全文获取类型
收费全文 | 4831篇 |
免费 | 2篇 |
国内免费 | 11篇 |
专业分类
航空 | 2519篇 |
航天技术 | 1556篇 |
综合类 | 183篇 |
航天 | 586篇 |
出版年
2021年 | 29篇 |
2018年 | 68篇 |
2017年 | 36篇 |
2016年 | 40篇 |
2014年 | 74篇 |
2013年 | 101篇 |
2012年 | 107篇 |
2011年 | 159篇 |
2010年 | 102篇 |
2009年 | 182篇 |
2008年 | 193篇 |
2007年 | 114篇 |
2006年 | 89篇 |
2005年 | 86篇 |
2004年 | 115篇 |
2003年 | 139篇 |
2002年 | 180篇 |
2001年 | 200篇 |
2000年 | 93篇 |
1999年 | 123篇 |
1998年 | 154篇 |
1997年 | 99篇 |
1996年 | 138篇 |
1995年 | 168篇 |
1994年 | 146篇 |
1993年 | 95篇 |
1992年 | 122篇 |
1991年 | 57篇 |
1990年 | 63篇 |
1989年 | 125篇 |
1988年 | 58篇 |
1987年 | 60篇 |
1986年 | 51篇 |
1985年 | 152篇 |
1984年 | 120篇 |
1983年 | 108篇 |
1982年 | 117篇 |
1981年 | 153篇 |
1980年 | 56篇 |
1979年 | 46篇 |
1978年 | 57篇 |
1977年 | 37篇 |
1976年 | 40篇 |
1975年 | 48篇 |
1974年 | 39篇 |
1973年 | 25篇 |
1972年 | 49篇 |
1971年 | 47篇 |
1970年 | 30篇 |
1969年 | 33篇 |
排序方式: 共有4844条查询结果,搜索用时 31 毫秒
381.
J. Semkova R. Koleva N. Bankov St. Malchev V. M. Petrov V. A. Shurshakov I. V. Chernykh V. V. Benghin S. G. Drobyshev E. N. Yarmanova I. V. Nikolaev 《Cosmic Research》2013,51(2):124-132
For estimating radiation risk in space flights it is necessary to determine radiation dose obtained by critical organs of a human body. For this purpose the experiments with human body models are carried out onboard spacecraft. These models represent phantoms equipped with passive and active radiation detectors which measure dose distributions at places of location of critical organs. The dosimetric Liulin-5 telescope is manufactured with using three silicon detectors for studying radiation conditions in the spherical tissue-equivalent phantom on the Russian segment of the International space station (ISS). The purpose of the experiment with Liulin-5 instrument is to study dynamics of the dose rate and particle flux in the phantom, as well as variations of radiation conditions on the ISS over long time intervals depending on a phase of the solar activity cycle, orbital parameters, and presence of solar energetic particles. The Liulin-5 dosimeter measures simultaneously the dose rate and fluxes of charged particles at three depths in the radial channel of the phantom, as well as the linear energy transfer. The paper presents the results of measurements of dose rate and particle fluxes caused by various radiation field components on the ISS during the period from June 2007 till December 2009. 相似文献
382.
Zetzer J. I. Kozlov S. I. Rybakov V. A. Ponomarenko A. V. Smirnova N. V. Romanovsky Yu. A. Meng C.-I. Erlandson R. Stoyanov B. 《Cosmic Research》2002,40(3):233-240
The measurements of infrared emission from an artificial structure, which was generated during the Fluxus experiment with plasma jet injection into the atmosphere, are obtained and discussed for the first time. Additional experimental data on the airglow in the visible spectral band of the disturbed region of the atmosphere are presented. A generalized analysis of the data is given. 相似文献
383.
Flight demonstration of new thruster and green propellant technology on the PRISMA satellite 总被引:2,自引:0,他引:2
The concept of a storable liquid monopropellant blend for space applications based on ammonium dinitramide (ADN) was invented in 1997, within a co-operation between the Swedish Space Corporation (SSC) and the Swedish Defense Research Agency (FOI). The objective was to develop a propellant which has higher performance and is safer than hydrazine. The work has been performed under contract from the Swedish National Space Board and ESA. The progress of the development has been presented in several papers since 2000.ECAPS, a subsidiary of the Swedish Space Corporation was established in 2000 with the aim to develop and market the novel “high performance green propellant” (HPGP) technology for space applications. The new technology is based on several innovations and patents w.r.t. propellant formulation and thruster design, including a high temperature resistant catalyst and thrust chamber.The first flight demonstration of the HPGP propulsion system will be performed on PRISMA. PRISMA is an international technology demonstration program with Swedish Space Corporation as the Prime Contractor.This paper describes the performance, characteristics, design and verification of the HPGP propulsion system for PRISMA. Compatibility issues related to using a new propellant with COTS components is also discussed. The PRISMA mission includes two satellites in LEO orbit were the focus is on rendezvous and formation flying. One of the satellites will act as a “target” and the main spacecraft performs rendezvous and formation flying maneuvers, where the ECAPS HPGP propulsion system will provide delta-V capability.The PRISMA CDR was held in January 2007. Integration of the flight propulsion system is about to be finalized.The flight opportunity on PRISMA represents a unique opportunity to demonstrate the HPGP propulsion system in space, and thus take a significant step towards its use in future space applications. The launch of PRISMA scheduled to 2009. 相似文献
384.
F. R. Cleminson 《Space Policy》1988,4(2)
Verification of arms control treaties is essential to provide adequate international confidence in treaty compliance. This Viewpoint underlines the responsibility of non-superpower countries to become more closely involved in space surveillance of treaties to which they are parties. In Canada, Paxsat research has focused on two potential applications of space-based remote sensing to multi-lateral arms control verification. The necessary technology is readily available in non-superpower countries for the Paxsat concept to be put into operation. 相似文献
385.
386.
F. Bagenal A. Adriani F. Allegrini S. J. Bolton B. Bonfond E. J. Bunce J. E. P. Connerney S. W. H. Cowley R. W. Ebert G. R. Gladstone C. J. Hansen W. S. Kurth S. M. Levin B. H. Mauk D. J. McComas C. P. Paranicas D. Santos-Costa R. M. Thorne P. Valek J. H. Waite P. Zarka 《Space Science Reviews》2017,213(1-4):219-287
In July 2016, NASA’s Juno mission becomes the first spacecraft to enter polar orbit of Jupiter and venture deep into unexplored polar territories of the magnetosphere. Focusing on these polar regions, we review current understanding of the structure and dynamics of the magnetosphere and summarize the outstanding issues. The Juno mission profile involves (a) a several-week approach from the dawn side of Jupiter’s magnetosphere, with an orbit-insertion maneuver on July 6, 2016; (b) a 107-day capture orbit, also on the dawn flank; and (c) a series of thirty 11-day science orbits with the spacecraft flying over Jupiter’s poles and ducking under the radiation belts. We show how Juno’s view of the magnetosphere evolves over the year of science orbits. The Juno spacecraft carries a range of instruments that take particles and fields measurements, remote sensing observations of auroral emissions at UV, visible, IR and radio wavelengths, and detect microwave emission from Jupiter’s radiation belts. We summarize how these Juno measurements address issues of auroral processes, microphysical plasma physics, ionosphere-magnetosphere and satellite-magnetosphere coupling, sources and sinks of plasma, the radiation belts, and the dynamics of the outer magnetosphere. To reach Jupiter, the Juno spacecraft passed close to the Earth on October 9, 2013, gaining the necessary energy to get to Jupiter. The Earth flyby provided an opportunity to test Juno’s instrumentation as well as take scientific data in the terrestrial magnetosphere, in conjunction with ground-based and Earth-orbiting assets. 相似文献
387.
H. M. Cuppen C. Walsh T. Lamberts D. Semenov R. T. Garrod E. M. Penteado S. Ioppolo 《Space Science Reviews》2017,212(1-2):1-58
The cross-disciplinary field of astrochemistry exists to understand the formation, destruction, and survival of molecules in astrophysical environments. Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. A broad consensus has been reached in the astrochemistry community on how to suitably treat gas-phase processes in models, and also on how to present the necessary reaction data in databases; however, no such consensus has yet been reached for grain-surface processes. A team of \({\sim}25\) experts covering observational, laboratory and theoretical (astro)chemistry met in summer of 2014 at the Lorentz Center in Leiden with the aim to provide solutions for this problem and to review the current state-of-the-art of grain surface models, both in terms of technical implementation into models as well as the most up-to-date information available from experiments and chemical computations. This review builds on the results of this workshop and gives an outlook for future directions. 相似文献
388.
S. B. Mende H. U. Frey K. Rider C. Chou S. E. Harris O. H. W. Siegmund S. L. England C. Wilkins W. Craig T. J. Immel P. Turin N. Darling J. Loicq P. Blain E. Syrstad B. Thompson R. Burt J. Champagne P. Sevilla S. Ellis 《Space Science Reviews》2017,212(1-2):655-696
ICON Far UltraViolet (FUV) imager contributes to the ICON science objectives by providing remote sensing measurements of the daytime and nighttime atmosphere/ionosphere. During sunlit atmospheric conditions, ICON FUV images the limb altitude profile in the shortwave (SW) band at 135.6 nm and the longwave (LW) band at 157 nm perpendicular to the satellite motion to retrieve the atmospheric O/N2 ratio. In conditions of atmospheric darkness, ICON FUV measures the 135.6 nm recombination emission of \(\mathrm{O}^{+}\) ions used to compute the nighttime ionospheric altitude distribution. ICON Far UltraViolet (FUV) imager is a Czerny–Turner design Spectrographic Imager with two exit slits and corresponding back imager cameras that produce two independent images in separate wavelength bands on two detectors. All observations will be processed as limb altitude profiles. In addition, the ionospheric 135.6 nm data will be processed as longitude and latitude spatial maps to obtain images of ion distributions around regions of equatorial spread F. The ICON FUV optic axis is pointed 20 degrees below local horizontal and has a steering mirror that allows the field of view to be steered up to 30 degrees forward and aft, to keep the local magnetic meridian in the field of view. The detectors are micro channel plate (MCP) intensified FUV tubes with the phosphor fiber-optically coupled to Charge Coupled Devices (CCDs). The dual stack MCP-s amplify the photoelectron signals to overcome the CCD noise and the rapidly scanned frames are co-added to digitally create 12-second integrated images. Digital on-board signal processing is used to compensate for geometric distortion and satellite motion and to achieve data compression. The instrument was originally aligned in visible light by using a special grating and visible cameras. Final alignment, functional and environmental testing and calibration were performed in a large vacuum chamber with a UV source. The test and calibration program showed that ICON FUV meets its design requirements and is ready to be launched on the ICON spacecraft. 相似文献
389.
Reconfiguration of multiprocessor systems makes it possible to improve their failure-resistance that is especially important for the integrated modular avionics systems. The algorithm considered in this paper allows minimizing the reservation and providing the better safety level and more effective flight completion or even its further execution in the case of failures of airborne equipment. 相似文献
390.
R. Manuel S.E.S. FerreiraM.S. Potgieter R.D. StraussN.E. Engelbrecht 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Time-dependent cosmic ray modulation is calculated over multiple solar cycles using our well established two-dimensional time-dependent modulation model. Results are compared to Voyager 1, Ulysses and IMP cosmic ray observations to establish compatibility. A time-dependence in the diffusion and drift coefficients, implicitly contained in recent expressions derived by , , and , is incorporated into the cosmic ray modulation model. This results in calculations which are compatible with spacecraft observations on a global scale over consecutive solar cycles. This approach compares well to the successful compound approach of Ferreira and Potgieter (2004). For both these approaches the magnetic field magnitude, variance of the field and current sheet tilt angle values observed at Earth are transported time-dependently into the outer heliosphere. However, when results are compared to observations for extreme solar maximum, the computed step-like modulation is not as pronounced as observed. This indicates that some additional merging of these structures into more pronounced modulation barriers along the way is needed. 相似文献