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   40571篇
  免费   1422篇
  国内免费   142篇
化学   21392篇
晶体学   218篇
力学   1107篇
综合类   5篇
数学   6890篇
物理学   12523篇
  2023年   256篇
  2021年   347篇
  2020年   510篇
  2019年   410篇
  2018年   538篇
  2017年   531篇
  2016年   1107篇
  2015年   833篇
  2014年   950篇
  2013年   2017篇
  2012年   1843篇
  2011年   2005篇
  2010年   1358篇
  2009年   1142篇
  2008年   1871篇
  2007年   1759篇
  2006年   1656篇
  2005年   1507篇
  2004年   1310篇
  2003年   1056篇
  2002年   921篇
  2001年   863篇
  2000年   712篇
  1999年   503篇
  1998年   439篇
  1997年   436篇
  1996年   532篇
  1995年   478篇
  1994年   501篇
  1993年   512篇
  1992年   565篇
  1991年   386篇
  1990年   397篇
  1989年   365篇
  1988年   334篇
  1987年   356篇
  1986年   322篇
  1985年   520篇
  1984年   499篇
  1983年   421篇
  1982年   437篇
  1981年   431篇
  1980年   424篇
  1979年   406篇
  1978年   404篇
  1977年   399篇
  1976年   368篇
  1975年   364篇
  1974年   352篇
  1973年   296篇
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
101.
Montgomery and Vaughan improved a theorem of Erd?s and Fuchs for an arbitrary sequence. Sárközy extended this theorem of Erd?s and Fuchs for two arbitrary sequences which are "near" in a certain sense. Using the idea of Jurkat (differentiation of the generating function), we will extend similarly the result of Montgomery and Vaughan for "sufficiently near" sequences.  相似文献   
102.
The aim of this paper is to give decompositions of some weaker forms of continuity using the concepts of classes B 1, B 2, B 3, αA and αC introduced by ourselves.  相似文献   
103.
The crystal structure of 1-[3-(3,4-dimethoxyphenyl)-2-propenoyl]pyrrolidine (C15H19NO3) (I) has been determined by X-ray analysis. It crystallizes orthorhombic space group Pbca with a = 24.295(3), b = 15.086(3), c = 7.552(3)A, V = 2768(1)A3, Z = 8, Dcalc = 1.254 g/cm3, mu = (Mo K(alpha)) = 0.87 cm(-1). The title compound has analgesic activity of cycloaliphatic amine part. The molecule is deviated from planar configuration.  相似文献   
104.
Charge density fluctuation of low frequency in a dusty plasma   总被引:2,自引:0,他引:2  
The charge density fluctuation of low frequency in a dusty plasma, which is derived from the longitudinal dielectric permittivity of the dusty plasma, has been studied by kinetic theory. The results show that theP value, which describes the relative charge density on the dust in the plasma, and the charging frequency of a dust particle Ω c , which describes the ratio of charge changing of the dust particles, determine the character of the charge density fluctuation of low frequency. For a dusty plasma ofP≪1, when the charging frequency Ω c , is much smaller than the dusty plasma frequency ωd, there is a strong charge density fluctuation which is of character of dust acoustic eigenwave. For a dusty plasma ofP≫1, when the frequency Ω c , is much larger than ω d there are weaker fluctuations with a wide spectrum. The results have been applied to the ionosphere and the range of radius and density of dust particles is found, where a strong charge density fluctuation of low frequency should exist.  相似文献   
105.
The dependence of cross sections on the colour state of the colliding hadrons is investigated within the Low-Nussinov model of two-gluon exchange. The total cross sections for colour-octet hadrons are practically constant as functions of the hadronic radii, while they tend to zero when the radii of the colour-singlet hadrons approach zero. The slope parameter of the differential clastic cross sections for small momentum transfers is rather insensitive to the colour structure of the colliding hadrons. The integrated colour exchange cross section is calculated.  相似文献   
106.
107.
High-spin states in196Pb have been populated using the reaction170Er(30Si,4n). The previously observed shears bands in this nucleus have been extended and some of their transitions have been reordered. They now form regular bands with band crossings. One of the bands splits into two pathways at high spin.  相似文献   
108.
109.
110.
Rotationally symmetric deformations of a flat annular elastic membrane under a gravitational force are studied, with prescribed radial stresses or horizontal displacements at the edges. The small-finitedeflection theory of Föppl-Hencky as well as a simplified version of Reissner's static first approximation theory of thin shells of revolution are applied which lead to consider a single, second-order, ordinary differential equation for the derivation of the principal stresses in the membrane. Using analytical methods, the range of those boundary data is determined for which the solutions of the differential equation are wrinkle free in the sense that both the radial and the circumferential stress components are nonnegative everywhere.  相似文献   
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