全文获取类型
收费全文 | 157篇 |
免费 | 45篇 |
国内免费 | 11篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 7篇 |
2016年 | 14篇 |
2015年 | 6篇 |
2014年 | 11篇 |
2013年 | 8篇 |
2012年 | 17篇 |
2011年 | 13篇 |
2010年 | 6篇 |
2009年 | 11篇 |
2008年 | 14篇 |
2007年 | 15篇 |
2006年 | 8篇 |
2005年 | 10篇 |
2004年 | 12篇 |
2003年 | 5篇 |
2002年 | 9篇 |
2001年 | 9篇 |
2000年 | 1篇 |
1999年 | 8篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1991年 | 2篇 |
排序方式: 共有213条查询结果,搜索用时 125 毫秒
121.
对于采用储气井储存方式的CNG加气站,其与附近民用建筑的防火间距问题,在目前的规范中没有相应要求。而在《汽车加油加气站设计与施工规范》中虽有储气井与民用建筑的防火距离规定,但对民用建筑的保护类别界定在实际操作中较困难。结合实际工程,通过采用对储气井储存方式的CNG加气站各工艺设备进行火灾和爆炸危险性的量化分析,验证了其与附近民用建筑的防火间距,为此类工程设计提供了方法和依据。 相似文献
122.
123.
在建立多种类型武器目标分配模型的基础上,提出了一种求解该模型的改进粒子群算法。首先,定义粒子聚焦距离变化率,使惯性权重依据聚焦距离变化率自适应调整;其次,采用速度最大值线性递减的策略平衡算法收敛精度与全局寻优能力之间的矛盾;最后,粒子替换策略使算法改善了因自适应惯性权重的引入而造成收敛速度变慢的问题。仿真结果表明,提出模型和算法合理有效,算法收敛快,适合求解各种种群规模的武器目标分配问题。 相似文献
124.
125.
利用非线性模型预测控制(nonlinear model predictive control,NMPC)的思想建立了战机末端规避导弹的机动策略求解方法。根据导弹与战机的空战态势,建立了导弹与战机的相对运动微分方程;将导弹的导引律引入到导弹运动模型中,与飞机模型一起构建了系统预测模型,并对飞机和导弹的运动约束进行了分析。通过对导弹结构限制和战术特性的分析,给出了飞机机动规避导弹的性能指标,进而建立了机动规避导弹的最优控制模型。利用高斯伪谱法对模型进行求解,采用滚动优化策略实现了对机动规避策略的闭环求解。针对导弹气动参数和导航比未知以及相对测量量具有噪声的问题,利用极大似然法对导弹的气动参数和导航比进行估计,实现了对系统预测模型的反馈校正。仿真结果表明,此方法能够实现对导弹的机动规避。 相似文献
126.
127.
基于尾流自导鱼雷的制导原理、弹道和自导开机过程,提出了最小开机距离的概念。分析指出了影响尾流自导鱼雷最小开机距离的主要因素是设定的鱼雷深度、鱼雷的航行精度和目标运动参数散布等。建立了最小开机距离的计算模型,并在不同攻击态势下进行了仿真计算和统计分析,得出了有益的结论:在一定的攻击条件下,不同的设定深度、使用不同的鱼雷速制以及不同的目标运动要素误差、鱼雷航行精度,将使鱼雷的最小开机距离不同,即鱼雷的最小开机距离实际上是关于各种因素的函数。通过最小开机距离可以进一步计算出鱼雷自导开机的最大距离,若在工程中予以实现,将对提高潜艇攻击的隐蔽性和鱼雷作战效能具有重要意义。 相似文献
128.
We study a class of new scheduling problems which involve types of teamwork tasks. Each teamwork task consists of several components, and requires a team of processors to complete, with each team member to process a particular component of the task. Once the processor completes its work on the task, it will be available immediately to work on the next task regardless of whether the other components of the last task have been completed or not. Thus, the processors in a team neither have to start, nor have to finish, at the same time as they process a task. A task is completed only when all of its components have been processed. The problem is to find an optimal schedule to process all tasks, under a given objective measure. We consider both deterministic and stochastic models. For the deterministic model, we find that the optimal schedule exhibits the pattern that all processors must adopt the same sequence to process the tasks, even under a general objective function GC = F(f1(C1), f2(C2), … , fn(Cn)), where fi(Ci) is a general, nondecreasing function of the completion time Ci of task i. We show that the optimal sequence to minimize the maximum cost MC = max fi(Ci) can be derived by a simple rule if there exists an order f1(t) ≤ … ≤ fn(t) for all t between the functions {fi(t)}. We further show that the optimal sequence to minimize the total cost TC = ∑ fi(Ci) can be constructed by a dynamic programming algorithm. For the stochastic model, we study three optimization criteria: (A) almost sure minimization; (B) stochastic ordering; and (C) expected cost minimization. For criterion (A), we show that the results for the corresponding deterministic model can be easily generalized. However, stochastic problems with criteria (B) and (C) become quite difficult. Conditions under which the optimal solutions can be found for these two criteria are derived. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004 相似文献
129.
A problem we call recurrent construction involves manufacturing large, complex, expensive products such as airplanes, houses, and ships. Customers order configurations of these products well in advance of due dates for delivery. Early delivery may not be permitted. How should the manufacturer determine when to purchase and release materials before fabrication, assembly, and delivery? Major material expenses, significant penalties for deliveries beyond due dates, and long product makespans in recurrent construction motivate choosing a release timetable that maximizes the net present value of cash flows. Our heuristic first projects an initial schedule that dispatches worker teams to tasks for the backlogged products, and then solves a series of maximal closure problems to find material release times that maximize NPV. This method compares favorably with other well‐known work release heuristics in solution quality for large problems over a wide range of operating conditions, including order strength, cost structure, utilization level, batch policy, and uncertainty level. Computation times exhibit near linear growth in problem size. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004 相似文献
130.
Parametric inference for component distributions from lifetimes of systems with dependent components
In system reliability analysis, for an n ‐component system, the estimation of the performance of the components in the system is not straightforward in practice, especially when the components are dependent. Here, by assuming the n components in the system to be identically distributed with a common distribution belonging to a scale‐family and the dependence structure between the components being known, we discuss the estimation of the lifetime distributions of the components in the system based on the lifetimes of systems with the same structure. We develop a general framework for inference on the scale parameter of the component lifetime distribution. Specifically, the method of moments estimator (MME) and the maximum likelihood estimator (MLE) are derived for the scale parameter, and the conditions for the existence of the MLE are also discussed. The asymptotic confidence intervals for the scale parameter are also developed based on the MME and the MLE. General simulation procedures for the system lifetime under this model are described. Finally, some examples of two‐ and three‐component systems are presented to illustrate all the inferential procedures developed here. © 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2012 相似文献