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   104486篇
  免费   2309篇
  国内免费   1679篇
化学   40305篇
晶体学   991篇
力学   8515篇
综合类   105篇
数学   35377篇
物理学   23181篇
  2022年   328篇
  2021年   514篇
  2020年   668篇
  2019年   759篇
  2018年   11065篇
  2017年   10845篇
  2016年   6974篇
  2015年   1536篇
  2014年   1247篇
  2013年   1554篇
  2012年   5145篇
  2011年   11810篇
  2010年   6755篇
  2009年   7055篇
  2008年   7662篇
  2007年   9804篇
  2006年   1089篇
  2005年   2014篇
  2004年   2135篇
  2003年   2605篇
  2002年   1748篇
  2001年   937篇
  2000年   754篇
  1999年   589篇
  1998年   546篇
  1997年   451篇
  1996年   489篇
  1995年   378篇
  1994年   322篇
  1993年   385篇
  1992年   337篇
  1991年   353篇
  1990年   352篇
  1989年   349篇
  1987年   309篇
  1985年   324篇
  1984年   327篇
  1982年   317篇
  1980年   302篇
  1979年   344篇
  1978年   363篇
  1977年   338篇
  1976年   419篇
  1975年   373篇
  1974年   399篇
  1973年   420篇
  1972年   385篇
  1971年   339篇
  1970年   321篇
  1969年   305篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
On the basis of a computer analysis of four classes of toxic polypeptides, generalized primary structures of each class have been obtained which can be used for planning the synthesis of biologically active compounds.  相似文献   
92.
电子束流品质对自由电子激光小信号增益影响的计算   总被引:1,自引:0,他引:1  
对电子束有一定初始能量分散或角度分散时的自由电子激光小信号增益用较简便的方法进行了分析计算,并给出了一个渐近公式,结果与用计算机模拟解自由电子激光微分方程组得到的结果一致。  相似文献   
93.
94.
In this paper we obtain a number of Maharam-type slice integral representations, with respect to scalar measures, for positive projections in Dedekind complete vector lattices and f-algebras. AMS Classification: 47B65, 46A40, 06F25  相似文献   
95.
We calculate the leptonic constant for the pseudoscalar ground state of the B c meson in the framework of a QCD-motivated potential model taking into account the two-loop anomalous dimension for the heavy quark current in nonrelativistic QCD as matched with full QCD.  相似文献   
96.
We define analytic functions within Clifford Algebras CL, and study their trigonometric properties. We write the addition formulas when their arguments, A and B in CL, commute, this generalizes ordinary trigonometry. We examine in particular the case A2 = 1.   相似文献   
97.
In the present paper it is shown that if S1 and S2 are two Clifford topological semigroups satisfying certain conditions and T is an isometric isomorphism of LUC(S1*) onto LUC(S2*), then T maps S1 topologically isomorphically onto S2. Furthermore, T maps M l n(S1) (M(S1), respectively) isometrically isomorphically onto M l n(S2) (M(S2), respectively). Indeed, we have obtained a generalization of a well-known result of Ghahramani, Lau and Losert for locally compact groups to a more general setting of Clifford topological semigroups.  相似文献   
98.

The accuracy of determination of the optical constants of smooth copper surfaces produced by different technologies is analyzed, with particular attention paid to the consideration of the influence of scattered radiation (which is ignored by many authors) on the retrieval of the optical constants of copper surfaces from reflected radiation. The neglect of scattered radiation can lead to errors as high as 50% in determining the optical constants for bulk copper. For thin films, the errors are much lower. The influence of surface oxidation during measurements in air and surface features of studied objects on the parameters to be determined is analyzed as well. It is shown that errors in determination of the constants are maximal in the plasma resonance region of copper.

  相似文献   
99.
This paper describes some work carried out in the Scientific Research and Development Branch (SRDB) of the Home Office, intended to contribute to an overall aim of building up internal expertise in the field of expert systems. This was done by carrying out a number of pilot and demonstrator projects, two of which are described in some detail. The plan, which proved successful, was to build as far as possible on the relevant skills already possessed by an OR group in the branch. The lessons learned from these are summarized in the hope that they will be of use to other groups who wish to become involved in this important area.  相似文献   
100.
Frank Jackson and Philip Pettit have defended a non-reductive account of causal relevance known as the ‘program explanation account’. Allegedly, irreducible mental properties can be causally relevant in virtue of figuring in non-redundant program explanations which convey information not conveyed by explanations in terms of the physical properties that actually do the ‘causal work’. I argue that none of the possible ways to spell out the intuitively plausible idea of a program explanation serves its purpose, viz., defends non-reductive physicalism against Jaegwon Kim’s Causal Exclusion Argument according to which non-reductive physicalism is committed to epiphenomenalism because irreducible mental properties are ‘screened off’ from causal relevance by their physical realizers. Jackson and Pettit’s most promising explication of a program explanation appeals to the idea of invariance of effect under variation of realization, but I show that invariance of effect under variation of realization is neither necessary nor sufficient for causal relevance.  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