全文获取类型
收费全文 | 2707篇 |
免费 | 5篇 |
国内免费 | 8篇 |
专业分类
航空 | 1324篇 |
航天技术 | 924篇 |
综合类 | 11篇 |
航天 | 461篇 |
出版年
2021年 | 20篇 |
2019年 | 17篇 |
2018年 | 109篇 |
2017年 | 63篇 |
2016年 | 40篇 |
2015年 | 14篇 |
2014年 | 58篇 |
2013年 | 97篇 |
2012年 | 56篇 |
2011年 | 100篇 |
2010年 | 78篇 |
2009年 | 122篇 |
2008年 | 146篇 |
2007年 | 68篇 |
2006年 | 69篇 |
2005年 | 72篇 |
2004年 | 65篇 |
2003年 | 87篇 |
2002年 | 44篇 |
2001年 | 97篇 |
2000年 | 50篇 |
1999年 | 66篇 |
1998年 | 69篇 |
1997年 | 67篇 |
1996年 | 65篇 |
1995年 | 88篇 |
1994年 | 86篇 |
1993年 | 45篇 |
1992年 | 51篇 |
1991年 | 15篇 |
1990年 | 24篇 |
1989年 | 51篇 |
1988年 | 34篇 |
1987年 | 22篇 |
1986年 | 28篇 |
1985年 | 74篇 |
1984年 | 70篇 |
1983年 | 43篇 |
1982年 | 69篇 |
1981年 | 67篇 |
1980年 | 19篇 |
1979年 | 10篇 |
1978年 | 31篇 |
1977年 | 12篇 |
1975年 | 24篇 |
1974年 | 16篇 |
1973年 | 16篇 |
1972年 | 16篇 |
1970年 | 9篇 |
1969年 | 12篇 |
排序方式: 共有2720条查询结果,搜索用时 27 毫秒
131.
A.K. Sharma O.B. Gurav Anindya Bose H.P. Gaikwad G.A. Chavan Atanu Santra S.S. Kamble R.S. Vhatkar 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(10):3131-3138
Indian Space Research Organization (ISRO) has developed an indigenous system named Indian Regional Navigation Satellite System (IRNSS) or NavIC (Navigation with Indian Constellation), that consists of 7 satellites and transmits navigation signal in L and S bands. ISRO, for validation of the system, has installed many IGS (IRNSS/GPS/SBAS) receivers scattered over the Indian region. Using preliminary data from two geographically widely separated stations over India, this paper presents the results on studies on parameters of IRNSS signal quality and discusses how these parameters may be used to study the ionospheric behavior over the Indian region. The results show the importance and advantages of using IRNSS data for such studies. 相似文献
132.
Cosmic Research - An Erratum to this paper has been published: https://doi.org/10.1134/S0010952521120017 相似文献
133.
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
134.
135.
Y. Wu D.Y. Yang P.F. Tu Y.Z. Tian Y.H. Guo X.M. Wang X.B. Li 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The dried, fleshy stems of Cistanche deserticola (Orobanchaceae) are popular tonics in Traditional Chinese Medicine (TCM) to treat the inability of kidney in expelling extra fluid in the body, causing fluid retention, and reform reproductive system. However, the wild plants of C. deserticola have become endangered due to habitat downsizing and over-harvesting for its medicinal usages. The present research was carried out for the following purposes: (1) promoting the space-breeding research; (2) providing molecular evidence for agricultural selective breeding; and (3) protecting this endangered herbal medicine and conserving its genetic resources. 相似文献
136.
The paper describes a device and a technique of forming the information processing algorithms used in the integrated acoustic monitoring system for jet fuel tanks, intended for monitoring the level, density and mass of liquid products. 相似文献
137.
Yu. A. Gravchenko B. K. Grankin V. V. Kozlov S. V. Chirva 《Russian Aeronautics (Iz VUZ)》2017,60(3):327-334
The paper adduces the relators for algebraic operations on graphs using the numeric codes of the graphs. The special algebra of codes has been devised with consideration of the principles of graph transformation. This paper demonstrates the relevance of numeric coding of graphs for solving the problems of enumeration, systematization, and compact representation of the information about the structural and functional characteristics of the systems of flow distribution and conversion of rocket and space technology and for conducting the modeling transformations of given systems in the course of the structural and functional studies as well. 相似文献
138.
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
139.
Marco B. Quadrelli Paul Backes W. Keats Wilkie Lou Giersch Ubaldo Quijano Jason Keim Daniel Scharf Rudranarayan Mukherjee S. Case Bradford Michael McKee 《Acta Astronautica》2011,68(7-8):947-973
This paper summarizes the modeling, simulation, and testing work related to the development of technology to investigate the potential that shape memory actuation has to provide mechanically simple and affordable solutions for delivering assets to a surface and for sample capture and possible return to Earth. We investigate the structural dynamics and controllability aspects of an adaptive beam carrying an end-effector which, by changing material equilibrium phases, is able to actively decouple the end-effector dynamics from the spacecraft dynamics during the surface contact phase. Asset delivery and sample capture and return are at the heart of several emerging potential missions to small bodies, such as asteroids and comets, and to the surface of large bodies, such as Titan. 相似文献
140.
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