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   382247篇
  免费   1926篇
  国内免费   1000篇
化学   164361篇
晶体学   5461篇
力学   24330篇
综合类   20篇
数学   75160篇
物理学   115841篇
  2021年   3204篇
  2020年   3556篇
  2019年   4372篇
  2018年   16565篇
  2017年   16480篇
  2016年   14038篇
  2015年   4498篇
  2014年   7377篇
  2013年   12670篇
  2012年   14002篇
  2011年   22158篇
  2010年   15709篇
  2009年   16248篇
  2008年   18078篇
  2007年   19913篇
  2006年   10372篇
  2005年   10035篇
  2004年   9981篇
  2003年   9898篇
  2002年   9264篇
  2001年   8111篇
  2000年   6461篇
  1999年   4757篇
  1998年   4555篇
  1997年   4367篇
  1996年   4028篇
  1995年   3507篇
  1994年   3521篇
  1993年   3568篇
  1992年   3545篇
  1991年   3962篇
  1990年   3947篇
  1989年   3981篇
  1988年   3693篇
  1987年   3782篇
  1986年   3480篇
  1985年   4019篇
  1984年   4251篇
  1983年   3638篇
  1982年   3851篇
  1981年   3496篇
  1980年   3283篇
  1979年   3789篇
  1978年   3866篇
  1977年   4012篇
  1976年   4119篇
  1975年   3851篇
  1974年   3719篇
  1973年   3890篇
  1972年   3374篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
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   
102.
103.
The luminescence and scintillation properties of poly(methyl methacrylate) containing 1,1,3-trimethyl-3-phenylindan were studied.  相似文献   
104.
In this paper, we find the approximate solution of a second order nonlinear partial differential equation on a simple connected region inR 2. We transfer this problem to a new problem of second order nonlinear partial differential equation on a rectangle. Then, we transformed the later one to an equivalent optimization problem. Then we consider the optimization problem as a distributed parameter system with artificial controls. Finally, by using the theory of measure, we obtain the approximate solution of the original problem. In this paper also the global error inL 1 is controlled.  相似文献   
105.
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   
106.
107.
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   
108.
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   
109.
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   
110.
Optics and Spectroscopy - The fluorescence of the nematic liquid crystal n-butyl-n′-methoxyazoxybenzene (BMAOB) in the form of a layer and in porous glasses with pores of different diameter...  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