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281.
驻涡燃烧室凹腔温度变化规律及气量分配   总被引:4,自引:2,他引:2  
通过对单双涡燃烧室进行热态试验研究,研究余气系数、进口气流参数对凹腔壁温分布的影响,并通过三维数值模拟对燃烧室及凹腔气流量进行计算,得到壁温分布规律,为燃烧室材料选择以及气量分配的后续优化做好铺垫.试验结果表明,单涡试验件的最高壁温出现在凹腔后壁面;燃烧室余气系数变化改变了双涡试验件最高壁温的位置;数值模拟结果比较准确的得到了驻涡燃烧室的气流量分布.  相似文献   
282.
VDMOSFET导通电阻的最佳化设计   总被引:2,自引:0,他引:2  
分析了VDMOSFET导通电阻模型,提出了单胞尺寸是影响导通电阻的最重要因素。单胞尺寸的最佳化选择可使器件的特征导通电阻RonA(单位面积导通电阻)最小,并通过大量理论计算给出击穿电压为50V时的最佳单胞尺寸。  相似文献   
283.
通过对JTdble及相应Swing组件的内部机制的研究,较为详细地介绍了在用JTable制作表格型编辑器时,对指定列的单元编辑器实现输入校验的技术;并对所涉及的类及自定义扩展类作了说明。  相似文献   
284.
Experimental study of an aircraft fuel tank inerting system   总被引:3,自引:2,他引:1  
In this work, a simulated aircraft fuel tank inerting system has been successfully established based on a model tank. Experiments were conducted to investigate the influences of different operating parameters on the inerting effectiveness of the system, including flow rate of the inert gas(nitrogen-enriched air), inert gas concentration, fuel load of the tank and different inerting approaches. The experimental results show that under the same operating conditions, the time span of a complete inerting process decreased as the flow rate of inert gas was increased; the time span using the inert gas with 5% oxygen concentration was much longer than that using pure nitrogen;when the fuel tank was inerted using the ullage washing approach, the time span increased as the fuel load was decreased; the ullage washing approach showed the best inerting performance when the time span of a complete inerting process was the evaluation criterion, but when the decrease of dissolved oxygen concentration in the fuel was also considered to characterize the inerting effectiveness, the approach of ullage washing and fuel scrubbing at the same time was the most effective.  相似文献   
285.
新一代便携式飞机称重系统的研制及应用   总被引:1,自引:0,他引:1  
介绍了一种新研制出的便携式飞机称重系统,较详细的介绍了系统有很低的原理及应用。  相似文献   
286.
Aircraft conceptual design optimizations that maximize the performance at a design condition (single-point) may result in designs with unsatisfying off-design performance. To further improve aircraft efficiency under actual flight operations, there is a need to consider multiple flight conditions (multipoint) in aircraft conceptual design and optimization. A new strategy for multipoint optimizations in aircraft conceptual design is proposed in this paper. A wide-body aircraft is taken as an example for both single-point and multipoint optimizations with the objective of maximizing the specific hourly productivity. Boeing 787-8 flight data was used in the multipoint optimization to reflect the true objective function. The results show that the optimal design from the multipoint optimization has a 7.72% total specific hourly productivity increase of entire flight missions compared with that of the baseline aircraft, while the increase in the total specific hourly productivity from the single-point optimal design is only 5.73%. The differences between the results of single-point and multipoint optimizations indicate that there is a good option to further improve aircraft efficiency by considering actual flight conditions in aircraft conceptual design and optimization.  相似文献   
287.
Solar-powered aircraft have attracted great attention owing to their potential for longendurance flight and wide application prospects.Due to the particularity of energy system, flight strategy optimization is a significant way to enhance the flight performance for solar-powered aircraft.In this study, a flight strategy optimization model for high-altitude long-endurance solar-powered aircraft was proposed.This model consists of three-dimensional kinematic model,aerodynamic model, energy collection model, energy store model and energy loss model.To solve the nonlinear optimal control problem with process constraints and terminal constraints, Gauss pseudo-spectral method was employed to discretize the state equations and constraint equations.Then a typical mission flying from given initial point to given final point within a time interval was considered.Results indicate that proper changes of the attitude angle contribute to increasing the energy gained by photovoltaic cells.Utilization of gravitational potential energy can partly take the role of battery pack.Integrating these two measures, the optimized flight strategy can improve the final state of charge compared with current constant-altitude constant-velocity strategy.The optimized strategy brings more profits on condition of lower sunlight intensity and shorter daytime.  相似文献   
288.
Successful growth and development of higher plants in space rely on adequate availability and uptake of water and nutrients, and efficient energy distribution through photosynthesis and gas exchange. In the present review, literature has been reviewed to assemble the relevant knowledge within space plant research for future planetary missions. Focus has been on fractional gravity, space radiation, magnetic fields and ultimately a combined effect of these factors on gas exchange, photosynthesis and transport of water and solutes.  相似文献   
289.
霍尔推力器通道等离子体与壁面有很强的相互作用,为了降低壁面腐蚀,提高在轨寿命, 针对推力器全通道放电过程建立二维物理模型,采用粒子模拟方法(Particle In Cell),数值研究了电离区壁面分割高于阳极偏压的低发射石墨电极对推力器放电特性的影响,讨论了放电通道电势、离子数密度、电子温度、电离速率及比冲的变化规律。结果表明:在电离区不同位置分割高偏压电极对等离子体放电特性影响明显,电极位置在电离区前端时,电极偏压高于阳极电压60V时通道内放电等离子体参数几乎不变。而电极位置在电离区末端,电极偏压高于阳极电压18V时就会导致加速区轴向扩张,离子聚焦效果强,电子温度显著升高,电子与壁面相互作用减弱,羽流发散角减小。由此推力器比冲提升约12%,寿命延长,性能提高。  相似文献   
290.
为突破实际测试当中的局限,研究了横电磁波传输(TEM)室频率范围的扩展方法。运用电磁场与微波技术相关原理,通过分析TEM室壳体开缝对高次模的影响,利用壳体表面电流分布变化规律和波导缝隙天线原理重新解释了开缝对高次模的抑制作用,进而提出了一种TEM室壳体表面开缝的设计方法。通过电磁场数值仿真,验证了抑制高次模工程方法的有效性,并对其控制参数和约束条件的准确性进行了分析评估;通过加工实物并进行实测,进一步验证了新方法的效果。仿真与测试结果表明,开缝抑制高次模的工程方法能够在不减小测试空间与影响主模传输的前提下,将测试带宽扩展了42.9%。   相似文献   
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