全文获取类型
收费全文 | 9849篇 |
免费 | 279篇 |
国内免费 | 230篇 |
专业分类
化学 | 1817篇 |
晶体学 | 89篇 |
力学 | 42篇 |
综合类 | 18篇 |
数学 | 7301篇 |
物理学 | 1091篇 |
出版年
2023年 | 48篇 |
2022年 | 83篇 |
2021年 | 76篇 |
2020年 | 101篇 |
2019年 | 234篇 |
2018年 | 224篇 |
2017年 | 130篇 |
2016年 | 104篇 |
2015年 | 136篇 |
2014年 | 281篇 |
2013年 | 547篇 |
2012年 | 281篇 |
2011年 | 622篇 |
2010年 | 505篇 |
2009年 | 596篇 |
2008年 | 650篇 |
2007年 | 703篇 |
2006年 | 521篇 |
2005年 | 358篇 |
2004年 | 309篇 |
2003年 | 299篇 |
2002年 | 278篇 |
2001年 | 190篇 |
2000年 | 201篇 |
1999年 | 267篇 |
1998年 | 274篇 |
1997年 | 210篇 |
1996年 | 218篇 |
1995年 | 267篇 |
1994年 | 212篇 |
1993年 | 202篇 |
1992年 | 186篇 |
1991年 | 101篇 |
1990年 | 101篇 |
1989年 | 116篇 |
1988年 | 70篇 |
1987年 | 56篇 |
1986年 | 59篇 |
1985年 | 77篇 |
1984年 | 78篇 |
1983年 | 58篇 |
1982年 | 73篇 |
1981年 | 47篇 |
1980年 | 44篇 |
1979年 | 44篇 |
1978年 | 44篇 |
1977年 | 19篇 |
1976年 | 19篇 |
1975年 | 12篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Let E\subset \Bbb R
s
be compact and let d
n
E
denote the dimension of the space of polynomials of degree at most n in s variables restricted to E . We introduce the notion of an asymptotic interpolation measure (AIM). Such a measure, if it exists , describes the asymptotic behavior of any scheme τ
n
={ \bf x
k,n
}
k=1
dnE
, n=1,2,\ldots , of nodes for multivariate polynomial interpolation for which the norms of the corresponding interpolation operators do
not grow geometrically large with n . We demonstrate the existence of AIMs for the finite union of compact subsets of certain algebraic curves in R
2
. It turns out that the theory of logarithmic potentials with external fields plays a useful role in the investigation. Furthermore,
for the sets mentioned above, we give a computationally simple construction for ``good' interpolation schemes.
November 9, 2000. Date revised: August 4, 2001. Date accepted: September 14, 2001. 相似文献
52.
Emulsions of perfluorotributylamine (FTBA) and perflubron were evaluated for their utility in 19F echo planar imaging. Fluorine images of the emulsions were obtained in a phantom and two mice that had been predosed. Both agents, but particularly perflubron, show potential for fluorine echo planar studies because of the long spin-spin relaxation times of the CF3 resonances. High resolution thin slice images obtained in as little as 26.6 ms are presented. 相似文献
53.
Summary. This paper introduces and analyzes the convergence properties of a method that computes an approximation to the invariant
subspace associated with a group of eigenvalues of a large not necessarily diagonalizable matrix. The method belongs to the
family of projection type methods. At each step, it refines the approximate invariant subspace using a linearized Riccati's
equation which turns out to be the block analogue of the correction used in the Jacobi-Davidson method. The analysis conducted
in this paper shows that the method converges at a rate quasi-quadratic provided that the approximate invariant subspace is
close to the exact one. The implementation of the method based on multigrid techniques is also discussed and numerical experiments
are reported.
Received June 15, 2000 / Revised version received January 22, 2001 / Published online October 17, 2001 相似文献
54.
Jaana Eloranta 《BIT Numerical Mathematics》1991,31(4):576-590
Labeled transition systems (lts) provide an operational semantics for many specification languages. In order to abstract unrelevant details of lts's, manybehavioural equivalences have been defined; here observation equivalence is considered. We are interested in the following problem:Given a finite lts, which is the minimal observation equivalent lts corresponding to it? It is well known that the number of states of an lts can be minimized by applying arelational coarsest partition algorithm. However, the obtained lts is not unique (up to the renaming of the states): for an lts there may exist several observation equivalent lts's which have the minimal number of states but varying number of transitions. In this paper we show how the number of transitions can be minimized, obtaining a unique lts. 相似文献
55.
56.
Yuri Borovskikh 《Acta Appl Math》1994,35(3):213-298
U-statistics in Banach spaces are considered and thoroughly investigated. The martingale structure, estimates of moments, the law of large numbers, the central limit theorem, the invariance principle, estimates of the rate of convergence, and large deviations are established 相似文献
57.
58.
We study the tangent space at a monomial point M in the Hilbert scheme that parameterizes all ideals with the same Hilbert function as M over an exterior algebra. 相似文献
59.
Shuguang Wang 《Geometriae Dedicata》1995,57(2):207-215
We classify, in terms of simple algebraic equations, the fixed point sets of the moduli space of stable bundles over genus 2 curves with anti-holomorphic involutions.Research supported by SRF of University of Missouri. 相似文献
60.
In this paper we design a fast new algorithm for reducing an N × N quasiseparable matrix to upper Hessenberg form via a sequence of N − 2 unitary transformations. The new reduction is especially useful when it is followed by the QR algorithm to obtain a complete set of eigenvalues of the original matrix. In particular, it is shown that in a number of cases some recently devised fast adaptations of the QR method for quasiseparable matrices can benefit from using the proposed reduction as a preprocessing step, yielding lower cost and a simplification of implementation. 相似文献