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181.
自激励式电磁铆接放电电流分析 总被引:1,自引:0,他引:1
电磁铆接是一种将电磁能转化为机械能的铆接工艺。传统感应式低电压电磁铆接存在能量利用率低、难以解决高强度大直径铆钉和难成形材料铆钉的铆接等问题。基于自激励式电磁铆接技术,建立放电电流分析模型,通过数值分析与工艺试验探讨自激励式电磁铆接进行大直径铆钉成形的可行性。研究结果表明建立的电磁铆接放电电流分析模型可实现传统感应式和自激励式电磁铆接放电电流分析,分析结果与试验吻合较好;放电能量相同时,自激励式电磁铆接的涡流斥力峰值要远大于感应式的涡流斥力,能有效提高能量利用率,是实现大直径铆钉成形的有效方式;在放电电压为320V时,自激励式电磁铆接可实现直径为10mm的45号钢铆钉的成形,其变形以绝热剪切的方式进行。 相似文献
182.
This paper compares the flame acceleration in single-trial dual-detonation tubes triggered by a spark plug and non-thermal plasma igniter. The low-temperature plasma was generated by an in-house novel AC-driven dielectric barrier discharge igniter, which reduces the power supply requirements and was applied in the quiescent ignition of a single-trial detonation tube. Three different types of detonation mixtures were tested with flame propagation tracked by ion probes and pressure waves recorded by high-frequency pressure transducers. The flame propagation speeds were calculated and compared based on signals from the ion probes. The detonation combustion succeeded in the dual tubes, but the deflagration-to-detonation transition could be significantly accelerated by the plasma for all mixtures, as it was shortened by more than 50% compared to that of the spark plug. The present study provides a suitable technological approach for igniters of PDEs. 相似文献
183.
Aerodynamic performance of low-Reynolds number flyers, for a chord-based Reynolds number of 105 or below, is sensitive to wind gusts and flow separation. Active flow control offers insight into fluid physics as well as possible improvements in vehicle performance. While facilitating flow control by introducing feedback control and fluidic devices, major challenges of achieving a target aerodynamic performance under unsteady flow conditions lie on the high-dimensional nonlinear dynamics of the flow system. Therefore, a successful flow control framework requires a viable as well as accessible control scheme and understanding of underlying flow dynamics as key information of the flow system. On the other hand, promising devices have been developed recently to facilitate flow control in this flow regime. The dielectric barrier discharge (DBD) actuator is such an example; it does not have moving parts and provides fast impact on the flow field locally. In this paper, recent feedback flow control studies, especially those focusing on unsteady low-Reynolds number aerodynamics, are reviewed. As an example of an effective flow control framework, it is demonstrated that aerodynamic lift of a high angle-of-attack wing under fluctuating free-stream conditions can be stabilized using the DBD actuator and an adaptive algorithm based on general input–output models. System nonlinearities and control challenges are discussed by assessing control performance and the variation of the system parameters under various flow and actuation conditions. Other fundamental issues from the flow dynamics view point, such as the lift stabilization mechanism and the influence on drag fluctuation are also explored. Both potentiality and limitation of the linear modeling approach are discussed. In addition, guidelines on system identification and the controller and actuator setups are suggested. 相似文献
184.
Flow separation,as an aerodynamic phenomenon,occurs in specific conditions.The conditions are studied in a wind tunnel on different airfoils.The phenomenon can be delayed or suppressed by exerting an external momentum to the flow.Dielectric barrier discharge actuators arranged in a row of 8 and perpendicular to the flow direction can delay flow separation by exerting the momentum.In this study,a mathematical model is developed to predict a parameter,which is utilized to represent flow separation on an NACA0012 airfoil.The model is based on the neurofuzzy method applied to experimental datasets.The neuro model is trained in different flow conditions and the parameter is measured by pressure sensors. 相似文献
185.
186.
基于脉冲电源的MOSFET驱动电路研究及应用 总被引:1,自引:0,他引:1
分析了在电火花等精密加工中MOSFET驱动器的隔离技术及特点,提出了可靠驱动MOSFET的设计思路,并在实际中得到应用。 相似文献
187.
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189.
钡钨空心阴极等离子体放电模式实验研究 总被引:1,自引:0,他引:1
主要通过实验的手段,系统研究了钡钨空心阴极的等离子体放电特性及其工作模式。实验中,使空心阴极工作在三极管构型下,调节相应的放电参数,详细分析钡钨空心阴极放电特性的变化规律、存在的放电模式及其转化规律。最后得到结论:钡钨空心阴极放电表现为羽毛状、亮斑状和弥漫状等3种典型的工作模式;不同放电模式可以用放电电流、放电电压及其振荡特性进行判定和区分;随着放电参数的变化,几种放电模式之间可以相互转化。 相似文献
190.