全文获取类型
收费全文 | 509篇 |
免费 | 99篇 |
国内免费 | 93篇 |
专业分类
航空 | 443篇 |
航天技术 | 131篇 |
综合类 | 73篇 |
航天 | 54篇 |
出版年
2024年 | 2篇 |
2023年 | 8篇 |
2022年 | 13篇 |
2021年 | 22篇 |
2020年 | 23篇 |
2019年 | 21篇 |
2018年 | 26篇 |
2017年 | 21篇 |
2016年 | 39篇 |
2015年 | 23篇 |
2014年 | 39篇 |
2013年 | 40篇 |
2012年 | 48篇 |
2011年 | 61篇 |
2010年 | 46篇 |
2009年 | 44篇 |
2008年 | 35篇 |
2007年 | 29篇 |
2006年 | 33篇 |
2005年 | 37篇 |
2004年 | 20篇 |
2003年 | 14篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 9篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
排序方式: 共有701条查询结果,搜索用时 15 毫秒
141.
《中国航空学报》2016,(6):1749-1761
Air traffic flow management (ATFM) is a collaborative process between the airspace provider and the airspace users. The result of the collaboration should be an outcome that maxi-mizes the utility of the system without excessively penalizing any of the agents. This paper develops a discrete-event simulation model which consists of aggregate departure/arrival airports, flight routes, and sectors for evaluating the alternative collaborative route selection strategy. Given the different perspectives from air traffic control center (ACC) and airlines, eight performance-metrics and five alternative route selection strategies represent the past, current and proposed air traffic flow management operations that were evaluated. The Monte Carlo method combined with the Optimal Computing Budget Allocation (OCBA) simulation optimization technique is employed to assess the performance of different strategies. A case study of the upper air routes in central and southern China shows that the proposed model can be readily implemented to simulate different kinds of air traffic flow management strategies and predict the effect of changes on the airspace sys-tem. It also shows that the proposed alternative collaborative route selection strategy is an effective way in alleviating the en-route traffic congestion. 相似文献
142.
143.
小展弦比飞翼亚、跨、超声速支撑干扰研究 总被引:1,自引:0,他引:1
通过数值模拟方法研究了小展弦比飞翼标模在0.6、0.9、1.5三个典型马赫数下的支撑干扰特性,分别考虑了近场尾部外形局部畸变和尾支杆干扰及远场风洞中部支架干扰,并基于表面压力系数差异为准则尝试对近场干扰量进行分解。研究得到如下结论:马赫数0.6时,远场支撑阻力系数和俯仰力矩系数的干扰量约占总支撑干扰量的30%,升力系数约占20%;马赫数0.9、迎角2°时,阻力系数远场支撑干扰量占总支撑干扰量的40%,迎角18°时,远场支撑干扰使得涡破裂位置提前;马赫数1.5时,远场支撑干扰可以忽略;基于表面压力系数差异将支撑干扰量分解的方法在亚声速支撑干扰前传明显时不适用,在马赫数0.9、迎角2°时求得近场支撑干扰使得马赫数减小约0.02,迎角减小约0.1°,马赫数1.5时用此法求得马赫数和迎角的干扰量均约等于0。 相似文献
144.
根据民机张线测力试验的特殊要求,研制了一台套筒结构形式的张线天平。详细介绍了该天平在研制中遇到的难点、关键技术的解决措施以及研制的结果。天平元件布置在58mm的外套筒上,内杆直径为44mm,外套筒和内杆通过楔块焊接在一起。法向力、俯仰力矩和滚转力矩为拉压变形,横向力和偏航力矩为"S"形变形,轴向力为弯曲变形,元件支撑部分受拉压变形且刚度较强。通过对天平进行有限元分析,在法向力和俯仰力矩作用下,得出的应变结果与实际输出基本吻合。风洞试验结果表明:天平设计合理,天平外套筒、内杆及张线支撑系统刚度好,天平各分量测量精度高。 相似文献
145.
Evan A. Thomas Mark M. Weislogel David M. Klaus 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
It is well recognized that water handling systems used in a spacecraft are prone to failure caused by biofouling and mineral scaling, which can clog mechanical systems and degrade the performance of capillary-based technologies. Long duration spaceflight applications, such as extended stays at a Lunar Outpost or during a Mars transit mission, will increasingly benefit from hardware that is generally more robust and operationally sustainable over time. 相似文献
146.
Lu Zhong Sun Youchao 《中国航空学报》2007,20(5):402-407
分析了产品维修性影响属性,给出了维修性属性值与权重的确定方法;提出了基于相对接近度的维修性模糊评价方法。以虚拟环境下产品维修过程为研究对象,在分析产品各可更换单元的维修作业的基础上,建立了产品维修性评价模型。最后结合民机主起落架系统给出了应用实例,结果表明该模型适用于产品维修性的定性评价并且能够支持维修性并行设计。 相似文献
147.
从工程应用角度基于IPT工作模式,建立详细初步设计阶段以电子样机、虚拟仿真技术等为手段,同步开展使用与维修保障设计分析的流程和方法。以某型飞机舵机A为实例,对建立的方法进行应用,实践表明,建立的方法适用、有效、符合工程实际。该方法的建立,将对详细初步设计阶段一级IPT成员同步开展使用与维修保障设计、分析工作提供有力的技术支撑,对提高军用飞机使用与维修保障设计水平具有重要意义。 相似文献
148.
149.
150.
A.A. Tikhomirov Yu.A. Kudenko S.A. Ushakova L.S. Tirranen I.A. Gribovskaya J.-B. Gros Ch. Lasseur 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
To close mass exchange loops in bioregenerative life support systems more efficiently, researchers of the Institute of Biophysics SB RAS (Krasnoyarsk, Russia) have developed a procedure of wet combustion of human wastes and inedible parts of plants using H2O2 in alternating electromagnetic field. Human wastes pretreated in this way can be used as nutrient solutions to grow plants in the phototrophic unit of the LSS. The purpose of this study was to explore the possibilities of using human wastes oxidized to different degrees to grow plants cultivated on the soil-like substrate (SLS). The treated human wastes were analyzed to test their sterility. Then we investigated the effects produced by human wastes oxidized to different degrees on growth and development of wheat plants and on the composition of microflora in the SLS. The irrigation solution contained water, substances extracted from the substrate, and certain amounts of the mineralized human wastes. The experiments showed that the human wastes oxidized using reduced amounts of 30% H2O2: 1 ml/g of feces and 0.25 ml/ml of urine were still sterile. The experiments with wheat plants grown on the SLS and irrigated by the solution containing treated human wastes in the amount simulating 1/6 of the daily diet of a human showed that the degree of oxidation of human wastes did not significantly affect plant productivity. On the other hand, the composition of the microbiota of irrigation solutions was affected by the oxidation level of the added metabolites. In the solutions supplemented with partially oxidized metabolites yeast-like microscopic fungi were 20 times more abundant than in the solutions containing fully oxidized metabolites. Moreover, in the solutions containing incompletely oxidized human wastes the amounts of phytopathogenic bacteria and denitrifying microorganisms were larger. Thus, insufficiently oxidized sterile human wastes added to the irrigation solutions significantly affect the composition of the microbiological component of these solutions, which can ultimately unbalance the system as a whole. 相似文献