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C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | can be read from the graph given in our previous letter with an error of less than 20 percent (due to the uncertainties of inter- and extrapolation; in order to facilitate the latter, we added to the curves a further experimental point for r
= 29 cm.). The value of Atot
for the ammonium solution can be easily calcul... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | = 3.2, we find:
ν = 3.5 ± 0.7.
中文
We were not able to allow for an error in Af
, since the value of σf
given by Anderson et al
. contains no indication of probable error. Any error in σ
f
will affect ν – 1 in an inversely proportional way; in any case ν will remain greater than 1.
中文
The interest of the phen... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 假设溶液中只有依照1/υ
定律吸收中子的原子核(这个法则的唯一例外将在不久后处理),τ
正比于1/Σci
σi
,其中ci
是吸收中子的原子核浓度(克原子每升),σi
是所有速度为1的中子的俘获截面,指标i
遍历溶液中原子核所致的各种中子吸收反应。用Ai
代替ci
σi
,用Atot
代替ΣAi
,我们将得到:
上式忽略了所有包含诸如(ΔQ
)2
、ΔQ
·ΔAtot
等的高阶项。
英文
符号Δ代表我们在以前实验所使用的两种溶液(硝酸双氧铀和硝酸铵)中观察到的差值[1]
。在Atot
引入使Atot
定义不明确的因素之前,ΔAtot
可以忽略不计,这(硝酸双氧铀对... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 英文
(王静 翻译;夏海鸿 审稿)
Use of Isotopes in Biology
Editor's Note
Here Nature
reports on developments in the application of radioactive elements and heavy non-radioactive isotopes as tracers in biology and medicine. The possibility of identifying single-atom decays made such methods very sensitive. At a recent meeting of... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | For use, a small amount of the labelled sodium phosphate is added to ordinary sodium phosphate solution, and by this means the path of the phosphorus in the body can be traced. Estimations are carried out by observing the decay, at a given time, using a Geiger counter, and comparing directly with the decay of a similar... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | It may be objected that the use of isotopes as indicators in the living body may disturb the normal conditions. Actually, the proportion of radioactive phosphorus which it is necessary to use is extremely small, and the radiation from it may be comparable with that from the potassium which is already present in the bod... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | nearly removed, there will be a slow exchange of labelled phosphate back from the bones to the blood. Thus it may be possible to detect labelled phosphate several weeks after administration. Examination of the separate organs of the body enables the passage of the phosphate to be followed, and similarly examination of ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | The use of radioactive sodium phosphate have also been of great help in a study of the formation of (goat) milk. Samples of blood and milk taken at intervals after administration of labelled phosphate were examined for the activity of the phosphate in the blood and the various phosphorus compounds in the milk. It was f... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | carried out using heavy nitrogen as indicator.
中文
The use of deuterium as an indicator was discussed by Prof H. S. Raper and Dr. W. E. van Heyningen. The former referred to the work of Cavanagh and Raper, in which fats labelled with deuterium were fed to animals and a study made of the rate of formation of the deute... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 《自然》的这篇文章报道了在生物学和医学领域应用放射性元素和非放射性元素的重同位素作为示踪剂的进展。对单原子衰变的识别能力使该类方法具有很高的灵敏性。在最近召开的化学学会与生理学学会上,研究者们描述了在追踪人体内骨骼对磷的吸收时放射性磷的应用。类似的研究还有探测器官的化学放射性,评估蛋白质形成的时间。还有一些实验是利用诸如重氧或放射性钠等作为示踪剂研究人体生理及植物生理。与机体内自然产生的放射性相比,实验引入的放射性是较小的,因此这些实验基本上是安全的。
英文
人工放射性同位素和非放射性元素的重同位素的发现,以及后者的浓缩方法的出现,为检测体内物质的反应和运动开辟了新途径。
英文
在生物学研究中最常使用的同位素示踪剂是放射... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 英文
放射性磷酸钠的使用也为研究(山羊)奶的形成提供了很大的帮助。在注射同位素标记的磷酸盐后,间隔性采集血液和奶液样品,检测血液中磷酸盐的放射性以及奶液中的各种含磷化合物。3到4小时之后,发现奶液中的无机磷酸盐被血浆中的放射性磷酸盐取代;然而如果在注射放射性磷酸盐的同时注射重水,那么1小时后由血液和奶液制得的水溶液样品就具有相同的放射强度,速率方面的差异可归结为水分子扩散通过膜的速率比磷酸根离子更快这一事实。根据酪蛋白变得具有放射性的速率,对比奶液中的放射性无机磷,可以估算出腺细胞中酪蛋白的形成时间大约为一小时。
英文
在加入同位素标记的磷酸盐几个小时后,与无机磷酸盐相比,奶液中的磷脂仅具有轻微的放射性,这一事实意味着后者不... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | on the “transfer” of liquid helium II by a surface film above the liquid level, we stressed the similarity of this “transfer” with the so-called transport phenomena in the free liquid, and suggested that the latter might be due to a process similar to the transfer above the liquid level. Later experiments on the format... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | . However, in the present case the transfer of liquid must be carried out through the surface film above the liquid level, which shows that there exists a flow of helium against a temperature gradient, even if the two containers are not connected by free liquid. One may conclude therefore that the “fountain phenomenon”... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | for a flow of liquid helium II through capillaries. It seems to us, however, that the anomalous phenomena of liquid helium II are not so much caused by capillary flow as by a transport along solid surfaces; and these results seem to indicate that the heat content of those atoms transported by surface flow must be lower... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 这清楚地表明,当存在温度差的时候,氦会从温度较低的地方“迁移”到温度较高的地方。然而,当进一步加热时,瓶内的蒸发就成为主导因素,因此,杜瓦瓶内的液面会下降到低于池中的液面高度。
英文
图1
英文
这一效应与艾伦和琼斯[3]
在体相液体中发现的“喷泉现象”极为相似。然而,在我们的实验中,液体迁移必须通过液面上的表面膜才能实现,这说明:即使两个容器之间没有自由液体相连通,也会存在与温度梯度方向相反的液氦流。有人也许因此得出结论:瓶内液体中的“喷泉现象”可能也是由于表面迁移而产生的,尽管在这种情况下迁移处于液面之下。下面的事实则进一步证实了这一假设:当用装有细粉的管子连接两个容器中的液体时,产生的“喷泉现象”比用直毛细管时... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | of March 18, p. 455, has aroused great interest. This has partly found expression in numerous requests from all parts of the world for the earliest possible publication of a detailed description. I am able to pursue my investigations only in very limited spare time. The preparation of an adequately illustrated detailed... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | plates are attached to the scales by tissue which is softened by alkali. The tubercles are of simple structure with a central cavity (see Fig. 1). The lateral line tubes are posteriorly widely bifurcate.
中文
Fig. 1. Section of a scale (×50) of Latimeria chalumnoe
J. L. B. Smith.
中文
Fins.
All the rays of the fir... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | There are eight bones in the “parafrontal” series, the anterior expanded bones having been named “antorbitals” in fossils. Besides these nineteen there are the small dentigerous rostral plates. Most of these bones are small and laminate.
中文
Sensory canals
. The main canals run much as have been shown in reconstruct... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | anterior to the median nasal cavity, lies a sac, typically covered below, laterally, and partly behind, by the prevomer, in front by bone No. 18. That bone lies against the outer surface of the hind column of the prevomer. These sacs correspond with the usual “olfactory capsules”, but do not appear to have any external... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | There is a series of small “labial” dentate plates on the outer surface of the dentary. Superiorly are four dentate plates on each dentary. The anterior coronoid is small and bears granular teeth as well as several large tusks. The posterior coronoid is large and feebly granulate at the base. The articular-prearticular... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 因此,下文将仅对保留完整的组织结构进行如实的描述。
英文
鱼鳔。
依照标本剥制师提供的较为确切的证据,这个器官至多只是轻微骨化。
英文
鱼鳞
为圆鳞,但轻微骨化。对身体中部无修饰部分的鱼鳞进行灼烧处理,其剩余物远远少于对硬骨鱼类鱼鳞进行类似处理后得到的剩余物,但性质是相同的。每片鱼鳞外露的表面积占总面积的1/4到1/6不等。尾部鱼鳞上的装饰为皮刺形式,而在身体的其他部分是结节形式。结节仅在表面存在;每一个结节位于一个有波纹的薄的椭圆形基板上。基板通过已被碱软化过的组织固定在鱼鳞表面。结节是带有中央空腔的简单结构(见图1)。侧线管后端分叉较宽。
英文
图1.拉蒂迈鱼(史密斯)的鳞片截面图(放大50倍)。
英... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 海岸区的其他6个小博物馆条件非常艰苦,一般只有一个主管或馆员,他们不可能精通博物学所有的分支学科。他们中的任何人对海中比腔棘鱼更加陌生或至少一样陌生的鱼早已见怪不怪。正是拉蒂迈小姐的能力和决心挽回了很多损失,科学工作者有足够的理由对其表示感谢。我以拉蒂迈命名这个属就是为了表达对她的感谢。
英文
(田晓阳 翻译;陈平富 审稿)
Control of the Chain Reaction Involved in Fission of the Uranium Nucleus
F. Adler and H. von Halban, jun.
Editor's Note
Because roughly 3.5 neutrons a... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 's, which is to be taken over all kinds of nuclei present in the solution; ν is the average number of neutrons liberated in one fission, α
the average probability for a neutron to diffuse out of the system before being absorbed.
中文
The energy liberated by the chain will be
E = NF,
(2)
F
being the energy liberat... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | Added in proof
: In the case of a chain propagating itself by thermal neutrons, the time necessary for the slowing down and for the absorption of a neutron, that is, its mean life, is of the order of 10−4
sec. If one makes ν′′ as small as 1,007, it needs 100 times the mean life of a neutron or about 10−2
sec. to dou... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 英文
不过,我们可以引入一种吸收剂,比如镉,它的截面不依赖于热区的中子的能量。我们将用下面的式子来代替式(1):
其中A′
是所有遵循1/υ
定律的Ai
的和,而Ac
是一个常数,它取决于新加入的吸收剂。此时的ν′′将会随着温度的增加而减小。在系统的组成和几何常数的特征温度下,ν′′会变得比1还小,而系统则会在该温度附近的某个温度下达到自稳定;平衡是由下面的事实所决定的,即单位时间内系统释放出的能量大小(以热或者核辐射的形式)等于系统产生的能量。佩兰曾经讨论过类似的问题[3]
。
英文
附加说明
:在热中子所导致的自持增殖链的情况中,对中子慢化和吸收所需要的时间,即中子的平均寿命,为10–4
秒的数量级。... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | I have made some experiments on the same problem by a different method. Any increase of neutron effects observed when neutrons are allowed to pass through a given medium may be due: (a
) to the inelastic scattering of neutrons, (b
) to the reaction (n,
2n
) or, exceptionally (n,
3n
); (c
) to an unknown cause, a... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | of paraffin wax of 6 mm. thickness. The results are given below, the figures being the total numbers of counts of a Geiger-Müller counter in corresponding series.
中文
中文
It can be inferred from these data that uranium gives off, in fact, more neutrons than aluminium or copper. The increase is larger relatively to ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 这一结论在这几位作者随后的一篇文章[2]
中得到证实,他们发现由铀贡献的中子能够产生吸能反应S(n, p
)P。
英文
我对同样的问题用不同方法做了一些实验。在令中子通过一种给定介质的实验中,所观察到的中子效应的任何增长都可能是由于以下原因造成的:(a
)中子的非弹性散射;(b
)(n
,2n
)反应,个别时候是(n
,3n
)反应;(c
)未知原因,就像在铀核裂变的情况中那样。在哈尔班、约里奥和科瓦尔斯基的实验中,由于集成方法的采用和初级中子的能量较低,故可以排除效应(a
)和(b
)。但是如果这些效应存在的话,就有可能通过将铀与只可能有(a
)效应或只有(a
)和(b
)效应的物质进行比较,进而... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | HE first indication that the transmutation of heavy nuclei could be effected in a laboratory experiment was obtained by Fermi in March 1934. Curie and Joliot had just discovered that short-lived radioactive species are produced as the result of α
-particle bombardment of certain light elements, and Fermi, accepting th... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | = 92, 91, 90, 89, 88, 83 or 82. It seemed quite clear, then, that after the uranium nucleus had captured a neutron, not less than two β transformations followed, and consequently that a new element, for which Z
was not less than 94, was ultimately produced. These conclusions at once gave rise to much argument amongst ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | hours period, and at once proceeded to investigate the chemical nature of the element to which it belonged. They showed that this radioelement did not separate with the platinum precipitate and soon discovered that it bore a close resemblance to lanthanum in chemical behaviour. At first the most plausible suggestion ap... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | discussed the problem on the Bohr theory of heavy nuclei, making particular use of the essentially classical “water-drop model” of the highly condensed system of particles of which such a nucleus is constituted. They concluded, “It seems therefore possible that the uranium nucleus has only small stability of form, and ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | Perhaps the first such feature concerns the radioelements of the platinum precipitate, of which the previously supposed transuranic nature was now in question. Before the fission process was discovered, both in Berkeley and in Cambridge projects had already been formed of investigating these elements for natural X-radi... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | = 93 is formed as the result of the disintegration. Yet, in spite of much careful investigation, no radioactivity of any kind has been discovered which is unquestionably due to the transformation of this species. Furthermore, in respect of the parent species (the uranium isotope for which τ
= 23 min.), this is clearly... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | Hitherto, the process of fission has been spoken of without any precise statement regarding the nature of the fragments which result from the primary act of division of the nucleus, and in fact very little exact knowledge is as yet available on this point. Determinations of the range of the fission products provide som... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | The frequency of the neutron-evaporation process accompanying fission, and the energies of the neutrons so produced, have been studied by many workers, but so far most exhaustively by Joliot22
and his colleagues, and by Fermi23
and others in New York. The general result appears to be that, for each process of fission... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 居里和约里奥刚刚发现α
粒子轰击某些轻元素时会产生短寿命的放射性核素,费米便认识到这种“诱发的”放射性的出现可以作为嬗变的证据,并且很快指出,几乎所有元素的核——即使是那些具有最大原子量的核——在用中子轰击时都会发生转变。费米根据自己的早期实验推断,中子通常只是被核俘获,他接着指出,当撞击前的中子以慢的(“热”)速度运动时,这个俘获过程一般会比它具有高能量时更为有效——而且有时会高效很多。最后他发现,在所有这些俘获转变中生成的放射性产物,它们的分裂都会释放出负电子。因此,在任何情况下,兼有中子俘获与β蜕变的组合过程的最终结果都显示出,生成的核的质量和电荷数都比被轰击核大一个单位。
英文
1934年6月[1]
,费米及其合作... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 英文
由迈特纳和弗里施所开创的研究很快便引发了欧洲及美国物理实验室的众多研究人员的追随:哈恩和施特拉斯曼对居里与萨维奇的发现进行的证实已经向很多研究者非常明确地指出,这涉及到了某些新的事物。在巴黎、伯克利、华盛顿、纽约和巴尔的摩,短短几天的时间内就得到了有关铀和钍裂变的直接证据。现在,在最初宣布之后大约三个半月的时间内,已经发表了大量的文章,这样就有必要对关于这一主题的报道进行严格的筛选。因此,在这篇综述的其余部分中将只能包括有关新现象的最值得关注的特征。
英文
也许第一个值得关注的特征就是关于铂沉淀物中的放射性元素,以前曾认为其所具有的超铀性质现在遭到了质疑。在发现裂变过程之前,对这些元素的天然X辐射研究项目在伯克利和剑桥... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 英文
对于伴随裂变的中子蒸发过程的频率,以及这种过程中产生的中子的能量,已经有很多研究者进行过研究,但是到目前为止最为详尽的当属约里奥[22]
和他的同事,以及费米[23]
和另外一些来自纽约的研究者。看来一般性的结论是,对于铀的每一次裂变过程,至少有两个具有106
电子伏数量级的平均能量的中子,最终会从残存碎片中蒸发。由于能量比这还低的中子仍然可以靠自己来产生裂变(如前所述,可能是在铀–235中),因此必须要对可能出现的放热分裂累积过程加以考虑。很明显,除了中子导致裂变的可能性之外,如果过程中消去中子的可能性充分减小,那么对任何含铀的固体物质,裂变过程最终都一定会逐渐累积。在科学文献中还没有关于该问题的直接实验的报道,但是... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | , elastic collisions of fast neutrons with heavier nuclei are observed by means of an ionization chamber filled with a gas at atmospheric pressure and connected to a linear amplifier. In order to study separately the effect due to the primary thermal neutrons, the experiment is performed with, and without, a cadmium sh... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | notably more frequent in the absence of cadmium and, therefore, that neutrons possessing an energy of at least
11 Mev. are liberated in uranium irradiated with thermal neutrons
.
中文
The high energy of these fast neutrons shows that their parent nuclei are in a highly excited state at the moment of their liberation... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 分布曲线显示,观测到的脉冲频率在能量1.5兆电子伏到2.5兆电子伏之间快速下降;在能量2.5兆电子伏到3.7兆电子伏之间,频率的下降减慢了很多,不过,在这第二个能量区域所观测到的脉冲非常稀少。记录到的总的脉冲数很少(使用镉时:90分钟里有84个脉冲;不使用镉时:90分钟里有161个脉冲);但是似乎很明确的是,在没有镉时能量约为2.5兆电子伏的反冲明显出现得更为频繁,因此,用热中子辐照铀时释放出至少具有11 兆电子伏能量的中子
。
英文
这些快中子所具有的高能量表明,在它们释出时其母核处于高激发态,释出与裂变可能是同时发生的。这样,裂变能中不容忽视的一部分就被转移走了;更大的一部分则被在裂变中生成的核通过发射β射线和γ射线带走... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | simultaneous advances in the study of the nucleus, by bombardment with swift-moving primary particles, enhanced the desire for individual isotopic species of the elements, at the same time that it provided an alternative tool for research in the form of artificially produced radioactive elements.
中文
The successful s... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | N has been made available in large amounts of moderate concentrations and smaller amounts of highly concentrated heavy isotope. In this method, ammonia gas is exchanged counter current with ammonium ion in a column, the heavy nitrogen accumulating at the bottom. The success of this process makes 100 percent 15
N avail... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | is the most interesting, and of great promise for the general solution of the problem of separation of gaseous and liquid isotopic materials in quantity. Clusius combines the well-known thermal diffusion process, suggested by Chapman, with a thermal syphoning process by carrying out the separation in vertical tubes in ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | atomic weight units was secured. In a metre tube with a glass core heated internally, Brewer and Bramley4
showed that a 27 percent enrichment of ammonia at the bottom of the column with 50:50 methane (16)–ammonia (17) mixtures could be secured in fifteen minutes under favourable pressure and temperature gradient condi... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | It is obvious that the maintenance of this separation factor will result in concentrations of upwards of 20 percent 13
C at the bottom of the column when the normal ratio of 1.1 percent 13
C is kept at the top of the column. Such experiments are in progress. In the 12-metre tube, 3.76 litres of gas at 20 cm. pressure... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | , 27
. 260 (1939).
Phys. Rev.
, 55A
, 590 (1939); Amer. Chem. Soc. Abstracts,
Baltimore Meeting, April 1939.
Naturwiss.
, 27
, 230 (1939).
Phys. Rev.
, in the press.
Naturwiss.
, 27
, 110 (1939).
同位素分离的新视野
泰勒
编者按
哈罗德·尤里在1932年关于氢元素由两种同位素组成(一种是普通氢,其原子核中只有一个质子;另一种较重的同位素,其核由紧密结合在一起的一个质子与一个中子构成)的发现,激起了人们对其他... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 在相同的管子中,经过一次操作,可以使氯化氢中氯的同位素比从76:24变为60:40。克劳修斯与迪克尔最近[2]
声称,他们使用一根总长36米的管子,每天可以得到8立方厘米的盐酸,其中99%的氯质量数为37。同时,管子的顶部生成了2升盐酸(Cl=35.147),其中每升又可以产生25立方厘米的盐酸(Cl=35.06)。受该元素敛集率的影响,继续对此溶液进行纯化应该可以得到原子量刚好低于35的氯。
英文
格罗特[3]
对此方法进行了验证,他将氙同位素的分离与12级的赫兹扩散泵系统进行了比较,后者在2毫米大气压下于12小时内产生了0.5个单位的原子量变化。在大气压下实现相同的原子量改变需要使用长2.5米、壁厚12毫米的管子,管子... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 英文
(王耀杨 翻译;汪长征 审稿)
Nuclear Reactions in the Continuous Energy Region
N. Bohr et al
.
Editor's Note
The chief interest of this Letter to Nature
is its authors: Niels Bohr at Copenhagen was the acknowledged father of quantum mechanics, Rudolf Peierls was a graduate research worker at Copenhagen who eventually migra... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | is deflected without actually getting into close interaction with the individual constituents of the original nucleus.
中文
On these assumptions a very general conservation theorem of wave mechanics1
yields the relation
where λ is the wave-length of the incident particle and l
is the angular momentum.
中文
In the ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | , which in this case is well defined.
中文
In the continuum, (3) must be identical with (2), since the cross-section does not vary appreciably over an energy interval containing many levels, and hence, comparing (2) and (3)
where the superscript A
has been added to the probabilities occurring in (1) in order to show... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | , it is thus a reasonable idealization to assume that, even in the continuum, all
are equal to
, except, of course, for A
=B
, where we have seen in (4) that the phases are necessarily such as to favour the re-emission of the incident particle.
中文
A typical case of a reaction in the continuum is the nuclear ph... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | The details of this and of the other arguments of this note will be published in the Proceedings of the Copenhagen Academy
.
Bothe, W., and Gentner, W., Z
. Phys
., 106
, 236 (1937); 112
, 45 (1939).
连续能量区域的核反应
玻尔等
编者按
这篇寄给《自然》的通迅最令人感兴趣的是他的作者:哥本哈根的尼尔斯·玻尔,他是众所周知的量子力学之父,鲁道夫·佩尔斯为哥本哈根的研究生,最后移居英国,是应用热扩散过程来分离同位素方法的设计... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 如果我们假定没有其他的特殊情况可以导致
对A
的依赖性,那么除去A=B
的情况以外,理想化地假定所有
是合理的,即使是在能量连续的体系中,正如我们在式(4)看到的那样,该状态必然更有利于产生入射粒子的再发射过程。
英文
在能量连续体系中的一个典型反应是重元素原子的光电效应,由17毫伏的γ射线引发。博特和根特纳在最初的实验中发现,不同元素的有效截面明显不同,但是他们后来的研究[2]
又表明这种不同可以用残余核子的放射性差异来解释,而且所有重元素在光电效应中的有效截面均为5×10–26
平方厘米的量级。
英文
在前面基于式(1)和(2)的讨论中,由于没有清楚地认识到
之间的差别,我们发现要解析这种大小的光电效应... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | , the grid leak being 1011
ohms and the sensitivity 1.2×10–15
amp./div. on the scale.
中文
We have employed two experimental arrangements in which the source was placed (1) between the chamber and the substance used as scatterer, the nature and the thickness of which were variable; (2) in the centre of a cube of 16 ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | being only as a correction term in the determination of the mean free path λ and the average distance L
travelled by the neutrons before they escape from the whole mass, which is supposed spherical, the radius being r
and
. This experiment, taking into account the results of the previous experiments, gives for lead... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | for the uranium nucleus is (11.2±1.5)10–24
cm.2
. This value implies a mean path in uranium much shorter than that usually admitted; this suggests that smaller masses than those hitherto expected might be used to show chain fission.
中文
(144
, 201-202; 1939)
La. Goldstein, A. Rogozinski and R. J. Walen: Laboratoir... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 英文
第二种实验我们在一阶近似下给出了吸收系数(1–ki
)σi
+(1–kr
νr
)σr
的值,σe
的值只是作为中子从假设为球形的块状物体逃逸前的测定平均自由程λ
和中子穿行平均距离L
的修正项,球块的半径是r
,且
。考虑到以前实验的结果,这个实验给出了铅的
平方厘米。假定σi
的值能达到σe
值[3]
的30%,则有
。
英文
对于铀我们不仅要考虑σi
,还要考虑νr
σr
,而对于其他物质很有可能由于ki
的值很小,σt
与σe
的值相差并不大。
英文
对于铀的情况,我们有
英文
如果假定每次裂变都产生放射性元素,约里奥和安德森等人[... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | are isomeric nuclei. The problem of uranium Z has been taken up recently by Feather and Bretscher (Proc. Roy. Soc.
, 165
, 542; 1938). It should be noted that, for many years, uranium Z and uranium X2
were the only known example of an isomeric pair.
中文
After the discovery of artificial radioactivity, the study of... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | . Selection rules may then be invoked to weaken considerably the probability per unit of time of the transition from the upper to the ground state of the nucleus. Of course, experiments which make it possible to test the truth of Weiszäcker's hypothesis are of great interest.
中文
One of the most important points is t... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | . In particular, in the cases of isomeric nuclei of radio-bromine8
and of element 439
, strong lines of conversion electrons have been photographed in the Wilson chamber or in the magnetic spectrograph. Of course, the internal conversion is accompanied by emission of X-rays: as a rule, the analysis of these rays is a... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | that β-stable nuclei with a metastable excited state ought not to be very rare and should be revealed by the study of the radiation emitted by this metastable state. These nuclei are interesting for the understanding of nuclear isomerism, because the radiation corresponding to the transition from one isomeric state to ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | In* has not yet been sufficiently studied; its properties are of the greatest interest both for the understanding of the nuclear isomerism and for that of isobaric pairs. In effect, 115
In and 115
Sn are one of the rare cases of stable neighbouring isobaric nuclei: 115
In* might then decay into 115
Sn (β-emission) ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | There is no doubt that new isomers of β-stable nuclei will be discovered, in the course of research undertaken in different laboratories; systematic research on the radiations emitted by metastable states will certainly be very useful for the understanding of nuclear isomerism.
中文
In conclusion, we may remark that i... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | , 681 (1939).
Seaborg and Segré, Phys. Rev
., 55
, 808 (1939). Kalbfell, Phys. Rev.
, 54
, 543 (1938).
Alvarez, Phys. Rev.
, 54
, 486 (1938). Roussinow, Yusephovitch, Phys. Rev.
, 55
, 979 (1939). Siday, ref. 8. Walke, Williams and Evans, Proc. Roy. Soc.
, A, 171
, 360 (1939).
Segré, Halford and Seaborg, Phys... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 目前已知道超过30对这样的核,并且毫无疑问的是,尚未发现的同质异能核对比这数目要多得多。现在我们可以说,核的同质异能性绝对不是一种个别现象
。
英文
我们可以很自然地想到,两个同质异能核之间的物理差异与相同原子核的两个不同激发态有关(比如说基态和第一激发态)。但是,在这种情况下,高能态是如何成为亚稳态的,或者说,它怎么能维持这么长时间(在某些情况下甚至超过一天)呢?是什么机制使它们免于在很短时间内通过发射电磁辐射而崩溃呢?魏茨克回答了上述问题[4]
。
英文
根据魏茨克的假说
,核的同质异能现象可以这样解释:即假定核的最低激发态具有与基态相差若干单位的角动量
。这样,根据选择规则,原子核在单位时间内从上述激发态跃... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 因此,周期为6小时的放射性是一种β放射性钼的子体。
英文
戈德哈伯、齐拉特和希尔[14]
曾观测到一种非常有趣的情况,并对其进行了充分的研究。他们通过上面提到的(n,n
)反应得到了115
In的一个半衰期为4.1小时的亚稳态(115
In*),此外,一种放射性镉(T
=2.5天)衰变后也能得到同样的态。115
In*发射出的辐射还没被充分的研究;它的性质对理解核的同质异能现象与同量异位对来说都是非常重要的。实际上,115
In与115
Sn是稳定的相邻同量异位核的罕见实例之一:115
In*可以衰变成115
Sn(β辐射),或者衰变成115
In,或者同时衰变成这两种元素。
英文
巴恩斯与阿拉丁[... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | He was awarded a Nobel Prize in 1950 for precisely this work.
中文
T
HE heavy ionizing particles in the cosmic rays are so rare that it seems unlikely that much information can be obtained from experiments with cloud chambers. The only method at present available which can yield quantitative results is the method of ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | It will be seen that radiation primarily responsible for the long tracks suffers practically no absorption in lead but is strongly absorbed in air. The short tracks also indicate that the primary radiation giving rise to them is strongly absorbed in air but not in lead. (Probably most of the short tracks on the Bristol... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | -ray tracks. The fifth track is 14 cm. long and has an average grain density of about three times
that of α
-rays of 8 cm. range. Considering that there is very little difference between the grain density produced by protons and α
-particles of the same range, we must ascribe this track to a heavy particle with a ve... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 英文
在对发生的各种过程进行解释时,首先遇到的问题是相应于那些重电离粒子径迹的原初射线的性质;因此我们分别测量了其在铅和空气中被吸收的情况。用不同厚度的铅覆盖一组半色调的伊尔福底片(感光乳胶厚度为70微米,对α
粒子和质子敏感),分别放置在少女峰和布里斯托尔,并让其在宇宙射线中曝光230天。我们把观测到的径迹按照其长度(即出现在乳胶上的那部分径迹的长度)分作两类:(i)长度小于10 cm air(即10厘米等效空气长度)的径迹,(ii)长度大于10 cm air的径迹。第一类径迹大部分是由放射性污染引起的,而第二类径迹全部是由宇宙射线产生。具体的实验结果如下表所示:
英文
由上表可见,相应于长程径迹的原初射线实际上在铅中... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | Hubble mentions a red-shift of +0.231 A. This corresponds to a velocity of recession of approximately 43,000 miles per second, nearly a quarter of the velocity of light! The conviction grows upon one that these fantastic velocities are not real.
中文
Alternative interpretations of the red-shift have been proposed, but... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | (1) holds good for sources of light near and far, by comparing a grating and a prism spectrogram of the emission spectrum of the nucleus of N.G.C.
4151.
(3) The wave-length is constant during the light's journey: this assumption is accepted as correct when measuring radial velocities.
(4) The frequency n
of a newly g... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 中文
The slowing down of the frequency and of the velocity both follow linear laws: n
′(×1012
)= 762.2–0.4T
; and c
0
(Km./sec.)=299,774–173T
, where T
is in millions of years.
中文
Accordingly, 240 millions years ago, light travelled with a velocity approximately 13 percent greater than now, and the wave-length ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 光在传播的过程中,光速c
0
和频率n
都不断减小,直至到达地球,此时二者分别变为c
和n
′,但是它们仍然满足关系c
=n
′λ0
(3),其中n
′<n
。由于c
0
>c
,根据(2)式可得λ0
>λ,其中,λ为实验室光源的波长。该不等式也可以写为λ0
=λ+d
λ,这就是我们观测到的红移现象。
英文
在表2中,mc
表示每个星团中亮度排名第五的星云的光度(这些星团非常相似,所以可以用于精确的距离测量),d
λ/λ表示观测到的红移[1]
。R
表示以光年为单位的距离,由下面的关系式可确定R
:logr
=0.2mc
+4.803。λ0
是Ca+
的K
线的初始波长,可以... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | OSMIC ray ionization bursts produced by showers of ten or more particles in a small ionization chamber (volume 1 litre) have been recorded at sea-level in Cambridge and, thanks to the hospitality of Prof. P. M. S. Blackett and Dr. H. J. J. Braddick, under 30 m. of clay in London. The data discussed here, curves A
(150... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | with counters. We should not expect to find exactly the ratio of the areas (approximately 1:30) because narrow showers or condensations of rays of cross-section smaller than the area of the large chamber tend to increase disproportionately the bursts in the small chamber.
中文
中文
The bursts which are found undergro... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | We think, therefore, that nearly all the showers which produce bursts at sea-level in our thin-walled ionization chambers originate very high in the atmosphere, and that the dual nature of the distribution curve at sea-level (as indicated by the change of slope) is due, not to the existence of showers of two kinds, but... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 英文
英文
在地面以下测量到的爆发(B
曲线)肯定是由穿越了的宇宙射线产生的。利用霍米·巴巴[4]
在其论文里给出的数据,假设介子的自旋为
,我们已经计算出由电子被介子撞击而产生的级联簇射在地铁站里的预期曲线分布。根据欧拉和海森堡[3]
的方法,我们认为大气中介子累积能量分布曲线的指数为1.87。如果我们假设在地面以下的实验中,簇射区域的横截面不比电离室大多少,那么从计算结果中可以看到(m
曲线):仅由介子和电子的碰撞过程所产生的簇射就足以解释在地面以下记录的爆发了(实际上测量到的大型爆发数值要多于计算值,对这种差异的理论解释将在以后讨论)。
英文
在海平面上用上述方法得到的计算值(n
曲线)比观察到爆发的... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | The question “How could the world's population be improved most effectively genetically?” raises far broader problems than the purely biological ones, problems which the biologist unavoidably encounters as soon as he tries to get the principles of his own special field put into practice. For the effective genetic impro... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | work of the community at large. These objects cannot be achieved unless there is an organization of production primarily for the benefit of consumer and worker, unless the conditions of employment are adapted to the needs of parents and especially of mothers, and unless dwellings, towns and community services generally... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | Before people in general, or the State which is supposed to represent them, can be relied upon to adopt rational policies for the guidance of their reproduction, there will have to be, fifthly, a far wider spread of knowledge of biological principles and of recognition of the truth that both environment and heredity co... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | Sixthly, conscious selection requires, in addition, an agreed direction or directions for selection to take, and these directions cannot be social ones, that is, for the good of mankind at large, unless social motives predominate in society. This in turn implies its socialized organization. The most important genetic o... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | genetics is beset with special difficulties which require the prosecution of research in this field to be on a much vaster scale, as well as more exact and analytical, than hitherto contemplated. This can, however, come about when men's minds are turned from war and hate and the struggle for the elementary means of sub... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 英文
有效遗传改良的第四个必要条件就是曾经奏效的生育控制手段的合法化、广泛传播以及通过科学研究使其进一步发展,不论消极的还是积极的,这些措施都能在生育过程的所有阶段实施——如自愿进行的暂时性或永久性绝育、避孕、流产(作为第三道防线)、控制生育力和生殖周期、人工受精等。与此同时,还需要与生育孩子相关的社会意识和社会责任的发展,并且只有上述所需的经济和社会条件都具备,以及现在盛行的关于性别和生育的迷信态度都已被科学的社会态度所取代的时候,这一发展才可能是切实有效的。对一位无论是已婚还是未婚的母亲或者一对夫妻而言,这将使得即便不会视生育为一项责任,也会视其为使拥有最好的孩子成为可能的一项荣誉和权利,这包括对他们的养育和遗传赋予,后者甚至... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 英文
英文
(刘皓芳 翻译;刘京国 审稿)
Myosine and Adenosinetriphosphatase
W. A. Engelhardt and M. N. Ljubimowa
Editor's Note
Here biochemist Wladimir Engelhardt and his wife and former postgraduate student Militza Ljubimowa, both from Moscow's Academy of Sciences, show that myosine (now myosin), one of the contractile proteins ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | myosine takes place. Under the conditions of our experiments (optimal conditions have not been determined) the activity of myosine preparations ranged in different experiments from 350 to 600 microgram phosphorus liberated per mgm. nitrogen in 5 min. at 37°. Expressed as
this gives values of 500-850.
中文
Acidificati... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | -phosphatase and yields adenosinediphosphate, which is not further dephosphorylated and has been isolated in substance. This may serve as a convenient way of preparing adenosinediphosphate, instead of using crayfish muscle4
. The adenosinediphosphatase is thus associated with the more soluble proteins, occupying an in... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 英文
通常肌肉中的水或氯化钾提取物仅具有微弱的矿化三磷酸腺苷的能力。即便是这种磷酸盐轻微的析出也不是主要由三磷酸腺苷(ATP)的直接水解引起的,而是由一个间接的矿化作用过程造成。这个过程通常伴随着磷酸盐从腺苷酸系统到肌氨酸的转移,并且会引起相应的酶(有人建议命名为“磷酸水解酶”)的可溶性增强。
英文
三磷酸腺苷酶在肌肉可溶性组分中含量很少,而相比之下,很高的三磷酸腺苷酶活性却与肌肉中的水不溶性蛋白质相结合。所有用来提取肌球蛋白的缓冲液及高浓度盐溶液,都可以很容易地使这种酶的活性溶于其中。这使得人们在从肌肉抽提物中分离肌球蛋白时,无论是采用透析、稀释、谨慎酸化还是盐析的方法,往往都可以在分离得到的肌球蛋白组分中检测到三磷酸腺苷... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | measured their strength. The two scientists later won the 1963 Nobel Prize in Physiology or Medicine for their work on how action potentials arise and spread in nerve cells.
中文
N
ERVOUS messages are invariably associated with an electrical change known as the action potential. This potential is generally believed t... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | mm. from its tip. A small action potential was recorded from the upper end of the axon and this gradually increased as the electrode was lowered, until it reached a constant amplitude of 80-95 mv. at a distance of about 10 mm. from the cannula. In this region the axon appeared to be in a completely normal condition, fo... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | 从神经纤维内记录到的动作电位
霍奇金,赫胥黎
编者按
在这篇论文之前,从未有人成功地测得神经纤维内的电脉冲或者“动作电位”。在此,来自普利茅斯英国海洋生物协会实验室的生理学家艾伦·劳埃德·霍奇金与安德鲁·菲尔丁·赫胥黎(托马斯·亨利·赫胥黎的孙子)利用巨型乌贼相当大的神经纤维(轴突)完成了这一壮举。他们的研究证明了动作电位——可自行传导的电化学波——产生于细胞表面,并且第一次测量了它们的强度。后来,这两位科学家因为他们在神经细胞中动作电位的产生和传播方面的研究工作而获得了1963年诺贝尔生理学或医学奖。
英文
神经信号常与被称为动作电位的电学变化相联系。人们普遍认为,这种电位出现在位于轴突细胞质与外部介质之间的隔膜处。如... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | active periods. The associations are now well established, but remain controversial in terms of their implications for solar effects on climate change.
中文
M
ANY attempts have been made in the past to correlate solar and terrestrial phenomena. Until quite recently, the only one that was found to show a clearly measu... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | gravitation and electrical forces.
中文
Radiation pressure is insufficient to support the whole mass of chromospheric gases, but the dynamical concept of turbulence has partially solved this difficulty. A turbulent velocity of 15 km./sec. in the chromosphere is indicated; in the lower layers it is on a much smaller sc... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | It is natural to inquire whether this relationship is due to the presence of chromospheric eruptions, which are most commonly observed in or near large active sunspots. A distinct relationship has been established between eruptions and magnetic storms, similar to that with sunspots. Of the twenty-nine greatest eruption... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | A further relationship between sunspots and terrestrial magnetism is shown by the fact, known for many years, that magnetic storms tend to recur at intervals of one synodic solar rotation (about 27 days). A catalogue of 403 storms based on Greenwich records for the years 1874-1927 has been used to study this relationsh... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | with great accuracy, and, with the help of knowledge of atomic energy levels, attributed to “forbidden” transitions of neutral oxygen.
中文
The presence of ionized oxygen and nitrogen indicates the action of particles of high energy. The work of Störmer has shown how the streamers may be identified with the paths of e... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | layers. Finally, the absorption coefficient for rays in a large range of wave-length (100-1,000 A.) is a maximum, so that these rays will produce an ionization maximum at about the same height—calculated to be 200 km.—which will be confined to the sunlit hemisphere. This maximum is identified by Vegard with the F
1
la... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0302. 《自然》百年科学经典（第三卷）(英汉对照版)(1934-1945).epub | .epub | 24,505,760 | 2025-09-26T19:07:02.019948 | The question of the ultimate character of the short-wave solar radiation associated with these disturbances (for example, its frequency and whether it consists of continuous or line-emission) is still quite unsettled. The spectrum of chromospheric eruptions in the observable range has been found to consist of lines due... | 400套付费套装书 |
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