全文获取类型
收费全文 | 1524篇 |
免费 | 296篇 |
国内免费 | 460篇 |
专业分类
航空 | 674篇 |
航天技术 | 516篇 |
综合类 | 114篇 |
航天 | 976篇 |
出版年
2024年 | 14篇 |
2023年 | 47篇 |
2022年 | 59篇 |
2021年 | 97篇 |
2020年 | 67篇 |
2019年 | 108篇 |
2018年 | 116篇 |
2017年 | 98篇 |
2016年 | 100篇 |
2015年 | 119篇 |
2014年 | 200篇 |
2013年 | 129篇 |
2012年 | 156篇 |
2011年 | 118篇 |
2010年 | 113篇 |
2009年 | 107篇 |
2008年 | 88篇 |
2007年 | 79篇 |
2006年 | 63篇 |
2005年 | 59篇 |
2004年 | 35篇 |
2003年 | 53篇 |
2002年 | 40篇 |
2001年 | 29篇 |
2000年 | 28篇 |
1999年 | 22篇 |
1998年 | 20篇 |
1997年 | 13篇 |
1996年 | 12篇 |
1995年 | 12篇 |
1994年 | 13篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 16篇 |
排序方式: 共有2280条查询结果,搜索用时 15 毫秒
921.
对柔性梁的振动主动控制进行了研究.主动控制策略采用独立模态空间控制,模态控制律采用离散变结构控制律;给出了从实际测量中提取模态坐标和将模态控制力转换成实际控制力的方法,并给出了离散切换面和离散变结构模态控制律的确定方法.最后结合算例,对文中所给控制方法的有效性进行了验证. 相似文献
922.
本文通过对初步设计阶段中航天飞机立尾气动布局原则的讨论和现有航天飞机立尾气动布局型式(包括方案)的分析,明确了航天飞机立尾气动布局可能的三种模式和改进航天飞机横侧向气动特性的主要措施等问题。这些结果对航天飞机气动布局和外形初步设计有直接参考价值。 相似文献
923.
空间物体的若干法律问题研究 总被引:2,自引:0,他引:2
高国柱 《中国民航学院学报》2006,24(5):51-55
对空间物体的概念、特征进行了研究,探讨了空间物体与空间碎片以及航空航天物体之间的关系,从而明确了空间物体的内涵与外延。此外,对空间物体发射国和空间物体的登记制度进行了研究,提出区分不同情况确定发射国和通过协议划分损害赔偿责任的创新观点。 相似文献
924.
经济空间趋势面模型的建立与分析 总被引:1,自引:0,他引:1
为了形象直观的了解经济空间的发展状况,介绍了如何对经济数据实现基于格网的建模方法,并通过Surfer软件进行空间数据插值后建立空问趋势面。利用此方法绘制了江苏省人均GNP、第一产业、第二产业、第三产业、GNP、农业人口率等二维和三维趋势面图,通过它对江苏省的经济布局及其趋势状况进行了实证研究。结果表明江苏省经济发展存在着明显的梯度特征,三大区域之间的经济差距目前呈显著的扩大趋势。 相似文献
925.
926.
Reconstructed attitude data for the Hipparcos mission as obtained in the final stages of the data analysis for the published
catalogue is used to derive detailed information on the dynamics of the satellite. Most elements of the inertia tensor of
the satellite could be calibrated from the observed acceleration data, which are also used to reconstruct torques due to solar
radiation and gravity gradient, and the magnetic moment of the satellite and it's interaction with the magnetic field surounding
the Earth. The effects of the oblateness of the Earth on the gravity gradient are evaluated and shown to be negligable. The
magnetic field model includes both the `main' and the `disturbance' fields. The remaining systematic effects in residual torques
are most likely attributed to variations in the magnetic field that are local and are beyond the models used to describe it.
The angular momentum vector for one of the gyros was reconstructed from the torque it asserted on the satellite while it was
running in redundant mode.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
927.
928.
929.
The large commercial aircraft, developed today by manufacturers, are characterized by a high flexibility which results in a stronger interaction between the flight control system and the structural modes. The active control of the first elastic modes is needed to meet the performance requirements. This paper proposes an identification methodology of a flexible aircraft from flight test data, which is appropriate for control law design with modern control techniques (LQG, H2/H∞). In a first step a procedure based on Eigensystem Realization Algorithm (ERA) is used to determine an initial aeroelastic model which is subsequently combined with a linearized rigid-body model and optimized by an output-error minimization method. Two application examples show the good performances of the approach. 相似文献
930.
The Geospace Double Star Project (DSP) consists of two small satellites operating in the near-earth equatorial and polar regions, respectively. The goals of DSP are: (1) to provide high-resolution field, particle, and wave measurements in some important near-earth active regions which have not been covered by current ISTP missions, such as the near-earth plasma sheet and its boundary layer, the ring current, the radiation belts, the dayside magnetopause boundary layer, and the polar region; (2) to investigate the trigger mechanisms of magnetic storms, magnetospheric substorms, and magnetospheric particle events,as well as the responses of geospace storms to solar activities and interplanetary disturbances; (3) to set up the models describing the spatial and temporal variations of the near-earth space environment.To realize the above goals, the equatorial satellite TC-1 and the polar satellite TC-2 will accommodate, respectively, eight instruments on board. TC-1was launched successfully in December 2003 while the polar satellite (TC-2)will be launched in July 2004. The orbit of the equatorial satellite TC-1 consists of a perigee at 550 km, an apogee at 60 000 km, and an inclination of about 28.5; while the orbit of the polar satellite will have a perigee of 700 km, an apogee of 40 000 km, and an inclination of about 90. The two satellites will take coordinated measurements with Cluster Ⅱ and will first form a "six-point exploration" in geospace.The operational status of TC-1 are introduced in this paper. 相似文献