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   438761篇
  免费   3404篇
  国内免费   1588篇
化学   213131篇
晶体学   6198篇
力学   23191篇
综合类   66篇
数学   64675篇
物理学   136492篇
  2020年   3310篇
  2019年   3790篇
  2018年   11819篇
  2017年   12463篇
  2016年   10229篇
  2015年   4523篇
  2014年   6578篇
  2013年   14837篇
  2012年   15433篇
  2011年   24171篇
  2010年   16331篇
  2009年   16475篇
  2008年   21963篇
  2007年   24701篇
  2006年   12977篇
  2005年   16209篇
  2004年   13072篇
  2003年   12177篇
  2002年   10660篇
  2001年   10782篇
  2000年   8281篇
  1999年   6009篇
  1998年   5205篇
  1997年   5039篇
  1996年   5019篇
  1995年   4382篇
  1994年   4433篇
  1993年   4313篇
  1992年   4575篇
  1991年   4916篇
  1990年   4631篇
  1989年   4606篇
  1988年   4469篇
  1987年   4415篇
  1986年   4259篇
  1985年   5528篇
  1984年   5601篇
  1983年   4736篇
  1982年   5001篇
  1981年   4704篇
  1980年   4337篇
  1979年   4772篇
  1978年   5109篇
  1977年   5120篇
  1976年   5310篇
  1975年   4902篇
  1974年   4923篇
  1973年   5099篇
  1972年   4011篇
  1971年   3402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.
On the basis of the method of successive approximations in formal series we construct systems of particular solutions of the equations of planar and flexural harmonic vibrations of thin rectilinear anisotropic plates with a plane of symmetry of elastic properties parallel to the faces. The solutions constructed are classified as special sk-functions of generalized complex variables. Translated fromTeoreticheskaya i Prikladnaya Mekhanika No. 24, 1993, pp. 54–61.  相似文献   
34.
Nonperturbative nolocal structure of QCD vacuum is well described by instanton model. Specific helicity and flavor structure of zero modes of quarks, in instanton field allows simultaneously to explain some important features of low-and high-energy hadron phenomemology. The basic characteristics of hadron spectrum, partonic sum rules, heavyquark potential etc within the instanton liquid model are briefly discussed.  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.
The simple relation between representations of the covering groups of SL2 and GL2 makes it possible to fuse and extend the recent metaplectic results of Shimura, Waldspurger, Flicker, and ourselves. By giving a new (purely local andL-function theoretic) treatment of the Waldspurger-Shintani correspondence, we also simplify some of Waldspurger’s original results.  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.
This paper presents an alternative to the beta continuous probability distribution for risk analysis. Particular attention has been given to two major applications of distributions, namely project management risk and critical path analysis (PERT). In conjunction with the beta, the triangular and normal distributions are frequently employed in order to give sufficient robustness to risk analysis. The beta distribution, as used in PERT, has a major theoretical implementation flaw. The new distribution was developed to give a possible alternative method of assessing risk. It is shown that the requirement to estimate the most pessimistic variate may be replaced by the probability to exceed the mode. Proposals for other simplifications in risk analysis are discussed. Practical means to validate the most appropriate distributions for risk analysis are outlined, and a cost-data case study is included.  相似文献   
39.
40.
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