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   176399篇
  免费   574篇
  国内免费   133篇
化学   73568篇
晶体学   2597篇
力学   10415篇
综合类   1篇
数学   32448篇
物理学   58077篇
  2021年   869篇
  2020年   965篇
  2019年   1105篇
  2018年   10332篇
  2017年   11199篇
  2016年   6183篇
  2015年   1851篇
  2014年   1845篇
  2013年   3398篇
  2012年   7266篇
  2011年   15922篇
  2010年   9751篇
  2009年   9887篇
  2008年   13734篇
  2007年   17312篇
  2006年   2964篇
  2005年   9164篇
  2004年   5682篇
  2003年   5624篇
  2002年   3611篇
  2001年   2404篇
  2000年   1963篇
  1999年   1294篇
  1998年   1172篇
  1997年   1054篇
  1996年   1079篇
  1995年   942篇
  1994年   906篇
  1993年   897篇
  1992年   939篇
  1991年   1014篇
  1990年   956篇
  1989年   991篇
  1988年   915篇
  1987年   862篇
  1986年   822篇
  1985年   962篇
  1984年   1074篇
  1983年   920篇
  1982年   931篇
  1981年   843篇
  1980年   797篇
  1979年   882篇
  1978年   997篇
  1977年   937篇
  1976年   869篇
  1975年   815篇
  1974年   832篇
  1973年   847篇
  1972年   591篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
A mixed boundary-value problem for the nonlinear Schrödinger equation and its generalization is studied by the method used for the inverse scattering problem. A connection is established between conservation laws and boundary conditions in integrable boundary-value problems for higher nonlinear Schrödinger equations. It is shown that the generalized boundary-value problem requires a joint consideration of regular and singular solutions for the nonlinear Schrödinger equation with repulsion.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 169, pp. 151–165, 1988.  相似文献   
92.
Preface     
  相似文献   
93.
This paper presents an alternative to the beta continuous probability distribution for risk analysis. Particular attention has been given to two major applications of distributions, namely project management risk and critical path analysis (PERT). In conjunction with the beta, the triangular and normal distributions are frequently employed in order to give sufficient robustness to risk analysis. The beta distribution, as used in PERT, has a major theoretical implementation flaw. The new distribution was developed to give a possible alternative method of assessing risk. It is shown that the requirement to estimate the most pessimistic variate may be replaced by the probability to exceed the mode. Proposals for other simplifications in risk analysis are discussed. Practical means to validate the most appropriate distributions for risk analysis are outlined, and a cost-data case study is included.  相似文献   
94.
95.
Summary The main purpose of this paper is to introduce the concepts of η-sets, ηζ-sets,η-continuity and ηζ-continuity and to obtain a decomposition of continuity.  相似文献   
96.
Electrochemical separation of lead-silver alloys into the constituents by thin-layer electrolysis in molten electrolytes, with bismuth as metal separator, is studied. It is proposed to determine the extent of component recovery by potentiometry.  相似文献   
97.
Formalization for problems of multicriteria decision making under uncertainty is constructed in terms of guaranteed and weak estimates. A relevant definition of the vector maximinimax value is given. Parameterization and approximation of maximum, minimax, and maximinimax values based on the inverse logical convolution are suggested. An application for multicommodity networks is considered. Received: December 13, 2000 / Accepted: August 21, 2001?Published online May 8, 2002  相似文献   
98.
The procedure for calculating the dispersion of the refractive and absorption indices and thickness of an optical film, based on measurements of spectral dependence of the transmittance, is described. The film parameters are calculated using a solution of the approximation problem. The effect of the film model on the calculated values of the refractive and absorption indices is analyzed.  相似文献   
99.
100.
The process of harmonic wave propagation is investigated in a semi-infinite rigidly-clamped elastic layer. An analytic solution of the problem is obtained by the superposition method. The wave field expansion in the form of a normal mode series for a corresponding infinite waveguide is established. According to residue theory, the explicit form of the expansion coefficients is established with physical requirements of the radiation conditions taken into account.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 19, pp. 3–10, 1988.  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