全文获取类型
收费全文 | 268篇 |
免费 | 125篇 |
国内免费 | 30篇 |
专业分类
423篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 2篇 |
2020年 | 14篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 18篇 |
2016年 | 21篇 |
2015年 | 16篇 |
2014年 | 33篇 |
2013年 | 25篇 |
2012年 | 31篇 |
2011年 | 23篇 |
2010年 | 14篇 |
2009年 | 23篇 |
2008年 | 20篇 |
2007年 | 30篇 |
2006年 | 19篇 |
2005年 | 17篇 |
2004年 | 18篇 |
2003年 | 14篇 |
2002年 | 11篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 3篇 |
排序方式: 共有423条查询结果,搜索用时 0 毫秒
11.
12.
舰船航向保持的变结构控制及仿真 总被引:4,自引:1,他引:4
运用变结构控制理论和计算机仿真技术研究舰船航向保持过程的变结构控制问题,针对舰船定向航行要求航向准、舵角小的控制特点,采用二次型最优控制方法设计滑动模态超平面,设计了满足滑模超平面到达条件的指数趋近律,导出了对应的控制律。同时,为进行比较研究,设计了PID控制器并整定了相关参数。理论分析与仿真研究表明:对于舰船定向航行,变结构控制方案正确可行,控制效果优于PID控制方案。 相似文献
13.
14.
Ji Hwan Cha 《海军后勤学研究》2006,53(3):226-234
Burn‐in procedure is a manufacturing technique that is intended to eliminate early failures of system or product. Burning‐in a component or system means to subject it to a period of use prior to being used in field. Generally, burn‐in is considered expensive and so the length of burn‐in is typically limited. Thus, burn‐in is most often accomplished in an accelerated environment in order to shorten the burn‐in process. A new failure rate model for an accelerated burn‐in procedure, which incorporates the accelerated ageing process induced by the accelerated environmental stress, is proposed. Under a more general assumption on the shape of failure rate function of products, which includes the traditional bathtub‐shaped failure rate function as a special case, upper bounds for optimal burn‐in time will be derived. A numerical example will also be given for illustration. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006 相似文献
15.
16.
17.
A learning tabu search for a truck allocation problem with linear and nonlinear cost components 下载免费PDF全文
The two‐level problem studied in this article consists of optimizing the refueling costs of a fleet of locomotives over a railway network. The goal consists of determining: (1) the number of refueling trucks contracted for each yard (truck assignment problem denoted TAP) and (2) the refueling plan of each locomotive (fuel distribution problem denoted FDP). As the FDP can be solved efficiently with existing methods, the focus is put on the TAP only. In a first version of the problem (denoted (P1)), various linear costs (e.g., fuel, fixed cost associated with each refueling, weekly operating costs of trucks) have to be minimized while satisfying a set of constraints (e.g., limited capacities of the locomotives and the trucks). In contrast with the existing literature on this problem, two types of nonlinear cost components will also be considered, based on the following ideas: (1) if several trucks from the same fuel supplier are contracted for the same yard, the supplier is likely to propose discounted prices for that yard (Problem (P2)); (2) if a train stops too often on its route, a penalty is incurred, which represents the dissatisfaction of the clients (Problem (P3)). Even if exact methods based on a mixed integer linear program formulation are available for (P1), they are not appropriate anymore to tackle (P2) and (P3). Various methods are proposed for the TAP: a descent local search, a tabu search, and a learning tabu search (LTS). The latter is a new type of local search algorithm. It involves a learning process relying on a trail system, and it can be applied to any combinatorial optimization problem. Results are reported and discussed for a large set of instances (for (P1), (P2), and (P3)), and show the good performance of LTS. © 2014 Wiley Periodicals, Inc. 62:32–45, 2015 相似文献
18.
We consider a loss system with a fixed budget for servers. The system owner's problem is choosing the price, and selecting the number and quality of the servers, in order to maximize profits, subject to a budget constraint. We solve the problem with identical and different service rates as well as with preemptive and nonpreemptive policies. In addition, when the policy is preemptive, we prove the following conservation law: the distribution of the total service time for a customer entering the slowest server is hyperexponential with expectation equal to the average service rate independent of the allocation of the capacity. © 2015 Wiley Periodicals, Inc. Naval Research Logistics 62: 81–97, 2015 相似文献
19.
广泛工作在ISM(Industrial,Scientific and Medical)频段的无线传感器网络面临严重的频谱稀缺问题。在无线通信中,动态频谱分配被认为是提高频谱效能的重要途径。针对典型集中式管理的认知无线传感器网络设计了基于图着色结合负载强度的高效频谱分配算法。首先在协议干扰模型下确保频谱资源在空间上充分利用,随后综合考虑节点负载强度与公平性建立优化模型并按照乘子法加拟牛顿法框架求解最优值。仿真实验表明算法与固定频谱分配方式和传统自适应频谱分配算法相比,在系统吞吐量和节点缓冲区队列长度两个关键性能指标上具有显著优势。 相似文献
20.
Eyal Pecht 《Defence and Peace Economics》2017,28(3):367-399
This study develops a dynamic model that integrates military intelligence into the defense capability of the country and the optimal allocation of its government budget. We assert that the effectiveness of the country’s military intelligence is contingent on the quality of its human capital, which, in turn, implies a long-term positive relationship between the government’s various civilian expenditures and its capacity to achieve a cost-effective intelligence and, hence, military capability. This relationship is developed within a multiple-period arms race model between two rivals. Using this model and stylized data for the Israeli–Syrian arms race, we show that an appropriate budget shift from defense to civilian expenditures during the initial periods of the planning horizon will gradually (over a decade, say) increase the quality of human capital in the country and, thus, the effectiveness of its intelligence, which, in turn, will increase the country’s future security and welfare. 相似文献