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   78293篇
  免费   595篇
  国内免费   123篇
化学   41672篇
晶体学   1265篇
力学   3305篇
综合类   1篇
数学   7974篇
物理学   24794篇
  2022年   629篇
  2021年   879篇
  2020年   979篇
  2019年   1109篇
  2018年   1604篇
  2017年   1701篇
  2016年   2171篇
  2015年   1039篇
  2014年   1737篇
  2013年   3308篇
  2012年   2936篇
  2011年   3320篇
  2010年   2677篇
  2009年   2664篇
  2008年   3044篇
  2007年   2903篇
  2006年   2796篇
  2005年   2462篇
  2004年   2274篇
  2003年   2088篇
  2002年   2158篇
  2001年   2251篇
  2000年   1645篇
  1999年   1260篇
  1998年   1138篇
  1997年   1045篇
  1996年   906篇
  1995年   840篇
  1994年   818篇
  1993年   818篇
  1992年   872篇
  1991年   940篇
  1990年   884篇
  1989年   908篇
  1988年   826篇
  1987年   771篇
  1986年   739篇
  1985年   869篇
  1984年   965篇
  1983年   823篇
  1982年   839篇
  1981年   747篇
  1980年   704篇
  1979年   771篇
  1978年   894篇
  1977年   916篇
  1976年   810篇
  1975年   776篇
  1974年   790篇
  1973年   760篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Summary The main purpose of this paper is to introduce the concepts of η-sets, ηζ-sets,η-continuity and ηζ-continuity and to obtain a decomposition of continuity.  相似文献   
72.
Electrochemical separation of lead-silver alloys into the constituents by thin-layer electrolysis in molten electrolytes, with bismuth as metal separator, is studied. It is proposed to determine the extent of component recovery by potentiometry.  相似文献   
73.
The procedure for calculating the dispersion of the refractive and absorption indices and thickness of an optical film, based on measurements of spectral dependence of the transmittance, is described. The film parameters are calculated using a solution of the approximation problem. The effect of the film model on the calculated values of the refractive and absorption indices is analyzed.  相似文献   
74.
75.
The process of harmonic wave propagation is investigated in a semi-infinite rigidly-clamped elastic layer. An analytic solution of the problem is obtained by the superposition method. The wave field expansion in the form of a normal mode series for a corresponding infinite waveguide is established. According to residue theory, the explicit form of the expansion coefficients is established with physical requirements of the radiation conditions taken into account.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 19, pp. 3–10, 1988.  相似文献   
76.
The classical Volterra model, equipped with the Faddeev-Takhtajan Poisson bracket provides a lattice version of the Virasoro algebra. The Volterra model being integrable, we can express the dynamical variables in terms of the so-called separated variables. Taking the continuum limit of these formulae, we obtain the Virasoro generators written as determinants of infinite matrices, the elements of which are constructed with a set of points lying on an infinite genus Riemann surface. The coordinates of these points are separated variables for an infinite set of Poisson commuting quantities including L 0. The scaling limit of the eigenvector can also be calculated explicitly, so that the associated Schroedinger equation is in fact exactly solvable.  相似文献   
77.
78.
A convenient method of synthesis of 2-(methoxycarbonylmethylene)-substituted imidazolidines and imidazolidinium bromides, and also of bicyclic diazo compounds has been developed starting from methyl bromopropiolate and ethylenediamine and its derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1205–1208, September, 1991.  相似文献   
79.
We report an experimental observation of the influence of concentration of Er3+ ions in an Erbiumdoped silica fiber on the spectral characteristics of an erbium fiber laser. Our basic conclusion is that an increase of erbium concentration in the fiber results in the laser optical spectrum narrowing. We also discuss possible mechanisms responsible for this effect.  相似文献   
80.
We propose a scheme to obtain the distance of two identical atoms placed inside the standing wave field by monitoring the collective resonance fluorescence spectrum emitted by the two particles. We find three different parameter ranges, depending on the distance of the atoms as compared to the transition wavelength. For large interparticle distances, dipole-dipole coupling is negligible, and the main system evolution arises from the interaction with the standing wave field. In the small-distance limit, the dynamics is dominated by the dipole-dipole interaction. Finally, in the intermediate region, a rich interplay of the various couplings arises, which however is lifted for strong driving laser fields. The present measurement procedure allows us to distinguish the three cases. In each of the cases, we show how to determine the distance of the two particles and their respective positions relative to the nodes of the standing wave field with fractional-wavelength precision.  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