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   1361445篇
  免费   26057篇
  国内免费   7867篇
化学   677626篇
晶体学   20505篇
力学   75277篇
综合类   117篇
数学   243996篇
物理学   377848篇
  2021年   13615篇
  2020年   16018篇
  2019年   16166篇
  2018年   13924篇
  2016年   28665篇
  2015年   21065篇
  2014年   30713篇
  2013年   74717篇
  2012年   39093篇
  2011年   36876篇
  2010年   38105篇
  2009年   40361篇
  2008年   35605篇
  2007年   31646篇
  2006年   36466篇
  2005年   29453篇
  2004年   30484篇
  2003年   28544篇
  2002年   29444篇
  2001年   29182篇
  2000年   25078篇
  1999年   22715篇
  1998年   21173篇
  1997年   21208篇
  1996年   21219篇
  1995年   19277篇
  1994年   18729篇
  1993年   18249篇
  1992年   18315篇
  1991年   18551篇
  1990年   17744篇
  1989年   17816篇
  1988年   17360篇
  1987年   17352篇
  1986年   16298篇
  1985年   22714篇
  1984年   23904篇
  1983年   20069篇
  1982年   21726篇
  1981年   20941篇
  1980年   20285篇
  1979年   20524篇
  1978年   21764篇
  1977年   21378篇
  1976年   21068篇
  1975年   19742篇
  1974年   19380篇
  1973年   19834篇
  1972年   14311篇
  1967年   12558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