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   92968篇
  免费   1055篇
  国内免费   514篇
化学   34549篇
晶体学   883篇
力学   7115篇
数学   34466篇
物理学   17524篇
  2023年   140篇
  2022年   255篇
  2021年   330篇
  2020年   402篇
  2019年   387篇
  2018年   10600篇
  2017年   10403篇
  2016年   6611篇
  2015年   1304篇
  2014年   841篇
  2013年   1162篇
  2012年   4841篇
  2011年   11688篇
  2010年   6249篇
  2009年   6571篇
  2008年   7490篇
  2007年   9608篇
  2006年   1130篇
  2005年   2113篇
  2004年   2227篇
  2003年   2446篇
  2002年   1512篇
  2001年   416篇
  2000年   427篇
  1999年   299篇
  1998年   306篇
  1997年   271篇
  1996年   363篇
  1995年   220篇
  1994年   186篇
  1993年   213篇
  1992年   140篇
  1991年   155篇
  1990年   120篇
  1989年   130篇
  1988年   142篇
  1987年   129篇
  1986年   127篇
  1985年   145篇
  1984年   146篇
  1983年   97篇
  1982年   156篇
  1981年   160篇
  1980年   143篇
  1979年   127篇
  1978年   147篇
  1977年   110篇
  1976年   89篇
  1975年   87篇
  1973年   93篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
41.
It is explicitly shown that if phase transition occurs at the core of a newborn neutron star with moderately strong magnetic field strength, which populates only the electron’s Landau levels, then in the β -equilibrium condition, the quark core is energetically much more unstable than the neutron matter of identical physical condition.  相似文献   
42.
Basic ideas and results which characterize quantum diffusion of defects in quantum crystals like solid helium as a new phenomenon are presented. Quantum effects in such media lead to a delocalization of point defects (vacancies, impurities etc.) and they turn into quasiparticles of a new type—defectons, which are characterized not by their position in the crystal lattice but by their quasimomentum and dispersion law. Defecton-defecton and defecton-phonon scattering are considered and an interpolation formula for the diffusion coefficient valid in all interesting temperature and concentration regions is presented. A comparison with the experimental data is made. Some alternative points of view are discussed in detail and the inconsistency of the Kisvarsanyi-Sullivan theory is shown.  相似文献   
43.
In this paper we obtain a number of Maharam-type slice integral representations, with respect to scalar measures, for positive projections in Dedekind complete vector lattices and f-algebras. AMS Classification: 47B65, 46A40, 06F25  相似文献   
44.
We define analytic functions within Clifford Algebras CL, and study their trigonometric properties. We write the addition formulas when their arguments, A and B in CL, commute, this generalizes ordinary trigonometry. We examine in particular the case A2 = 1.   相似文献   
45.
In the present paper it is shown that if S1 and S2 are two Clifford topological semigroups satisfying certain conditions and T is an isometric isomorphism of LUC(S1*) onto LUC(S2*), then T maps S1 topologically isomorphically onto S2. Furthermore, T maps M l n(S1) (M(S1), respectively) isometrically isomorphically onto M l n(S2) (M(S2), respectively). Indeed, we have obtained a generalization of a well-known result of Ghahramani, Lau and Losert for locally compact groups to a more general setting of Clifford topological semigroups.  相似文献   
46.
We study the relation between the cohomology of general linear and symmetric groups and their respective quantizations, using Schur algebras and standard homological techniques to build appropriate spectral sequences. As our methods fit inside a much more general context within the theory of finite-dimensional algebras, we develop our results first in that general setting, and then specialize to the above situations. From this we obtain new proofs of several known results in modular representation theory of symmetric groups. Moreover, we reduce certain questions about computing extensions for symmetric groups and Hecke algebras to questions about extensions for general linear groups and their quantizations.  相似文献   
47.
This paper describes some work carried out in the Scientific Research and Development Branch (SRDB) of the Home Office, intended to contribute to an overall aim of building up internal expertise in the field of expert systems. This was done by carrying out a number of pilot and demonstrator projects, two of which are described in some detail. The plan, which proved successful, was to build as far as possible on the relevant skills already possessed by an OR group in the branch. The lessons learned from these are summarized in the hope that they will be of use to other groups who wish to become involved in this important area.  相似文献   
48.
49.
50.
What strategy should a football (soccer, in American parlance) club adopt when deciding whether to sack its manager? This paper introduces a simple model assuming that a club's objective is to maximize the number of league points that it scores per season. The club's strategy consists of three choices: the length of the honeymoon period during which it will not consider sacking a new manager, the level of the performance trapdoor below which the manager get the sack, and the weight that it will give to more recent games compared to earlier ones. Some data from the last six seasons of the English Premiership are used to calibrate the model. At this early stage of the research, the best strategy appears to have only a short honeymoon period of eight games (much less than the actual shortest period of 12 games), to set the trapdoor at 0.74 points per game, and to put 47% of the weight on the last five games. A club adopting this strategy would obtain on average 56.8 points per season, compared to a Premiership average of 51.8 points.  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