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   573141篇
  免费   5766篇
  国内免费   1597篇
化学   302496篇
晶体学   8654篇
力学   26798篇
综合类   22篇
数学   68069篇
物理学   174465篇
  2021年   5030篇
  2020年   5412篇
  2019年   6132篇
  2018年   8179篇
  2017年   8071篇
  2016年   11876篇
  2015年   7125篇
  2014年   11360篇
  2013年   26065篇
  2012年   20159篇
  2011年   24459篇
  2010年   17850篇
  2009年   17832篇
  2008年   22738篇
  2007年   22568篇
  2006年   20667篇
  2005年   18500篇
  2004年   17201篇
  2003年   15254篇
  2002年   15206篇
  2001年   16928篇
  2000年   12816篇
  1999年   10019篇
  1998年   8299篇
  1997年   8149篇
  1996年   7809篇
  1995年   7027篇
  1994年   7000篇
  1993年   6746篇
  1992年   7564篇
  1991年   7730篇
  1990年   7372篇
  1989年   7248篇
  1988年   7210篇
  1987年   7075篇
  1986年   6694篇
  1985年   8661篇
  1984年   8867篇
  1983年   7132篇
  1982年   7223篇
  1981年   7147篇
  1980年   6624篇
  1979年   7271篇
  1978年   7403篇
  1977年   7446篇
  1976年   7391篇
  1975年   6820篇
  1974年   6725篇
  1973年   6869篇
  1972年   4972篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
In the article, it is proved that any nonnegative solution of an elliptic quasilinear inequality that vanishes on a subset of positive measure is trivial. __________ Translated from Trudy Seminara imeni I. G. Petrovskogo, No. 25, pp. 112–118, 2005.  相似文献   
132.
133.
This article deals with an expanded mixed finite element formulation, based on the Hu‐Washizu principle, for a nonlinear incompressible material in the plane. We follow our related previous works and introduce both the stress and the strain tensors as further unknowns, which yields a two‐fold saddle point operator equation as the corresponding variational formulation. A slight generalization of the classical Babu?ka‐Brezzi's theory is applied to prove unique solvability of the continuous and discrete formulations, and to derive the corresponding a priori error analysis. An extension of the well‐known PEERS space is used to define an stable associated Galerkin scheme. Finally, we provide an a posteriori error analysis based on the classical Bank‐Weiser approach. © 2002 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 18: 105–128, 2002  相似文献   
134.
Off-the-shell anomalous factors of the two-body Coulomb transition matrices appear in the integral form of the Faddeev second-order nuclear-electronic amplitude, for proton-hydrogen charge transfer scattering in a typical nlmnlm′ transition. A symmetric-impulse approximation (SIA) is applied to eliminate these factors and an induction method is proposed to analytically calculate the remaining integrals. The nuclear-electronic amplitude is derived for the general case, and for totally symmetric collisions, in terms of generalized hypergeometric functions of two variables, F 4, and of one variable, 3 F 2, respectively. The angular distribution of the second-order nuclear-electronic charge transfer amplitude shows the Thomas mechanism as a peak or a hump for symmetric and asymmetric collisions. There also exists a peak in the forward angular distribution of the second-order nuclear-electronic amplitude, which partly cancels the kinematic peak in the angular distribution of the charge transfer differential cross sections.  相似文献   
135.
136.
Specific features of the initiated oxidation of polyethylene and its low-molecular-weight analogue tridecane, associated with the occurrence of the process in the short-chain mode, were studied.  相似文献   
137.
138.
139.
The thermal and dielectric behaviors of poly(vinylidene fluoride-trifluoroethylene) copolymers near the ferroelectric-to-paraelectric phase transition are investigated for samples with 20, 25, 30, and 40 mol% trifluoroethylene (TrFE). The data suggest that the transition becomes continuous for a particular composition near 50 mol% TrFE. Experimental data are sensitive to thermal history (kinetics of crystallization, and kinetics and cycling over the structural transition). It is found that several anomalies are present at the structural change, and in particular the 30 mol% TrFE sample shows the most marked anomalies. These phenomena can be attributed to defects, but another possibility would be the existence of an intemediate supplementary phase. Both hypotheses are discussed.  相似文献   
140.
In recent years there has emerged significant interest in low pressure radio frequency (rf) glow discharges which are used widely particulary in IC fabrication. Various parameters of the rf glow discharge have been found to be useful for its electrical characterization; however, there is no uniformity and agreement. Extensive experimental investigations on various discharge systems have shown, that the self-bias on the rf driven electrode, the complex conductivity and the breakdown characteristic are preferable parameters of rf discharges. Advantageously the self-bias and the complex conductivity should be presented in dependence on the pressure and the applied rf voltage. The discharge current cannot be measured quite accurately due to currents via leaky capacitors and the deviations from a sinusoidal form of the current due to nonlinearities.  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