全文获取类型
收费全文 | 8454篇 |
免费 | 9篇 |
国内免费 | 26篇 |
专业分类
航空 | 4369篇 |
航天技术 | 2823篇 |
综合类 | 202篇 |
航天 | 1095篇 |
出版年
2021年 | 55篇 |
2019年 | 49篇 |
2018年 | 102篇 |
2016年 | 50篇 |
2014年 | 135篇 |
2013年 | 191篇 |
2012年 | 180篇 |
2011年 | 266篇 |
2010年 | 175篇 |
2009年 | 293篇 |
2008年 | 348篇 |
2007年 | 198篇 |
2006年 | 190篇 |
2005年 | 201篇 |
2004年 | 178篇 |
2003年 | 251篇 |
2002年 | 251篇 |
2001年 | 315篇 |
2000年 | 165篇 |
1999年 | 205篇 |
1998年 | 256篇 |
1997年 | 181篇 |
1996年 | 239篇 |
1995年 | 298篇 |
1994年 | 270篇 |
1993年 | 165篇 |
1992年 | 199篇 |
1991年 | 118篇 |
1990年 | 107篇 |
1989年 | 217篇 |
1988年 | 102篇 |
1987年 | 108篇 |
1986年 | 101篇 |
1985年 | 281篇 |
1984年 | 225篇 |
1983年 | 192篇 |
1982年 | 203篇 |
1981年 | 275篇 |
1980年 | 98篇 |
1979年 | 78篇 |
1978年 | 89篇 |
1977年 | 70篇 |
1976年 | 68篇 |
1975年 | 89篇 |
1974年 | 70篇 |
1973年 | 62篇 |
1972年 | 87篇 |
1971年 | 75篇 |
1970年 | 63篇 |
1969年 | 64篇 |
排序方式: 共有8489条查询结果,搜索用时 31 毫秒
411.
Devajyoti Dutta Sanjay Sharma G.K. Sen B.A.M. Kannan S. Venketswarlu R.M. Gairola J. Das G. Viswanathan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
By using a Doppler Weather Radar (DWR) at Shriharikota (13.66°N & 80.23°E), an Artificial Neural Network (ANN) based technique is proposed to improve the accuracy of rain intensity estimation. Three spectral moments of a Doppler spectra are utilized as an input data to an ANN. Rain intensity, as measured by the tipping bucket rain gauges around the DWR station, are considered as a target values for the given inputs. Rain intensity as estimated by the developed ANN model is validated by the rain gauges measurements. With the help of a developed technique, reasonable improvement in the estimation of rain intensity is observed. By using the developed technique, root mean square error and bias are reduced in the range of 34–18% and 17–3% respectively, compared to Z–R approach. 相似文献
412.
An algorithm of analyzing the design parameters for a thin-walled wing from composite material based on the efficient distribution
of structural material between load-carrying elements is described. We consider the problems of convergence acceleration for
the iteration design analysis. Also presented are the examples of determining the design parameters for a superlight aircraft
wing and the rational parameters of the filler in the form of a three-dimensional rod structure. 相似文献
413.
We considered the influence of temperature on the nitric oxide emission under combustion of the near-stoichiometric mixtures
with and without water feed. We revealed the advantage of the method of fuel-water-air mixture combustion over that of the
leaned mixture combustion. 相似文献
414.
Systems for the indication and display of secondary information in avionics and autobasing complexes
A. A. Bagdasarov R. V. Anitropov O. V. Bagdasarova I. L. Livshits 《Russian Aeronautics (Iz VUZ)》2011,54(2):185-191
We consider the peculiarities of application for the cabin indicating systems of secondary information display, formulate
and systematize the compositional and technical requirements for display systems and their elements. The tendencies and lines
in the development of head-up displays for avionics and autobasing complexes were determined. The technique of calculating
optics of such display systems with the use of electronic distortion compensation is presented. 相似文献
415.
H.S. Ahluwalia J. Jackiewicz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
The decay phase of the sunspot cycle 23 exhibited two unusual features. First, it lasted too long. Second, the interplanetary magnetic field intensity at earth orbit reached the lowest value since in situ measurements in space began in October 1963. These physical anomalies significantly altered the early forecasts for the sunspot activity parameters for cycle 24, made by several colleagues. We note that there was a significant change in the solar behavior during cycle 22. We discuss the observed trends and their effect on our empirical solar activity forecast technique, leading to our prediction for cycle 24 parameters; cycle 24 will be only half as active as cycle 23, reaching its peak in May 2013. We speculate on the possible implications of this outcome on future earth climate change and the ensuing socio-economic consequences. 相似文献
416.
417.
J. Mazur L. Friesen A. Lin D. Mabry N. Katz Y. Dotan J. George J. B. Blake M. Looper M. Redding T. P. O’Brien J. Cha A. Birkitt P. Carranza M. Lalic F. Fuentes R. Galvan M. McNab 《Space Science Reviews》2013,179(1-4):221-261
The Relativistic Proton Spectrometer (RPS) on the Radiation Belt Storm Probes spacecraft is a particle spectrometer designed to measure the flux, angular distribution, and energy spectrum of protons from ~60 MeV to ~2000 MeV. RPS will investigate decades-old questions about the inner Van Allen belt proton environment: a nearby region of space that is relatively unexplored because of the hazards of spacecraft operation there and the difficulties in obtaining accurate proton measurements in an intense penetrating background. RPS is designed to provide the accuracy needed to answer questions about the sources and losses of the inner belt protons and to obtain the measurements required for the next-generation models of trapped protons in the magnetosphere. In addition to detailed information for individual protons, RPS features count rates at a 1-second timescale, internal radiation dosimetry, and information about electrostatic discharge events on the RBSP spacecraft that together will provide new information about space environmental hazards in the Earth’s magnetosphere. 相似文献
418.
R.?A.?KayumovEmail author I.?Z.?Mukhamedova E.?B.?Tuisina 《Russian Aeronautics (Iz VUZ)》2016,59(4):452-459
This paper considers a beam with a technological longitudinal section on the level of the gravity center of the cross section that is loaded by a vertical concentrated force. We study the structure durability depending on the load amplitude and the initial crack length. 相似文献
419.
420.