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   1404460篇
  免费   32240篇
  国内免费   9045篇
化学   713264篇
晶体学   20338篇
力学   76395篇
综合类   113篇
数学   247777篇
物理学   387858篇
  2021年   13568篇
  2020年   16740篇
  2019年   17742篇
  2018年   16038篇
  2017年   14913篇
  2016年   30286篇
  2015年   22205篇
  2014年   31610篇
  2013年   75901篇
  2012年   41957篇
  2011年   42017篇
  2010年   40894篇
  2009年   42928篇
  2008年   40851篇
  2007年   37130篇
  2006年   39186篇
  2005年   34316篇
  2004年   33926篇
  2003年   31280篇
  2002年   31988篇
  2001年   30568篇
  2000年   26248篇
  1999年   23072篇
  1998年   21166篇
  1997年   21081篇
  1996年   21162篇
  1995年   19183篇
  1994年   18649篇
  1993年   18196篇
  1992年   18235篇
  1991年   18495篇
  1990年   17707篇
  1989年   17780篇
  1988年   17402篇
  1987年   17308篇
  1986年   16215篇
  1985年   22624篇
  1984年   23864篇
  1983年   20056篇
  1982年   21663篇
  1981年   20902篇
  1980年   20226篇
  1979年   20472篇
  1978年   21760篇
  1977年   21364篇
  1976年   21060篇
  1975年   19515篇
  1974年   19169篇
  1973年   19703篇
  1972年   14198篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
The three-band two-dimensional repulsive Hubbard model in the formalism of the temperature Green function is investigated. The applicability of the weak coupling approach at the values of the dimensionless coupling constant U/t≈10–11 is justified. The normal state, the antiferromagnetic state with Neel magnetic ordering on the “copper” sublattice, and the superconducting state with nontrivial Cooper pairing in channels with odd angular momenta are studied. The possibility of other magnetic states in the model is discussed. Bibliography: 20 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 209, 1994, pp. 194–228. Translated by K. Malyshev.  相似文献   
962.
An explicit way for producing invariants for 6-valent graphs with rigid vertices within the framework of Kauffman's approach to graph invariants is presented. These invariants can be used to detect the chirality of a 6-valent graph with rigid vertices. A relevant example is considered. Bibliography: 19 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 223, 1995, pp. 251–262. Translated by A. M. Nikitin  相似文献   
963.
964.
ASTRASSENLAWOFTHEITERATEDLOGARITHMFORPROCESSESWITHINDEPENDENTINCREMENTWangJiagangAbstractLetX={X(t),t0}beaproceswithindep...  相似文献   
965.
966.
In a previous paper (Ref. 1), an exact solution of the optimal planar interception with fixed end conditions was derived in closed form. The optimal control was expressed as an explicit function of the state variables and two fixed parameters, obtained by solving a set of nonlinear algebraic equations involving elliptic integrals. In order to facilitate the optimal control implementation, the present paper derives a highly accurate simplified solution assuming that the ratio of the pursuer turning radius to the initial range is small. An asymptotic expansion further reduces the computational workload. Construction of a near-optimal open-loop control, based on the approximations, completes the present paper.  相似文献   
967.
968.
We consider the method of normal forms, the Bogolyubov averaging method, and the method of asymptotic decomposition proposed by Yu. A. Mitropol’skii and the author of this paper. Under certain assumptions about group-theoretic properties of a system of zero approximation, the results obtained by the method of asymptotic decomposition coincide with the results obtained by the method of normal forms or the Bogolyubov averaging method. We develop a new algorithm of asymptotic decomposition by a part of the variables and its partial case — the algorithm of averaging on a compact Lie group. For the first time, it became possible to consider asymptotic expansions of solutions of differential equations on noncommutative compact groups.  相似文献   
969.
This paper deals mainly with generalizations of results in finitary combinatorics to infinite ordinals. It is well-known that for finite ordinals ∑bT<αβ is the number of 2-element subsets of an α-element set. It is shown here that for any well-ordered set of arbitrary infinite order type α, ∑bT<αβ is the ordinal of the set M of 2-element subsets, where M is ordered in some natural way. The result is then extended to evaluating the ordinal of the set of all n-element subsets for each natural number n ≥ 2. Moreover, series ∑β<αf(β) are investigated and evaluated, where α is a limit ordinal and the function f belongs to a certain class of functions containing polynomials with natural number coefficients. The tools developed for this result can be extended to cover all infinite α, but the case of finite α appears to be quite problematic.  相似文献   
970.
We give various representations of asymptotics for the probability for a Wiener process to reside within a curvilinear strip during extended time intervals.  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