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   1399374篇
  免费   25829篇
  国内免费   7790篇
化学   708686篇
晶体学   20470篇
力学   75472篇
综合类   106篇
数学   245252篇
物理学   383007篇
  2021年   13525篇
  2020年   15948篇
  2019年   16094篇
  2018年   13419篇
  2016年   28251篇
  2015年   20963篇
  2014年   30532篇
  2013年   74597篇
  2012年   41251篇
  2011年   40130篇
  2010年   38563篇
  2009年   40336篇
  2008年   38884篇
  2007年   35120篇
  2006年   40408篇
  2005年   33026篇
  2004年   33388篇
  2003年   31031篇
  2002年   31894篇
  2001年   31511篇
  2000年   26830篇
  1999年   23511篇
  1998年   21451篇
  1997年   21350篇
  1996年   21294篇
  1995年   19306篇
  1994年   18747篇
  1993年   18315篇
  1992年   18606篇
  1991年   18860篇
  1990年   18062篇
  1989年   18023篇
  1988年   17648篇
  1987年   17530篇
  1986年   16524篇
  1985年   22914篇
  1984年   24043篇
  1983年   20147篇
  1982年   21821篇
  1981年   21016篇
  1980年   20357篇
  1979年   20655篇
  1978年   21881篇
  1977年   21500篇
  1976年   21276篇
  1975年   20050篇
  1974年   19718篇
  1973年   20231篇
  1972年   14675篇
  1967年   12822篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
53.
54.
The Weierstrass nowhere differentiable function, and functions constructed from similar infinite series, have been studied often as examples of functions whose graph is a fractal. Though there is a simple formula for the Hausdorff dimension of the graph which is widely accepted, it has not been rigorously proved to hold. We prove that if arbitrary phases are included in each term of the summation for the Weierstrass function, the Hausdorff dimension of the graph of the function has the conjectured value for almost every sequence of phases. The argument extends to a much wider class of Weierstrass-like functions.

  相似文献   

55.
NaY zeolite samples loaded with sodium metal by vapor phase deposition have been investigated using129Xe NMR spectroscopy. At low sodium concentration, the129Xe NMR spectrum showed three resonance lines which clearly indicate the existence of distinct domains in the zeolite sample. Such an observation suggests that the diffusion of the xenon atoms into each domain only occurs with respect to the NMR time scale (2.9 ms). As the sodium concentration increases, observation of a single broad line indicate a macroscopic homogenization of the system. The shift of this line is explained in part due to a paramagnetic interaction between the xenon atoms and the unpaired electrons of particles containing an odd number of sodium atoms. The linewidth is due to the distribution of the local magnetic fields partially averaged by the rapid motion of the xenon atoms and to the statistical distribution of the sodium particles in the supercage cavities. The paramagnetic interaction vanishes with the oxidation of the sample leading to a narrowing and a shift of the line to higher magnetic fields.  相似文献   
56.
The Thoms effect observed with water-soluble cationic copolymer of acrylamide was studied in relation to the concentration, molecular weight, and molecular weight polydispersity of the polymeric additive, with its composition and composition polydispersity being constant.  相似文献   
57.
    
  相似文献   
58.
We prove a character formula for any finite-dimensional irreducible representationV of the “queer” Lie superalgebra g=q(n). It expresses chV in terms of the multiplicities of the irreducible g-subquotients of the cohomology groups of certain dominant g-bundles on the Π-symmetric projective spaces (i.e., on the homogeneous superspacesG/P whose reduced space is a projective space, whereG=Q(n)). We also establish recurrent relations for the above multiplicities, and this enables us to compute explicitly chV for any givenV. This provides a complete solution to the Kac character problem for the Lie superalgebraq(n). Finally, we consider the particular cases ofq(2), q(3), andq(4) in which we compare the new character formula with the generic character formula of [12]. Translated from Itogi Nauki i Tekhniki, Seriya Sovremennaya Matematika i Ee Prilozheniya. Tematicheskie Obzory. Vol. 41, Algebraic Geometry-7, 1997.  相似文献   
59.
An explicit way for producing invariants for 6-valent graphs with rigid vertices within the framework of Kauffman's approach to graph invariants is presented. These invariants can be used to detect the chirality of a 6-valent graph with rigid vertices. A relevant example is considered. Bibliography: 19 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 223, 1995, pp. 251–262. Translated by A. M. Nikitin  相似文献   
60.
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