全文获取类型
收费全文 | 357篇 |
免费 | 33篇 |
国内免费 | 35篇 |
专业分类
航空 | 204篇 |
航天技术 | 87篇 |
综合类 | 27篇 |
航天 | 107篇 |
出版年
2022年 | 3篇 |
2021年 | 19篇 |
2020年 | 7篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 8篇 |
2015年 | 9篇 |
2014年 | 25篇 |
2013年 | 14篇 |
2012年 | 6篇 |
2011年 | 34篇 |
2010年 | 6篇 |
2009年 | 17篇 |
2008年 | 9篇 |
2007年 | 6篇 |
2006年 | 7篇 |
2005年 | 19篇 |
2004年 | 15篇 |
2003年 | 35篇 |
2002年 | 41篇 |
2001年 | 12篇 |
2000年 | 6篇 |
1999年 | 10篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1991年 | 3篇 |
1989年 | 8篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 3篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 6篇 |
1971年 | 1篇 |
1970年 | 3篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 4篇 |
1966年 | 2篇 |
1963年 | 2篇 |
1962年 | 1篇 |
排序方式: 共有425条查询结果,搜索用时 17 毫秒
31.
Electrodynamic tethers have been recently proposed for satellite and rocket upper stage deorbiting to mitigate the debris problem at Low Earth Orbits (LEOs). The deorbiting performance of several electrodynamic tethers, where the electron collection from the ionosphere is obtained with either simple bare wires or bare wires terminated with conducting spherical collectors, was analyzed and compared. Our results indicate that the use of the spherical collectors at the positive termination of the system significantly enhances the deorbiting capabilities of the electrodynamic bare tethers. 相似文献
32.
33.
HAJIF-Ⅱ是中国航空研究院领导研制的航空结构动力分析系统。它可以进行结构的固有动力特性计算,以及带主动控制系统的飞机颤振计算和突风响应计算。它具有31条固定流程、2600条FORTRAN语句。允许使用99个原级子结构,每个子结构的自由度数可达7000。颤振计算和突风响应计算中,可以使用50个形态。非定常空气动力计算的分块数可达300个。在刚度矩阵和质量矩阵的管理上,采用超元矩阵方法做“宏观处理”,并用有效列方法做“微观处理”,发展了新的同时迭代算法,以提高实特征值计算的效率。设计了比较完整的形态综合法计算程序,除固定界面法和自由界面法之外,还发展了分级综合和逐步综合的新方法。非定常空气动力计算方面,引入了用曲线拟合方法把谐振荡空气动力转入拉氏平面的技术。用本系统计算了一批典型的结构,取得了良好结果。 相似文献
34.
介绍了模拟板由小模型到大模型的研制过程,着重讨论了模拟板小模型与大模型在流场总压恢复系数、周向不均匀度、低压区范围等方面的相关性问题。研究结果表明由小模型到大模型的研制方案是正确可行的。 相似文献
35.
Solar sails have much attracted the interest of the scientific community as an advanced low-thrust propulsion means capable of promoting the reduction of mission costs and the feasibility of missions that are not practically accessible via conventional propulsion because of their large ΔV requirements. To reduce the overall flight time, a given mission is usually analyzed in the framework of a minimum time control problem, with the employment of a continuous steering law. The aim of this paper is to investigate the performance achievable with a piecewise-constant steering law whose aim is to substantially reduce the complex task of reorienting the sail over the whole mission. Unlike previous studies based on direct approaches, here we use an indirect method to optimally select the sail angle within a set of prescribed values. The corresponding steering law translates the results available for continuous controls to the discrete case, and is able of producing trajectories that are competitive in performance with the optimum variable direction program. 相似文献
36.
37.
In this review we present the current status of line-profile-variation studies of β Cep stars. Such studies have been performed
for 26 bright members of this class of pulsating stars in the past 25 years. We describe all these currently available data
and summarize the interpretations based on them in terms of the excited pulsation modes.
We emphasize that line-profile variations offer a much more detailed picture of the pulsational behaviour of pulsating stars
compared to ground-based photometric data. The latter, however, remain necessary to unravel the often complex frequency pattern
and to achieve unambiguous mode identification for multiperiodic β Cep stars and also to derive the pulsational properties
of the faint members of the class.
We highlight the statistical properties of the sample of 26 stars for which accurate spectroscopic studies are available and
point out some future prospects.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
38.
利用分布粘帖在矩形机翼上下两面的压电驱动器,探索使用该类结构提高飞行器横滚能力的可能性。通过风洞模型设计、材料性能测试、模型固有特性测试、压电柔度矩阵测试等试验项目,保证了有限元模型的计算精度,最终通过模型的风洞试验验证了利用气动弹性效应,获得了附加升力与横滚力矩的方案。该原理性试验说明利用分布式压电驱动器改善横滚性能是可行的。 相似文献
39.
S. Hayakawa J. Kuijpers J. Kleczek Boris Valnicek L. Kresak H. R. De Ruiter 《Space Science Reviews》1991,57(1-2):189-192
40.
This paper discusses the generation, stability, and control of artificial equilibrium points for a solar balloon spacecraft in the α Centauri A and B binary star system. The continuous propulsive acceleration provided by a solar balloon is shown to be able to modify the position of the (classical) Lagrangian equilibrium points of the three-body system on a locus whose geometrical form is known analytically. A linear stability analysis reveals that the new generated equilibrium points are usually unstable, but part of them can be stabilized with a simple feedback control logic. 相似文献