全文获取类型
收费全文 | 371413篇 |
免费 | 3778篇 |
国内免费 | 1441篇 |
专业分类
化学 | 193071篇 |
晶体学 | 5983篇 |
力学 | 17281篇 |
综合类 | 8篇 |
数学 | 41606篇 |
物理学 | 118683篇 |
出版年
2020年 | 2749篇 |
2019年 | 2991篇 |
2018年 | 3688篇 |
2017年 | 3631篇 |
2016年 | 5880篇 |
2015年 | 3985篇 |
2014年 | 6056篇 |
2013年 | 16440篇 |
2012年 | 12660篇 |
2011年 | 15876篇 |
2010年 | 10672篇 |
2009年 | 10755篇 |
2008年 | 14583篇 |
2007年 | 14528篇 |
2006年 | 13905篇 |
2005年 | 12665篇 |
2004年 | 11642篇 |
2003年 | 10135篇 |
2002年 | 10045篇 |
2001年 | 11663篇 |
2000年 | 8910篇 |
1999年 | 6935篇 |
1998年 | 5629篇 |
1997年 | 5559篇 |
1996年 | 5347篇 |
1995年 | 4867篇 |
1994年 | 4688篇 |
1993年 | 4678篇 |
1992年 | 5021篇 |
1991年 | 5146篇 |
1990年 | 4681篇 |
1989年 | 4646篇 |
1988年 | 4686篇 |
1987年 | 4518篇 |
1986年 | 4284篇 |
1985年 | 6022篇 |
1984年 | 6168篇 |
1983年 | 5025篇 |
1982年 | 5363篇 |
1981年 | 5162篇 |
1980年 | 5003篇 |
1979年 | 5112篇 |
1978年 | 5218篇 |
1977年 | 5138篇 |
1976年 | 5200篇 |
1975年 | 4874篇 |
1974年 | 4840篇 |
1973年 | 4953篇 |
1972年 | 3283篇 |
1971年 | 2568篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
We discuss a mass change that has its origin in the action of forces on an object. This phenomenon, well-known in the context of quantum field theory (mass renormalization), can be discussed systematically in both classical and quantum mechanics in a framework given by Stückelberg. We employ this framework to resolve an interesting conflict of opinions between Schopenhauer and Hegel in the mid-19th century. We show that Hegel, Kant, and Schopenhauer demonstrated remarkable prescience in their views as seen from a modern perspective. 相似文献
112.
The results of experimental investigations on thermal nonequilibrium ionization in CO2: N2: He mixtures are presented. Measurements of electron density, ne, in vibrationally excited nitrogen were made in a supersonic flow with different CO2 contents as well as in a CO2: N2: He = 1 : 5 : 4 mixture laser gas. The mixtures were heated in a shock tube and expanded through a supersonic nozzle. Furthermore, supersonic mixing of N2 and CO2 + He was used in some experiments. The measured values of ne in the plenum chamber and in the supersonic nozzle are reported, and the processes responsible for nonequilibrium ionization in a laser-active medium are discussed. 相似文献
113.
114.
115.
P. R. Latthe P. S. Shinge Bharati V. Badami P. B. Patil S. N. Holihosur 《Journal of Chemical Sciences》2006,118(3):249-256
3-[4-(Azidocarbonyl)]phenylsydnone (2) obtained from 3-(4-hydrazinocarbonyl) phenylsydnone (1) on Curtius rearrangement with alcohols, water and amines afforded the corresponding carbamates (3a-h), 4,4′-(sydnone-3-yl) diphenyl urea (4) and 4-(heterocyclyl)phenyl ureas (5a-l). Compounds (5a-l) on one-pot ring conversion yielded the 1,3,4-oxadiazolin-2-one derivatives (6a-l), which on reaction with N2H4 gave the 4-amino-1,2,4-triazolin-3-ones (7a-l). All these compounds exhibited moderate antimicrobial activity against the few microbes tested. The carbamates have been
found to be more toxic against fourth instar larvae ofAedes aegypti, in particular, then-butyl derivative (3e). 相似文献
116.
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
117.
We extend the matrix version of Cochran's statistical theorem to outer inverses of a matrix. As applications, we investigate the Wishartness and independence of matrix quadratic forms for Kronecker product covariance structures. 相似文献
118.
119.
X Y Liu C J Li 《Science in China. Series B, Chemistry, life sciences & earth sciences》1989,32(10):1215-1223
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
120.
The auction algorithm for the transportation problem 总被引:1,自引:0,他引:1
The auction algorithm is a parallel relaxation method for solving the classical assignment problem. It resembles a competitive bidding process whereby unassigned persons bid simultaneously for objects, thereby raising their prices. Once all bids are in, objects are awarded to the highest bidder. This paper generalizes the auction algorithm to solve linear transportation problems. The idea is to convert the transportation problem into an assignment problem, and then to modify the auction algorithm to exploit the special structure of this problem. Computational results show that this modified version of the auction algorithm is very efficient for certain types of transportation problems. 相似文献