全文获取类型
收费全文 | 1888篇 |
免费 | 528篇 |
国内免费 | 76篇 |
专业分类
化学 | 144篇 |
晶体学 | 1篇 |
力学 | 423篇 |
综合类 | 56篇 |
数学 | 899篇 |
物理学 | 969篇 |
出版年
2024年 | 3篇 |
2023年 | 16篇 |
2022年 | 35篇 |
2021年 | 74篇 |
2020年 | 75篇 |
2019年 | 60篇 |
2018年 | 57篇 |
2017年 | 104篇 |
2016年 | 111篇 |
2015年 | 78篇 |
2014年 | 113篇 |
2013年 | 135篇 |
2012年 | 152篇 |
2011年 | 129篇 |
2010年 | 101篇 |
2009年 | 104篇 |
2008年 | 132篇 |
2007年 | 104篇 |
2006年 | 95篇 |
2005年 | 106篇 |
2004年 | 88篇 |
2003年 | 77篇 |
2002年 | 68篇 |
2001年 | 77篇 |
2000年 | 61篇 |
1999年 | 53篇 |
1998年 | 46篇 |
1997年 | 51篇 |
1996年 | 40篇 |
1995年 | 31篇 |
1994年 | 20篇 |
1993年 | 17篇 |
1992年 | 13篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1959年 | 1篇 |
排序方式: 共有2492条查询结果,搜索用时 250 毫秒
141.
Genetic algorithms are adaptive sampling strategies based on information processing models from population genetics. Because they are able to sample a population broadly, they have the potential to out-perform existing heuristics for certain difficult classes of location problems. This paper describes reproductive plans in the context of adaptive optimization methods, and details the three genetic operators which are the core of the reproductive design. An algorithm is presented to illustrate applications to discrete-space location problems, particularly thep-median. The algorithm is unlikely to compete in terms of efficiency with existingp-median heuristics. However, it is highly general and can be fine-tuned to maximize computational efficiency for any specific problem class. 相似文献
142.
Akihiko Inoue 《Journal of Mathematical Analysis and Applications》2003,286(1):237-247
We study continuous coherent risk measures on Lp, in particular, the worst conditional expectations. We show some representation theorems for them, extending the results of Artzner, Delbaen, Eber, Heath, and Kusuoka. 相似文献
143.
J. Hoffman 《国际流体数值方法杂志》2009,59(11):1241-1258
General Galerkin (G2) is a new computational method for turbulent flow, where a stabilized Galerkin finite element method is used to compute approximate weak solutions to the Navier–Stokes equations directly, without any filtering of the equations as in a standard approach to turbulence simulation, such as large eddy simulation, and thus no Reynolds stresses are introduced, which need modelling. In this paper, G2 is used to compute the drag coefficient cD for the flow past a circular cylinder at Reynolds number Re=3900, for which the flow is turbulent. It is found that it is possible to approximate cD to an accuracy of a few percent, corresponding to the accuracy in experimental results for this problem, using less than 105 mesh points, which makes the simulations possible using a standard PC. The mesh is adaptively refined until a stopping criterion is reached with respect to the error in a chosen output of interest, which in this paper is cD. Both the stopping criterion and the mesh‐refinement strategy are based on a posteriori error estimates, in the form of a space–time integral of residuals times derivatives of the solution of a dual problem, linearized at the approximate solution, and with data coupling to the output of interest. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
144.
Graph Coloring with Adaptive Evolutionary Algorithms 总被引:4,自引:0,他引:4
This paper presents the results of an experimental investigation on solving graph coloring problems with Evolutionary Algorithms (EAs). After testing different algorithm variants we conclude that the best option is an asexual EA using order-based representation and an adaptation mechanism that periodically changes the fitness function during the evolution. This adaptive EA is general, using no domain specific knowledge, except, of course, from the decoder (fitness function). We compare this adaptive EA to a powerful traditional graph coloring technique DSatur and the Grouping Genetic Algorithm (GGA) on a wide range of problem instances with different size, topology and edge density. The results show that the adaptive EA is superior to the Grouping (GA) and outperforms DSatur on the hardest problem instances. Furthermore, it scales up better with the problem size than the other two algorithms and indicates a linear computational complexity. 相似文献
145.
AnInequalityofMatrixandBayesUnbiasedEstimatesZhangYaoting(ShanghaiUniversityofFinanceandEconomics,200433)AbstractTheinequali... 相似文献
146.
147.
Wataru Sakamoto 《Computational Statistics》2007,22(4):583-597
An empirical Bayes method to select basis functions and knots in multivariate adaptive regression spline (MARS) is proposed,
which takes both advantages of frequentist model selection approaches and Bayesian approaches. A penalized likelihood is maximized
to estimate regression coefficients for selected basis functions, and an approximated marginal likelihood is maximized to
select knots and variables involved in basis functions. Moreover, the Akaike Bayes information criterion (ABIC) is used to
determine the number of basis functions. It is shown that the proposed method gives estimation of regression structure that
is relatively parsimonious and more stable for some example data sets. 相似文献
148.
在对定速风力发电机建模的基础上,设计了模型参考自适应控制器,并进行了跟随性能和抗干扰性能仿真,仿真结果表明自适应控制器的自适应能力很好. 相似文献
149.
ARMAX系统不外加输入激励的辨识 总被引:1,自引:0,他引:1
本文在不外加输入激励情况下,讨论了开环不稳定和非最小相位的ARMAX系统系数的一致估计.所用方法是用适应镇定的办法,使得闭环系统成为平稳可逆的ARMA过程,然后利用Yule-Walker方程给出闭环系统系数的一致估计,而把求开环系统系数的一致估计归结为解一组线性代数方程。 相似文献
150.