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   561922篇
  免费   3576篇
  国内免费   1182篇
化学   264927篇
晶体学   8227篇
力学   30665篇
综合类   5篇
数学   84377篇
物理学   178479篇
  2020年   4724篇
  2019年   5697篇
  2018年   12817篇
  2017年   13206篇
  2016年   13223篇
  2015年   6061篇
  2014年   9948篇
  2013年   21713篇
  2012年   19368篇
  2011年   27600篇
  2010年   19416篇
  2009年   19586篇
  2008年   25178篇
  2007年   27273篇
  2006年   17113篇
  2005年   18516篇
  2004年   15891篇
  2003年   15034篇
  2002年   14058篇
  2001年   13829篇
  2000年   10943篇
  1999年   8151篇
  1998年   7330篇
  1997年   7218篇
  1996年   6752篇
  1995年   6125篇
  1994年   6061篇
  1993年   6080篇
  1992年   6362篇
  1991年   6738篇
  1990年   6582篇
  1989年   6547篇
  1988年   6376篇
  1987年   6336篇
  1986年   5927篇
  1985年   7493篇
  1984年   7860篇
  1983年   6605篇
  1982年   7110篇
  1981年   6682篇
  1980年   6364篇
  1979年   6902篇
  1978年   7189篇
  1977年   7085篇
  1976年   7417篇
  1975年   6720篇
  1974年   6740篇
  1973年   7194篇
  1972年   5284篇
  1971年   4466篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Estimates of a rate of convergence of orderO(n –1) are obtained for integral functionals of an empirical process.Translated fromTeoriya Sluchainykh Protsessov, Vol. 15, pp. 10–16, 1987.  相似文献   
62.
Translated fromProblemy Ustoichivosti Stokhasticheskikh Modelei. Trudy Seminara, 1988, pp. 84–92.  相似文献   
63.
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   
64.
Using an integral theory of grating diffraction we calculate efficiencies greater than 100% if a coating with gain is taken into account. A connection with guided modes is conjectured. The application in optical computing seems to be possible.  相似文献   
65.
Physics and Mathematics Division with Computational Center of the Bashkir Branch of the USSR Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 80, No. 3, pp. 470–473, September, 1989.  相似文献   
66.
In this paper, an application of the Riquer-Thomas-Janet theory is described for the problem of transforming a system of partial differential equations into a passive form, i.e., to a special form which contains explicitly both the equations of the initial system and all their nontrivial differential consequences. This special representation of a system markedly facilitates the subsequent integration of the corresponding differential equations. In this paper, the modern approach to the indicated problem is presented. This is the approach adopted in the Knuth-Bendix procedure [13] for critical-pair/completion and then Buchberger's algorithm for completion of polynomial ideal bases [13] (or, alternatively, for the construction of Groebner bases for ideals in a differential operator ring [14]). The algorithm of reduction to the passive form for linear system of partial differential equations and its implementation in the algorithmic language REFAL, as well as the capabilities of the corresponding program, are outlined. Examples illustrating the power and efficiency of the system are presented.  相似文献   
67.
68.
In this paper, the authors studied certain properties of the estimate of Liang and Krishnaiah (1985, J. Multivariate Anal. 16, 162–172) for multivariate binary density. An alternative shrinkage estimate is also obtained. The above results are generalized to general orthonormal systems.  相似文献   
69.
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   
70.
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