全文获取类型
收费全文 | 25032篇 |
免费 | 532篇 |
国内免费 | 99篇 |
专业分类
化学 | 13968篇 |
晶体学 | 153篇 |
力学 | 767篇 |
综合类 | 9篇 |
数学 | 3446篇 |
物理学 | 7320篇 |
出版年
2022年 | 310篇 |
2021年 | 394篇 |
2020年 | 364篇 |
2019年 | 311篇 |
2018年 | 405篇 |
2017年 | 361篇 |
2016年 | 624篇 |
2015年 | 525篇 |
2014年 | 602篇 |
2013年 | 969篇 |
2012年 | 1262篇 |
2011年 | 1429篇 |
2010年 | 804篇 |
2009年 | 755篇 |
2008年 | 1209篇 |
2007年 | 1190篇 |
2006年 | 1070篇 |
2005年 | 1505篇 |
2004年 | 1530篇 |
2003年 | 1069篇 |
2002年 | 716篇 |
2001年 | 603篇 |
2000年 | 556篇 |
1999年 | 346篇 |
1998年 | 290篇 |
1997年 | 289篇 |
1996年 | 359篇 |
1995年 | 320篇 |
1994年 | 313篇 |
1993年 | 338篇 |
1992年 | 328篇 |
1991年 | 265篇 |
1990年 | 217篇 |
1989年 | 205篇 |
1988年 | 182篇 |
1987年 | 176篇 |
1986年 | 175篇 |
1985年 | 225篇 |
1984年 | 217篇 |
1983年 | 184篇 |
1982年 | 190篇 |
1981年 | 185篇 |
1980年 | 169篇 |
1979年 | 154篇 |
1978年 | 182篇 |
1977年 | 139篇 |
1976年 | 134篇 |
1975年 | 117篇 |
1974年 | 137篇 |
1973年 | 123篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
J. Pires M. Brotas de Carvalho F. R. Ribeiro E. G. Derouane 《Reaction Kinetics and Catalysis Letters》1991,43(2):313-319
The silicoaluminophosphate SAPO-37 as well as ZSM-20 zeolite have a faujaside-like structure and are potentially useful as catalysts. We report in this work different procedures to decompose the organic template occluded in SAPO-37. The texture of the final products was analyzed by means of nitrogen adsorption. The acid properties of SAPO-37 and ZSM-20 were also compared by IR measurements of adsorbed pyridine and related to the acidic properties of the presently commonly used cracking catalyst zeolite Y.
-37, ZSM-20 . , -37. . -37 ZSM-20 - . , .相似文献
942.
R. de Leone 《Journal of Optimization Theory and Applications》1991,69(2):235-249
A unified treatment is given for partially and totally asynchronous parallel successive overrelaxation (SOR) algorithms for the linear complementarity problem. Convergence conditions are established and compared to previous results. Convergence of the partially asynchronous method for the symmetric linear complementarity problem can be guaranteed if the relaxation factor is sufficiently small. Unlike previous results, this relaxation factor interval does not depend explicitly on problem size.This material is based on research supported by the Air Force Office of Scientific Research Grant No. AFOSR-89-0410.The author wishes to thank the referee for pointing out how to improve the bound (12). The same technique can be used to reduce the factorn in Ref. 5, p. 553, to
. 相似文献
943.
Fernando de Felice 《General Relativity and Gravitation》1991,23(2):135-149
In this paper we deduce the general pattern of the potential surfaces for time-like geodesics in the Curzon metric. We find that for fairly small energies and orbital angular momenta, the time-like geodesics group into two sets; the geodesics of one set tend to thez-axis asR=(r2+z2)1/2 0,R=0 being a directional singularity, the others tend to ther-axis. At low energies these two sets are detached but they merge together as the energy increases. Stable circular motion is confined to thez = 0-plane and an energy threshold for stationary motion exists and is equal (per unit of rest-mass energy) to 0.945, a value almost indistinguishable from that in the Schwarzschild space-time. 相似文献
944.
We are dealing with a numerical method for solving the problem of minimizing a difference of two convex functions (a d.c. function) over a closed convex set in
n
. This algorithm combines a new prismatic branch and bound technique with polyhedral outer approximation in such a way that only linear programming problems have to be solved.Parts of this research were accomplished while the third author was visiting the University of Trier, Germany, as a fellow of the Alexander von Humboldt foundation. 相似文献
945.
946.
947.
948.
949.
950.