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   2989篇
  免费   395篇
  国内免费   176篇
  2024年   3篇
  2023年   7篇
  2022年   21篇
  2021年   36篇
  2020年   36篇
  2019年   68篇
  2018年   58篇
  2017年   115篇
  2016年   113篇
  2015年   66篇
  2014年   271篇
  2013年   324篇
  2012年   183篇
  2011年   245篇
  2010年   212篇
  2009年   231篇
  2008年   187篇
  2007年   215篇
  2006年   176篇
  2005年   178篇
  2004年   161篇
  2003年   134篇
  2002年   87篇
  2001年   88篇
  2000年   43篇
  1999年   45篇
  1998年   32篇
  1997年   30篇
  1996年   31篇
  1995年   25篇
  1994年   33篇
  1993年   18篇
  1992年   21篇
  1991年   16篇
  1990年   24篇
  1989年   14篇
  1988年   10篇
  1987年   2篇
  1975年   1篇
排序方式: 共有3560条查询结果,搜索用时 46 毫秒
51.
基于风险理论提出一种面向不同目标探测任务的传感器调度方法。将主动传感器辐射被截获风险和目标探测风险结合起来,建立一般目标探测框架下的传感器最小风险调度模型。分目标跟踪、目标识别和目标威胁等级评估三种情况将传感器最小风险调度模型具体化,给出不同情况下目标探测风险值的计算方法。针对模型的求解提出一种基于混沌思想、反向学习和双向轮盘赌的改进人工蜂群算法。通过仿真实验证明了模型的可行性和算法的有效性。  相似文献   
52.
鲁赢  伏涛  张志勇  林文浩 《国防科技》2020,41(3):127-130
随着智能技术的发展,人类已逐步迈入智能时代,而智能时代催生了军事训练变革。本文从智能技术影响军事训练典型领域的角度,分析了智能时代背景下,以大数据和人工智能为核心的智能技术,如何影响军事训练的理念、内容、方式及管理,并催生了这些领域的变革。研究表明,智能时代发展背景下,军事训练理念将更加先进,训练内容更加融合,训练方式更加有效,训练管理更加精准。  相似文献   
53.
《防务技术》2020,16(1):201-207
Three different kinds of PELE (the penetrator with lateral efficiency) were launched by ballistic artillery to impact the multi-layer spaced metal target plates. The impact velocities of the projectiles were measured by the velocity measuring system. The damage degree and process of each layer of target plate impacted by the three kinds of projectiles were analyzed. The experimental results show that all the three kinds of projectiles have the effect of expanding holes on the multi-layer spaced metal target plates. For the normal structure PELE(without layered) with tungsten alloy jacket and the radial layered PELE with tungsten alloy jacket, the diameters of holes on the second layer of plates are 3.36 times and 3.76 times of the diameter of the projectile, respectively. For radial layered PELE with W/Zr-based amorphous composite jacket, due to the large number of tungsten wires dispersed after the impact, the diameter of the holes on the four-layer spaced plates can reach 2.4 times, 3.04 times, 5.36 times and 2.68 times of the diameter of the projectile. Besides, the normal structure PELE with tungsten alloy jacket and the radial layered PELE whit tungsten alloy jacket formed a large number of fragments impact marks on the third target plate. Although the number of fragments penetrating the third target plate is not as large as that of the normal structure PELE, the area of dispersion of fragments impact craters on the third target plate is larger by the radial layered PELE. The radial layered PELE with W/Zr-based amorphous composite jacket released a lot of heat energy due to the impact of the matrix material, and formed a large area of ablation marks on the last three target plates.  相似文献   
54.
The aim of this paper is to investigate the determinants of international arms transfers in a gravity model framework. By distinguishing between the decision to export arms (extensive margin) and the value of the arms exported (intensive margin), while also considering its interdependence, is what differentiates this paper from previous research. A theoretically justified gravity model of trade augmented with political and security motives is estimated using a two-stage panel data approach for 104 exporting countries over the period from 1950 to 2007. In addition to the usual gravity variables related to the economic mass of the trading countries and the trade cost factors, the model is extended with political and security factors. The level of democracy in both trading partners, political differences between trading partners and voting similarity with the United States in the UN General Assembly of the countries engaged in trade are the main political factors, whereas the existence of conflicts, military pacts, and embargoes are taken as security motives. The key result indicates that both political and security motives are an important determinant of an arms trade, but their effects on the extensive margin of exports (the decision to order a transfer) differs from their effect on the intensive margin (average value of exports). Moreover, the relative importance of the factors under study has changed since 1989. In the post-cold war period, countries that are less democratic are more likely to export arms, military pacts are less relevant and embargoes play a role.  相似文献   
55.
Buying off the shelf procurements (OTS) has become an important part of the national acquisition strategy in several countries, and this paper seeks to bring empirical evidence on OTS as the preferred acquisition strategy by use of data from 2015 to 2022 investment portfolio of the Norwegian Armed Forces. We develop definitions for three categories of procurement – OTS, modified OTS and development projects – as well as a method to classify projects into these categories. Our first finding is that the characteristics of OTS projects correspond to modified OTS and development projects. Our second finding indicates that OTS projects perform better when it comes to the completion of projects according to the initial schedule, compared to development projects.  相似文献   
56.
This paper explores the notion that US efforts to evade the political costs of war paradoxically contribute to the subsequent exacerbation of costs over time. Leaders seek to purchase political capital in the short term by limiting the costs and requirements of military operations, but in doing so cause strategic and political liabilities to mount in the long run. While identification of such behaviour is not new, insufficient attention has been devoted to explaining its causes, dynamics, and manifestations in relation to key decisions on and in war. Evidence derived from studies of recent American discretionary campaigns is analysed to advance an argument with respect to this pattern of self-defeating strategic behaviour.  相似文献   
57.
The article outlines the essential role of free play elements in various types of exercises for the development of in-depth and practical military professionalism. It thereafter argues why such use of free play contradicts the military science founded Russian Way of War.  相似文献   
58.
目标宽带RCS预估算法一直是计算电磁学的一个研究热点,本文分别研究了渐近波形估计技术(AWE)与最佳一致逼近技术在宽频带RCS预估领域内的应用。首先,介绍了传统矩量法计算RCS的原理,并分析了两种快速算法的计算过程。然后,采用这两种技术,分别计算了简易飞机模型的RCS值,并对这两种方法进行比较。计算结果表明相比传统的矩量法,这两种方法在不影响精度的前提下大大提高了计算效率。同时,相比渐近波形估计技术,最佳一致逼近技术在节省内存,节约时间方面更具优势。最后,采用最佳一致逼近理论,结合电磁计算软件,实现较大尺寸目标的宽频带RCS的计算。  相似文献   
59.
ABSTRACT

In the decades following independence from Spain, ‘civil wars’ ravaged the newly established polities in South America. Former vice-regal capitals inherited a larger portion of the colonial administration and had larger economic resources and a hegemonic project they were able to have permanent and professional armed forces, capable of leading the offensive and giving battle following the European rules of military art. The central hypothesis of this work is that there is a necessary relationship between the shape of these asymmetrical conflicts, their outcome and the political territorial configuration of each country in post-revolutionary Spanish America. When permanent armies took over from local militias, the capital kept the integrity of its territories and there was a tendency towards political centralization. When this did not happen and the militias managed to find a way to defeat their centralizing enemies, the local powers had an opportunity to renegotiate their participation in the political body, and sought to maintain their independence, which was manifest in federal agreements, otherwise a process of territorial fragmentation began. More than a difference between regular and irregular forces there was one between intermittent, and permanent mobilization.  相似文献   
60.
针对阵列体制雷达,由极大似然估计导出自适应多零点单脉冲测角原理。分析发现迭代步长过大导致双零点单脉冲技术在多目标条件下失效,因此提出加权步长改进角度估计的迭代过程,只需要较少计算量就能实现群内多个目标的精确测角。仿真结果表明:该算法在较高信噪比条件下可以精确测量群内三个目标角度,测角误差约为0.15倍波束宽度;当群目标数较多或者目标相位差接近于0时,算法性能下降明显。  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