全文获取类型
收费全文 | 578篇 |
免费 | 9篇 |
出版年
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2017年 | 11篇 |
2016年 | 15篇 |
2015年 | 10篇 |
2014年 | 12篇 |
2013年 | 104篇 |
2012年 | 22篇 |
2011年 | 27篇 |
2010年 | 23篇 |
2009年 | 15篇 |
2008年 | 30篇 |
2007年 | 13篇 |
2006年 | 15篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2002年 | 3篇 |
2001年 | 4篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 3篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 9篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1973年 | 4篇 |
1972年 | 14篇 |
1971年 | 3篇 |
1970年 | 5篇 |
1969年 | 11篇 |
1968年 | 7篇 |
1967年 | 4篇 |
1966年 | 5篇 |
排序方式: 共有587条查询结果,搜索用时 0 毫秒
81.
82.
基于RDC模块的角度测量仪的设计与实现 总被引:1,自引:0,他引:1
设计了一种便携式的角度测量仪.介绍了自整角机/旋转变压器信号处理原理,设计了信号量程放大电路.通过单片机控制,将角度信息显示在测量仪上并将数据传输显示在PC机,实现了角度监测.测试验证表明:该设计方法测量精度高、电压信号输入范围宽、可靠性好,完全可以满足角度测量及实时监测的要求. 相似文献
83.
目标的电磁散射特性研究对于实现雷达探测、识别、跟踪目标起着至关重要的作用,而雷达散射截面(Radar Cross Section,RCS)又是体现目标电磁散射特性的一个重要方面.参数曲面能精确模拟目标的几何外形,提高计算精度.采用参数曲面——双线性表面建模,运用物理光学(Physical Optics,PO)法计算电大... 相似文献
84.
Consider a project during the life cycle of which there are cash payouts and in‐flows. To better meet his financial commitments, the project owner would like to meet all deadlines without running out of cash. We show that the cash availability objective is similar to the total weighted flowtime used to measure work‐in‐progress performance in the scheduling and inventory control literatures. In this article we provide several specialized solution methods for the problem of minimizing total weighted flowtime in an arbitrary acyclic project network, subject to activity release times and due dates, where the activity weights may be positive or negative and represent cash in‐ and out‐flows. We describe the structure of an optimal solution and provide several efficient algorithms and their complexity based on mincost and maxflow formulations. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006 相似文献
85.
The UK Ministry of Defence is British industry's largest single customer and a number of firms and industries are highly dependent on defence sales. Various hypotheses have been proposed about the impact of defence procurement on firms and these are investigated using four performance indicators: financial structure, investment, productivity and profitability. With regard to the borrowing ratio, capital investment and the rate of return, there is no statistically significant difference between the mean financial ratios for low and high dependence firms. However, non‐dependents appear to have a higher level and rate of growth of labour productivity than dependents. 相似文献
86.
Lani Miyoshi Sanders Sharon M. DeLand Arian L. Pregenzer 《The Nonproliferation Review》2013,20(3):475-489
In his 2009 Prague speech and the 2010 Nuclear Posture Review, President Barack Obama committed the United States to take concrete steps toward nuclear disarmament while maintaining a safe, secure, and effective nuclear deterrent. There is an inherent tension between these two goals that is best addressed through improved integration of nuclear weapons objectives with nuclear arms control objectives. This article reviews historical examples of the interaction between the two sets of objectives, develops a framework for analyzing opportunities for future integration, and suggests specific ideas that could benefit the nuclear weapons enterprise as it undergoes transformation and that could make the future enterprise compatible with a variety of arms control futures. 相似文献
87.
88.
This article presents a proposed theory of how war economies are formed and maintained, as well as an integrated policy framework to guide the dismantling of war economies emanating from the proposed theory. Additionally, six potential areas for future research pertaining to the dismantling of war economies are also presented. 相似文献
89.
Janne E. Nolan 《The Nonproliferation Review》2013,20(2):273-277
ABSTRACTWidespread and often exaggerated generalizations about the global spread weapons of mass destruction (WMDs) have proven to be not only misleading and technologically naïve, but also unhelpful in formulating effective policies to counter their threat. The new book by George Mason University's Sonia Ben Ouagrham-Gormley dispels the popular narrative that governments and terror groups can easily—and inevitably will—develop WMDs, particularly biological weapons, by exploring the complex external and internal conditions that such programs require, as demonstrated by the Cold War-era biological weapon programs of the superpowers. This empirically grounded and realistic assessment of how states try—and often fail—to develop such programs offers a more reliable basis to craft realistic counterproliferation policies that can elicit international support. 相似文献
90.
International safeguards is the system of measures put in place by the International Atomic Energy Agency and states to ensure nuclear programs remain dedicated to peaceful purposes. This international safeguards system consists of agreements, inspections, and evaluations that have never considered the safeguards culture of a state or facility. Neither a common definition nor an understanding of safeguards culture is internationally recognized. This article provides an analysis of the concept of safeguards culture and gauges its value to the international safeguards community. The authors explore distinctions among safeguards culture, safeguards compliance, and safeguards performance, and suggest possible indicators of safeguards culture and methods to promote a strong, positive safeguards culture. 相似文献