全文获取类型
收费全文 | 404篇 |
免费 | 22篇 |
国内免费 | 2篇 |
专业分类
航空 | 227篇 |
航天技术 | 41篇 |
综合类 | 42篇 |
航天 | 118篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 6篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 16篇 |
2013年 | 11篇 |
2012年 | 10篇 |
2011年 | 31篇 |
2010年 | 13篇 |
2009年 | 10篇 |
2008年 | 28篇 |
2007年 | 50篇 |
2006年 | 47篇 |
2005年 | 28篇 |
2004年 | 38篇 |
2003年 | 30篇 |
2002年 | 10篇 |
2001年 | 13篇 |
2000年 | 14篇 |
1999年 | 11篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1989年 | 1篇 |
排序方式: 共有428条查询结果,搜索用时 15 毫秒
421.
袁光华 《西安航空技术高等专科学校学报》2005,23(4):48-51
通过传统型与任务型两个教学班的不同的授课方法,测试结果显示:两班学生在英语学习方面的努力程度相似,但实验后的两次水平测试结果表明实验班学生(任务型)优于控制班(传统型)的学生。 相似文献
422.
体育教育的改革和发展必须融入现代社会与科学技术的发展大潮,以计算机为主体的多媒体教学使传统的体育教学方法发生了巨大变革,体育教育应转变思想,更新观念,探索教育新模式、新方法以适应时代发展的需要。为此,在体育教学中对如何运用多媒体技术改进体育教学方法、指导教学效果等方面进行了探索。 相似文献
423.
三坐标测量机的现状、发展与未来 总被引:8,自引:0,他引:8
叙述了三坐标测量机的基本构成、国内外上产现状、发展与未来。包括测量机的准确度、分类及丰富的软件。尤其对测量机的发展作了较详细的介绍。最后,预测厂测量机的未来。 相似文献
424.
425.
《中国航空学报》2022,35(9):106-116
A real-time ray-based hardware emulator for Unmanned Aerial Vehicle (UAV) communication channels which suits for the Three-Dimensional (3D) dynamic scenarios and considers the movements of both terminals is developed in this paper. The time-variant channel parameters, i.e., ray delay, ray gain, and ray Doppler frequency are precalculated in the host by using the Ray Tracing (RT) method. Meanwhile, RT simulation dramatically increases the number of valid rays. To address the problem of resource limitation and huge computational burden in the implementation, an efficient ray coefficients generation method based on iteration is proposed and implemented. With the advantages of low cost and high flexibility, a Software Defined Radio (SDR) hardware platform is used to emulate the ray-based UAV channels by utilizing the compact architecture including the Time-Division (TD) scheme and Tapped-Delay Line (TDL) for channel convolution. Finally, hardware measurement results demonstrate that the properties of emulated channel, i.e., Power Delay Profile (PDP) and Doppler Power Spectrum Density (DPSD) consist with the simulated ones, which verifies the correctness of hardware implementation. The proposed channel emulator provides an efficient way for optimization, verification, and evaluation of UAV communication systems. 相似文献
426.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2023,71(1):654-675
Space law education has an essential role in the space capacity building of a country because of its importance for human resources development in space law. Comparisons between Canada and China, the European Union and China and the United States of America (USA) and China in space law degree education, course, teaching methodology, institute and practice and communication platform are provided in an attempt to review some issues which exist within the Chinese space law educational system and to seek a better choice for China’s space law education reform. Chinese space law education has achieved noticeable progress over the past two decades. However, it is still limited in comparison to its counterparts in Europe and Northern America. The range of the space law degree education programmes and space-law-related courses is comparatively limited. A gap remains between space law education and practice in China. Chinese space law classes are still dominated by the teacher-centred teaching methodology, although several universities have some new teaching practices. The establishment of seven space law-related research institutes plays an increasingly important role in Chinese space law education, space law and policy research and legal advisory services for the Chinese government and non-governmental sectors. However, these institutes still have a long way to go in comparison with their counterparts in Europe and Northern America. While China has established domestic research platforms for space law communication through international cooperation, it does not provide space law practice platforms for space law education. While international space law does not provide a direct legal foundation for space law education in China, Chinese educational laws can lay a profound legal foundation for Chinese space law education. To promote its national expertise and capacity in space law, based on the three-pillar model and the experiences of its counterparts in North America and Europe, China should adopt a systematic and sustainable regime for its space law education. 相似文献
427.
为增强卫星的自主生存能力,研究了基于卫星轨道软件平台的自主导航计算方法。由星载导航部件获取导航参数,应用数值或解析法进行自主导航计算,以实时获得精确的轨道参数。理论分析和仿真结果表明,读方法正确可行,具有较高的工程应用价值。 相似文献
428.
《中国航空学报》2022,35(9):1-18
As an indispensable component of the emerging 6G networks, Space-Air-Ground Integrated Networks (SAGINs) are envisioned to provide ubiquitous network connectivity and services by integrating satellite networks, aerial networks, and terrestrial networks. In 6G SAGINs, a wide variety of network services with the features of diverse requirements, complex mobility, and multi-dimensional resources will pose great challenges to service provisioning, which urges the development of service-oriented SAGINs. In this paper, we conduct a comprehensive review of 6G SAGINs from a new perspective of service-oriented network. First, we present the requirements of service-oriented networks, and then propose a service-oriented SAGINs management architecture. Two categories of critical technologies are presented and discussed, i.e., heterogeneous resource orchestration technologies and the cloud-edge synergy technologies, which facilitate the interoperability of different network segments and cooperatively orchestrate heterogeneous resources across different domains, according to the service features and requirements. In addition, the potential future research directions are also presented and discussed. 相似文献