全文获取类型
收费全文 | 4592篇 |
免费 | 449篇 |
国内免费 | 462篇 |
专业分类
化学 | 257篇 |
晶体学 | 15篇 |
力学 | 285篇 |
综合类 | 112篇 |
数学 | 4138篇 |
物理学 | 696篇 |
出版年
2024年 | 3篇 |
2023年 | 60篇 |
2022年 | 78篇 |
2021年 | 92篇 |
2020年 | 137篇 |
2019年 | 133篇 |
2018年 | 138篇 |
2017年 | 137篇 |
2016年 | 147篇 |
2015年 | 98篇 |
2014年 | 202篇 |
2013年 | 404篇 |
2012年 | 189篇 |
2011年 | 242篇 |
2010年 | 227篇 |
2009年 | 282篇 |
2008年 | 291篇 |
2007年 | 308篇 |
2006年 | 304篇 |
2005年 | 271篇 |
2004年 | 228篇 |
2003年 | 206篇 |
2002年 | 210篇 |
2001年 | 166篇 |
2000年 | 151篇 |
1999年 | 142篇 |
1998年 | 106篇 |
1997年 | 90篇 |
1996年 | 84篇 |
1995年 | 66篇 |
1994年 | 66篇 |
1993年 | 32篇 |
1992年 | 31篇 |
1991年 | 21篇 |
1990年 | 23篇 |
1989年 | 7篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 23篇 |
1985年 | 23篇 |
1984年 | 15篇 |
1983年 | 13篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 2篇 |
1978年 | 4篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1957年 | 3篇 |
1936年 | 1篇 |
排序方式: 共有5503条查询结果,搜索用时 15 毫秒
71.
The Secondary Bifurcation of an Aeroelastic Airfoil Motion: Effect of High Harmonics 总被引:6,自引:0,他引:6
The nonlinear dynamical response of a two-degree-of-freedom aeroelastic airfoil motion with cubic restoring forces is investigated. A secondary bifurcation after the primary Hopf (flutter) bifurcation is detected for a cubic hard spring in the pitch degree-of-freedom. Furthermore, there is a hysteresis in the secondary bifurcation: starting from different initial conditions the motion may jump from one limit cycle to another at different fluid flow velocities. A high-order harmonic balance method is employed to investigate the possible bifurcation branches. Furthermore, a numerical time simulation procedure is used to confirm the stable and unstable bifurcation branches. 相似文献
72.
Giulio Peruginelli 《代数通讯》2015,43(1):197-211
We describe an algorithm to compute the different factorizations of a given image primitive integer-valued polynomial f(X) = g(X)/d ∈ ?[X], where g ∈ ?[X] and d ∈ ? is square-free, assuming that the factorizations of g(X) in ?[X] and d in ? are known. We translate this problem into a combinatorial one. 相似文献
73.
We present here a fine singularity analysis of solutions to the Laplace equation in special polygonal domains in the plane. We assume piecewise constant Neumann data on one component of the boundary. Our motivation is to study the so‐called Berg effect, which is explained in the introduction. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
74.
Stability and bifurcations analysis of a competition model with piecewise constant arguments 下载免费PDF全文
In this paper, we investigate local and global asymptotic stability of a positive equilibrium point of system of differential equations where t ≥ 0, the parameters r1, k1, α1, α2, r2, k2, and d1 are positive, and [t] denotes the integer part of t ∈ [0, ∞ ). x(t) and y(t) represent population density for related species. Sufficient conditions are obtained for the local and global stability of the positive equilibrium point of the corresponding difference system. We show through numerical simulations that periodic solutions arise through Neimark–Sacker bifurcation. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
75.
Eckhard Steffen 《Journal of Graph Theory》2015,78(3):195-206
Let G be a bridgeless cubic graph. Consider a list of k 1‐factors of G. Let be the set of edges contained in precisely i members of the k 1‐factors. Let be the smallest over all lists of k 1‐factors of G. Any list of three 1‐factors induces a core of a cubic graph. We use results on the structure of cores to prove sufficient conditions for Berge‐covers and for the existence of three 1‐factors with empty intersection. Furthermore, if , then is an upper bound for the girth of G. We also prove some new upper bounds for the length of shortest cycle covers of bridgeless cubic graphs. Cubic graphs with have a 4‐cycle cover of length and a 5‐cycle double cover. These graphs also satisfy two conjectures of Zhang 18 . We also give a negative answer to a problem stated in 18 . 相似文献
76.
Interpolating minimal energy C1‐Surfaces on Powell–Sabin Triangulations: Application to the resolution of elliptic problems 下载免费PDF全文
M. A. Fortes P. González M. J. Ibáñez M. Pasadas 《Numerical Methods for Partial Differential Equations》2015,31(3):798-821
In this article, we present a method to obtain a C1‐surface, defined on a bounded polygonal domain Ω, which interpolates a specific dataset and minimizes a certain “energy functional.” The minimization space chosen is the one associated to the Powell–Sabin finite element, whose elements are C1‐quadratic splines. We develop a general theoretical framework for that, and we consider two main applications of the theory. For both of them, we give convergence results, and we present some numerical and graphical examples. © 2014 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 31: 798–821, 2015 相似文献
77.
Selberg-type integrals that can be turned into constant term identities for Laurent polynomials arise naturally in conjunction with random matrix models in statistical mechanics. Built on a recent idea of Karasev and Petrov we develop a general interpolation based method that is powerful enough to establish many such identities in a simple manner. The main consequence is the proof of a conjecture of Forrester related to the Calogero–Sutherland model. In fact we prove a more general theorem, which includes Aomoto's constant term identity at the same time. We also demonstrate the relevance of the method in additive combinatorics. 相似文献
78.
The mixed moments for the Askey–Wilson polynomials are found using a bootstrapping method and connection coefficients. A similar bootstrapping idea on generating functions gives a new Askey–Wilson generating function. Modified generating functions of orthogonal polynomials are shown to generate polynomials satisfying recurrences of known degree greater than three. An important special case of this hierarchy is a polynomial which satisfies a four term recurrence, and its combinatorics is studied. 相似文献
79.
We establish various properties for the zero sets of three families of bivariate Hermite polynomials. Special emphasis is given to those bivariate orthogonal polynomials introduced by Hermite by means of a Rodrigues type formula related to a general positive definite quadratic form. For this family we prove that the zero set of the polynomial of total degree n+m consists of exactly n+m disjoint branches and possesses n+m asymptotes. A natural extension of the notion of interlacing is introduced and it is proved that the zero sets of the family under discussion obey this property. The results show that the properties of the zero sets, considered as affine algebraic curves in R2, are completely different for the three families analyzed. 相似文献
80.
This paper introduces a new framework for implicit restarting of the Krylov–Schur algorithm. It is shown that restarting with arbitrary polynomial filter is possible by reassigning some of the eigenvalues of the Rayleigh quotient through a rank‐one correction, implemented using only the elementary transformations (translation and similarity) of the Krylov decomposition. This framework includes the implicitly restarted Arnoldi (IRA) algorithm and the Krylov–Schur algorithm with implicit harmonic restart as special cases. Further, it reveals that the IRA algorithm can be turned into an eigenvalue assignment method. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献