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C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | There are, however, certain objections to these proposals. Unlike, for example, the Reynolds number, specific heat and enthalpy are dimensionless only so long as we bear in mind their relationship to water, for they rely for the invariance of their nominal numerical values on the retention of liquid water as the nomina... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | I cannot accept the objection by Mr. Laws to my temperature scale, as in using the MKS system any relationship to water is now irrelevant, because the kilogram mass is defined as a platinum-iridium cylinder deposited at the International Bureau of Weights and Measurements at Sèvres, France. The unit of energy is not ba... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | , had a series of thermometers manufactured using Joules per kilomole as a scale; and I am now using them in the laboratory and requiring students to become familiar with them. There was only a nominal surcharge for making these thermometers, and with wide adoption of the scale the price of the thermometers would be th... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 我认为接受这种温标比接受杰奥尔吉安教授的温标更加容易和令人满意,因为此温标不需要进行任何性质的重新计算并且更加适合于实际用户。
英文
劳斯
* * *
我感谢劳斯先生提供参考文献2和参考文献3。
英文
我知道参考文献2,并且除此之外,托尔曼[4]
对于讨论温度的量纲有很大的兴趣。只不过托尔曼希望用ML
2
/T
2
作为温度的单位,也就是说,允许将分子质量数(分子量)作为质量的量纲。然而,波特[5]
在他的《量纲的方法》一书中清晰地解释了温度的量纲实际上是L
2
/T
2
。
英文
我不能接受劳斯先生对我的温标理论所提出的异议,当使用MKS单位制时,任何物理量与水的关系此时都不相关,因为千克质量是通过采... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | ?”, I have been asked; would it not be more in keeping with the spirit of the occasion if I were to speak of the future of biology rather than of its past? It would indeed be, if only it were possible, but unfortunately it is not. What we want to know about the science of the future is the content and character of new ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | Haldane is very critical of the theories of memory propounded by Ewald Hering and Richard Semon, who “assume that memory in general is dependent on protoplasmic ‘engrams’, and that germ-cells are furnished with a system of engrams, functioning as guide-posts to all the normal stages of development”. (“Engrams”, I shoul... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | , working biologists tend nowadays to classify themselves less by “subjects” than by the analytical levels at which they work—a horizontal classification where the older was vertical. So we have molecular biologists, whose ambition is to interpret biological performances explicitly in terms of molecular structure; we h... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | and endocrinology). There is no compelling reason why he should be able to talk with relaxed fluency about messenger-RNA, and it is not essential that he should ever have heard of it—though an unreasonable feeling that he “ought” to know something about it is more likely to be found in a good ecologist than in an indif... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | environment, would be shared by the great majority of the members of the population, and would be stable except in so far as it might be modified by further evolution. The members of the population were predominantly uniform and homozygous in genetic makeup, and, to whatever degree they were so, would necessarily breed... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | equality. This pattern of genetic differentiation is determined and actively maintained by selective forces: it is the population as a whole that breeds true, not its individual members. We can no longer draw a distinction between an active process of evolution and a more or less stationary end-product: evolution is co... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | for evolution, of the forms in which genetic variants are proffered for selection. We have therefore no convincing account of evolutionary progress—of the otherwise inexplicable tendency of organisms to adopt ever more complicated solutions of the problems of remaining alive. This is a “molecular” problem, in the newer... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | in 1933; its resolving power was then one micron.
中文
Electron microscopy has shown that cells contain sheets, tubes, bags and, indeed, micro-organs—real anatomical structures in the sense that they have firm and definite shapes and look as if only their size prevented our picking them up and handling them. Moreover,... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | nothing to take its place. Peters's idea of the existence of a “cytoskeleton” to account for the orderly unfolding of cellular metabolism in time and place now seems wonderfully prescient, but there was precious little direct evidence for the existence of anything of the kind, and much that seemed incompatible with it.... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | It was not always so. In the 1930's experimental embryology had much the same appeal as molecular biology has today: students felt it to be the most rapidly advancing front of biological research. This was partly due to the work of Vogt, who had shown that the mobilization and deployment of cellular envelopes, tubes an... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | instructions rather than another. It is just possible to see how something of the kind happens in the induction of adaptive enzymes in bacteria—a phenomenon of which the older description, the “training” of bacteria, reminds us that it too, at one time, was thought to be “instructive” in nature. All this applies only t... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | theory. We had also learnt finally, and I hope for ever, the methodological lesson of behaviourism: that statements about what an animal feels or is conscious of, and what its motives are, belong to an altogether different class from statements about what it does and how it acts. I say the “methodological” lesson of be... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | was a certain natural connectedness between its various terms, as if they represented the playing out of a certain instinctual programme. Then, and only then, was it possible to start to obtain significant information from the study of contrived behaviour—from the application or withholding of stimuli—for it is not inf... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | complacency is to be deplored, so also is humility. Humility is not a state of mind conducive to the advancement of learning. No one formula will satisfy that purpose, for there is no one kind of scientist; but a certain mixture of confidence and restless dissatisfaction will be an ingredient of most formulae. Confiden... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 对于未来的科学,我们想知道的是新科学理论和新科学思想的内容和特征。但遗憾的是,十年后甚至十分钟后人们的新思想都是无法预知的,人们一旦试图去预测未来,就会让自己陷入自相矛盾的境地。因为预测一种思想也就等于接受了这种思想,如果我们接受了这种思想,它就不再是预测的产物。让我们试图将下面这句话补充完整:“我推测,下一届英国科学促进会会议上将有人提出基本粒子间相互关系的新理论,叫做
......”如果我现在将这句话补充完整的话,那么下次会议时这个理论就不是新理论,而如果我无法说出这是一个什么样的理论,那么我就没有完成这次预测。
英文
与推测将来可能或肯定会发生某事相比,大部分人在否定将来会发生某些事上更有把握。伪预言者们已经浪费了无数... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 我所说的“达尔文主义复兴”是指通过孟德尔遗传学的方式再现达尔文主义,如我们非常熟知的费希尔、霍尔丹、赖特、诺顿所做的工作以及一定程度上洛特卡和沃尔泰拉所做的工作。现在我们知道进化是发生在种群水平上的,而不是沿着世系或家系发生的:进化是一个种群在遗传结构上所发生的长期而系统的变化,其中自然选择起着至关重要的作用。但是,对于以王朝形式考虑进化的人来说,进化的结果是产生了一个新的基因型。新基因型的产生为种群在恶劣环境下的生存提供了一条解决途径,并且能够在种群内绝大多数个体之间共享,还能在未来的进化中保持稳定。一个种群内的绝大多数个体在遗传结构上大体是一致的或者是同源的,无论这种一致或同源性是何种程度,都能使种群的性状稳定地遗传。遗传多样性... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | )总而言之,细胞秩序是一种结构或晶体秩序,即一个“固体”秩序,而实际上,“这种所谓无定形固体既不是真的没有固定形状也不是纯粹的固体”[4]
。
英文
这个新概念是生物学史上的一次巨大变革,它标志着旧有的认为生命机体是胶质
的说法的消失,胶质学说是一个由古老的“原生质体”学说衍生而来的复杂概念。原生质学说认为原生质是一种易碎的胶状物,是一种生物醚渗透结构或者是无生命的结构,这早在30年代就已经过时,那时如果有人声称自己在研究“原生质”,那么他肯定会被嘲笑或被认为是疯子。然而我们对较高深的胶质学说仍然深信不疑,此理论认为细胞内存在异质性和液态晶体秩序。同时,我们也赞成霍普金斯于1913年在英国科学促进会会议上所发表的著名论断,... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 我们后来也了解了行为主义方法论,并且我希望能一直如此:它陈述的是动物的感受是什么或能意识到什么以及它的动机是什么,它与动物做了什么和怎样做的陈述属于完全不同的一类。我称它为行为主义“方法论”是因为,这个词代表着特定的心理学理论,即行为的现象学是行为的全部——以我看来,这个理论远不像它的名字一样听起来无聊。尽管行为主义方法学看起来过于严谨以至于产生了尚未丢弃,通过内省获得的特殊洞察力的教条,但是洛伦兹和丁伯根研究动物行为的方式近乎引领了一场思维上的革命,并使牛津、剑桥和遍布世界各地的多家学校纷纷建立起动物行为学学院,又有哪个学科能与之相提并论呢?
英文
我认为下面这个非常简单回复就是正确答案。在30年代,除了通过某种实验干预(即... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | shall start from the observed shift of the spectrum lines of galaxies interpreted in terms of the expansion of the universe. The red shift implies that distances between galaxies, measured with an imaginary ruler for example, increase with time. An immediate question is whether the universe was denser in the past than ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | was more dense in the past than it is today. However, further knowledge is needed concerning the nature of the radio sources before this conclusion can be regarded as definitive.
中文
If the quasi-stellar objects are truly cosmological a great deal becomes pretty well settled. Imagine an object of fixed intrinsic brig... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | At present, red-shift measurements are available for about fifteen quasi-stellar objects. The shifts are dimensionless numbers given by dividing the wave-length shift of any spectrum line by the laboratory wave-length of the same line. The result is the same for all lines. The measured values range from quite small val... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | These remarks are all subject to a cosmological interpretation of the red-shift of the spectrum lines of the quasi-stellar objects. If much smaller, fainter objects were fired out of our own galaxy, or out of some neighbouring galaxy, with speeds close to light the same red-shifts would be observed. Can we be sure that... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 14-121, two regions of radio emission on opposite sides of, and collinear with, a centre of optical emission. The possibility must be considered that a cascade process is involved. An initial object in the centre of a galaxy breaks violently into two pieces. Later, each of these pieces breaks into two further pieces; a... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | The same difficulty does not arise in the case of the galaxy NGC
5128. This is a nearby massive elliptical, distant about four million parsec. At least one major outburst is known to have occurred in the nucleus of this galaxy within the past ten million years. The probability must also be considered that both NGC
51... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | fluctuations can be tolerated. If we are already near the end of the road, the theory will survive and will then probably turn out the correct theory. But if we are still near the beginning of the road, the prospects for the theory will be slight. I would say we have to do with a fifty-fifty situation.
中文
I would li... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | A similar result follows from the entirely different consideration of the helium-to-hydrogen ratio in stars and gaseous nebulae within our galaxy. Determinations of this ratio range from 0.08 to 0.18; and the ratio seems to be just as high in old stars as in most young stars. The ratio to be expected from current stell... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | consideration of this problem points decisively toward the universe having been very much denser in the past than it is at present.
中文
Galaxies have been broadly classified into two types—ellipticals and spirals. There is an incontrovertible argument to show that spirals must have condensed from a more diffuse form.... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | . The critical point now emerges, that the surface brightness of the resulting aggregation can be calculated (assuming the material forms into stars) and the calculations yield quite unambiguously a law close to the inverse square, in fact just what is observed.
中文
The point I wish to make is that whereas the steep ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | believed the answer to this question was also affirmative, but my belief was based more on the failure of those who maintained the opposite to demonstrate their case than on any positive demonstration on the affirmative side. However, progress on the affirmative side has been made very recently, and opinion has general... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | During the past ten years the struggle has been to invent a form of mathematics operating in the manner customary in physics, namely, starting from an action principle. It was found possible to represent the creation of matter through the introduction of a new field. The manner in which the field was treated was quite ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | So far as I am aware, such an oscillating model is in satisfactory agreement with all available data. The model is less dull than it seems at first sight, for it contains the possibility of some carry-through from one cycle to the next. Suppose the universe as we observe it eventually stops expanding. Suppose it falls ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | During the past year, Dr. Narlikar and I managed to investigate a possibility which had previously proved too difficult to handle, the case in which there are departures from homogeneity, the case in which there are fluctuations from one region of space to another. To our surprise we found that under certain conditions... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | (3) The observed values are of non-local origin.
中文
I imagine few will be satisfied with the first of these possibilities. I also imagine most physicists prefer (2). But what if (3) should be correct? Could the curious values we observe for the dimensionless numbers be connected with the particular oscillating and f... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 这是由于即便是最亮的星系也无法在理论差异稍稍明显的距离上被观测到。在更遥远的距离尺度上,不同理论的差异将变得明显起来。然而,技术上的困难是当光强度非常小时,不能获得照相光谱谱线数据。需要的是更亮的天体。类星射电源正是在此刻成了具有关键重要性的观测对象。在接受这些类星体光谱谱线的红移具备宇宙学特性之后,可以发现类星射电源的光度比最大星系还要高约4个星等,即大约亮40倍。
英文
迄今为止,人们已经得到了大约15个类星体的红移数据。在这里我们定义红移为任意谱线的波长移动除以实验室中该谱线的波长,是无量纲的量。其结果对所有谱线均是相同的。测量得到的谱线红移量范围从十分小的值如类星体3C
273的0.16到非常大的值如3C
9的2。... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 当然,我们也必须考虑这种可能性,即观察到的类星体是银河系与这个星系NGC
5128共同产生的:银河系产生相对低速的天体,而NGC
5128产生速度较大的天体。
英文
上面谈到的这些问题毫无疑问可以通过观测解决。随着快速积累的观测资料,观测正导致我们对类星体尺度的估算。观测发现,来自3C
273的光大约以10年为特征时标在变化。这说明该光学天体的最大半径为10光年。不仅如此,3C
273的辐射中也发现了存在持续时间仅为数周的光闪。主要是因为最大半径会缩小为1/10光年或是更少,现在有一种倾向不相信3C
273提供的证据。因为按宇宙学假设,怎么可能存在直径只有1/10光年的天体,却能够释放出比最亮的星系都还要亮100倍的... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 英文
椭圆星系是显著的无定形的,恒星在其中的分布是处处平滑的。如果测量椭圆星系的表面亮度,会发现某一点的面亮度和其距中心的距离非常接近平方反比定律。在接近中心点处面亮度上升十分陡。中心有一个极亮的中心核,但由于大气视宁度效应,将中心点涂抹成看起来成盘状,这让我们现在无法定出其中心有多锐,多像恒星。
英文
假设宇宙是从一个密度高得多,比如,10–12
克/厘米3
的状态膨胀演化而来,并假定刚开始膨胀的气体并非完全平滑的,其中已经存在一些气体凝聚形成的团块,而这些凝聚团块能够在一定程度上使保持住的气体质量将能够被准确地计算。例如,一个大约有十亿个太阳质量的团块将能够使得大约一万亿个太阳质量的气体被束缚在星系大小的范围内。一个... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 这个模型并不像乍看起来那样死板,因为其中包含着从一个循环转入下一个循环的可能性。如果我们现在的这个宇宙最终停止膨胀了,并且返回相对高的密度状态,在这种状态中,恒星将会蒸发,甚至重元素原子核也将瓦解,物质将形成,而氦和氢的比例也如我在上面提到的约为0.14。在高密度状态,物质分布并非是十分均匀的。因为存在着星系或星系团,所以将不可避免地偏离均匀分布。而这样的不均匀将形成凝聚的团块,新一代的星系将会围绕它们形成。这样,我前面提到的凝聚的团块将不仅仅是来源于随机的扰动。上一代的星系将会成为下一代星系的种子。磁场也将在一次次循环中保存下来。
英文
对于该模型,现在有两方面的反对意见。首先是这个模型中新引入的场是无源的。该场是我们为了此... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | point out that its geographical extent could enable reconstruction of fluctuations in ice-age climate—a technique now central to understanding the mechanisms and speed by which climate has switched in the past between glacial and warm conditions.
中文
S
INCE Bramlette and Bradley1
first described glacial marine sedi... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | . can also be defined using the relative abundance of ice-rafted detritus present in the cores.
中文
The amount of ice-rafted detritus present in the sand fraction of 13 cores taken from the North Atlantic (Fig. 1) previously described by Ericson et al.
7
was estimated at intervals down the cores (Fig. 2) by examinat... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | In general, the sand fraction consists mainly of tests of pelagic Foraminifera mixed with ice-rafted sand and minor amounts of volcanic ash. The ice-rafted detritus is easily identifiable, as it characteristically consists of very poorly sorted, and mainly angular, sand and pebbles of a variety of mineral and rock type... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 9-3. The variation in the percentage of ice-rafted detritus in the sand fraction at intervals down the cores (Fig. 2) can be interpreted as a measure of the effects of climate on deposition. Zones containing a relatively high percentage of ice-rafted detritus correlate very closely with zones containing colder-water fo... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | These results indicate that the abundance and distribution of ice-rafted detritus in deep-sea cores in the North Atlantic could provide a powerful tool for delineating even minor fluctuations in the Pleistocene climate. Cores taken in pelagic sediment in the vicinity of cores R
5-36, R
10-10 and A
180-13 in particul... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | Heezen, B. C., Geol. Soc. Amer. Spec. Paper
, 65
, 99 (1959).
Pratt, R. M., Deep-Sea Res.
, 8
, 152 (1961).
Ericson, D. B., Ewing, M., Wollin, G., and Heezen, B. C., Geol. Soc. Amer.,
72
, 193 (1961).
Ericson, D. B., Ewing, M., and Wollin, G., Science
, 144
, 1183 (1964).
Krinsley, D. H., and Newman, W. S., Scie... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 粒度大于1毫米的部分主要由花岗岩、片麻岩、区域变质岩和各类沉积岩组成。
英文
在北大西洋东部的岩芯中,冰筏砂与黑色浮石以及褐色和黑色的玻璃共生。由于黑色火山碎屑的含量与分选较差的冰筏砂的含量具有稳定的关系,所以这类碎屑也应属于冰筏成因的漂砾。正如此前埃里克森等人[8]
曾注意到的一样,冰岛附近岩芯中的黑色浮石和玻璃最为丰富(图1),而黑色浮石的含量向南逐渐降低。这些现象表明来自东格陵兰岛和不列颠群岛的碎屑物稀释了来自冰岛的火山碎屑物。在北大西洋西部,石英含量较小,仅占冰筏砂的30%~50%。岩芯A
157-5和A
157-6中冰筏砂的典型特征是含有大量的角闪石和石榴石。
英文
冰筏砂的含量从南至北逐渐增加,在最南端... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | the magic number 50 arises as 8 neutrons or protons in a closed-shell core, and another 42 in an outer halo. These magic-number nuclei have a higher average binding energy than other nuclei.
中文
I
N 1933 Elsasser1
pointed out that some of the properties of atomic nuclei correspond to greater stability for certain n... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | of energy-levels) are 2, 6, 8, 14, 16, 20, 28, 32, 38, 40, 50, 56, 64, 68, 70, 82, 92, 100, 106, 110, 112, 126, 136, 142,....
中文
In the course of developing a theory of nuclear structure based on the assumption of closest packing of clusters of nucleons5
, I have found that the magic numbers have a very simple stru... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | . For example, the 3s
1/2, 2d
3/2, and 1h
11/2 sub-sub-shells all begin to be occupied at about N
or Z
= 60 and are all completed at about N
or Z
= 82.
中文
The configurations found in this way for the magic numbers are given in Table 1 and Fig. 1. Each of the first two represents a completed shell. The third (... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 例如,他们[4]
将N
或Z
为50的组态标记为(1s
1/2)2
(1p
3/2)4
(1p
1/2)2
(1d
5/2)6
(2s
1/2)2
(1d
3/2)4
(1f
7/2)8
(2p
3/2)4
(1f
5/2)6
(2p
1/2)2
(1g
9/2)10
,或更简略地写成1s
2
1p
6
1d
10
2s
2
2p
6
1f
14
(1g
9/2)10
。
英文
有关自旋–轨道耦合和梅耶夫人–延森壳层模型的证据是令人信服的。然而,对于他们的论据,让人难以理解的是,为什么这6个幻数在可以填满自旋–轨道耦合的支壳层的数字集合中是如此与众不同,这个集合... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | The context of the International Biological Programme which ran during the 1960s and 1970s, as explained here by its scientific director E. Barton Worthington, looks astonishingly prescient from today's perspective. The programme was essentially concerned with environmental biology and conservation, but it adopted the ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | sciences. Research on the ionosphere, the atmosphere, and the geosphere has been greatly stimulated by organized activities—the International Polar Years, the International Geophysical Year and the International Years of the Quiet Sun which have developed one from the other. Programmes are going forward strongly, too, ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | Some biologists are inclined to think that the International Biological Programme is rather a waste of effort and money. They argue that opportunities for the exchange of knowledge and ideas are not lacking, but are almost overburdening, for international unions and associations exist in every branch of biology. From s... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | secretariat of the Royal Society, by priming and holding the feeding-bottle, have enormously helped the infant's early growth.
中文
How the ideas leading up to the International Biological Programme have fluctuated and developed has been related by Prof. Montalenti, the Italian geneticist who led much of the preparato... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | will explain.
中文
Principles
The programme is based on a number of principles. First, it is a directional and a selected programme. It is not a free-for-all, nor is all research bearing on productivity and human adaptability automatically incorporated into it. The initials IBP can be regarded, if you like, as a kind ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | conservation rather than preservation; but the perpetuation of sample biological systems for future biologists to study is definitely among its objectives.
中文
Fourthly, and this could perhaps almost go without saying, the International Biological Programme is limited to research which could benefit from internationa... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | different facets of the processes of production—photosynthesis (utilization of solar energy) and the nitrogen cycle—this section is called Production Processes (PP). Each of the three may reveal new resources of value to mankind or new methods applicable to the use and conservation of resources, which require fundament... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | IBP work in the warmer regions overseas, in co-operation, of course, with the countries concerned. One of these is likely to be in savannah country, at the Cambridge Nuffield Unit of Tropical Animal Ecology, situated in the Queen Elizabeth Park in Uganda; another at a site yet to be determined in an area of tropical ra... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | and oasis conditions. This indeed will make a useful counterpart to the proposed IBP bases in savannah and rain forest to which I have already referred.
中文
From the PF section I will draw two examples of British initiative: one is an intensive study of the biological productivity of a reach of the Thames, organized ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | into meat than the latter; if only kangaroos produced wool instead of hair, they might be the basis of Australian prosperity. In Africa there are indications that the broad spectrum of indigenous African mammals, such as giraffe, antelopes, buffalo and wart hog, may be better agents of secondary production of meat than... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | completed, their study will take quite a significant place in the programme. Here again, it is good to note that Britain has taken an initiative, and as I speak a group of eight scientists drawn from Liverpool and other universities in Britain and Nigeria, and supported financially by the Ministry of Overseas Developme... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | their natural environments. This involves mounting a good many quite complex expeditions to remote places. British workers under IBP/HA expect, for example, to work this autumn on the Hazda tribe around Lake Eyassi in Tanzania and the people of Bhutan in the very high Himalayas.
中文
Organization
There is a school of ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | Britain, and a number of other members, some representing the main international unions in the biological sciences and some drawn from the different bio-geographical regions of the world. It includes also the seven international conveners of the sections of IBP. Unesco, FAO, WHO, SCOR, and SCAR have representatives on ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | a model, and if some twenty major nations have comparable programmes and twenty or thirty others prepare smaller programmes, the total is bound to run to several million pounds. The finance for national programmes will of course be provided nationally: in this first year of design and feasibility studies, the British T... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | The gestation period of the Programme has been long, but recent progress is at a much greater rate than we had dared to hope a couple of years ago, for the world needs an IBP. What, then, is the philosophy behind it? What is the driving force that causes many busy people about the world to devote their time and energy ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | , 223-226; 1965)
Dr. E. B. Worthington: Scientific Director (Designate).
*
Substance of an Evening Discourse delivered on September 3 at the meeting in Cambridge of the British Association for the Advancement of Science.
国际生物学计划
*
沃辛顿
编者按
站在今天的角度看,国际生物学计划是一个非常具有前瞻性的计划,本文中该计划的科学主任巴顿·沃辛顿指出它是在20世纪六七十年代期间实施的。虽然该计划的重点... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 英文
蒙塔伦蒂教授讲述了这些想法是如何促成国际生物学计划在曲折中发展的,这个意大利遗传学家为这项计划做了大量的筹备工作。首先,有人认为这个计划应该关注人体组织,特别是种群动力学和遗传学。之后,大量的主张认为该计划应致力于保存和保护世界不同地区的生物系统,特别是那些因为经济发展而濒临灭绝的生物系统。最后,这些观点和其他想法以这样一种方式整合起来以引起众多生物学家的注意。1964年确定出其目标旨在保证世界范围内的以下研究:(a
)陆地上、淡水中以及海水中的有机质生产,新能源以及现有自然资源的潜力和使用;(b
)人类对环境变化的适应性。这项计划并没有囊括生物学的所有领域,而是仅限于与人类生产和人类福利相关的基础生物学研究,这些项目将... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 当然,这七个部分不仅彼此之间紧密联系,并且与同一时期进行的其他计划也是紧密联系的,例如淡水生物群落生产力部分和国际水文十年计划之间存在联系。
英文
国际生物学计划由它的各个部分共同组成,其意义不仅仅在于包含七个不同的部分,而且在于大部分研究的开展和资助都是在国家层面而非国际层面上进行的。目前许多国家正忙着准备他们自己的国家级项目,其中一个最先进的项目是英国的,目前由皇家学会公布。
英文
研究例子
让我们来举些例子来说明国际生物学计划所要从事的这种工作,尤其是要看看英国所作的贡献。虽然我们对国内生物群落和人群了解的还不多,但一些流行的想法是我们应当利用海外优秀科学家的知识和能力,那里对生物生产力仍然知之甚少。因而英国陆地生... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 而这些贮存的大量的水不仅用于发电和灌溉,而且能满足人类的许多其他需求,并且也对较大区域里的生物产生了深远的影响。例如,熟悉非洲的任何人都能认识到大型自然湖泊对天气、植被、渔业和人类用水以及水资源的贮存、运输、城市发展的地理位置和其他方面造成的重要影响。国际生物学计划执行的时期碰巧与在建的几座新的大型水库及已完工的几座水库引起的生物变化所处的时期相同,对它们的研究将在这项计划中占据重要地位。在这里,我们再次表扬英国采取的主动行动,在我演讲的这一刻,由8名分别来自利物浦以及英国和尼日利亚的其他一些大学的科学家组成的团队正承担着对尼日尔河部分河段的初步研究工作,该项目由海外发展部给予资金支持。1806年芒戈·帕克曾来过这些河段,这些河段将... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 迄今为止,还不能估算出到底要花费多少钱,因为很少的国家项目已经有了详细的计划,尽管有一些正在积极地准备着。如果我们以英国的计划为例,若二十个左右的主要国家能有类似的计划并且还有二三十个其他准备好的小计划,那么执行这些计划所需的总费用一定会达到几百万英镑。当然,国家计划的经费将由该国提供:在制订计划和可行性研究的第一年,英国财政部专门为国际生物学计划拨款了80,000英镑;为英国皇家学会和大自然保护协会增加合法投票权。这有益于进行委任并开始开展一些野外实验研究。很多其他国家也有些许类似的做法。例如,捷克斯洛伐克除了支付规划阶段的资金外,还为其中一个国际召集人(在布拉格基地的马利克教授)提供办公室日常运转和员工费用。
英文
为了制... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | n previous experiments at Jodrell Bank the angular sizes of discrete radio sources have been investigated by means of long baseline interferometers1,2
. The highest resolving power used previously was obtained during observations at a wave-length λ=0.73 m with telescopes 180,000 wave-lengths apart (134 km). Four quasi... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 21 and 102) all gave clear fringe patterns over a wide range of hour angles, though for only one source did the amplitude remain approximately constant. These sources are listed in column 1 of Table 1. Column 2 shows their catalogued8
flux density, S
, at λ=0.21 m. The observed fringe amplitudes were normalized by da... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 102 did not appear to be resolved at any hour angle when its elevation was greater than 15°, so that its angular size is shown to be less than 0.1 sec of arc in all position angles. Each of the other sources was partially resolved at some hour angle, and the corresponding maximum angular dimensions (assuming gaussian s... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | , from the ratio given by the occultation observations of 1962.9. The total flux from this source was therefore re-measured recently, with the Mark I telescope at Jodrell Bank, and compared with the radio galaxies 3C
348 and 353. These measurements show that, on the assumption that the radio galaxies have remained con... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | * These linear dimensions have been calculated for model universes (ref. 4) in which the acceleration parameter q0
=+1. If q0
=0, these values must be multiplied by a factor (1+0.5z
) which for these sources lies in the range 1-2.01.
† Results (ref. 7) of detailed analysis of observations at λ=0.73 m.
‡ None of the ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | , 207
, 1024 (1965).
类星体角大小的新极限
阿吉等
编者按
类星体最早是作为离我们星系非常遥远的强大射电源而为人所知的。在20世纪60年代中期,射电天文学家们开始积极着手对这些神秘天体的信息进行收集汇总。本文叙述了两架相隔了134千米射电望远镜的观测应用(一架在英国北部曼彻斯特大学的焦德雷尔班克,另一架在莫尔文以南的雷达研究实验室),这使人们能够通过干涉测量技术推断类星体的大小。
英文
在焦德雷尔班克之前的实验中,人们曾用长基线干涉仪对分立射电源的角大小作了研究[1,2]
。从前进行的最高分辨率的观测是在波长λ = 0.73米处,用相隔180,000倍波长(即134千米)距离的望远镜观测到的。在这... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 因此,最近用焦德雷尔班克的马克I望远镜重新测量了这个源的总流量,并与射电星系3C
348和353作了比较。这些观测表明,如果假定射电星系保持稳定,那么在1965.6射电星系3C
273的总辐射流量约为46±1.5个流量单位。如果假设干涉仪的观测结果是参照子源B
的,而且这个子源的流量在3年里大致增加了30%,即现在增至30个流量单位,那么这是与其他结果相一致的。但并不清楚子源B
中哪个区的辐射流量在增加。这个结论可与登特[3]
给出的测量结果相比较,登特指出在8,000兆周/秒时,几乎所有的辐射均来自子源B
,而其对应的流量在2.5年里增大了40%。
英文
表2.3C
273在0.21米处的数据
A
部分仍为... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | = 60. The cytological, morphological and biochemical studies of M.
271 reported here provide good evidence that it is a true hybrid and therefore the product of double chromosome reduction.
中文
The plants used in this investigation were as follows: Parents. Solanum demissum
(C.P.C. 2249) (dms
2249). This clone, co... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 271 has no stainable pollen and attempts to backcross it by both parents as males gave one berry when sto
2282.2 was used. This contained two seeds, but neither germinated.
中文
Possible Origins
There is no definite morphological evidence to suggest, let alone prove, that M.
271 is a true hybrid of S. demissum
× S.... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 271 could have conceivably arisen by male parthenogenesis, in which case it would be genetically equivalent to a segregate in a progeny raised by selfing sto
2282.2. Such a progeny was grown and all the individuals were found to resemble closely the parent plant; furthermore, all were fertile and set berries by selfpo... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | is the predominant parent.
中文
(2) The pattern of M.
271 does not disagree with the idea that stoloniferum
is the other parent. One constituent of stoloniferum
, it is true, is not present in the hybrid. This substance, luteolin 7-glucoside, though characteristic of the species, is not always present: it was lacki... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 271 contained three glycosides of which two corresponded in R
F
value with glycosides from the different parents, that is with demissine and α-chaconine; the third appeared to be a new demissidine glycoside. On acid hydrolysis, these glycosides together yielded demissidine, with traces of solanidine, and four sugars: ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 2282.2 (Table 1). However, pollen grain measurements from ten different anthers showed a range of size within each anther. Using within-anther variance as a measure of this variation, Bartlett's test showed a highly significant heterogeneity between anthers (χ2
[9]487.4). Furthermore, the mean variance within anthers ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | thought that the chromosome number of the parents disproved the supposed origin of these cultivars but, in retrospect, it now seems that the original interpretation is worth reconsideration.
中文
In none of these examples is there definite proof of double chromosome reduction: for the potato hybrid, although direct cy... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 英文
杂种M.
271
这是由dms
2249(♀)×sto
2282.2(♂)杂交得到的种子,该种子萌发后逐渐长为节间极短的簇生盘状的矫小植株,仅生长出一朵花。相比之下,若将其嫁接在番茄上,则生长直立且旺盛,节间长,花多且持续产生。对M.
271与其亲本的叶片和花器官性状进行比较(表1)表明,它在许多方面更接近亲本demissum
而不是sto
2282.2。五倍体杂种(2n
=60)应该也更偏向于demissum
,因为其基因组组成为3 dms
+2 sto
。如果不考虑染色体数量,M.
271应该在形态上更像多元单倍体S. demissum
(2n
= 3x
= 36)[1-3]
。表2是减数... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 缩写:dms—demissum
; sto—stoloniferum
; chm—chomatophyllum
; san—santollalae
; ver—verrucosum.
英文
(1)杂种M.
271的酚型与demissum
的相同,这与形态学证据是吻合的(见上文),表明demissum
是其主要亲本。
英文
(2)杂种M.
271的酚型并不能否定stoloniferum
是其另外一个亲本。的确,在杂种中没有检测到stoloniferum
的一种成分,但也有研究表明虽然木樨草素7–葡糖苷是该物种的特征性物质,但并非总能被检测到:在所有检测过的38个克隆体中,4个克隆体中未检测到木樨草素7... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 这种机制非常有可能是产生发生染色体双减数的花粉粒的原因。遗憾的是,由于病毒感染使克隆体丢失,未能对sto
2282.2的减数分裂进行再次研究。因此,尚缺乏双减数假说的细胞学证据。
英文
讨论
双减数常被用来解释许多异常杂种的产生。例如,斯蒂尔[15]
通过将腋花矮牵牛(2n
= 2x
= 14)和碧冬茄(2n
= 4x
= 28)杂交,获得了与其两亲本均相似的二倍体后代。西山[16]
在燕麦属杂种研究中,卡尔佩琴科[17]
在芸薹属植物和萝卜属植物杂交实验中,尤尔特和沃克[18]
在对一品红的研究中都观察到了类似的现象。在对樱桃的研究中,研究者认为3个二倍体樱桃栽培品种是由二倍体物种欧洲甜樱桃和四倍体栽培品种... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | ) the lower limit on the angular diameter of the source derived from the absence of self-absorption down to some particular frequency4,5
(assuming the synchrotron mechanism and that the electrons are radiating incoherently); (c
) the distance derived from the red shift of the optical counterpart of the radio source. ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | Model I.
This model consists of a source of angular diameter 0.5 sec and (roughly constant) flux density ~25 flux units down to at least 200 Mc/s, in the centre of which is a varying source of angular diameter 1.3×10–3
sec (corresponding to a linear diameter of 3 pc), and at minimum a flux density ~2.5 flux units dow... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | have the values ~4,000 and ~10,000 Mc/s respectively, and the expected variations at 8,000 Mc/s are large enough to account for the observations. Our estimates for v
a
and v
b
are only rough, but they indicate what might be expected, and the measurement of their values and of the variations at intermediate frequencie... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | (v) could come, if it in fact comes from a region which is opaque at all frequencies up to v.
We find that R
(v) ~0.3 (S
(v))1/2
(v/104
)1.25
parsecs, when S
is measured in flux units and v in Mc/s. This radius can be compared with the distance r
(v) which an electron radiating at frequencies ~v would travel in... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | ) from ~0.6 to ~1.9 pc, could therefore certainly occur rapidly enough to explain Dent's observations. We can also predict, on the basis of this model, that more rapid variations could occur at higher frequencies. Furthermore, if a sudden change in the rate of injection of particles produces changes in S
(v) at differ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | 105
Mc/s) to the value of H.
to the precise position where the electrons are accelerated. And to their mean rate of outward drift. It would therefore clearly not be worth while to base an exact calculation on this crude model.
中文
The foregoing rough arguments do, however, suggest that at least a part of the visibl... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | . It will not be possible to find out whether the central part of the source is polarized at radio frequencies until the extent to which the degree of polarization changes when the flux varies has been examined. However, even if the radio flux from the core were polarized (implying large-scale uniformity in the directi... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | If the gas were in the form of a uniform spherical cloud, its diameter would be ~0.5 pc, and it would be opaque to light of all frequencies because of scattering by free electrons. It would therefore be difficult to account for the observed fluctuations in optical luminosity with a time-scale of a few months, since if ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | ergs/sec, mainly at visible wave-lengths. Its thermal energy content is insufficient to maintain this rate of energy loss for more than a few weeks, and so it must be absorbing energy at an equal rate from the interior. Since the shell absorbs radio waves, intense but unobserved radio radiation may exist in the spheric... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | Mc/s (apart from the component which comes from the halo) is, according to this model, emitted outside the shell by electrons which have escaped from the interior. An electron ejected from the massive object at the centre will be absorbing and emitting radiation at the same rate until it approaches the shell. Since the... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0306. 《自然》百年科学经典(英汉对照版)(第四卷)(1946-1965).epub | .epub | 35,511,682 | 2025-09-26T19:07:57.651603 | /γ sec. The highest energy electrons the synchrotron losses of which are balanced by self-absorption have γ ~250, and their Compton lifetimes are of the same order as the time they would take to travel outwards from the centre to the shell. The Compton losses, therefore, are significant, though their exact magnitude is... | 400套付费套装书 |
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