全文获取类型
收费全文 | 7204篇 |
免费 | 25篇 |
国内免费 | 16篇 |
专业分类
航空 | 3688篇 |
航天技术 | 2357篇 |
综合类 | 193篇 |
航天 | 1007篇 |
出版年
2021年 | 55篇 |
2019年 | 45篇 |
2018年 | 114篇 |
2017年 | 65篇 |
2016年 | 68篇 |
2014年 | 121篇 |
2013年 | 148篇 |
2012年 | 162篇 |
2011年 | 241篇 |
2010年 | 164篇 |
2009年 | 271篇 |
2008年 | 309篇 |
2007年 | 171篇 |
2006年 | 140篇 |
2005年 | 156篇 |
2004年 | 170篇 |
2003年 | 215篇 |
2002年 | 229篇 |
2001年 | 284篇 |
2000年 | 145篇 |
1999年 | 179篇 |
1998年 | 221篇 |
1997年 | 152篇 |
1996年 | 203篇 |
1995年 | 243篇 |
1994年 | 219篇 |
1993年 | 133篇 |
1992年 | 174篇 |
1991年 | 85篇 |
1990年 | 90篇 |
1989年 | 182篇 |
1988年 | 90篇 |
1987年 | 84篇 |
1986年 | 77篇 |
1985年 | 219篇 |
1984年 | 186篇 |
1983年 | 162篇 |
1982年 | 175篇 |
1981年 | 206篇 |
1980年 | 79篇 |
1979年 | 68篇 |
1978年 | 73篇 |
1977年 | 56篇 |
1976年 | 52篇 |
1975年 | 75篇 |
1974年 | 61篇 |
1972年 | 77篇 |
1971年 | 59篇 |
1970年 | 41篇 |
1969年 | 45篇 |
排序方式: 共有7245条查询结果,搜索用时 78 毫秒
331.
D. V. Kurylev 《Russian Aeronautics (Iz VUZ)》2016,59(2):287-292
This paper deals with roughing milling of vane channels for axial blisks by a cup tool. The effect of the shaping strategy on waviness of the surfaces being machined and allowance for subsequent operations is determined. 相似文献
332.
S. Mereghetti A. Tiengo P. Esposito G. Vianello A. De Luca D. Götz G. Weidenspointner A. von Kienlin G.L. Israel L. Stella N. Rea R. Turolla S. Zane 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
We describe the results obtained with Target of Opportunity observations of the galactic sources SGR 1627–41 and 1E 1547–5408. These two transients show several similarities supporting the interpretation of Anomalous X-ray Pulsars and Soft Gamma-ray Repeaters as a single class of strongly magnetized neutron stars. 相似文献
333.
P.T. Gallagher C.A. Young J.P. Byrne R.T.J. McAteer 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Coronal mass ejections (CMEs) are large-scale eruptions of plasma and magnetic field that can produce adverse space weather at Earth and other locations in the Heliosphere. Due to the intrinsic multiscale nature of features in coronagraph images, wavelet and multiscale image processing techniques are well suited to enhancing the visibility of CMEs and suppressing noise. However, wavelets are better suited to identifying point-like features, such as noise or background stars, than to enhancing the visibility of the curved form of a typical CME front. Higher order multiscale techniques, such as ridgelets and curvelets, were therefore explored to characterise the morphology (width, curvature) and kinematics (position, velocity, acceleration) of CMEs. Curvelets in particular were found to be well suited to characterising CME properties in a self-consistent manner. Curvelets are thus likely to be of benefit to autonomous monitoring of CME properties for space weather applications. 相似文献
334.
335.
Mosbeh R. Kaloop Mosaruf Hussan Dookie Kim 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(11):3505-3521
This study aims at assessing the safety behavior of the Incheon long-span bridge using high rate (10?Hz) geodetic monitoring global positioning system (GPS). The time series of wavelet spectrum analysis is utilized to assess the dynamic behavior of the bridge. The coefficients and model errors of the time series autoregressive-moving average (ARMA) model are used to evaluate the movement performances of the bridge. The results show that: (i) the accuracy of GPS measurements to extract the dynamic behavior of the bridge is 97.27% when compared with the design results. (ii) the behavior of the bridge is within the safety limits of the bridge design with minimum observed changes for the historical GPS measurements in time and frequency domains, the mean deflection of bridge deck is 8.26?mm and frequency changes of bridge is 0.004?Hz compared with the design results. (iii) the time series analysis of the wavelet spectrum and ARMA model coefficients can be used to detect the significant frequency changes and study the rigidity of the bridge performance, respectively; and the both methods are found to be suitable techniques to estimate the performance changes of the GPS measurements in the time and frequency domains during the monitoring time period. 相似文献
336.
The paper presents a technique of forming and evaluating the allowable clearance between a launch vehicle fairing and spacecraft. 相似文献
337.
M.R. Saradjian M. Hosseini 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
In the past studies, different soil moisture estimation models were developed for bare soil areas by using remotely-sensed data. However, there are few models that can be used to estimate soil moisture in vegetated areas. Water Cloud Model (WCM) model is a widely used soil moisture estimation model has been developed for vegetated areas. In this study, the WCM model was extended to take soil roughness parameter into consideration. The modeling and its accuracy assessment were done by using multi-polarization Airborne Synthetic Aperture Radar (AIRSAR) images and ground data collected during field Soil Moisture Experiments. 相似文献
338.
This paper considers the axisymmetric transverse vibrations of aircraft nonuniform structural elements that are introduced by a thermal shock. Analytical solutions have been obtained and their numerical analysis has been performed. 相似文献
339.
V.D. Kuznetsov I.I. Sobelman I.A. Zhitnik S.V. Kuzin Yu.D. Kotov Yu.E. Charikov S.N. Kuznetsov E.P. Mazets A.A. Nusinov A.M. Pankov J. Sylwester 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The CORONAS-F mission experiments and results have been reviewed. The observations with the DIFOS multi-channel photometer in a broad spectral range from 350 to 1500 nm have revealed the dependence of the relative amplitudes of p-modes of the global solar oscillations on the wavelength that agrees perfectly well with the earlier data obtained in a narrower spectral ranges. The SPIRIT EUV observations have enabled the study of various manifestations of solar activity and high-temperature events on the Sun. The data from the X-ray spectrometer RESIK, gamma spectrometer HELICON, flare spectrometer IRIS, amplitude–temporal spectrometer AVS-F, and X-ray spectrometer RPS-1 have been used to analyze the X- and gamma-ray emission from solar flares and for diagnostics of the flaring plasma. The absolute and relative content of various elements (such as potassium, argon, and sulfur) of solar plasma in flares has been determined for the first time with the X-ray spectrometer RESIK. The Solar Cosmic Ray Complex monitored the solar flare effects in the Earth’s environment. The UV emission variations recorded during solar flares in the vicinity of the 120-nm wavelength have been analyzed and the amplitude of relative variations has been determined. 相似文献
340.
R.N.C. Eze 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Hard X-ray emitting symbiotic stars are candidates for SN Ia progenitors. The importance of Type Ia SNe as standard candles for cosmology makes the study of their progenitor systems particularly important. Additionally, they provide one of the most promising laboratories for the study of astrophysical jets. Typically, the X-ray emission in these systems is modeled with a collisional plasma model, sometimes with an emission measure distribution taken from a cooling flow model. The lack of any coherent periods in both X-rays and optical wave band strongly suggests that the accreting white dwarfs in the hard X-ray symbiotic stars are non-magnetic. Although relatively few have been discovered to date, but we believe that there are very many of them in our galaxy and could be possible candidates for the Galactic Ridge X-ray Emissions (GRXE). 相似文献