全文获取类型
收费全文 | 120篇 |
免费 | 1篇 |
专业分类
航空 | 74篇 |
航天技术 | 23篇 |
航天 | 24篇 |
出版年
2021年 | 1篇 |
2018年 | 1篇 |
2017年 | 5篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 1篇 |
2013年 | 7篇 |
2012年 | 3篇 |
2011年 | 5篇 |
2010年 | 1篇 |
2009年 | 7篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2005年 | 2篇 |
2004年 | 4篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1973年 | 3篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 6篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有121条查询结果,搜索用时 234 毫秒
111.
D.K. Chapman A.H. Brown 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(14):103-107
Dark-grown, 4-day old, seedlings were rotated for 20 hr on horizontal clinostats to minimize the amplitude of circumnutation. Then a Plexiglas sheet was placed gently against the tip of the cotyledons. By time-lapse video imaging (using intermittent IR illumination to which the plants were insensitive) movements of the clinostatted plants were observed before, during, and after the period of mechanical contact. Immediately after the Plexiglas sheet was removed residual nutation increased in amplitude almost three-fold, then declined over the next 7 hr to the prestimulation level. This demonstration of enhancement of circumnutation by mechanical contact is consistent with the model of an endogenous oscillator that can be stimulated by factors other than gravity. 相似文献
112.
Simulated microgravity does not alter epithelial cell adhesion to matrix and other molecules. 总被引:2,自引:0,他引:2
J M Jessup K Brown S Ishii R Ford T J Goodwin G Spaulding 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1994,14(8):71-76
Microgravity has advantages for the cultivation of tissues with high fidelity; however, tissue formation requires cellular recognition and adhesion. We tested the hypothesis that simulated microgravity does not affect cell adhesion. Human colorectal carcinoma cells were cultured in the NASA Rotating Wall Vessel (RWV) under low shear stress with randomization of the gravity vector that simulates microgravity. After 6-7 days, cells were assayed for binding to various substrates and compared to cells grown in standard tissue culture flasks and static suspension cultures. The RWV cultures bound as well to basement membrane proteins and to CEA, an intercellular adhesion molecule, as control cultures did. Thus, microgravity does not alter epithelial cell adhesion and may be useful for tissue engineering. 相似文献
113.
114.
David H. Rodgers Patricia M. Beauchamp Laurence A. Soderblom Robert H. Brown Gun-Shing Chen Meemong Lee Bill R. Sandel David A. Thomas Robert T. Benoit Roger V. Yelle 《Space Science Reviews》2007,129(4):309-326
MICAS is an integrated multi-channel instrument that includes an ultraviolet imaging spectrometer (80–185 nm), two high-resolution
visible imagers (10–20 μrad/pixel, 400–900 nm), and a short-wavelength infrared imaging spectrometer (1250–2600 nm). The wavelength ranges were chosen
to maximize the science data that could be collected using existing semiconductor technologies and avoiding the need for multi-octave
spectrometers. It was flown on DS1 to validate technologies derived from the development of PICS (Planetary Imaging Camera
Spectrometer). These technologies provided a novel systems approach enabling the miniaturization and integration of four instruments
into one entity, spanning a wavelength range from the UV to IR, and from ambient to cryogenic temperatures with optical performance
at a fraction of a wavelength. The specific technologies incorporated were: a built-in fly-by sequence; lightweight and ultra-stable,
monolithic silicon-carbide construction, which enabled room-temperature alignment for cryogenic (85–140 K) performance, and
provided superb optical performance and immunity to thermal distortion; diffraction-limited, shared optics operating from
80 to 2600 nm; advanced detector technologies for the UV, visible and short-wavelength IR; high-performance thermal radiators
coupled directly to the short-wave infrared (SWIR) detector optical bench, providing an instrument with a mass less than 10
kg, instrument power less than 10 W, and total instrument cost of less than ten million dollars. The design allows the wavelength
range to be extended by at least an octave at the short wavelength end and to ∼50 microns at the long wavelength end. Testing
of the completed instrument demonstrated excellent optical performance down to 77 K, which would enable a greatly reduced
background for longer wavelength detectors. During the Deep Space 1 Mission, MICAS successfully collected images and spectra
for asteroid 9969 Braille, Mars, and comet 19/P Borrelly. The Borrelly encounter was a scientific hallmark providing the first
clear, high resolution images and excellent, short-wavelength infrared spectra of the surface of an active comet’s nucleus. 相似文献
115.
Over 4200 delegates attended the fifth Euroscience Open Forum (ESOF), held in Dublin from 11 to 15 July 2012, with papers covering the gamut of scientific research, applications and policy contributed by Nobel laureates, including James Watson and Jules Hoffmann, internationally recognized but ‘local’ figures such as Mary Robinson, Jocelyn Bell Burnell and Bob Geldof, ‘celebrity’ scientists like Marcus du Sautoy and Craig Venter and a range of other major researchers. Space was also represented, with keynotes by the NASA administrator and ESA's Director of Science and Robotic Exploration. This report summarizes and discusses the space-related proceedings. 相似文献
117.
A method for selective pulse-train discrimination based on pulse repetition frequency (PRF) is presented. The technique permits acceptance of a pulse train with a desired PRF while rejecting all others, including those with pulse rates harmonically related to the desired one. 相似文献
118.
The proximity fuze 总被引:1,自引:0,他引:1
The ballistic accuracy and range of guns in 1914 was adequate for shooting at aircraft, but the method of aiming had not evolved beyond 1871 and was incapable of dealing with the small size, high speed, and agility of the airplane. It was realized that direct hits by projectiles could not be expected except by machine gun and automatic cannon, so the high explosive shells of heavier guns would have to be detonated through the time fuzes used for shrapnel. Pointing the gun and cutting the fuze required accurate location of the target and calculation of where it would be when the shell completed its flight. Of the inaccuracies in causing a shell to explode near an airplane, that of the fuze, especially the accurate determination of the flight time, was by far the worst. The development of a solution to this problem, a fuze that felt the influence of the plane in some manner, is reviewed 相似文献
119.
Observability, Eigenvalues, and Kalman Filtering 总被引:3,自引:0,他引:3
In higher order Kalman filtering applications the analyst often has very little insight into the nature of the observability of the system. For example, there are situations where the filter may be estimating certain linear combinations of state variables quite well, but this is not apparent from a glance at the error covariance matrix. It is shown here that the eigenvalues and eigenvectors of the error covariance matrix, when properly normalized, can provide useful information about the observability of the system. 相似文献
120.