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   87359篇
  免费   6391篇
  国内免费   13795篇
化学   64910篇
晶体学   2328篇
力学   1647篇
综合类   624篇
数学   16524篇
物理学   21512篇
  2024年   189篇
  2023年   1239篇
  2022年   2541篇
  2021年   2497篇
  2020年   2445篇
  2019年   2504篇
  2018年   2176篇
  2017年   2558篇
  2016年   2675篇
  2015年   2410篇
  2014年   3469篇
  2013年   7190篇
  2012年   4837篇
  2011年   5882篇
  2010年   4992篇
  2009年   6061篇
  2008年   5944篇
  2007年   6100篇
  2006年   5527篇
  2005年   4665篇
  2004年   4408篇
  2003年   3692篇
  2002年   3141篇
  2001年   2444篇
  2000年   2357篇
  1999年   1984篇
  1998年   1734篇
  1997年   1472篇
  1996年   1402篇
  1995年   1373篇
  1994年   1246篇
  1993年   1050篇
  1992年   971篇
  1991年   699篇
  1990年   480篇
  1989年   475篇
  1988年   395篇
  1987年   305篇
  1986年   252篇
  1985年   304篇
  1984年   242篇
  1983年   114篇
  1982年   178篇
  1981年   201篇
  1980年   158篇
  1979年   123篇
  1978年   99篇
  1977年   106篇
  1976年   71篇
  1973年   58篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
21.
We show that there are close relations between extremal problems in dual Brunn-Minkowski theory and isotropic-type properties for some Borel measures on the sphere. The methods we use allow us to obtain similar results in the context of Firey-Brunn-Minkowski theory. We also study reverse inequalities for dual mixed volumes which are related with classical positions, such as ?-position or isotropic position.  相似文献   
22.
多媒体在二维动量实验中的应用   总被引:2,自引:1,他引:1  
利用VisualBasic的多媒体功能和CCD摄像头以及气垫桌等组成的实验系统,演示了二维碰撞中的动量守恒.  相似文献   
23.
Various 2-substituted indoles were prepared by heteroannulation of o-iodoanilines and terminal alkynes in a one-pot reaction with a Pd(II)-NaY zeolite catalyst. The product formation largely depended on the solvent, base, and reaction temperature. The recycled catalyst showed good reusability in the heteroannulation reaction.  相似文献   
24.
Rhodium catalysts have been prepared on palygorskite and montmorillonite (clay) supports by reduction with hydrogen (1 atmosphere) at room temperature of a cationic organometallic rhodium compound anchored to the support. The activity of these catalysts for the hydrogenation of liquid-phase 1-hexene remains constant with increase of prehydrogenation time and with re-use for several runs. No rhodium leaching is observed.  相似文献   
25.
We show that the Hardy-Littlewood maximal operator and a class of Calderón-Zygmund singular integrals satisfy the strong type modular inequality in variable Lp spaces if and only if the variable exponent p(x) ∼ const. Received: 15 September 2004  相似文献   
26.
Basic principles of the generalized lattice model of multicomponent condensed systems are formulated. Short-range parts of interatomic interactions are taken into account by means of the geometric constraints method. Long-range parts of the interactions are taken into account in mean field approximation. The expression for Helmholtz free energy is obtained. A system of integral equations for the equilibrium distributions of components is derived. The asymptotic properties of its solutions are investigated. Moment expansion of interatomic interactions and localization of integral terms in free energy is obtained. A Ginzburg–Landau-like functional of free energy is derived.  相似文献   
27.
Nonlocal vertex algebras generated by formal vertex operators   总被引:2,自引:0,他引:2  
This is the first paper in a series to study vertex algebra-like objects arising from infinite-dimensional quantum groups (quantum affine algebras and Yangians). In this paper we lay the foundations for this study. For any vector space W, we study what we call quasi compatible subsets of Hom (W,W((x))) and we prove that any maximal quasi compatible subspace has a natural nonlocal (namely noncommutative) vertex algebra structure with W as a natural faithful quasi module in a certain sense, and that any quasi compatible subset generates a nonlocal vertex algebra with W as a quasi module. In particular, taking W to be a highest weight module for a quantum affine algebra we obtain a nonlocal vertex algebra with W as a quasi module. We also formulate and study a notion of quantum vertex algebra and we give general constructions of nonlocal vertex algebras, quantum vertex algebras and their modules.  相似文献   
28.
A graph G is N2locally connected if for every vertex ν in G, the edges not incident with ν but having at least one end adjacent to ν in G induce a connected graph. In 1990, Ryjá?ek conjectured that every 3‐connected N2‐locally connected claw‐free graph is Hamiltonian. This conjecture is proved in this note. © 2004 Wiley Periodicals, Inc. J Graph Theory 48: 142–146, 2005  相似文献   
29.
30.
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