全文获取类型
收费全文 | 354篇 |
免费 | 10篇 |
国内免费 | 2篇 |
专业分类
航空 | 10篇 |
航天技术 | 349篇 |
综合类 | 1篇 |
航天 | 6篇 |
出版年
2023年 | 7篇 |
2022年 | 1篇 |
2021年 | 16篇 |
2020年 | 16篇 |
2019年 | 16篇 |
2018年 | 22篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 35篇 |
2013年 | 41篇 |
2012年 | 16篇 |
2011年 | 41篇 |
2010年 | 25篇 |
2009年 | 42篇 |
2008年 | 39篇 |
2007年 | 3篇 |
2006年 | 2篇 |
2005年 | 6篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1990年 | 1篇 |
排序方式: 共有366条查询结果,搜索用时 15 毫秒
161.
Space Science Reviews - In this review, we examine four specific questions/issues of contemporary interest within the overall topic of ionospheric plasma outflow into the magnetosphere. These four... 相似文献
162.
163.
164.
Long-Song He Jin-Song Ping 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The occurrence characteristics of medium-scale travelling ionospheric disturbances (MSTIDs) were investigated using the Tasman International Geospace Environment Radar (TIGER). From the occurrence study of sea echoes, we found two maxima, one pre-noon and the other after noon. They are less obvious with increase of magnetic activities, and more obvious when Bz is northwards. It is suggested that this maxima were related to fore- and after-noon maxima in the distribution of net field-aligned currents flowing from the magnetosphere to the ionosphere, and that these two regions were sources of atmospheric gravity waves (AGWs) due to enhancement of Hall conductivities in the ionosphere. The Lorentz force is suggested to be a possible mechanism for the excitation of MSTIDs in the dayside ionosphere. 相似文献
165.
A.D. Danilov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(1):102-110
The analysis of the behavior of the critical frequency foF2 during the 24th solar activity cycle (Danilov and Konstantinova, 2020a, c) is prolonged for two more months and the nighttime hours. In addition to the Rz and Ly-α indices used in the aforementioned papers for correction of the F10.7 index during the 24th cycle, the commonly used Mg II index is added. The results confirm the previous conclusions on the existence of the “vague” period with chaotic behavior of foF2 and the recovery of the negative trend in foF2 after 2008–2010. A comparison of the F10.7 index with three other SA indices (Ly-α, Rz, and Mg II) for the 22nd, 23rd, and 24th SA cycles is performed. It is shown that the relationship between F10.7 and other indices is close in the 22nd and 23rd cycles but differs from that in the 24th cycle. The corrected values of F10.7 in the 24th cycle are proposed for analysis of ionospheric trends during that cycle. 相似文献
166.
A. Carrillo-Vargas R. Pérez-Enríquez Mario Rodríguez-Martínez R. López-Montes G.A. Casillas-Pérez E.A. Araujo-Pradere 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
The radio telescope MEXART was developed to make observations of interplanetary scintillation (IPS) produced by large scale disturbances associated with solar events. In this work it is shown that on occasion there are disturbances in the ionosphere that are related with these events and which cannot only contaminate the IPS but actually be the main contribution to the observed oscillations. This was the case of the event of 15 December 2006 observed by MEXART, which presented clear scintillation. The total electron content (TEC) of the ionosphere above Mexico was calculated for the same period. It was found that the variations in TEC were associated with the scintillations detected by MEXART. 相似文献
167.
Irfan Azeem Michael Barlage 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(7):1931-1941
Ionospheric variability impacts operational performances of a variety of technological systems, such as HF communication, Global Positioning System (GPS) navigation, and radar surveillance. The ionosphere is not only perturbed by geomagnetic inputs but is also influenced by atmospheric tides and other wave disturbances propagating from the troposphere to high altitudes. Atmospheric Gravity Waves (AGWs) excited by meteorological sources are one of the largest sources of mesoscale variability in the ionosphere. In this paper, Total Electron Content (TEC) data from networks of GPS receivers in the United States are analyzed to investigate AGWs in the ionosphere generated by convective thunderstorms. Two case studies of convectively generated gravity waves are presented. On April 4, 2014 two distinct large convective systems in Texas and Arkansas generated two sets of concentric AGWs that were observed in the ionosphere as Traveling Ionospheric Disturbances (TIDs). The period of the observed TIDs was 20.8 min, the horizontal wavelength was 182.4 km, and the horizontal phase speed was 146.4 m/s. The second case study shows TIDs generated from an extended squall line on December 23, 2015 stretching from the Gulf of Mexico to the Great Lakes in North America. Unlike the concentric wave features seen in the first case study, the extended squall line generated TIDs, which exhibited almost plane-parallel phase fronts. The TID period was 20.1 min, its horizontal wavelength was 209.6 km, and the horizontal phase speed was 180.1 m/s. The AGWs generated by both of these meteorological events have large vertical wavelength (>100 km), which are larger than the F2 layer thickness, thus allowing them to be discernible in the TEC dataset. 相似文献
168.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(3):933-942
This study uses the 3D ray tracing to analyse ionospheric disturbance generated by a ballistic missile plume (which was simulated in our previous work). Ray tracing results show that the 6 MHz radio waves are completely reflected by the ionosphere and cannot reach the ionospheric disturbance zone. The 8 MHz radio waves partially penetrate the ionospheric disturbance zone, producing a focusing effect. Most of the 10 MHz radio waves pass through the ionosphere and the disturbance zone. The focusing effect and focus height are reduced. In the height range 65̃400 km, the ray absorption loss of reflection is greater than the transmitted ray. When the ray is reflected multiple times in the cavity formed by the plume, ray absorption loss greatly increases. 相似文献
169.
P.O. Amaechi E.O. Oyeyemi A.O. Akala 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(8):2074-2090
The study investigated the effects of intense geomagnetic storms of 2015 on the occurrences of large scale ionospheric irregularities over the African equatorial/low-latitude region. Four major/intense geomagnetic storms of 2015 were analyzed for this study. These storms occurred on 17th March 2015 (?229?nT), 22nd June 2015 (?204?nT), 7th October 2015 (?124?nT), and 20th December 2015 (?170?nT). Total Electron Content (TEC) data obtained from five African Global Navigation Satellite Systems (GNSS) stations, grouped into eastern and western sectors were used to derive the ionospheric irregularities proxy indices, e.g., rate of change of TEC (ROT), ROT index (ROTI) and ROTI daily average (ROTIAVE). These indices were characterized alongside with the disturbance storm time (Dst), the Y component of the Interplanetary Electric Field (IEFy), polar cap (PC) index and the H component of the Earth’s magnetic field from ground-based magnetometers. Irregularities manifested in the form of fluctuations in TEC. Prompt penetration of electric field (PPEF) and disturbance dynamo electric field (DDEF) modulated the behaviour of irregularities during the main and recovery phases of the geomagnetic storms. The effect of electric field over both sectors depends on the local time of southward turning of IMF Bz. Consequently, westward electric field inhibited irregularities during the main phase of March and October 2015 geomagnetic storms, while for the June 2015 storm, eastward electric field triggered weak irregularities over the eastern sector. The effect of electric field on irregularities during December 2015 storm was insignificant. During the recovery phase of the storms, westward DDEF suppressed irregularities. 相似文献
170.
N.V. Bakhmetieva V.L. Frolov V.D. Vyakhirev E.E. Кalinina A.D. Akchurin E.Yu. Zykov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(7):1919-1930
The paper presents data from some campaigns at Sura heating facility in 2011–1016. The experiments on probing of the artificial disturbed region of the lower ionosphere were carried out at two observation sites. One of them was located near Vasil’sursk 1 km from Sura facility (56.1°N; 46.1°E) and the other site was located at the Observatory (55.85°N; 48.8°E) of Kazan State University, 170 km to the East. Investigation of the features of the disturbed region of the lower ionosphere based on its diagnostics by the methods of the vertical sounding and oblique backscattering is the main goal of this paper. Ionosphere disturbance was fulfilled by the effect of the powerful radio wave of the ordinary or extraordinary polarization emitted by transmitters of the Sura facility with effective radiated power ERP = 50–120 MW at the frequency of 4.3, 4.7 and 5.6 MHz. Pumping waves were emitted with period from 30 s to 15 min. The disturbed region of the ionosphere in Vasil’sursk was probed by the vertical sounding technique using the partial reflexion radar at the frequency of 2.95 and 4.7 MHz. For the oblique sounding of the disturbed region the modified ionosonde Cyclon-M, operating at ten frequencies from 2.01 to 6.51 MHz was used at the Observatory site. On many heating sessions simultaneous variations of the probing partial reflection signals in Vasil’sursk and backscattered signals in Observatory were observed at the height at 40–100 km below the reflection height of the pumping wave. These observations were correlated with the pumping periods of the Sura facility. Possible mechanisms of the appearance of the disturbance in the lower ionosphere and its effect on the probing radio waves are discussed. 相似文献