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   355839篇
  免费   6986篇
  国内免费   5045篇
化学   171601篇
晶体学   5290篇
力学   20984篇
综合类   332篇
数学   54323篇
物理学   115340篇
  2021年   3640篇
  2020年   3990篇
  2019年   4643篇
  2018年   12618篇
  2017年   12975篇
  2016年   10754篇
  2015年   4952篇
  2014年   7204篇
  2013年   12689篇
  2012年   14585篇
  2011年   22492篇
  2010年   15485篇
  2009年   15807篇
  2008年   19834篇
  2007年   22461篇
  2006年   9943篇
  2005年   13474篇
  2004年   10504篇
  2003年   10072篇
  2002年   8621篇
  2001年   7736篇
  2000年   6034篇
  1999年   4459篇
  1998年   3976篇
  1997年   3793篇
  1996年   3726篇
  1995年   3190篇
  1994年   3348篇
  1993年   3188篇
  1992年   3415篇
  1991年   3554篇
  1990年   3490篇
  1989年   3458篇
  1988年   3279篇
  1987年   3270篇
  1986年   3114篇
  1985年   3755篇
  1984年   3840篇
  1983年   3253篇
  1982年   3192篇
  1981年   3071篇
  1980年   2871篇
  1979年   3353篇
  1978年   3346篇
  1977年   3424篇
  1976年   3547篇
  1975年   3245篇
  1974年   3207篇
  1973年   3386篇
  1972年   2639篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
981.
We show that the modified method for finite-dimensional approximation of solutions of Fredholm integral equations of the first kind presented in this paper is more economical than traditional methods for finite-dimensional approximation. Institute of Mathematies, Ukrainian Academy of Science, Kiev. Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 49, No. 2, pp. 289–295, February, 1997.  相似文献   
982.
An overview of membrane introduction mass spectrometry (MIMS) is presented and comparisons are made with other direct sample introduction techniques. Special attention is given to the unique advantages and the limitations of newer variants on the MIMS technique, including affinity MIMS, reverse-phase and trap MIMS. The salient features of the interfaces used in MIMS are summarized and the various membrane materials commonly used are delineated. The applicability of MIMS is illustrated via discussion of
1. (i) bioreactor monitoring (represented by yeast fermentation),
2. (ii) environmental monitoring (illustrated by analysis of contaminated ground water samples) and
3. (iii) on-line chemical reaction monitoring (exemplified by the photolysis of aryl esters).
The applicability of MIMS to the analysis of environmental samples, including complex mixtures in water, air and soil, is noted.  相似文献   
983.
984.
The electrochemical behavior of the copper-tyrosine complex has been studied by linear-sweep adsorption voltammetry. In 0.02 mol/L Na2HPO4 buffer solution (pH=9.6), the complex can be adsorped on a hanging mercury drop electrode and reduced at a peak potential of about –0.42 V (vs. SCE). The secondary derivative peak height is linear proportional to the concentration of tyrosine in the range 1.0×10–7–5.0×10–5 mol/L. The detection limit is 5×10–8 mol/L.Project supported by the Provincial Science Foundation of Shandong Province  相似文献   
985.
Plasma Chemistry and Plasma Processing - Nonequilibrium nitrogen dissociation-recombination kinetics in the boundary layer and on the surface of a solid body during hypersonic flow. the subsequent...  相似文献   
986.
We study the conjugate boundary-value problem with boundary conditions whose orders can be as large as the order of the differential equation or larger. We construct the Green's function of the problem over the entire space when the separating surface is a hyperplane, and we describe its properties. Bibliography: 6 titles.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 30, 1989, pp. 20–24.  相似文献   
987.
988.
Chemiluminescence (CL) was found upon the isomerization of dimethyldioxirane in the gas phase under argon atmosphere. The intensity of CL increases as temperature increases and decreases with time at constant temperature. If Silipor is placed in a cell containing the dimethyldioxirane vapor in argon, the intensity of CL sharply increases (more than 10 times) and then decreases following the exponential law. In all cases tripletly excited methyl acetate is the emitter of chemiluminescence.[/ p]Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2582–2583, October 1996.  相似文献   
989.
On the basis of the general class of solutions of 6D vacuum Einstein equations and using well-known results of the 6D geometric model of electroweak and gravitational interactions, the variations of fundamental physical constants and their influence on the observed red-shift of galaxies are investigated. By considering the interpretation of extra components of the 6D metric as reproducing the properties of matter in the 4D curved space-time, the effective quantities of matter are obtained. In particular, the states of dust and radiation are shown. The corresponding 5D models were also investigated.  相似文献   
990.
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