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941.
R T Reynolds C P McKay J F Kasting 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1987,7(5):125-132
Tidal dissipation in the satellites of a giant planet may provide sufficient heating to maintain an environment favorable to life on the satellite surface or just below a thin ice layer. In our own solar system, Europa, one of the Galilean satellites of Jupiter, could have a liquid ocean which may occasionally receive sunlight through cracks in the overlying ice shell. In such case, sufficient solar energy could reach liquid water that organisms similar to those found under Antarctic ice could grow. In other solar systems, larger satellites with more significant heat flow could represent environments that are stable over an order of Aeons and in which life could perhaps evolve. We define a zone around a giant planet in which such satellites could exist as a tidally-heated habitable zone. This zone can be compared to the habitable zone which results from heating due to the radiation of a central star. In our solar system, this radiatively-heated habitable zone contains the Earth. 相似文献
942.
S. Satish S. Selva Raju T.S. Nanjunda Swamy P.L. Kulkarni 《Acta Astronautica》2009,65(9-10):1424-1428
In a little over four decades, the Indian Space Program has carved a niche for itself with the unique application driven program oriented towards National development. The end-to-end capability approach of the space projects in the country call for innovative practices and procedures in assuring the quality and reliability of space systems. The System Reliability (SR) efforts initiated at the start of the projects continue during the entire life cycle of the project encompassing design, development, realisation, assembly, testing and integration and during launch. Even after the launch, SR groups participate in the on-orbit evaluation of transponders in communication satellites and camera systems in remote sensing satellites. SR groups play a major role in identification, evaluation and inculcating quality practices in work centres involved in the fabrication of mechanical, electronics and propulsion systems required for Indian Space Research Organization's (ISRO's) launch vehicle and spacecraft projects. Also the reliability analysis activities like prediction, assessment and demonstration as well as de-rating analysis, Failure Mode Effects and Criticality Analysis (FMECA) and worst-case analysis are carried out by SR groups during various stages of project realisation. These activities provide the basis for project management to take appropriate techno-managerial decisions to ensure that the required reliability goals are met. Extensive test facilities catering to the needs of the space program has been set up. A system for consolidating the experience and expertise gained for issue of standards called product assurance specifications to be used in all ISRO centres has also been established. 相似文献
943.
Equilibrium adsorption isotherm data for the purine base adenine has been obtained on several prebiotically relevant minerals by frontal analysis using water as a mobile phase. Adenine is far displaced toward adsorption on pyrite (FeS2), quartz (SiO2), and pyrrhotite (FeS), but somewhat less for magnetite (Fe3O4) and forsterite (Mg2SiO4). The prebiotic prevalence of these minerals would have allowed them to act as a sink for adenine; removal from the aqueous phase would confer protection from hydrolysis as well, establishing a nonequilibrium thermodynamic framework for increased adenine synthesis. Our results provide evidence that adsorption phenomena may have been critical for the primordial genetic architecture. 相似文献
944.
M. Bamsey T. Graham M. Stasiak A. Berinstain A. Scott T. Rondeau Vuk M. Dixon 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Canada began research on space-relevant biological life support systems in the early 1990s. Since that time Canadian capabilities have grown tremendously, placing Canada among the emerging leaders in biological life support systems. The rapid growth of Canadian expertise has been the result of several factors including a large and technically sophisticated greenhouse sector which successfully operates under challenging climatic conditions, well planned technology transfer strategies between the academic and industrial sectors, and a strong emphasis on international research collaborations. Recent activities such as Canada’s contribution of the Higher Plant Compartment of the European Space Agency’s MELiSSA Pilot Plant and the remote operation of the Arthur Clarke Mars Greenhouse in the Canadian High Arctic continue to demonstrate Canadian capabilities with direct applicability to advanced life support systems. There is also a significant latent potential within Canadian institutions and organizations with respect to directly applicable advanced life support technologies. These directly applicable research interests include such areas as horticultural management strategies (for candidate crops), growth media, food processing, water management, atmosphere management, energy management, waste management, imaging, environment sensors, thermal control, lighting systems, robotics, command and data handling, communications systems, structures, in-situ resource utilization, space analogues and mission operations. With this background and in collaboration with the Canadian aerospace industry sector, a roadmap for future life support contributions is presented here. This roadmap targets an objective of at least 50% food closure by 2050 (providing greater closure in oxygen, water recycling and carbon dioxide uptake). The Canadian advanced life support community has chosen to focus on lunar surface infrastructure and not low Earth orbit or transit systems (i.e. microgravity applications). To advance the technical readiness for the proposed lunar missions, including a lunar plant growth lander, lunar “salad machine” (i.e. small scale plant production unit) and a full scale lunar plant production system, a suite of terrestrial developments and analogue systems are proposed. As has been successfully demonstrated by past Canadian advanced life support activities, terrestrial technology transfer and the development of highly qualified personnel will serve as key outputs for Canadian advanced life support system research programs. This approach is designed to serve the Canadian greenhouse industry by developing compliance measures for mitigating environmental impact, reducing labour and energy costs as well as improving Canadian food security, safety and benefit northern/remote communities. 相似文献
945.
Trajectories of spacecraft with electro-jet low-thrust engines are studied for missions planning to deliver samples of matter from small bodies of the Solar System: asteroids Vesta and Fortuna, and Martian moon Phobos. Flight trajectories are analyzed for the mission to Phobos, the limits of optimization of payload spacecraft mass delivered to it are determined, and an estimate is given to losses in the payload mass when a low-thrust engine with constant outflow velocity is used. The model of an engine with ideally regulated low thrust is demonstrated to be convenient for calculations and analysis of flight trajectories of a low-thrust spacecraft. 相似文献
946.
We present the observational results on chromospheric spicules obtained at the Sayan observatory 50 cm coronograph. To investigate the evolution of chromospheric spicules, we analysed spicule spectra of strong chromospheric lines measured simultaneously at three altitudes above the solar limb during 5–60 min with a time resolution of 10 to 20 s. The spatial resolution was better than 1, and the spectral resolution was 0.03Å in 6563Å. The appearance of a spicule at a given altitude is preceded by an sharp increase in line-of-sight velocity and/or in line half-width at a lower level. Generally, the evolution has a non-monotonous impulsive character. Changes of line-of-sight velocities and other parameters of the line profile can be represented as the superposition of slow, evolutionary changes and fluctuations with periods of about 80 to 120 s. The amplitude of line-of-sight velocity fluctuations is 2–3 km/sec and tends to increase with height. By studying the phase delays of the fluctuations at different heights, we found that the propagation velocity exceeds 300 km s–1, and that the disturbances do not necessarily propagate upwards. 相似文献
947.
Part I of this work deals with the use of electrodynamic forces for control of tethered satellite system. A system formed by two massive end-bodies connected to each other by a current carrying tether is to be kept in an Earth-pointing orientation by means of joint actions of thrusters on one of the end-bodies and electrodynamic forces acting on the tether 相似文献
948.
D. J. McComas E. R. Christian N. A. Schwadron N. Fox J. Westlake F. Allegrini D. N. Baker D. Biesecker M. Bzowski G. Clark C. M. S. Cohen I. Cohen M. A. Dayeh R. Decker G. A. de Nolfo M. I. Desai R. W. Ebert H. A. Elliott H. Fahr P. C. Frisch H. O. Funsten S. A. Fuselier A. Galli A. B. Galvin J. Giacalone M. Gkioulidou F. Guo M. Horanyi P. Isenberg P. Janzen L. M. Kistler K. Korreck M. A. Kubiak H. Kucharek B. A. Larsen R. A. Leske N. Lugaz J. Luhmann W. Matthaeus D. Mitchell E. Moebius K. Ogasawara D. B. Reisenfeld J. D. Richardson C. T. Russell J. M. Sokół H. E. Spence R. Skoug Z. Sternovsky P. Swaczyna J. R. Szalay M. Tokumaru M. E. Wiedenbeck P. Wurz G. P. Zank E. J. Zirnstein 《Space Science Reviews》2018,214(8):116
The Interstellar Mapping and Acceleration Probe (IMAP) is a revolutionary mission that simultaneously investigates two of the most important overarching issues in Heliophysics today: the acceleration of energetic particles and interaction of the solar wind with the local interstellar medium. While seemingly disparate, these are intimately coupled because particles accelerated in the inner heliosphere play critical roles in the outer heliospheric interaction. Selected by NASA in 2018, IMAP is planned to launch in 2024. The IMAP spacecraft is a simple sun-pointed spinner in orbit about the Sun-Earth L1 point. IMAP’s ten instruments provide a complete and synergistic set of observations to simultaneously dissect the particle injection and acceleration processes at 1 AU while remotely probing the global heliospheric interaction and its response to particle populations generated by these processes. In situ at 1 AU, IMAP provides detailed observations of solar wind electrons and ions; suprathermal, pickup, and energetic ions; and the interplanetary magnetic field. For the outer heliosphere interaction, IMAP provides advanced global observations of the remote plasma and energetic ions over a broad energy range via energetic neutral atom imaging, and precise observations of interstellar neutral atoms penetrating the heliosphere. Complementary observations of interstellar dust and the ultraviolet glow of interstellar neutrals further deepen the physical understanding from IMAP. IMAP also continuously broadcasts vital real-time space weather observations. Finally, IMAP engages the broader Heliophysics community through a variety of innovative opportunities. This paper summarizes the IMAP mission at the start of Phase A development. 相似文献
949.
A prominent neuroscientist A. Damasio has observed that “More may have been learned about the brain and the mind in the 1990s... than during the entire previous history of psychology and neuroscience” (1999). This progress, which should continue at an exponentially increasing pace as we move into the 21st century, sets the stage for another revolution-in the scientific formulation of intentional behavior. Just as applied sciences such as fluid mechanics and solid-state electronics benefited from breakthroughs in physics, so it may be expected that social psychology and economics, for example, will similarly benefit from our expanding knowledge of psychosomatic and psychological function. Economics, however, with its basic concepts dating from the nineteenth century, must endure an extensive renewal. Toward this end, a new mathematical theory of behavior was formulated in the early 1990s based on the contributions of prominent psychologists and economists over the past two centuries. Presentation of the new approach at international conferences continued in 2000 with attention moving beyond the fundamentals into macroeconomic concerns including business cycles, productivity, and unemployment 相似文献
950.
Mende S.B. Frey H.U. Immel T.J. Gerard J.-C. Hubert B. Fuselier S.A. 《Space Science Reviews》2003,109(1-4):211-254
The IMAGE spacecraft carries three FUV photon imagers, the Wideband Imaging Camera (WIC) and two channels, SI-12 and SI-13, of the Spectrographic Imager. These provide simultaneous global images, which can be interpreted in terms of the precipitating particle types (protons and electrons) and their energies. IMAGE FUV is the first space-borne global imager that can provide instantaneous global images of the proton precipitation. At times a bright auroral spot, rich in proton precipitation, is observed on the dayside, several degrees poleward of the auroral zone. The spot was identified as the footprint of the merging region of the cusp that is located on lobe field lines when IMF Bz was northward. This identification was based on compelling statistical evidence showing that the appearance and location of the spot is consistent with the IMF Bz and By directions. The intensity of the spot is well correlated with the solar wind dynamic pressure and it was found that the direct entry of solar wind particles could account for the intensity of the observed spot without the need for any additional acceleration. Another discovery was the observation of dayside sub-auroral proton arcs. These arcs were observed in the midday to afternoon MLT sector. Conjugate satellite observations showed that these arcs were generated by pure proton precipitation. Nightside auroras and their relationship to substorm phases were studied through single case studies and in a superimposed epoch analysis. It was found that generally there is substantial proton precipitation prior to substorms and the proton intensity only doubles at substorm onset while the electron auroral brightness increases on average by a factor of 5 and sometimes by as much as a factor of 10. Substorm onset occurs in the central region of the pre-existing proton precipitation. Assuming that nightside protons are precipitating from a quasi-stable ring current at its outer regions where the field lines are distorted by neutral sheet currents we can associate the onset location with this region of closed but distorted field lines relatively close to the earth. Our results also show that protons are present in the initial poleward substorm expansion however later they are over taken by the electrons. We also find that the intensity of the substorms as quantified by the intensity of the post onset electron precipitation is correlated with the intensity of the proton precipitation prior to the substorms, highlighting the role of the pre-existing near earth plasma in the production of the next substorm. 相似文献