全文获取类型
收费全文 | 9730篇 |
免费 | 1181篇 |
国内免费 | 461篇 |
专业分类
化学 | 879篇 |
晶体学 | 17篇 |
力学 | 1078篇 |
综合类 | 343篇 |
数学 | 6202篇 |
物理学 | 2853篇 |
出版年
2024年 | 21篇 |
2023年 | 94篇 |
2022年 | 297篇 |
2021年 | 286篇 |
2020年 | 205篇 |
2019年 | 227篇 |
2018年 | 249篇 |
2017年 | 363篇 |
2016年 | 458篇 |
2015年 | 305篇 |
2014年 | 571篇 |
2013年 | 667篇 |
2012年 | 513篇 |
2011年 | 579篇 |
2010年 | 466篇 |
2009年 | 615篇 |
2008年 | 630篇 |
2007年 | 639篇 |
2006年 | 517篇 |
2005年 | 473篇 |
2004年 | 415篇 |
2003年 | 372篇 |
2002年 | 331篇 |
2001年 | 284篇 |
2000年 | 247篇 |
1999年 | 222篇 |
1998年 | 211篇 |
1997年 | 183篇 |
1996年 | 152篇 |
1995年 | 118篇 |
1994年 | 80篇 |
1993年 | 94篇 |
1992年 | 82篇 |
1991年 | 49篇 |
1990年 | 49篇 |
1989年 | 35篇 |
1988年 | 33篇 |
1987年 | 30篇 |
1986年 | 33篇 |
1985年 | 38篇 |
1984年 | 33篇 |
1983年 | 14篇 |
1982年 | 21篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1959年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
991.
Tzyy-Chyang LuJyh-Ching Juang 《Applied mathematics and computation》2011,218(6):2516-2532
This work presents the evolutionary quantum-inspired space search algorithm (QSSA) for solving numerical optimization problems. In the proposed algorithm, the feasible solution space is decomposed into regions in terms of quantum representation. As the search progresses from one generation to the next, the quantum bits evolve gradually to increase the probability of selecting the regions that render good fitness values. Through the inherent probabilistic mechanism, the QSSA initially behaves as a global search algorithm and gradually evolves into a local search algorithm, yielding a good balance between exploration and exploitation. To prevent a premature convergence and to speed up the overall search speed, an overlapping strategy is also proposed. The QSSA is applied to a series of numerical optimization problems. The experiments show that the results obtained by the QSSA are quite competitive compared to those obtained using state-of-the-art IPOP-CMA-ES and QEA. 相似文献
992.
A discretization algorithm is proposed by Haar wavelet approximation theory for the fractional order integral. In this paper, the integration time is divided into two parts, one presents the effect of the past sampled data, calculated by the iterative method, and the other presents the effect of the recent sampled data at a fixed time interval, calculated by the Haar wavelet. This method can reduce the amount of the stored data effectively and be applied to the design of discrete-time fractional order PID controllers. Finally, several numerical examples and simulation results are given to illustrate the validity of this discretization algorithm. 相似文献
993.
Siwaporn Saewan Poom Kumam 《Applied mathematics and computation》2011,218(7):3522-3538
We introduce a modified block hybrid projection algorithm for finding a common element of the set of common fixed points of an infinite family of closed and uniformly quasi-?-asymptotically nonexpansive mappings, the set of the variational inequality for an α-inverse-strongly monotone operator, the set of solutions of the mixed equilibrium problems. Then, we obtain strong convergence theorems for the sequences generated by this process in a 2-uniformly convex and uniformly smooth Banach space. Our results extend and improve ones from several earlier works. 相似文献
994.
In this paper we propose numerical treatment for singular integral equations. The methods are developed by means of the Sinc approximation with smoothing transformations. Such approximation is an effective technique against the singularities of the equations, and achieves exponential convergence. Therefore the methods improve conventional results where only polynomial convergence have been reported. The resulting algebraic system is solved by least squares approximation and leap frog algorithm. Estimation of errors of the approximate solution is presented. Some experimental tests are presented to show the efficient of the proposed methods. 相似文献
995.
Liliana Garrido Lopera Jorge Alberto Achcar 《Applied mathematics and computation》2011,218(7):3635-3648
In this paper, we introduce a Bayesian analysis for mixture of distributions belonging to the exponential family. As a special case we consider a mixture of normal exponential distributions including joint modeling of the mean and variance. We also consider joint modeling of the mean and variance heterogeneity. Markov Chain Monte Carlo (MCMC) methods are used to obtain the posterior summaries of interest. We also introduce and apply an EM algorithm, where the maximization is obtained applying the Fisher scoring algorithm. Finally, we also include analysis of real data sets to illustrate the proposed methodology. 相似文献
996.
Artificial bee colony algorithm (ABC) is a relatively new optimization technique which has been shown to be competitive to other population-based algorithms. However, there is still an insufficiency in ABC regarding its solution search equation, which is good at exploration but poor at exploitation. To address this concerning issue, we propose an improved ABC (IABC) by using a modified search strategy to generate a new food source in order that the exploration and exploitation can be well balanced and satisfactory optimization performances can be achieved. In addition, to enhance the global convergence, when producing the initial population, both opposition-based learning method and chaotic maps are employed. In this paper, the proposed algorithm is applied to control and synchronization of discrete chaotic systems which can be formulated as both multimodal numerical optimization problems with high dimension. Numerical simulation and comparisons with some typical existing algorithms demonstrate the effectiveness and robustness of the proposed approach. 相似文献
997.
Chi-Jen Lin 《Operations Research Letters》2011,39(1):67-73
This paper proposes iterative labeling algorithms to determine the Type II sensitivity ranges of the fractional assignment problem. Unlike the traditional sensitivity range which keeps the current optimal basis remaining optimal, the Type II sensitivity range is the range that keeps the current optimal assignment remaining optimal. Focusing only on the non-degenerate basic variables makes the Type II sensitivity range more practical. Three cases of perturbation, each with two kinds, are discussed. An example is presented to demonstrate the proposed algorithms. 相似文献
998.
We examine the model-building issue related to multi-objective estimation of distribution algorithms (MOEDAs) and show that some of their, as yet overlooked, characteristics render most current MOEDAs unviable when addressing optimization problems with many objectives. We propose a novel model-building growing neural gas (MB-GNG) network that is specially devised for properly dealing with that issue and therefore yields a better performance. Experiments are conducted in order to show from an empirical point of view the advantages of the new algorithm. 相似文献
999.
This paper deals with the problems of consistency and strong consistency of the maximum likelihood estimators of the mean and variance of the drift fractional Brownian motions observed at discrete time instants. Both the central limit theorem and the Berry-Ess′een bounds for these estimators are obtained by using the Stein’s method via Malliavin calculus. 相似文献
1000.
杨奇祥 《数学物理学报(B辑英文版)》2011,(4):1517-1534
If we use Littlewood-Paley decomposition, there is no pseudo-orthogonality for Ho¨rmander symbol operators OpS m 0 , 0 , which is different to the case S m ρ,δ (0 ≤δ < ρ≤ 1). In this paper, we use a special numerical algorithm based on wavelets to study the L p continuity of non infinite smooth operators OpS m 0 , 0 ; in fact, we apply first special wavelets to symbol to get special basic operators, then we regroup all the special basic operators at given scale and prove that such scale operator’s continuity decreases very fast, we sum such scale operators and a symbol operator can be approached by very good compact operators. By correlation of basic operators, we get very exact pseudo-orthogonality and also L 2 → L 2 continuity for scale operators. By considering the influence region of scale operator, we get H 1 (= F 0 , 2 1 ) → L 1 continuity and L ∞→ BMO continuity. By interpolation theorem, we get also L p (= F 0 , 2 p ) → L p continuity for 1 < p < ∞ . Our results are sharp for F 0 , 2 p → L p continuity when 1 ≤ p ≤ 2, that is to say, we find out the exact order of derivations for which the symbols can ensure the resulting operators to be bounded on these spaces. 相似文献