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   379239篇
  免费   2677篇
  国内免费   1040篇
化学   189473篇
晶体学   6006篇
力学   19009篇
综合类   7篇
数学   44580篇
物理学   123881篇
  2020年   3312篇
  2019年   3891篇
  2018年   5418篇
  2017年   5487篇
  2016年   7290篇
  2015年   3907篇
  2014年   6911篇
  2013年   15946篇
  2012年   12062篇
  2011年   14682篇
  2010年   11142篇
  2009年   11262篇
  2008年   13802篇
  2007年   13795篇
  2006年   12735篇
  2005年   11448篇
  2004年   10776篇
  2003年   9613篇
  2002年   9708篇
  2001年   11069篇
  2000年   8403篇
  1999年   6534篇
  1998年   5696篇
  1997年   5456篇
  1996年   5146篇
  1995年   4672篇
  1994年   4632篇
  1993年   4706篇
  1992年   4853篇
  1991年   5279篇
  1990年   4971篇
  1989年   4999篇
  1988年   4883篇
  1987年   4813篇
  1986年   4534篇
  1985年   6008篇
  1984年   6186篇
  1983年   5056篇
  1982年   5385篇
  1981年   5204篇
  1980年   4935篇
  1979年   5270篇
  1978年   5529篇
  1977年   5505篇
  1976年   5657篇
  1975年   5221篇
  1974年   5171篇
  1973年   5349篇
  1972年   4015篇
  1971年   3483篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
The nonlinear theory of thermally stimulated depolarization currents is developed. The theory explains the processes of hetero- and homocharge relaxation in complex crystals with hydrogen bonds and allows the relaxation oscillator parameters to be calculated using the quadratic approximation for the external electric field.  相似文献   
122.
We study correlations in the exclusive reaction at rest with complete reconstruction of the kinematics for each event. The inclusive distribution is fairly flat at small invariant mass of the pion pair while a small enhancement in the double differential distribution is observed for small invariant masses of both pion pairs. Dynamical models with resonances in the final state are shown to be consistent with the data while the stochastic HBT mechanism is not supported by the present findings. Received: 26 February 2002 / Revised version: 22 July 2002 / Published online: 30 August 2002  相似文献   
123.
Magnetization and remagnetization processes in a close-packed nanodispersed barium hexaferrite powder sample in the magnetically stable state were analyzed. Reversibility effects were discussed in terms of interparticle interaction. Judging from the magnetization curve and the parameters characterizing remagnetization irreversibility, the sample under study is a model system of small Stoner-Wohlfarth particles.  相似文献   
124.
A condition for regularization of boundary-contact integrals in two-dimensional problems of acoustics is considered. With an example of the simplest boundary-contact problem of acoustics, it is shown that a known sufficient condition for regularization is also a necessary one. The study of analytic properties of the transition admittance of an infinite plate that is in contact with a medium is conducted in order to obtain this statement. The considerations are carried out in general terms. The results obtained may be used in arbitrary models of plate theory, and they also may be adapted to boundary-contact problems of another physical nature. Bibliography: 9 titles.  相似文献   
125.
126.
We discuss a mass change that has its origin in the action of forces on an object. This phenomenon, well-known in the context of quantum field theory (mass renormalization), can be discussed systematically in both classical and quantum mechanics in a framework given by Stückelberg. We employ this framework to resolve an interesting conflict of opinions between Schopenhauer and Hegel in the mid-19th century. We show that Hegel, Kant, and Schopenhauer demonstrated remarkable prescience in their views as seen from a modern perspective.  相似文献   
127.
Mutual–temporal coherence of the supercontinuum (SC) generation has been experimentally investigated using a diffraction grating based interferometer. A broadband SC generation was produced in a pyrex glass plate with a 1.6-μm coherence length at 550-nm center wavelength. The degree of mutual coherence of 0.34 was measured for a wavefront shift for zero and first diffraction orders of half of the beam diameter. A design of SC source with the capability of manipulating the amplitudes and phases of optical frequency components within the SC pulse is presented for coherence applications.  相似文献   
128.
The conditions for obtaining a high efficiency of energy exchange upon two-wave interactions in dynamic holograms are found by analysis and numerical simulation of a system of nonlinear equations. Use of an asymmetric scheme of beam interaction in a medium with two nonlinearities, one of which determines the amplitude and relaxation time of a grating and the other of which provides phase modulation of the interacting beams, is proposed. It is shown that such a scheme in combination with the specific properties of a medium makes it possible to radically reduce the requirements for the nonlinearity of a medium and the intensity of a light flux in limiting systems, as well as to significantly decrease the time of the transition process. As a result, it becomes possible to attain an efficiency of energy transfer higher than 90% and to increase the corresponding attenuation of a high-power beam by almost two orders of magnitude, which is of interest for optical limiting of intense light fluxes.  相似文献   
129.
Frank  A. I.  Nosov  V. G. 《JETP Letters》2004,79(7):313-315
JETP Letters - The problem of storing ultracold neutrons over a plane magnetic mirror in the presence of gravity is considered. For neutrons with a definite polarization, the sum of the magnetic...  相似文献   
130.
Bibliography: 42 titles.__________Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 306, 2003, pp. 7–15.  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