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   184898篇
  免费   17976篇
  国内免费   13229篇
化学   99928篇
晶体学   1942篇
力学   12596篇
综合类   734篇
数学   44542篇
物理学   56361篇
  2024年   390篇
  2023年   2233篇
  2022年   3922篇
  2021年   4248篇
  2020年   4483篇
  2019年   4266篇
  2018年   13425篇
  2017年   12987篇
  2016年   10880篇
  2015年   6068篇
  2014年   6782篇
  2013年   8712篇
  2012年   13457篇
  2011年   19994篇
  2010年   12386篇
  2009年   12395篇
  2008年   13449篇
  2007年   14708篇
  2006年   6224篇
  2005年   6215篇
  2004年   5388篇
  2003年   5052篇
  2002年   3898篇
  2001年   2653篇
  2000年   2406篇
  1999年   2420篇
  1998年   2090篇
  1997年   1805篇
  1996年   1877篇
  1995年   1601篇
  1994年   1401篇
  1993年   1184篇
  1992年   1033篇
  1991年   911篇
  1990年   768篇
  1989年   610篇
  1988年   484篇
  1987年   432篇
  1986年   410篇
  1985年   338篇
  1984年   250篇
  1983年   202篇
  1982年   181篇
  1981年   123篇
  1980年   110篇
  1979年   74篇
  1978年   63篇
  1976年   50篇
  1973年   48篇
  1914年   45篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
讨论了C2(×)Cn量子系统的最大纠缠混合态,得到了Negativity纠缠度下的最大纠缠混合态的解析结果,并计算了该态在非满秩情形下的量子相对熵纠缠度.  相似文献   
12.
13.
Recently, research on left-handed materials (LHMs) has attracted considerable attentions. The LHMs are a kind of metameterial which have negative permittivity and negative permeability, which lead to negative refractive index in a frequency range. The LHMs that have been available so far are in the microwave range and are usually composed of classical particles, such as split-ring resonators. Some quantum phenomena such as spontaneous emission of atoms in the LHMs which are considered to be 'classical background' have also been investigated. Many potential applications of LHMs have been proposed, such as superlenses which, in principle, can achieve arbitrary subwavelength resolution.  相似文献   
14.
The principal physics goals of the Compact Muon Solenoid experiment under construction at the Large Hadron Collider at CERN in Geneva are reviewed. Procedures to search for the Standard Model Higgs boson, supersymmetric Higgses and other supersymmetric particles are described.  相似文献   
15.
We reveal that for a realistic system, interference effects are obtained such as the suppression of central line and inner sidebands and the narrowing of the outer fluorescence sidebands. For this purpose, we consider a spontaneous decay from an excited state to a metastable state when the excited and metastable states are resonantly coupled to an auxiliary metastable state by a laser field and a microwave field, respectively. The fluorescence spectrum evolves from a five-peaked structure into a doublet of ultrasharp lines as the ratio of the laser field Rabi frequency to the microwave Rabi frequency is decreased. The physical origin is presented in terms of dressed states.  相似文献   
16.
Soliton interaction under the influence of higher-order effects   总被引:6,自引:0,他引:6  
In this paper, we present exact N-soliton solution by employing simple, straightforward Darboux transformation based on the Lax pair for Hirota equation, a higher-order nonlinear Schrödinger (HNLS) equation. As examples, one- and two-soliton solutions in explicit forms are given and their properties are also analyzed. A bound solution without interaction will be theoretically predicted if one can adjust frequency shift for each soliton appropriately. Further, we obtain the approximate eigenvalues by employing two-soliton solution and discuss analytically the interaction between neighboring solitons under the influence of the higher-order effects. It is shown that the combined effects of the higher-order effects can restrain the interaction between neighboring solitons to some extent. The results are proved by directly solving HNLS equation numerically.  相似文献   
17.
It is explicitly shown that if phase transition occurs at the core of a newborn neutron star with moderately strong magnetic field strength, which populates only the electron’s Landau levels, then in the β -equilibrium condition, the quark core is energetically much more unstable than the neutron matter of identical physical condition.  相似文献   
18.
A convective flow CO laser composed of polytetrafluoroethylene discharge tubes, nickel–chromium steel components, a cupric heat exchanger and other components is described. Operating in liquid nitrogen condition, output power of 60 W has been obtained from a non-selective cavity.  相似文献   
19.
Equilibrium Problems with Applications to Eigenvalue Problems   总被引:5,自引:0,他引:5  
In this paper, we consider equilibrium problems and introduce the concept of (S)+ condition for bifunctions. Existence results for equilibrium problems with the (S)+ condition are derived. As special cases, we obtain several existence results for the generalized nonlinear variational inequality studied by Ding and Tarafdar (Ref. 1) and the generalized variational inequality studied by Cubiotti and Yao (Ref. 2). Finally, applications to a class of eigenvalue problems are given.  相似文献   
20.
Basic ideas and results which characterize quantum diffusion of defects in quantum crystals like solid helium as a new phenomenon are presented. Quantum effects in such media lead to a delocalization of point defects (vacancies, impurities etc.) and they turn into quasiparticles of a new type—defectons, which are characterized not by their position in the crystal lattice but by their quasimomentum and dispersion law. Defecton-defecton and defecton-phonon scattering are considered and an interpolation formula for the diffusion coefficient valid in all interesting temperature and concentration regions is presented. A comparison with the experimental data is made. Some alternative points of view are discussed in detail and the inconsistency of the Kisvarsanyi-Sullivan theory is shown.  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