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241.
A.P. Kireev A.M. Krymskii 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
The pattern of the magnetic field/plasma convection can be, to some extent, recovered from the magnetic field measurements by employing either theoretical or numerical models. We use the MAG/ER day-time measurements of the magnetic field at the altitudes from 90 to 180 km during the elliptical orbits of MGS. Analysis of the altitude variation of the characteristics of the large-scale magnetic fields, which were measured some distance away from strong crustal magnetic anomalies, is summarized. The low density of the Martian atmosphere together with the crustal magnetization result in critical differences in plasma convection which are followed by remarkable differences of the magnetic field features within the ionosphere of Venus and Mars (even in its northern hemisphere where the crustal magnetization is, on the average, low) and distribution of currents. 相似文献
242.
E.L. Afraimovich E.I. Astafyeva E.A. Kosogorov Yu.V. Yasyukevich 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
For the first time we propose a method for detecting the mid-latitude field-aligned disturbances (FADs) prolated on the magnetic field. The method is based on GPS detection of isolated ionosphere disturbances and analysis of the angle between the “GPS satellite-receiver” line-of-sight and the local magnetic field vector, for which maximum (minimum) of aperiodic variation of the total electron content (TEC) is registered. 相似文献
243.
Minakshi Devi A.K. Barbara Ko-Ichiro Oyama Chia-Hung Chen 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
The modifications induced in the dynamics of the ionosphere by the major Japan earthquake (EQ) of March 11, 2011 (epicenter at 38.322°N, 142.369°E, M = 8.9) in presence of a magnetic storm are examined by mapping latitudinal variations of F-layer ionization density (NmF2) from 22 stations covering the epicenter zone. The changes forced into the Total Electron Content (TEC) by the major EQ in the magnetic storm ambiance are also examined from the GPS data collected at Guwahati (26° 10′ N, 91° 45’ E), situated in the major fault system of East Asia. The contributions of pre-seismic electric field as well as of magnetic storm time electric field in the observed density variations are brought into the ambit of discussion. The influence of lower atmosphere in shaping TEC features during the study case is highlighted. The effects of solar activity on density variations during such complex ambiances are also addressed. 相似文献
244.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014,53(2):219-225
The Ionospheric F2-layer peak parameters response to a magnetic storm had been investigated over Ilorin, Nigeria (Lat. 8:53°N, Long. 4.5°E, dip angle, −2.96°), Jicamarca, Peru (11.95°S, 76.87°W, dip angle, 0.8°) and Hermanus, South Africa (34.42°S, 19.22°E, dip angle, −60.77°), using percentage enhancement/depletion values. Our results showed an enhancement in NmF2 at all of these stations. Averagely, pre-noon and post-noon peaks are highest at Ilorin during quiet time. The similar pattern observed for quiet condition between Ilorin and Jicamarca was due to their latitudinal positions. For disturbed NmF2 condition, Jicamarca and Ilorin recorded higher peaks at nighttime than during the daytime for the storms main phase, and the reverse over Hermanus. The nighttime and daytime increases were observed respectively at Ilorin and Hermanus during the recovery period. The hmF2 variation recorded higher enhancement at Jicamarca during the daytime and at Hermanus at nighttime during the main phase. During the recovery phase, the highest enhancement was recorded during the daytime at Jicamarca, and over Hermanus at nighttime. These observations find their explanation in the magnetospheric current, solar wind and E × B drift. 相似文献
245.
D. Buresova J. Lastovicka P. Hejda J. Bochnicek 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
The paper is focused on ionospheric response to occasional magnetic disturbances above selected ionospheric stations located at middle latitudes of the Northern and Southern Hemisphere under extremely low solar activity conditions of 2007–2009. We analyzed changes in the F2 layer critical frequency foF2 and the F2 layer peak height hmF2 against 27-days running mean obtained for different longitudinal sectors of both hemispheres for the initial, main and recovery phases of selected magnetic disturbances. Our analysis showed that the effects on the middle latitude ionosphere of weak-to-moderate CIR-related magnetic storms, which mostly occur around solar minimum period, could be comparable with the effects of strong magnetic storms. In general, both positive and negative deviations of foF2 and hmF2 have been observed independent on season and location. However positive effects on foF2 prevailed and were more significant. Observations of stormy ionosphere also showed large departures from the climatology within storm recovery phase, which are comparable with those usually observed during the storm main phase. The IRI STORM model gave no reliable corrections of foF2 for analyzed events. 相似文献
246.
D.I. Pontin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The magnetic field in many astrophysical plasmas – such as the solar corona and Earth’s magnetosphere – has been shown to have a highly complex, three-dimensional structure. Recent advances in theory and computational simulations have shown that reconnection in these fields also has a three-dimensional nature, in contrast to the widely used two-dimensional (or 2.5-dimensional) models. Here we discuss the underlying theory of three-dimensional magnetic reconnection. We also review a selection of new models that illustrate the current state of the art, as well as highlighting the complexity of energy release processes mediated by reconnection in complicated three-dimensional magnetic fields. 相似文献
247.
通过调节压气机转速和试验器的进、排气节气门的开度,可以获得所需的压气机气动试验特性。压气机试验器调节系统采用双冗余液压系统、成熟的可编程控制器和适合压气机性能试验特点的控制软件,很好地解决了试验状态控制精度低和试验风险高的问题。该系统的成功应用使试验器的工作效率显著提高,并减少了设备损耗和大量的能源消耗。 相似文献
248.
自励模式霍尔推力器设计 总被引:1,自引:1,他引:0
为实现P70霍尔推力器自励模式稳定放电运行,分别设计了满足自励模式放电要求的磁路和电路。其磁路设计是基于霍尔推力器他励运行模式最优放电性能参数和磁势不变原理,采用FEMM有限元磁场计算软件建模,将推力器内铁心半径由7 mm减至4 mm,可得到满足自励模式运行要求的优化磁场。针对电磁线圈串入主放电回路不同位置对放电的影响,考虑电磁线圈绝缘要求,提出将电磁线圈串入放电电源负极性端,整体电路设计可使放电可靠。性能对比实验表明,自励模式与他励模式性能接近,在放电电压为420V时,自励模式最高效率达到61%。自励模式实验获得了稳定放电,且放电电流低频振荡幅值很小。 相似文献
249.
250.
Tuanhui Zhou Haisheng Ji Guangli Huang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(8):1195-1201
In this paper, we analyze the footpoint motion of two large solar flares using observations made by the Transition Region and Coronal Explorer (TRACE) and Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The two flares are the M5.7 flare of March 14, 2002 and the X10 flare of October 29, 2003. They are both classical two-ribbon flares as observed in TRACE 1600 or 171 Å images and have long-duration conjugate hard X-ray (HXR) footpoint emission. We use the ‘center-of-mass’ method to locate the centroids of the UV/EUV flare ribbons. The results are: (1) The conjugate UV/EUV ribbons and HXR footpoints of the two flares show a converging (inward) motion during the impulsive phase. For the two flares, the converging motion lasts about 3 and 10 min, respectively. The usual separation (outward) motion for the flare ribbons and footpoints take place only after the converging motion. (2) During the inward and the outward motion, the conjugate ribbons and footpoints of the two events exhibit a strong unshear motion. In obtaining above results, TRACE UV/EUV and RHESSI HXR data show an overall agreement. The two events demonstrate that the magnetic reconnection for the flares occurs in highly sheared magnetic field. Furthermore, the results support the magnetic model constructed by Ji et al. [Ji, H., Huang, G., Wang, H. Astrophys. J. 660, 893–900, 2007], who proposed that the contracting motion of flaring loops is the signature of the relaxation of sheared magnetic fields. 相似文献