全文获取类型
收费全文 | 215篇 |
免费 | 96篇 |
国内免费 | 10篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 9篇 |
2020年 | 4篇 |
2019年 | 12篇 |
2018年 | 7篇 |
2017年 | 12篇 |
2016年 | 16篇 |
2015年 | 8篇 |
2014年 | 10篇 |
2013年 | 22篇 |
2012年 | 15篇 |
2011年 | 15篇 |
2010年 | 13篇 |
2009年 | 22篇 |
2008年 | 13篇 |
2007年 | 14篇 |
2006年 | 18篇 |
2005年 | 11篇 |
2004年 | 16篇 |
2003年 | 5篇 |
2002年 | 10篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 2篇 |
排序方式: 共有321条查询结果,搜索用时 15 毫秒
161.
以二维浅水波为例,详细探讨如何开发并行模式的切线性模式和伴随模式。切线性模式的并行机制和原始模式一致,而伴随模式不同。三个模式采用一致的数据剖分方法可提高并行效率。在集群并行计算机系统上采用一维数据剖分,切线性模式的通信量与原始模式相当,而计算量几乎是原始模式的2倍;伴随模式的通信量大约是原始模式的2倍,而计算量几乎是原始模式的3倍。在三个模式中,切线性模式的加速比最大。 相似文献
162.
为了提高大长径比发动机药柱结构完整性水平,基于三维黏弹性有限元法,计算某大长径比固体发动机在温度和内压荷载联合作用下的结构响应;研究伞盘结构及其位置对药柱最大Von Mises应变的影响规律;讨论当伞盘位于药柱中部时,伞盘最大Von Mises应变随伞盘宽度、深度以及顶部圆弧半径比的变化规律。结果表明,伞盘位于药柱中部时可以有效地降低大长径比药柱的最大Von Mises应变,增加伞盘宽度、深度或选取合适的半径比均可降低伞盘结构的最大Von Mises应变。所得结论可为固体发动机设计提供参考。 相似文献
163.
164.
165.
张连民 《中国人民武装警察部队学院学报》2001,17(3):25-26
通过对防火设备、灭火装备的费用估算,介绍如何利用数学建模的方式进行消防设备费用估算的具体方法,并对火灾过程中装备费用的精确估算方法进行了初步探讨. 相似文献
166.
边界附近的点对程序故障更加敏感.针对这一特征,提出了一种基于程序域边界分析的测试方法.从被测程序本身出发,进行定义域确定及子域划分,分析定义域边界和子域边界,并跟据其边界测试点产生测试用例,以检测域边界附近的处理.实验表明对定义域边界及其子域边界进行测试,可有效地提高故障覆盖率. 相似文献
167.
Various methods and criteria for comparing coherent systems are discussed. Theoretical results are derived for comparing systems of a given order when components are assumed to have independent and identically distributed lifetimes. All comparisons rely on the representation of a system's lifetime distribution as a function of the system's “signature,” that is, as a function of the vector p= (p1, … , pn), where pi is the probability that the system fails upon the occurrence of the ith component failure. Sufficient conditions are provided for the lifetime of one system to be larger than that of another system in three different senses: stochastic ordering, hazard rate ordering, and likelihood ratio ordering. Further, a new preservation theorem for hazard rate ordering is established. In the final section, the notion of system signature is used to examine a recently published conjecture regarding componentwise and systemwise redundancy. © 1999 John Wiley & Sons, Inc. Naval Research Logistics 46: 507–523, 1999 相似文献
168.
《防务技术》2019,15(6):844-852
To optimize the energy output and improve the energy utilization efficiency of an aluminized explosive, an explosion device was developed and used to investigate the detonation pressure and temperature of R1 (Al6) aluminum powder and the aluminum powder particle gradation of R2 (Al6+Al13), R3 (Al6+Al24) and R4 (Al6+Al flake) in a confined space. By using gas chromatography, quantitative analysis and calculations were carried out to analyze the gaseous detonation products. Finally, the reaction ratios of the aluminum powder and the explosion reaction equations were calculated. The results show that in a confined space, the quasi-static pressures and equilibrium temperature of the aluminum powder in air are higher than in vacuum. In vacuum, the quasi-static pressures and equilibrium temperatures of the samples in descending order are R1>R3>R4>R2 and R3>R4>R1>R2, respectively. In air, the quasi-static pressures and equilibrium temperatures of the samples in descending order are R1>R2>R4>R3 and R1>R4>R2>R3, respectively. R4 (Al6+Al flake) and R3 (Al6+Al24) have relatively higher temperatures after detonation, which shows that the particle gradation method can enhance the reaction energy output of aluminum during the initial reaction stage of the explosion and increase the reaction ratio by 10.6% and 8.0%, respectively. In air, the reaction ratio of Al6 aluminum powder can reach as high as 78.16%, and the reaction ratio is slightly reduced after particle gradation. Finally, the reaction equations of the explosives in vacuum and in air were calculated by quantitative analysis of the explosion products, which provides a powerful basis for the study of RDX-based explosive reactions. 相似文献
169.
Dimitri Percia David Marcus Matthias Keupp Ricardo Marino Patrick Hofstetter 《Defence and Peace Economics》2019,30(1):111-127
The Swiss Armed Forces are suffering from a structural deficit of militia officers despite good pay and a general supportive attitude in the population. Whereas, prior studies have focused on motivation to explain understaffing in armed forces, we offer an alternative approach based on opportunity cost. We model decision alternatives both within and outside a military organization, taking private sector employment as the reference point. We then monetize opportunity costs of leisure, fringe benefits, and private sector income not compensated. Our results suggest that in terms of opportunity cost, service as a militia officer is the least attractive option, an effect that we believe explains the persistent staff deficit. Implications of these findings for the literature and recruitment policy are discussed. 相似文献
170.
当前装备供应保障系统中维修器材存在短缺、积压以及配送系统效率低下等问题,亟须对生产、库存和配送作业环节进行集成优化。为客观反映各个决策环节,将该问题公式化为一个混合整数线性规划模型,针对该模型多变量、多约束的特点,提出了一个基于数学规划的两阶启发式算法对其进行求解。结合算例,检验模型的可行性,并选取求解器CPLEX和一个类似的迭代算法与该算法在求解质量和运算时间方面进行对比与分析。结果表明,提出的模型是合理可行的,该算法在求解不同规模实例时表现出优异的性能。 相似文献