全文获取类型
收费全文 | 10161篇 |
免费 | 1599篇 |
国内免费 | 463篇 |
专业分类
化学 | 1878篇 |
晶体学 | 44篇 |
力学 | 1705篇 |
综合类 | 194篇 |
数学 | 5127篇 |
物理学 | 3275篇 |
出版年
2024年 | 16篇 |
2023年 | 142篇 |
2022年 | 237篇 |
2021年 | 279篇 |
2020年 | 240篇 |
2019年 | 231篇 |
2018年 | 232篇 |
2017年 | 425篇 |
2016年 | 488篇 |
2015年 | 442篇 |
2014年 | 547篇 |
2013年 | 787篇 |
2012年 | 561篇 |
2011年 | 559篇 |
2010年 | 518篇 |
2009年 | 621篇 |
2008年 | 647篇 |
2007年 | 647篇 |
2006年 | 492篇 |
2005年 | 383篇 |
2004年 | 393篇 |
2003年 | 418篇 |
2002年 | 353篇 |
2001年 | 261篇 |
2000年 | 283篇 |
1999年 | 269篇 |
1998年 | 229篇 |
1997年 | 170篇 |
1996年 | 168篇 |
1995年 | 150篇 |
1994年 | 119篇 |
1993年 | 92篇 |
1992年 | 72篇 |
1991年 | 78篇 |
1990年 | 66篇 |
1989年 | 52篇 |
1988年 | 59篇 |
1987年 | 48篇 |
1986年 | 38篇 |
1985年 | 63篇 |
1984年 | 34篇 |
1983年 | 27篇 |
1982年 | 33篇 |
1981年 | 26篇 |
1980年 | 46篇 |
1979年 | 44篇 |
1978年 | 26篇 |
1977年 | 36篇 |
1976年 | 36篇 |
1974年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
851.
In this paper an important problem in chaos control theory concerningthe possibility of generating a new stable periodic solutionby a small feedback control law for a dynamical system is addressed.It is proved that a solution with an initial point being somekind of non-wandering property can become a new asymptoticallystable solution by a small feedback control law. This showsthat the popular opinion that a small control law is not ableto create a new periodic point is untrue, and suggests a newapproach to controlling chaos. 相似文献
852.
This paper is concerned with the simultaneous maneuver and vibration control of a flexible spacecraft. The problem is solved by means of a perturbation approach whereby the slewing of the spacecraft regarded as rigid represents the zero-order problem and the control of vibration, as well as of perturbations from the rigid-body maneuver, represents the first-order problem. The zero-order control is to be carried out in minimum time, which implies bang-bang control. On the other hand, the first-order control is a time-dependent linear quadratic regulator including integral feedback and prescribed convergence rate.This research was sponsored by USAF/ASD and AFOSR Research Grant F33615-86-C-3233 monitored by Drs. A. K. Amos and V. B. Venkayya, whose support is greatly appreciated. 相似文献
853.
首先给出了牲畜(家禽)的传染病(禽流感、口蹄疫)的控制策略模型,控制措施包括两个方面:一,除掉那些已经被确诊的被传染的种群.二,对那些认为处于疫区的,可能被传染的种群采取预控制(隔离、提前宰杀).因为预控制并不能辨别出哪些群体是真正的接触者,所以这种控制措施将导致把感染者和健康的一并除掉,这就产生了一个矛盾:控制强度的加大能够减少疾病的传播率,但同时增加了无辜者被宰杀的群体的数量,并且证明了一个优化的控制策略,它能够减少由于过多捕杀带来的损失. 相似文献
854.
855.
856.
G. Ortner M. Bayer A. Kress A. Forchel Y. B. Lyanda-Geller T. L. Reinecke 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):171
Semiconductor nanostructures have attracted considerable interest during the recent years in view of the potential application in quantum information processing. In particular, quantum dots have been suggested to fulfill an essential requirement for quantum computation: controllable interaction that couples two quantum dot qubits. Previous experiments on two vertically aligned quantum dots have demonstrated the formation of coupled exciton states. We show that this coupling between two In0.60Ga0.40As/GaAs quantum dots can be tuned by an electric field applied along the molecule axis. This controllable coupling in such a relatively simple configuration could be implemented in a solid-state-based quantum device. 相似文献
857.
J. H. Park 《Journal of Optimization Theory and Applications》2005,124(2):491-502
In this article, the guaranteed cost control problem for a class of neutral delay systems is investigated. A linear--quadratic cost function is considered as a performance measure for the closed-loop system. Based on the Lyapunov method, delay-dependent criteria, which are expressed in terms of matrix inequalities, are proposed to guarantee the asymptotic stability of the system. The matrix inequalities can be solved easily by various efficient optimization algorithms. 相似文献
858.
859.
860.
Fritz Colonius Wolfgang Kliemann 《Transactions of the American Mathematical Society》2008,360(11):5667-5682
This paper proposes a topological framework for the analysis of the time shift on behaviors. It is shown that controllability is not a property of the time shift, while chain controllability is. This also leads to a global decomposition of behaviors.