全文获取类型
收费全文 | 432篇 |
免费 | 75篇 |
国内免费 | 96篇 |
专业分类
航空 | 275篇 |
航天技术 | 128篇 |
综合类 | 53篇 |
航天 | 147篇 |
出版年
2024年 | 3篇 |
2023年 | 8篇 |
2022年 | 15篇 |
2021年 | 14篇 |
2020年 | 25篇 |
2019年 | 15篇 |
2018年 | 13篇 |
2017年 | 12篇 |
2016年 | 9篇 |
2015年 | 24篇 |
2014年 | 42篇 |
2013年 | 42篇 |
2012年 | 31篇 |
2011年 | 51篇 |
2010年 | 46篇 |
2009年 | 45篇 |
2008年 | 36篇 |
2007年 | 29篇 |
2006年 | 23篇 |
2005年 | 15篇 |
2004年 | 18篇 |
2003年 | 11篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 11篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有603条查询结果,搜索用时 109 毫秒
81.
82.
认知风格是学习者习惯性的认知特点,它相对固定。不同学习者往往具有不同的认知特点。在二语习得理论中,认知风格被视为学习者个体内在因素之一。研究认知风格对于教与学都具有重要的意义。 相似文献
83.
84.
85.
日本是辽宁重要的经贸国家之一,在辽宁对外经贸中起着极为重要的作用。研究对日经贸关系及其对辽宁经济的影响,有利于辽宁区域经济的发展。从辽宁与日本的经贸关系出发,运用相关的统计数据,建立回归模型来实证分析辽宁与日贸易及吸收日资对辽宁经济所产生的推动效应,最后阐述了辽宁与日本经贸关系的前景,从而对辽宁与日本的经贸关系有更深刻地认识。 相似文献
86.
87.
对变压器冷却风机用外转子异步电机的主要工艺问题进行了探讨分析,并提出了解决措施,使外转子异步电机有更广阔的应用领域. 相似文献
88.
V. A. Sadovnichiy A. M. Amelyushkin V. Angelopoulos V. V. Bengin V. V. Bogomolov G. K. Garipov E. S. Gorbovskoy B. Grossan P. A. Klimov B. A. Khrenov J. Lee V. M. Lipunov G. W. Na M. I. Panasyuk I. H. Park V. L. Petrov C. T. Russell S. I. Svertilov E. A. Sigaeva G. F. Smoot Yu. Shprits N. N. Vedenkin I. V. Yashin 《Cosmic Research》2013,51(6):427-433
At present, the Institute of Nuclear Physics of Moscow State University, in cooperation with other organizations, is preparing space experiments onboard the Lomonosov satellite. The main goal of this mission is to study extreme astrophysical phenomena such as cosmic gamma-ray bursts and ultra-high-energy cosmic rays. These phenomena are associated with the processes occurring in the early universe in very distant astrophysical objects, therefore, they can provide information on the first stages of the evolution of the universe. This paper considers the main characteristics of the scientific equipment aboard the Lomonosov satellite. 相似文献
89.
This paper studies a nonlinear robust control algorithm of the electro-hydraulic load simulator (EHLS). The tracking performance of the EHLS is mainly limited by the actuator's motion disturbance, flow nonlinearity, and friction, etc. The developed controller is developed based on the nonlinear motion loading model. The problems of the actuator's disturbance and flow nonlinearity are considered. To address the friction problem, the friction model of the loading motor is identified experimentally. The friction disturbance is compensated using the obtained friction model. Therefore, this paper considers the main three factors comprehensively. The developed algorithm is easy to apply since the controller can be obtained just with one step back-stepping design. The stability of the developed algorithm is proven via Lyapunov analysis. Both co-simulation and experiments are performed to verify the effectiveness of this method. 相似文献
90.
A system impulse response with low sidelobes is critical in synthetic aperture radar(SAR) images because sidelobes contribute to noise and interfere with nearby scatterers. However,the conventional tricks of sidelobe suppression are unable to be exactly applied to the case of spaceborne sliding spotlight SAR due to great azimuth shifts in both time and frequency domains. In this paper, an extended chirp scaling algorithm is presented for spaceborne sliding spotlight SAR data imaging. The proposed algorithm firstly uses the spectral analysis(SPECAN) technique to avoid the azimuth spectrum folding effect and then employs the chirp scaling(CS) algorithm to achieve data focusing, i.e., the so-called two-step approach. To suppress the sidelobe level, an efficient strategy for the azimuth spectral weighting which only involves matrix multiplications and short fast Fourier transformations(FFTs) is proposed, which is a post-process executed on the focused SAR image and particularly simple to be implemented. The SAR image processed by the proposed extended CS algorithm is very precise and perfectly phase-preserving. In the end, computer simulation results verify the analysis and confirm the validity of the proposed algorithm. 相似文献