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   60283篇
  免费   9982篇
  国内免费   1435篇
化学   56726篇
晶体学   497篇
力学   973篇
综合类   1篇
数学   6743篇
物理学   6760篇
  2023年   164篇
  2022年   154篇
  2021年   405篇
  2020年   1582篇
  2019年   2944篇
  2018年   1475篇
  2017年   1076篇
  2016年   4113篇
  2015年   4066篇
  2014年   4013篇
  2013年   5523篇
  2012年   4386篇
  2011年   3685篇
  2010年   3691篇
  2009年   3556篇
  2008年   3719篇
  2007年   3126篇
  2006年   2710篇
  2005年   2793篇
  2004年   2556篇
  2003年   2188篇
  2002年   2762篇
  2001年   1877篇
  2000年   1765篇
  1999年   741篇
  1998年   323篇
  1997年   329篇
  1996年   394篇
  1995年   275篇
  1994年   316篇
  1993年   274篇
  1992年   264篇
  1991年   230篇
  1990年   231篇
  1989年   201篇
  1988年   186篇
  1987年   178篇
  1986年   175篇
  1985年   253篇
  1984年   274篇
  1983年   188篇
  1982年   212篇
  1981年   225篇
  1980年   224篇
  1979年   180篇
  1978年   175篇
  1977年   197篇
  1976年   164篇
  1975年   165篇
  1974年   130篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
81.
In the present Note we introduce an extension of the conservative space–time mesh refinement method presented by Fouquet et al. We also propose a post-treatment of the solution that reduces the spurious phenomena due to the non-conformity between the time meshes. A reinterpretation of the equations in terms of new unknowns leads to a new scheme with second order consistent coupling equations. Numerical experiments in 2D and a plane wave analysis for the 1D model show that the method is second order accurate for an arbitrary refinement. To cite this article: J. Rodríguez, C. R. Acad. Sci. Paris, Ser. I 339 (2004).  相似文献   
82.
Sauer, Shelah, Vapnik and Chervonenkis proved that if a set system on n vertices contains many sets, then the set system has full trace on a large set. Although the restriction on the size of the groundset cannot be lifted, Frankl and Pach found a trace structure that is guaranteed to occur in uniform set systems even if we do not bound the size of the groundset. In this note we shall give three sequences of structures such that every set system consisting of sufficiently many sets contains at least one of these structures with many sets.  相似文献   
83.
The distribution of mono- poly- and unlabelled protein molecules in the radiolabelling mixture was calculated from probability point of view as a function of the radioiodine/protein ratio.  相似文献   
84.
85.
86.
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   
87.
In order to study the influence of seeded impurities on ITER like reactor operation the COREDIV code has been extended to include the transport of several sputtered and/or injected impurities. In the COREDIV code the core plasma is treated in the frame of 1D radial transport model whereas in the edge the 2D multifluid code EPIT is used. The EPIT code solves in the slab geometry the MHD equations for densities and velocities for all ions species as well as for electron and ion temperatures. The iteration scheme in the code leads to steady state solution of coupled core and SOL system. The numerical results for Carbon and Nickel plate and seeded impurities Silicon and Neon are presented.  相似文献   
88.
In the title compound, catena‐poly[lithium‐μ3‐ethyl­ene­diphos­phon­ato], [Li(C2H7O6P2)]n, the supra­molecular monoclinic (C2/c) structure consists of one‐dimensional lithium chains [Li⋯Li = 2.7036 (8) Å] that are embedded within ethyl­ene­diphosphon­ate anions linked by strong symmetric hydrogen bonds [O⋯O = 2.473 (3) Å]. The Li atoms and the H atom in the symmetric hydrogen bond reside on twofold rotation axes and there is an inversion center at the mid‐point of the C—C bond of the ethylenediphosphonate ligand.  相似文献   
89.
The inhomogeneous Dirichlet problems concerning divergence form elliptic equations are studied. Optimal regularity requirements on the coefficients and domains for the W1,p theory, 1 < p < ∞, are obtained. The principal coefficients are supposed to be in the John‐Nirenberg space with small BMO seminorms. The domain is a Reifenberg domain. These conditions for the W1,p theory not only weaken the requirements on the coefficients but also lead to a more general geometric condition on the domains. In fact, these domains might have fractal dimensions. © 2004 Wiley Periodicals, Inc.  相似文献   
90.
Ohne Zusammenfassung Die mitgeteilten Untersuchungen haben wir mit Unterstützung der Ungarischen wissenschaftlichen „Széchenyi“-Gesellschaft durchgeführt.  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