全文获取类型
收费全文 | 456275篇 |
免费 | 6305篇 |
国内免费 | 1362篇 |
专业分类
化学 | 248359篇 |
晶体学 | 6657篇 |
力学 | 19208篇 |
综合类 | 13篇 |
数学 | 52971篇 |
物理学 | 136734篇 |
出版年
2021年 | 4038篇 |
2020年 | 4561篇 |
2019年 | 4897篇 |
2018年 | 6112篇 |
2017年 | 5979篇 |
2016年 | 9430篇 |
2015年 | 6081篇 |
2014年 | 9173篇 |
2013年 | 21221篇 |
2012年 | 16968篇 |
2011年 | 20720篇 |
2010年 | 14347篇 |
2009年 | 14090篇 |
2008年 | 18848篇 |
2007年 | 18671篇 |
2006年 | 17379篇 |
2005年 | 15615篇 |
2004年 | 14452篇 |
2003年 | 12580篇 |
2002年 | 12455篇 |
2001年 | 13788篇 |
2000年 | 10409篇 |
1999年 | 8236篇 |
1998年 | 6892篇 |
1997年 | 6624篇 |
1996年 | 6392篇 |
1995年 | 5726篇 |
1994年 | 5671篇 |
1993年 | 5459篇 |
1992年 | 6064篇 |
1991年 | 6106篇 |
1990年 | 5853篇 |
1989年 | 5631篇 |
1988年 | 5662篇 |
1987年 | 5525篇 |
1986年 | 5234篇 |
1985年 | 6804篇 |
1984年 | 6908篇 |
1983年 | 5457篇 |
1982年 | 5562篇 |
1981年 | 5523篇 |
1980年 | 5121篇 |
1979年 | 5487篇 |
1978年 | 5646篇 |
1977年 | 5542篇 |
1976年 | 5446篇 |
1975年 | 5033篇 |
1974年 | 5024篇 |
1973年 | 4984篇 |
1972年 | 3530篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
Kurt M. Anstreicher 《Mathematical Programming》1997,76(1):245-263
We consider the construction of small step path following algorithms using volumetric, and mixed volumetric-logarithmic, barriers.
We establish quadratic convergence of a volumetric centering measure using pure Newton steps, enabling us to use relatively
standard proof techniques for several subsequently needed results. Using a mixed volumetric-logarithmic barrier we obtain
an O(n
1/4
m
1/4
L) iteration algorithm for linear programs withn variables andm inequality constraints, providing an alternative derivation for results first obtained by Vaidya and Atkinson. In addition,
we show that the same iteration complexity can be attained while holding the work per iteration to O(n
2
m), as opposed to O(nm
2), operations, by avoiding use of the true Hessian of the volumetric barrier. Our analysis also provides a simplified proof
of self-concordancy of the volumetric and mixed volumetric-logarithmic barriers, originally due to Nesterov and Nemirovskii.
This paper was first presented at the 1994 Faculty Research Seminar “Optimization in Theory and Practice”, at the University
of Iowa Center for Advanced Studies. 相似文献
942.
943.
It has been shown by Yu. M. Golubev, M. I. Kolobov, and I. V. Sokolov, Zh. éksp. Teor. Fiz. 111, 1579 (1997) [JETP 84, 864 (1997)], that when an optical cavity is excited by external radiation from a sub-Poisson laser the cavity mode may be
in either a sub-Poisson or a Poisson stationary state. This is not important for a resonant medium which is excited into the
upper laser level while interacting with this mode inside the cavity. The degree of regularity of the excitation will be identical
to that of the initial light flux incident on the cavity, and this ultimately ensures the same sub-Poisson lasing as for strictly
regular pumping of the resonant medium.
Zh. éksp. Teor. Fiz. 113, 1223–1234 (April 1998) 相似文献
944.
O. M. Kiselev 《Theoretical and Mathematical Physics》1998,114(1):81-89
We construct and asymptotic solution of the Cauchy problem for the Davey-Stewartson-I equation as t→∞. The solution, which
is of order t−1, is rapidly oscillating. The envelope of the oscillations can be defined by an integral equation.
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 114, No. 1, pp. 104–114, January, 1998. 相似文献
945.
946.
A. Sánchez-Lavega A. Salazar A. Ocariz L. Pottier E. Gomez L.M. Villar E. Macho 《Applied Physics A: Materials Science & Processing》1997,65(1):15-22
Received: 16 September 1996/Accepted: 6 January 1997 相似文献
947.
948.
949.
950.
Regularity of multiwavelets 总被引:7,自引:0,他引:7
The motivation for this paper is an interesting observation made by Plonka concerning the factorization of the matrix symbol associated with the refinement equation for B-splines with equally spaced multiple knots at integers and subsequent developments which relate this factorization to regularity of refinable vector fields over the real line. Our intention is to contribute to this train of ideas which is partially driven by the importance of refinable vector fields in the construction of multiwavelets. The use of subdivision methods will allow us to consider the problem almost entirely in the spatial domain and leads to exact characterizations of differentiability and Hölder regularity in arbitrary L p spaces. We first study the close relationship between vector subdivision schemes and a generalized notion of scalar subdivision schemes based on bi-infinite matrices with certain periodicity properties. For the latter type of subdivision scheme we will derive criteria for convergence and Hölder regularity of the limit function, which mainly depend on the spectral radius of a bi-infinite matrix induced by the subdivision operator, and we will show that differentiability of the limit functions can be characterized by factorization properties of the subdivision operator. By switching back to vector subdivision we will transfer these results to refinable vectors fields and obtain characterizations of regularity by factorization and spectral radius properties of the symbol associated to the refinable vector field. Finally, we point out how multiwavelets can be generated from orthonormal refinable bi-infinite vector fields. 相似文献