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   113705篇
  免费   6130篇
  国内免费   4922篇
化学   49968篇
晶体学   1209篇
力学   8744篇
综合类   331篇
数学   35710篇
物理学   28795篇
  2024年   104篇
  2023年   715篇
  2022年   1268篇
  2021年   1393篇
  2020年   1455篇
  2019年   1505篇
  2018年   11371篇
  2017年   11208篇
  2016年   7612篇
  2015年   2622篇
  2014年   2356篇
  2013年   3015篇
  2012年   6868篇
  2011年   13595篇
  2010年   7769篇
  2009年   8159篇
  2008年   8906篇
  2007年   10761篇
  2006年   2196篇
  2005年   2875篇
  2004年   2818篇
  2003年   3019篇
  2002年   2094篇
  2001年   1075篇
  2000年   1046篇
  1999年   949篇
  1998年   864篇
  1997年   779篇
  1996年   857篇
  1995年   652篇
  1994年   601篇
  1993年   519篇
  1992年   403篇
  1991年   394篇
  1990年   294篇
  1989年   264篇
  1988年   246篇
  1987年   194篇
  1986年   189篇
  1985年   177篇
  1984年   128篇
  1983年   103篇
  1982年   103篇
  1981年   76篇
  1980年   80篇
  1979年   68篇
  1978年   50篇
  1914年   45篇
  1909年   41篇
  1908年   40篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
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   
53.
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   
54.
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   
55.
56.
Mo2Ni3Si/NiSi metal silicide composite coatings with a fine microstructure consisting of Mo2Ni3Si primary dendrites and the interdendritic Mo2Ni3Si/NiSi eutectics were fabricated on austenitic stainless steel AISI 321 by laser cladding process. Small amplitude reciprocating sliding wear resistance of the coatings is evaluated as functions of normal load and slip amplitude and the wear mechanisms were discussed based on worn surface morphology observations. Results showed that the Mo2Ni3Si/NiSi coatings have excellent small amplitude reciprocating sliding wear resistance.  相似文献   
57.
58.
物理模型教学与创新能力的培养   总被引:1,自引:0,他引:1  
现代教学以能力培养为重点.学生获得研究问题、探索问题的能力是十分重要的,物理模型的教学过程对培养学生研究问题、探索问题、发展创造思维、培养辩证唯物主义思想方法都极为有利,因此,必须重视物理模型教学.  相似文献   
59.
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   
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