全文获取类型
收费全文 | 1188篇 |
免费 | 503篇 |
国内免费 | 121篇 |
专业分类
1812篇 |
出版年
2024年 | 6篇 |
2023年 | 12篇 |
2022年 | 17篇 |
2021年 | 24篇 |
2020年 | 23篇 |
2019年 | 27篇 |
2018年 | 30篇 |
2017年 | 54篇 |
2016年 | 84篇 |
2015年 | 75篇 |
2014年 | 98篇 |
2013年 | 75篇 |
2012年 | 93篇 |
2011年 | 89篇 |
2010年 | 75篇 |
2009年 | 114篇 |
2008年 | 80篇 |
2007年 | 92篇 |
2006年 | 103篇 |
2005年 | 80篇 |
2004年 | 83篇 |
2003年 | 55篇 |
2002年 | 57篇 |
2001年 | 56篇 |
2000年 | 42篇 |
1999年 | 42篇 |
1998年 | 36篇 |
1997年 | 37篇 |
1996年 | 29篇 |
1995年 | 12篇 |
1994年 | 21篇 |
1993年 | 20篇 |
1992年 | 22篇 |
1991年 | 16篇 |
1990年 | 20篇 |
1989年 | 10篇 |
1988年 | 3篇 |
排序方式: 共有1812条查询结果,搜索用时 15 毫秒
821.
We present a stochastic programming approach to capacity planning under demand uncertainty in semiconductor manufacturing. Given multiple demand scenarios together with associated probabilities, our aim is to identify a set of tools that is a good compromise for all these scenarios. More precisely, we formulate a mixed‐integer program in which expected value of the unmet demand is minimized subject to capacity and budget constraints. This is a difficult two‐stage stochastic mixed‐integer program which cannot be solved to optimality in a reasonable amount of time. We instead propose a heuristic that can produce near‐optimal solutions. Our heuristic strengthens the linear programming relaxation of the formulation with cutting planes and performs limited enumeration. Analyses of the results in some real‐life situations are also presented. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005. 相似文献
822.
823.
Most modern processes involve multiple quality characteristics that are all measured on attribute levels, and their overall quality is determined by these characteristics simultaneously. The characteristic factors usually correlate with each other, making multivariate categorical control techniques a must. We study Phase I analysis of multivariate categorical processes (MCPs) to identify the presence of change‐points in the reference dataset. A directional change‐point detection method based on log‐linear models is proposed. The method exploits directional shift information and integrates MCPs into the unified framework of multivariate binomial and multivariate multinomial distributions. A diagnostic scheme for identifying the change‐point location and the shift direction is also suggested. Numerical simulations are conducted to demonstrate the detection effectiveness and the diagnostic accuracy.© 2013 Wiley Periodicals, Inc. Naval Research Logistics, 2013 相似文献
824.
Thomas-Durell Young 《战略研究杂志》2013,36(7):1031-1057
By any objective measure, defense institutions in Central and Eastern Europe have all but universally been incapable of producing viable defense plans that are based on objective costing and operational planning data. This situation exists in spite the provision of considerable Western advice and assistance, let alone reporting to and receiving assessments by NATO’s International Staff under Partnership for Peace, as well as via the integrated defense planning and reporting systems. An explanation for this systematic failure across European post-Communist defense institutions can be found in the continued slow development of an over-arching policy framework which directs and approves all activities of the armed forces, as well as the de-centralization of financial decision-making down to capability providers. The essay ends with an examination of the adverse effects of the early introduction of planning programming, budgeting system (PPBS), have had on the development of effective policy and planning capabilities within these defense institutions. 相似文献
825.
《防务技术》2019,15(6):829-836
The depth of penetration (DOP) method is a well-known ballistic test method for characterisation and ranking of ceramic armour materials. The ceramic tile is bonded to a backing material of semi-infinite thickness, and the penetration depth of the projectile gives a measure of the performance of the ceramic. There is, however, an inherent variability in the results from this test method. In this work, the accuracy and the variability of the DOP method has been investigated in a round robin exercise. Six ballistic test centres took part in the exercise. A test protocol was developed, in which the threat type (projectile and impact conditions) and a procedure on how to prepare the targets were specified. The targets consisted of alumina tiles of two different thicknesses that were bonded to polycarbonate backing cubes. Two different 7.62 mm armour piercing projectiles were employed; one with a hard steel core and one with a tungsten carbide core. The projectiles and the other materials all came from single material batches in order to avoid batch-to-batch variations in material properties. These materials were distributed between the ballistic test centres. The test results of the different ballistic test facilities were collected and compared. There was not a lot of variation between the average DOP values obtained at each laboratory, but the variation in penetration depth between shots was high. The consequence of this variation may be less confidence in the test results, and a statistical method was used to evaluate the required number of tests that are sufficient to obtain an average result with high confidence. In most cases, the required number of tests is much higher than what is practically feasible. This work was conducted as part of the European Defence Agency-project CERAMBALL. 相似文献
826.
张建国 《海军工程大学学报》1994,(3)
本文论述了用蒙特卡罗方法直接模拟计算非带电粒子辐射的屏蔽穿透概率问题,讨论了粒子穿透概率无偏估计的两种实际情况,探讨了将粒子输运理论应用于解决实际辐射物理问题的途径。 相似文献
827.
828.
针对压力容器制造、使用过程中各种参数的不确定性,提出了一种基于响应平面的随机分析方法.根据某压力容器的结构特点,确定性有限元分析采用了接触有限元,结合中心组合抽样设计构建了容器最大应力的响应平面,以此为基础对压力容器应力分布进行了随机分析.可靠性分析中引入应力—强度干涉模型,并分别对容器壁面和接管处进行了可靠性评定.实... 相似文献
829.
In this study, we illustrate a real‐time approximate dynamic programming (RTADP) method for solving multistage capacity decision problems in a stochastic manufacturing environment, by using an exemplary three‐stage manufacturing system with recycle. The system is a moderate size queuing network, which experiences stochastic variations in demand and product yield. The dynamic capacity decision problem is formulated as a Markov decision process (MDP). The proposed RTADP method starts with a set of heuristics and learns a superior quality solution by interacting with the stochastic system via simulation. The curse‐of‐dimensionality associated with DP methods is alleviated by the adoption of several notions including “evolving set of relevant states,” for which the value function table is built and updated, “adaptive action set” for keeping track of attractive action candidates, and “nonparametric k nearest neighbor averager” for value function approximation. The performance of the learned solution is evaluated against (1) an “ideal” solution derived using a mixed integer programming (MIP) formulation, which assumes full knowledge of future realized values of the stochastic variables (2) a myopic heuristic solution, and (3) a sample path based rolling horizon MIP solution. The policy learned through the RTADP method turned out to be superior to polices of 2 and 3. © 2010 Wiley Periodicals, Inc. Naval Research Logistics 2010 相似文献
830.
为解决飞机在低空突防过程中的雷达地形遮蔽盲区快速计算问题,提出了一种基于转盘爬虫对象的快速算法。首先介绍了雷达盲区产生的因素,分析了地形遮蔽和地球曲率盲区的计算模型,然后定义了转盘及爬虫对象,并设计了基于转盘爬虫对象的地形遮蔽盲区计算方法和流程。在此基础上,将雷达地形遮蔽盲区计算结果进行三维建模及可视化,通过典型算例对算法进行对比测试和实验,得到不同高度的雷达地形遮蔽盲区分布图及三维可视化模型,证明了算法的快速性和可行性。 相似文献