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   582323篇
  免费   6739篇
  国内免费   1752篇
化学   313571篇
晶体学   8607篇
力学   25144篇
综合类   19篇
数学   69566篇
物理学   173907篇
  2021年   4849篇
  2020年   5444篇
  2019年   5968篇
  2018年   7872篇
  2017年   7714篇
  2016年   11471篇
  2015年   7111篇
  2014年   10979篇
  2013年   26528篇
  2012年   20122篇
  2011年   24726篇
  2010年   17548篇
  2009年   17267篇
  2008年   22910篇
  2007年   22909篇
  2006年   21277篇
  2005年   19164篇
  2004年   17551篇
  2003年   15611篇
  2002年   15437篇
  2001年   17008篇
  2000年   13089篇
  1999年   10199篇
  1998年   8570篇
  1997年   8349篇
  1996年   8023篇
  1995年   7027篇
  1994年   7017篇
  1993年   6893篇
  1992年   7589篇
  1991年   7735篇
  1990年   7367篇
  1989年   7186篇
  1988年   7207篇
  1987年   7048篇
  1986年   6705篇
  1985年   8733篇
  1984年   8997篇
  1983年   7156篇
  1982年   7453篇
  1981年   7323篇
  1980年   6827篇
  1979年   7362篇
  1978年   7643篇
  1977年   7501篇
  1976年   7452篇
  1975年   6937篇
  1974年   6916篇
  1973年   7016篇
  1972年   4886篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
991.
A self-consistent, completely quantum calculation of the structure of the inner crust of neutron stars is carried out in the Wigner-Seitz approximation with a realistic phenomenological nuclear energy functional, where pair correlations of neutrons and protons are included in the explicit form. It has been shown that the superfluidity of neutrons and protons affects the structure of the ground state of the crust.  相似文献   
992.
Journal of Statistical Physics - We study high-energy asymptotics of the steady velocity distributions for model kinetic equations describing various regimes in dilute granular flows. The main...  相似文献   
993.
The kinetics of formation and relaxation of transient holographic gratings recorded in a system of saturable three-level centers is studied. Distortions in the shape of the profile of recorded and decaying structures of population and of the refractive index are taken into account. The analysis of the time dependences of diffraction efficiencies of different orders is performed for phase (thermal) and amplitude (concentration) gratings.  相似文献   
994.
We examine several interesting relationships and expressions involving Fourier-Feynman transform, convolution product and first variation for functionals in the Fresnel class F(B) of an abstract Wiener space B. We also prove a translation theorem and Parseval's identity for the analytic Feynman integral. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   
995.
A Pd-catalyzed three-component assembling of highly functionalized 4-benzyl-(and allyl-)pyrrolidines was achieved based on a combination of allyl amines, gem-diactivated alkenes, and unsaturated halides (or triflate).  相似文献   
996.
Rees  D. A. S.  Magyari  E.  Keller  B. 《Transport in Porous Media》2003,53(3):347-355
The effect of viscous dissipation on the development of the boundary layer flow from a cold vertical surface embedded in a Darcian porous medium is investigated. It is found that the flow evolves gradually from the classical Cheng–Minkowycz form to the recently discovered asymptotic dissipation profile which is a parallel flow.  相似文献   
997.
In this paper we analyze the bottom of the energy-momentum spectrum of the translation invariant Nelson model, describing one electron linearly coupled to a second quantized massive scalar field. Our results are valid for all values of the coupling constant and include an HVZ theorem, non-degeneracy of ground states, existence of isolated groundstates in dimensions 1 and 2, non-existence of ground states embedded in the bottom of the essential spectrum in dimensions 3 and 4, (i.e., at total momenta where no isolated groundstate eigenvalue exists), and we study regularity and monotonicity properties of the bottom of the essential spectrum, as a function of total momentum. Communicated by Joel Feldman submitted 04/11/04, accepted 17/02/05  相似文献   
998.
999.
One of the most ignored, but urgent and vital challenges confronting society today is the vulnerability of urban areas to extreme events. Current organization of response systems, predominantly based on a command and control model, limits their effectiveness and efficiency. Particularly, in decision‐making processes where a large number of actors may be involved. In this article, a new distributed collaborative decision‐making model is proposed to overcome command and control limitations encountered in stressful, hostile, chaotic, and large‐scale settings. This model was derived by borrowing concepts from the collective decision making of honeybees foraging, a successful process in solving complex tasks within complex settings. The model introduced in this article was evaluated through differential equations, i.e., continuous analysis, and difference equations, i.e., discrete analysis. The most important result found is that the best available option in any large‐scale decision‐making problem can be configured as an attractor, in a distributed and timely manner. We suggest that the proposed model has the potential to facilitate decision‐making processes in large‐scale settings. © 2005 Wiley Periodicals, Inc. Complexity 11:28–38, 2005  相似文献   
1000.
In this paper, we give necessary and sufficient conditions for a bilateral operator weighted shift to enjoy the single-valued extension property.

  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