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   214679篇
  免费   16545篇
  国内免费   561篇
化学   141144篇
晶体学   3074篇
力学   9074篇
综合类   3篇
数学   22074篇
物理学   56416篇
  2023年   4228篇
  2022年   2255篇
  2021年   3580篇
  2020年   5816篇
  2019年   3731篇
  2018年   4165篇
  2017年   2629篇
  2016年   8482篇
  2015年   7155篇
  2014年   7830篇
  2013年   12570篇
  2012年   8817篇
  2011年   7866篇
  2010年   8274篇
  2009年   8189篇
  2008年   7500篇
  2007年   7132篇
  2006年   6168篇
  2005年   5566篇
  2004年   5132篇
  2003年   4630篇
  2002年   4480篇
  2001年   5251篇
  2000年   3878篇
  1999年   2991篇
  1998年   2502篇
  1997年   2463篇
  1996年   2310篇
  1995年   2239篇
  1994年   2164篇
  1993年   2201篇
  1992年   2389篇
  1991年   2305篇
  1990年   2244篇
  1989年   2193篇
  1988年   2224篇
  1987年   2216篇
  1985年   2716篇
  1984年   2784篇
  1983年   2477篇
  1982年   2614篇
  1981年   2455篇
  1980年   2462篇
  1979年   2597篇
  1978年   2641篇
  1977年   2686篇
  1976年   2784篇
  1975年   2801篇
  1974年   2764篇
  1973年   2772篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
51.
52.
In this paper, we study the consistency of a variant of fractionalstep Runge–Kutta methods. These methods are designed tointegrate efficiently semi-linear multidimensional parabolicproblems by means of linearly implicit time integration processes.Such time discretization procedures are also related to a splittingof the space differential operator (or the spatial discretizationof it) as a sum of ‘simpler’ linear differentialoperators and a nonlinear term.  相似文献   
53.
54.
The sub-millisecond protonation dynamics of the chromophore in S65T mutant form of the green fluorescent protein (GFP) was tracked after a rapid pH jump following laser-induced proton release from the caged photolabile compoundo-nitrobenzaldehyde. Following a jump in pH from 8 to 5 (which is achieved within 2 μs), the fluorescence of S65T GFP decreased as a single exponential with a time constant of ∼90 μs. This decay is interpreted as the conversion of the deprotonated fluorescent GFP chromophore to a protonated non-fluorescent species. The protonation kinetics showed dependence on the bulk viscosity of the solvent, and therefore implicates bulk solvent-controlled protein dynamics in the protonation process. The protonation is proposed to be a sequential process involving two steps: (a) proton transfer from solvent to the chromophore, and (b) internal structural rearrangements to stabilize a protonated chromophore. The possible implications of these observations to protein dynamics in general is discussed  相似文献   
55.
56.
57.
B. Ananthanarayan 《Pramana》2003,61(5):911-920
A review of chiral perturbation theory and recent developments on the comparison of its predictions with experiment is presented. Some interesting topics with scope for further elaboration are touched upon.  相似文献   
58.
The European Physical Journal E - Recently, the chain dynamics of molten polymers in confined geometries has been investigated, using NMR. Some of these experiments have been performed on...  相似文献   
59.
We construct an integral Newton-type interpolation polynomial with a continual set of nodes. This interpolant is unique and preserves an operator polynomial of the corresponding degree.  相似文献   
60.
Relaxor properties of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) and non-lead perovskite thin films have been analysed in terms of large frequency dispersion of dielectric response at low temperatures. A wide spectrum of dielectric relaxation was observed in the frequency-dependent response of the imaginary part of the dielectric permittivity. Transformation from normal ferroelectric to relaxor behaviour has been observed in the case of the Ca substituting the BaTiO3 thin films. A number of techniques were exploited to investigate the wide spectrum of relaxation times in pulsed laser ablated thin films.ac anddc electric field induced complex dielectric properties of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) thin films were studied as function of frequencies at different temperatures. Nonlinear behaviour of dielectric susceptibility with respect to the amplitude of theac drive was observed at lower temperatures. The frequency dependence of transition temperatureT m (temperature of the maximum of dielectric constant) was studied using the Vogel-Fulcher relation. Dedicated to Professor C N R Rao on his 70th birthday  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