全文获取类型
收费全文 | 10587篇 |
免费 | 2156篇 |
国内免费 | 1973篇 |
专业分类
航空 | 7234篇 |
航天技术 | 2527篇 |
综合类 | 1575篇 |
航天 | 3380篇 |
出版年
2024年 | 34篇 |
2023年 | 105篇 |
2022年 | 272篇 |
2021年 | 335篇 |
2020年 | 392篇 |
2019年 | 264篇 |
2018年 | 295篇 |
2017年 | 351篇 |
2016年 | 339篇 |
2015年 | 467篇 |
2014年 | 659篇 |
2013年 | 695篇 |
2012年 | 792篇 |
2011年 | 764篇 |
2010年 | 902篇 |
2009年 | 818篇 |
2008年 | 785篇 |
2007年 | 740篇 |
2006年 | 639篇 |
2005年 | 547篇 |
2004年 | 383篇 |
2003年 | 398篇 |
2002年 | 391篇 |
2001年 | 389篇 |
2000年 | 364篇 |
1999年 | 399篇 |
1998年 | 315篇 |
1997年 | 285篇 |
1996年 | 263篇 |
1995年 | 206篇 |
1994年 | 199篇 |
1993年 | 189篇 |
1992年 | 153篇 |
1991年 | 149篇 |
1990年 | 122篇 |
1989年 | 110篇 |
1988年 | 80篇 |
1987年 | 50篇 |
1986年 | 33篇 |
1985年 | 13篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1969年 | 1篇 |
1900年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
A Novel Onboard-gateway-based Mechanism to Improve TCP Performance in Aeronautical Satellite Networks 总被引:1,自引:1,他引:0
GU Ming ZHANG Jun 《中国航空学报》2007,20(3):260-265
The IP-based networks on aircraft serve to support Internet services via satellites. However, in aeronautical satellite hybrid net- works,the TCP protocol performance often deteriorates due to improper decreases and slow recovery of the congestion window. This paper proposes a window size determination and notification mechanism, onboard-gateway-based mechanism (OGBM), which is based on the onboard gateway in the networks on aircraft. A cross-layer approach is adopted by the onboard gateway to obtain the satellite link bandwidth information. And then, by the gateway, through changing the receiver’s advertised window field in ACK packets, TCP sources are notified of the window size of each TCP source calculated on the ground of bandwidth delay product and flow numbers. The mechanism is able to avoid improper changes of TCP window and serve multiple users. Simulation results show that the mechanism with the fairness index close to 1 improves TCP performance in aeronautical satellite networks. 相似文献
52.
53.
项目教学法在《微机系统实现与维护》课程教学中的应用探索 总被引:1,自引:0,他引:1
项目教学法突破传统的教学模式,在参与项目完成的过程中学生能更好、更快地掌握所学知识,学习的积极性和主动性大大提高。本文将项目教学法的学习模式引入到高职高专的《微机系统实现与维护》课程教学中,对如何把理论与实践有机地结合,如何提高学生的技能水平作了一定的探索。 相似文献
54.
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
55.
企业如何培育忠诚顾客 总被引:1,自引:0,他引:1
马红霞 《郑州航空工业管理学院学报(管理科学版)》2001,19(3):52-56
当今社会,买方市场已然形成,顾客由被动变为主动,地位与作用日益突出,在这种形势下,提升顾客满意度,培养忠诚顾客,日益成为企业的核心任务。本文对顾客满意与顾客忠诚的意义、培育忠诚顾客的途径进行探讨,以期对企业能有所启发。 相似文献
56.
This paper proposes a neural-network current-regulated switching strategy and an intelligent controller for a matrix converter permanent magnet synchronous motor (PMSM) drive system. By using this new switching strategy, the current harmonics of the system are effectively reduced. In addition, by using the intelligent controller, position control of the drive system can be achieved and an adjustable speed range from 1 r/min to 1500 r/min can be obtained. All the current-loop, speed-loop, and position-loop control algorithms are implemented by a 32-bit TMS320C40 digital signal processor. Several experimental results are shown to validate the theoretical analysis 相似文献
57.
Liu S. Singer C.H. Dougal R.A. 《IEEE transactions on aerospace and electronic systems》2006,42(2):612-624
Electric power anomalies or disturbances can disrupt the normal operation of equipment, accelerate aging, or even cause outright failures thus resulting in increased costs of maintenance and reduced system reliability. Past research on the effects caused by power anomalies has been mostly focused on industrial, commercial, or residential systems, or on power distribution equipment. A literature survey reveals that there is no comprehensive review related to low-voltage (LV) power systems and utilization equipment applicable to military combat vehicles, such as aircraft and ships. This paper summarizes the results of a new literature survey that focused on the causes, effects, and mitigation methods for power anomalies typical of LV mobile power systems. Electric power anomaly cost data collected from the literature are also presented, from which the costs of anomalies to the national defense are estimated using some simple rationales. 相似文献
58.
数据采集系统的总体评价 总被引:5,自引:0,他引:5
从性能指标出发,综述了数据采集系统总结评价技术的发展状况。并提出了对数据采集系统性能指标的两类分类方法 。 相似文献
59.
冯增才 《中国民航学院学报》1996,14(3):63-68
简要介绍了美国UNISYS公司1100、2200系列中型计算机上符号流生成器的使用,并用它编制了一些常用的运行流,简化了用户的上机操作,提高了上机效率。 相似文献
60.