全文获取类型
收费全文 | 147篇 |
免费 | 145篇 |
国内免费 | 55篇 |
专业分类
航空 | 163篇 |
航天技术 | 6篇 |
综合类 | 1篇 |
航天 | 177篇 |
出版年
2024年 | 1篇 |
2023年 | 8篇 |
2022年 | 23篇 |
2021年 | 17篇 |
2020年 | 26篇 |
2019年 | 25篇 |
2018年 | 13篇 |
2017年 | 5篇 |
2016年 | 23篇 |
2015年 | 13篇 |
2014年 | 21篇 |
2013年 | 25篇 |
2012年 | 17篇 |
2011年 | 25篇 |
2010年 | 16篇 |
2009年 | 9篇 |
2008年 | 5篇 |
2007年 | 11篇 |
2006年 | 15篇 |
2005年 | 7篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
排序方式: 共有347条查询结果,搜索用时 31 毫秒
271.
《中国航空学报》2020,33(6):1589-1601
In this paper, numerical investigation of hypersonic gas flow over two typical gap-cavity structures is carried out using all-speed preconditioned density-based solver. Such structures filled with porous seal in the gap are often present at the joint locations of control surfaces of the hypersonic vehicles. Single-domain approach is adopted to integrate the governing equations for both porous and fluid regions. The basic thermal invasion characteristic is first illustrated using the maze gap-cavity structure without sealing. Then, the influence of seal filling depth on the thermal invasion characteristic is investigated for the structure with sealing. Finally, a comparison of thermal invasion characteristics between maze and straight gap-cavity structures is performed to examine the influence of gap bending. Results show that the main source of hot airflow invading into the gap is from the millimeter scale gas layer within the boundary layer. And the invasion characteristic presents approximate stationary behavior. A primary vortex occurs in the gap adjacent to the leeward wall, which is ascribed to the impinging effect between the separate boundary flow and the windward wall. This effect is also the main driving force of thermal invasion. A treatment of filling the seal in certain depth inside the gap can significantly reduce the thermal load of seal and maintain an acceptable level of the invading mass flow rate. Additionally, it is found that the gap bending exerts a limited block effect on the thermal invasion without sealing, and this effect can be ignored with sealing. These results can provide a reference for optimizing the seal gap-cavity structure configuration. 相似文献
272.
针对机载雷达对高超音速运动目标的检测性能下降问题,首先建立了高超音速运动目标回波信号模型,在此基础上定量分析了目标高超音速运动引起的跨距离单元走动和多普勒频率时变现象。经过详细推导,利用Keystone变换法完成了回波的跨距离单元走动校正,并将基于高阶模糊度函数的参数估计技术应用于高超音速目标多普勒参量估计中,补偿多普勒高阶项后进行相参积累处理。通过计算机仿真证明了所提方法的有效性。 相似文献
273.
274.
275.
A series of cross-sectional flow fields of Counterrotating Vortex Pairs(CVPs) generated by a large-scale ramp vortex generator is observed using an ice-cluster-based Planar Laser Scattering(PLS) method in a shock tunnel with a nominal flow Mach number of 6. Combined with a numerical simulation, two streamwise CVPs with opposite rotating directions are identified in the wake flow of the vortex generator with an absence of a boundary layer, namely, a Primary CVP(PCVP) and a Secondary CVP(SCVP). Th... 相似文献
276.
This paper focuses on the usage of the forward-facing cavity and opposing jet combinatorial configuration as the thermal protection system (TPS) for hypersonic vehicles. A hemispherecone nose-tip with the combinatorial configuration is investigated numerically in hypersonic free stream. Some numerical results are validated by experiments. The flow field parameters, aerodynamic force and surface heat flux distribution are obtained. The influence of the opposing jet stagnation pressure on cooling efficiency of the combinatorial TPS is discussed. The detailed numerical results show that the aerodynamic heating is reduced remarkably by the combinatorial system. The recirculation region plays a pivotal role for the reduction of heat flux. The larger the stagnation pressure of opposing jet is, the more the heating reduction is. This kind of combinatorial system is suitable to be the TPS for the high-speed vehicles which need long-range and long time flight. 相似文献
277.
Air-breathing hypersonic vehicles (HSVs) are typically characterized by interactions of elasticity, propulsion and rigid-body flight dynamics, which may result in intractable aeroservoelastic problem. When canard is added, this problem would be even intensified by the introduction of low-frequency canard pivot mode. This paper concerns how the aeroservoelastic stability of a canard-configured HSV is affected by the pivot stiffnesses of all-moveable horizontal tail (HT) and canard. A wing/pivot system model is developed by considering the pivot torsional flexibility, fuselage vibration, and control input. The governing equations of the aeroservoelastic system are established by combining the equations of rigid-body motion, elastic fuselage model, wing/pivot system models and actuator dynamics. An unsteady aerodynamic model is developed by steady Shock-Expansion theory with an unsteady correction using local piston theory. A baseline controller is given to provide approximate inflight characteristics of rigid-body modes. The vehicle is trimmed for equilibrium state, around which the linearized equations are derived for stability analysis. A comparative study of damping ratios, closed-loop poles and responses are conducted with varying controller gains and pivot stiffnesses. Available bandwidth for control design is discussed and feasible region for pivot stiffnesses of HT and canard is given. 相似文献
278.
279.
为满足高超声速飞行器舱内温度要求,提出了在舵轴热短路区域使用相变材料进行热耗散的方案.通过开展导热增强型相变材料温控试验,获得了不同试验方案对舵轴及周围金属壳体的降温效果.结果表明,导热增强型相变材料由于良好的导热性能,能够很好地发挥相变吸热能力,对降低舵轴热短路区域的局部高温具有显著效果;金属壳体内、外同时使用低温和中温相变装置,能够将舵轴周围金属壳体温度控制在允许工作温度范围内(150℃).本研究可为飞行器舵轴温控设计提供指导. 相似文献
280.
Convection coefficients and heat fluxes due to aerodynamic heating on critical surfaces of hypersonic vehicle are obtained analytically. The applicability of recovery temperature for stagnation regions is discussed. Convection coefficient for the bicurvature forward stagnation region is obtained directly from 2-D stagnation region correlation, using the two principal radii of curvatures. Convective heat flux to swept-back leading edge (SBLE) surface is obtained from the 2-D stagnation region and flat plate heat fluxes, using the respective velocity vector components. Results reveal the concepts of temperature-minimised-sweepback, and the thermally-benign sharp SBLE effect at high sweepback angles. 相似文献