全文获取类型
收费全文 | 476514篇 |
免费 | 20356篇 |
国内免费 | 10596篇 |
专业分类
化学 | 253150篇 |
晶体学 | 5978篇 |
力学 | 25079篇 |
综合类 | 522篇 |
数学 | 76294篇 |
物理学 | 146443篇 |
出版年
2022年 | 4544篇 |
2021年 | 5279篇 |
2020年 | 5863篇 |
2019年 | 5445篇 |
2018年 | 14467篇 |
2017年 | 13949篇 |
2016年 | 13775篇 |
2015年 | 8338篇 |
2014年 | 9984篇 |
2013年 | 21129篇 |
2012年 | 22268篇 |
2011年 | 31018篇 |
2010年 | 18859篇 |
2009年 | 18915篇 |
2008年 | 23944篇 |
2007年 | 25507篇 |
2006年 | 17328篇 |
2005年 | 16228篇 |
2004年 | 14449篇 |
2003年 | 13028篇 |
2002年 | 11797篇 |
2001年 | 12333篇 |
2000年 | 9718篇 |
1999年 | 8208篇 |
1998年 | 6717篇 |
1997年 | 6537篇 |
1996年 | 6604篇 |
1995年 | 5890篇 |
1994年 | 5421篇 |
1993年 | 5090篇 |
1992年 | 5399篇 |
1991年 | 5206篇 |
1990年 | 4766篇 |
1989年 | 4433篇 |
1988年 | 4595篇 |
1987年 | 4190篇 |
1986年 | 4085篇 |
1985年 | 5655篇 |
1984年 | 5616篇 |
1983年 | 4550篇 |
1982年 | 4904篇 |
1981年 | 4892篇 |
1980年 | 4640篇 |
1979年 | 4730篇 |
1978年 | 4709篇 |
1977年 | 4674篇 |
1976年 | 4631篇 |
1975年 | 4533篇 |
1974年 | 4381篇 |
1973年 | 4561篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Based on the Collins formula and irradiance moments definition, the propagation of the kurtosis parameter of super-Gaussian beams through a spherically aberrated lens is studied. Detailed numerical results are given. It is shown that, as compared with aberration-free super-Gaussian beams, the profile of spherically aberrated super-Gaussian beams can be leptokurtic, mesokurtic or platykurtic, depending on the aberration and propagation distance. The results for the spherically aberrated Gaussian beams can be dealt with as a special case treated in this paper. Finally, the advantage of our method is pointed out. 相似文献
22.
It is explicitly shown that if phase transition occurs at the core of a newborn neutron star with moderately strong magnetic
field strength, which populates only the electron’s Landau levels, then in the β -equilibrium condition, the quark core is
energetically much more unstable than the neutron matter of identical physical condition. 相似文献
23.
We study the induced measure obtained from a 1-step Markov measure, supported by a topological Markov chain, after the mapping of the original alphabet onto another one. We give sufficient conditions for the induced measure to be a Gibbs measure (in the sense of Bowen) when the factor system is again a topological Markov chain. This amounts to constructing, when it does exist, the induced potential and proving its Hölder continuity. This is achieved through a matrix method. We provide examples and counterexamples to illustrate our results. 相似文献
24.
A convective flow CO laser composed of polytetrafluoroethylene discharge tubes, nickel–chromium steel components, a cupric heat exchanger and other components is described. Operating in liquid nitrogen condition, output power of 60 W has been obtained from a non-selective cavity. 相似文献
25.
Jeroen J. L. M. Cornelissen W. Sander Graswinckel Alan E. Rowan Nico A. J. M. Sommerdijk Roeland J. M. Nolte 《Journal of polymer science. Part A, Polymer chemistry》2003,41(11):1725-1736
The conformational properties of polymers derived from isocyanodipeptides have been investigated with a combination of model calculations, X‐ray diffraction, and circular dichroism spectroscopy. Depending on the configuration of the side chains, defined arrays of hydrogen bonds along the polymeric backbone are formed. This leads to a well‐defined conformation as, for example, expressed in the formation of lyotropic liquid‐crystalline phases and increased helical stability. Upon the disruption of the hydrogen bonds by a strong acid, a less well‐defined macromolecular conformation is observed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1725–1736, 2003 相似文献
26.
27.
Equilibrium Problems with Applications to Eigenvalue Problems 总被引:5,自引:0,他引:5
In this paper, we consider equilibrium problems and introduce the concept of (S)+ condition for bifunctions. Existence results for equilibrium problems with the (S)+ condition are derived. As special cases, we obtain several existence results for the generalized nonlinear variational inequality studied by Ding and Tarafdar (Ref. 1) and the generalized variational inequality studied by Cubiotti and Yao (Ref. 2). Finally, applications to a class of eigenvalue problems are given. 相似文献
28.
J. Krause und F. Umland 《Fresenius' Journal of Analytical Chemistry》1989,335(7):791-795
Summary This paper presents some applications of cyclic voltammetry at the interface of two immiscible electrolyte solutions by means of an experimental set-up described in a former publication. When using special sample preparation good results are obtained for the determination of iodide and quinine in pharmaceutical products as well as for the determination of quinine in tonic water and dodecylsulfate in a tooth-salt.
Herrn Prof. Dr. Günther Tölg zum 60. Geburtstag gewidmet 相似文献
Herrn Prof. Dr. Günther Tölg zum 60. Geburtstag gewidmet 相似文献
29.
X Y Liu C J Li 《Science in China. Series B, Chemistry, life sciences & earth sciences》1989,32(10):1215-1223
To further evaluate the causality between endogenous pyrogen (EP)-induced fever and cyclic adenosine-3',5'-monophosphate (cyclic AMP) level, the effects of sodium salicylate (SS) on the febrile response and increased levels of cyclic AMP in both cerebrospinal fluid (c.s.f.) and plasma during EP-induced fever in rabbits were observed. The results suggest that cyclic AMP is probably involved in the central mediation of EP-induced fever and that increased concentration of cyclic AMP in c.s.f. associated with EP-induced fever is not the result of temperature elevation but appears to be caused by the increased synthesis in the central nervous system. In addition it is confirmed that blood is impossibly a contributory source of increased cyclic AMP in c.s.f. during EP fever, and that SS may act subsequent to the increase in cyclic AMP. 相似文献
30.