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   1337355篇
  免费   32559篇
  国内免费   10752篇
化学   671244篇
晶体学   20295篇
力学   75234篇
综合类   341篇
数学   242051篇
物理学   371501篇
  2021年   14063篇
  2020年   16550篇
  2019年   16803篇
  2016年   28079篇
  2015年   21396篇
  2014年   31409篇
  2013年   75677篇
  2012年   38921篇
  2011年   34928篇
  2010年   37234篇
  2009年   39763篇
  2008年   34119篇
  2007年   29162篇
  2006年   36818篇
  2005年   28015篇
  2004年   29761篇
  2003年   28109篇
  2002年   29466篇
  2001年   28820篇
  2000年   25149篇
  1999年   22917篇
  1998年   21419篇
  1997年   21379篇
  1996年   21418篇
  1995年   19454篇
  1994年   18853篇
  1993年   18361篇
  1992年   18246篇
  1991年   18512篇
  1990年   17661篇
  1989年   17712篇
  1988年   17188篇
  1987年   17181篇
  1986年   16124篇
  1985年   22515篇
  1984年   23752篇
  1983年   19933篇
  1982年   21627篇
  1981年   20859篇
  1980年   20180篇
  1979年   20308篇
  1978年   21659篇
  1977年   21238篇
  1976年   20949篇
  1975年   19653篇
  1974年   19282篇
  1973年   19801篇
  1972年   14281篇
  1968年   12095篇
  1967年   12486篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
In this paper we consider a wavelet algorithm for the piecewise constant collocation method applied to the boundary element solution of a first kind integral equation arising in acoustic scattering. The conventional stiffness matrix is transformed into the corresponding matrix with respect to wavelet bases, and it is approximated by a compressed matrix. Finally, the stiffness matrix is multiplied by diagonal preconditioners such that the resulting matrix of the system of linear equations is well conditioned and sparse. Using this matrix, the boundary integral equation can be solved effectively.  相似文献   
942.
The Thoms effect observed with water-soluble cationic copolymer of acrylamide was studied in relation to the concentration, molecular weight, and molecular weight polydispersity of the polymeric additive, with its composition and composition polydispersity being constant.  相似文献   
943.
    
  相似文献   
944.
We propose a numerical-experimental method of determining the residual stresses in welded shells of revolution. We solve the inverse conditionally correct problem of recovering the complete picture of the residual stress state from part of the experimental values obtained by the method of photoelasticity. We apply the numerical spline-collocation method. Translated fromMatematichni Metodi ta Fiziko-mekhanichni Polya, Vol. 39, No. 1, 1996, pp. 149–151.  相似文献   
945.
We prove a character formula for any finite-dimensional irreducible representationV of the “queer” Lie superalgebra g=q(n). It expresses chV in terms of the multiplicities of the irreducible g-subquotients of the cohomology groups of certain dominant g-bundles on the Π-symmetric projective spaces (i.e., on the homogeneous superspacesG/P whose reduced space is a projective space, whereG=Q(n)). We also establish recurrent relations for the above multiplicities, and this enables us to compute explicitly chV for any givenV. This provides a complete solution to the Kac character problem for the Lie superalgebraq(n). Finally, we consider the particular cases ofq(2), q(3), andq(4) in which we compare the new character formula with the generic character formula of [12]. Translated from Itogi Nauki i Tekhniki, Seriya Sovremennaya Matematika i Ee Prilozheniya. Tematicheskie Obzory. Vol. 41, Algebraic Geometry-7, 1997.  相似文献   
946.
Multidimensional two-phase Stefan (k=1) and nonstationary filtration Florin (k=0) problems for second order parabolic equations in the case when the free boundary is a graph of a functionx n k (xt),x′∈ n?1 ,n≥2,t∈(0,T) are studied. A unique solvability theorem in weighted Hölder spaces of functions with time power weight is proved, coercive estimates for solutions are obtained. Bibliography: 30 titles.  相似文献   
947.
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   
948.
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   
949.
950.
ASTRASSENLAWOFTHEITERATEDLOGARITHMFORPROCESSESWITHINDEPENDENTINCREMENTWangJiagangAbstractLetX={X(t),t0}beaproceswithindep...  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