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   344353篇
  免费   1806篇
  国内免费   424篇
化学   160781篇
晶体学   5284篇
力学   19193篇
综合类   3篇
数学   47787篇
物理学   113535篇
  2021年   3472篇
  2020年   3788篇
  2019年   4621篇
  2018年   6811篇
  2017年   7025篇
  2016年   8837篇
  2015年   4062篇
  2014年   7660篇
  2013年   14067篇
  2012年   11759篇
  2011年   13628篇
  2010年   11304篇
  2009年   11477篇
  2008年   13108篇
  2007年   12809篇
  2006年   11596篇
  2005年   10004篇
  2004年   9629篇
  2003年   8982篇
  2002年   9202篇
  2001年   9037篇
  2000年   7070篇
  1999年   5295篇
  1998年   5013篇
  1997年   4797篇
  1996年   4307篇
  1995年   3824篇
  1994年   3881篇
  1993年   3885篇
  1992年   3950篇
  1991年   4395篇
  1990年   4311篇
  1989年   4353篇
  1988年   4058篇
  1987年   4072篇
  1986年   3803篇
  1985年   4435篇
  1984年   4750篇
  1983年   4051篇
  1982年   4273篇
  1981年   3902篇
  1980年   3628篇
  1979年   4128篇
  1978年   4315篇
  1977年   4501篇
  1976年   4468篇
  1975年   4211篇
  1974年   4075篇
  1973年   4237篇
  1972年   3546篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
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   
102.
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   
103.
104.
The luminescence and scintillation properties of poly(methyl methacrylate) containing 1,1,3-trimethyl-3-phenylindan were studied.  相似文献   
105.
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   
106.
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   
107.
108.
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   
109.
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   
110.
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