全文获取类型
收费全文 | 178篇 |
免费 | 229篇 |
国内免费 | 69篇 |
专业分类
航空 | 285篇 |
航天技术 | 7篇 |
综合类 | 1篇 |
航天 | 183篇 |
出版年
2023年 | 9篇 |
2022年 | 34篇 |
2021年 | 26篇 |
2020年 | 33篇 |
2019年 | 31篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 25篇 |
2015年 | 19篇 |
2014年 | 25篇 |
2013年 | 31篇 |
2012年 | 18篇 |
2011年 | 28篇 |
2010年 | 22篇 |
2009年 | 15篇 |
2008年 | 10篇 |
2007年 | 13篇 |
2006年 | 19篇 |
2005年 | 10篇 |
2004年 | 6篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 1篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 5篇 |
排序方式: 共有476条查询结果,搜索用时 43 毫秒
451.
452.
An experimental study was conducted on turbulent separation behaviors induced by blunt fins with different sweep angles at Mach number 6.0. The Nano-particle based Planar Laser Scattering technique(NPLS) was applied to visualize the flowfield, complemented by pressure tests.Sweep angles of the fins were 10°, 20°,...,60°, with the same leading edge diameter of 10 mm. Fine structures of the interference flowfield induced by blunt fins have been obtained, including the shock systems and vortexes. I... 相似文献
453.
Characteristics of particle migration and deposition were numerically investigated in presence of aggressive swirl at the turbine inlet. The isolated effects of the inlet swirl were considered in detail by shifting the circumferential position of the swirl and by implementing positive and negative swirling directions. Particles were released from the turbine inlet and the resulting deposition on the vanes was determined by using the critical velocity model in a range of particle diameters from 1... 相似文献
454.
美国高超声速技术的发展与展望 总被引:5,自引:0,他引:5
高超声速技术是许多航空航天新技术的集合 ,它的发展将对世界安全、宇宙空间资源开发及相关学科产生重大影响。本报告介绍了美国取得的主要研究成果 ,进行了历史性的经验教训总结 ;重点对美国最新发展计划的内容进行了述评 ;分析了美国开发高超声速技术的战略选择及对世界安全形势带来的影响。最后阐明了高超声速技术全球化将会引发新一轮军备竞赛。 相似文献
455.
为了研究高超声速进气道的脉冲起动特性,对二元高超声速进气道在脉冲风洞中流场建立过程进行了数值模拟,并根据运动激波关系式建立了双波结构数学模型,分析了进气道脉冲起动过程中双波结构的产生及传播过程。研究表明通过理论计算得到的双波结构气动参数与仿真结果基本一致。结合仿真发现进气道脉冲起动过程流场的主要特征包括:运动激波与斜激波相交、激波/边界层相互干扰以及分离包的空间位置和自身体积变化、进气道自起动过程等。另外结合双波结构计算模型,通过仿真研究了影响双波结构流动参数及影响进气道脉冲起动特性的因素,发现初始条件影响进气道的脉冲起动特性主要是通过改变双波结构的强度实现的。 相似文献
456.
457.
458.
《中国航空学报》2023,36(5):421-433
The interception problem of Hypersonic Gliding Vehicles (HGVs) has been an important aspect of missile defense systems. In order to provide interceptors with accurate information of target trajectory, a model based on an improved Long Short-Time Memory (LSTM) network for trajectory prediction pipeline is proposed for the interception of a skip gliding hypersonic target. Firstly, for trajectory prediction required by intercepting guidance laws, the altitude, velocity and velocity direction of the target are formulated in the form of analytic functions, consisting of linear decay terms and amplitude decay sinusoidal terms. Then, the dynamic characteristics of the model parameters are analyzed, and the target trajectory prediction pipeline is proposed with the prediction error considered. Finally, an improved LSTM network is designed to estimate parameters in a dynamically-updated manner, and estimation results are used for the calculation of the final trajectory prediction pipeline. The proposed prediction algorithm provides information on the velocity vector for midcourse guidance with the effect of prediction errors on interception taken into account. Simulation is conducted and the results show the high accuracy of the algorithm in HGVs’ trajectory prediction which is conducive to increasing the interception success rate. 相似文献
459.
《中国航空学报》2022,35(10):56-66
Under hypersonic flow conditions, the complicated gas-graphene interactions including surface catalysis and surface ablation would occur concurrently and intervene together with the thermodynamic response induced by spacecraft reentry. In this work, the competing effects of surface heterogeneous catalytic recombination and ablation characteristics at elevated temperatures are investigated using the Reactive Molecular Dynamics (RMD) simulation method. A Gas-Surface Interaction (GSI) model is established to simulate the collisions of hyper-enthalpy atomic oxygen on graphene films in the temperature range of 500–2500 K. A critical temperature Tc around 900 K is identified to distinguish the graphene responses into two parts: at T < Tc, the heterogeneous surface catalysis dominates, while the surface ablation plays a leading role at T > Tc. Contradicting to the traditional Arrhenius expression that the recombination coefficient increases with the increase of surface temperature, the value is found to be relatively uniform at T < Tc but declines sharply as the surface temperature increases further due to the competing ablation effect. The occurrence of surface ablation decreases the amounts of active sites on the graphene surface for oxygen adsorption, leading to reduced recombination coefficient from both Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms. It suggests that the traditional Computational Fluid Dynamics (CFD) simulation method, which relies on the Arrhenius-type catalysis model, would result in large discrepancies in predicting aerodynamic heat for carbon-based materials during reentry into strong aerodynamic thermal environment. 相似文献
460.
《中国航空学报》2023,36(5):434-446
In response to the challenges of aerospace defense caused by the rapid development of hypersonic targets in recent years, the research on the unsupervised classification of flight states for hypersonic targets is carried out in this paper, which is based on the Hyperspectral Features (HFs) of hypersonic targets covered with plasma sheath during high-speed flight. First, a new concept of the super node is defined to improve classification accuracy by alleviating the intraclass variability of HFs. Then, the frequency domain information of the curve of HFs is utilized to reduce the feature redundancy according to the prior theoretical knowledge that the fluctuation characteristics of HFs of the same flight states are similar. Finally, an unsupervised classification method based on the Density Peak Clustering (DPC) for HFs is designed to class flight states after eliminating the impact of intraclass variability and feature dimension redundancy. The proposal is compared with the traditional classification algorithms on simulated hyperspectral data sets of typical flight states of the hypersonic vehicle and an actual-observation hyperspectral data set. The results indicate that the performance of our proposal has competitive advantages in terms of Overall Accuracy (OA), Average Accuracy (AA) and Kappa coefficient. 相似文献