全文获取类型
收费全文 | 180篇 |
免费 | 33篇 |
国内免费 | 36篇 |
专业分类
航空 | 99篇 |
航天技术 | 102篇 |
综合类 | 2篇 |
航天 | 46篇 |
出版年
2023年 | 7篇 |
2022年 | 19篇 |
2021年 | 14篇 |
2020年 | 11篇 |
2019年 | 10篇 |
2018年 | 9篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 10篇 |
2014年 | 17篇 |
2013年 | 9篇 |
2012年 | 7篇 |
2011年 | 7篇 |
2010年 | 9篇 |
2009年 | 4篇 |
2008年 | 7篇 |
2007年 | 7篇 |
2006年 | 4篇 |
2004年 | 2篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 14篇 |
2000年 | 10篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 3篇 |
1996年 | 14篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1991年 | 3篇 |
1990年 | 2篇 |
排序方式: 共有249条查询结果,搜索用时 15 毫秒
191.
BTT导弹的自适应滑模反演控制设计 总被引:5,自引:0,他引:5
针对具有非匹配不确定性的BTT导弹非线性动力学模型,结合反演控制、自适应控 制和 滑模控制方法,设计了一种新颖的BTT导弹自适应反演滑模控制器。反演设计的每一步中均 采用具有范数型切换函数的连续滑模控制律,并采用自适应算法对不确定性的上界进行估计 。将虚拟控制量的导数作为不确定性处理,利用自适应滑模控制的鲁棒性对其进行补偿,解 决了“计算膨胀”问题,简化了控制系统的设计,并且设计中无需事先已知气动参数摄动 的上界。采用Lyapunov稳定性理论证明了跟踪误差最终有界。仿真结果显示了本文设计方法 的有效性。
相似文献
相似文献
192.
利用Fluke8508A参考级数字多用表和Guildline9334A直流标准电阻作标准,采用电流电压转换法,实现对高准确度直流标准电流源准确、可靠的校准。通过对其测量不确定度进行准确、详细的评定,证明可圆满地实现误差为±0.003%的高准确度直流标准电流源的校准,从而大大增强了对高准确度直流标准电流源的校准能力。 相似文献
193.
194.
195.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2023,71(1):539-555
The number of Earth orbiting objects is constantly growing, and some orbital regions are becoming risky environments for space assets of interest, which are increasingly threatened by accidental collisions with other objects, especially in Low-Earth Orbit (LEO). Collision risk assessment is performed by various methods, both covariance and non-covariance based. The Cube algorithm is a non-covariance-based method used to estimate the collision rates between space objects, whose concept consists in dividing the space in cubes of fixed dimension and, at each time instant, checking if two or more objects share the same cube. Up to now its application has been limited to the long-term scenarios of orbital debris evolutionary models, where considering the uncertainties is not necessary and impractical. Within operative contexts, instead, medium-term collision risk analysis may be an important task, in which the propagation-related uncertainties play a prominent role, but the timescale poses challenges for the application of standard covariance-based conjunction analysis techniques. In this framework, this paper presents an approach for the evaluation of the medium-term collision frequency for objects in LEO, called Uncertainty-aware Cube method. It is a modified version of the Cube, able to take the possible errors in the space objects’ position into account for the detection of the conjunctions. As an object’s orbit is propagated, the along-track position error grows more and more, and each object could potentially be in a different position with respect to the one determined by numerical propagation and, thus, in a different cube. Considering the uncertainties, at each time instant the algorithm associates more than one cube to each object and checks if they share at least one cube. If so, a conjunction is detected and a degree of confidence is evaluated. The performance of the method is assessed in different LEO scenarios and compared to the original Cube method. 相似文献
196.
197.
根据测量不确定度的原理,详细分析了涡轮流量计的校准不确定度,推导出它的计算公式,并且结合具体的流量校准装置进行了简化和计算举例。 相似文献
198.
199.
200.
Fabio Vargas 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(2):967-985
Measurements of dynamic parameters of atmospheric gravity waves, mainly the vertical wavelength, the momentum flux and the momentum flux divergence, are affected by large uncertainties crudely documented in the scientific literature. By using methods of error analysis, we have quantified these uncertainties for frequently observed temporal and spatial wave scales. The results show uncertainties of ~10%, ~35%, and ~65%, at least, in the vertical wavelength, momentum flux, and flux divergence, respectively. The large uncertainties in the momentum flux and flux divergence are dominated by uncertainties in the Brunt-Väisälä frequency and in spatial separation of the nightglow layers, respectively. The measured uncertainties in fundamental wave parameters such as the wave amplitude, intrinsic period, horizontal wavelength, and wave orientation are ~10% or less and estimated directly from our nightglow image data set. Other key environmental quantities such as the scale height and the Brunt-Väisälä frequency, frequently considered as constants in gravity wave parameter estimations schemes, are actually quite variable, presenting uncertainties of ~4% and ~9%, respectively, according to the several solar activity and seasonal atmosphere scenarios from the NRLMSISE-00 model simulated here. 相似文献