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   314326篇
  免费   3753篇
  国内免费   1091篇
化学   170607篇
晶体学   4457篇
力学   13029篇
综合类   7篇
数学   36262篇
物理学   94808篇
  2020年   1983篇
  2019年   1954篇
  2018年   1965篇
  2017年   1875篇
  2016年   3858篇
  2015年   3235篇
  2014年   4422篇
  2013年   13976篇
  2012年   10728篇
  2011年   13363篇
  2010年   8270篇
  2009年   8255篇
  2008年   12335篇
  2007年   12571篇
  2006年   12212篇
  2005年   11154篇
  2004年   10034篇
  2003年   8848篇
  2002年   8700篇
  2001年   10109篇
  2000年   7710篇
  1999年   6115篇
  1998年   4894篇
  1997年   4733篇
  1996年   4773篇
  1995年   4363篇
  1994年   4114篇
  1993年   3940篇
  1992年   4431篇
  1991年   4293篇
  1990年   4011篇
  1989年   3830篇
  1988年   4120篇
  1987年   3784篇
  1986年   3677篇
  1985年   5317篇
  1984年   5395篇
  1983年   4377篇
  1982年   4753篇
  1981年   4793篇
  1980年   4545篇
  1979年   4663篇
  1978年   4665篇
  1977年   4644篇
  1976年   4597篇
  1975年   4508篇
  1974年   4356篇
  1973年   4524篇
  1972年   2569篇
  1971年   1879篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
902.
The effect of angular momentum on the competition between fission and particle emission during light system fission process was studied via fission diffusion model. The prescission particle multiplicities were found to increase with decreasing angular momentum. The experimental prescission proton and α particle multiplicities can be fitted for 10.6 MeV/nucleon 84Kr(27Al,binary fission) reaction with this model. Entrance channel effect found in [1] is proved to be angular momentum effect.  相似文献   
903.
It is shown that the non-trivial cocycles on simple Lie algebras may be used to introduce antisymmetric multibrackets which lead to higher-order Lie algebras, the definition of which is given. Their generalised Jacobi identities turn out to be satisfied by the antisymmetric tensors (or higher-order “structure constants”) which characterise the Lie algebra cocycles. This analysis allows us to present a classification of the higher-order simple Lie algebras as well as a constructive procedure for them. Our results are synthesised by the introduction of a single, complete BRST operator associated with each simple algebra. Received: 3 June 1996 / Accepted: 8 November 1996  相似文献   
904.
We give a simple proof that everyk-connected bipartite tournament has a cycle through every set ofk vertices. This was conjectured in [4].This research was done while the first author was visiting Laboratoire de Recherche en Informatique, universite Paris-Sud whose hospitality and financial support is gratefully acknowledged  相似文献   
905.
906.
Bharuth-Ram  K.  Butler  J. E.  Naidoo  D.  Klingelhofer  G. 《Hyperfine Interactions》2004,156(1-4):129-135
Hyperfine Interactions - Conversion electron Mössbauer spectroscopy measurements have been made on a diamond sample synthesized by chemical vapour deposition. The sample was implanted with 70...  相似文献   
907.
A class of long-range predictive adaptive fuzzy relational controllers is presented. The plant behavior is described over an extended time horizon by a fuzzy relational model which is identified based on input-output closed-loop observations of the plant variables. In this class of adaptive controllers the control law attempts to minimize a quadratic cost over an extended control horizon. When used with linear models, this approach has revealed a significant potential for overcoming the limitations of one-step ahead schemes, such as the stabilization of non-minimum phase plants. Here, a uniform framework is adopted for implementing both the fuzzy model and the fuzzy controller, namely distributed fuzzy relational structures gaining from their massive parallel processing features and from the learning capabilities typical of the connectivist approaches. Issues such as maintenance during the adaptation process of the meaning of linguistic terms used at both fuzzy systems interfaces are addressed, namely by introducing a new design methodology for on-line fuzzy systems interface adaptation. The examples presented reinforce the claim of the usefulness of this new approach.  相似文献   
908.
The effect of weak annihilation and u-quark penguin contribution on the branching ratio B→K1γ at next-to-leading order of αs are calculated using the LEET approach. It is shown that the value of the LEET form factor remains the same in the range of the unitarity triangle phase α favored by the standard model. The CP-asymmetry for the above mentioned decay has been calculated, and its suppression due to the hard-spectator correction has also been incorporated. In addition, the sensitivity of the CP-asymmetry on the underlying parameters has been discussed.  相似文献   
909.
Investigations of detonation onset in pulverized fuel–air mixtures were carried out. Combustion and detonation processes in sprays differ greatly from that in homogeneous mixtures, because not only chemical reactions, but physical processes of combustible mixture formation take place within the combustion zone (droplets atomization and evaporation). The polydispersed character of mixture and non-uniformity of droplet spatial distribution strongly affects spray combustion and detonation onset. The present paper contains the results of theoretical and experimental investigations of detonation onset peculiarities in polydispersed non-uniform hydrocarbon–air mixtures.  相似文献   
910.
During irradiation of liquid samples of 1-vinylimidazole, 2-vinylnaphthalene, 2-vinylpyridine, 4-vinylpyridine and 1,1-diphenylethene with positive muons, radicals of the type MuCH2ĊHAr (Ar=the appropriate aromatic group), and the MuCH2ĊPh2 radical were observed by transverse field μSR; the muon hyperfine couplings are considered in the context of the effectiveness of the aryl groups in delocalising the unpaired electron.  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