全文获取类型
收费全文 | 394篇 |
免费 | 151篇 |
国内免费 | 28篇 |
专业分类
573篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 6篇 |
2020年 | 11篇 |
2019年 | 8篇 |
2018年 | 2篇 |
2017年 | 23篇 |
2016年 | 27篇 |
2015年 | 20篇 |
2014年 | 34篇 |
2013年 | 29篇 |
2012年 | 31篇 |
2011年 | 24篇 |
2010年 | 20篇 |
2009年 | 43篇 |
2008年 | 32篇 |
2007年 | 30篇 |
2006年 | 32篇 |
2005年 | 18篇 |
2004年 | 30篇 |
2003年 | 16篇 |
2002年 | 11篇 |
2001年 | 21篇 |
2000年 | 15篇 |
1999年 | 5篇 |
1998年 | 7篇 |
1997年 | 9篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 9篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 11篇 |
1989年 | 3篇 |
1988年 | 2篇 |
排序方式: 共有573条查询结果,搜索用时 0 毫秒
391.
反舰导弹末制导雷达的目标选择方法主要采用"先入为主"和"录取对比"方法。从影响目标选择的误差因素出发,对这两种目标选择方法的原理进行了分析研究。研究表明:这两种方法都是基于选择点的预定目标选择方法;且由于受自控终点散布误差和目标机动误差的影响,基于选择点的预定目标选择方法不适应超视距应用。蒙特卡罗仿真表明,预定目标上释放冲淡干扰时,基于选择点的预定目标选择方法已基本不具备预定目标选择能力,超视距情况下正确选择预定目标的概率低于0.2。 相似文献
392.
393.
油罐的壁厚设计关系到油罐的经济性和可靠性,如何把握两者的辩证关系对油罐的设计与建设具有十分重要的意义。传统上大型油罐壁厚设计采用的是变点法;以可靠度理论为基础,以可靠性分析模型为核心,提出利用可靠度法求解大型油罐壁厚的新方法。以50 000 m3油罐为例,编程分析并计算以2种方法设计的壁厚。变点法设计的底圈罐壁厚度与圈数无关;以中心点可靠度法求解壁厚,可靠性指标一定时,底圈罐壁厚度同样与圈数无关。探讨可靠度法求解壁厚的可行性,验证变点法设计壁厚的可靠性。 相似文献
394.
We consider a parallel‐machine scheduling problem with jobs that require setups. The duration of a setup does not depend only on the job just completed but on a number of preceding jobs. These setup times are referred to as history‐dependent. Such a scheduling problem is often encountered in the food processing industry as well as in other process industries. In our model, we consider two types of setup times—a regular setup time and a major setup time that becomes necessary after several “hard‐to‐clean” jobs have been processed on the same machine. We consider multiple objectives, including facility utilization, flexibility, number of major setups, and tardiness. We solve several special cases assuming predetermined job sequences and propose strongly polynomial time algorithms to determine the optimal timing of the major setups for given job sequences. We also extend our analysis to develop pseudopolynomial time algorithms for cases with additional objectives, including the total weighted completion time, the total weighted tardiness, and the weighted number of tardy jobs. © 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2012 相似文献
395.
This article treats the problem of subdividing an area for storing containers such that the workload is evenly shared among the cranes operating the resulting subareas. We consider two crane sets: while noncrossing constraints between cranes of the same set need to be observed, cranes of different sets do not interfere. Such a problem setting is, for instance, relevant for scheduling the (un‐)loading of vessels by parallel quay cranes operating on opposing berths or in container yards with cross‐over cranes. We formalize the resulting optimization problem, prove computational complexity, and present exact and heuristic solution procedures. © 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2012 相似文献
396.
397.
在对潜搜索中,针对搜索兵力武器装备战技性能的优劣、指挥人员的军政素质的高低、水文气象条件的好坏等因素均会随着时间的推移而发生变化的特点,为了取得最佳的搜潜效果,需要根据时间变化给不同的作战单元分派不同的作战任务.将整数规划与灰色模型相结合,建立了对潜搜索的灰色整数规划模型,给出了检验方法和求解步骤,并举例分析说明.经验证,该模型精度等级较高,且能使各作战单元的搜索效率达到最佳,因此,可资对潜搜索兵力分配时借鉴. 相似文献
398.
以已完成的"平台罗经综合训练模拟器"为基础,给出了训练模拟器软硬件的设计方法及其实现要点,对同类模拟器的研制具有借鉴和参考作用. 相似文献
399.
In hinterland container transportation the use of barges is getting more and more important. We propose a real‐life operational planning problem model from an inland terminal operating company, in which the number of containers shipped per barge is maximized and the number of terminals visited per barge is minimized. This problem is solved with an integer linear program (ILP), yielding strong cost reductions, about 20%, compared to the method used currently in practice. Besides, we develop a heuristic that solves the ILP in two stages. First, it decides for each barge which terminals to visit and second it assigns containers to the barges. This heuristic produces almost always optimal solutions and otherwise near‐optimal solutions. Moreover, the heuristic runs much faster than the ILP, especially for large‐sized instances. 相似文献
400.
This article is concerned with the determination of pricing strategies for a firm that in each period of a finite horizon receives replenishment quantities of a single product which it sells in two markets, for example, a long‐distance market and an on‐site market. The key difference between the two markets is that the long‐distance market provides for a one period delay in demand fulfillment. In contrast, on‐site orders must be filled immediately as the customer is at the physical on‐site location. We model the demands in consecutive periods as independent random variables and their distributions depend on the item's price in accordance with two general stochastic demand functions: additive or multiplicative. The firm uses a single pool of inventory to fulfill demands from both markets. We investigate properties of the structure of the dynamic pricing strategy that maximizes the total expected discounted profit over the finite time horizon, under fixed or controlled replenishment conditions. Further, we provide conditions under which one market may be the preferred outlet to sale over the other. © 2015 Wiley Periodicals, Inc. Naval Research Logistics 62: 531–549, 2015 相似文献