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   519477篇
  免费   3618篇
  国内免费   809篇
化学   244024篇
晶体学   8028篇
力学   28553篇
综合类   14篇
数学   77084篇
物理学   166201篇
  2021年   4097篇
  2020年   4637篇
  2019年   5508篇
  2018年   12678篇
  2017年   13157篇
  2016年   12835篇
  2015年   5618篇
  2014年   9539篇
  2013年   19617篇
  2012年   17997篇
  2011年   25878篇
  2010年   18530篇
  2009年   18852篇
  2008年   23511篇
  2007年   25563篇
  2006年   15379篇
  2005年   16772篇
  2004年   14370篇
  2003年   13891篇
  2002年   12836篇
  2001年   12881篇
  2000年   10169篇
  1999年   7492篇
  1998年   6544篇
  1997年   6380篇
  1996年   6070篇
  1995年   5467篇
  1994年   5428篇
  1993年   5294篇
  1992年   5910篇
  1991年   6158篇
  1990年   6083篇
  1989年   6091篇
  1988年   5849篇
  1987年   5919篇
  1986年   5521篇
  1985年   6688篇
  1984年   6966篇
  1983年   5733篇
  1982年   5986篇
  1981年   5744篇
  1980年   5365篇
  1979年   6157篇
  1978年   6197篇
  1977年   6356篇
  1976年   6285篇
  1975年   5775篇
  1974年   5684篇
  1973年   5770篇
  1972年   4583篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The final stage of self-focusing of 500-ps pulses of a neodymium laser in silicate and phosphate glasses and in the nonlinear liquids perfluorooctane, benzene, and toluene is studied theoretically and experimentally. The formation of spatial solitons, which are stable due to the nonlinearity saturation, is demonstrated. It is found that the intensity of the nonlinearity saturation is close to that of the threshold breakdown for glasses and the role of stimulated Raman scattering is significant for liquids.  相似文献   
992.
A self-consistent, completely quantum calculation of the structure of the inner crust of neutron stars is carried out in the Wigner-Seitz approximation with a realistic phenomenological nuclear energy functional, where pair correlations of neutrons and protons are included in the explicit form. It has been shown that the superfluidity of neutrons and protons affects the structure of the ground state of the crust.  相似文献   
993.
Journal of Statistical Physics - We study high-energy asymptotics of the steady velocity distributions for model kinetic equations describing various regimes in dilute granular flows. The main...  相似文献   
994.
The kinetics of formation and relaxation of transient holographic gratings recorded in a system of saturable three-level centers is studied. Distortions in the shape of the profile of recorded and decaying structures of population and of the refractive index are taken into account. The analysis of the time dependences of diffraction efficiencies of different orders is performed for phase (thermal) and amplitude (concentration) gratings.  相似文献   
995.
We examine several interesting relationships and expressions involving Fourier-Feynman transform, convolution product and first variation for functionals in the Fresnel class F(B) of an abstract Wiener space B. We also prove a translation theorem and Parseval's identity for the analytic Feynman integral. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   
996.
997.
998.
A sequential scheme for calculating the polarizability of a pair of parallel cylinders with an arbitrary (but fairly symmetric) form is suggested. An infinite set of algebraic equations is derived for coefficients involved in an expression for the potential. The numerical solution of this set makes it possible to find the polarizability with any degree of accuracy. This method is unrelated to the cylinder shape. The electrostatic properties of the cylinders are described in terms of the multipolar polarizability matrix.  相似文献   
999.
The structure of bis-(2,3-pentamethylene-3,4-dihydro-4-oxoquinazolinium) tetrachlorocuprate (II) sesquihydrate, (C13H15N2O)2[CuCl4]·1.5H2O, was determined by single crystal X-ray diffraction. In contrast to the previously studied analogs, the compound contains crystallization water molecules.Original Russian Text Copyright © 2004 by K. K. Turgunov, B. Tashkhodzhaev, L. V. Molchanov, and Kh. M. Shakhidoyatov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 955–959, September–October, 2004.  相似文献   
1000.
Hexaphyrin(1.0.1.0.0.0) (isoamethyrin) undergoes a significant color change in the presence of UO22+, PuO22+, and NpO22+. The complexation of the first of these dioxo actinide cations was studied in semi-quantitative fashion in 1:1 MeOH-CH2Cl2. Under these conditions, the detection limit for UO22+ was found to be ca. 5.8 ppm by naked eye monitoring and <28 ppb by UV-vis spectroscopy. Isoamethyrin does not undergo a color change in the presence of most transition metals or when exposed to Gd(III). Isoamethyrin thus constitutes an attractive alternative to 2,2′(1,8-dihydroxy-3,6-disulfonaphthylene-2,7-bisazo)-bisbenzenarsonic acid (AzIII) and 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol (BrPADAP), systems currently used as actinide cation sensors.  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