全文获取类型
收费全文 | 132篇 |
免费 | 21篇 |
国内免费 | 21篇 |
专业分类
航空 | 85篇 |
航天技术 | 28篇 |
综合类 | 6篇 |
航天 | 55篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 12篇 |
2013年 | 11篇 |
2012年 | 10篇 |
2011年 | 9篇 |
2010年 | 8篇 |
2009年 | 6篇 |
2008年 | 7篇 |
2007年 | 14篇 |
2006年 | 13篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 2篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 5篇 |
1991年 | 1篇 |
排序方式: 共有174条查询结果,搜索用时 46 毫秒
71.
本文应用多输入、多输出跟踪模型法,对CCV型飞机纵向飞行控制系统的解耦控制律问题进行了研究。并以某型飞机为例,说明如何应用该方法确定三种纵向直接力模态的动态解耦控制律。 相似文献
72.
《中国航空学报》2023,36(4):120-133
In order to meet the demand of CubeSats for low power and high-performance micro-propulsion system, a porous ionic liquid electrospray thruster prototype is developed in this study. 10 × 10 conical emitter arrays are fabricated on an area of 3.24 cm2 by computer numerical control machining technology. The propellant is 1-ethyl-3-methylimidazolium tetrafluoroborate. The overall dimension of the assembled prototype is 3 cm × 3 cm × 1 cm, with a total weight of about 15 g (with propellant). The performance of this prototype is tested under vacuum. The results show that it can work in the voltage range of ±2.0 kV to ±3.0 kV, and the maximum emission current and input power are about 355 μA and 1.12 W. Time of Flight (TOF) mass spectrometry results show that cationic monomers and dimers dominate the beam in positive mode, while a higher proportion of higher-order solvated ion clusters in negative mode. The maximum specific impulse is 2992 s in positive mode and 849 s in negative mode. The thrust is measured in two methods: one is calculated by TOF results and the other is directly measured by high-precision torsional thrust stand. The thrust (T) obtained by these two methods conforms to a certain scaling law with respect to the emission current (Iem) and the applied voltage (Vapp), following the scale of T ∼ IemVapp0.5, and the thrust range is from 2.1 μN to 42.6 μN. Many thruster performance parameters are significantly different in positive and negative modes. We speculate that due to the higher solvation energy of the anion, more solvated ion clusters are formed rather than pure ions under the same electric field. It may help to improve thruster performance if porous materials with smaller pore sizes are used as reservoirs. Although there are still many problems, most of the performance parameters of ILET-3 are good, which can theoretically meet the requirements of CubeSats for micro-propulsion system. 相似文献
73.
声纳是对水下目标进行定位、导航和通讯的主要手段。在现代声纳中常要求在一部声纳中同时具有几种信号工作方式的功能,例如单频脉冲信号工作方式、键控式调频信号工作方式等等。这就要求作为声纳发射机的驱动信号源要有相当高的频率稳定度和准确度,特别对于调频信号。介绍一种用单片直接频率合成器(DDS)产生上述信号的电路设计,该电路具有转变信号工作方式方便,并具有晶体振荡器的频率准确度和稳定度。 相似文献
74.
偏置动量卫星偏航姿态估计与控制研究 总被引:2,自引:1,他引:2
为改善偏置动量卫星无偏航姿态敏感器时用滚动角间接控制偏航姿态的精度,基于降维观测器设计提出了一种采用偏航角估计值直接控制偏航姿态方法。在分析收敛性的基础上,给出了降维观测器的设计,以及直接控制法的系统模型。理论分析和仿真结果表明,该法能大幅提高偏置动量卫星的姿态精度,且易于软件实现,不增加系统硬件配置。 相似文献
75.
3D-printing technologies are receiving an always increasing attention in architecture, due to their potential use for direct construction of buildings and other complex structures, also of considerable dimensions, with virtually any shape. Some of these technologies rely on an agglomeration process of inert materials, e.g. sand, through a special binding liquid and this capability is of interest for the space community for its potential application to space exploration. In fact, it opens the possibility for exploiting in-situ resources for the construction of buildings in harsh spatial environments. The paper presents the results of a study aimed at assessing the concept of 3D printing technology for building habitats on the Moon using lunar soil, also called regolith. A particular patented 3D-printing technology – D-shape – has been applied, which is, among the existing rapid prototyping systems, the closest to achieving full scale construction of buildings and the physical and chemical characteristics of lunar regolith and terrestrial regolith simulants have been assessed with respect to the working principles of such technology. A novel lunar regolith simulant has also been developed, which almost exactly reproduces the characteristics of the JSC-1A simulant produced in the US. Moreover, tests in air and in vacuum have been performed to demonstrate the occurrence of the reticulation reaction with the regolith simulant. The vacuum tests also showed that evaporation or freezing of the binding liquid can be prevented through a proper injection method. The general requirements of a Moon outpost have been specified, and a preliminary design of the habitat has been developed. Based on such design, a section of the outpost wall has been selected and manufactured at full scale using the D-shape printer and regolith simulant. Test pieces have also been manufactured and their mechanical properties have been assessed. 相似文献
76.
Nicolao Fornengo 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(12):2010-2018
In this review article the current status of particle dark matter is addressed. We discuss the main theoretical extensions of the standard model which allow to explain dark matter in terms of a (yet undiscovered) elementary particle. We then discuss the theoretical predictions for the searches of particle dark matter: direct detection in low-background underground experiments and indirect detection of neutrinos, gamma-rays and antimatter with terrestrial and space-borne detectors. Attention will be placed also on the discussion of the uncertainties, mainly of astrophysical origin, which affect the theoretical predictions. The constraints placed by these searches on the extensions of the standard models will be briefly addressed. 相似文献
77.
文章首先引入了一类不可微数学规划的高阶Mond-Weir对偶模型以及高阶V-不变凸、高阶广义V-不变吐的概念。然后,在ShashiK.Mishra和Norma.G.Rueda所做工作的基础上,对于上述高阶对偶模型建立了高阶V-不变凸条件下的弱埘偶和强对偶理论。最后,进一步在更弱的高阶广义V-不变凸条件下的建立了Mond-Weir型对偶模型的弱对偶和强对偶理论。 相似文献
78.
根据哈密顿原理建立了三维压电动力学耦合系统的哈密顿对偶体系,将经典的弹性力学一类变量问题转化为二类变量,并建立了哈密顿正则方程组.分别在不同坐标系下研究了功能梯度压电材料FGPM(Functionally Graded Piezoelectric Material)四边简支板及两端简支管的静动力学特性,通过辛算法进行了数值分析.结果表明,在哈密顿对偶体系中能够求解复杂FGPM结构机电耦合静动力学问题;在FGPM多层板/管结构中,面外变量在厚度方向连续分布,而面内变量在材料分界面处存在突变现象. 相似文献
79.
80.