全文获取类型
收费全文 | 246篇 |
免费 | 107篇 |
国内免费 | 55篇 |
专业分类
航空 | 264篇 |
航天技术 | 40篇 |
综合类 | 47篇 |
航天 | 57篇 |
出版年
2024年 | 1篇 |
2023年 | 12篇 |
2022年 | 18篇 |
2021年 | 21篇 |
2020年 | 13篇 |
2019年 | 14篇 |
2018年 | 17篇 |
2017年 | 18篇 |
2016年 | 13篇 |
2015年 | 11篇 |
2014年 | 33篇 |
2013年 | 23篇 |
2012年 | 18篇 |
2011年 | 23篇 |
2010年 | 17篇 |
2009年 | 10篇 |
2008年 | 13篇 |
2007年 | 8篇 |
2006年 | 10篇 |
2005年 | 9篇 |
2004年 | 5篇 |
2003年 | 8篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 8篇 |
1998年 | 15篇 |
1997年 | 12篇 |
1996年 | 9篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1987年 | 1篇 |
排序方式: 共有408条查询结果,搜索用时 781 毫秒
331.
332.
于蓉 《中国民航飞行学院学报》2011,22(3):39-41
航空服务若想在激烈的市场竞争中取胜,将体验融于服务,开发设计出令人难忘的客户体验,无疑将对提升服务质量,保持客户忠诚度起到关键作用。本文从体验与航空服务的互动关系出发,分析了体验在航空服务中的重要作用,探讨了航空服务中体验设计的方法,帮助探寻民航企业体验设计中的重要依托要素。 相似文献
333.
334.
以多舵面组合下的无尾飞翼布局为基础,建立全机的结构动力学有限元模型,进行固有模态分析。对颤振计算方法进行改进,分析了多舵面下的颤振和振动特性,研究了在机身后缘机翼外侧的副翼改成对开式双舵面后无尾飞翼布局的颤振和振动特性,提出了一种建模和计算的方法。 相似文献
335.
336.
空防对抗仿真的情景想定设计 总被引:1,自引:0,他引:1
为使空防对抗仿真更接近实战,对仿真情景想定设计作了改进。将防空区等分成4个扇形区,在确定对突防飞机威胁最大的影响因素的基础上,根据动态规划法得出进袭飞机采用不同航线时防空方不同部署形式的赢得矩阵,并由布朗算法计算该矩阵,得出攻防双方作战方案的选取概率。仿真计算结果表明,该设计方法较合理,避免了仿真的盲目性,对战术仿真有一定的参考价值。 相似文献
337.
Optimization problems are often highly constrained and evolutionary algorithms(EAs)are effective methods to tackle this kind of problems. To further improve search efficiency and convergence rate of EAs, this paper presents an adaptive double chain quantum genetic algorithm(ADCQGA) for solving constrained optimization problems. ADCQGA makes use of doubleindividuals to represent solutions that are classified as feasible and infeasible solutions. Fitness(or evaluation) functions are defined for both types of solutions. Based on the fitness function, three types of step evolution(SE) are defined and utilized for judging evolutionary individuals. An adaptive rotation is proposed and used to facilitate updating individuals in different solutions.To further improve the search capability and convergence rate, ADCQGA utilizes an adaptive evolution process(AEP), adaptive mutation and replacement techniques. ADCQGA was first tested on a widely used benchmark function to illustrate the relationship between initial parameter values and the convergence rate/search capability. Then the proposed ADCQGA is successfully applied to solve other twelve benchmark functions and five well-known constrained engineering design problems. Multi-aircraft cooperative target allocation problem is a typical constrained optimization problem and requires efficient methods to tackle. Finally, ADCQGA is successfully applied to solving the target allocation problem. 相似文献
338.
Vulnerability analysis for airport networks based on fuzzy soft sets: From the structural and functional perspective 总被引:1,自引:0,他引:1
Recently,much attention has been paid to the reliability and vulnerability of critical infrastructure.In air traffic systems,the vulnerability analysis for airport networks can be used to guide air traffic administrations in their prioritization of the maintenance and repair of airports,as well as to avoid unnecessary disturbances in the planning of flight schedules.In this paper,the evaluation methods of airport importance and network efficiency are established.Firstly,the evaluation indices of airport importance are proposed from both the topological and functional perspectives.The topological characteristics come from the structure of airport network and the functional features stem from the traffic flow distribution taking place inside the network.Secondly,an integrated evaluation method based on fuzzy soft set theory is proposed to identify the key airports,which can fuse together importance indices over different time intervals.Thirdly,an airport network efficiency method is established for the purpose of assessing the accuracy of the evaluation method.Finally,empirical studies using real traffic data of US and China’s airport networks show that the evaluation method proposed in this paper is the most accurate.The vulnerability of US and China’s airport networks is compared.The similarities and differences between airport geography distribution and airport importance distribution are discussed here and the dynamics of airport importance is studied as well. 相似文献
339.
为了探索航空发动机空气起动系统的匹配机理,寻找改善全包线内系统性能的技术途径,通过对系统各单元工作特性及相互制约条件的分析,在综合辅助动力装置(APU)、引气管路、调压装置、空气涡轮起动机(ATS)特性计算模型的基础上,发展了一种基于各单元匹配的空气起动系统性能计算方法。该方法能够准确获取系统设计点、各单元特征参数及边界条件,确定APU引气特性、引气管路损失特性、ATS喉道面积和调压装置蝶阀调节规律,进而实现空气起动系统全包线特性计算。利用试验数据对模型进行了校验,结果表明,输出功率计算误差3.5%、引气流量计算误差4%。该模型克服了目前工程上只能单点计算,且需反复迭代的缺陷,为空气起动系统总体性能设计和评估提供了一种有效的分析工具。 相似文献
340.
《中国航空学报》2020,33(10):2510-2526
Due to elimination of horizontal and vertical tails, flying wing aircraft has poor longitudinal and directional dynamic characteristics. In addition, flying wing aircraft uses drag rudders for yaw control, which tends to generate strong three-axis control coupling. To overcome these problems, a flight control law design method that couples the longitudinal axis with the lateral-directional axes is proposed. First, the three-axis coupled control augmentation structure is specified. In the structure, a “soft/hard” cross-connection method is developed for three-axis dynamic decoupling and longitudinal control response decoupling from the drag rudders; maneuvering turn angular rate estimation and subtraction are used in the yaw axis to improve the directional damping. Besides, feedforward control is adopted to improve the maneuverability and control decoupling performance. Then, detailed design methods for feedback and feedforward control parameters are established using eigenstructure assignment and model following technique. Finally, the proposed design method is evaluated and compared with conventional method by numeric simulations. The influences of control derivatives variation of drag rudders on the method are also analyzed. It is demonstrated that the method can effectively improve the dynamic characteristics of flying wing aircraft, especially the directional damping characteristics, and decouple the longitudinal responses from the drag rudders. 相似文献