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   1266091篇
  免费   25608篇
  国内免费   7661篇
化学   620916篇
晶体学   19912篇
力学   73328篇
综合类   101篇
数学   236637篇
物理学   348466篇
  2021年   13432篇
  2020年   15853篇
  2019年   15982篇
  2016年   26877篇
  2015年   20444篇
  2014年   30220篇
  2013年   74019篇
  2012年   33873篇
  2011年   27624篇
  2010年   34570篇
  2009年   37623篇
  2008年   28119篇
  2007年   22865篇
  2006年   31385篇
  2005年   22683篇
  2004年   25334篇
  2003年   24737篇
  2002年   26331篇
  2001年   24066篇
  2000年   22113篇
  1999年   21268篇
  1998年   20530篇
  1997年   20593篇
  1996年   20874篇
  1995年   19011篇
  1994年   18427篇
  1993年   17956篇
  1992年   17454篇
  1991年   17802篇
  1990年   17033篇
  1989年   17145篇
  1988年   16684篇
  1987年   16733篇
  1986年   15612篇
  1985年   22095篇
  1984年   23481篇
  1983年   19753篇
  1982年   21504篇
  1981年   20753篇
  1980年   20084篇
  1979年   20087篇
  1978年   21507篇
  1977年   21057篇
  1976年   20718篇
  1975年   19384篇
  1974年   19017篇
  1973年   19492篇
  1972年   14015篇
  1968年   11889篇
  1967年   12269篇
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
31.
32.
33.
Investigated is the dependency of the crack tip opening displacement (CTOD) on the local microstructure of the heat affected zone in high-strength low-alloy (HSLA) microalloyed steel. Since the initiation of the crack tip location could not be controlled in fatigue, any possible correlation between heat iput in welding and fracture toughness could be smeared. Modified CTOD data are defined; they show that the fracture resistance of the weld joint decreased as the heat input increased.  相似文献   
34.
In this paper the notion of pre gs-closed functions is introduced and investigated. Presemiclosed functions are pre gs-closed but not conversely. It is shown that s-normality is preserved under continuous pre gs-closed surjections.  相似文献   
35.
Experimental data on the effect of thallium and sodium impurities on the lattice heat conductivity of PbTe at room temperature are reported. Because the lattice of lead chalcogenides is strongly polarized near charged impurities, the effect of impurities on the lattice heat conductivity depends substantially on their charge state. This property of the material has been used to determine the charge state of the thallium impurity in PbTe. The results obtained argue for a model of quasi-local thallium-impurity states which assumes low electron-correlation energy at an impurity center. Fiz. Tverd. Tela (St. Petersburg) 40, 1206–1208 (July 1998)  相似文献   
36.
The lidar equation for the vibrational backscattering of neodymium laser radiation and its harmonics by hydrogen molecules is solved numerically. Inclined paths in the atmosphere are investigated with the aim of selecting the transmitter wavelength for detecting the lowest concentrations of hydrogen. Zh. Tekh. Fiz. 68, 20–22 (January 1998)  相似文献   
37.
Ideas previously enunciated by the author about the physical interpretation of curvilinear space with torsion are developed. With the new equations describing the eigenstates of such a space, the static centrosymmetric solution for gravitational and electric fields can be made consistent with the Newton and Coulomb laws. The asymptotic behavior of the axisymmetric solution at infinity is studied. The gyromagnetic ratio obtained is characteristic of the electron. Ural State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, p. 56–60, May, 1998.  相似文献   
38.
The electrostatic problem for a thin, unclosed spherical shell and a torus is reduced to paired summation equations in the Legendre polynomials by means of formulas relating the spherical and toroidal harmonic functions. The paired equations are transformed to a Fredholm integral equation of the second kind. Formulas are obtained for computing the charges of the conductors in the form of a series in a small parameter. The capacitance is computed for certain geometrical parameters of the conductors. Zh. Tekh. Fiz. 68, 1–6 (July 1998)  相似文献   
39.
Ordinary cohomologies in an algebra most often exhibit themselves either as objects that describe extensions (of algebras, groups, or modules) or as subjects hindering the existence of algebraic constructions. We introduce the notion of nonlinear cohomologies at a level of cochain complexes, furnish particular examples for Lie algebras, and give an interpretation of first nonlinear cohomologies in terms of “quasiextensions” of orthogonal modules. Translated fromAlgebra i Logika, Vol. 37, No. 5, pp. 522–541, September–October, 1998.  相似文献   
40.
The barotropic compressible Navier–Stokes equations in an unbounded domain are studied. We prove the unique existence of the solution (u, p) of the system (1.1) in the Sobolev spaceHk + 3 × Hk + 2provided that the derivatives of the data of the problem are sufficiently small, wherek ≥ 0 is any integer. The proof follows from an analysis of the linearized problem, the solvability of the continuity equation, and the Schauder fixed point theory. Similar smoothness results are obtained for a linearized form of (1.1).  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