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   6875篇
  免费   368篇
  国内免费   659篇
化学   1187篇
晶体学   16篇
力学   129篇
综合类   51篇
数学   5078篇
物理学   928篇
无线电   513篇
  2024年   5篇
  2023年   88篇
  2022年   75篇
  2021年   83篇
  2020年   134篇
  2019年   159篇
  2018年   160篇
  2017年   164篇
  2016年   196篇
  2015年   180篇
  2014年   340篇
  2013年   594篇
  2012年   292篇
  2011年   401篇
  2010年   304篇
  2009年   499篇
  2008年   523篇
  2007年   472篇
  2006年   421篇
  2005年   357篇
  2004年   290篇
  2003年   299篇
  2002年   264篇
  2001年   188篇
  2000年   180篇
  1999年   196篇
  1998年   173篇
  1997年   186篇
  1996年   97篇
  1995年   82篇
  1994年   71篇
  1993年   53篇
  1992年   36篇
  1991年   38篇
  1990年   29篇
  1989年   21篇
  1988年   9篇
  1987年   16篇
  1986年   12篇
  1985年   22篇
  1984年   18篇
  1983年   8篇
  1982年   30篇
  1981年   24篇
  1980年   23篇
  1979年   28篇
  1978年   18篇
  1977年   14篇
  1976年   11篇
  1974年   5篇
排序方式: 共有7902条查询结果,搜索用时 0 毫秒
71.
One from the most important properties of accretive and monotone operators is the existence of zeros and surjectivity. In the paper we introduce relaxed variants of dissipative, accretive and monotone operators. Using essentially the properties of the solution set of appropriate differential inclusions we study the existence of zeros of such operators. As corollaries the existence of fixed points of relaxed contractive and relaxed nonexpansive multifunctions are obtained.  相似文献   
72.
73.
Twenty alloys of various compositions in the Cu2Se-Al2Se3 system were prepared and investigated. The T(x) phase diagram of the Cu2Se-Al2Se3 system was obtained from x-ray diffraction, differential thermal analysis, and microstructure investigation for the first time. The homogeneity region of the CuAlSe2 semiconducting compound was established. Previous articles by this author were presented with the spelling of his name as B.V. Korzun.  相似文献   
74.
We modify Szász-Durrmeyer operators by means of three-diagonal generalized matrix which overcomes a difficulty in extending a Berens-Lorentz result to the Szász-Durrmeyer operators for second order of smoothness. The direct and converse theorems for these operators inL p are also presented by Ditzian-Totik modulus of smoothness.This project is supported by Zhejiang Provincial Foundation of China.  相似文献   
75.
76.
王勤 《数学杂志》1997,17(4):468-472
记X为复数域上无限维Banach空间,H为无限维复可分Hilert空间。本文给出B(X)上保持点谱的满射可加射具有的形式,以及B(H)上某些初等算子保点谱的充要条件。  相似文献   
77.
We construct the spaces that the elliptic Ruijsenaars operators act on. It is shown that they are extensible to nonnegative selfadjoint operators on a space of square integrable functions, or preserve a finite dimensional vector space of entire functions. These facts are shown in terms of the R-operators which satisfy the Yang–lBaxter equation. The elliptic Ruijsenaars operators are considered as the elliptic analogues of the Macdonald operators or the difference analogues of the Lamé operators.  相似文献   
78.
In this paper, we investigate strict stability of differential systems by variational Lyapunov function. We obtain some sufficient conditions and comparison theorems.  相似文献   
79.
In this paper, by means of monotone iterative technique, a necessary and sufficient condition of the existence of positive solution for a class of nonlinear singular differential system is established, the results of the existence and uniqueness of the positive solution and the iterative sequence of solution are given. In the end, two classes extending boundary value differential systems are discussed and some further results are obtained.  相似文献   
80.
Working in a given conformal class, we prove existence of constant Q-curvature metrics on compact manifolds of arbitrary dimension under generic assumptions. The problem is equivalent to solving a nth-order non-linear elliptic differential (or integral) equation with variational structure, where n is the dimension of the manifold. Since the corresponding Euler functional is in general unbounded from above and below, we use critical point theory, jointly with a compactness result for the above equation.  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