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   362591篇
  免费   4071篇
  国内免费   1785篇
化学   195264篇
晶体学   5775篇
力学   15155篇
综合类   64篇
数学   42202篇
物理学   109987篇
  2020年   2923篇
  2019年   3214篇
  2018年   4151篇
  2017年   4251篇
  2016年   6330篇
  2015年   4049篇
  2014年   6219篇
  2013年   15498篇
  2012年   12383篇
  2011年   14966篇
  2010年   10718篇
  2009年   10572篇
  2008年   14167篇
  2007年   14145篇
  2006年   13374篇
  2005年   12116篇
  2004年   10980篇
  2003年   9761篇
  2002年   9605篇
  2001年   10838篇
  2000年   8194篇
  1999年   6121篇
  1998年   5143篇
  1997年   5031篇
  1996年   4861篇
  1995年   4390篇
  1994年   4440篇
  1993年   4257篇
  1992年   4740篇
  1991年   4759篇
  1990年   4544篇
  1989年   4417篇
  1988年   4337篇
  1987年   4269篇
  1986年   4164篇
  1985年   5477篇
  1984年   5600篇
  1983年   4804篇
  1982年   5119篇
  1981年   4766篇
  1980年   4536篇
  1979年   4834篇
  1978年   5053篇
  1977年   5022篇
  1976年   5079篇
  1975年   4742篇
  1974年   4826篇
  1973年   5024篇
  1972年   3683篇
  1971年   2960篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
It has been shown by the ESR of spin probes that thionin initially interacts with with negatively charged membranes electrostatically and then passes into the membranes to a depth comparable with the length of the hydrophobic sections of the protein loops.Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent. Brigham Young University, Provo, Utah, USA. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 594–597, July–August, 1993.  相似文献   
32.
Blumberg  L. M. 《Chromatographia》1994,39(11-12):719-728
Chromatographia - Previously [11], the theoretical limit ofresolution in one class of chromatographic conditions was found and its proof was briefly outlined. Here, the theoretical limits...  相似文献   
33.
34.
An estimate of the factors which influence the rate of growth of filamentary silicon crystals in a standard chloride system using a quartz reactor with hot walls is given. It is shown that a diffusion form of crystallization is observed under the conditions investigated.Voronezh State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 22–26, October, 1995.  相似文献   
35.
Surface relief formation at holographic recording on amorphous selenium films was demonstrated and investigated. The presence of this optical phase modulation component is essential for ensuring significant, stable and erasable optical recording in a-Se films at 290–320 K temperatures, where conventional photodarkening was known as insignificant and unstable. Photocrystallization can only be observed in super-exposed a-Se films at the given experimental conditions of hologram recording. Erasing behavior of surface relief gratings under heat treatment was also investigated in order to reveal further details of the mechanism. Photoinduced structural transformations within the amorphous phase, connected to local ordering under the condition of light-induced fluidity, are proposed as an explanation for the relief formation and erasing. The observed reversible optical recording process may be useful for the various optoelectronic applications of photoconductive a-Se layers. Received: 12 June 2000 / Accepted: 6 June 2001 / Published online: 30 August 2001  相似文献   
36.
Using an integral theory of grating diffraction we calculate efficiencies greater than 100% if a coating with gain is taken into account. A connection with guided modes is conjectured. The application in optical computing seems to be possible.  相似文献   
37.
In this paper, an application of the Riquer-Thomas-Janet theory is described for the problem of transforming a system of partial differential equations into a passive form, i.e., to a special form which contains explicitly both the equations of the initial system and all their nontrivial differential consequences. This special representation of a system markedly facilitates the subsequent integration of the corresponding differential equations. In this paper, the modern approach to the indicated problem is presented. This is the approach adopted in the Knuth-Bendix procedure [13] for critical-pair/completion and then Buchberger's algorithm for completion of polynomial ideal bases [13] (or, alternatively, for the construction of Groebner bases for ideals in a differential operator ring [14]). The algorithm of reduction to the passive form for linear system of partial differential equations and its implementation in the algorithmic language REFAL, as well as the capabilities of the corresponding program, are outlined. Examples illustrating the power and efficiency of the system are presented.  相似文献   
38.
39.
40.
The article surveys the main results of the statistical approach to the solution of ill-posed problems of mathematical physics, in application to specific ill-posed inverse problems in geophysics.Invited paper presented at the International Seminar on Mathematical Foundations of the Interpretation of Geophysical Fields, Moscow, May–June 1972.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 79, pp. 67–81, 1978.  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