全文获取类型
收费全文 | 1366篇 |
免费 | 176篇 |
国内免费 | 234篇 |
专业分类
航空 | 751篇 |
航天技术 | 562篇 |
综合类 | 130篇 |
航天 | 333篇 |
出版年
2024年 | 6篇 |
2023年 | 17篇 |
2022年 | 35篇 |
2021年 | 51篇 |
2020年 | 59篇 |
2019年 | 50篇 |
2018年 | 66篇 |
2017年 | 49篇 |
2016年 | 68篇 |
2015年 | 86篇 |
2014年 | 99篇 |
2013年 | 103篇 |
2012年 | 103篇 |
2011年 | 116篇 |
2010年 | 111篇 |
2009年 | 119篇 |
2008年 | 86篇 |
2007年 | 74篇 |
2006年 | 60篇 |
2005年 | 54篇 |
2004年 | 42篇 |
2003年 | 34篇 |
2002年 | 40篇 |
2001年 | 39篇 |
2000年 | 24篇 |
1999年 | 20篇 |
1998年 | 22篇 |
1997年 | 14篇 |
1996年 | 24篇 |
1995年 | 16篇 |
1994年 | 22篇 |
1993年 | 18篇 |
1992年 | 17篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 10篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1984年 | 9篇 |
排序方式: 共有1776条查询结果,搜索用时 171 毫秒
891.
In a pico-satellite with small volume, measurements from on-board three-axis magnetometer (TAM) are not accurate, as it can be easily disturbed by other electronic systems. To improve its accuracy, a scheme of compensation methods is introduced in this article. The scheme is based on an improved measurement model of pico-satellite TAM, and it mainly consists of three steps. First, in satellite design stage, several techniques are recommended to simplify the afterwards compensations. Then after satellite assembly, TAM ground tests and pre-launch calibration with least-square batch filter are introduced to improve magnetometer performance. At the end, a post-launch calibration with unscented Kalman filter (UKF) is implemented with in-orbit data. The compensation scheme is used in the development of Chinese pico-satellite ZDPS-1A made by Zhejiang University. Results show that with the introduced compensation scheme, the maximum error of ZDPS-1A TAM can be reduced from 80 mG to 6 mG (1 G=10-4 T). 相似文献
892.
横Π型梁在风洞应变天平阻力结构上的应用 总被引:1,自引:0,他引:1
主要通过对比传统T型梁和横Π型梁,对风洞应变天平的阻力测量梁进行了分析,根据分析结果提出了传统的横Π型阻力测量梁的改进方式,并通过有限元分析软件进行了优化分析,改进后的横Π型阻力测量梁降低了升力对阻力的干扰,并有利于提高天平阻力分量的稳定性。该测量梁结构应用到了某型飞机高速风洞试验测力天平上,天平静态校准结果与理论分析结果吻合,风洞试验时天平状态良好、性能稳定。 相似文献
893.
A three-dimensional infrared radiation code for exhaust system was developed by the finite volume method coupled with narrow band k-distribution in non-gray absorbing-emitting media. The final infrared signature had considered the atmosphere effect, and the simulation values were favorably consistent with testing ones. The results indicate that the relative errors considering the effect of atmosphere compared with that of the contrary condition reduce by 31%, it shows that when simulating the infrared radiation of the target which is received by the infrared detectors, even the calculation band is in atmospheric windows 3~5 μm, the effect of atmospheric transmission on infrared signature of the target should not be neglected. 相似文献
894.
895.
在简述风洞天平校准原理的基础上,归纳分析了国外风洞天平校准台的主要类型及特点;阐述了美欧在风洞天平校准技术方面的发展理念和开展的关键技术研究。 相似文献
896.
简述了美国航空航天协会AIAA的《风洞试验内式应变天平校准和使用》推荐标准制订的目的、过程和主要涵盖的内容;分析了该标准所反映出的国外风洞天平校准技术发展的特点;阐述了该天平校准标准对我国天平技术发展的启示,为国内风洞天平技术的创新发展提供参考。 相似文献
897.
898.
基于ProE的航天器三维屏蔽与辐射剂量评估方法研究 总被引:3,自引:0,他引:3
为准确评估结构异常复杂的航天器内部遭遇的辐射剂量,本文将直线近似原理和ProE工程软件相结合,自主开发了一种新型的航天器三维屏蔽与辐射剂量评估方法。利用本方法对立方体、球、平板等简单几何体内部的屏蔽厚度和辐射剂量进行了分析计算,计算结果表明基于ProE的三维屏蔽与辐射剂量计算方法是可靠的。结构复杂程度相当于中等规模航天器的模型计算结果表明,本方法能够较高效的分析评估复杂航天器内部遭遇的屏蔽厚度和辐射剂量。
相似文献
相似文献
899.
Removing Solar Radiation Based on the Empirical Mode Decomposition Method for Seismo-Ionospheric Anomaly Before the M9.0 Tohoku Earthquake
下载免费PDF全文
![点击此处可从《空间科学学报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The ionospheric effect from solar activity can be seen as the background in the process of detecting the ionospheric precursor prior to strong earthquakes. The ionospheric variation induced by the forthcoming earthquake can be covered by the strong solar background during the period of high solar activity. The issue of how to remove the ionospheric effect from solar radiation is of outstanding significance. In this paper, a method of Empirical Mode Decomposition (EMD) is used to eliminate the solar background. As a case study, the global ionospheric map TEC before the M9.0 Tohoku earthquake on 11 March 2011 is analyzed. After the effect of solar radiation is removed using the EMD method, the precursor of the imminent earthquake is more obvious. The ionospheric anomaly had a local character and only appeared close to the earthquake epicenter while the useful signals were covered by the solar radiation background with traditional method, which implies that the EMD method is effective in eliminating solar radiation background. 相似文献
900.