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   1377435篇
  免费   25781篇
  国内免费   7741篇
化学   691360篇
晶体学   20466篇
力学   75281篇
综合类   102篇
数学   243578篇
物理学   380170篇
  2021年   13551篇
  2020年   15963篇
  2019年   16088篇
  2018年   13366篇
  2016年   28240篇
  2015年   20886篇
  2014年   30494篇
  2013年   74530篇
  2012年   39787篇
  2011年   37995篇
  2010年   38010篇
  2009年   40075篇
  2008年   36880篇
  2007年   32810篇
  2006年   38371篇
  2005年   31048篇
  2004年   31835篇
  2003年   29821篇
  2002年   30635篇
  2001年   30418篇
  2000年   26049篇
  1999年   23155篇
  1998年   21255篇
  1997年   21275篇
  1996年   21248篇
  1995年   19331篇
  1994年   18760篇
  1993年   18334篇
  1992年   18466篇
  1991年   18785篇
  1990年   17937篇
  1989年   17981篇
  1988年   17498篇
  1987年   17428篇
  1986年   16385篇
  1985年   22796篇
  1984年   23950篇
  1983年   20090篇
  1982年   21754篇
  1981年   20956篇
  1980年   20313篇
  1979年   20595篇
  1978年   21804篇
  1977年   21443篇
  1976年   21267篇
  1975年   19925篇
  1974年   19638篇
  1973年   20125篇
  1972年   14580篇
  1967年   12719篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
A refined definition of basic concepts for logic describing physical systems is proposed. Within the suggested formalism of generating semigroups the active logic of questions and passive logic of answers are introduced. The objects for which both logics are isomorphic are called self-adequate. It is shown that the assumption of self-adequacy implies that the object is either quantum or classical. The possibility of application of the theory to non-self-adequate objects is discussed.  相似文献   
992.
Based on a dipole-dipole interaction model, we discuss the levitation force and related vibration problems to understand the effects of flux pinning in type-II superconductors, and the applications of levitation in superconducting systems.  相似文献   
993.
In an effort to clarify the role of controlled oxygen exposure in the synthesis of LaBa2Cu3Oy samples which achieve zero resistivity above 90 K, we have prepared samples of La(1+x)Ba(2–x)Cu3Oy with x approximately equal to 0 and with y varying between 6.22 and 7.00. We find that for large values of y, 6.88相似文献   
994.
The influence of an electrical field on the charge transfer in crystals with orbital degeneration is investigated. An expression is obtained for the current density in crystals with narrow d-conduction bands in transition metal compounds. As the electrical field intensity increases, a current density maximum is observed with a subsequent section of negative differential conductivity. The results of the investigation agree qualitatively with experimental data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 14–18, February, 1989.  相似文献   
995.
Summary We have estimated and measured the daily thermal expansion of an oceanographic platform. This has been found negligible as far as the calibration of a satellite altimeter is concerned.  相似文献   
996.
Conclusions Complex compounds of bisacyl derivatives of diaminodibenzo-18-crown-6 ether are active catalysts of the two stages of the synthesis of poly(ethylene terephthalate).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2544–2547, November. 1987.  相似文献   
997.
This Note introduces a new integral form of the charge and current deposition scheme given in 1992 by Villasenor and Buneman, which permits the conservation of charge in PIC codes. This integral form extends directly to higher order spline shape factors, whose use produces less numerical noise. We thus get a discrete charge conserving method for high order shape factors. This method extends easily to nonuniform Cartesian grids for first order shape factors. To cite this article: R. Barthelmé, C. R. Acad. Sci. Paris, Ser. I 341 (2005).  相似文献   
998.
999.
In this paper, by extending Kucera's idea to the function field case, we obtain several determinant formulas involving the real class number and the relative class number of any subfield of cyclotomic function fields. We also provide several examples using these determinant formulas.

  相似文献   

1000.
A brief review of the potential functions used in the molecular dynamics modeling of liquid benzene is presented. The structural characteristics of liquid benzene obtained from the correlation distribution functions are discussed. It is demonstrated that, within the framework of this approach, the predicted structure of liquid benzene is virtually independent of the form of the potential used.  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