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   1323844篇
  免费   25747篇
  国内免费   7719篇
化学   655524篇
晶体学   20211篇
力学   74460篇
综合类   104篇
数学   240243篇
物理学   366768篇
  2021年   13535篇
  2020年   15958篇
  2019年   16106篇
  2018年   12384篇
  2016年   27802篇
  2015年   20793篇
  2014年   30466篇
  2013年   74375篇
  2012年   37021篇
  2011年   33173篇
  2010年   36461篇
  2009年   38942篇
  2008年   32642篇
  2007年   28133篇
  2006年   34860篇
  2005年   26978篇
  2004年   28807篇
  2003年   27388篇
  2002年   28495篇
  2001年   27406篇
  2000年   24159篇
  1999年   22203篇
  1998年   20899篇
  1997年   20891篇
  1996年   21043篇
  1995年   19122篇
  1994年   18535篇
  1993年   18100篇
  1992年   17907篇
  1991年   18252篇
  1990年   17440篇
  1989年   17504篇
  1988年   17070篇
  1987年   17056篇
  1986年   15969篇
  1985年   22416篇
  1984年   23680篇
  1983年   19901篇
  1982年   21608篇
  1981年   20838篇
  1980年   20180篇
  1979年   20295篇
  1978年   21636篇
  1977年   21220篇
  1976年   20943篇
  1975年   19644篇
  1974年   19278篇
  1973年   19768篇
  1972年   14274篇
  1967年   12457篇
排序方式: 共有10000条查询结果,搜索用时 15 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