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181.
I.R. Petrova V.V. Bochkarev R.R. Latipov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
We present results of the spectral analysis of data series of Doppler frequency shifted signals reflected from the ionosphere, using experimental data received at Kazan University, Russia. Spectra of variations with periods from 1 min to 60 days have been calculated and analyzed for different scales of periods. The power spectral density for spring and winter differs by a factor of 3–4. Local maxima of variation amplitude are detected, which are statistically significant. The periods of these amplitude increases range from 6 to 12 min for winter, and from 24 to 48 min for autumn. Properties of spectra for variations with the periods of 1–72 h have been analyzed. The maximum of variation intensity for all seasons and frequencies corresponds to the period of 24 h. Spectra of variations with periods from 3 to 60 days have been calculated. The maxima periods of power spectral density have been detected by the MUSIC method for the high spectral resolution. The detected periods correspond to planetary wave periods. Analysis of spectra for days with different level of geomagnetic activity shows that the intensity of variations for days with a high level of geomagnetic activity is higher. 相似文献
182.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013,52(5):810-820
The highest Total Electron Content (TEC) values in the world normally occur at Equatorial Ionization Anomaly (EIA) region resulting in largest ionospheric range delay values observed for any potential Space Based Augmentation System (SBAS). Reliable forecasting of TEC is crucial for satellite based navigation systems. The day to day variability of the location of the anomaly peak and its intensity is very large. This imposes severe limitations on the applicability of commonly used ionospheric models to the low latitude regions. It is necessary to generate a mathematical ionospheric forecasting and mapping model for TEC based on physical ionospheric influencing parameters. A model, IRPE-TEC, has been developed based on real time low latitude total electron content data using GPS measurements from a number of stations situated around the northern crest of the EIA during 2007 through 2011 to predict the vertical TEC values during the low and moderate solar activity levels of the 24th solar cycle. This model is compared with standard ionospheric models like International Reference Ionosphere (IRI) and Parameterized Ionospheric Model (PIM) to establish its applicability in the equatorial region for accurate predictions. 相似文献
183.
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
184.
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186.
Daniele Bortoluzzi Pierre A. Mäusli Riccardo Antonello Philipp M. Nellen 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
In the frame of space missions, mechanisms often constitute critical systems whose functionality and performance need to be tested on ground before the mission launch. The LISA scientific space mission will detect gravitational waves by measuring the relative displacement of pairs of free-floating test masses set into geodesic motion onboard of three spacecrafts. Inside each satellite, the injection of the test masses from the caged configuration into the geodesic trajectory will be performed by the grabbing positioning and release mechanism. To provide a successful injection, the test masses must be dynamically released with a minimal residual velocity against adhesion with the holding device. A parameter that determines the test mass residual velocity is the quickness of the retraction of the holding device. The need arises then to characterize the dynamic response of the release mechanism in order to predict its behaviour in the in-flight conditions. Once a validated model of the mechanism is available, the compliance of the system to the tight requirement on the maximum allowed residual velocity of the test mass may be verified. Starting from an electro-mechanical model of the mechanism dynamics, this paper presents the results of the experimental identification of its relevant parameters. 相似文献
187.
砂轮形貌的激光功率谱特性及其检测 总被引:3,自引:0,他引:3
阐述了砂轮形貌的理论功率谱图象、实际功率谱图象及其功率谱特性,获得了砂轮形貌的特征参数与激光功率图象的对应关系。根据上述的理论分析,设计了激光功率谱法检测砂轮形貌的采样原理及检测装置。采用时,将砂轮一圈划分为256个等分点,每一点均进行功率谱型的采样;为检测方便,在对称的功率谱图象一侧采集8个点的光强,共获得由8个数据组成的256个离散功率谱型。通过对离散功率谱型的计算自理最后由检测装置打印出砂轮 相似文献
188.
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
189.
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
190.
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