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   180751篇
  免费   1838篇
  国内免费   553篇
化学   94061篇
晶体学   3082篇
力学   7425篇
综合类   3篇
数学   21289篇
物理学   57282篇
  2020年   1550篇
  2019年   1705篇
  2018年   2138篇
  2017年   2225篇
  2016年   3439篇
  2015年   2158篇
  2014年   3384篇
  2013年   8206篇
  2012年   6363篇
  2011年   7550篇
  2010年   5398篇
  2009年   5335篇
  2008年   7053篇
  2007年   6943篇
  2006年   6591篇
  2005年   5992篇
  2004年   5486篇
  2003年   4955篇
  2002年   4734篇
  2001年   5407篇
  2000年   3990篇
  1999年   3069篇
  1998年   2562篇
  1997年   2468篇
  1996年   2312篇
  1995年   2184篇
  1994年   2162篇
  1993年   2048篇
  1992年   2362篇
  1991年   2304篇
  1990年   2247篇
  1989年   2184篇
  1988年   2178篇
  1987年   2171篇
  1986年   2065篇
  1985年   2699篇
  1984年   2786篇
  1983年   2445篇
  1982年   2579篇
  1981年   2376篇
  1980年   2351篇
  1979年   2493篇
  1978年   2536篇
  1977年   2466篇
  1976年   2498篇
  1975年   2417篇
  1974年   2386篇
  1973年   2565篇
  1972年   1652篇
  1971年   1359篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
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   
52.
53.
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   
54.
55.
56.
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   
57.
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   
58.
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   
59.
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   
60.
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