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采用三维SIMPLE程序和k-ε双方程湍流模型对三维受限垂直射流进行数值模拟,研究了不同的几何变量和流动参数对射流穿透和混合的影响。模拟结果表明,三维垂直射流最显著的流动特征是形成了流向旋涡。射流与来流的混合程度取决于旋涡的位置、作用范围和强弱。单股射流随动量比、旋涡强度和尺度的增加,混合增强。对于单排多股射流,喷孔间距直接影响旋涡涡心位置。密排射流,旋涡过于靠近下壁面,旋涡无法影响上面来流;但喷孔排列也不能过于稀疏,否则涡对靠的太近,旋涡对侧面影响不大。S/H和动量比不变,改变孔径D对射流穿透几乎无影响。这一重要结论说明S/H和J是决定多股受限射流穿透深度的最重要的量。 相似文献
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氮气源系统是根据我国大型空间环境模拟设备对纯净氮气的需要而设计的。文章介绍了该系统的主要理论计算部分,包括压缩机供气量的估算、主管路管径的选择、汽化器换热能力的计算、电加热器功率的计算等。 相似文献
257.
Houssam Toutanji Christopher M. Goff Edwin Ethridge Eric Stokes 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
Recent discoveries of water ice trapped within lunar topsoil (regolith) have placed a new emphasis on the recovery and utilization of water for future space exploration. Upon heating the lunar ice to sublimation, the resulting water vapor could theoretically transmit through the lunar regolith, to be captured on the surface. As the permeability of lunar regolith is essential to this process, this paper seeks to experimentally determine the permeability and flow characteristics of various gas species through simulated lunar regolith (SLR). Two different types of SLR were compacted and placed into the permeability setup to measure the flow-rate of transmitted gas through the sample. Darcy’s permeability constant was calculated for each sample and gas combination, and flow characteristics were determined from the results. The results show that Darcy’s permeability constant varies with SLR compaction density, and identified no major difference in permeable flow between the several tested gas species. Between the two tested SLR types, JSC-1A was shown to be more permeable than NU-LHT under similar conditions. In addition, a transition zone was identified in the flow when the gas pressure differential across the sample was less than ∼40 kPa. 相似文献
258.
多种示漏气体分析仪的研制 总被引:1,自引:1,他引:0
借鉴欧洲空间中心所用检漏仪的原理及主要技术措施,采用分子泵和机械泵的真空获得系统、钛升华泵和旁通阀真空维持系统、高灵敏的质谱分析系统,研制出了一次能检测出多个系统的高灵敏的多种示漏气体分析仪。文章介绍该分析仪的原理、设计方案、设计特点、设计计算。进行了性能测试,结果表明:该分析仪在大气环境条件下,最小可检测He,CF4的浓度小于5×10-8,对Ne小于5×10-7。 相似文献
259.
《中国航空学报》2021,34(7):135-156
Surface roughness is a critical health parameter of a turbine blade due to its implications on blade surface heat transfer and structural integrity. This paper proposes a physics-based online framework for Gas Turbine Engines (GTE), in order to assess the blade surface roughness in a high-pressure turbine without engine shutdown. The framework consolidates Gas Path Analysis (GPA) based performance monitoring models and meanline turbomachinery analysis, using a novel GPA-meanline matching process. This extracts meaningful performance deviation trends from GPA, while addressing the uncertainties associated with the measurements and modelling. To relate efficiency loss to surface roughness severity, a meanline-based system-identification process has been developed to establish the meanline representation of the turbine stage, and to incorporate the empirical surface roughness loss correlations. The roughness loss correlations have been evaluated against recent transonic test data in the literature. A modification to the compressibility correction factor has been made according to the evaluation outcome, which improved loss predictions compared to the experimental measurements. The framework was tested on the three-year operational data of a cogeneration GTE, and the results verified the framework's potential for online surface roughness monitoring. The predicted surface roughness showed agreement in both trend and the magnitude-level with the measurements reported in the literature. 相似文献
260.
以含硼贫氧固体推进剂为燃料,对带凹腔火焰稳定器的固体火箭超燃冲压发动机燃烧室构型首次开展了地面直连试验研究。试验模拟了23km,5.5Ma的飞行工况,通过测量压强、推力和流量等参数,得出了燃烧室性能。试验结果表明:一次富燃燃气在燃气发生器喉部沉积导致燃气流量持续提高,试验过程中当量比由0.44逐渐增加至0.54;本文所研究的凹腔稳焰结构提高了富燃燃气中气相可燃组分的燃烧效率,但对于凝相颗粒燃烧的促进效果不明显;试验工况下发动机总燃烧效率约48%,高空比冲约为423s,高于文献中所报道的中心支板喷射稳焰的固体火箭超燃冲压发动机试验比冲性能。 相似文献