全文获取类型
收费全文 | 691篇 |
免费 | 344篇 |
国内免费 | 107篇 |
专业分类
航空 | 793篇 |
航天技术 | 163篇 |
综合类 | 39篇 |
航天 | 147篇 |
出版年
2024年 | 7篇 |
2023年 | 19篇 |
2022年 | 31篇 |
2021年 | 34篇 |
2020年 | 29篇 |
2019年 | 29篇 |
2018年 | 20篇 |
2017年 | 26篇 |
2016年 | 41篇 |
2015年 | 31篇 |
2014年 | 69篇 |
2013年 | 68篇 |
2012年 | 54篇 |
2011年 | 49篇 |
2010年 | 25篇 |
2009年 | 24篇 |
2008年 | 23篇 |
2007年 | 43篇 |
2006年 | 34篇 |
2005年 | 39篇 |
2004年 | 31篇 |
2003年 | 36篇 |
2002年 | 24篇 |
2001年 | 27篇 |
2000年 | 31篇 |
1999年 | 38篇 |
1998年 | 57篇 |
1997年 | 33篇 |
1996年 | 29篇 |
1995年 | 23篇 |
1994年 | 36篇 |
1993年 | 15篇 |
1992年 | 19篇 |
1991年 | 14篇 |
1990年 | 19篇 |
1989年 | 8篇 |
1988年 | 3篇 |
1987年 | 4篇 |
排序方式: 共有1142条查询结果,搜索用时 31 毫秒
1.
《中国航空学报》2020,33(2):634-663
The determination of optimal aerial transport networks and their associated flight frequencies is crucial for the strategic planning of airlines, as well as for carrying out market research, to establish target markets, and for aircraft and crew rostering. In addition, optimum airplane types for the selected networks are crucial to improve revenue and to provide reduced operating costs. The present study proposes an innovative approach to determine the optimal aerial transport network simultaneously with the determination of the optimum fleet for that network, composed of three types of airplanes (network and vehicle integrated design). The network profit is maximized. The passenger’s demands between the airports are determined via a gravitational model. An embedded linear programming solution is responsible for obtaining potential optimal network configurations. The optimum fleet combination is determined from a database of candidate aircraft designs via genetic algorithm. A truly realistic airplane representation is made possible thanks to accurate surrogate models for engine and aerodynamics is adopted. An accurate engine deck encompassing a compression map and an innovative engine weight calculation besides an aerodynamical artificial neural network module enable a high degree of accuracy for the mission analysis. The proposed methodology is applied to obtain the optimum network comprised of twenty main Brazilian airports and corresponding fleet. 相似文献
2.
对无动力J—7LP动力学缩比模型进行了遥控试飞,以研究其失速尾旋特性,全偏平尾和方向舵可使模型进八尾旋,舵面全回中即可从各种尾旋中改出。偏转副翼对尾旋特性有明显的影响。 相似文献
3.
The architecture of digital sheet metal manufacturing system is proposed based on the classification of sheet metal manufacturing information.The essence of digital manufacturing is the definition,management and transfer of information,and the key technologies are brought forward and described.It is pointed out that knowledge-based manufacturing elements design is necessary to make digital technology efficient.The management of all kinds of sheet metal manufacturing element information is to build single source of manufacturing data.Multi-state model-based digital transfer and coordination method is designed to provide a foundation for digital manufacturing of aircraft sheet metal part.The application of digital sheet metal manufacturing is exemplified with an aircraft sheet metal part.The application result is compared to that of the traditional analog transfer technology.It is shown that the developed technology can improve part quality,shorten manufacturing time and lower manufacturing cost. 相似文献
4.
5.
6.
提出了探空火箭动力系统设计参数优化计算方法.综合考虑了动力系统与火箭外弹道之间的关系.在给定有效载荷、最高射高的条件下,选取动力系统的设计参数使火箭的起飞质量最小.选用了增广拉格朗日法约束优化技术和牛顿迭代法求解数学模型.计算结果表明,该计算方法是合理的. 相似文献
7.
8.
空间小推力发动机推力室喷注器的设计与身部冷却问题 总被引:3,自引:0,他引:3
介绍了空间小推力双组元液体火箭发动机推力空头部喷注器设计的某些特点和身部冷却的一些问题,具体地讨论了几种喷注器设计方案和简述了身部液膜/辐射冷却的机制,并给出某些情况下估算壁温的方法。 相似文献
9.
10.