全文获取类型
收费全文 | 1014篇 |
免费 | 23篇 |
国内免费 | 11篇 |
专业分类
化学 | 725篇 |
晶体学 | 5篇 |
力学 | 24篇 |
综合类 | 7篇 |
数学 | 138篇 |
物理学 | 149篇 |
出版年
2019年 | 8篇 |
2018年 | 13篇 |
2017年 | 9篇 |
2016年 | 17篇 |
2015年 | 15篇 |
2014年 | 21篇 |
2013年 | 37篇 |
2012年 | 31篇 |
2011年 | 42篇 |
2010年 | 21篇 |
2009年 | 26篇 |
2008年 | 41篇 |
2007年 | 33篇 |
2006年 | 30篇 |
2005年 | 20篇 |
2004年 | 34篇 |
2003年 | 29篇 |
2002年 | 30篇 |
2001年 | 12篇 |
2000年 | 15篇 |
1999年 | 19篇 |
1996年 | 12篇 |
1993年 | 11篇 |
1992年 | 16篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1974年 | 7篇 |
1944年 | 9篇 |
1943年 | 7篇 |
1916年 | 7篇 |
1915年 | 8篇 |
1911年 | 8篇 |
1910年 | 12篇 |
1909年 | 10篇 |
1908年 | 7篇 |
1907年 | 8篇 |
1901年 | 8篇 |
1900年 | 12篇 |
1898年 | 11篇 |
1895年 | 7篇 |
1892年 | 11篇 |
1891年 | 12篇 |
1890年 | 9篇 |
1882年 | 10篇 |
1870年 | 8篇 |
1866年 | 7篇 |
排序方式: 共有1048条查询结果,搜索用时 140 毫秒
1.
Ohne Zusammenfassung 相似文献
2.
E. Utescher Ed. Ritsert Th. Salzer und C. Schwarz 《Fresenius' Journal of Analytical Chemistry》1888,27(1):665-668
Ohne Zusammenfassung 相似文献
3.
Mao‐Chuan Yuan Ping‐I Shih Chen‐Han Chien Ching‐Fong Shu 《Journal of polymer science. Part A, Polymer chemistry》2007,45(14):2925-2937
We have synthesized a blue‐light‐emitting polyfluorene (PF) derivative ( PF‐CBZ‐OXD ) that presents bulky hole‐transporting carbazole and electron‐transporting oxadiazole pendent groups functionalized at the C‐9 positions of alternating fluorene units. The results from photoluminescence and electrochemical measurements indicate that both the side chains and the PF main chain retain their own electronic characteristics in the copolymer. An electroluminescent device incorporating this polymer as the emitting layer was turned on at 4.5 V; it exhibited a stable blue emission with a maximum external quantum efficiency of 1.1%. Moreover, we doped PF‐CBZ‐OXD and its analogue PF‐TPA‐OXD with a red‐light‐emitting iridium phosphor for use as components of phosphorescent red‐light emitters to investigate the effect of the host's HOMO energy level on the degree of charge trapping and on the electrophosphorescent efficiency. We found that spectral overlap and individual energy level matching between the host and guest were both crucial features affecting the performance of the electroluminescence devices. Atomic force microscopy measurements indicated that the dipolar nature of PF‐CBZ‐OXD , in contrast to the general nonpolarity of polydialkylfluorenes, provided a stabilizing environment that allowed homogeneous dispersion of the polar iridium triplet dopant. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2925–2937, 2007 相似文献
4.
We shall answer several questions concerning additive or multiplicative commutators in a division ring which are algebraic of bounded degree over its center. 相似文献
5.
D. Fong J. H. Hamilton A. V. Ramayya J. K. Hwang C. Goodin K. Li J. Kormicki J. O. Rasmussen Y. X. Luo S. C. Wu I. Y. Lee A. V. Daniel G. M. Ter-Akopian G. S. Popeko A. S. Fomichev A. M. Rodin Yu. Ts. Oganessian M. Jandel J. Kliman L. Krupa J. D. Cole M. A. Stoyer R. Donangelo W. C. Ma 《Physics of Atomic Nuclei》2006,69(7):1161-1167
The hot bimodal fission of 252Cf is reexamined with new high-statistics data. We constructed a γ-γ-γ coincidence cube for binary fission and LCP-gated γ-γ matrix for ternary fission. By identifying the secondary fission fragments from their γ-ray transitions, we measured the yields for various fission splits. The normal neutron yield distribution is found to be
Gaussian for Xe-Ru. However, the binary fission split of Ba-Mo is found to exhibit a bimodal neutron distribution with the
“hot mode” corresponding to ≈3.1% of the total yield. In α ternary fission, the first measurements of yields for specific fission splits are presented. The Te-α-Ru and Xe-α-Mo neutron yields fit well with a single mode, but the Ba-α-Zr split shows evidence for an enhanced hot mode with an intensity of ≈13.8% of the normal mode.
The text was submitted by the authors in English. 相似文献
6.
This paper presents results on symmetries of the spectrum of singularities for random cascades found in the statistical theory of turbulence. It is shown that empirical dimension curves possess a natural symmetry whose presence restricts the class of allowable probability distributions of the cascade generator in a simple manner. In particular, necessary and sufficient conditions on the probability distribution of the generator are obtained for symmetry of the singularity spectrum within a large class of cascade models. 相似文献
7.
8.
Functionalised hydroxylamine derivatives of (S)-prolinol prepared by a Cope elimination have been found to undergo oxidation to the nitrone either in the presence of air or a catalytic quantity of TPAP. These undergo intramolecular cycloaddition to give tricyclic isoxazolidines with high diastereoselectivity. 相似文献
9.
G. M. Ter-Akopian A. V. Daniel A. S. Fomichev G. S. Popeko A. M. Rodin Yu. Ts. Oganessian J. H. Hamilton A. V. Ramayya J. Kormicki J. K. Hwang D. Fong P. Gore J. D. Cole M. Jandel J. Kliman L. Krupa J. O. Rasmussen I. Y. Lee A. O. Macchiavelli P. Fallon M. A. Stoyer R. Donangelo S. -C. Wu W. Greiner 《Physics of Atomic Nuclei》2004,67(10):1860-1865
Ternary fission of 252Cf was studied at Gammasphere using eight ΔE×E particle telescopes. Helium, beryllium, boron, and carbon light charged particles (LCPs) emitted with kinetic energy more than 9, 21, 26, and 32 MeV, respectively, were identified. The 3368-keV γ transition from the first 2+ excited state in 10Be was found and the population probability ratio N(2+)/N(0+) = 0.160 ± 0.025 was estimated. No evidence was found for 3368-keV γ rays emitted from a triple molecular state. For the first time, charge distributions are obtained for ternary fission fragments emitted with helium, beryllium, and carbon LCPs. 相似文献
10.
A ring is said to be a left essential extension of a reduced ring (domain) if it contains a left ideal which is a reduced ring (domain) and intersects nontrivially every nonzero twosided ideal of the ring. We prove that every ring which is a left essential extension of a reduced ring is a subdirect sum of rings which are essential extensions of domains, but the converse implication does not hold. We give some applications of this result and discuss several related questions.Received: 6 January 2003 相似文献