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   21964篇
  免费   1149篇
  国内免费   1099篇
化学   8426篇
晶体学   171篇
力学   199篇
综合类   37篇
数学   13617篇
物理学   1762篇
  2024年   20篇
  2023年   126篇
  2022年   161篇
  2021年   171篇
  2020年   278篇
  2019年   655篇
  2018年   643篇
  2017年   447篇
  2016年   382篇
  2015年   523篇
  2014年   874篇
  2013年   1625篇
  2012年   965篇
  2011年   1304篇
  2010年   1175篇
  2009年   1458篇
  2008年   1624篇
  2007年   1549篇
  2006年   1220篇
  2005年   947篇
  2004年   882篇
  2003年   763篇
  2002年   858篇
  2001年   542篇
  2000年   541篇
  1999年   542篇
  1998年   490篇
  1997年   384篇
  1996年   418篇
  1995年   402篇
  1994年   382篇
  1993年   277篇
  1992年   217篇
  1991年   137篇
  1990年   128篇
  1989年   142篇
  1988年   96篇
  1987年   77篇
  1986年   83篇
  1985年   95篇
  1984年   92篇
  1983年   66篇
  1982年   91篇
  1981年   73篇
  1980年   63篇
  1979年   42篇
  1978年   37篇
  1977年   32篇
  1976年   33篇
  1973年   19篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
In this study, the functional interaction of HPLW peptide with VEGFR2 (Vascular Endothelial Growth Factor Receptor 2) was determined by using fast 15N‐edited NMR spectroscopic experiments. To this aim, 15N uniformly labelled HPLW has been added to Porcine Aortic Endothelial Cells. The acquisition of isotope‐edited NMR spectroscopic experiments, including 15N relaxation measurements, allowed a precise characterization of the in‐cell HPLW epitope recognized by VEGFR2.  相似文献   
3.
4.
5.
A general and efficient methodology for the direct transition metal free trifluoromethylthiolation of a broad range of biologically relevant N‐heteroarenes is reported employing abundant sodium chloride as the catalyst. This method is operationally simple, exhibits high functional group tolerance, and does not require protecting groups.  相似文献   
6.
7.
8.
In this paper, an application of the Riquer-Thomas-Janet theory is described for the problem of transforming a system of partial differential equations into a passive form, i.e., to a special form which contains explicitly both the equations of the initial system and all their nontrivial differential consequences. This special representation of a system markedly facilitates the subsequent integration of the corresponding differential equations. In this paper, the modern approach to the indicated problem is presented. This is the approach adopted in the Knuth-Bendix procedure [13] for critical-pair/completion and then Buchberger's algorithm for completion of polynomial ideal bases [13] (or, alternatively, for the construction of Groebner bases for ideals in a differential operator ring [14]). The algorithm of reduction to the passive form for linear system of partial differential equations and its implementation in the algorithmic language REFAL, as well as the capabilities of the corresponding program, are outlined. Examples illustrating the power and efficiency of the system are presented.  相似文献   
9.
In this paper, the influence functions and limiting distributions of the canonical correlations and coefficients based on affine equivariant scatter matrices are developed for elliptically symmetric distributions. General formulas for limiting variances and covariances of the canonical correlations and canonical vectors based on scatter matrices are obtained. Also the use of the so-called shape matrices in canonical analysis is investigated. The scatter and shape matrices based on the affine equivariant Sign Covariance Matrix as well as the Tyler's shape matrix serve as examples. Their finite sample and limiting efficiencies are compared to those of the Minimum Covariance Determinant estimators and S-estimator through theoretical and simulation studies. The theory is illustrated by an example.  相似文献   
10.
In this paper we give a realization of some symmetric space G/K as a closed submanifold P of G. We also give several equivalent representations of the submanifold P. Some properties of the set gKP are also discussed, where gK is a coset space in G.  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