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231.
232.
It is important for any new launch system to develop a successful pricing strategy and to optimize launch system parameters to receive a high economic profit. A question arises, what will happen when an existing suborbital flight market (the first likely to be established in space) is interfered with by a new established orbital flight market for space tourism. There is a risk that the suborbital space tourism market could be almost instantly displaced when a product capable of reaching orbit was introduced. This is best discussed using the following three cases whose results are presented in this paper. Case A presents a ticket pricing strategy for a suborbital and orbital vehicle if the two vehicles do not compete in the same market. Case B shows the necessary ticket pricing strategy for a suborbital vehicle if there is competition from an orbital flight operator. However, the suborbital vehicle would not be able to keep up with a drop in ticket prices due to its obsolete characteristics. Thus, the suborbital vehicle would be forced to stop operation in the year when flight costs became higher than flight receipts as shown in case C. 相似文献
233.
北约(NATO)最近出台了一份名为《无人机系统飞行计划》的战略指导文件,要求 NATO 及各成员国共同制定一个无人机采办和使用的协同计划,包括 NATO 采办自己的无人机系统计划、各成员国采办高空长航时(HALE)无人机系统计划, 相似文献
234.
235.
K.L. Bryson Z. Peeters F. Salama B. Foing P. Ehrenfreund A.J. Ricco E. Jessberger A. Bischoff M. Breitfellner W. Schmidt F. Robert 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
In March of 2009, the ORGANIC experiment integrated into the European multi-user facility EXPOSE-R, containing experiments dedicated to Astrobiology, was mounted through Extra Vehicular Activity (EVA) externally on the International Space Station (ISS). The experiment exposed organic samples of astronomical interest for a duration of 97 weeks (∼22 months) to the space environment. The samples that were returned to Earth in spring 2011, received a total UV radiation dose during their exposure including direct solar irradiation of >2500 h, exceeding the limits of laboratory simulations. We report flight sample preparation and pre-flight ultraviolet–visible (UV–Vis) characterization of the ORGANIC samples, which include 11 polycyclic aromatic hydrocarbons (PAHs) and three fullerenes. The corresponding time-dependent ground control monitoring experiments for ORGANIC measured over ∼19 months are presented and the results anticipated upon return of the samples are discussed. We present the first UV–Vis spectrum of solid circobiphenyl (C38H16). Further, we present the first published UV–Vis spectra of diphenanthro[9,10-b′,10′-d]thiophene (C28H16S), dinaphtho[8,1,2-abc,2′,1′,8′-klm]coronene (C36H16), tetrabenzo[de,no,st,c′d′]heptacene (C42H22), and dibenzo[jk,a′b′]octacene (C40H22) in solid phase and in solution. The results of the ORGANIC experiment are expected to enhance our knowledge of the evolution and degradation of large carbon-containing molecules in space environments. 相似文献
236.
John H. Heinbockel Tony C. Slaba Steve R. Blattnig Ram K. Tripathi Lawrence W. Townsend Thomas Handler Tony A. Gabriel Lawrence S. Pinsky Brandon Reddell Martha S. Clowdsley Robert C. Singleterry John W. Norbury Francis F. Badavi Sukesh K. Aghara 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The protection of astronauts and instrumentation from galactic cosmic rays and solar particle events is one of the primary constraints associated with mission planning in low earth orbit or deep space. To help satisfy this constraint, several computational tools have been developed to analyze the effectiveness of various shielding materials and structures exposed to space radiation. These tools are now being carefully scrutinized through a systematic effort of verification, validation, and uncertainty quantification. In this benchmark study, the deterministic transport code HZETRN is compared to the Monte Carlo transport codes HETC-HEDS and FLUKA for a 30 g/cm2 water target protected by a 20 g/cm2 aluminum shield exposed to a parameterization of the February 1956 solar particle event. Neutron and proton fluences as well as dose and dose equivalent are compared at various depths in the water target. The regions of agreement and disagreement between the three codes are quantified and discussed, and recommendations for future work are given. 相似文献
237.
Previous literature has analyzed PCM/FM telemetry systems using idealized FM demodulators at the receiver. However, in many systems operating today, phase-lock loop demodulators are employed which depart noticeably from ideal operation as the loop falls ?out of lock.? In this paper an approximate expression for error probability is derived, which clearly indicates the effect of the loop on the previously published data using ideal discriminators. It is shown that the presence of the loop becomes apparent at input signal-to-noise ratios below approximately 3.5 dB, while the amount of error increase over the ideal case depends, to a large extent, upon the shape of IF filtering being used. 相似文献
238.
Erika M. Harnett Robert M. Winglee 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
The Moon spends 20% of its orbit within the terrestrial magnetosphere. During this time it experiences a dynamic plasma environment, including high-speed streams, flux ropes and a flux of heavy ions from ionospheric outflows. 3D multi-fluid simulations of the Moon within the magnetosphere during a substorm shows that a highly variable plasma flow can develop in the vicinity of the Moon due to the passage of a flux rope. The transit of a flux rope past the Moon potentially leads to a plasma wake that is mis-aligned from the optical wake by nearly 30°. This will have implications when determining the range of space weathering and surface charging the lunar surface experiences. 相似文献
239.
Robert J. Coates 《Space Science Reviews》1969,9(3):361-418
The tracking and data acquisition systems provide the key link between the remote spacecraft and the scientific experimenter on the ground. The operation of the space experiment takes place through the links of command, telemetry and tracking. The evolution from the early very simple spacecraft missions toward more complex and sophisticated missions has been paralleled by a similar evolution in the tracking and data acquisition systems. The early Minitrack interferometer tracking system still carries the major tracking workload for space missions; however greater tracking accuracy requirements for more recent missions, such as the Orbiting Geophysical Observatory and the Apollo mission, have brought about the development of unified tracking and data acquisition systems which utilize hybrid pseudo-random code/sidetone ranging techniques. The data acquisition has evolved from analog telemetry systems to the present day heavy use of PCM digital telemetry. Likewise the command systems have evolved from early simple on/off command systems into PCM digital command data systems. The trend is toward greater real time control of more complex functions on board the spacecraft. Newer spacecraft are incorporating computer-type systems in the spacecraft which require programming and memory load through the ground command link. The most attractive concept for the next generation network for tracking and data acquisition is a network consisting of synchronous-orbit Tracking and Data Relay Satellites for covering launches and low-orbit earth satellites plus a few selected ground stations for supporting spacecraft in high earth orbit and lunar orbit. 相似文献
240.
Stelios Charalambides Garry E. Hunt Michael J. Rycroft Robert J. Murgatroyd David W.S. Limbert 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1985,5(6):127-132
We present the results of a study of anomalies, which are defined as differences of seasonal means from the data set seasonal means, in the Earth's radiation budget from the analysis of nine years of ten day mean observations derived from the NOAA polar orbiter satellites for the period, 1974–1983. We estimate that the standard deviation in the outgoing longwave flux for this period is less than 12 Wm?2 and typically 7 Wm?2. The results show that there are several geographical areas for which the standard deviation is in excess of 20 Wm?2; in such regions the radiation budget anomalies exceeded these due to natural atmospheric variability. In this paper we discuss the relationship of these anomalies with climatic change. 相似文献