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   48021篇
  免费   1338篇
  国内免费   12篇
化学   28842篇
晶体学   246篇
力学   801篇
综合类   1篇
数学   9037篇
物理学   10444篇
  2023年   339篇
  2022年   287篇
  2021年   471篇
  2020年   674篇
  2019年   625篇
  2018年   966篇
  2017年   885篇
  2016年   1731篇
  2015年   1441篇
  2014年   1405篇
  2013年   3193篇
  2012年   2914篇
  2011年   2717篇
  2010年   1827篇
  2009年   1525篇
  2008年   2394篇
  2007年   2156篇
  2006年   1954篇
  2005年   1984篇
  2004年   1716篇
  2003年   1434篇
  2002年   1255篇
  2001年   976篇
  2000年   983篇
  1999年   678篇
  1998年   541篇
  1997年   453篇
  1996年   599篇
  1995年   434篇
  1994年   510篇
  1993年   464篇
  1992年   488篇
  1991年   415篇
  1990年   459篇
  1989年   374篇
  1988年   399篇
  1987年   349篇
  1986年   342篇
  1985年   483篇
  1984年   443篇
  1983年   344篇
  1982年   344篇
  1981年   358篇
  1980年   305篇
  1979年   296篇
  1978年   295篇
  1977年   298篇
  1976年   312篇
  1974年   287篇
  1973年   282篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Palladium and molybdenum polycrystalline layers (clusters) have been deposited in a stainless steel UHV system onto a layer of alumina (Al2O3). This layer has been prepared by high temperature oxidation of an aluminium layer. The interaction of this system with nitrogen has been investigated at room temperature by an FEM technique. Under these conditions nitrogen spillover from molybdenum to palladium has been observed.  相似文献   
2.
3.
This note shows that a certain toric quotient of the quintic Calabi-Yau threefold in provides a counterexample to a recent conjecture of Cox and Katz concerning nef cones of toric hypersurfaces. Received: 8 February 2001; in final form: 17 September 2001 / Published online: 1 February 2002  相似文献   
4.
5.
Some remarks to problems of point and interval estimation, testing and problems of outliers are presented in the case of multivariate regression model. This work was supported by the Council of Czech Government J14/98:153100011.  相似文献   
6.
Lithium (10–150 ng ml?1) in wine is determined by atomic absorption spectrometry by direct nebulization and after digestion with mixed acids. The results of methods are similar. Thirty-four wines from various Spanish provinces are analysed.  相似文献   
7.
Regioselective demethylation of 3,4-dihydropapaveraldine (2a) at 7 and 3' positions affords a properly substituted diphenolic key intermidiate (2d) for the synthesis of reticuline and N-norreticuline.  相似文献   
8.
A review of ideas leading to full rejection of any finite or partially-infinite order kinetic equation linearized in external field is given on grounds of the time-convolution Generalized Master Equations (GME). By two examples (two-level and band conduction problem), it is shown how standard kinetic equations result from GME in the lowest order approximations which obscure, however, a direct correspondence with the Kubo linear response theory. Without approximations, on the other hand, the rigorous approach is shown to be fully equivalent with the Kubo results. It is argued and illustrated that usual technical simplicity and seeming physical lucidity of standard theories (connected with the presence of field-independent transfer or scattering rates in the fielddependent linearized theory) are just owing to structural features which are solely due to the lowest order approximations involved. These features (i.e. also the possibility of standard physical interpretation of kinetic phenomena) are proved to disappear completely as far as the theory goes properly to higher orders.  相似文献   
9.
Sauer, Shelah, Vapnik and Chervonenkis proved that if a set system on n vertices contains many sets, then the set system has full trace on a large set. Although the restriction on the size of the groundset cannot be lifted, Frankl and Pach found a trace structure that is guaranteed to occur in uniform set systems even if we do not bound the size of the groundset. In this note we shall give three sequences of structures such that every set system consisting of sufficiently many sets contains at least one of these structures with many sets.  相似文献   
10.
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