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351.
加速退化试验广泛应用于橡胶密封件等长寿命产品的可靠性评估,试验过程中需要将高应力水平下的试验结果外推到正常应力水平。要获得准确的产品可靠性评估结果,需要保证加速应力下的退化失效机理与正常应力下的退化失效机理一致。基于似然比检验原理,提出加速退化试验机理一致性判别方法及流程。针对失效机理一致与失效机理变化两种场合,提出对数线性及非对数线性两类加速模型,并结合混合效应模型描述产品退化过程。利用似然比检验判断加速模型参数是否变化,完成失效机理一致性判别。仿真算例和应用实例表明,该方法能够有效判别橡胶密封件失效机理是否变化,并找到失效机理不变的应力水平边界。 相似文献
352.
This article provides conditions under which total‐cost and average‐cost Markov decision processes (MDPs) can be reduced to discounted ones. Results are given for transient total‐cost MDPs with transition rates whose values may be greater than one, as well as for average‐cost MDPs with transition probabilities satisfying the condition that there is a state such that the expected time to reach it is uniformly bounded for all initial states and stationary policies. In particular, these reductions imply sufficient conditions for the validity of optimality equations and the existence of stationary optimal policies for MDPs with undiscounted total cost and average‐cost criteria. When the state and action sets are finite, these reductions lead to linear programming formulations and complexity estimates for MDPs under the aforementioned criteria.© 2017 Wiley Periodicals, Inc. Naval Research Logistics 66:38–56, 2019 相似文献
353.
Operating costs per unit of input or output are often claimed to grow faster in defence than elsewhere in the economy. In this paper, we outline several possible reasons as to why operating costs increase at higher rates in defence, including differences in the input factor mix and productivity growth, the technological complexity required to maintain the relative effect of weapon systems and a gradual reduction in the number of units and activity. We investigate whether operating costs grow at a faster rate than elsewhere in the economy, by estimating growth in real output unit costs in the Norwegian Armed Forces for the period 1994–2013, using activity as a measure of output. We find no increase beyond general inflation in structural (fixed) costs, whereas activity-based (variable) costs per unit of activity increase significantly. 相似文献
354.
在装备再制造周期及再制造费用基本概念的基础上,给出了再制造费用参数的相关内容,并阐述了工程估算法、专家判断估算法、参数估算法、类比估算法等4种装备再制造费用分析及预测估算的方法,构建了基于工程估算法的再制造费用分解结构,并对再制造费用分析流程进行了详细描述,可为形成正确的再制造设计方案提供费用决策依据。 相似文献
355.
装备维修宏观调控指标体系研究 总被引:3,自引:0,他引:3
在对大量历史数据的统计分析基础上 ,科学确定了全军装备维修宏观管理所需的调控指标 ,并建立了计量经济学模型和回归模型 ,为装备维修宏观调控提供了基本依据。 相似文献
356.
357.
358.
离子束加工误差对散射损失的影响研究 总被引:1,自引:0,他引:1
离子束加工(Ion Beam Figuring,IBF)去除函数对加工残差具有重要的影响,而加工残差引起的表面散射则导致光学性能发生变化.为了减小加工残差对光学性能的影响,利用基于CCOS成形原理的离子束加工仿真程序对光学镜面进行修形,分析不同去除函数宽度对散射损失(Ratio of Scattering Loss,RSL)指标的影响.通过研究可知,随着去除函数宽度的减小,加工残差对散射损失的影响越来越小.因此,根据加工残差对RSL指标的影响程度以及RSL指标要求,可以合理选择去除函数宽度,从而在满足面形精度的同时,优化加工工艺. 相似文献
359.
The signature of a system with independent and identically distributed (i.i.d.) component lifetimes is a vector whose ith element is the probability that the ith component failure is fatal to the system. System signatures have been found to be quite useful tools in the study and comparison of engineered systems. In this article, the theory of system signatures is extended to versions of signatures applicable in dynamic reliability settings. It is shown that, when a working used system is inspected at time t and it is noted that precisely k failures have occurred, the vector s [0,1]n‐k whose jth element is the probability that the (k + j)th component failure is fatal to the system, for j = 1,2,2026;,n ‐ k, is a distribution‐free measure of the design of the residual system. Next, known representation and preservation theorems for system signatures are generalized to dynamic versions. Two additional applications of dynamic signatures are studied in detail. The well‐known “new better than used” (NBU) property of aging systems is extended to a uniform (UNBU) version, which compares systems when new and when used, conditional on the known number of failures. Sufficient conditions are given for a system to have the UNBU property. The application of dynamic signatures to the engineering practice of “burn‐in” is also treated. Specifically, we consider the comparison of new systems with working used systems burned‐in to a given ordered component failure time. In a reliability economics framework, we illustrate how one might compare a new system to one successfully burned‐in to the kth component failure, and we identify circumstances in which burn‐in is inferior (or is superior) to the fielding of a new system. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2009 相似文献
360.
Jomana Amara 《Defense & Security Analysis》2019,35(3):326-342
In 1968, President Nixon established the Commission on an All-Volunteer Armed Force, or the Gates Commission, which served as the impetus and justification for an All-Volunteer Force (AVF). At the end of its deliberations, the commission recommended abolishing the draft and transforming the U.S. military into a force of volunteers beginning in 1973. Interestingly, the debate regarding the merits of both systems appeared to be largely economic – with cost–benefit analysis playing the primary role. Lately, we are beginning to see a new, politically-motivated impetus for returning to a “system of national service.” The ideas spurring this debate are many: the need to reaffirm the nation state, the commitment of citizens to the state, political ownership and oversight of the forces, the need for social equity in serving the nation, limiting the support for armed conflict by burden-sharing among citizens, and equitably spreading the personal cost of war. 相似文献