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241.
弯管是粉末燃料冲压发动机燃料输送系统的重要组成部分,为了研究弯管内气固两相流的流场结构、颗粒碰撞以及压力损失的变化规律,基于连续相-离散元(CFD-DEM)耦合模型,考虑颗粒的碰撞受力和弹塑性形变,对铝粉在弯管内的流动状况进行数值仿真。研究结果表明:CFD-DEM算法相对于传统的双流体模型和轨道法,能更为准确地描述颗粒流的碰撞信息和两相流的流动状况。弯管内的总压损失随流化气流量的增加,呈先减少再增加的趋势,在本文研究的条件下,优选的流化气流量为6g/s~7g/s(流化气速度为3.0m/s~3.5m/s);在低流速下,颗粒间的碰撞次数远大于颗粒-壁面间的碰撞,随着流速的增高,颗粒与外侧壁面间的碰撞次数迅速增高,并导致颗粒-壁面间的碰撞次数超过颗粒间的碰撞。弯管的弯径越大,弯管内的总压损失越大,但颗粒-颗粒、颗粒-壁面的碰撞次数均减少。 相似文献
242.
Benkai LI Chenwei DAI Wenfeng DING Changyong YANG Changhe LI Olga KULIK Vyacheslav SHUMYACHER 《中国航空学报》2021,34(8):65-74
In this article, a grinding force model, which is on the basis of cutting process of single abrasive grains combined with the method of theoretical derivation and empirical formula by analyzing the formation mechanism of grinding force, was established. Three key factors have been taken into accounts in this model, such as the contact friction force between abrasive grains and materials, the plastic deformation of material in the process of abrasive plowing, and the shear strain effect of material during the process of cutting chips formation. The model was finally validated by the orthogonal grinding experiment of powder metallurgy nickel-based superalloy FGH96 by using the electroplated CBN abrasive wheel. Grinding force values of prediction and experiment were in good consistency. The errors of tangential grinding force and normal grinding force were 9.8% and 13.6%, respectively. The contributions of sliding force, plowing force and chip formation force were also analyzed. In addition, the tangential forces of sliding, plowing and chip formation are 14%, 19% and 11% of the normal forces on average, respectively. The pro-posed grinding force model is not only in favor of optimizing the grinding parameters and improving grinding efficiency, but also contributes to study some other grinding subjects (e.g. abrasive wheel wear, grinding heat, residual stress). 相似文献
243.
使用基于Lee多孔材料屈服模型推导出的韧性损伤模型,对导向器类粉末金属零件成形过程中,在应力、应变、密度分布及其积累因素影响下,材料的损伤状态进行了数值模拟,在不同的加载状态下,压坯各点的损伤状况和破裂过程进行了跟踪,实验证实模拟结果具有较高的精度。 相似文献
244.
《中国航空学报》2023,36(1):423-433
Real-time mixing of multi-species powder challenges Laser Metal Deposition (LMD) of Functionally Graded Materials (FGMs). The current work proposes a novel method of using a static mixer to realize rapid, uniform multi-species powder mixing. Firstly, copper powder and 316L stainless steel powder are selected to complete the powder mixing observation experiment with Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS). Secondly, computational fluid dynamics and particle mixing simulation models are used to analyze the flow field and particle motion characteristics in the static mixer. Finally, LMD experiment and metallographic observation are carried out with 316L stainless steel powder and WC powder to verify the feasibility of the static mixer. This study provides a theoretical and practical basis for powder mixing in laser processing with a static mixer. The conclusions can also be applied to other processing fields requiring real-time and uniform mixing of multi-species powders. 相似文献
245.
This paper presents how the combustion performance of nano-sized aluminum(nAl)powder in carbon dioxide are affected by silica. The ignition and combustion performance of nAl powder with silica addition were studied by a high-temperature tube furnace. An s-type thermocouple and a high-speed motion acquisition instrument were performed to evaluate the ignition temperature, maximum combustion temperature, maximum change of rate of temperature, and combustion propagation speed. The combustion effici... 相似文献
246.
黑火药作为固体火箭发动机中常用的点火药,是决定其工作性能的关键因素。为了研究黑火药在真空环境下的点火性能,通过真空点火试验,测试了不同点火结构、不同黑火药质量下的点火压力曲线和羽流现象,并与常压点火试验结果对比,分析了不同工况下黑火药点火性能的优劣。结果表明:真空环境下增加黑火药质量可以提高点火压强峰值,与常压条件相比提升幅度较小;与常压试验对比,真空下前端点火和尾部点火产生的压强峰值都会下降2MPa左右;不同黑火药质量的常压或真空点火试验中,前端点火试验样机到达压强峰值的时间都近似为5ms,而尾部点火试验样机到达峰值的时间不同;在真空点火试验中,羽流扩张角会在一段时间内变大或变小,即出现明显的黑火药不稳定燃烧现象,试验结束后有较多未燃烧完全的黑火药残留在发动机周围,而在常压点火试验中,这些未燃烧完全的黑火药颗粒会在空气中二次燃烧,黑火药残留较少。 相似文献