全文获取类型
收费全文 | 105篇 |
免费 | 0篇 |
国内免费 | 3篇 |
专业分类
航空 | 43篇 |
航天技术 | 25篇 |
航天 | 40篇 |
出版年
2021年 | 4篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 9篇 |
2012年 | 6篇 |
2011年 | 5篇 |
2010年 | 7篇 |
2009年 | 5篇 |
2008年 | 5篇 |
2007年 | 7篇 |
2006年 | 6篇 |
2005年 | 6篇 |
2004年 | 3篇 |
2003年 | 6篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1980年 | 2篇 |
1975年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有108条查询结果,搜索用时 390 毫秒
31.
The Atacama Desert is one of the driest environments on Earth, and has been so for over 200,000 years. Previous reports have suggested that surprisingly low numbers of culturable bacteria, counted as biomass or species diversity, are present in Atacama sands collected from the most hyperarid regions. In previous studies, the presence of eukaryotic organisms was not discussed. In this report, we describe a method of direct plating onto rich media that resulted in culturing a range of fungi from Atacama samples. All fungi identified in this preliminary survey are spore-forming saprobes that are readily dispersed by wind, a likely mechanism that accounts for their presence in the central Atacama Desert. 相似文献
32.
33.
34.
Requirements are rarely static, and are ever more likely to evolve as the development time of a system stretches out and its service life increases. In this paper, we discuss the evolution of requirements for the US spacesuit, the extravehicular mobility unit (EMU), as a case study to highlight the need for flexibility in system design. We explore one fundamental environmental change, using the Space Shuttle EMU aboard the International Space Station, and the resulting EMU requirement and design changes. The EMU, like other complex systems, faces considerable uncertainty during its service life. Changes in the technical, political, or economic environment cause changes in requirements, which in turn necessitate design modifications or upgrades. We make the case that flexibility is a key attribute that needs to be embedded in the design of long-lived, complex systems to enable them to efficiently meet the inevitability of changing requirements after they have been fielded. 相似文献
35.
Spatial Reference Systems 总被引:1,自引:0,他引:1
Spatial Cognition and Computation - 相似文献
36.
37.
J.Steven Newman 《Acta Astronautica》2001,48(5-12)
38.
Gale Paulsen Kris Zacny Christopher B. Dreyer Attila Szucs Matt Szczesiak Chris Santoro Jack Craft Magnus Hedlund John Skok 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
We have developed a rock grinding and polishing mechanism for in situ planetary exploration based on abrasive disks, called Grinding Rocks Into Thin Sections (GRITS). Performance characteristics and design considerations of GRITS are presented. GRITS was developed as part of a broader effort to develop an in situ automated rock thin section (ISARTS) instrument. The objective of IS-ARTS was to develop an instrument capable of producing petrographic rock thin sections on a planetary science spacecraft. GRITS may also be useful to other planetary science missions with in situ instruments in which rock surface preparation are necessary. 相似文献
39.
The utilization of pressure vessels in aerospace applications is manifold.In this work,fnite element analysis(FEA)has been carried out using ANSYS software package with 2D axisymmetric model to access the failure pressure of cylindrical pressure vessel made of ASTM A36 carbon steel having weld-induced residual stresses.To fnd out the effect of residual stresses on failure pressure,frst an elasto-plastic analysis is performed to fnd out the failure pressure of pressure vessel not having residual stresses.Then a thermo-mechanical fnite element analysis is performed to assess the residual stresses developed in the pressure vessel during welding.Finally one more elasto-plastic analysis is performed to assess the effect of residual stresses on failure pressure of the pressure vessel having residual stresses.This analysis indicates reduction in the failure pressure due to unfavorable residual stresses. 相似文献
40.
Hawkins S. Edward Darlington E. Hugo Murchie Scott L. Peacock Keith Harris Terry J. Hersman Christopher B. Elko Michael J. Prendergast Daniel T. Ballard Benjamin W. Gold Robert E. Veverka Joseph Robinson Mark S. 《Space Science Reviews》1997,82(1-2):31-100
A multispectral imager has been developed for a rendezvous mission with the near-Earth asteroid, 433 Eros. The Multi-Spectral Imager (MSI) on the Near-Earth Asteroid Rendezvous (NEAR) spacecraft uses a five-element refractive optical telescope, has a field of view of 2.93 × 2.25°, a focal length of 167.35 mm, and has a spatial resolution of 16.1 × 9.5 m at a range of 100 km. The spectral sensitivity of the instrument spans visible to near infrared wavelengths, and was designed to provide insight into the nature and fundamental properties of asteroids and comets. Seven narrow band spectral filters were chosen to provide multicolor imaging and to make comparative studies with previous observations of S asteroids and measurements of the characteristic absorption in Fe minerals near 1 µm. An eighth filter with a much wider spectral passband will be used for optical navigation and for imaging faint objects, down to visual magnitude of +10.5. The camera has a fixed 1 Hz frame rate and the signal intensities are digitized to 12 bits. The detector, a Thomson-CSF TH7866A Charge-Coupled Device, permits electronic shuttering which effectively varies the dynamic range over an additional three orders of magnitude. Communication with the NEAR spacecraft occurs via a MIL-STD-1553 bus interface, and a high speed serial interface permits rapid transmission of images to the spacecraft solid state recorder. Onboard image processing consists of a multi-tiered data compression scheme. The instrument was extensively tested and calibrated prior to launch; some inflight calibrations have already been completed. This paper presents a detailed overview of the Multi-Spectral Imager and its objectives, design, construction, testing and calibration. 相似文献