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61.
The evolving use of large space systems, with accompanying large truss-like structures, creates the need to develop an on-orbit fabrication and assembly capability for producing structural elements and structural subsystems. Such a capability is a basic necessity for extremely large structural subsystems because of the economy of operations resulting from the on-orbit conversion of high-density material stock into low-density structural elements. This paper discusses the development of large space structural subsystems; in particular the role a generic structure plays in that development. This generic structure embodies the key issues of the structural subsystems of various classes of large space systems and as such, when its development is completed a proof-of-capability will have been accomplished for a wide variety of large space structures. 相似文献
62.
A definitive analysis technique is proposed for designing wind generating plants to produce electrical energy at minimum cost. The method employs variation in essential design parameters: rated power level, rated wind velocity, design wind velocity, and number of generator poles. These parameters in turn define wind turbine radius, turbine speed, rated torque at step-up gear input, and step-up gear ratio. When these are combined with site (or region) specific wind statistics, appropriate wind plant cost functions, and criteria by which to compute annual cost of ownership, the result yields the cost of produced energy for the several design variations. The selected design is that one for which the cost of produced energy is minimum. 相似文献
63.
The oxidants produced by radiolysis and photolysis in the icy surface of Europa may be necessary to sustain carbon-based biochemistry in Europa's putative subsurface ocean. Because the subduction of oxidants to the ocean presents considerable thermodynamic challenges, we examine the formation of oxygen and related species in Europa's surface ice with the goal of characterizing the chemical state of the irradiated material. Relevant spectral observations of Europa and the laboratory data on the production of oxygen and related species are first summarized. Since the laboratory data are incomplete, we examine the rate equations for formation of oxygen and its chemical precursors by radiolysis and photolysis. Measurements and simple rate equations are suggested that can be used to characterize the production of oxidants in Europa's surface material and the chemical environment produced by radiolysis. Possible precursor molecules and the role of radical trapping are examined. The possibility of oxygen reactions on grain surfaces in Europa's regolith is discussed, and the earlier estimates of the supply of O(2) to the atmosphere are increased. 相似文献
64.
This paper contains a mathematical analysis of the problem of automatically pointing a sighting device, mounted on a moving vehicle, at a fixed target. The results apply to situations such as automatic sighting devices for aircraft and helicopters, automatic camera aiming for airborne photography, etc. Basic mathematical relations, which govern all forms of such automatic pointing devices, are derived. 相似文献
65.
Daly M. G. Barnouin O. S. Dickinson C. Seabrook J. Johnson C. L. Cunningham G. Haltigin T. Gaudreau D. Brunet C. Aslam I. Taylor A. Bierhaus E. B. Boynton W. Nolan M. Lauretta D. S. 《Space Science Reviews》2017,212(1-2):899-924
Space Science Reviews - The Canadian Space Agency (CSA) has contributed to the Origins Spectral Interpretation Resource Identification Security-Regolith Explorer (OSIRIS-REx) spacecraft the... 相似文献
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C. S. Arridge N. Andr�� H. J. McAndrews E. J. Bunce M. H. Burger K. C. Hansen H.-W. Hsu R. E. Johnson G. H. Jones S. Kempf K. K. Khurana N. Krupp W. S. Kurth J. S. Leisner C. Paranicas E. Roussos C. T. Russell P. Schippers E. C. Sittler H. T. Smith M. F. Thomsen M. K. Dougherty 《Space Science Reviews》2011,164(1-4):1-83
Saturn??s rich magnetospheric environment is unique in the solar system, with a large number of active magnetospheric processes and phenomena. Observations of this environment from the Cassini spacecraft has enabled the study of a magnetospheric system which strongly interacts with other components of the saturnian system: the planet, its rings, numerous satellites (icy moons and Titan) and various dust, neutral and plasma populations. Understanding these regions, their dynamics and equilibria, and how they interact with the rest of the system via the exchange of mass, momentum and energy is important in understanding the system as a whole. Such an understanding represents a challenge to theorists, modellers and observers. Studies of Saturn??s magnetosphere based on Cassini data have revealed a system which is highly variable which has made understanding the physics of Saturn??s magnetosphere all the more difficult. Cassini??s combination of a comprehensive suite of magnetospheric fields and particles instruments with excellent orbital coverage of the saturnian system offers a unique opportunity for an in-depth study of the saturnian plasma and fields environment. In this paper knowledge of Saturn??s equatorial magnetosphere will be presented and synthesised into a global picture. Data from the Cassini magnetometer, low-energy plasma spectrometers, energetic particle detectors, radio and plasma wave instrumentation, cosmic dust detectors, and the results of theory and modelling are combined to provide a multi-instrumental identification and characterisation of equatorial magnetospheric regions at Saturn. This work emphasises the physical processes at work in each region and at their boundaries. The result of this study is a map of Saturn??s near equatorial magnetosphere, which represents a synthesis of our current understanding at the end of the Cassini Prime Mission of the global configuration of the equatorial magnetosphere. 相似文献
69.
J L Garland K L Cook M Johnson R Sumner N Fields 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1997,20(10):1931-1937
A study evaluating alternative methods for long term operation of biomass production systems was recently completed at the Kennedy Space Center (KSC). The 418-day study evaluated repeated batch versus mixed-aged production of potato grown on either standard 1/2-strength Hoagland's nutrient solution or solutions including nutrients recycled from inedible plant material. The long term effects of closure and recycling on microbial dynamics were evaluated by monitoring the microbial communities associated with various habitats within the plant growth system (i.e., plant roots, nutrient solution, biofilms within the hydroponic systems, atmosphere, and atmospheric condensate). Plate count methods were used to enumerate and characterize microorganisms. Microscopic staining methods were used to estunate total cell densities. The primary finding was that the density and composition of microbial communities associated with controlled environmental plant growth systems are stable during long term operation. Continuous production resulted in slightly greater stability. Nutrient recycling, despite the addition of soluble organic material from the waste processing system, did not significantly increase microbial density in any of the habitats. 相似文献
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