全文获取类型
收费全文 | 602篇 |
免费 | 24篇 |
出版年
2021年 | 8篇 |
2019年 | 12篇 |
2018年 | 8篇 |
2017年 | 15篇 |
2016年 | 12篇 |
2015年 | 10篇 |
2014年 | 13篇 |
2013年 | 95篇 |
2011年 | 8篇 |
2010年 | 7篇 |
2009年 | 8篇 |
2007年 | 7篇 |
2006年 | 7篇 |
2005年 | 7篇 |
2004年 | 10篇 |
2002年 | 11篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1998年 | 10篇 |
1997年 | 15篇 |
1996年 | 8篇 |
1995年 | 14篇 |
1994年 | 15篇 |
1993年 | 19篇 |
1992年 | 11篇 |
1991年 | 14篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 17篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 16篇 |
1984年 | 16篇 |
1983年 | 8篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1975年 | 8篇 |
1974年 | 13篇 |
1973年 | 7篇 |
1972年 | 10篇 |
1971年 | 12篇 |
1970年 | 6篇 |
1969年 | 7篇 |
1968年 | 6篇 |
1967年 | 6篇 |
排序方式: 共有626条查询结果,搜索用时 15 毫秒
211.
AbstractThe utilization of health care services by veterans has received much attention in recent years. However, the impact of the large array of factors affecting the veterans’ demand for health care services remains understudied. These factors include individual socio-demographic and economic characteristics, the availability of various sources of health insurance, and the prevalence of medical conditions. We use public data to analyze how veterans’ utilization of health care services varies with these factors. We also analyze how the reliance on VA services varies when alternative sources of health insurance are available to veterans. Based on the estimated relationships, we use a micro-simulation model to forecast future health care utilization, both inside and outside of VA. 相似文献
212.
213.
We consider parallel‐machine scheduling with a common server and job preemption to minimize the makespan. While the non‐preemptive version of the problem is strongly NP‐hard, the complexity status of the preemptive version has remained open. We show that the preemptive version is NP‐hard even if there is a fixed number of machines. We give a pseudo‐polynomial time algorithm to solve the case with two machines. We show that the case with an arbitrary number of machines is unary NP‐hard, analyze the performance ratios of some natural heuristic algorithms, and present several solvable special cases. © 2017 Wiley Periodicals, Inc. Naval Research Logistics 64: 388–398, 2017 相似文献
214.
The Replenishment at Sea Planner (RASP) is saving the U.S. Navy millions of dollars a year by reducing fuel consumption of its Combat Logistics Force (CLF). CLF shuttle supply ships deploy from ports to rendezvous with underway U.S. combatants and those of coalition partners. The overwhelming commodity transferred is fuel, ship‐to‐ship by hoses, while other important packaged goods and spare parts are high‐lined, or helicoptered between ships. The U.S. Navy is organized in large areas of responsibility called numbered fleets, and within each of these a scheduler must promulgate a daily forecast of CLF shuttle operations. The operational planning horizon extends out several weeks, or as far into the future as we can forecast demand. We solve RASP with integer linear optimization and a purpose‐built heuristic. RASP plans Replenishment‐at‐Sea (RAS) events with 4‐hour (Navy watch) time fidelity. For five years, RASP has served two purposes: (1) it helps schedulers generate a daily schedule and animates it using Google Earth, and (2) it automates reports command‐to‐ship messages that are essential to keep this complex logistics system operating. 相似文献
215.
216.
针对加速度计长期自然贮存于不同温度应力下,试验数据为成败型不完全数据,贮存寿命无法准确评估的难题,运用极小x~2估计和拟合优度检验相结合的方法来拟合产品的失效分布,通过Matlab软件中的fminsearch函数确定了不同温度下的分布参数,采用最小二乘法求解了参数与温度之间的函数关系,提出了该类型加速度计基于不同温度的失效分布函数,并预测了正常温度下贮存寿命为16.8 a。结果表明:提出的加速度计失效分布函数更能反映加速度计在不同温度下的贮存寿命变化规律,在工程研究领域具有一定的实用价值。 相似文献
217.
卫星具有覆盖范围广、可长时间稳定运行、无国界限制、安全性高等独特优势,是提升部队作战效能的"倍增器",也是解决大范围战场信息支撑能力问题的有效手段和最佳途径。21世纪初,高速增长的经济推动越南航天事业驶入了发展的快车道,不仅实现了卫星发射的零突破,还相继发射了多颗通信卫星、遥感卫星和试验型纳卫星。文章主要对越南当前的卫星现状进行总结归纳,并分析其未来的发展计划。 相似文献
218.
In this article, we address a stochastic generalized assignment machine scheduling problem in which the processing times of jobs are assumed to be random variables. We develop a branch‐and‐price (B&P) approach for solving this problem wherein the pricing problem is separable with respect to each machine, and has the structure of a multidimensional knapsack problem. In addition, we explore two other extensions of this method—one that utilizes a dual‐stabilization technique and another that incorporates an advanced‐start procedure to obtain an initial feasible solution. We compare the performance of these methods with that of the branch‐and‐cut (B&C) method within CPLEX. Our results show that all B&P‐based approaches perform better than the B&C method, with the best performance obtained for the B&P procedure that includes both the extensions aforementioned. We also utilize a Monte Carlo method within the B&P scheme, which affords the use of a small subset of scenarios at a time to estimate the “true” optimal objective function value. Our experimental investigation reveals that this approach readily yields solutions lying within 5% of optimality, while providing more than a 10‐fold savings in CPU times in comparison with the best of the other proposed B&P procedures. © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 131–143, 2014 相似文献
219.
Goodness C. Aye Mehmet Balcilar Rangan Gupta Reneé van Eyden 《Defence and Peace Economics》2014,25(6):619-633
This paper contributes to the growing literature on the milex-growth nexus, by providing a case study of South Africa and considering the possibility of structural breaks by applying newly developed econometric methods. Using full sample bootstrap Granger non-causality tests, no Granger causal link is found between military expenditure and GDP for 1951–2010, but parameter instability tests show the estimated VARs to be unstable. Using a bootstrap rolling window estimation procedure, however, finds evidence of bidirectional Granger causality in various subsamples. This implies standard Granger non-causality tests, which neither account for structural breaks nor time variation may be invalid. 相似文献
220.
P.I. Kasatkin 《Defense & Security Analysis》2014,30(4):311-322
The article studies the range of problems that have emerged due to the growing immigration from Muslim countries into the European Union (EU). While describing the functions of immigrants' communities, the authors focus on their political role in the receiving states. The study of the historical development of government–diaspora relations in three cases (the UK, France, and Germany) shows that Muslim communities' political influence does not reflect their economic and cultural role, which in the future might threaten the EU security, unless these countries develop a new approach to an “acculturation” policy. 相似文献