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   34134篇
  免费   222篇
  国内免费   316篇
化学   13716篇
晶体学   282篇
力学   1569篇
综合类   12篇
数学   10180篇
物理学   8913篇
  2021年   68篇
  2020年   80篇
  2019年   76篇
  2018年   1240篇
  2017年   1485篇
  2016年   791篇
  2015年   650篇
  2014年   586篇
  2013年   930篇
  2012年   3371篇
  2011年   2578篇
  2010年   1990篇
  2009年   1717篇
  2008年   823篇
  2007年   885篇
  2006年   866篇
  2005年   4673篇
  2004年   4139篇
  2003年   2488篇
  2002年   672篇
  2001年   376篇
  2000年   174篇
  1999年   265篇
  1998年   179篇
  1997年   131篇
  1996年   131篇
  1995年   105篇
  1994年   114篇
  1993年   101篇
  1992年   230篇
  1991年   192篇
  1990年   206篇
  1989年   153篇
  1988年   142篇
  1987年   105篇
  1986年   84篇
  1985年   102篇
  1984年   108篇
  1983年   72篇
  1982年   94篇
  1981年   95篇
  1980年   103篇
  1979年   103篇
  1978年   102篇
  1977年   93篇
  1976年   149篇
  1975年   88篇
  1974年   78篇
  1973年   106篇
  1972年   54篇
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
71.
The invariance of the geometric mean G with respect to the Lagrangian mean-type mapping (Lf,Lg), i.e. the equation G○(Lf,Lg)=G, is considered. We show that the functions f and g must be of high class regularity. This fact allows to reduce the problem to a differential equation and determine the second derivatives of the generators f and g.  相似文献   
72.
In the paper we indicate an error made in the proof of the main result of the paper [M.A. Darwish, On quadratic integral equation of fractional orders, J. Math. Anal. Appl. 311 (2005) 112-119]. Moreover, we provide correct proof of a slightly modified version of the mentioned result. The main tool used in our proof is the technique associated with the Hausdorff measure of noncompactness.  相似文献   
73.
In this paper we deal with nonlinear second-order boundary value problems with impulses. The impulsive functions depend implicitly on the different considered variables and the boundary value conditions are nonlinear. In both cases functional dependence on the solution is allowed. The existence results follow from the existence of a pair of well-ordered lower and upper solutions.  相似文献   
74.
We study linear dynamical systems with multidimensional time in Banach spaces. Using Taylor functional calculus we prove that under additional assumptions hyperbolic systems have shadowing property.  相似文献   
75.
In this work was presented an application of the use of task specific onium salts (TSOSs) as soluble supports in Grieco’s multicomponent synthesis of tetrahydroquinolines. These soluble supports are of wide applicability and combine advantages of solid phase synthesis without its limitations with those of solution phase chemistry. After a simple washing step, products were cleaved from the supports and obtained in pure form and good yields.  相似文献   
76.
A Fubini theorem     
Let I0 be the σ-ideal of subsets of a Polish group generated by Borel sets which have perfectly many pairwise disjoint translates. We prove that a Fubini-type theorem holds between I0 and the σ-ideals of Haar measure zero sets and of meager sets. We use this result to give a simple proof of a generalization of a theorem of Balcerzak-Ros?anowski-Shelah stating that I0 on N2 strongly violates the countable chain condition.  相似文献   
77.
78.
The ion-beam-assisted etching of silicon in Cl2 environment is considered. The theoretically calculated dependences of silicon etching rate on the flux of Cl2 molecules at different ion current densities are compared with experimentally measured. The composition of the adsorbed layer is determined. It is found that SiCl2 molecules prevail in the adsorbed layer. The reciprocal of relative concentration of SiCl2 molecules in the adsorbed layer linearly depends on the ion-to-neutral flux ratio.  相似文献   
79.
We derive a fourth-order compact finite difference scheme for a two-dimensional elliptic problem with a mixed derivative and constant coefficients. We conduct experimental study on numerical solution of the problem discretized by the present compact scheme and the traditional second-order central difference scheme. We study the computed accuracy achieved by each scheme and the performance of the Gauss-Seidel iterative method, the preconditioned GMRES iterative method, and the multigrid method, for solving linear systems arising from the difference schemes.  相似文献   
80.
We study continuum and atomistic models for the elastodynamics of crystalline solids at zerotemperature.We establish sharp criterion for the regime of validity of the nonlinear elastic wave equationsderived from the well-known Cauchy-Born rule.  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