首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1371134篇
  免费   25799篇
  国内免费   7760篇
化学   680008篇
晶体学   20901篇
力学   75964篇
综合类   104篇
数学   245968篇
物理学   381748篇
  2021年   13489篇
  2020年   15910篇
  2019年   16045篇
  2018年   15611篇
  2017年   14278篇
  2016年   29072篇
  2015年   21103篇
  2014年   30429篇
  2013年   74331篇
  2012年   39292篇
  2011年   38535篇
  2010年   39416篇
  2009年   41697篇
  2008年   37580篇
  2007年   34111篇
  2006年   36344篇
  2005年   31714篇
  2004年   31338篇
  2003年   29281篇
  2002年   29616篇
  2001年   27686篇
  2000年   24463篇
  1999年   22356篇
  1998年   20949篇
  1997年   20932篇
  1996年   21085篇
  1995年   19129篇
  1994年   18588篇
  1993年   18150篇
  1992年   17960篇
  1991年   18311篇
  1990年   17501篇
  1989年   17563篇
  1988年   17135篇
  1987年   17163篇
  1986年   16005篇
  1985年   22479篇
  1984年   23748篇
  1983年   19943篇
  1982年   21632篇
  1981年   20880篇
  1980年   20218篇
  1979年   20371篇
  1978年   21691篇
  1977年   21279篇
  1976年   20966篇
  1975年   19708篇
  1974年   19311篇
  1973年   19854篇
  1972年   14311篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
841.
842.
A physical program of irradiation of emulsions in beams of relativistic nuclei named the BECQUEREL Project is reviewed. It is destined to study in detail the processes of relativistic fragmentation of light radioactive and stable nuclei. The expected results would make it possible to answer some topical questions concerning the cluster structure of light nuclei. Owing to the best spatial resolution, the nuclear emulsions would enable one to obtain unique and evident results. The most important irradiations will be performed in the secondary beams of He, Be, B, C, and N radioactive nuclei formed on the basis of JINR Nuclotron beams of stable nuclei. We present results on the charged state topology of relativistic fragmentation of the 10B nucleus at low energy-momentum transfers as the first step of the research.  相似文献   
843.
844.
845.
Beloshapka  V. K. 《Mathematical Notes》2004,75(3-4):475-488
In previous papers by the present author, a machinery for calculating automorphisms, constructing invariants, and classifying real submanifolds of a complex manifold was developed. The main step in this machinery is the construction of a “nice” model surface. The nice model surface can be treated as an analog of the osculating paraboloid in classical differential geometry. Model surfaces suggested earlier possess a complete list of the desired properties only if some upper estimate for the codimension of the submanifold is satisfied. If this estimate fails, then the surfaces lose the universality property (that is, the ability to touch any germ in an appropriate way), which restricts their applicability. In the present paper, we get rid of this restriction: for an arbitrary type (n,K) (where n is the dimension of the complex tangent plane, and K is the real codimension), we construct a nice model surface. In particular, we solve the problem of constructing a nondegenerate germ of a real analytic submanifold of a complex manifold of arbitrary given type (n,K) with the richest possible group of holomorphic automorphisms in the given class.  相似文献   
846.
The title compound is a centrosymmetric dimer with each cadmium in a distorted CdS5 square pyramidal geometry. The Cd–S bond distances range from 2.5626(11) to 2.8459(11) Å. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
847.
848.
849.
The sorption properties of stationary phases based on nematic p-substituted azoxybenzenes were studied. Correlations were revealed between the structural selectivity of mesogens, chemical nature of terminal substituents, capability for dispersion interactions and polarity of the sorbents, temperature gradient of the retention indices, and thermodynamic parameters of solution of xylene isomers in the sorbents.  相似文献   
850.
Linear nth order (n?3) ordinary differential equations have been shown to possess n+1, n+2 or n+4 Lie point symmetries. Each class contains equations which are equivalent under point transformation. By taking the example of third order equations, we show that all linear equations are equivalent if the class of transformation is broadened to include nonlocal transformations and hence the representative of this class of equations is y(n)=0.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号