全文获取类型
收费全文 | 11116篇 |
免费 | 1938篇 |
国内免费 | 524篇 |
专业分类
化学 | 1996篇 |
晶体学 | 47篇 |
力学 | 1811篇 |
综合类 | 212篇 |
数学 | 5327篇 |
物理学 | 4185篇 |
出版年
2024年 | 27篇 |
2023年 | 191篇 |
2022年 | 292篇 |
2021年 | 321篇 |
2020年 | 270篇 |
2019年 | 259篇 |
2018年 | 284篇 |
2017年 | 485篇 |
2016年 | 536篇 |
2015年 | 493篇 |
2014年 | 613篇 |
2013年 | 851篇 |
2012年 | 604篇 |
2011年 | 627篇 |
2010年 | 571篇 |
2009年 | 660篇 |
2008年 | 702篇 |
2007年 | 705篇 |
2006年 | 563篇 |
2005年 | 427篇 |
2004年 | 442篇 |
2003年 | 461篇 |
2002年 | 377篇 |
2001年 | 299篇 |
2000年 | 313篇 |
1999年 | 299篇 |
1998年 | 244篇 |
1997年 | 192篇 |
1996年 | 183篇 |
1995年 | 167篇 |
1994年 | 136篇 |
1993年 | 101篇 |
1992年 | 80篇 |
1991年 | 88篇 |
1990年 | 72篇 |
1989年 | 54篇 |
1988年 | 69篇 |
1987年 | 52篇 |
1986年 | 40篇 |
1985年 | 64篇 |
1984年 | 39篇 |
1983年 | 29篇 |
1982年 | 34篇 |
1981年 | 27篇 |
1980年 | 47篇 |
1979年 | 46篇 |
1978年 | 26篇 |
1977年 | 36篇 |
1976年 | 37篇 |
1974年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
Differential game formulations provide an adequate basis for a guidance law synthesis against highly maneuvering targets. This paper deals with a guidance law based on a linear-quadratic differential game formulation. This guidance law has many attractive properties: it is continuous, linear with respect to the state variables, and its gain coefficients can be precalculated offline. Nevertheless, due to the lack of hard control constraints in the formulation, the magnitude of the control can exceed the admissible level imposed by the nature of the problem. In this paper, the upper bound of the interceptor control is obtained depending on the system parameters and the penalty coefficients of the game performance index. It is shown that the interceptor can guarantee an arbitrarily small miss distance without exceeding the control constraints if it has sufficient maneuverability and if the penalty coefficients are chosen properly. By manipulating the penalty coefficients, it is possible to reduce significantly the maneuverability requirements compared to the case of zero interceptor penalty coefficient. 相似文献
42.
The control of piecewise-deterministic processes is studied where only local boundedness of the data is assumed. Moreover the discount rate may be zero. The value function is shown to be solution to the Bellman equation in a weak sense; however the solution concept is strong enough to generate optimal policies. Continuity and compactness conditions are given for the existence of nonrelaxed optimal feedback controls. 相似文献
43.
Toshihiro Kobayashi 《Mathematical Methods in the Applied Sciences》2004,27(1):79-89
This paper is concerned with global stabilization of an undamped non‐linear string in the case where any velocity feedback is not available. The linearized system has an infinite number of poles and zeros on the imaginary axis. In the case where any velocity feedback is not available, a parallel compensator is effective. The stabilizer is constructed for the augmented system which consists of the controlled system and a parallel compensator. It is proved that the string can be stabilized by linear boundary control. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
44.
Mari Grobbelaar‐Van Dalsen 《Mathematical Methods in the Applied Sciences》2004,27(11):1301-1315
This paper is concerned with well‐posedness results for a mathematical model for the transversal vibrations of a two‐dimensional hybrid elastic structure consisting of a rectangular Reissner–Mindlin plate with a Timoshenko beam attached to its free edge. The model incorporates linear dynamic feedback controls along the interface between the plate and the beam. Classical semigroup methods are employed to show the unique solvability of the coupled initial‐boundary‐value problem. We also show that the energy associated with the system exhibits the property of strong stability. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
45.
Larbi Berrahmoune 《Mathematical Methods in the Applied Sciences》2004,27(12):1385-1398
We consider an initial and boundary value problem for a homogenous string subject to an internal pointwise control. The solution resulting from a non‐linear feedback is studied. We give various explicit decay estimates depending on the control position and the feedback non‐linearity. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
46.
The paper discusses the relationship between weights and control vertices of two rational NURBS curves of degree two or three with all weights larger than zero when they represent the same curve parametrically and geometrically, and gives sufficient and necessary conditions for coincidence of two rational NURBS curves in non-degeneracy case. 相似文献
47.
48.
49.
汪更生 《数学物理学报(B辑英文版)》2005,25(1):7-22
This paper deals with maximum principle for some optimal control problem governed by some elliptic variational inequalities. Some state constraints are discussed. The basic techniques used here are based on those in [1] and a new penalty functional defined in this paper. 相似文献
50.