全文获取类型
收费全文 | 6471篇 |
免费 | 1169篇 |
国内免费 | 1250篇 |
专业分类
航空 | 4209篇 |
航天技术 | 1721篇 |
综合类 | 708篇 |
航天 | 2252篇 |
出版年
2024年 | 43篇 |
2023年 | 188篇 |
2022年 | 237篇 |
2021年 | 334篇 |
2020年 | 303篇 |
2019年 | 346篇 |
2018年 | 361篇 |
2017年 | 324篇 |
2016年 | 400篇 |
2015年 | 387篇 |
2014年 | 560篇 |
2013年 | 423篇 |
2012年 | 493篇 |
2011年 | 519篇 |
2010年 | 403篇 |
2009年 | 388篇 |
2008年 | 404篇 |
2007年 | 388篇 |
2006年 | 333篇 |
2005年 | 300篇 |
2004年 | 261篇 |
2003年 | 238篇 |
2002年 | 178篇 |
2001年 | 169篇 |
2000年 | 142篇 |
1999年 | 128篇 |
1998年 | 121篇 |
1997年 | 80篇 |
1996年 | 58篇 |
1995年 | 55篇 |
1994年 | 56篇 |
1993年 | 50篇 |
1992年 | 41篇 |
1991年 | 39篇 |
1990年 | 45篇 |
1989年 | 37篇 |
1988年 | 29篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 16篇 |
1984年 | 4篇 |
排序方式: 共有8890条查询结果,搜索用时 15 毫秒
51.
跨大气层和空间区域飞行器的液体推进剂管理 总被引:1,自引:0,他引:1
根据大气层飞行环境与机动飞行特点,以及空间飞行环境与液体推进剂特点,分析了跨大气层和空间区域飞行器的保证重力场和失重状态下均无夹气液体输送、控制液体推进剂质心位移、剩余推进剂空间排放和重复使用等液体推进剂管理技术要求。阐述了相应的关键技术,如包括无夹气输送、液体质心位移控制、失重状态下的流体动力、参数确定和结构设计等管理模式确定,以及包括模型参数确定、模型、状态模拟和验证等的管理模式试验。 相似文献
52.
53.
Africano John Schildknecht Thomas Matney Mark Kervin Paul Stansbery Eugene Flury Walter 《Space Debris》2000,2(4):357-369
Since more than 10 years there is evidence that small-size space debris is accumulating in the geosynchronous orbit (GEO), probably as the result of breakups. Two break-ups have been reported in GEO. The 1978 break-up of an EKRAN 2 satellite, SSN 10365, was identified in 1992, and in 1992 a Titan 3C Transtage, SSN 3432, break-up produced at least twenty observable pieces. Subsequently several nations performed optical surveys of the GEO region in the form of independent observation campaigns. Such surveys suffer from the fact that the field of view of optical telescopes is small compared with the total area covered by the GEO ring. As a consequence only a small volume of the orbital element-magnitude-space is covered by each individual survey. Results from these surveys are thus affected by observational biases and therefore difficult to compare. This paper describes the development of a common search strategy to overcome these limitations. The strategy optimizes the sampling for objects in orbits similar to the orbits of the known GEO population but does not exclude the detection of objects with other orbital planes. A properly designed common search strategy clearly eases the comparison of results from different groups and the extrapolation from the sparse (biased) samples to the entire GEO environment. 相似文献
54.
55.
Tether Satellite System Collision Study 总被引:1,自引:0,他引:1
A study was performed to determine the probability of collision with resident space objects and untrackable debris for the tether component of the Tethered Satellite System (TSS) after it broke away from the Space Shuttle orbiter (mission STS-75) in February 1996. Both an analytical and a numerical approach were used in this study, and the results obtained with these two methods were found to be in good agreement. These results show that the deployed tether is expected to have been impacted by several particles 0.1mm or larger in size. The probability of collision with objects 10cm in size or larger was on the order of 10–3 per month. Since the severed tether reentered within one month after deployment, the collision hazard to other objects while in orbit was small. The analytical methods used in this study are useful for tether collision evaluations in general. 相似文献
56.
本文通过对《宇航学报》1981~1988年322篇论文中2466条参考文献的统计分析,得出以下结论,(a)宇航科学的文献情报源重在期刊类文献。(b)以《宇航学报》、《航空学报》、《AIAA,Jourual》等六种期刊类文献为重点文献。(c)中文的引文作者和论文作者相对集中。(d)期刊类文献的半衰期为8~10年。 相似文献
57.
58.
S. Mereghetti D. Gtz J. Borkowski 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,34(12):2729-2733
The INTEGRAL satellite has been successfully launched in October 2002 and has recently started its operational phase. The INTEGRAL burst alert system (IBAS) will distribute in real time the coordinates of the gamma ray bursts (GRBs) detected with INTEGRAL. After a brief introduction on the INTEGRAL instruments, we describe the main IBAS characteristics and report on the initial results. During the initial performance and verification phase of the INTEGRAL mission, which lasted about two months, two GRBs have been localized with accuracy of 2–4 arcmin. These observations have allowed us to validate the IBAS software, which is now expected to provide quick (few seconds delay) and precise (few arcmin) localization for 10–15 GRBs per year. 相似文献
59.
依据两步映射法和体纹理的思想,将曲面纹理的映射过程分为非实时映射和实时查询两个部分,提出一种能实时显示曲面纹理的方法及相应的抗混叠措施,最后,结合一种快速浓淡算法,为曲面纹理叠加光照效果,生成了很逼真的图象。 相似文献
60.
INS/GPS组合导航系统的容错研究 总被引:1,自引:0,他引:1
本文研究了INS/GPS组合导航系统的容错问题,并提出了一个两级故障检测及分离方案。通过采用该方案,INS/GPS组合导航系统将具有较高的容错能力,并能为用户提供连续、精确的导航信息。 相似文献