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   1325335篇
  免费   25694篇
  国内免费   7706篇
化学   656669篇
晶体学   20207篇
力学   74374篇
综合类   104篇
数学   240260篇
物理学   367121篇
  2021年   13486篇
  2020年   15904篇
  2019年   16064篇
  2018年   12328篇
  2016年   27740篇
  2015年   20728篇
  2014年   30377篇
  2013年   74250篇
  2012年   37188篇
  2011年   33459篇
  2010年   36472篇
  2009年   38892篇
  2008年   32858篇
  2007年   28382篇
  2006年   35130篇
  2005年   27227篇
  2004年   28983篇
  2003年   27546篇
  2002年   28605篇
  2001年   27409篇
  2000年   24167篇
  1999年   22204篇
  1998年   20902篇
  1997年   20890篇
  1996年   21067篇
  1995年   19146篇
  1994年   18551篇
  1993年   18123篇
  1992年   17927篇
  1991年   18260篇
  1990年   17454篇
  1989年   17515篇
  1988年   17074篇
  1987年   17059篇
  1986年   15970篇
  1985年   22418篇
  1984年   23679篇
  1983年   19902篇
  1982年   21609篇
  1981年   20839篇
  1980年   20181篇
  1979年   20296篇
  1978年   21637篇
  1977年   21222篇
  1976年   20943篇
  1975年   19644篇
  1974年   19278篇
  1973年   19769篇
  1972年   14277篇
  1967年   12456篇
排序方式: 共有10000条查询结果,搜索用时 7 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