全文获取类型
收费全文 | 221篇 |
免费 | 109篇 |
国内免费 | 20篇 |
专业分类
航空 | 192篇 |
航天技术 | 45篇 |
综合类 | 25篇 |
航天 | 88篇 |
出版年
2024年 | 4篇 |
2023年 | 2篇 |
2022年 | 16篇 |
2021年 | 16篇 |
2020年 | 19篇 |
2019年 | 13篇 |
2018年 | 12篇 |
2017年 | 8篇 |
2016年 | 5篇 |
2015年 | 7篇 |
2014年 | 15篇 |
2013年 | 15篇 |
2012年 | 12篇 |
2011年 | 18篇 |
2010年 | 7篇 |
2009年 | 11篇 |
2008年 | 10篇 |
2007年 | 22篇 |
2006年 | 20篇 |
2005年 | 7篇 |
2004年 | 12篇 |
2003年 | 8篇 |
2002年 | 12篇 |
2001年 | 10篇 |
2000年 | 5篇 |
1999年 | 14篇 |
1998年 | 5篇 |
1997年 | 14篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1989年 | 1篇 |
排序方式: 共有350条查询结果,搜索用时 15 毫秒
61.
Aeroelastic two-level optimization for preliminary design of wing structures considering robust constraints 总被引:1,自引:0,他引:1
An aeroelastic two-level optimization methodology for preliminary design of wing struc- tures is presented, in which the parameters for structural layout and sizes are taken as design vari- ables in the first-level optimization, and robust constraints in conjunction with conventional aeroelastic constraints are considered in the second-level optimization. A low-order panel method is used for aerodynamic analysis in the first-level optimization, and a high-order panel method is employed in the second-level optimization. It is concluded that the design of the abovementioned structural parameters of a wing can be improved using the present method with high efficiency. An improvement is seen in aeroelastic performance of the wing obtained with the present method when compared to the initial wing. Since these optimized structures are obtained after consideration of aerodynamic and structural uncertainties, they are well suited to encounter these uncertainties when they occur in reality. 相似文献
62.
郑熙强 《南昌航空工业学院学报》1997,(1):27-32
设G是一个格序群,П(G),П(m(G),P(G),C(G)分别是G的素子群,极小素子群,极子群,凸1-子群集合,Ω(G)是P(G)在C(G)中生成的闭子格。Ω(G)的元素称为G的Ω-子群。 相似文献
63.
H.R. Alimohammadi H. Naseh F. Ommi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(5):1682-1700
One of the challenges of combustion chamber and nozzle design in a Liquid Propellant Engine (LPE) is to predict the behavior and performance of the cooling system. Therefore, while designing, the optimization of the cooling system is always of great importance. This paper presents the multi-objective optimization of the LPE’s cooling system. To this end, a novel framework has been developed, resulting from the application of the Response Surface Method (RSM) and the correlation coefficients matrix, sensitivity analysis and the The Particle Swarm Optimization (PSO). based on this method, the input variables, constraints, objective functions, and their surfaces were identified. In terms of multi-optimization algorithms, RSM and PSO are utilized to get global optimum. In conclusion, the methodology capability is to optimize the LPE’s cooling system, 6 percentage increase in total heat transfer and 7 bar decrease cooling system pressure loss, which resulted in a 1.2-seconds increase in the specific impulse of the engine. 相似文献
64.
Zhenli CHEN Minghui ZHANG Yingchun CHEN Weimin SANG Zhaoguang TAN Dong LI Binqian ZHANG 《中国航空学报》2019,32(8):1797-1827
Civil aviation faces great challenges because of its robust projected future growth and potential adverse environmental effects. The classical Tube-And-Wing(TAW) configuration following the Cayley's design principles has been optimized to the architecture's limit, which can hardly satisfy the further requirements on green aviation. By past decades' investigations the BlendedWing-Body(BWB) concept has emerged as a potential solution, which can simultaneously fulfill metrics of noise, emission and fuel burn. The purpose of the present work is to analyze the developments of critical technologies for BWB conceptual design from a historical perspective of technology progress. It was found that the high aerodynamic efficiency of BWB aircraft can be well scaled by the mean aerodynamic chord and wetted aspect ratio, and should be realized with the trade-offs among stability and control and low-speed performance. The structure concepts of non-cylinder pressurized cabin are of high risks on weight prediction and weight penalty. A static stability criterion is recommended and further clear and adequate criteria are required by the evaluations of flying and handling qualities. The difficulties of propulsion and airframe integration are analyzed. The energy to revenue work ratios of well-developed BWB configurations are compared,which are 31.5% and 40% better than that of TAW, using state-of-art engine technology and future engine technology, respectively. Finally, further study aspects are advocated. 相似文献
65.
分析了铝合金锻件重复淬火保温时间的长短及其组织性能的影响情况。根据大量的试验数据,证实了重复淬火保温时间及时效保温时间的长短对锻件性能的直接影响,并以此确定了合理的工艺参数。 相似文献
66.
可伸缩挠性结构的稳定性研究 总被引:4,自引:1,他引:3
张洪华 《中国空间科学技术》1997,17(5):1-5
研究了一类可伸缩挠性梁结构的稳定性。主要结论有:一般可伸缩挠性梁结构的动力学可由刚体姿态运动、挠性体振动和梁伸缩运动相耦合的混合偏微分方程和常微分方程描述;结构振动与转动能量的耗散与积聚取决于梁的伸缩运动,在伸展过程中系统的能量被耗散,在收缩过程中系统能量被积聚,在平台保持过程系统能量维持不变。因此,梁的伸展过程是稳定的,梁的收缩过程是不稳定的,而平台保持过程是临界稳定的。 相似文献
67.
火箭新型号总体方案论证时,一般借鉴国内外相近规模和相同推进剂火箭的结构系数进行类比确定子级结构系数,按照比例系数分配贮箱和壳段等部段的质量,但该质量分配不能反映载荷对结构设计的影响,在细化迭代设计中易造成方案无法闭环,导致设计工作反复。为了加快总体方案论证,提出一种基于载荷的箭体结构快速估重方法,开发形成结构估重数字化模块并嵌入总体设计平台。应用案例表明,提出的数字化估重平台能够有效提高估重精度,同时显著缩短论证周期,兼具总体方案比较和优化、全箭质量管理等功能,能有效降低方案推翻重新设计的风险,在新型号总体方案论证中发挥了重要作用。 相似文献
68.
69.
中国民航飞行学院在五十五年的建校过程中逐步形成了自身的“飞院文化”,包括物质文化、行为文化、精神文化和制度文化四个方面。这四个方面相互联系、相互依存,共同形成“飞院文化”的丰富内涵。 相似文献
70.