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   307175篇
  免费   1614篇
  国内免费   626篇
化学   141594篇
晶体学   4707篇
力学   17739篇
综合类   20篇
数学   43873篇
物理学   101482篇
  2021年   3205篇
  2020年   3556篇
  2019年   4375篇
  2018年   6409篇
  2017年   6600篇
  2016年   8178篇
  2015年   3692篇
  2014年   7107篇
  2013年   12392篇
  2012年   10395篇
  2011年   12063篇
  2010年   10275篇
  2009年   10398篇
  2008年   11694篇
  2007年   11485篇
  2006年   10190篇
  2005年   8809篇
  2004年   8532篇
  2003年   7994篇
  2002年   8301篇
  2001年   7887篇
  2000年   6188篇
  1999年   4614篇
  1998年   4384篇
  1997年   4230篇
  1996年   3845篇
  1995年   3394篇
  1994年   3448篇
  1993年   3478篇
  1992年   3493篇
  1991年   3902篇
  1990年   3898篇
  1989年   3923篇
  1988年   3636篇
  1987年   3727篇
  1986年   3423篇
  1985年   3974篇
  1984年   4210篇
  1983年   3603篇
  1982年   3810篇
  1981年   3459篇
  1980年   3238篇
  1979年   3746篇
  1978年   3832篇
  1977年   3994篇
  1976年   4103篇
  1975年   3835篇
  1974年   3710篇
  1973年   3866篇
  1972年   3357篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
61.
62.
The behavior of real disperse systems with organic impurities was examined under conditions of destabilization by inorganic coagulants. A number of physicochemical methods of analysis and a simulation method were used to identify the character and type of the complexes formed and to calculate their stability constants.  相似文献   
63.
A standard model Lagrangian is constructed making the pseudo-Finsleroid generalization of the Yang-Mills field equation by the conformal method. The Higgs field potential is suggested that ensures generation of particle masses caused by the spontaneous symmetry breaking. After transition to the conformal coordinates, the expressions obtained assume the standard form that in many cases allows the results of pseudo-Euclidean theory to be used in calculations of the Feynman diagrams. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 44–51, April, 2006.  相似文献   
64.
65.
The luminescence and scintillation properties of poly(methyl methacrylate) containing 1,1,3-trimethyl-3-phenylindan were studied.  相似文献   
66.
It is proved that a Galois extension of a field of characteristic p is completely determined by its Galois group and the endomorphism of the additive group of the group algebra that corresponds to the raising to the power p.  相似文献   
67.
68.
For a planar convex set K with C 2-smooth boundary, the area of the set of the points lying on a given number of affine diameters of K is estimated. As a corollary, it is proved that the area of K is at most pM2 /4\pi M^2 /4 , where M is the largest length of a chord of K halving the area of K. Bibliography: 2 titles.  相似文献   
69.
Multimode triggered optical superradiance due to a two-photon transition is theoretically studied. Kinetic equations are derived for the dynamics of cooperative development of coherence and population inversion of optical centers interacting with each other through a common field of emitted photons. Various regimes of triggering of optical superradiance due to a two-photon transition are considered. The possibility of creating a quantum photomultiplier on the basis of the triggered optical superradiance is discussed.  相似文献   
70.
The process of focusing of an inhomogeneously polarized beam passed through a system consisting of a uniaxial crystal and a polarization filter is considered. It is shown that the action of this system is equivalent to the action of a phase transparency with a complex relief of the refractive index. In particular, if the angle between the axes of the quarter-wave plate and the polarizer is equal to 45°, this transparency has a helicoidal relief. Simultaneously, two singular beams with different curvatures of their wavefronts arise in the transparency. The action of the lens consists in formation of a combined singular beam having three focal waists. The boundary wave arising upon focusing is able not only to form a new spectrum of toroidal vortices, but also to straighten the focusing region, forming a fairly extended range with a weak divergence.  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