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   20139篇
  免费   3546篇
  国内免费   3226篇
化学   15391篇
晶体学   205篇
力学   1156篇
综合类   284篇
数学   2341篇
物理学   7534篇
  2024年   17篇
  2023年   365篇
  2022年   385篇
  2021年   583篇
  2020年   754篇
  2019年   768篇
  2018年   591篇
  2017年   558篇
  2016年   889篇
  2015年   873篇
  2014年   1067篇
  2013年   1485篇
  2012年   1767篇
  2011年   1907篇
  2010年   1461篇
  2009年   1427篇
  2008年   1600篇
  2007年   1478篇
  2006年   1354篇
  2005年   1107篇
  2004年   911篇
  2003年   821篇
  2002年   750篇
  2001年   594篇
  2000年   484篇
  1999年   461篇
  1998年   373篇
  1997年   299篇
  1996年   297篇
  1995年   261篇
  1994年   219篇
  1993年   185篇
  1992年   161篇
  1991年   124篇
  1990年   124篇
  1989年   79篇
  1988年   72篇
  1987年   69篇
  1986年   46篇
  1985年   44篇
  1984年   19篇
  1983年   23篇
  1982年   16篇
  1981年   10篇
  1980年   7篇
  1978年   3篇
  1977年   5篇
  1973年   3篇
  1970年   3篇
  1957年   2篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
131.
132.
133.
河南省城市居民消费结构比较研究   总被引:8,自引:1,他引:7  
本文主要应用聚类分析方法 ,对河南省 17个地市级城市居民的消费结构进行了比较统计分析 ,从而得到了各城市居民消费结构的一些特点和规律 ,并进一步探讨了其消费结构、可支配收入与总消费支出之间的关系  相似文献   
134.
In this paper, we discuss the controllability of a nonlinear degenerate parabolic system with bilinear control. Based on the shrinking property of the solutions, we prove that the system is not globally approximately controllable. Furthermore, we give an approximate null controllability result. We also prove that the system is not globally exactly null controllable by a comparison principle.  相似文献   
135.
An effcient multiparty quantum secret sharing scheme is proposed with Greenberger-Horne-Zeilinger (GHZ) states following some ideas in quantum dense coding. The agents take the single-photon measurements on the photons received for eavesdropping check and exploit the four local unitary operations Ⅰ, σx, σx and iσy to code their message. This scheme has the advantage of high capacity as each GHZ state can carry two bits of information. The parties do not need to announce the measuring bases for almost all the photons, which will reduce the classical information exchanged largely. The intrinsic efficiency for qubits and the total effciency both approach the maximal values.  相似文献   
136.
Generalized KKM Type Theorems in FC-Spaces with Applications (I)   总被引:1,自引:0,他引:1  
The class KKM(X,Y) (resp., s-KKM(X,Y,Z)) of set-valued mappings with KKM (resp., s-KKM) property is introduced in FC-spaces without any convexity structure. Some generalized KKM (resp., s-KKM) type theorems are proved in FC-spaces under much weak assumptions. As applications, some new section theorems and coincidence theorems are established in FC-spaces. These theorems generalize many known results in literature. The further applications of these results will be given in a follow-up paper.  相似文献   
137.
Introduction Parkinson′sdisease(PD),alsocalledshaking palsy,isaneurodegenerativedisorderandfrequently occursinthepeopleabovetheageof65[1].PDisa relativelycommonneurodegenerativedisorder,which hasclinicalsymptomsincludingbradykinesia,rest tremor,rigidity,…  相似文献   
138.
In this paper we give a geometric interpretation of the notion of the horizontal mean curvature which is introduced by Danielli Garofalo-Nhieu and Pauls who recently introduced sub- Riemannian minimal surfaces in Carnot groups. This will be done by introducing a natural nonholonomic connection which is the restriction (projection) of the natural Riemannian connection on the horizontal bundle. For this nonholonomic connection and (intrinsic) regular hypersurfaces we introduce the notions of the horizontal second fundamental form and the horizontal shape operator. It turns out that the horizontal mean curvature is the trace of the horizontal shape operator.  相似文献   
139.
This paper investigates bivariate recursive equations on excess-of-loss reinsurance. For an insurance portfolio, under the assumptions that the individual claim severity distribution has bounded continuous density and the number of claims belongs to R1 (a, b) family, bivariate recursive equations for the joint distribution of the cedent's aggregate claims and the reinsurer's aggregate claims are obtained.  相似文献   
140.
In this paper, we study a micro‐macro model for polymeric fluid. The system involves coupling between the macroscopic momentum equation and a microscopic evolution equation describing the combined effects of the microscopic potential and thermofluctuation. We employ an energetic variation procedure to explore the relation between the macroscopic transport of the particles and the induced elastic stress due to the microscopic structure. For the initial data not far from the equilibrium, we prove the global existence and uniqueness of classical solutions to the system. © 2006 Wiley Periodicals, Inc.  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