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   330篇
  免费   206篇
  国内免费   23篇
  559篇
  2024年   3篇
  2023年   7篇
  2022年   8篇
  2021年   8篇
  2020年   13篇
  2019年   9篇
  2018年   8篇
  2017年   26篇
  2016年   30篇
  2015年   31篇
  2014年   37篇
  2013年   39篇
  2012年   35篇
  2011年   38篇
  2010年   28篇
  2009年   32篇
  2008年   20篇
  2007年   28篇
  2006年   19篇
  2005年   25篇
  2004年   16篇
  2003年   17篇
  2002年   17篇
  2001年   14篇
  2000年   11篇
  1999年   8篇
  1998年   10篇
  1997年   8篇
  1996年   3篇
  1994年   3篇
  1993年   3篇
  1992年   1篇
  1990年   2篇
  1989年   2篇
排序方式: 共有559条查询结果,搜索用时 15 毫秒
381.
This paper explores the hypothesis that both the preexisting quality of democracy in a polity at the onset of conflict and the quality of democracy expected to emerge in the aftermath influence the likelihood of civil war. An empirical investigation of the hypothesis presents a challenge due to concerns of endogeneity and selection: the post-conflict level of democracy is endogenous to the pre-conflict level. Further, for a given time period, either a number of countries have not experienced civil war; or if they did, did not resolve the conflict. We overcome this selection bias by implementing a three-step extension to the Heckman procedure using an unbalanced cross-country panel of 77 countries over the period 1971–2005. Consistent with our hypothesis, we find that a standard deviation improvement in the existing level of democracy reduces the probability of civil war by approximately 9 percentage points and a corresponding improvement in expected post-conflict democratization increases the probability of conflict by approximately 48 percentage points.  相似文献   
382.
In this paper, based on a bidirectional parallel multi-branch feature pyramid network (BPMFPN), a novel one-stage object detector called BPMFPN Det is proposed for real-time detection of ground multi-scale targets by swarm unmanned aerial vehicles (UAVs). First, the bidirectional parallel multi-branch convolution modules are used to construct the feature pyramid to enhance the feature expression abilities of different scale feature layers. Next, the feature pyramid is integrated into the single-stage object detection framework to ensure real-time performance. In order to validate the effectiveness of the proposed algorithm, experiments are conducted on four datasets. For the PASCAL VOC dataset, the proposed algorithm achieves the mean average precision (mAP) of 85.4 on the VOC 2007 test set. With regard to the detection in optical remote sensing (DIOR) dataset, the proposed algorithm achieves 73.9 mAP. For vehicle detection in aerial imagery (VEDAI) dataset, the detection accuracy of small land vehicle (slv) targets reaches 97.4 mAP. For unmanned aerial vehicle detection and tracking (UAVDT) dataset, the proposed BPMFPN Det achieves the mAP of 48.75. Compared with the previous state-of-the-art methods, the results obtained by the proposed algorithm are more competitive. The experimental results demonstrate that the proposed algorithm can effectively solve the problem of real-time detection of ground multi-scale targets in aerial images of swarm UAVs.  相似文献   
383.
利用低时空分辨率的卫星遥感观测进行目标群关联,由于目标群运动状态转变的规律性不好寻找,目标群的精确属性特征难于获取,增加了利用目标属性进行关联的实现难度.考虑到地形特征对目标群运动影响的特点,提出了基于地形栅格分析的多目标关联算法.  相似文献   
384.
为更好地研究高原地区车辆发动机与油料的适应性,针对高原地区特殊的地理环境气候特点,选用10W/40高温重负荷润滑油,对其进行了理化性能分析、350 h台架可靠性试验及高原实际行车试验。结果表明:该型润滑油具有优良的抗氧抗腐性、清净分散性和抗磨性,可满足高原地区大功率、重负荷柴油发动机的用油要求。  相似文献   
385.
C4ISRK是实现未来信息化战场"网络中心战"概念的一组必要的装备系统.着眼于为C4ISRK系统作战运用项目先期概念技术演示提供仿真平台,提出了C4ISRK系统的概念模型,在此基础上重点研究了基于HLA的C4ISRK作战运用仿真系统的总体框架及其设计,为该仿真系统的建立和仿真实施提供了技术支持.  相似文献   
386.
一种改进的遥感图像分形维数提取算法   总被引:5,自引:0,他引:5  
基于离散分形布朗随机场的图像分数维提取方法,在综合分析和实验验证的基础上,提出了一种改进的图像分形维数计算方法。仿真实验证明,该算法相较于原算法计算结果稳定,不同地物的区分能力强,能够应用于遥感图像的地物分类。  相似文献   
387.
六氟异丙醇聚硅氧烷(SXFA)合成方法研究   总被引:2,自引:0,他引:2  
《防化研究》2006,(1):27-29
  相似文献   
388.
The political upheavals that erupted in Kenya after the release of the 2007–8 election results resulted in the death of approximately 1 200 people, as well as the loss of livestock and other valuable property. While the Kenyan government tried to seek solutions to the crisis, the International Criminal Court (ICC) issued warrants for the arrest of top government officials. For its part, the African Union (AU) accused the ICC of racism by targeting only African leaders, and maintained that such practices undermine the rule of equality before the law set forth in Article 27 of the Rome Statute. The AU is therefore advising African countries, including Kenya, to consider withdrawing from the ICC. Will the ICC's intervention into the situation in Kenya bring justice and peace to the country, or will it add to the existing injuries affecting not just the country but the region as well? Through a critical analysis of contemporary scholarly discourse, this article unravels the dilemma of the ICC's intervention and the likely consequences of this action for the people of Kenya and Africa.  相似文献   
389.
复合导线具有一种很有价值的高电导特性:在一定的频率区域,铜包钢复合导线的导电性能明显地高于铜导线.文章给出了这种高电导特性与传输频率及导线结构的关系.  相似文献   
390.
根据部队的实际使用情况,考虑到诸多理论成果的应用现状,提出一种简洁实用的关联识别算法,即根据多信源、多因子的综合判断给出目标的属性。该算法还首次给出了复杂空域的计算方法。  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