全文获取类型
收费全文 | 268篇 |
免费 | 33篇 |
国内免费 | 109篇 |
专业分类
航空 | 169篇 |
航天技术 | 91篇 |
综合类 | 34篇 |
航天 | 116篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 15篇 |
2020年 | 6篇 |
2019年 | 11篇 |
2018年 | 12篇 |
2017年 | 10篇 |
2016年 | 13篇 |
2015年 | 10篇 |
2014年 | 15篇 |
2013年 | 20篇 |
2012年 | 18篇 |
2011年 | 21篇 |
2010年 | 28篇 |
2009年 | 17篇 |
2008年 | 18篇 |
2007年 | 18篇 |
2006年 | 19篇 |
2005年 | 17篇 |
2004年 | 11篇 |
2003年 | 7篇 |
2002年 | 13篇 |
2001年 | 15篇 |
2000年 | 12篇 |
1999年 | 8篇 |
1998年 | 8篇 |
1997年 | 12篇 |
1996年 | 9篇 |
1995年 | 11篇 |
1994年 | 9篇 |
1993年 | 2篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
排序方式: 共有410条查询结果,搜索用时 375 毫秒
51.
52.
计算气动光学是采用数值计算的方法研究高速空气动力流场对光波传输和光学成像影响的一门交叉学科,在红外成像制导设计等工程应用中发挥着重要的作用。总结了计算气动光学研究的三种基本计算方法,包括基于CFD简化方法的光学统计估算、基于RANS流场的计算和基于LES/DNS瞬态流场的计算,对这三种计算方法的基本理论、计算过程进行了介绍,综述了新近的一些计算气动光学研究进展,最后指出了未来的研究重点和方向。 相似文献
53.
54.
Balázs Zábori Attila Hirn Pál Bencze 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The main point of the paper is to use the simultaneous measurements of the energetic particle flux by TriTel and those of electron density by a Langmuir probe to study the question of to what extent solar electromagnetic and corpuscular radiation (galactic cosmic rays, particle precipitation from the radiation belts) are responsible for the ionization of the atmosphere. The electron density measured by the Langmuir probe is the sum of the ionization produced by the solar electromagnetic radiation and that due to the corpuscular radiation. The ionization produced by the solar electromagnetic radiation may be computed. The flux of energetic particles in an energy range may be determined by taking the difference between the threshold energy of the TriTel telescopes and the energy corresponding to the local cut-off rigidity. As the ESEO satellite will have a quasi-polar and circular orbit, the cut-off rigidity will change from low to high latitudes, thus enabling the assignment of different energy bands for the telescopes. Thus, it will be possible to determine which energy bands of particle produce ionization at different latitudes. 相似文献
55.
S. Watari 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,42(9):1445-1449
Progress in information technology has enabled to collecting data in near real-time. This significantly improves our ability to monitor space weather conditions. We deliver information on near real-time space weather conditions via the internet. We have started two collaborations with space weather users. One is a measurement of geomagnetically induced current (GIC) of power grids in collaboration with a Japanese power company. The other concerns radiation hazards for aircrews. The radiation exposure level for aircrews was been determined by the Japanese government by the end of 2005. The proposed upper limit is 5 mSV a year. We are actively seeking ways to contribute to this subject. Our activities at the Japanese space weather center are reported in this paper. 相似文献
56.
57.
Leakage due to wear is one of the main failure modes of aero-hydraulic spool valves. This paper established a practical coupling wear model for aero-hydraulic spool valves based on dynamic system modelling theory. Firstly, the experiment for wear mechanism verification proved that adhesive wear and abrasive wear did coexist during the working process of spool valves. Sec-ondly coupling behavior of each wear mechanism was characterized by analyzing actual time-variation of model parameters during wear evolution process. Meanwhile, Archard model and three-body abrasive wear model were utilized for adhesive wear and abrasive wear, respectively. Furthermore, their coupling wear model was established by calculating the actual wear volume. Finally, from the result of formal test, all the required parameters for our model were obtained. The relative error between model prediction and data of pre-test was also presented to verify the accuracy of model, which demonstrated that our model was useful for providing accurate prediction of spool valve’s wear life. 相似文献
58.
将nc-Si:H薄膜进行等离子和高温氧化处理,测量了样品的氢,氧含量,Raman谱,红外吸收谱,光致发光(PL),结果表明两种氧化方式都将氧掺入薄膜中,但不同处理方式氧在薄膜中的键合形式不同Raman谱表明氧化处理对薄膜中晶粒大小及晶态比没有影响,用晶粒-表面模型对氧化引起的光致发光(PL)蓝移进行了解释。 相似文献
59.
J.-C. Liou N.L. Johnson 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
The intentional breakup of Fengyun-1C on 11 January 2007 created the most severe orbital debris cloud in history. The altitude where the event occurred was probably the worst location for a major breakup in the low Earth orbit (LEO) region, since it was already highly populated with operational satellites and debris generated from previous breakups. The addition of so many fragments not only poses a realistic threat to operational satellites in the region, but also increases the instability (i.e., collision cascade effect) of the debris population there. 相似文献
60.
We study kinetic excitation mechanisms for high-frequency dispersive Alfvén waves in the solar corona, solar wind, and Earth's
magnetosphere. The ion-cyclotron and Cherenkov kinetic effects are important for these waves which we call the ion-cyclotron
kinetic Alfvén waves (ICKAWs). Ion beams, anisotropic particles distributions and currents provide free energy for the excitation
of ICKAWs in space plasmas. As particular examples we consider ICKAW instabilities in the coronal magnetic reconnection events,
in the fast solar wind, and in the Earth's magnetopause. Energy conversion and transport initiated by ICKAW instabilities
is significant for the whole dynamics of Sun-Earth connection chain, and observations of ICKAW activity could provide a diagnostic/predictive
tool in the space environment research.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献