全文获取类型
收费全文 | 13144篇 |
免费 | 342篇 |
国内免费 | 254篇 |
专业分类
化学 | 1838篇 |
晶体学 | 56篇 |
力学 | 92篇 |
综合类 | 109篇 |
数学 | 10848篇 |
物理学 | 797篇 |
出版年
2023年 | 23篇 |
2022年 | 121篇 |
2021年 | 127篇 |
2020年 | 100篇 |
2019年 | 237篇 |
2018年 | 289篇 |
2017年 | 181篇 |
2016年 | 165篇 |
2015年 | 182篇 |
2014年 | 307篇 |
2013年 | 735篇 |
2012年 | 426篇 |
2011年 | 680篇 |
2010年 | 693篇 |
2009年 | 920篇 |
2008年 | 900篇 |
2007年 | 887篇 |
2006年 | 633篇 |
2005年 | 481篇 |
2004年 | 399篇 |
2003年 | 337篇 |
2002年 | 312篇 |
2001年 | 314篇 |
2000年 | 357篇 |
1999年 | 350篇 |
1998年 | 353篇 |
1997年 | 299篇 |
1996年 | 237篇 |
1995年 | 244篇 |
1994年 | 248篇 |
1993年 | 241篇 |
1992年 | 238篇 |
1991年 | 180篇 |
1990年 | 184篇 |
1989年 | 197篇 |
1988年 | 128篇 |
1987年 | 117篇 |
1986年 | 132篇 |
1985年 | 112篇 |
1984年 | 130篇 |
1983年 | 48篇 |
1982年 | 107篇 |
1981年 | 62篇 |
1980年 | 100篇 |
1979年 | 74篇 |
1978年 | 79篇 |
1977年 | 34篇 |
1976年 | 15篇 |
1975年 | 5篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
11.
Summary. Let be a square matrix dependent on parameters and , of which we choose as the eigenvalue parameter. Many computational problems are equivalent to finding a point such that has a multiple eigenvalue at . An incomplete decomposition of a matrix dependent on several parameters is proposed. Based on the developed theory two new algorithms are
presented for computing multiple eigenvalues of with geometric multiplicity . A third algorithm is designed for the computation of multiple eigenvalues with geometric multiplicity but which also appears to have local quadratic convergence to semi-simple eigenvalues. Convergence analyses of these methods
are given. Several numerical examples are presented which illustrate the behaviour and applications of our methods.
Received December 19, 1994 / Revised version received January 18, 1996 相似文献
12.
Summary Consider the solution of one-dimensional linear initial-boundary value problems by a finite element method of lines using a piecewiseP
th
-degree polynomial basis. A posteriori estimates of the discretization error are obtained as the solutions of either local parabolic or local elliptic finite element problems using piecewise polynomial corrections of degreep+1 that vanish at element ends. Error estimates computed in this manner are shown to converge in energy under mesh refinement to the exact finite element discretization error. Computational results indicate that the error estimates are robust over a wide range of mesh spacings and polynomial degrees and are, furthermore, applicable in situations that are not supported by the analysis.This research was partially supported by the U.S. Air Force Office of Scientific Research, Air Force Systems Command, USAF, under Grant Number AFOSR 90-0194; by the U.S. Army Research Office under Contract Number DAAL03-91-G-0215; and by the National Science Foundation under Institutional Infrastructure Grant Number CDA-8805910 相似文献
13.
Summary In the analysis of discretization methods for stiff intial value problems, stability questions have received most part of the attention in the past.B-stability and the equivalent criterion algebraic stability are well known concepts for Runge-Kutta methods applied to dissipative problems. However, for the derivation ofB-convergence results — error bounds which are not affected by stiffness — it is not sufficient in many cases to requireB-stability alone. In this paper, necessary and sufficient conditions forB-convergence are determined.This paper was written while J. Schneid was visiting the Centre for Mathematics and Computer Science with an Erwin-Schrödinger stipend from the Fonds zur Förderung der wissenschaftlichen Forschung 相似文献
14.
Summary We present an approximation method of a space-homogeneous transport equation which we prove is convergent. The method is very promising for numerical computation. Comparison of a numerical computation with an exact solution is given for the Master equation. 相似文献
15.
The interferometric intensity patterns from a 2D shearing interferometer are shown and discussed. The intensity patterns can be obtained in two different approaches incorporating differential and extended wavefront controlled displacements. The reliable directional sensitivity of this interferometer allows the optimization of the measurement parameters to estimate the wavefront of the intensity patterns by regularization techniques. 相似文献
16.
Let T and S be invertible measure preserving transformations of a probability measure space (X, ℬ, μ). We prove that if the group generated by T and S is nilpotent, then exists in L
2-norm for any u, v∈L
∞(X, ℬ, μ). We also show that for A∈ℬ with μ(A)>0 one has . By the way of contrast, we bring examples showing that if measure preserving transformations T, S generate a solvable group, then (i) the above limits do not have to exist; (ii) the double recurrence property fails, that
is, for some A∈ℬ, μ(A)>0, one may have μ(A∩T
-n
A∩S
-
n
A)=0 for all n∈ℕ. Finally, we show that when T and S generate a nilpotent group of class ≤c, in L
2(X) for all u, v∈L
∞(X) if and only if T×S is ergodic on X×X and the group generated by T
-1
S, T
-2
S
2,..., T
-c
S
c
acts ergodically on X.
Oblatum 19-V-2000 & 5-VII-2001?Published online: 12 October 2001 相似文献
17.
Summary In 1980 Dahmen-DeVore-Scherer introduced a modulus of continuity which turns out to reflect invariance properties of compound cubature rules effectively. Accordingly, sharp error bounds are derived, the existence of relevant counterexamples being a consequence of a quantitative resonance principle, established previously. 相似文献
18.
Saida Sultanic 《Integral Equations and Operator Theory》2006,55(4):573-595
The central question of this paper is the one of finding the right analogue of the Commutant Lifting Theorem for the Bergman
space La2. We also analyze the analogous problem for weighted Bergman spaces La,α2, − 1 < α < ∞. 相似文献
19.
Michel Hébert 《Archive for Mathematical Logic》1991,31(2):133-143
Summary We give a syntactic characterization of (finitary) theories whose categories of models are closed under the formation of connected limits (respectively the formation of pullbacks and substructures) in the category of all structures. They are also those theories whose consistent extensions by new atomic facts admit in each component an initial structure (respectively an initial term structure), and also thoseT for whichM(T) is locally finitely multi-presentable in a canonical way. We also show that these two properties of theories are nonuniform. 相似文献
20.
Wu Hongyi 《高校应用数学学报(英文版)》2006,21(1):96-106
A family of Said-Bézier type generalized Ball (SBGB) bases and surfaces with a parameter H over triangular domain is introduced, which unifies Bézier surface and Said-Ball surface and includes several intermediate
surfaces. To convert different bases and surfaces, the dual functionals of bases are presented. As an application of dual
functionals, the subdivision formulas for surfaces are established. 相似文献