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   960篇
  免费   289篇
  国内免费   57篇
  1306篇
  2022年   17篇
  2021年   22篇
  2020年   17篇
  2019年   14篇
  2018年   11篇
  2017年   57篇
  2016年   51篇
  2015年   38篇
  2014年   60篇
  2013年   120篇
  2012年   126篇
  2011年   135篇
  2010年   46篇
  2009年   36篇
  2008年   42篇
  2007年   64篇
  2006年   65篇
  2005年   78篇
  2004年   63篇
  2003年   59篇
  2002年   30篇
  2001年   38篇
  2000年   34篇
  1999年   20篇
  1998年   5篇
  1997年   10篇
  1996年   10篇
  1995年   4篇
  1994年   4篇
  1993年   3篇
  1992年   7篇
  1991年   6篇
  1990年   9篇
  1989年   4篇
  1987年   1篇
排序方式: 共有1306条查询结果,搜索用时 15 毫秒
101.
利用ADAMS软件中的参数化分析工具,采用设计变量和局部模型重建的方法,实现了特种斜盘发动机斜盘倾角、后球心分布圆半径和导槽形式的参数化,建立了特种斜盘发动机参数化虚拟样机,并进而从设计研究、试验研究和初步优化分析等三个方面,对特种斜盘发动机进行了较为详细和全面的参数化分析.  相似文献   
102.
用有限时间热力学的方法分析具有热阻、热漏、内不可逆性的定常流联合卡诺型热机循环.导出了在傅立叶导热定律下联合循环功率、效率和生态学指标的性能,并进行优化;得到功率、效率和生态学指标之间的优化关系,并由数值计算分析了功率、效率和循环熵产率之间的关系.所得的结果表明,最大生态学指标下的效率十分接近于联合循环可以达到的最大效率;相应的熵产率也要低于以输出功率为优化目标时的熵产率.  相似文献   
103.
基于分布式哈希表(DHT)的P2P查找经常受到在底层网络中路由时无必要的路径长度增加的影响.另外,DHT在处理复制方面也有一定的缺陷.文中探讨了解决这些问题的方法.对使用Bloom filters作为资源路由的方法做了简要回顾,并较为详细地阐述了在资源分散的覆盖网络中使用距离加权Bloom filter的网络路由算法.对该算法进行了仿真测试,证明了其有效性.  相似文献   
104.
复杂背景下机载雷达目标探测的模型分析   总被引:2,自引:0,他引:2  
考虑机载雷达目标探测受到复杂环境因素的影响,建立复杂背景条件下机载雷达目标探测的系统模型.利用此模型提出一个机载雷达目标探测的效能指标.在效能仿真的基础上,给出复杂背景条件下诸要素对机载雷达目标探测的定量影响.仿真结果表明了该模型的正确性和有效性.  相似文献   
105.
This paper systematically analyzes the causes of the escalation of violence during the initial stages of the Jeju Island Rebellion and the failure of South Korean counterinsurgency operations. It is argued that four interrelated factors provided the conditions for armed insurgency in the small island of Jeju: inter-agency tension between the Korean National Police (KNP) and the Korean Constabulary; the mainlanders' misinterpretation of the insurgency; the effect of systematic police brutality; and the role of youth groups. Consequently, two counterinsurgency lessons will be drawn from this study: that inter-agency cooperation and coordination at the tactical level between security branches and the incorporation of local population at the micro-level is essential in conducting efficient and effective counterinsurgency operations.  相似文献   
106.
The Pakistani Taliban, factionalized into some 40 groups, form a decentralized insurgent movement, often characterized by infighting, divergent motivations, and a shifting web of alliances. The Pakistani Taliban remain little understood because most scholars have avoided a serious treatment of the insurgent movement and instead focused on analyzing the geopolitics of the region and Pakistan's ‘double game’. This article seeks to fill this gap by dissecting the movement through selected theories of organization and mobilization. First, I explain the various dimensions of the conflict and the origins of the insurgency. Next, I discuss the Pakistani Taliban's political organization, categorizing it as composed of various warlord regimes. I further list the Taliban's component groups and numerical strength and chart the leadership structure. Lastly, I analyze insurgent recruitment strategies, accounting for the role of selective incentives, coercion, and genuine grievances.  相似文献   
107.
Croatia's successful bid for independence was one of the defining moments of the immediate post-Cold War period. Nevertheless, the means that Croatia used to obtain independence remains relatively unexamined by academics. This article focuses on the early period of Croatia's bid for secession, and specifically the role that Yugoslavia's policy of Total National Defence played in facilitating its independence. Unlike in Slovenia, where the legacies of Total National Defence facilitated Slovenia's bid for secession, in Croatia the decision of its political leaders meant that the country largely neglected its positive legacies, resulting in a protracted four-year struggle.  相似文献   
108.
ABSTRACT

Sectarian militants have for years launched attacks from Pakistan across the border to Iran. Finding sanctuary in a neighbouring country can make the difference between success and failure for militants. Conventional wisdom holds that a lasting transnational militancy challenge would typically create serious interstate conflict. Militancy has triggered armed encounters between Iran and Pakistan. This article argues that despite some tension militancy has resulted in deeper cooperation in the ambivalent dyad. Both states’ overarching security concerns, having exhausted other options, the believed involvement of third-party states, and economic potential, have moderately alleviated negative pressure caused by militancy.  相似文献   
109.
This paper, intended to stimulate debate, suggests that we are at a turning point in the history of the UK military aerospace industry. It argues that there is urgent need for a fresh vision as to how the UK military aerospace industry can both prosper and make its maximum contribution to the defence of Britain. Further, the resulting plans and policies must emphasise the robustness of defence capabilities in a future in which the only thing we can be certain is that it will be very different from the present – especially whenever defence most matters.  相似文献   
110.
Stay-behind networks in France were set up starting in 1948 and were aimed at responding to the possibility of a Soviet armed attack into Western Europe. Participants were identified, and arms and explosives cached, to be activated in case of hostilities. This activity became folded into a multilateral effort under the Allied Coordination Committee (ACC) of NATO. In France, the network was run as a highly compartmented activity under the French external intelligence service (DGSE). As the Soviet threat receded, the stay-behind activity became more and more dormant, and in 1990 it was quietly disbanded, immediately after the P-2 scandal broke in Italy.  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