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   7514篇
  免费   155篇
  国内免费   87篇
化学   4654篇
晶体学   85篇
力学   166篇
数学   1716篇
物理学   1135篇
  2020年   69篇
  2019年   63篇
  2018年   84篇
  2017年   50篇
  2016年   142篇
  2015年   105篇
  2014年   126篇
  2013年   414篇
  2012年   326篇
  2011年   369篇
  2010年   234篇
  2009年   202篇
  2008年   334篇
  2007年   336篇
  2006年   401篇
  2005年   383篇
  2004年   337篇
  2003年   279篇
  2002年   297篇
  2001年   92篇
  2000年   80篇
  1999年   87篇
  1998年   105篇
  1997年   104篇
  1996年   146篇
  1995年   90篇
  1994年   84篇
  1993年   78篇
  1992年   88篇
  1991年   80篇
  1990年   69篇
  1989年   66篇
  1988年   58篇
  1987年   73篇
  1986年   61篇
  1985年   107篇
  1984年   122篇
  1983年   87篇
  1982年   94篇
  1981年   120篇
  1980年   131篇
  1979年   97篇
  1978年   109篇
  1977年   80篇
  1976年   92篇
  1975年   106篇
  1974年   100篇
  1973年   97篇
  1972年   51篇
  1971年   43篇
排序方式: 共有7756条查询结果,搜索用时 15 毫秒
31.
It was argued by Schramm and Smirnov that the critical site percolation exploration path on the triangular lattice converges in distribution to the trace of chordal SLE 6. We provide here a detailed proof, which relies on Smirnov’s theorem that crossing probabilities have a conformally invariant scaling limit (given by Cardy’s formula). The version of convergence to SLE 6 that we prove suffices for the Smirnov–Werner derivation of certain critical percolation crossing exponents and for our analysis of the critical percolation full scaling limit as a process of continuum nonsimple loops. Research of Charles M.Newman was partially supported by the US NSF under grants DMS-01-04278 and DMS-06-06696.  相似文献   
32.
Enantioselective biocatalysis in nonaqueous media is becoming increasingly important in preparative synthetic chemistry. This article discusses (1) the general catalytic properties of enzymes in nonaqueous environments, (2) the basic principles that govern lipase-catalyzed enantioselective esterification and transesterification reactions in organic media for the preparation of optically active acids and alcohols, (3) the determination of kinetic and thermodynamic parameters, and (4) the quantitative analysis of published data.  相似文献   
33.
The synthesis of chiral oxazolidinedione derived bicalutamide analogs has been discussed.  相似文献   
34.
The aim of this article is to give a new dynamical proof of the Ferrand–Obata theorem when the manifold is compact. This will give us a generalisation of this theorem to transversally conformal foliations ofcodimension greater than three and constant basic functions.  相似文献   
35.
We consider the M(t)/M(t)/m/m queue, where the arrival rate λ(t) and service rate μ(t) are arbitrary (smooth) functions of time. Letting pn(t) be the probability that n servers are occupied at time t (0≤ nm, t > 0), we study this distribution asymptotically, for m→∞ with a comparably large arrival rate λ(t) = O(m) (with μ(t) = O(1)). We use singular perturbation techniques to solve the forward equation for pn(t) asymptotically. Particular attention is paid to computing the mean number of occupied servers and the blocking probability pm(t). The analysis involves several different space-time ranges, as well as different initial conditions (we assume that at t = 0 exactly n0 servers are occupied, 0≤ n0m). Numerical studies back up the asymptotic analysis. AMS subject classification: 60K25,34E10 Supported in part by NSF grants DMS-99-71656 and DMS-02-02815  相似文献   
36.
CrCl2-mediated condensation of γ-chloro-gem-trichloroalkanes with aldehyde generates homoallylic alcohols through a hydride rearrangement followed by a Nozaki-Hiyama allylation.  相似文献   
37.
Partially supported by NSF grant DMS-8701746  相似文献   
38.
Characterizations of real inner product spaces among a class of metric spaces have been obtained based on homogeneity of metric pythagorean orthogonality, a metrization of the concept of pythagorean orthogonality as defined in normed linear spaces. In the present paper a considerable weakening of this hypothesis is shown to characterize real inner product spaces among complete, convex, externally convex metric spaces, generalizing a result of Kapoor and Prasad [9], and providing a connection with the many characterizations of such spaces using euclidean four point properties.  相似文献   
39.
For a given n-by-n matrix A, we consider the set of matrices which commute with A and all of whose principal submatrices commute with the corresponding principal submatrices of A. The properties of this set are examined, with particular attention to its dimension.  相似文献   
40.
We prove for a large class of tilings that, given a finite tile set, if it is possible to tile Euclideann-space with isometric copies of this set, then there is a tiling with the ‘local isomorphism property’. Research supported in part by NSF Grant No. DMS-9001475.  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