全文获取类型
收费全文 | 2329篇 |
免费 | 67篇 |
国内免费 | 14篇 |
专业分类
化学 | 1661篇 |
晶体学 | 10篇 |
力学 | 35篇 |
数学 | 442篇 |
物理学 | 232篇 |
综合类 | 30篇 |
出版年
2023年 | 14篇 |
2022年 | 23篇 |
2021年 | 39篇 |
2020年 | 43篇 |
2019年 | 44篇 |
2018年 | 23篇 |
2017年 | 20篇 |
2016年 | 65篇 |
2015年 | 39篇 |
2014年 | 50篇 |
2013年 | 74篇 |
2012年 | 109篇 |
2011年 | 109篇 |
2010年 | 54篇 |
2009年 | 79篇 |
2008年 | 133篇 |
2007年 | 108篇 |
2006年 | 107篇 |
2005年 | 96篇 |
2004年 | 88篇 |
2003年 | 94篇 |
2002年 | 95篇 |
2001年 | 40篇 |
2000年 | 59篇 |
1999年 | 34篇 |
1998年 | 47篇 |
1997年 | 50篇 |
1996年 | 46篇 |
1995年 | 35篇 |
1994年 | 44篇 |
1993年 | 32篇 |
1992年 | 25篇 |
1991年 | 35篇 |
1990年 | 24篇 |
1989年 | 19篇 |
1988年 | 30篇 |
1987年 | 24篇 |
1986年 | 16篇 |
1985年 | 26篇 |
1984年 | 40篇 |
1983年 | 25篇 |
1982年 | 35篇 |
1981年 | 32篇 |
1980年 | 26篇 |
1979年 | 16篇 |
1978年 | 15篇 |
1977年 | 18篇 |
1976年 | 17篇 |
1975年 | 10篇 |
1973年 | 7篇 |
排序方式: 共有2410条查询结果,搜索用时 0 毫秒
111.
We deal with the iterative solution of linear systems arising from so-called dual-dual mixed finite element formulations. The linear systems are of a two-fold saddle point structure; they are indefinite and ill-conditioned. We define a special inner product that makes matrices of the two-fold saddle point structure, after a specific transformation, symmetric and positive definite. Therefore, the conjugate gradient method with this special inner product can be used as iterative solver. For a model problem, we propose a preconditioner which leads to a bounded number of CG-iterations. Numerical experiments for our model problem confirming the theoretical results are also reported.
112.
We show that each elation generalized quadrangle with parameters (p, p), where p is a prime, is isomorphic to the symplectic quadrangle W(p) or its dual Q(4, p). Our results cover the more general case of linearly small elation generalized quadrangles. In particular, we obtain a characterization of the symplectic quadrangle over the field of complex numbers among compact connected quadrangles. We prove that every root elation quadrangle (Q, c, H F ) is a skew translation quadrangle. 相似文献
113.
Asymptotically harmonic manifolds are simply connected complete Riemannian manifolds without conjugate points such that all horospheres have the same constant mean curvature \(h\). In this article we present results for harmonic functions on rank one asymptotically harmonic manifolds \(X\) with mild curvature boundedness conditions. Our main results are (a) the explicit calculation of the Radon–Nikodym derivative of the visibility measures, (b) an explicit integral representation for the solution of the Dirichlet problem at infinity in terms of these visibility measures, and (c) a result on horospherical means of bounded eigenfunctions implying that these eigenfunctions do not admit non-trivial continuous extensions to the geometric compactification \(\overline{X}\). 相似文献
114.
Nathan Barker Nigel Boston Norbert Peyerimhoff Alina Vdovina 《Monatshefte für Mathematik》2012,3(2):319-327
We find new mixed and unmixed Beauville structures for groups constructed as 2-quotients, i.e. quotients of 2-power order, of the fundamental group of a certain simplicial complex. 相似文献
115.
Norbert Polat 《Czechoslovak Mathematical Journal》2001,51(3):477-492
For an end and a tree T of a graph G we denote respectively by m() and m
T
() the maximum numbers of pairwise disjoint rays of G and T belonging to , and we define tm() := min{m
T(): T is a spanning tree of G}. In this paper we give partial answers — affirmative and negative ones — to the general problem of determining if, for a function f mapping every end of G to a cardinal f() such that tm() f() m(), there exists a spanning tree T of G such that m
T
() = f() for every end of G. 相似文献
116.
We investigate the minimum residual method for symmetric, indefinite linear systems of a so‐called dual–dual structure. These systems arise when using a combined dual‐mixed finite element method with a Dirichlet‐to‐Neumann mapping to solve a class of exterior transmission problems. As a model problem we consider an elliptic equation of divergence form coupled with the Laplace equation in an unbounded region of the plane. We give abstract convergence results for the preconditioned minimum residual method for the solution of linear systems of the special dual–dual structure. For our model problem, we show that this iterative method provides an efficient solution procedure where standard preconditioners can directly be used. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
117.
Forecasting of the sea level plays a key role to control on- and offshore facilities. First, we start with a determinstic time series method based on the state space embedding to determine the vector field of the nonlinear dynamical system and deduce the solution of its corresponding high-order differential equation. Second, We assume that the sea state is a stochastic process governed by a deterministic part and by noise so that this dynamical system can be modelled by the Langevin equation. We extract the nonlinear dynamical system considering fluctuations directly from a measured time series by estimating the drift vector and the diffusion matrix of the Fokker-Planck equation. In order to determine the prediction accuracy, the numerical solutions of the deterministic model and the Langevin equation are compared to the data values at future time. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
118.
Norbert Seifter 《Combinatorica》1984,4(4):351-356
LexX be anm-connected infinite graph without subgraphs homeomorphic toKm, n, for somen, and let α be an automorphism ofX with at least one cycle of infinite length. We characterize the structure of α and use this characterization to extend a
known result about orientation-preserving automorphisms of finite plane graphs to infinite plane graphs. In the last section
we investigate the action of α on the ends ofX and show that α fixes at most two ends (Theorem 3.2). 相似文献
119.
Norbert Brunner 《Archive for Mathematical Logic》1984,24(1):119-135
A set is amorphous, if it is not a union of two disjoint infinite subsets. The following variants of the Tychonoff product theorem are investigated in the hierarchy of weak choice principles. TA1: An amorphous power of a compactT
2 space is compact. TA2: An amorphous power of a compactT
2 space which as a set is wellorderable is compact. In ZF0TA1 is equivalent to the assertion, that amorphous sets are finite. RT is Ramsey's theorem, that every finite colouring of the set ofn-element subsets of an infinite set has an infinite homogeneous subset and PW is Rubin's axiom, that the power set of an ordinal is wellorderable. In ZF0RT+PW implies TA2. Since RT+PW is compatible with the existence of infinite amorphous sets, TA2 does not imply TA1 in ZF0. But TA2 cannot be proved in ZF0 alone. As an application, we prove a theorem of Stone, using a weak wellordering axiomD
3 (a set is wellorderable, if each of its infinite subsets is structured) together with RT.
Diese Arbeit ist Teil der Habilitationsschrift des Verfassers im Fachgebiet Mathematische Analysis an der Technischen Universität Wien. 相似文献
120.
John Koker Norbert J. Kuenzi Asuman Okta Rochelle Leibowitz Lowell Carmony 《School science and mathematics》1998,98(1):4-11
In The Handbook of Integer Sequence Numbers by N. J. Sloane (1973) , the sequences of integers known as the Catalan numbers and the Bell numbers are called sequences 577 and 585, respectively. In this paper, several problems in which these sequences arise are investigated. These problems are appropriate for both pre- and in-service teachers, as well as students studying discrete mathematics. 相似文献