全文获取类型
收费全文 | 591篇 |
免费 | 107篇 |
国内免费 | 44篇 |
专业分类
化学 | 189篇 |
晶体学 | 2篇 |
力学 | 55篇 |
综合类 | 8篇 |
数学 | 261篇 |
物理学 | 227篇 |
出版年
2024年 | 2篇 |
2023年 | 13篇 |
2022年 | 30篇 |
2021年 | 34篇 |
2020年 | 45篇 |
2019年 | 45篇 |
2018年 | 27篇 |
2017年 | 21篇 |
2016年 | 33篇 |
2015年 | 22篇 |
2014年 | 24篇 |
2013年 | 42篇 |
2012年 | 24篇 |
2011年 | 24篇 |
2010年 | 27篇 |
2009年 | 19篇 |
2008年 | 39篇 |
2007年 | 21篇 |
2006年 | 23篇 |
2005年 | 17篇 |
2004年 | 28篇 |
2003年 | 18篇 |
2002年 | 17篇 |
2001年 | 13篇 |
2000年 | 12篇 |
1999年 | 13篇 |
1998年 | 14篇 |
1997年 | 11篇 |
1996年 | 7篇 |
1995年 | 13篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 9篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有742条查询结果,搜索用时 31 毫秒
491.
In this paper, we propose a memory state feedback model predictive control (MPC) law for a discrete-time uncertain state delayed system with input constraints. The model uncertainty is assumed to be polytopic, and the delay is assumed to be unknown, but with a known upper bound. We derive a sufficient condition for cost monotonicity in terms of LMI, which can be easily solved by an efficient convex optimization algorithm. A delayed state dependent quadratic function with an estimated delay index is considered for incorporating MPC problem formulation. The MPC problem is formulated to minimize the upper bound of infinite horizon cost that satisfies the sufficient conditions. Therefore, a less conservative sufficient conditions in terms of linear matrix inequality (LMI) can be derived to design a more robust MPC algorithm. A numerical example is included to illustrate the effectiveness of the proposed method. 相似文献
492.
本文通过积分检验, 刻画了不同分布的$\varphi$-混合序列后置和的极限结果,并由此导出了它们的Chover型重对数律,推广和改进了已有的结果. 相似文献
493.
本文讨论了同分布的 -混合序列其共同分布属于稳定分布(非高斯情形)吸引场部分和的Chover型重对数律.特别地当分布函数属于稳分布的正则吸引场时,得到了部分和及后置和更精细的结果,即积分检验的结果,由此立即可推出相应的Chover型重对数律. 相似文献
494.
HaoZHAO GuiZhenLIU XiaoXiaYAN 《数学学报(英文版)》2005,21(2):413-422
Let G be a graph with vertex set V(G) and edge set E(G) and let g and f be two integervalued functions defined on V(G) such that 2k - 2 ≤g(x)≤f(x) for all x∈V(G). Let H be a subgraph of G with mk edges. In this paper, it is proved that every (mg m-1,mf-m 1)-graph G has (g, f)-factorizations randomly k-orthogonal to H under some special conditions. 相似文献
495.
关于B值随机元随机指标和的矩的讨论 总被引:1,自引:0,他引:1
在本文中,我们研究停止时间N的矩、B值随机元X_n的矩以及{X_n,n≥1}的随机指标和S_N的矩之间的关系。特别,在赋予Banach空间以某些特定的几何性质,例如假设B为p-阶光滑空间、q-凸空间及Hilbert空间的情形下,讨论了上述各种矩之间的关系。 相似文献
496.
Various first-order and second-order sufficient conditions of optimality for nonlinear optimal control problems with delayed argument are formulated. The functions involved are not required to be convex. Second-order sufficient conditions are shown to be related to the existence of solutions of a Riccati-type matrix differential inequality. Their relation with the second variation is discussed.The authors are indebted to an anonymous referee for valuable suggestions that lead to various improvements in the paper. 相似文献
497.
S. A. Bagnich 《Journal of Applied Spectroscopy》1998,65(5):687-700
Results of investigations of all types of long-lived luminescence of organic molecules in the gas phase and condensed media
are presented. Methods for identification and separation of contributions of phosphorescence and thermally activated fluorescence
in long-lived luminescence of organic-molecule vapors are proposed. Energy transfer and migration processes in the case of
the inductive-resonant mechanism of intermolecular interaction leading to the appearance of sensitized phosphorescence and
annihilation-induced delayed fluorescence are considered. Experimental results on energy migration obtained for solid solutions
of organic compounds are analyzed within the framework of the concepts of percolation theory with account for the microscopic
inhomogeneity of the systems under investigation and the fractal properties of the clusters of activator molecules.
Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, F. Skorina Ave., 70, Minsk, 220072, Belarus.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 5, pp. 662–674, September–October, 1998. 相似文献
498.
田德生 《数学的实践与认识》2008,38(11):163-167
应用锥不动点定理研究了一类时滞微分方程周期解的存在性问题,建立了该系统具有至少一个正周期解的充分条件. 相似文献
499.
In this paper a system of three delay differential equations representing a Hopfield type general model for three neurons with two-way (bidirectional) time delayed connections between the neurons and time delayed self-connection from each neuron to itself is studied. Delay independent and delay dependent sufficient conditions for linear stability, instability and the occurrence of a Hopf bifurcation about the trivial equilibrium are addressed. The partition of the resulting parametric space into regions of stability, instability, and Hopf bifurcation in the absence of self-connection is realized. To extend the local Hopf branches for large delay values a particular bidirectional delayed tri-neuron model without self-connection is investigated. Sufficient conditions for global existence of multiple non-constant periodic solutions are obtained for such a model using the global Hopf-bifurcation theorem for functional differential equations due to J. Wu and the Bendixson criterion for higher dimensional ordinary differential equations due to Li and Muldowney, and following the approach developed by Wei and Li. 相似文献
500.
本文报道了在双极性扩散系数较大情况下,用非相干光时间延迟四波混频测量失相时间和光栅衰减时间的理论,并对计算结果进行了讨论。 相似文献