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   78043篇
  免费   568篇
  国内免费   114篇
化学   41601篇
晶体学   1262篇
力学   3281篇
综合类   1篇
数学   7837篇
物理学   24743篇
  2022年   631篇
  2021年   871篇
  2020年   972篇
  2019年   1106篇
  2018年   1597篇
  2017年   1686篇
  2016年   2152篇
  2015年   1026篇
  2014年   1734篇
  2013年   3302篇
  2012年   2921篇
  2011年   3306篇
  2010年   2647篇
  2009年   2645篇
  2008年   3015篇
  2007年   2902篇
  2006年   2786篇
  2005年   2455篇
  2004年   2256篇
  2003年   2085篇
  2002年   2145篇
  2001年   2243篇
  2000年   1638篇
  1999年   1258篇
  1998年   1128篇
  1997年   1039篇
  1996年   892篇
  1995年   838篇
  1994年   815篇
  1993年   816篇
  1992年   870篇
  1991年   943篇
  1990年   884篇
  1989年   908篇
  1988年   823篇
  1987年   771篇
  1986年   741篇
  1985年   866篇
  1984年   964篇
  1983年   818篇
  1982年   838篇
  1981年   747篇
  1980年   702篇
  1979年   770篇
  1978年   896篇
  1977年   917篇
  1976年   809篇
  1975年   774篇
  1974年   793篇
  1973年   762篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
In this paper, we describe an aircraft loading problem submitted by the French military agency (DGA) as part of a more general military airlift planning problem. It can be viewed as a kind of bi-dimensional bin-packing problem, with heterogeneous bins and several additional constraints. We introduce two-phase methods for solving this NP-hard problem. The first phase consists in building good initial solutions, thanks to two fast algorithms: a list-based heuristic and a loading pattern generation method. Both algorithms call a constraint-based subroutine, able to determine quickly if the items already loaded can be reshuffled to accommodate a new object. The second phase improves these preliminary solutions using local search techniques. Results obtained on real data sets are presented.  相似文献   
95.
Amplitude equations, as well as the effective dispersion and nonlinearity parameters, which define the dynamics of a wave packet formed by two strongly coupled modes, are derived with allowance for the frequency dependence of the linear mode coupling coefficient. These equations are used to study the onset of the modulation instability of the two-mode wave packet, soliton-like pulses, and compression modes. Unlike single-mode systems, the last two effects in optical waveguides may arise for both a negative and positive disper-sion of the waveguide material.  相似文献   
96.
In the paper we describe automorphisms and derivations of simple Lie algebras of family R. The Lie algebra of the automorphism group is found. Bibliography: 11 titles.__________Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 305, 2003, pp. 165–186.  相似文献   
97.
It is shown that the three-dimensional Navier-Stokes equation for incompressible fluid can be represented as an equation including only quaternions as co-ordinate operators and variables. Only the quaternion operations such as a quaternion product and a quaternion conjugation over these variables are used.  相似文献   
98.
Data on methods for the production of isatin and indole aldoximes, ketoximes, and amidoximes and their reactions are reviewed. Individual syntheses of new heterocycles from indole and isatin oximes are discussed. The principal results from investigation of the biological activity of derivatives of the oximes are also presented.  相似文献   
99.
The influence of ultrasonic shock treatment on variation in the pearlite structure and properties is studied in the surface layer of carburized steel. It is shown that plastic deformation results in carbon redistribution and formation of new phases.  相似文献   
100.
The PARRNe facility has been used to produce neutron-rich isotopes 83,84Gaby the ISOL method. Their decay has been studied, and β-γ coincidence and γ-γ coincidence data were collected as a function of time. The first two excited levels in 83Ge and the first excited level in 84Ge have been measured for the first time.  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