全文获取类型
收费全文 | 2381篇 |
免费 | 71篇 |
国内免费 | 47篇 |
专业分类
化学 | 90篇 |
晶体学 | 1篇 |
力学 | 85篇 |
综合类 | 4篇 |
数学 | 2115篇 |
物理学 | 204篇 |
出版年
2024年 | 2篇 |
2023年 | 41篇 |
2022年 | 32篇 |
2021年 | 34篇 |
2020年 | 73篇 |
2019年 | 51篇 |
2018年 | 41篇 |
2017年 | 37篇 |
2016年 | 49篇 |
2015年 | 52篇 |
2014年 | 83篇 |
2013年 | 211篇 |
2012年 | 138篇 |
2011年 | 133篇 |
2010年 | 122篇 |
2009年 | 166篇 |
2008年 | 175篇 |
2007年 | 155篇 |
2006年 | 105篇 |
2005年 | 85篇 |
2004年 | 64篇 |
2003年 | 60篇 |
2002年 | 32篇 |
2001年 | 36篇 |
2000年 | 37篇 |
1999年 | 43篇 |
1998年 | 32篇 |
1997年 | 45篇 |
1996年 | 33篇 |
1995年 | 36篇 |
1994年 | 30篇 |
1993年 | 24篇 |
1992年 | 19篇 |
1991年 | 18篇 |
1990年 | 18篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 21篇 |
1985年 | 22篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1981年 | 14篇 |
1980年 | 19篇 |
1979年 | 15篇 |
1978年 | 14篇 |
1977年 | 14篇 |
1976年 | 6篇 |
1974年 | 2篇 |
排序方式: 共有2499条查询结果,搜索用时 109 毫秒
131.
We consider a two-station tandem queue with a buffer size of one at the first station and a finite buffer size at the second station. Silva et al. (2013) gave a criterion determining the optimal admission control policy for this model. In this paper, we improve the results of Silva et al. (2013) and also solve the problem conjectured by Silva et al. (2013). 相似文献
132.
We study the problem of optimal reinsurance as a means of risk management in the regulatory framework of Solvency II under Conditional Value-at-Risk and, as its natural extension, spectral risk measures. First, we show that stop-loss reinsurance is optimal under both Conditional Value-at-Risk and spectral risk measures. Spectral risk measures thus constitute a more general class of suitable regulatory risk measures than specific Conditional Value-at-Risk. At the same time, the established type of stop-loss reinsurance can be maintained as the optimal risk management strategy that minimizes regulatory capital. Second, we derive the optimal deductibles for stop-loss reinsurance. We show that under Conditional Value-at-Risk, the optimal deductible tends towards restrictive and counter-intuitive corner solutions or “plunging”, which is a serious objection against its use in regulatory risk management. By means of the broader class of spectral risk measures, we are able to overcome this shortcoming as optimal deductibles are now interior solutions. Especially, the recently discussed power spectral risk measures and the Wang risk measure are shown to avoid any plunging. They yield a one-to-one correspondence between the risk parameter and the optimal deductible and, thus, provide economically plausible risk management strategies. 相似文献
133.
134.
Linhe Zhu Xiaoyuan Huang Ying Liu Zhengdi Zhang 《Journal of Mathematical Analysis and Applications》2021,493(2):124539
In the new social media era, it is becoming increasingly important to explore the propagation rules for rumors in social networks. This article is concerned with investigating a diffusive susceptible-infected rumor propagation model with a nonlinear propagation function in a spatially heterogeneous environment. We establish the uniform persistence and analyze the asymptotic behavior of the rumor-spreading steady state for the spatially heterogeneous model when one of the diffusion coefficients tends to zero. Moreover, to better reflect the effect of a time delay on the process of rumor propagation, we establish a spatially homogeneous model with a time delay and prove the existence and local stability of the corresponding equilibrium point. Furthermore, the optimal control in the spatially homogeneous environment case is derived. Finally, several numerical simulations are performed to verify the theoretical results in both spatially heterogeneous and spatially homogeneous systems. 相似文献
135.
Xin-yu Song Lan-sun ChenDepartment of Mathematics. Xinyang Teachers College Henan ChinaInstitute of Mathematics Academy of Mathematics System Sciences Chinese Academy of Sciences Beijing China 《应用数学学报(英文版)》2002,18(3):423-430
The dynamics of a predator-prey system, where prey population has two stages, an immature stage and a mature stage with harvesting, the growth of predator population is of Lotka-Volterra nature, are modelled by a system of retarded functional differential equations. We obtain conditions for global asymptotic stability of three nonnegative equilibria and a threshold of harvesting for the mature prey population. The effect of delay on the population at positive equilibrium and the optimal harvesting of the mature prey population are also considered. 相似文献
136.
In this paper, we study an inverse problem of reconstructing two time independent coefficients in the reaction diffusion system from the final measurement. First the given problem is transformed into an optimization problem by using optimal control framework and the existence of the minimizer for the control functional is established. Then we prove the stability estimate for two coefficients with the upper bound given by some Sobolev norms of the final measurement. 相似文献
137.
We prove an existence theorem of Lagrange multipliers for an abstract control problem in Banach spaces. This theorem may be applied to obtain optimality conditions for control problems governed by partial differential equations in the presence of pointwise state constraints. 相似文献
138.
A question of flow around an obstacle leads to an optimal control problem. If an optimum path exists, then it is calculable from the Pontryagin principle. The optimum is verified to be reached, using a discretization of the problem. 相似文献
139.
《复变函数与椭圆型方程》2012,57(4):285-301
Let U be the open unit disc of the complex plane. We explicitly construct the best pointwise approximation for determining a function in the Hardy space H p (U) from measured data at a countable set of points in U whenever the data is exact. A regularization scheme is given to deal with the case of nonexact data. Moreover, optimal error estimates are also studied. 相似文献
140.
M. Rachkov L. Marques 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2013,19(2):115-124
Modelling of the motion of a helicopter with a suspended load is described. The mathematical model takes into account stochastic disturbances acting on the load suspension point. The proposed approach allows solution of the problem of optimal control with minimization of oscillation and control power expenditure. The evolution of the system solution with time is investigated for various disturbance intensities. Computer calculation results are presented as a function of the suspension length and the intensity of stochastic disturbances. 相似文献