首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   314篇
  免费   102篇
  国内免费   10篇
  2024年   1篇
  2023年   6篇
  2022年   8篇
  2021年   18篇
  2020年   11篇
  2019年   7篇
  2018年   7篇
  2017年   12篇
  2016年   14篇
  2015年   28篇
  2014年   36篇
  2013年   18篇
  2012年   15篇
  2011年   28篇
  2010年   29篇
  2009年   18篇
  2008年   19篇
  2007年   16篇
  2006年   16篇
  2005年   23篇
  2004年   15篇
  2003年   13篇
  2002年   5篇
  2001年   14篇
  2000年   10篇
  1999年   7篇
  1998年   8篇
  1997年   5篇
  1996年   2篇
  1995年   5篇
  1994年   1篇
  1993年   3篇
  1992年   3篇
  1991年   1篇
  1989年   2篇
  1988年   2篇
排序方式: 共有426条查询结果,搜索用时 15 毫秒
151.
本文用实验方法从频域和时域两个方面研究了涂覆吸波材料目标的电磁散射,结果表明超宽带信号比常规雷达的窄带信号对付涂覆吸波材料目标有10~12dB好处,说明超宽带信号的确具有抗窄带吸波材料的良好能力。  相似文献   
152.
本文综述现代水面舰船结构的若干进展,从舰船结构材料、结构型式以及舰船生存能力等方面进行评述。  相似文献   
153.
充电法在复合材料静电测试中的问题   总被引:2,自引:0,他引:2  
按照GJB2605-96中有关静电衰减性能测试的要求,自制了复合材料静电衰减性能测试装置。用这套测试装置对9种不同结构的复合材料进行了实验研究。研究表明,利用充电法测试材料静电衰减性能时,由于电容效应,测试结果不能正确反映被测材料的静电性能。  相似文献   
154.
通过对КВΓ-76型锅炉蒸发管束强度计算的分析验算,发现原设计在某些参数的选取上存在明显的误差,导致选材要求过高.经过论证,得出可用普通碳素钢管替代低合金钢管的结论.  相似文献   
155.
本文介绍了抗超高速撞击多层结构复合材料的设计、制备和实验,并对结果进行了讨论,实验证明,以SiC陶瓷基复合材料为防护层、以空心微珠或多孔变密度复合材料为缓冲层、以编织物复合材料为结构层的多层结构复合材料,具有面密度低、抗撞击速度范围宽、抗撞击性能好的特点。  相似文献   
156.
本文根据隐蔽锥扫雷达天线的工作原理,从方向性函数出发,分析了接收状态下高频馈电网络中,和差信号的幅相特性与隐蔽锥扫波束交叉点电平的关系,从而对不能自动跟踪的隐蔽锥扫雷达,从天馈系统方面分析了原因,并为设计和部队维修提供了理论根据和有效方法。  相似文献   
157.
随着现代信号处理技术的发展,对非平稳信号分析和处理的小波分析技术已成功应用于雷达目标特性分析领域,大功率单脉冲雷达作为我国航天测控网当中的主干设备,具有一定的目标特性识别能力。主要针对目前靶场的现有装备,讨论了基于小波理论的单脉冲雷达空间目标RCS特性测量,并对窄带低分辨率雷达在未来空间目标识别中发挥其作用谈了作者的看法。  相似文献   
158.
ABSTRACT

The present international standard allows non-nuclear weapon states (NNWS) to forego safeguards when nuclear material is used in a “non-proscribed military activity,” though no criteria have been established to determine when NNWS can remove naval nuclear material from safeguards. Though at present, only nuclear-armed states possess nuclear submarines, the global nuclear naval landscape may soon change with the advancement of Brazil's fledgling program and the possible precedent it would set for other NNWS. A framework is needed to shore up nuclear security and prevent nuclear material diversion from the nuclear naval sector. Proposed and existing nonproliferation frameworks, including a Fissile Material Cut-off Treaty and commitments through the nuclear security summits, are insufficient to close this loophole. A Naval Use Safeguards Agreement (NUSA), modeled after the Additional Protocol of the International Atomic Energy Agency, would provide a framework to remove the opacity surrounding nuclear material in the naval sector. Designed for NNWS and encouraged as confidence-building measures for nuclear weapon states, NUSA would explicitly outline those stages in the naval nuclear fuel cycle where safeguards are to be applied and in what context. This viewpoint also further provides direction for targeted research and development in technical naval nuclear safeguards solutions.  相似文献   
159.
Unprecedented interest in seeking progress toward nuclear disarmament exists today; even some nuclear weapon states are looking for new ways to strengthen this process. National declarations of fissile material holdings—highly enriched uranium and plutonium—could play an important role in supporting this effort, facilitating not only transparency but also the irreversibility of the process. This article discusses what kind of content such declarations could have in order to be meaningful and effective, the sequence of data on fissile material holdings that states might release, and some of the challenges to be expected in reconstructing historic fissile material production; it also summarizes current attitudes of weapon states toward making such declarations. Initial declarations can be valuable as confidence-building measures, but better and more background data are necessary if declarations are to serve as the groundwork for deeper cuts in the nuclear arsenals. A robust verification approach would ultimately require inspectors to have access to fissile material production and storage sites. The methods and tools of nuclear forensic analysis—in this context also dubbed nuclear archaeology—would be a key element of this process. This article discusses the capabilities and limitations of potential approaches to verifying declarations of historic production of plutonium and highly enriched uranium; it also identifies and discusses opportunities for further research and development.  相似文献   
160.
Current U.S. nuclear weapons strategy, force structure, and doctrine contribute to the threat of nuclear terrorism in several ways. First, the U.S. nuclear stockpile presents opportunities for nuclear terrorists to seize the materials they need. Second, U.S. nuclear forces remain a key justification for Russia's maintenance of similar nuclear forces that are less well protected. Third, America's continued embrace of nuclear weapons encourages and legitimizes other states to seek nuclear weapons that they will have difficulty securing from terrorists. The national security interests of the United States would be better served by a strategy to shrink the global footprint of nuclear weapons and provide the highest possible levels of security for the most minimal possible deterrent forces. Given the inability to secure nuclear weapons and materials perfectly or to eliminate terrorism in the foreseeable future, reducing the global inventory of nuclear weapons and materials is the most reliable way to reduce the chances of nuclear terrorism.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号