全文获取类型
收费全文 | 694篇 |
免费 | 1篇 |
国内免费 | 8篇 |
专业分类
航空 | 271篇 |
航天技术 | 227篇 |
综合类 | 4篇 |
航天 | 201篇 |
出版年
2021年 | 7篇 |
2019年 | 8篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2014年 | 19篇 |
2013年 | 34篇 |
2012年 | 16篇 |
2011年 | 48篇 |
2010年 | 26篇 |
2009年 | 44篇 |
2008年 | 45篇 |
2007年 | 26篇 |
2006年 | 26篇 |
2005年 | 24篇 |
2004年 | 14篇 |
2003年 | 23篇 |
2002年 | 16篇 |
2001年 | 14篇 |
2000年 | 16篇 |
1999年 | 11篇 |
1998年 | 18篇 |
1997年 | 8篇 |
1996年 | 11篇 |
1995年 | 15篇 |
1994年 | 7篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 15篇 |
1985年 | 24篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 17篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1973年 | 5篇 |
1972年 | 2篇 |
1971年 | 5篇 |
1970年 | 4篇 |
1969年 | 2篇 |
1968年 | 7篇 |
1967年 | 8篇 |
1966年 | 3篇 |
排序方式: 共有703条查询结果,搜索用时 31 毫秒
631.
A.H. Maghrabi H. Al Harbi Z.A. Al-Mostafa M.N. Kordi S.M. Al-Shehri 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
A single channel cosmic ray muon detector was constructed and installed in Riyadh, central Saudi Arabia, for studying the variations in the cosmic ray (CR) muon flux. The detector has been in operation since July 2002. The recorded data correspond to muons that primarily have energies between 10 and 20 GeV. The detector will be used to continuously measure the intensity of the muon components of the cosmic rays, exploring its variations and possible correlations with environment parameters. The technical aspects of this detector will be presented. Some results obtained by the detector so far will be given. These include the modulation of the CR flux on different time scales (diurnal, 27-day, and long-term variations). Additionally, the effect of a severe dust storm on the muon count rate was investigated. 相似文献
632.
Non-statistical formulation of the problem of determining the future position of an object in circumterrestrial space orbiting
around the Earth is considered at some constraints on measurement errors. Criteria of optimality and the algorithms satisfying
these criteria are presented. Computational schemes are given for the most interesting (for practical purposes) central and
projective algorithms. Using mathematical simulation methods the precision characteristics of these algorithms are determined
at different distributions of measurement errors for typical situations, arising when one supports a catalog of space objects.
It is shown that the errors of determining the predicted position of a space object, obtained with the non-statistical approach,
can be less than the errors of the least squares method. 相似文献
633.
John E. Moores Raymond Francis Marianne Mader G.R. Osinski T. Barfoot N. Barry G. Basic M. Battler M. Beauchamp S. Blain M. Bondy R-D. Capitan A. Chanou J. Clayton E. Cloutis M. Daly C. Dickinson H. Dong R. Flemming P. Furgale J. Gammel N. Gharfoor M. Hussein R. Grieve H. Henrys P. Jaziobedski A. Lambert K. Leung C. Marion E. McCullough C. McManus C.D. Neish H.K. Ng A. Ozaruk A. Pickersgill L.J. Preston D. Redman H. Sapers B. Shankar A. Singleton K. Souders B. Stenning P. Stooke P. Sylvester L. Tornabene 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
634.
The geomagnetic signal contains an enormous temporal range—from geomagnetic jerks on time scales of less than a year to the evolution of Earth’s dipole moment over billions of years. This review compares observations and numerical models of the long-term range of that signal, for periods much larger than the typical overturn time of Earth’s core. On time scales of 105–109 years, the geomagnetic field reveals the control of mantle thermodynamic conditions on core dynamics. We first briefly describe the general formalism of numerical dynamo simulations and available paleomagnetic data sets that provide insight into paleofield behavior. Models for the morphology of the time-averaged geomagnetic field over the last 5 million years are presented, with emphasis on the possible departures from the geocentric axial dipole hypothesis and interpretations in terms of core dynamics. We discuss the power spectrum of the dipole moment, as it is a well-constrained aspect of the geomagnetic field on the million year time scale. We then summarize paleosecular variation and intensity over the past 200 million years, with emphasis on the possible dynamical causes for the occurrence of superchrons. Finally, we highlight the geological evolution of the geodynamo in light of the oldest paleomagnetic records available. A summary is given in the form of a tentative classification of well-constrained observations and robust numerical modeling results. 相似文献
635.
A.Z. Bochev A.K. Sinha 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
We show examples of long period Pc5 magnetic field pulsations near field-aligned current (FAC) regions in the high-latitude magnetosphere, observed by INTERBALL-Au, and coordinated with POLAR, GOES-9 and ground-based observations during 11 January and 11 April 1997. Identification of corresponding magnetosphere regions and subregions is provided by electrons and protons in the energy-range of 0.01–100 keV measured onboard the spacecraft. The ULF Pc5 wave occurrence is observed in both upward and downward FACs. A fairly good correlation is demonstrated between these ULF Pc5 waves and the consecutive injection of magnetosheath low energy protons. The constancy of the observed frequency peak at 1.8 mHz during quite unsteady solar wind pressure conditions could be reconciled with the surface wave mode model. The 3.1 mHz peak location area probably resembles field-line fluctuations with an interesting appearance of poloidal mode oscillation. It is suggested that the 1.3 mHz wave and its harmonic 2.6 mHz represent global compressional oscillations. 相似文献
636.
Blinn John C. Campbell James P. 《IEEE transactions on aerospace and electronic systems》1966,(5):585-590
This paper discusses the results of an analytic study of the feasibility of using microwave radiometry as a technique for navigation data sensing in Army aircraft. The study included a review of Army aircraft characteristics and navigation requirements. Various means of sensing passively aircraft velocity, altitude, and velocity-altitude ratio were considered. While there appears to be no practical method for direct measurement of either velocity or altitude separately, it does appear possible to measure velocity-altitude ratio by comparing radiometric signals received from the terrain along the aircraft ground track. When combined with a radar altimeter, such a sensor could yield navigation data compatible with Army aircraft requirements. Microwave radiometry may also be the basis for direction sensing (to known landmarks) in high-flying aircraft or satellites. 相似文献
638.
John B. Rogerson Jr. 《Space Science Reviews》1963,2(5):621-652
A review is presented of the Orbiting Astronomical Observatories Program together with a detailed of the OAO spacecraft and the four astronomical instruments currently being developed for the first three observations. 相似文献
639.
D'Antonio R. A. Gaffney John E. 《IEEE transactions on aerospace and electronic systems》1968,(5):728-732
This paper describes a radio interferometer that can be employed for beaming and attitude determination. It differs from conventional interferometers in that it employs a carrier modulated by a pseudonoise sequence. This enables it to provide an unambiguous angular resolution of the signal source. 相似文献
640.
Robert C. Singleterry Steve R. Blattnig Martha S. Clowdsley Garry D. Qualls Chris A. Sandridge Lisa C. Simonsen Tony C. Slaba Steven A. Walker Francis F. Badavi Jan L. Spangler Aric R. Aumann E. Neal Zapp Robert D. Rutledge Kerry T. Lee Ryan B. Norman John W. Norbury 《Acta Astronautica》2011,68(7-8):1086-1097
OLTARIS (On-Line Tool for the Assessment of Radiation In Space) is a space radiation analysis tool available on the World Wide Web. It can be used to study the effects of space radiation for various spacecraft and mission scenarios involving humans and electronics. The transport is based on the HZETRN transport code and the input nuclear physics model is NUCFRG. This paper describes the tools behind the web interface and the types of inputs required to obtain results. Typical inputs are mission parameters and slab definitions or vehicle thickness distributions. Radiation environments can be chosen by the user. This paper describes these inputs as well as the output response functions including dose, dose equivalent, whole body effective dose equivalent, LET spectra and detector response models. 相似文献