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   1339389篇
  免费   25851篇
  国内免费   7785篇
化学   666187篇
晶体学   20244篇
力学   74627篇
综合类   102篇
数学   242144篇
物理学   369721篇
  2021年   13600篇
  2020年   16020篇
  2019年   16170篇
  2018年   12436篇
  2016年   27987篇
  2015年   20910篇
  2014年   30638篇
  2013年   74695篇
  2012年   37976篇
  2011年   34535篇
  2010年   37009篇
  2009年   39384篇
  2008年   33928篇
  2007年   29307篇
  2006年   36049篇
  2005年   28341篇
  2004年   29738篇
  2003年   28045篇
  2002年   29248篇
  2001年   27737篇
  2000年   24439篇
  1999年   22455篇
  1998年   21077篇
  1997年   21086篇
  1996年   21226篇
  1995年   19336篇
  1994年   18763篇
  1993年   18325篇
  1992年   18101篇
  1991年   18434篇
  1990年   17587篇
  1989年   17625篇
  1988年   17155篇
  1987年   17163篇
  1986年   16048篇
  1985年   22550篇
  1984年   23775篇
  1983年   19968篇
  1982年   21697篇
  1981年   20895篇
  1980年   20228篇
  1979年   20366篇
  1978年   21680篇
  1977年   21272篇
  1976年   20991篇
  1975年   19637篇
  1974年   19285篇
  1973年   19751篇
  1972年   14277篇
  1967年   12470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