全文获取类型
收费全文 | 981篇 |
免费 | 38篇 |
国内免费 | 53篇 |
专业分类
化学 | 23篇 |
力学 | 50篇 |
综合类 | 7篇 |
数学 | 913篇 |
物理学 | 79篇 |
出版年
2023年 | 13篇 |
2022年 | 8篇 |
2021年 | 9篇 |
2020年 | 20篇 |
2019年 | 28篇 |
2018年 | 26篇 |
2017年 | 22篇 |
2016年 | 26篇 |
2015年 | 10篇 |
2014年 | 41篇 |
2013年 | 61篇 |
2012年 | 38篇 |
2011年 | 34篇 |
2010年 | 40篇 |
2009年 | 66篇 |
2008年 | 60篇 |
2007年 | 77篇 |
2006年 | 57篇 |
2005年 | 45篇 |
2004年 | 34篇 |
2003年 | 38篇 |
2002年 | 37篇 |
2001年 | 24篇 |
2000年 | 36篇 |
1999年 | 24篇 |
1998年 | 20篇 |
1997年 | 28篇 |
1996年 | 19篇 |
1995年 | 20篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 15篇 |
1984年 | 4篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1973年 | 1篇 |
1971年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有1072条查询结果,搜索用时 15 毫秒
31.
Cheng-Feng Lee Leevan Ling Robert Schaback 《Advances in Computational Mathematics》2009,30(4):339-354
In this paper, we are interested in some convergent formulations for the unsymmetric collocation method or the so-called Kansa’s method. We review some newly developed theories on solvability and convergence. The rates of convergence of these variations of Kansa’s method are examined and verified in arbitrary–precision computations. Numerical examples confirm with the theories that the modified Kansa’s method converges faster than the interpolant to the solution; that is, exponential convergence for the multiquadric and Gaussian radial basis functions (RBFs). Some numerical algorithms are proposed for efficiency and accuracy in practical applications of Kansa’s method. In double–precision, even for very large RBF shape parameters, we show that the modified Kansa’s method, through a subspace selection using a greedy algorithm, can produce acceptable approximate solutions. A benchmark algorithm is used to verify the optimality of the selection process. 相似文献
32.
33.
Consider K ≥ 2 independent copies of the random walk on the symmetric group SN starting from the identity and generated by the products of either independent uniform transpositions or independent uniform neighbor transpositions. At any time $n\in \mathbb{N}$, let Gn be the subgroup of SN generated by the K positions of the chains. In the uniform transposition model, we prove that there is a cut‐off phenomenon at time N ln(N)/(2K) for the non‐existence of fixed point of Gn and for the transitivity of Gn, thus showing that these properties occur before the chains have reached equilibrium. In the uniform neighbor transposition model, a transition for the non‐existence of a fixed point of Gn appears at time of order $N^{1+\frac{2}{K}}$ (at least for K ≥ 3), but there is no cut‐off phenomenon. In the latter model, we recover a cut‐off phenomenon for the non‐existence of a fixed point at a time proportional to N by allowing the number K to be proportional to ln(N). The main tools of the proofs are spectral analysis and coupling techniques. © 2011 Wiley Periodicals, Inc. Random Struct. Alg., 2012 相似文献
34.
Tails of distributions having the form of the geometric convolution are considered. In the case of light-tailed summands,
a simple proof of the famous Cramér asymptotic formula is given via the change of probability measure. Some related results
are obtained, namely, bounds of the tails of geometric convolutions, expressions for the distribution of the 1st failure time
and failure rate in regenerative systems, and others. In the case of heavy-tailed summands, two-sided bounds of the tail of
the geometric convolution are given in the cases where the summands have either Pareto or Weibull distributions. The results
obtained have the property that the corresponding lower and upper bounds are tailed-equivalent.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
35.
We extend and generalize some results on bounding security prices under two stochastic volatility models that provide closed-form expressions for option prices. In detail, we compute analytical expressions for benchmark and standard good-deal bounds. For both models, our findings show that our benchmark results generate much tighter bounds. A deep analysis of the properties of option prices and bounds involving a sensitivity analysis and analytical derivation of Greeks for both option prices and bounds is also presented. These results provide strong practical applications taking into account the relevance of pricing and hedging strategies for traders, financial institutions, and risk managers. 相似文献
36.
The Goursat formula for the hypergeometric function extends the Euler–Gauss relation to the case of logarithmic singularities. 相似文献
37.
We here provide two sided bounds for the density of the solution of a system of n differential equations of dimension d, the first one being forced by a non-degenerate random noise and the n−1 other ones being degenerate. The system formed by the n equations satisfies a suitable Hörmander condition: the second equation feels the noise plugged into the first equation, the third equation feels the noise transmitted from the first to the second equation and so on … , so that the noise propagates one way through the system. When the coefficients of the system are Lipschitz continuous, we show that the density of the solution satisfies Gaussian bounds with non-diffusive time scales. The proof relies on the interpretation of the density of the solution as the value function of some optimal stochastic control problem. 相似文献
38.
The paper is devoted to a numerical limit analysis of a hollow spheroidal model with a von Mises solid matrix. To this purpose, existing kinematic and static 3D-FEM codes for the case of spherical cavities have been modified and improved to account for the model of a spheroidal cavity confocal with the external spheroidal boundary. The optimized conic programming formulations and the resulting codes appear to be very efficient. This framework is then applied to the derivation of numerical upper and lower anisotropic bounds in the case of an oblate void. The numerical results obtained from a series of tests are presented and allow to assess the accuracy of closed-form expressions of the macroscopic criteria proposed by
[Gologanu et al., 1994] and [Gologanu et al., 1997] for porous media with oblate voids. 相似文献
39.
Both necessary and sufficient conditions for the existence of two complementary-dual extremum principles for geometrically exact finite strain (one-dimensional) beam models are investigated by means of two different approaches. One is based on the results published by Gao and Strang, and the other relies on the approach proposed by Noble and Sewell. While the former is limited to beam models restricted to moderate large deformations, the latter is valid for arbitrarily large deformations (and strains). The numerical implementation of the complementary-dual extremum principles can lead to simple true global upper bounds of the error of the approximate solutions. 相似文献
40.
Monica Marras Stella Vernier‐Piro Giuseppe Viglialoro 《Mathematical Methods in the Applied Sciences》2016,39(11):2787-2798
This paper deals with a parabolic–parabolic Keller–Segel‐type system in a bounded domain of , {N = 2;3}, under different boundary conditions, with time‐dependent coefficients and a positive source term. The solutions may blow up in finite time t?; and under appropriate assumptions on data, explicit lower bounds for blow‐up time are obtained when blow up occurs. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献