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   17443篇
  免费   453篇
  国内免费   548篇
化学   4564篇
晶体学   98篇
力学   135篇
综合类   24篇
数学   11400篇
物理学   2223篇
  2023年   72篇
  2022年   126篇
  2021年   114篇
  2020年   156篇
  2019年   346篇
  2018年   325篇
  2017年   237篇
  2016年   226篇
  2015年   260篇
  2014年   439篇
  2013年   1193篇
  2012年   530篇
  2011年   899篇
  2010年   720篇
  2009年   1087篇
  2008年   1223篇
  2007年   1270篇
  2006年   982篇
  2005年   703篇
  2004年   605篇
  2003年   604篇
  2002年   463篇
  2001年   352篇
  2000年   370篇
  1999年   404篇
  1998年   399篇
  1997年   345篇
  1996年   359篇
  1995年   449篇
  1994年   367篇
  1993年   341篇
  1992年   342篇
  1991年   191篇
  1990年   199篇
  1989年   219篇
  1988年   147篇
  1987年   145篇
  1986年   127篇
  1985年   164篇
  1984年   134篇
  1983年   91篇
  1982年   151篇
  1981年   112篇
  1980年   96篇
  1979年   71篇
  1978年   92篇
  1977年   75篇
  1976年   72篇
  1975年   19篇
  1974年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
In [P. Sarnak, Class numbers of indefinite binary quadratic forms, J. Number Theory 15 (1982) 229-247], it was proved that the Selberg zeta function for SL2(Z) is expressed in terms of the fundamental units and the class numbers of the primitive indefinite binary quadratic forms. The aim of this paper is to obtain similar arithmetic expressions of the logarithmic derivatives of the Selberg zeta functions for congruence subgroups of SL2(Z). As applications, we study the Brun-Titchmarsh type prime geodesic theorem and the asymptotic formula of the sum of the class number.  相似文献   
92.
This article proposes a reweighted estimator of multivariate location and scatter, with weights adaptively computed from the data. Its breakdown point and asymptotic behavior under elliptical distributions are established. This adaptive estimator is able to attain simultaneously the maximum possible breakdown point for affine equivariant estimators and full asymptotic efficiency at the multivariate normal distribution. For the special case of hard-rejection weights and the MCD as initial estimator, it is shown to be more efficient than its non-adaptive counterpart for a broad range of heavy-tailed elliptical distributions. A Monte Carlo study shows that the adaptive estimator is as robust as its non-adaptive relative for several types of bias-inducing contaminations, while it is remarkably more efficient under normality for sample sizes as small as 200.  相似文献   
93.
We establish a mean square estimate on the weight aspect for symmetric square L-functions at every point on the critical line. Received: 15 February 2002  相似文献   
94.
A nonlinear operator equation F(x)=0, F:HH, in a Hilbert space is considered. Continuous Newton’s-type procedures based on a construction of a dynamical system with the trajectory starting at some initial point x 0 and becoming asymptotically close to a solution of F(x)=0 as t→+∞ are discussed. Well-posed and ill-posed problems are investigated. Received: June 29, 2001; in final form: February 26, 2002?Published online: February 20, 2003 This paper was finished when AGR was visiting Institute for Theoretical Physics, University of Giessen. The author thanks DAAD for support  相似文献   
95.
Reduced forms of iso‐α‐acids (isohumulones), used in modern beer brewing were separated and characterized by 1H and 13C NMR spectroscopy. Components from mixtures of rho‐iso‐α‐acids, tetrahydro‐iso‐α‐acids, and hexahydro‐iso‐α‐acids were isolated using high‐performance liquid chromatography (HPLC) and analyzed by use of one‐ and two‐dimensional NMR experiments. The data presented assign the identities of the main peaks in the HPLC traces for the reduced iso‐α‐acids. Previous tentative assignments regarding the cis and trans configurations and the structures of the acyl residues of the reduced iso‐α‐acids were confirmed and extensive NMR assignments were made. Furthermore, the previously unknown stereochemistry in the C‐4 side‐chain of the rho‐ and hexahydro‐iso‐α‐acids was assigned. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
96.
We describe an equivariant version (for actions of a finite group G) of Dold’s index theory, [10], for iterated maps. Equivariant Dold indices are defined, in general, for a G-map UX defined on an open G-subset of a G-ANR X (and satisfying a suitable compactness condition). A local index for isolated fixed-points is introduced, and the theorem of Shub and Sullivan on the vanishing of all but finitely many Dold indices for a continuously differentiable map is extended to the equivariant case. Homotopy Dold indices, arising from the equivariant Reidemeister trace, are also considered.   相似文献   
97.
In this paper, we investigate symplectic manifolds endowed with a Morse–Bott function with only two critical submanifolds, one of which is Lagrangian while the other one is symplectic.  相似文献   
98.
In this paper we first give a lower bound on multiplicities for Buchsbaum homogeneous k-algebras A in terms of the dimension d, the codimension c, the initial degree q, and the length of the local cohomology modules of A. Next, we introduce the notion of Buchsbaum k-algebras with minimal multiplicity of degree q, and give several characterizations for those rings. In particular, we will show that those algebras have linear free resolutions. Further, we will give many examples of those algebras.  相似文献   
99.
In this paper, we establish a theorem on the distribution of primes in quadratic progressions on average.  相似文献   
100.
本文讨论定义在Banach空间上的,既具有等式约束又具有不等式约束的,非光滑(F,P)不变凸多目标规划的Wolfe对偶性,Mond-Weir型对偶性可类似讨论之。  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