全文获取类型
收费全文 | 2571篇 |
免费 | 393篇 |
国内免费 | 213篇 |
出版年
2024年 | 3篇 |
2023年 | 8篇 |
2022年 | 23篇 |
2021年 | 38篇 |
2020年 | 35篇 |
2019年 | 60篇 |
2018年 | 52篇 |
2017年 | 104篇 |
2016年 | 101篇 |
2015年 | 71篇 |
2014年 | 218篇 |
2013年 | 265篇 |
2012年 | 163篇 |
2011年 | 212篇 |
2010年 | 174篇 |
2009年 | 211篇 |
2008年 | 160篇 |
2007年 | 189篇 |
2006年 | 172篇 |
2005年 | 165篇 |
2004年 | 148篇 |
2003年 | 110篇 |
2002年 | 72篇 |
2001年 | 80篇 |
2000年 | 41篇 |
1999年 | 43篇 |
1998年 | 32篇 |
1997年 | 29篇 |
1996年 | 31篇 |
1995年 | 24篇 |
1994年 | 31篇 |
1993年 | 21篇 |
1992年 | 19篇 |
1991年 | 16篇 |
1990年 | 27篇 |
1989年 | 15篇 |
1988年 | 11篇 |
1987年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有3177条查询结果,搜索用时 15 毫秒
941.
针对目前对多波束相控阵天线角跟踪性能测试研究较少的问题,首先分析了多波束相控阵天线的单脉冲和差测角方法,并对波束滑动、波束穿越及信号频率变化对角跟踪性能的影响进行了仿真分析。类比传统的雷达精度校飞试验,提出了基于飞艇的角跟踪性能测试方法,对角跟踪精度及误差范围进行测试,并利用STK软件实现了可视化。仿真分析表明,该方法可以实现对多波束相控阵天线角跟踪性能的评定并具有较高的工程应用价值。 相似文献
942.
Although soft power is now seen as an indispensable foreign policy tool, its efficacy has rarely been put to a rigorous empirical test. Using data from HARMONIOUS MISSIONs 2010, 2011 and 2013, this article seeks to examine the degree to which the soft power engagement missions of the Chinese hospital ship, the Peace Ark, has advanced Chinese interests. Although any conclusions drawn must be considered preliminary, as so little time has passed between the ship's visits and the current analysis, this research indicates that these missions’ impact on advancing Chinese interests was at best limited. Although observations from a single set of cases are unlikely to settle the debate between soft power advocates and detractors, it is hoped that this research will serve as a catalyst to further empirically based research on this topic. 相似文献
943.
Yolanda Sadie 《African Security Review》2015,24(4):450-457
Commitment by the government of the Democratic Republic of Congo to addressing sexual and gender-based violence (SGBV) in the country is reflected in a number of international commitments and national strategies. This article traces the (slow) progress in addressing some of the most important issues relating to SGBV to which the government has committed itself. It argues that unless the underlying gender norms and unequal power relations that form the basis of gender violence, discrimination and inequality in Congolese society are addressed, SGBV will persist. 相似文献
944.
Adrian Roads 《Arms and Armour》2017,14(2):101-137
The Pattern 1838 Musket was initially designed for the rank and file of the British army, it was instead issued to the elite Foot Guards. With arguably the lowest survival rate of any 19th Century British military firearm it is one of the rarest muskets to encounter today. This is its story … 相似文献
945.
946.
947.
948.
949.
950.