全文获取类型
收费全文 | 459篇 |
免费 | 160篇 |
国内免费 | 61篇 |
专业分类
航空 | 114篇 |
航天技术 | 272篇 |
综合类 | 18篇 |
航天 | 276篇 |
出版年
2024年 | 1篇 |
2023年 | 15篇 |
2022年 | 24篇 |
2021年 | 39篇 |
2020年 | 26篇 |
2019年 | 48篇 |
2018年 | 36篇 |
2017年 | 30篇 |
2016年 | 33篇 |
2015年 | 25篇 |
2014年 | 82篇 |
2013年 | 51篇 |
2012年 | 45篇 |
2011年 | 38篇 |
2010年 | 39篇 |
2009年 | 29篇 |
2008年 | 32篇 |
2007年 | 26篇 |
2006年 | 14篇 |
2005年 | 10篇 |
2004年 | 7篇 |
2003年 | 9篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有680条查询结果,搜索用时 437 毫秒
481.
J. Semkova R. Koleva St. Maltchev N. Kanchev V. Benghin I. Chernykh V. Shurshakov V. Petrov E. Yarmanova N. Bankov V. Lyagushin M. Goranova 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
Liulin-5 is a particle telescope developed for the investigation of the radiation environment within the Russian spherical tissue-equivalent phantom on the International Space Station (ISS). Liulin-5 experiment is conducted aboard the Russian segment of ISS since 28 June 2007 as an adherent part of the international project MATROSHKA-R. The main objective of Liulin-5 experiment is to study the depth-dose distribution of the different components of the orbital radiation field in a human phantom. Additional objectives are mapping of the radiation environment in the phantom and its variations with time and orbital parameters (such as solar cycle, solar flare events, inclination and altitude). Liulin-5 is an active instrument, capable to provide real-time radiation data for the particle flux and dose rates, energy deposition and LET spectra. Data are recorded automatically on memory cards, periodically transported to ground by returning vehicles. In this report we present some first results from data analysis including energy deposition spectra, absorbed dose, dose rate and flux distribution measured simultaneously at 3 different depths of phantom’s radial channel and linear energy transfer (LET) spectrum. Data discussed are for the period July 2007–April 2008. 相似文献
482.
考虑EKF滤波方法的线性化过程对估计误差的影响,提出一种非线性不确定系统的鲁棒H∞滤波方法.基于H∞理论,该算法将滤波模型和观测模型在线性化过程中所产生的误差作为系统的不确定部分,力求此误差对导航精度的影响最小,并且利用李亚普诺夫方法证明了该滤波算法的稳定性.利用所提算法对月球环绕段自主导航系统进行滤波估计,仿真结果证实了算法的有效性. 相似文献
483.
在基于视线矢量观测的自主光学导航系统中,观测模型的非线性是影响导航精度的一个重要因素。通过定量计算观测模型的非线性强度,研究了视线测量光学导航系统测量模型的选取问题。文章基于透射投影模型的共线性方程,给出了两种视线矢量观测模型的导航测量方程及测量噪声统计特性。在扩展卡尔曼滤波框架内深入分析了观测模型非线性对导航性能的影响。并利用微分几何非线性曲率测量理论,定量比较了两种观测模型的非线性强度。最后以基于视线矢量观测的姿态确定系统为例,仿真验证了非线性曲率测量与导航性能的一致性,结果表明基于单位矢量观测模型的光学导航系统具有更高的估计精度和更快的收敛特性。 相似文献
484.
钻取采样作为一种获取深层月壤的有效方式被应用于地外天体采样任务。不同于地面钻探,无人月面钻取采样面临诸多技术难点,例如遥操作信号延迟、探测器传感资源有限、缺乏采样点地质信息以及月壤力学特性复杂等。为保证采样任务高效可靠地执行,采样装置需充分利用有限的探测器硬件资源,依据钻进工况实时调整钻进工艺参数,对未知的钻进环境具有适应能力。提出一种基于可钻性在线辨识的月面钻进控制方法。利用可钻性指标综合评价当前对象的钻进难易程度,采用模式识别方法辨识钻进对象的可钻性等级并实时匹配最优的钻进工艺参数,从而实现钻进过程的智能控制。为验证所提出控制方法的有效性,开展了模拟月壤月岩交替布置的钻进试验研究。试验结果表明:该方法能够有效控制钻进负载。 相似文献
485.
486.
总结了近20年来火星探测的重要发现以及生命、气候和地质3个方面尚未解决的关键科学问题;介绍了美国国家航空航天局(NASA)2020火星探测任务的科学目标、科学载荷和着陆区选择的工程条件限制,并重点分析了经过3次着陆区选择研讨会,上百位行星科学家投票选取的排名前3的预选着陆区的地质情况。在此基础上,提出了对我国2020年火星任务的着陆探测部分的一些思考,并根据不同的任务目标(聚焦生命、气候和地质问题;支持载人火星探测的资源勘察;工程技术验证)提出了3个候选着陆区。 相似文献
487.
Kyeong Ja Kim Joo-Hee Lee Haingja Seo Gwanghyeok Ju Sang-Ryool Lee Gi-Hyuk Choi Eun-Sup Sim Tai Sik Lee 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Korea is planning a series of lunar space programs in 2020 starting with a lunar orbiter and a lander with a rover. Compared to other countries, Korea has a relatively brief history in space and planetary sciences. With the expected Korean missions on the near-term horizon and the relatively few Korean planetary scientists, Korea Institute of Geoscience and Mineral Resources (KIGAM) has established a new planetary research group focusing on development of prospective lunar instruments, analysis of the publicly available planetary data of the Moon, organizing nationwide planetary workshops, and initiating planetary educational programs with academic institutions. Korea has also initiated its own rocket development program, which could acquire a rocket-launch capability toward the Korean lunar mission. For the prospective Korea’s lunar science program, feasibility studies for some candidate science payloads have been started since 2010 for an orbiter and a lander. The concept design of each candidate instrument has been accomplished in 2012. It is expected that the development of science payloads may start by 2014 as Phase A. Not only developing hardware required for the lunar mission but also educational activities for young students are high priorities for Korea. The new plan of the Korean lunar mission can be successfully accomplished with international cooperative outreach programs in conjunction with internationally accessible planetary data system (PDS). This paper introduces the KIGAM’s international cooperative planetary research and educational programs and also summarizes other nationwide new developments for Korean lunar research projects at Kyung Hee University and Hanyang University. 相似文献
488.
489.
L. A. Mcfadden M. K. Rountree-Brown E. M. Warner S. A. M Claughlin J. M. Behne J. D. Ristvey S. Baird-Wilkerson D. K. Duncan S. D. Gillam G. H. Walker K. J. Meech 《Space Science Reviews》2005,117(1-2):373-396
The Deep Impact mission’s Education and Public Outreach (E/PO) program brings the principles of physics relating to the properties
of matter, motions and forces and transfer of energy to school-aged and public audiences. Materials and information on the
project web site convey the excitement of the mission, the principles of the process of scientific inquiry and science in
a personal and social perspective. Members of the E/PO team and project scientists and engineers, share their experiences
in public presentations and via interviews on the web. Programs and opportunities to observe the comet before, during and
after impact contribute scientific data to the mission and engage audiences in the mission, which is truly an experiment. 相似文献
490.
许海峰 《民用飞机设计与研究》2011,(2):52-55
持续适航文件和其他技术出版物是由飞机制造商提供的保持飞机固有安全性水平的重要资料。对持续适航文件编制过程中影响文件质量的人为因素问题进行了分析,并对如何提高文件质量提出了建议。 相似文献