全文获取类型
收费全文 | 204563篇 |
免费 | 1344篇 |
国内免费 | 444篇 |
专业分类
化学 | 105799篇 |
晶体学 | 3407篇 |
力学 | 10366篇 |
综合类 | 10篇 |
数学 | 22011篇 |
物理学 | 64758篇 |
出版年
2021年 | 2049篇 |
2020年 | 2062篇 |
2019年 | 2646篇 |
2018年 | 3723篇 |
2017年 | 3721篇 |
2016年 | 4894篇 |
2015年 | 2399篇 |
2014年 | 4383篇 |
2013年 | 8727篇 |
2012年 | 6941篇 |
2011年 | 8140篇 |
2010年 | 6527篇 |
2009年 | 6712篇 |
2008年 | 7699篇 |
2007年 | 7648篇 |
2006年 | 6735篇 |
2005年 | 5948篇 |
2004年 | 5657篇 |
2003年 | 5188篇 |
2002年 | 5179篇 |
2001年 | 5615篇 |
2000年 | 4149篇 |
1999年 | 3139篇 |
1998年 | 2715篇 |
1997年 | 2769篇 |
1996年 | 2547篇 |
1995年 | 2215篇 |
1994年 | 2338篇 |
1993年 | 2231篇 |
1992年 | 2527篇 |
1991年 | 2650篇 |
1990年 | 2561篇 |
1989年 | 2632篇 |
1988年 | 2541篇 |
1987年 | 2561篇 |
1986年 | 2416篇 |
1985年 | 3041篇 |
1984年 | 3110篇 |
1983年 | 2604篇 |
1982年 | 2573篇 |
1981年 | 2529篇 |
1980年 | 2342篇 |
1979年 | 2713篇 |
1978年 | 2676篇 |
1977年 | 2873篇 |
1976年 | 2877篇 |
1975年 | 2668篇 |
1974年 | 2604篇 |
1973年 | 2713篇 |
1972年 | 2085篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
T. K. V. Iyengar N. Srinivasacharyulu J. V. Ramana Murthy 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1988,39(5):649-667
An elliptic cylinder is performing oscillations parallel to either of the principal axes of the cross-sectional ellipse in a fluid particle suspension. The stream function governing the flow and the velocity components are determined in terms of Mathieu functions. The drag on the cylinder is evaluated and expressed in terms of two parametersK andK. The effects of the variation of the frequency parameter, eccentricity parameter and relaxation time parameter on the drag parametersK, K is studied numerically. 相似文献
982.
We present a modification of the Cyclic Subgradient Projection (CSP) method by Censor and Lent, which solves the convex feasibility problem in a finite number of steps when a Slater type condition holds, while preserving its row-action properties. A linear rate of convergence for the CSP method is established assuming the same hypothesis.Research partially supported by CNPq, under Grant No. 301699/81. 相似文献
983.
Wide-angle one-way wave equations 总被引:3,自引:0,他引:3
A one-way wave equation, also known as a paraxial or parabolic wave equation, is a differential equation that permits wave propagation in certain directions only. Such equations are used regularly in underwater acoustics, in geophysics, and as energy-absorbing numerical boundary conditions. The design of a one-way wave equation is connected with the approximation of (1-s2)1/2 on [-1,1] by a rational function, which has usually been carried out by Padé approximation. This article presents coefficients for L2, L infinity, and other alternative classes of approximants that have better wide-angle behavior. For theoretical results establishing the well posedness of these wide-angle equations, see the work of Trefethen and Halpern ["Well-posedness of one-way wave equations and absorbing boundary conditions," Math. Comput. 47, 421-435 (1986)]. 相似文献
984.
As is well known, Lovász Local Lemma implies that everyd-uniformd-regular hypergraph is 2-colorable, providedd 9. We present a different proof of a slightly stronger result; everyd-uniformd-regular hypergraph is 2-colorable, providedd 8.Research supported in part by Allon Fellowship and by a grant from the United States Israel Binational Science Foundation. 相似文献
985.
986.
LetW
(x) be a function nonnegative inR, positive on a set of positive measure, and such that all power moments ofW
2(x) are finite. Let {p
n
(W
2;x)}
0
denote the sequence of orthonormal polynomials with respect to the weightW
2(x), and let {A
n
}
1
and {B
n
}
1
denote the coefficients in the recurrence relation
相似文献
987.
Traditional O.R. systems are compared with problem solving in Artificial Intelligence via Expert Systems. The discussion centers on explicit knowledge representation. The general aspects are illustrated by two planning systems:
988.
M. N. Islam 《Annali di Matematica Pura ed Applicata》1988,150(1):129-139
The existence of a continuous periodic solution of the system
|
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 |