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   103542篇
  免费   27679篇
  国内免费   25194篇
化学   68333篇
晶体学   1961篇
力学   6785篇
综合类   1130篇
数学   13512篇
物理学   64694篇
  2024年   534篇
  2023年   1024篇
  2022年   1739篇
  2021年   1634篇
  2020年   1892篇
  2019年   2384篇
  2018年   2214篇
  2017年   3306篇
  2016年   3186篇
  2015年   3682篇
  2014年   3938篇
  2013年   6015篇
  2012年   6543篇
  2011年   8311篇
  2010年   11522篇
  2009年   11743篇
  2008年   6003篇
  2007年   5179篇
  2006年   4800篇
  2005年   4821篇
  2004年   5228篇
  2003年   4107篇
  2002年   3941篇
  2001年   4235篇
  2000年   3424篇
  1999年   3193篇
  1998年   2535篇
  1997年   2222篇
  1996年   2550篇
  1995年   2966篇
  1994年   3013篇
  1993年   3029篇
  1992年   2627篇
  1991年   2228篇
  1990年   1909篇
  1989年   1961篇
  1988年   1946篇
  1987年   1237篇
  1986年   1270篇
  1985年   920篇
  1984年   1048篇
  1982年   933篇
  1981年   764篇
  1980年   787篇
  1979年   560篇
  1978年   544篇
  1977年   637篇
  1976年   1045篇
  1973年   439篇
  1972年   532篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
The notion of Kuratowski convergence is applied to describe a kind of convergence in the context of holomorphic functions. We associate it to a convenient topology, explore its relation with the compact-open topology, thus providing a new set theoretic point of view of this classic topology, and present it in the framework of set-valued mappings.  相似文献   
102.
We consider a spinning charge coupled to the Maxwell field. Through the appropriate symmetry in the initial conditions the charge remains at rest. We establish that any time-dependent finite energy solution converges to a sum of a soliton wave and an outgoing free wave. The convergence holds in global energy norm. Under a small constant external magnetic field the soliton manifold is stable in local energy seminorms and the evolution of the angular velocity is guided by an effective finite-dimensional dynamics. The proof uses a non-autonomous integral inequality method.  相似文献   
103.
104.
We give a Gray code and constant average time generating algorithm for derangements, i.e., permutations with no fixed points. In our Gray code, each derangement is transformed into its successor either via one or two transpositions or a rotation of three elements. We generalize these results to permutations with number of fixed points bounded between two constants.  相似文献   
105.
We prove here that the surface of the regular icosahedron can be triangulated with 8 non-obtuse and with 12 acute triangles. We also show these numbers to be smallest possible.  相似文献   
106.
The extensive study of metric spaces and their embeddings has so far focused on embeddings that preserve pairwise distances. A very intriguing concept introduced by Feige allows us to quantify the extent to which larger structures are preserved by a given embedding. We investigate this concept, focusing on several major graph families such as paths, trees, cubes, and expanders. We find some similarities to the regular (pairwise) distortion, as well as some striking differences.  相似文献   
107.
An overview of the use of non-protein amino acids in the design of conformationally well-defined peptides, based on work from the author’s laboratory, is discussed. The crystal structures of several designed oligopeptides illustrate the useα-aminoisobutyric acid (Aib) in the construction of helices, D-amino acids in the design of helix termination segments andDPro-Xxx segments for nucleating ofβ-hairpin structures.β- andγ-amino acid residues have been used to expand the range of designed polypeptide structures. Dedicated to Professor C N R Rao on his 70th birthday  相似文献   
108.
The paper discusses the relationship between weights and control vertices of two rational NURBS curves of degree two or three with all weights larger than zero when they represent the same curve parametrically and geometrically, and gives sufficient and necessary conditions for coincidence of two rational NURBS curves in non-degeneracy case.  相似文献   
109.
Let Cld AW (X) be the hyperspace of nonempty closed subsets of a normed linear space X with the Attouch–Wets topology. It is shown that the space Cld AW (X) and its various subspaces are AR's. Moreover, if X is an infinite-dimensional Banach space with weight w(X) then Cld AW (X) is homeomorphic to a Hilbert space with weight 2 w(X).  相似文献   
110.
An investigation on nonconnectedness of numerical range for monic matrix polynomials L(λ) is undertaking here. The distribution of eigenvalues of L(λ) to the components of numerical range and some other algebraic properties are also presented.  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