全文获取类型
收费全文 | 2310篇 |
免费 | 224篇 |
国内免费 | 181篇 |
专业分类
化学 | 775篇 |
晶体学 | 10篇 |
力学 | 393篇 |
综合类 | 43篇 |
数学 | 815篇 |
物理学 | 679篇 |
出版年
2024年 | 5篇 |
2023年 | 15篇 |
2022年 | 27篇 |
2021年 | 61篇 |
2020年 | 50篇 |
2019年 | 66篇 |
2018年 | 53篇 |
2017年 | 106篇 |
2016年 | 94篇 |
2015年 | 68篇 |
2014年 | 129篇 |
2013年 | 182篇 |
2012年 | 111篇 |
2011年 | 148篇 |
2010年 | 103篇 |
2009年 | 135篇 |
2008年 | 172篇 |
2007年 | 159篇 |
2006年 | 137篇 |
2005年 | 105篇 |
2004年 | 107篇 |
2003年 | 81篇 |
2002年 | 82篇 |
2001年 | 65篇 |
2000年 | 53篇 |
1999年 | 46篇 |
1998年 | 44篇 |
1997年 | 45篇 |
1996年 | 36篇 |
1995年 | 28篇 |
1994年 | 24篇 |
1993年 | 21篇 |
1992年 | 24篇 |
1991年 | 20篇 |
1990年 | 16篇 |
1989年 | 12篇 |
1988年 | 17篇 |
1987年 | 14篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1974年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有2715条查询结果,搜索用时 31 毫秒
21.
22.
Decentralized iterative learning control for a class of large scale interconnected dynamical systems
Hansheng Wu 《Journal of Mathematical Analysis and Applications》2007,327(1):233-245
The problem of decentralized iterative learning control for a class of large scale interconnected dynamical systems is considered. In this paper, it is assumed that the considered large scale dynamical systems are linear time-varying, and the interconnections between each subsystem are unknown. For such a class of uncertain large scale interconnected dynamical systems, a method is presented whereby a class of decentralized local iterative learning control schemes is constructed. It is also shown that under some given conditions, the constructed decentralized local iterative learning controllers can guarantee the asymptotic convergence of the local output error between the given desired local output and the actual local output of each subsystem through the iterative learning process. Finally, as a numerical example, the system coupled by two inverted pendulums is given to illustrate the application of the proposed decentralized iterative learning control schemes. 相似文献
23.
John M. Davis Ian A. Gravagne 《Journal of Mathematical Analysis and Applications》2007,332(2):1291-1307
In this work, we reexamine the time scale Laplace transform as defined by Bohner and Peterson [M. Bohner, A. Peterson, Dynamic Equations on Time Scales: An Introduction with Applications, Birkhäuser, Boston, 2001; M. Bohner, A. Peterson, Laplace transform and Z-transform: Unification and extension, Methods Appl. Anal. 9 (1) (2002) 155-162]. In particular, we give conditions on the class of functions which have a transform, develop an inversion formula for the transform, and further, we provide a convolution for the transform. The notion of convolution leads to considering its algebraic structure—in particular the existence of an identity element—motivating the development of the Dirac delta functional on time scales. Applications and examples of these concepts are given. 相似文献
24.
The article is concerned with oscillation of nonautonomous neutral dynamic delay equations on time scales. Sufficient conditions are established for the existence of bounded positive solutions and for oscillation of all solutions of this equation. Some results extend known results for difference equations when the time scale is the set Z of positive integers and for differential equations when the time scale is the set R of real numbers. 相似文献
25.
Mihai V. Putz 《International journal of quantum chemistry》2006,106(2):361-389
A unified Mulliken valence with Parr ground‐state electronegativity picture is presented. It provides a useful analytical tool on which the absolute hardness as well ionization potential and electron affinity functionals are based. For all these chemical reactivity indices, systematic approximate density functionals are formulated within density functional softness theory and are applied to atomic systems. For the absolute hardness, a special relationship with the new electronegativity ansatz and a particular atomic trend paralleling the absolute electron affinity are established that should complement and augment the earlier finite‐difference energetic approach. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 相似文献
26.
基于尺度质心统计的纹理分析 总被引:1,自引:0,他引:1
结合目前纹理分析的三类算法,提出了尺度质心统计的分析算法。该算法以具有多分辨率特性的小波包为基础,结合结构法的纹理元分析方式,采用区域质心完成局部特征提取,最后使用投影法进行整体的特征提取。实验证明,尺度质心统计取得了令人满意的纹理分析效果。 相似文献
27.
28.
ABSTRACT. Limiting adverse consequences of fishing on essential fish habitat has emerged as a key fishery management objective. The conventional approach to providing habitat protection is to create MPAs or marine reserves that prohibit all or certain types of fishing in specific areas. However, there may be more cost‐effective and flexible ways to provide habitat protection. We propose an individual habitat quota (IHQ) system for habitat conservation that would utilize economic incentives to achieve habitat conservation goals cost‐effectively. Individual quotas of habitat impact units (HIU) would be distributed to fishers with an aggregate quota set to maintain a target habitat “stock.” HIU use would be based on a proxy for marginal habitat damage. We use a dynamic, explicitly spatial fishery and habitat simulation model to explore how such a system might work. We examine how outcomes are affected by spatial heterogeneity in the fishery and the scale of habitat regulation. We find that the IHQ system is a highly cost‐effective means of ensuring a given level of habitat protection, but that spatial heterogeneity and the scale of regulation can have significant effects on the distribution of habitat protection. 相似文献
29.
本文采用文[1,2]中提出的平衡结构法研究子系统s≥3的非线性大系统在近平衡区内的稳定性;得到了判别这类大系统稳定性的两个一般性准则. 相似文献
30.