全文获取类型
收费全文 | 9205篇 |
免费 | 35篇 |
国内免费 | 36篇 |
专业分类
航空 | 4553篇 |
航天技术 | 3328篇 |
综合类 | 39篇 |
航天 | 1356篇 |
出版年
2021年 | 66篇 |
2019年 | 71篇 |
2018年 | 131篇 |
2017年 | 77篇 |
2016年 | 74篇 |
2014年 | 178篇 |
2013年 | 236篇 |
2012年 | 207篇 |
2011年 | 290篇 |
2010年 | 205篇 |
2009年 | 345篇 |
2008年 | 427篇 |
2007年 | 248篇 |
2006年 | 219篇 |
2005年 | 242篇 |
2004年 | 200篇 |
2003年 | 299篇 |
2002年 | 186篇 |
2001年 | 300篇 |
2000年 | 178篇 |
1999年 | 216篇 |
1998年 | 250篇 |
1997年 | 179篇 |
1996年 | 244篇 |
1995年 | 310篇 |
1994年 | 304篇 |
1993年 | 178篇 |
1992年 | 209篇 |
1991年 | 121篇 |
1990年 | 102篇 |
1989年 | 239篇 |
1988年 | 96篇 |
1987年 | 106篇 |
1986年 | 107篇 |
1985年 | 315篇 |
1984年 | 261篇 |
1983年 | 214篇 |
1982年 | 238篇 |
1981年 | 297篇 |
1980年 | 95篇 |
1979年 | 90篇 |
1978年 | 84篇 |
1977年 | 82篇 |
1975年 | 79篇 |
1974年 | 65篇 |
1973年 | 65篇 |
1972年 | 76篇 |
1971年 | 62篇 |
1970年 | 67篇 |
1969年 | 62篇 |
排序方式: 共有9276条查询结果,搜索用时 281 毫秒
411.
E. G. Dem’yanenko 《Russian Aeronautics (Iz VUZ)》2014,57(2):204-211
In this paper, a new technique for shaping the thin-walled barrel-type parts is presented. 相似文献
412.
G. Gaias J.-S. Ardaens C. Colombo 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(11):3515-3526
This work presents a precise analytical model to reconstruct the line-of-sight vector to a target satellite over time, as required by angles-only relative navigation systems for application to rendezvous missions. The model includes the effects of the geopotential, featuring: the analytical propagation in the mean relative orbital elements (up to second-order expansion), the analytical two-way osculating/mean orbital elements’ conversion (second-order in and up to a given degree and order of the geopotential), and a second-order mapping from the perturbed osculating elements’ set to the local orbital frame. Performances are assessed against the line-of-sight reconstructed out of the precise GPS-based positioning products of the PRISMA mission. The line-of-sight modelled over a far-range one day long scenario can be fitted against the true one presenting residuals of the order of ten arc-seconds, which is below the typical sensor noise at far-range. 相似文献
413.
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
414.
V.E. Kunitsyn A.M. Padokhin A.E. Vasiliev G.A. Kurbatov V.L. Frolov G.P. Komrakov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The purpose of this work is to report the experimental evidences for the influence of perturbations in the electron density in the dayside mid-latitude ionosphere, that are caused by high-frequency heating of the F2 layer, on the GNSS signals. The experiments were carried out at the Sura heater (Radio Physical Research Institute, N. Novgorod). During the sessions of ionospheric heating with different time modulations of the radiated power the rays linking the navigational satellites with the ground receiver intersected the heated region. Variations in the total electron content (TEC) were studied; these variations are proportional to the reduced phases of navigational signals. It is shown that with the square-wave modulation of the radiated power (with periods of 1, 6, 10 and 15 min), perturbations with periods of the main modulation of heating and its harmonics appear in the spectrum of TEC variations. Examples are presented of identification of the heating-induced variations in TEC, including determination of the amplitudes and time characteristics of these variations. 相似文献
415.
The paper highlights significance of the interturbine transition duct as part of the high pressure and low pressure turbine spool. The correlations have been suggested allowing us to estimate variation of the average cross section flow swirl while its passing the interturbine transition duct. 相似文献
416.
417.
I. Martínez J.M. Perales 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The experimental results obtained in experiment “STACO” made on board the Spacelab D-2 are re-visited, with image-analysis tools not then available. The configuration consisted of a liquid bridge between two solid supporting discs. An expected breakage occurred during the experiment. The recorded images are analysed and the measured behaviour compared with the results of a three dimensional model of the liquid dynamics, obtaining a much better fit than with linear models. 相似文献
418.
Paul A. Crowther Joanne L. Bibby James P. Furness J. Simon Clark 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
We highlight how the downward revision in the distance to the star cluster associated with SGR 1806–20 by Bibby et al. (2008) reconciles the apparent low contamination of BATSE short GRBs by intense flares from extragalactic magnetars without recourse to modifying the frequency of one such flare per 30 years per Milky Way galaxy. We also discuss the variety in progenitor initial masses of magnetars based upon cluster ages, ranging from ∼50 M⊙ for SGR 1806–20 and AXP CXOU J164710.2–455216 in Westerlund 1 to ∼17 M⊙ for SGR 1900+14 according to Davies et al. (2009) and presumably also 1E 1841–045 if it originated from one of the massive RSG clusters #2 or #3. 相似文献
419.
C. J. Hansen M. A. Caplinger A. Ingersoll M. A. Ravine E. Jensen S. Bolton G. Orton 《Space Science Reviews》2017,213(1-4):475-506
Junocam is a wide-angle camera designed to capture the unique polar perspective of Jupiter offered by Juno’s polar orbit. Junocam’s four-color images include the best spatial resolution ever acquired of Jupiter’s cloudtops. Junocam will look for convective clouds and lightning in thunderstorms and derive the heights of the clouds. Junocam will support Juno’s radiometer experiment by identifying any unusual atmospheric conditions such as hotspots. Junocam is on the spacecraft explicitly to reach out to the public and share the excitement of space exploration. The public is an essential part of our virtual team: amateur astronomers will supply ground-based images for use in planning, the public will weigh in on which images to acquire, and the amateur image processing community will help process the data. 相似文献
420.
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