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   1163篇
  免费   295篇
  国内免费   120篇
  1578篇
  2024年   4篇
  2023年   6篇
  2022年   22篇
  2021年   27篇
  2020年   21篇
  2019年   10篇
  2018年   20篇
  2017年   48篇
  2016年   67篇
  2015年   51篇
  2014年   84篇
  2013年   82篇
  2012年   84篇
  2011年   91篇
  2010年   89篇
  2009年   105篇
  2008年   76篇
  2007年   84篇
  2006年   101篇
  2005年   82篇
  2004年   75篇
  2003年   44篇
  2002年   30篇
  2001年   31篇
  2000年   45篇
  1999年   26篇
  1998年   23篇
  1997年   25篇
  1996年   26篇
  1995年   15篇
  1994年   16篇
  1993年   16篇
  1992年   19篇
  1991年   13篇
  1990年   12篇
  1989年   5篇
  1988年   3篇
排序方式: 共有1578条查询结果,搜索用时 15 毫秒
661.
Abstract

The current field study used unique data collected in Israel in July 2014, during a military operation that the Israel Defence Forces (I.D.F.) conducted in the Gaza Strip, in reaction to the thousands of missiles launched from there into Israel. During this operation, the new Iron Dome anti-missile defence system was used to protect Israelis exposed to missile attacks. The study examined factors that correlate with decisions to comply with I.D.F. defence instructions regarding behaviour during missile attacks. In addition, the study examined the relationship between attitudes towards the Iron Dome technology and emotions, risk perceptions, and the decision to comply with I.D.F. defence instructions. The results indicate that stronger positive opinions towards Iron Dome were correlated with lower levels of fear and anger, and beliefs that participant’s chances of being injured by a missile were lower than they had been during previous military operation. In addition, better compliance with I.D.F. defence instructions correlated with being more fearful, angrier at Hamas, living closer to Gaza Strip, and having more positive opinions about Iron Dome. The findings also indicate gender differences with respect to factors correlated with risk perceptions, opinions regarding Iron Dome, and precautionary actions during attacks.  相似文献   
662.
This paper is intended to complement the existing literature on civil wars. First, it presents a simple theoretical model of conflict that defines a two‐sector economy. In a contested sector, two agents struggle to appropriate the maximum possible fraction of a contestable output. In an uncontested sector, they hold secure property rights over the production of some goods. Agents split their resource endowment between ‘butter’, ‘guns’ and ‘ice‐cream’. Following the theoretical insights the empirical analysis focuses on the relationship between civil wars and different sectors of the economy. In particular, a panel probit specification shows that the incidence of a civil war decreases in the size of manufacturing sector.  相似文献   
663.
664.
When a penetrator with enhanced lateral effect (PELE) impacts on a reinforced concrete (RC) target, the target is damaged with a large opening. An understanding of how PELE projectile parameters affect the opening dimension, is essential for effective design of the PELE projectile. In this study, under the condition that the impact velocity and target parameters (strength and thickness) were fixed values, the important influence factors of the PELE (jacket wall thickness B, jacket material strength Y1, filling material strength Y2 and angle of monolithic jacketθ) were determined by a dimensional analysis. Tests and simulations of the PELE penetrating the RC target were conducted to analyze the influence of these factors on opening diameter ((D), an equivalent diameter under relative kinetic energy). Based on the test and simulation results, it is found that the influence of these factors B, Y1 andθon the deformation mode of the jacket shows a similar trend:as values of the three factors decrease, the jacket deforms from small bending deformation to large one, and then to curling deformation. This causes the opening diameter to first increase with the decrease of these three factors, and then decreases. It is well known that the bending resistance of the jacket is related to these factors B, Y1 andθ. Therefore, a plastic limit bending moment (M0) of the jacket was quoted to characterize the influence of these factors on the bending deformation of the jacket and the opening diameter of the target. The influence factor Y2 causes (D) to first increase with the increase of Y2, and then decreases. A formula was developed to predict the opening diameter, whose influence parameters were considered in a dimensionless way. It has been shown that the dimensionless opening diameter (D)/d1 is dependent on two dimensionless parameters Q = (d31fc/M0) and G = (fc/Y2), where d1 and fc are the outer diameter of the projectile and the compressive strength of the target, respectively.  相似文献   
665.
无人机集群作战具有作战效能高、战场生存能力强、效费比极高的巨大优势,将给传统防空系统带来巨大挑战.现有反无人机集群技术大多来源于反无人机技术,但反平台与反集群存在显著差异,必须针对无人机集群自身技战术特点,加强对精确/高效/低成本的集群反制技术研究.因此,本文以剖析无人机集群反制技术的可行性为出发点,首先,从反无人机集...  相似文献   
666.
郝英好 《国防科技》2021,42(1):37-42
打击链是分析武器和系统等作战要素有效性的一种方法.针对当前智能武器概念缺乏一致定义的问题,本文提出了基于打击链作战方式的智能武器判定方法.针对智能武器认定困难引发的军控措施争论,分析了智能武器两方面的失控风险:人失去对自主武器的控制权与自主武器本身存在不可控因素和缺陷;以及智能武器的问责困境:如何在指挥者、编程者与智能...  相似文献   
667.
针对目前常用的维修装备数量预测方法存在的不足,以装备维修任务需求分析模型为输入,建立装备维修任务和维修装备数量之间的解析关系模型,从而计算出维修装备的数量。该方法充分考虑了任务需求对维修装备发展的牵引作用,为确定维修装备数量提供了新的途径。  相似文献   
668.
小波分析是当前信号、信息获取与处理领域(尤其是故障诊断分析与检测技术)中一个十分活跃且迅速发展的新领域,是当今国际研究热点,它同时具有理论深刻和应用十分广泛的双重意义。基于小波分析对网络协议进行指纹识别研究,利用小波变换把原始信号分解成多频段的信号,对信号进行塔式分解,通过计算处理每一层取得所有的有关Wi信息,提取指纹特征信息,并提出了检测方法和指纹识别系统的体系结构,对解决当今日益突出的网络安全问题进行有益尝试。  相似文献   
669.
简要介绍了目前稀土永磁减振器的研究现状和单质量稀土永磁减振器的结构与工作原理,运用大型有限元软件ANSYS对稀土永磁减振器的工作过程进行数值模拟,分析其在工作过程中的磁通密度、磁力线分布、力学特性以及它们之间的相互关系。研究表明:稀土永磁减振器具有较好的非线性减振效果;ANSYS在模拟稀土永磁减振器工作过程时,能形象直观的反映其在工作过程中的各种特性参数。  相似文献   
670.
根据汽油燃烧有可能生成复杂的多环芳烃的特点,对火场残留物中可能存在的微量汽油成分进行了提纯,并利用紫外分光光度计对样品进行分析,通过分析总结实验得出的数据及图谱,可以证明紫外光谱法分析火场残留物中可能存在的汽油成分是一种快速有效的鉴定分析方法。  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