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   8390篇
  免费   217篇
  国内免费   229篇
化学   872篇
晶体学   25篇
力学   68篇
综合类   24篇
数学   6864篇
物理学   983篇
  2023年   18篇
  2022年   35篇
  2021年   42篇
  2020年   48篇
  2019年   185篇
  2018年   196篇
  2017年   111篇
  2016年   84篇
  2015年   111篇
  2014年   219篇
  2013年   488篇
  2012年   321篇
  2011年   459篇
  2010年   421篇
  2009年   624篇
  2008年   650篇
  2007年   608篇
  2006年   517篇
  2005年   307篇
  2004年   286篇
  2003年   276篇
  2002年   238篇
  2001年   226篇
  2000年   199篇
  1999年   279篇
  1998年   219篇
  1997年   150篇
  1996年   201篇
  1995年   236篇
  1994年   196篇
  1993年   160篇
  1992年   114篇
  1991年   68篇
  1990年   55篇
  1989年   69篇
  1988年   36篇
  1987年   33篇
  1986年   26篇
  1985年   60篇
  1984年   41篇
  1983年   28篇
  1982年   37篇
  1981年   50篇
  1980年   25篇
  1979年   19篇
  1978年   11篇
  1977年   14篇
  1976年   10篇
  1975年   9篇
  1974年   11篇
排序方式: 共有8836条查询结果,搜索用时 363 毫秒
21.
Operators on manifolds with corners that have base configurations with geometric singularities can be analysed in the frame of a conormal symbolic structure which is in spirit similar to the one for conical singularities of Kondrat'ev's work. Solvability of elliptic equations and asymptotics of solutions are determined by meromorphic conormal symbols. We study the case when the base has edge singularities which is a natural assumption in a number of applications. There are new phenomena, caused by a specific kind of higher degeneracy of the underlying symbols. We introduce an algebra of meromorphic edge operators that depend on complex parameters and investigate meromorphic inverses in the parameter-dependent elliptic case. Among the examples are resolvents of elliptic differential operators on manifolds with edges.  相似文献   
22.
70K温区混合工质分凝分离循环节流制冷机实验研究   总被引:1,自引:0,他引:1  
混合工质节流制冷机正在许多方面获得越来越广泛的应用。文中设计了一种新型的混合工质分凝分离循环 ,建立了实验系统 ,并在 70 K温区进行了实验。实验结果表明 ,节流制冷机可以达到 6 5 .3K的低温 ,并在 72 K温度提供 1W的制冷量 ,输入功率为 5 0 0 W。  相似文献   
23.
A number of new functionalised bridged indolocarbazole systems have been prepared by ring-opening reactions of a key cyclic sulfate intermediate, prepared from the corresponding diol by the action of sulfuryl diimidazole and DBU. The same cyclic sulfate also undergoes an unprecedented asymmetric rearrangement to a chiral ketone, on treatment with a chiral lithium amide base.  相似文献   
24.
We analyze the long-time behavior of transport equations for a class of dissipative quantum systems with Fokker-planck type diffusion operator, subject to confining potentials of harmonic oscillator type. We establish the existence and uniqueness of a non-equilibrium steady state for the corresponding dynamics. Further, using a (classical) convex Sobolev inequality, we prove an optimal exponential rate of decay towards this state and additionally give precise dispersion estimates in those cases, where no stationary state exists.  相似文献   
25.
In present paper the parabolic equation solution is built. The construction is reduced to iterative procedure. And convergence of the latter is proven.  相似文献   
26.
Summary. We study a diffusion model of an interacting particles system with general drift and diffusion coefficients, and electrostatic inter-particles repulsion. More precisely, the finite particle system is shown to be well defined thanks to recent results on multivalued stochastic differential equations (see [2]), and then we consider the behaviour of this system when the number of particles goes to infinity (through the empirical measure process). In the particular case of affine drift and constant diffusion coefficient, we prove that a limiting measure-valued process exists and is the unique solution of a deterministic PDE. Our treatment of the convergence problem (as ) is partly similar to that of T. Chan [3] and L.C.G. Rogers - Z. Shi [5], except we consider here a more general case allowing collisions between particles, which leads to a second-order limiting PDE. Received: 5 August 1996 / In revised form: 17 October 1996  相似文献   
27.
28.
29.
Summary. We present a simple proof, based on modified logarithmic Sobolev inequalities, of Talagrand’s concentration inequality for the exponential distribution. We actually observe that every measure satisfying a Poincaré inequality shares the same concentration phenomenon. We also discuss exponential integrability under Poincaré inequalities and its consequence to sharp diameter upper bounds on spectral gaps. Received: 10 June 1996 / In revised form: 9 August 1996  相似文献   
30.
Magnetic Properties of the Cobaltates Na6CoS4, Na6CoSe4, and K6CoS4 The alkali metal cobalt chalcogenides Na6CoS4, Na6CoSe4, and K6CoS4 crystallize in the space group P63mc with Z = 4. The structure is characterized by isolated [CoX4]-tetrahedra. The magnetic susceptibilities show Curie-Weiss behaviour. The deviations at low temperatures are caused by antiferromagnetic interactions. The magnetic moments are discussed with regard to ligand-field parameters.  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