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   82903篇
  免费   634篇
  国内免费   132篇
化学   44899篇
晶体学   1329篇
力学   3350篇
综合类   1篇
数学   8052篇
物理学   26038篇
  2022年   658篇
  2021年   900篇
  2020年   1019篇
  2019年   1164篇
  2018年   1646篇
  2017年   1720篇
  2016年   2227篇
  2015年   1107篇
  2014年   1830篇
  2013年   3512篇
  2012年   3136篇
  2011年   3531篇
  2010年   2786篇
  2009年   2785篇
  2008年   3270篇
  2007年   3105篇
  2006年   3019篇
  2005年   2671篇
  2004年   2470篇
  2003年   2254篇
  2002年   2325篇
  2001年   2371篇
  2000年   1777篇
  1999年   1335篇
  1998年   1182篇
  1997年   1095篇
  1996年   948篇
  1995年   873篇
  1994年   877篇
  1993年   900篇
  1992年   955篇
  1991年   1005篇
  1990年   939篇
  1989年   960篇
  1988年   888篇
  1987年   840篇
  1986年   813篇
  1985年   968篇
  1984年   1052篇
  1983年   857篇
  1982年   903篇
  1981年   820篇
  1980年   766篇
  1979年   825篇
  1978年   941篇
  1977年   976篇
  1976年   858篇
  1975年   812篇
  1974年   838篇
  1973年   790篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Kinetic parameters of amino acid cations in an MK-40 ion-exchange membrane are calculated from the conductivity data. A theoretical quantum-chemical analysis of experimental activation energies for conduction suggests a mechanism of elementary act of transport of amino acid cations in the membrane.  相似文献   
102.
We introduce extensions of the Mangasarian-Fromovitz and Abadie constraint qualifications to nonsmooth optimization problems with feasibility given by means of lower-level sets. We do not assume directional differentiability, but only upper semicontinuity of the defining functions. By deriving and reviewing primal first-order optimality conditions for nonsmooth problems, we motivate the formulations of the constraint qualifications. Then, we study their interrelation, and we show how they are related to the Slater condition for nonsmooth convex problems, to nonsmooth reverse-convex problems, to the stability of parametric feasible set mappings, and to alternative theorems for the derivation of dual first-order optimality conditions.In the literature on general semi-infinite programming problems, a number of formally different extensions of the Mangasarian-Fromovitz constraint qualification have been introduced recently under different structural assumptions. We show that all these extensions are unified by the constraint qualification presented here.  相似文献   
103.
The aim of the paper is to present and substantiate a technique to visualize DEA modelling results without any loss of mathematical rigour. The proposed family of parametric optimization methods allows one to construct an intersection of the multidimensional frontier with a two-dimensional plane determined by any pair of given directions. This approach reduces the efficiency analysis of production units to the investigation of well-known functions in economics. We also propose constructive methods to calculate marginal rates of substitution, marginal rates of transformation and so on.  相似文献   
104.
105.
106.
The operating principles, design, and characteristics of an ion source with a cold magnetron cathode and magnetic plasma compression are described. The source is intended for the injector of a linear proton accelerator.  相似文献   
107.
Some boundary properties of nonparametric surfaces with finite area are proved.  相似文献   
108.
109.
We investigate a new interpretation for the Navier-Stokes corrections to the hydrodynamic equation of asymmetric interacting particle systems. We consider a system that starts from a measure associated with a profile that is constant along the drift direction. We show that under diffusive scaling the macroscopic behavior of the process is described by a nonlinear parabolic equation whose diffusion coefficient coincides with the diffusion coefficient of the hydrodynamic equation of the symmetric version of the process.  相似文献   
110.
Results of experimental investigations of the volt-brightness characteristics, frequency dependences of brightness, and the directional radiation pattern of electroluminescent MSDM, MSCM, and MSDCM emitters, where M stands for the first transparent and second nontransparent electrodes, S is a semiconductor, D is a thin-film dielectric, and C is a silicone-based composite liquid dielectric with a powdered segnetoelectric filler, developed on conventional “smooth” and rough glass substrates are presented. It is shown that electroluminescent structures on rough surfaces have a brightness approximately two times higher than that of similar structures developed on a “smooth” substrate. Ul’yanovsk State University, 42, L. Tolstoi St., Ul’yanovsk, 432700, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 4, pp. 507–512, July–August, 1997.  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