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   358038篇
  免费   3364篇
  国内免费   1085篇
化学   191590篇
晶体学   5718篇
力学   14699篇
综合类   9篇
数学   41343篇
物理学   109128篇
  2020年   3118篇
  2019年   3532篇
  2018年   4794篇
  2017年   4782篇
  2016年   6828篇
  2015年   3967篇
  2014年   6434篇
  2013年   15851篇
  2012年   11764篇
  2011年   14165篇
  2010年   10276篇
  2009年   10067篇
  2008年   13523篇
  2007年   13497篇
  2006年   12617篇
  2005年   11391篇
  2004年   10325篇
  2003年   9391篇
  2002年   9107篇
  2001年   10137篇
  2000年   7827篇
  1999年   5959篇
  1998年   5078篇
  1997年   5028篇
  1996年   4711篇
  1995年   4151篇
  1994年   4205篇
  1993年   4123篇
  1992年   4499篇
  1991年   4530篇
  1990年   4410篇
  1989年   4332篇
  1988年   4249篇
  1987年   4249篇
  1986年   4020篇
  1985年   5266篇
  1984年   5483篇
  1983年   4616篇
  1982年   4961篇
  1981年   4692篇
  1980年   4486篇
  1979年   4804篇
  1978年   4975篇
  1977年   4896篇
  1976年   4957篇
  1975年   4723篇
  1974年   4653篇
  1973年   4977篇
  1972年   3291篇
  1971年   2812篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
The applicability of differential electrolytic potentiometry as a detection system in flow injection analysis is investigated. A computer-controlled injector which delivers precise volumes of sample solutions in a reproducible manner was developed. Conditions such as current density employed, the concentrations of the solutions used and the flow rate were optimized. Chloride in water was determined by means of this system. The relation between chloride concentration and the measured signal was found to be Nernstian for solutions of concentrations above 6 μg ml−1 chloride. For solutions below this concentration, the relation is linear.  相似文献   
162.
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   
163.
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   
164.
The microhardness and content of carbon in electroplated gold coatings were studied as influenced by the operation time of citrate and citrate-phosphate gold-plating electrolytes. Such physicomechanical properties as porosity, microhardness, internal stress, plasticity, and microstructure of electroless-plated and electroplated nickel coatings were studied and analyzed.  相似文献   
165.
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   
166.
167.
168.
169.
A convenient method is proposed for the synthesis of all the individual methyl ethers of methyl 2-acetamido-2-deoxy-α-D-glucopyranoside based on the partial methylation of 2-acetamido-2-deoxy-α-D-glucopyranoside with dimethyl sulfate in an alkaline medium followed by preparative liquid column chromatography on silica gel of the resulting mixture of methyl ethers.  相似文献   
170.
Transport as a consequence of state-dependent diffusion   总被引:1,自引:0,他引:1  
Overdamped particles subject to a drift in a force field with sinusoidal space dependence and also a sinusoidally modulated space-dependent diffusion, with the same period as the drift, experience a net driving force. The resulting current depends on the amplitude of the modulation of the diffusion and is a periodic function of the phase difference between the sinusoidal drift and the sinusoidal modulation of the diffusion. For small modulation amplitudes a particle subject to state-dependent noise behaves the same way as a particle subject to thermal noise but with a drift which, in addition to the sinusoidal term, contains a net force term.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday  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