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821.
O.N. Sherstyukov A.D. AkchurinE.Yu. Ryabchenko 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
A technique of modelling the one-hop radio wave propagation at middle latitudes in the presence of sporadic E-Layer is presented. The technique is focused on the performance of the long-term forecast of the maximum usable frequency range and on the increase of the radio communication reliability. Examples of calculation for medium-distance paths are shown. 相似文献
822.
T. Dudok de Wit O. Alexandrova I. Furno L. Sorriso-Valvo G. Zimbardo 《Space Science Reviews》2013,178(2-4):665-693
Advanced spectral and statistical data analysis techniques have greatly contributed to shaping our understanding of microphysical processes in plasmas. We review some of the main techniques that allow for characterising fluctuation phenomena in geospace and in laboratory plasma observations. Special emphasis is given to the commonalities between different disciplines, which have witnessed the development of similar tools, often with differing terminologies. The review is phrased in terms of few important concepts: self-similarity, deviation from self-similarity (i.e. intermittency and coherent structures), wave-turbulence, and anomalous transport. 相似文献
823.
In this paper, the expediency of increasing the relative sizes in clean models of wings and aircraft layouts in the low-speed open working section wind tunnels with a circular nozzle section is considered. Also determined is an additional correction, which makes it possible to take into account the external atmospheric pressure influence upon the aerodynamic characteristics of large-scale models and enhance the efficiency of the low-speed wind tunnels. 相似文献
824.
N. I. Mikheev V. M. Molochnikov I. A. Davletshin O. A. Dushina 《Russian Aeronautics (Iz VUZ)》2009,52(1):77-82
A method for simulating spatial-temporary characteristics of pulsating flows in the varying-in-length-area channels based on the solution of one-dimensional nonstationary equations of gas dynamics is presented. The calculation results are compared with the experimental data, and it is shown that the method being proposed rather adequately simulates real processes in complex unsteady flows. 相似文献
825.
Vesta and Ceres are the largest members of the asteroid belt, surviving from the earliest phases of Solar System history. They formed at a time when the asteroid belt was much more massive than it is today and were witness to its dramatic evolution, where planetary embryos were formed and lost, where the collisional environment shifted from accretional to destructive, and where the current size distribution of asteroids was sculpted by mutual collisions and most of the asteroids originally present were lost by dynamical processes. Since these early times, the environment of the asteroid belt has become relatively quiescent, though over the long history of the Solar System the surfaces of Vesta and Ceres continue to record and be influenced by impacts, most notably the south polar cratering event on Vesta. As a consequence of such impacts, Vesta has contributed a significant family of asteroids to the main belt, which is the likely source of the HED meteorites on Earth. No similar contribution to the main belt (or meteorites) is evident for Ceres. Through studies of craters, the surfaces of these asteroids will offer an opportunity for Dawn to probe the modern population of small asteroids in a size regime not directly observable from Earth. 相似文献
826.
O.K. Obrou M.N. MeneA.T. Kobea K.Z. Zaka 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Total electron content (TEC) derived from ionosonde data recorded at the station of Korhogo (Lat = 9.33°N, Long = 5.43°W, Dip = 0.67°S) are compared to the International Reference Ionosphere (IRI) model predicted TEC for high (1999) and low (1994) solar activity conditions. The results show that the model represents the diurnal variation of the TEC as well as a solar activity and seasonal dependence. This variation is closer to that of the ionosonde-inferred TEC at high solar activity. However, at low solar activity the IRI overestimates the ionosonde-inferred TEC. The relative deviation ΔTEC is more prominent in the equinoctial seasons during nighttime hours where it is as high as 70%. At daytime hours, the relative deviation is estimated to 0–30%. 相似文献
827.
R.U. Beisembaev V.I. Drobzhev E.A. Dryn O.N. Kryakunova N.F. Nikolaevskiy 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Ground level enhancements of cosmic ray intensity registered by means of neutron monitors at middle latitudes were studied by using Student’s criterion. Three of these events on 6 November 1997, 24 August 1998, and 13 December 2006 were analyzed in detail. It is shown that the use of Student’s criterion allows revealing effectively the ground level enhancements at middle latitudes. 相似文献
828.
L.A. McKinnell E.O. Oyeyemi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
A new neural network (NN) based global empirical model for the foF2 parameter, which represents the peak electron density has been developed using extended temporal and spatial geophysical relevant inputs. The first results from this new model were presented at the International Reference Ionosphere (IRI) 2006 workshop in Buenos Aires, Argentina, and showed that this new model would be a suitable replacement for the URSI and CCIR maps currently used within the IRI model for the purpose of F2 peak electron density predictions. Measured ground based ionosonde data, from 85 global stations, spanning the period 1995–2005 and, for a few stations from 1976 to 1986, obtained from various resources of the World Data Centre (WDC) archives (Space Physics Interactive Data Resource SPIDR, the Digital Ionogram Database, DIDBase, and IPS Radio and Space Services) have been used for training a NN. 相似文献
829.
Three-frequency resonances in the problem of fast rotation of an asymmetric body in elliptical orbit
The paper presents a classification of resonance problems generated by the highest-degree term of the perturbing function in the problem of fast rotation of an asymmetric solid body in elliptic orbit in a central gravitational field. Explicit formulas are obtained for Hamiltonians of all Hamiltonian systems that deter-mine motions in the neighborhood of resonances. Basic resonance effects are described. 相似文献
830.
O.?V.?SapunovaEmail author N.?L.?Borodkova V.?G.?Eselevich G.?N.?Zastenker Yu.?I.?Yermolaev 《Cosmic Research》2017,55(6):396-402
The paper is concerned with studying the thickness of fronts of 38 interplanetary shocks detected by the BMSW instrument, which is a part of the scientific payload of the SPEKTR-R spacecraft, which was launched into a highly elliptical orbit in 2011. The main parameters of the interplanetary shocks have been calculated as follows: the ratio of thermal pressure to magnetic pressure before the front β, the angle between the shock front normal and the undisturbed magnetic field θBn, the ratio of the shock propagation velocity to the magnetosonic velocity in the undisturbed region Mms, and the shock front velocity relative to the Earth. It has been shown that the front thickness determined from the plasma parameters approximately matches the front thickness obtained from the magnetic field measurements and lies between 0.5 and 5 proton inertial lengths. In some events, the oscillations have been observed (upstream and downstream of the shock) in plasma parameters and in the magnetic field data. The length has been found to be between 0.5 and 6 proton inertial lengths for the preceding oscillations and between 0.5 and 10 proton inertial lengths for the following oscillations. The average value of the proton inertial length is 62 km. 相似文献