全文获取类型
收费全文 | 238篇 |
免费 | 46篇 |
国内免费 | 16篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 10篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 8篇 |
2016年 | 5篇 |
2015年 | 8篇 |
2014年 | 20篇 |
2013年 | 21篇 |
2012年 | 12篇 |
2011年 | 11篇 |
2010年 | 15篇 |
2009年 | 18篇 |
2008年 | 16篇 |
2007年 | 25篇 |
2006年 | 12篇 |
2005年 | 9篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 11篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1982年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有300条查询结果,搜索用时 15 毫秒
91.
92.
针对某型航空发动机燃-滑油附件后盖同部位成批次出现裂纹的问题,提出了裂纹故障引导转移的避障策略。通过研究裂纹产生的主要原因,分析后盖不同部位所产生的裂纹可能对航空发动机造成的危害程度,调整改变原支撑结构,在后盖非关键部位形成新的应力集中点,降低关键部位应力集中区的应力幅值,迫使故障从不可修复的关键部位转移到可修复的非关键部位。经计算机仿真,确定了裂纹引导缺口的最佳参数;同时,仿真结果表明,裂纹故障引导转移策略合理可行。 相似文献
93.
94.
95.
进攻是最好的防守。针对水面舰艇攻势防御问题,对水面舰艇攻势防御的概念及使用前提进行了讨论,通过与守势防御的比较,从理论上对攻势防御的优势进行了论证。最后,根据论证结果、数据仿真及作战实际,给出了攻势防御的使用原则。 相似文献
96.
Pulse Doppler (PD) fuze is widely used in current battlefield. However, with the threat of repeater jamming, especially digital radio frequency memory technology, the deficiency in the anti-repeater jamming of a traditional PD fuze increasingly emerges. Therefore, a repeater jamming suppression method for a PD fuze based on identity (ID) recognition and chaotic encryption is proposed. Every fuze has its own ID which is encrypted with different chaotic binary sequences in every pulse period of the transmitted signal. The thumbtack-shaped ambiguity function shows a good resolution and distance cut-off characteristic. The ability of anti-repeater jamming is emphatically analyzed, and the results at different signal-to-noise ratio (SNR) show a strong anti-repeater jamming ability and range resolution that the proposed method possesses. Furthermore, the anti-repeater jamming ability is influenced by processing gain, bit error rate (BER) and correlation function. The simulation result validates the theo-retical analysis, it shows the proposed method can significantly improve the anti-repeater jamming ability of a PD fuze. 相似文献
97.
In this paper we consider the problem of scheduling a set of jobs on a single machine on which a rate‐modifying activity may be performed. The rate‐modifying activity is an activity that changes the production rate of the machine. So the processing time of a job is a variable, which depends on whether it is scheduled before or after the rate‐modifying activity. We assume that the rate‐modifying activity can take place only at certain predetermined time points, which is a constrained case of a similar problem discussed in the literature. The decisions under consideration are whether and when to schedule the rate‐modifying activity, and how to sequence the jobs in order to minimize some objectives. We study the problems of minimizing makespan and total completion time. We first analyze the computational complexity of both problems for most of the possible versions. The analysis shows that the problems are NP‐hard even for some special cases. Furthermore, for the NP‐hard cases of the makespan problem, we present a pseudo‐polynomial time optimal algorithm and a fully polynomial time approximation scheme. For the total completion time problem, we provide a pseudo‐polynomial time optimal algorithm for the case with agreeable modifying rates. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005 相似文献
98.
Scheduling a set of n jobs on a single machine so as to minimize the completion time variance is a well‐known NP‐hard problem. In this paper, we propose a sequence, which can be constructed in O(n log n) time, as a solution for the problem. Our primary concern is to establish the asymptotical optimality of the sequence within the framework of probabilistic analysis. Our main result is that, when the processing times are randomly and independently drawn from the same uniform distribution, the sequence is asymptotically optimal in the sense that its relative error converges to zero in probability as n increases. Other theoretical results are also derived, including: (i) When the processing times follow a symmetric structure, the problem has 2⌊(n−1)/2⌋ optimal sequences, which include our proposed sequence and other heuristic sequences suggested in the literature; and (ii) when these 2⌊(n−1)/2⌋ sequences are used as approximate solutions for a general problem, our proposed sequence yields the best approximation (in an average sense) while another sequence, which is commonly believed to be a good approximation in the literature, is interestingly the worst. © 1999 John Wiley & Sons, Inc. Naval Research Logistics 46: 373–398, 1999 相似文献
99.
武器装备维修是武器装备维修保障的重要内容,加强装备维修绩效评价,建立科学规范的绩效评价指标体系,对深入推进装备维修工作健康发展将发挥积极作用。以平衡计分卡为研究手段,运用"5M1E"分析法,从一个内核和四个维度出发,分析武器装备维修绩效评价的影响因素,据此建立评价指标体系,并应用于装备维修管理实践,为有效提高装备维修保障效益提供有益借鉴。 相似文献
100.
大数据技术在决策领域的不断应用,将给装备保障决策方式带来重大变革。本文研究基于大数据的战区联合作战装备保障决策问题,提升信息化条件下装备保障准确、高效的决策方式等方面发挥重大作用。阐述了大数据的基本内涵,在决策领域的应用价值。通过系统推理的方法对战区联合作战装备保障决策的分析,提出基于大数据的战区联合作战装备保障决策基本构想,画出科学决策过程示意图,构建大数据战区联合作战装备保障辅助决策系统。结合研究大数据在战区联合作战装备保障决策领域的现实情况,提出相对应的措施建议。 相似文献