全文获取类型
收费全文 | 708篇 |
免费 | 232篇 |
国内免费 | 100篇 |
专业分类
航空 | 621篇 |
航天技术 | 118篇 |
综合类 | 85篇 |
航天 | 216篇 |
出版年
2024年 | 7篇 |
2023年 | 19篇 |
2022年 | 47篇 |
2021年 | 58篇 |
2020年 | 42篇 |
2019年 | 34篇 |
2018年 | 42篇 |
2017年 | 58篇 |
2016年 | 46篇 |
2015年 | 56篇 |
2014年 | 51篇 |
2013年 | 59篇 |
2012年 | 62篇 |
2011年 | 49篇 |
2010年 | 51篇 |
2009年 | 56篇 |
2008年 | 67篇 |
2007年 | 43篇 |
2006年 | 50篇 |
2005年 | 45篇 |
2004年 | 18篇 |
2003年 | 14篇 |
2002年 | 28篇 |
2001年 | 16篇 |
2000年 | 9篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有1040条查询结果,搜索用时 15 毫秒
11.
In situ formed TiB2 particle reinforced aluminum matrix composites (TiB2/Al MMCs) have some extraordinary properties which make them be a promising material for high performance aero-engine blade. Due to the influence of TiB2 particles, the machinability is still a problem which restricts the application of TiB2/Al MMCs. In order to meet the industrial requirements, the influence of TiB2 particles on the machinability of TiB2/Al MMCs was investigated experimentally. Moreover, the optimal machining conditions for this kind of MMCs were investigated in this study. The major conclusions are: (1) the machining force of TiB2/Al MMCs is bigger than that of non-reinforced alloy and mainly controlled by feed rate; (2) the residual stress of TiB2/Al MMCs is compressive while that of non-reinforced alloy is nearly neutral; (3) the surface roughness of TiB2/Al MMCs is smaller than that of non-reinforced alloy under the same cutting speed, but reverse result was observed when the feed rate increased; (4) a multi-objective optimization model for surface roughness and material removal rate (MRR) was established, and a set of optimal parameter combinations of the machining was obtained. The results show a great difference from SiC particle reinforced MMCs and provide a useful guide for a better control of machining process of this material. 相似文献
12.
Wilkinson定理是代数特征值问题中的一个经典定理,文章给出了Wilkinson定理的结果中关于扰动矩阵上界的另一种估计形式,并指出该形式对Wilkinson定理具有一定的改进。 相似文献
13.
The emerging new concepts and technologies based on microwave photonics have led to an ever-increasing interest in developing innovative radar systems with a net gain in functionality, bandwidth/resolution, size, mass, complexity and cost when compared with the traditional implementations. This paper describes the techniques de- veloped in the last few years in microwave photonics that might revolutionize the way to design multifunction radar systems, with an emphasis on the recent advances in optoelectronic oscillators (OEOs), arbitrary waveform gener- ation, photonic mixing, phase coding, filtering, beamforming, analog-to-digital conversion, and stable radio-fre- quency signal transfer. Challenges in implementation of these components and subsystems for meeting the technique requirements of the multifunction radar applications are discussed. 相似文献
14.
15.
针对靶场试验跨区域雷达联合参试的特点,结合靶场试验信息实时处理显示需求,分析和比较了高层体系 结构(HLA)和试验训练使能体系结构(TENA)的原理和技术优势,设计了适用于靶场试验的雷达组网信息系统总 体框架,阐述了该系统的组成和功能,为提高靶场综合试验能力做出了探索。 相似文献
16.
17.
18.
19.
20.
讨论了数据挖掘和可视化的关键技术,提出了一种可视化模型的设计方法并设计了一套数据挖掘可视化系统的方案,对提高决策的效率具有重大现实意义。 相似文献