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121.
N. Klöcker H. Lühr P. Robert A. Korth 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1985,5(4):237-241
Ground observations of locally confined, very intense, drifting current systems by the EISCAT magnetometer cross in correlation with GEOS 2 measurements will be explained in terms of kinetic Alfvén waves. In the ground based magnetograms the events are characterized by strong pulsations with amplitudes in the horizontal component up to 1000 nT and periods of about 300s and longer. They occur in the evening hours adjacent to the poleward side of the Harang discontinuity with the onset of a substorm. At the same time the inner edge of the plasma sheet passes the GEOS 2 position, magnetically conjugate to ground stations. The common features of four events during Nov and Dec 1982 will be discussed. 相似文献
122.
Dorr RF 《Aerospace America》2004,42(2):6-8
The Washington Watch column reports on President Bush's recently announced human space flight program, which includes new policies for returning the shuttle to flight, finishing the International Space Station by 2010, and developing a new space vehicle to return to the Moon; challenges in the airline industry; and selection of a helicopter for use by the President. 相似文献
123.
If impending failures in aerospace systems can be predicted deterministically during a test or checkout period, action can be taken to replace or repair the defective parts and a mission failure averted. This has the effect of increasing the mission reliability of the system. There are several methods of predicting specific failures especially adapted to electronic systems, but also applicable to electromechanical and fluid systems and components. These are classified and discussed in detail, with examples. References are cited for additional detail. By way of background, deterministic failure prediction is contrasted with statistical failure prediction. The nature and definition of failure and related concepts are also discussed, together with the physical principles upon which the several failure prediction methods are based. Used selectively and collectively, these failure prediction methods can form an optimal failure prevention strategy for use in a system test or checkout program. 相似文献
124.
Crane Robert B. Sharpe C. B. 《IEEE transactions on aerospace and electronic systems》1966,(6):659-664
The purpose of this paper is to investigate the signal distortion which results when long, series-fed arrays are used for communication. It is shown that under certain conditions the antenna array can be considered a linear filter, the response of which is a function of frequency as well as spatial coordinates. The distortion accompanying the transmission as measured by the least mean-square difference between the transmitted and the received signals is derived. This expression is evaluated for the case of a uniformly excited array and a rectangular band-pass signal spectrum. In the absence of noise the transmitted signal can be completely recovered in the receiver by employing the proper linear filter. In the presence of noise the signal cannot, of course, be completely recovered. However, a technique for minimizing the distortion, in this case using a pre-filter and a post-filter, is investigated. 相似文献
125.
本文介绍一种供数字波束形成X波段敏感蒙皮相控阵天线用的7.9~9.7GHz单片雷达接收机前端。这种敏捷单片接收机前端能够使自适应跳频雷达系统微波接收机模块的体积和成本显著减小。测量结果表明基本满足性能要求。 相似文献
126.
介绍了一种采用0.25um SiGe BiCMOS工艺集成的低压低功率X波段低噪声放大器(LNA),比较了此种放大器与IEEE 802.11a LNA的设计。X波段LNA和IEEE 802.11a LNA的工作频率分别为10GHz和5.8GHz。所设计的LNA都采用了相同的结构和电压,并耗费同量的电流。两种LNA都只需要1.5V的电压,消耗1.5mW的直流功率。两种电路的差异是它们有不同的输入与输出匹配和负载。本文介绍的LNA在10GHz时的电压增益为11.49dB,噪声系数(NF)为3.84dB,输入反射损失为-15.37dB,输出反射损失为-17dB,P1dB为-3.75dBm。在5.8GHz时的电压增益为16.07dB,噪声系数为3.07dB,输入反射损失为-18.1dB,输出反射损失为-15.23dB,P1dB为-6.54dBm。两电路的关键特征是:低压、低功率和良好的噪声匹配。频率为IOGHz和5.8GHz时,噪声系数与最小噪声系数之差分别只有0.03dB和0.05dB。验证了一种高频(X波段)低成本设计,与其他技术(如GaAs、SiBJT、JFET、PHMET和MESFET等)相比,它是在SiGe BiCMOS中设计的。 相似文献
127.
Robert A. Jones 《Space Policy》2004,20(1):45-48
It has always been clear that one of the main driving forces behind the space race was Cold War propaganda. But just what impact did it have on ‘the minds of men everywhere’? This paper presents a survey of the impact of space exploration on popular culture in Britain in the 1950s and 1960s, concentrating chiefly on the cinema. Before the launch of Sputnik in 1957, although space was present in popular culture, it was generally aimed at a specialised audience. In the 1960s, interest in space became widespread and reached unexpected corners of popular culture such as pop music. This popular success had dangerous consequences, however: when public interest waned in the early 1970s, the immense cost of the Moon landings could no longer be justified on propaganda grounds and the project was massively reduced. 相似文献
128.
Ilyin Viacheslav Moukhamedieva Lana Osipov Georgy Batov Aleksey Soloviova Zoya Mardanov Robert Panina Yana Gegenava Anna 《Acta Astronautica》2011,68(9-10):1529-1536
Current control of human microflora is a great problem not only for the space medicine but also for practical health care. Due to many reasons its realization by classical bacteriological method is difficult in practical application or cannot be done.To evaluate non-cultural methods of microbial control of crews in a confined habitat we evaluated two different methods.The first method is based on digital treatment of microbial visual images, appearing after gram staining of microbial material from natural sample. This way the rate between gram-positive and gram-negative microbe could be gained as well as differentiation of rods and cocci could be attained, which is necessary for primary evaluation of human microbial cenosis in remote confined habitats.The other non-culture method of human microflora evaluation is gas chromatomass spectrometry (gcms) analysis of swabs gathered from different body sites. Gc-ms testing of swabs allows one to validate quantitative and special microflora based on specific lipid markers analysis. 相似文献
130.
InSight Mars Lander Robotics Instrument Deployment System 总被引:1,自引:0,他引:1
A. Trebi-Ollennu Won Kim Khaled Ali Omair Khan Cristina Sorice Philip Bailey Jeffrey Umland Robert Bonitz Constance Ciarleglio Jennifer Knight Nicolas Haddad Kerry Klein Scott Nowak Daniel Klein Nicholas Onufer Kenneth Glazebrook Brad Kobeissi Enrique Baez Felix Sarkissian Menooa Badalian Hallie Abarca Robert G. Deen Jeng Yen Steven Myint Justin Maki Ali Pourangi Jonathan Grinblat Brian Bone Noah Warner Jaime Singer Joan Ervin Justin Lin 《Space Science Reviews》2018,214(5):93
The InSight Mars Lander is equipped with an Instrument Deployment System (IDS) and science payload with accompanying auxiliary peripherals mounted on the Lander. The InSight science payload includes a seismometer (SEIS) and Wind and Thermal Shield (WTS), heat flow probe (Heat Flow and Physical Properties Package, HP3) and a precision tracking system (RISE) to measure the size and state of the core, mantle and crust of Mars. The InSight flight system is a close copy of the Mars Phoenix Lander and comprises a Lander, cruise stage, heatshield and backshell. The IDS comprises an Instrument Deployment Arm (IDA), scoop, five finger “claw” grapple, motor controller, arm-mounted Instrument Deployment Camera (IDC), lander-mounted Instrument Context Camera (ICC), and control software. IDS is responsible for the first precision robotic instrument placement and release of SEIS and HP3 on a planetary surface that will enable scientists to perform the first comprehensive surface-based geophysical investigation of Mars’ interior structure. This paper describes the design and operations of the Instrument Deployment Systems (IDS), a critical subsystem of the InSight Mars Lander necessary to achieve the primary scientific goals of the mission including robotic arm geology and physical properties (soil mechanics) investigations at the Landing site. In addition, we present test results of flight IDS Verification and Validation activities including thermal characterization and InSight 2017 Assembly, Test, and Launch Operations (ATLO), Deployment Scenario Test at Lockheed Martin, Denver, where all the flight payloads were successfully deployed with a balloon gravity offload fixture to compensate for Mars to Earth gravity. 相似文献