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   306238篇
  免费   16928篇
  国内免费   685篇
化学   192600篇
晶体学   4184篇
力学   12898篇
综合类   9篇
数学   30683篇
物理学   83477篇
  2023年   4449篇
  2021年   4020篇
  2020年   6551篇
  2019年   4411篇
  2018年   5413篇
  2017年   3695篇
  2016年   9680篇
  2015年   7857篇
  2014年   8931篇
  2013年   15491篇
  2012年   11067篇
  2011年   10938篇
  2010年   10243篇
  2009年   9955篇
  2008年   10310篇
  2007年   10225篇
  2006年   9029篇
  2005年   8200篇
  2004年   7531篇
  2003年   6812篇
  2002年   6718篇
  2001年   7358篇
  2000年   5675篇
  1999年   4376篇
  1998年   3877篇
  1997年   3891篇
  1996年   3633篇
  1995年   3439篇
  1994年   3563篇
  1993年   3370篇
  1992年   3730篇
  1991年   3727篇
  1990年   3633篇
  1989年   3504篇
  1988年   3632篇
  1987年   3514篇
  1986年   3322篇
  1985年   4411篇
  1984年   4694篇
  1983年   3928篇
  1982年   4077篇
  1981年   4018篇
  1980年   4005篇
  1979年   3974篇
  1978年   4287篇
  1977年   4259篇
  1976年   4343篇
  1975年   4020篇
  1974年   4075篇
  1973年   4168篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
91.
Electric fields of the anions, cations and neutral forms of 2-aminopurine and 6-thioguanine have been mapped. Certain important features of the maps are similar to those found earlier in the neutral and ionic forms of adenine and guanine. The computed electric field patterns satisfactorily explain reactive sites and biological activity of the molecules.  相似文献   
92.
Investigations to the causes and effects of contaminants at the rf diode deposition of CrSi films in a non-heated high vacuum apparatus were carried out comparing an oxygen-free fusion target with an oxygen-containing cermet target. The films of the fusion target contained considerable amounts of oxygen; analogously the oxygen concentration in the films was increased in the case of the cermet target. Moreover, hydrogen was found. The concentration of the contaminants decreased with the sputtering power, however the rate of incorporation increased. For high sputtering rates the contamination process was reproducible and independent of the plant conditioning; the deposited films were depth-homogeneous. The reasons for this behaviour lie in water sources which are activated first of all by the discharge itself. The electrical properties found are explained by the contaminants and the deposition conditions.  相似文献   
93.
94.
In 1980 Chern and Terng defined a Bäcklund transformation for affine minimal surfaces. In this paper we show that this Bäcklund transformation can be simply represented by an involution and translation of the affine conormal.  相似文献   
95.
96.
Moscow Institute of Electronic Engineering. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 89, No. 1, pp. 132–150, October, 1991.  相似文献   
97.
A new microscopic model of anomalous muonium for the elemental semiconductors is proposed. The relevant configuration consisting of both a diamagrentic molecule Si−Mu and an unpaired orbital e is contained into a semivacancy of the real lattice. By using the unrestricted Hartree-Fock computational method the principal properties of the system are established. A dynamical version of the model together with a question on the formation of such system are discussed.  相似文献   
98.
A random-medium model which is a correlated distribution of points (particles) randomly positioned in the 3-dimensional space is considered. The construction of the medium starts from a noncorrelated (Poisson) distribution of parent particles, each of them initiates a finite Markov chain of its descendants. The complete collection of correlation functions of all orders within the scope of the model have been obtained. The use of the 3-dimensional stable law (Lévy law) as a transition probability allows us to present the correlation function in an explicit form. Proceedings of the XVII Seminar on Stability Problems for Stochastic Models, Kazan, Russian, 1995, Part II.  相似文献   
99.
100.
Kalman's theory is extended to a complete, smooth, and irreducible algebraic curve of arbitrary genus.  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