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   399246篇
  免费   4743篇
  国内免费   1454篇
化学   218399篇
晶体学   5823篇
力学   16556篇
综合类   12篇
数学   46204篇
物理学   118449篇
  2020年   2462篇
  2019年   2405篇
  2018年   2421篇
  2016年   4758篇
  2015年   3954篇
  2014年   5376篇
  2013年   17282篇
  2012年   12929篇
  2011年   16219篇
  2010年   10060篇
  2009年   9908篇
  2008年   14893篇
  2007年   15152篇
  2006年   14834篇
  2005年   13733篇
  2004年   12309篇
  2003年   10928篇
  2002年   10688篇
  2001年   12166篇
  2000年   9376篇
  1999年   7504篇
  1998年   6153篇
  1997年   5975篇
  1996年   5985篇
  1995年   5549篇
  1994年   5165篇
  1993年   4980篇
  1992年   5592篇
  1991年   5438篇
  1990年   5088篇
  1989年   4932篇
  1988年   5191篇
  1987年   4917篇
  1986年   4726篇
  1985年   6800篇
  1984年   6926篇
  1983年   5671篇
  1982年   6305篇
  1981年   6205篇
  1980年   5980篇
  1979年   6053篇
  1978年   6201篇
  1977年   6116篇
  1976年   6084篇
  1975年   5913篇
  1974年   5647篇
  1973年   5919篇
  1972年   3496篇
  1971年   2627篇
  1968年   2577篇
排序方式: 共有10000条查询结果,搜索用时 105 毫秒
71.
Equilibrium Problems with Applications to Eigenvalue Problems   总被引:5,自引:0,他引:5  
In this paper, we consider equilibrium problems and introduce the concept of (S)+ condition for bifunctions. Existence results for equilibrium problems with the (S)+ condition are derived. As special cases, we obtain several existence results for the generalized nonlinear variational inequality studied by Ding and Tarafdar (Ref. 1) and the generalized variational inequality studied by Cubiotti and Yao (Ref. 2). Finally, applications to a class of eigenvalue problems are given.  相似文献   
72.
In a recent paper to this journal (Whitman A M et al 2003 Waves Random Media 13 269-86) we derived a set of coupled equations that describe the intermodal scattering of acoustic radiation in a duct whose speed of sound varies randomly in space and time. In the paper we were mainly interested in modes that were not near cutoff. Here we study the solution of these equations in the vicinity of the cutoff. We find that near cutoff almost all the energy is reflected back independent of the other duct parameters. In addition to presenting these results, we analyse the mathematical structure of the equations in these regions in order to elucidate the reason for this behaviour.  相似文献   
73.
Summary This paper presents some applications of cyclic voltammetry at the interface of two immiscible electrolyte solutions by means of an experimental set-up described in a former publication. When using special sample preparation good results are obtained for the determination of iodide and quinine in pharmaceutical products as well as for the determination of quinine in tonic water and dodecylsulfate in a tooth-salt.

Herrn Prof. Dr. Günther Tölg zum 60. Geburtstag gewidmet  相似文献   
74.
To further evaluate the causality between endogenous pyrogen (EP)-induced fever and cyclic adenosine-3',5'-monophosphate (cyclic AMP) level, the effects of sodium salicylate (SS) on the febrile response and increased levels of cyclic AMP in both cerebrospinal fluid (c.s.f.) and plasma during EP-induced fever in rabbits were observed. The results suggest that cyclic AMP is probably involved in the central mediation of EP-induced fever and that increased concentration of cyclic AMP in c.s.f. associated with EP-induced fever is not the result of temperature elevation but appears to be caused by the increased synthesis in the central nervous system. In addition it is confirmed that blood is impossibly a contributory source of increased cyclic AMP in c.s.f. during EP fever, and that SS may act subsequent to the increase in cyclic AMP.  相似文献   
75.
The variational approach based on the covariant quantization method for the curved Einstein space is applied.  相似文献   
76.
The precision of intensity modulated fiber optic sensor systems mainly is restricted by the attenuation characteristics of the analog fiber optical data link. Special encoding and referencing schemes are used to overcome this data link dependence. In this paper encoding and referencing principles for optical sensors are outlined and compared. Especially the two wavelengths referencing and the optical delay line processing techniques are discussed in more detail and results are presented.  相似文献   
77.
78.
79.
80.
A three-dimensional examination of blood vessels is provided using MR data from seven cases. The vascular surfaces are constructed with an algorithm that automatically follows the selected artery or vein and generates a projected three-dimensional gradient shaded image. Fast 3DFT pulse sequences were optimized to enhance the time-of-flight contrast of the intravascular region. By increasing the surface threshold value in a three-dimensional head study, the flesh of a patient's face was peeled away to demonstrate the superfacial temporal artery. Gated cardiac images show the great vessels and cardiac chambers. A three-dimensional view of the aorta shows an irregular surface in the vicinity of an adrenal tumor. 3D MR exams provide a non-invasive technique for assessing vascular morphology in a clinical setting.  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