全文获取类型
收费全文 | 541篇 |
免费 | 1篇 |
国内免费 | 2篇 |
专业分类
航空 | 289篇 |
航天技术 | 81篇 |
综合类 | 3篇 |
航天 | 171篇 |
出版年
2021年 | 3篇 |
2019年 | 5篇 |
2018年 | 70篇 |
2017年 | 39篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 18篇 |
2012年 | 7篇 |
2011年 | 48篇 |
2010年 | 21篇 |
2009年 | 33篇 |
2008年 | 22篇 |
2007年 | 24篇 |
2006年 | 19篇 |
2005年 | 12篇 |
2004年 | 9篇 |
2003年 | 17篇 |
2002年 | 9篇 |
2001年 | 9篇 |
2000年 | 15篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 12篇 |
1985年 | 16篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1970年 | 2篇 |
1968年 | 6篇 |
1967年 | 7篇 |
1966年 | 3篇 |
1965年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有544条查询结果,搜索用时 15 毫秒
101.
Knowledge of the observable properties of orbital debris is necessary to validate debris models for both the low Earth orbit (LEO) and the geosynchronous Earth orbit (GEO). Current methods determine the size and mass of orbital debris based on knowledge or assumption of the material type of the piece. Improvement in the knowledge of material is the goal of the research described herein. The process of using spectral absorption features to determine the material type is explored. A review of the optical measurements of orbital debris as well as current research in the area is discussed. Reflectances of common spacecraft materials are compared. The need for, and advances made possible by obtaining real data are explored. The prospects of the venture are investigated. 相似文献
102.
Chiho Matsumoto John R. Moore Karen M. Leighly Dirk Grupe Beverley J. Wills 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,34(12):2566-2570
We present preliminary results from analyses of hard X-ray and optical observations of a soft X-ray selected sample. We created a small but complete sample with 20 of the softest and brightest objects with low Galactic absorption from the ROSAT bright soft X-ray selected radio-quiet AGN sample. This sample consists of 10 narrow-line Seyfert 1 galaxies and 10 broad-line Seyfert galaxies. We analyze ASCA data in the 0.6–10 keV band and optical spectra from ground-based telescopes. We investigate the photon indices in the hard X-ray band, soft excesses in the ASCA band, and optical emission line properties. The photon indices in the 2–10 keV band are nominal for both narrow-line Seyfert 1 galaxies and broad-line Seyfert 1 galaxies in each class compared with other heterogeneous samples. All of the narrow-line Seyfert 1 galaxies show soft excesses, but this component seems to be less significant for broad-line Seyfert 1 galaxies. There seems to be a trend of steeper X-ray spectra to be accompanied by narrower Hβ for narrow-line Seyfert 1 galaxies, but this is not extended to the larger velocity width regime of broad-line Seyfert 1 galaxies, and no clear trend is seen among them. 相似文献
103.
V. A. Ivanov D. V. Ivanov N. V. Ryabova Luong Viet Loc E. V. Katkov 《Russian Aeronautics (Iz VUZ)》2017,60(2):286-291
The paper presents the methods and algorithms for positioning the dynamic (moving) objects using the oblique-incidence ionospheric sounding by chirp signals. Full-scale experiments have been performed to determine a distance to an object and its location. 相似文献
104.
Starting from 1960s, a great number of missions and experiments have been performed for the study of the high-energy sky. This review gives a wide vision of the most important space missions and balloon experiments that have operated in the 10–600 keV band, a crucial window for the study of the most energetic and violent phenomena in the Universe. Thus it is important to take the stock of the achievements to better establish what we have still to do with future missions in order to progress in this field, to establish which are the technologies required to solve the still open issues and to extend our knowledge of the Universe. 相似文献
105.
David Mimoun Naomi Murdoch Philippe Lognonné Kenneth Hurst William T. Pike Jane Hurley Tanguy Nébut William B. Banerdt SEIS Team 《Space Science Reviews》2017,211(1-4):383-428
The SEIS (Seismic Experiment for Interior Structures) instrument on board the InSight mission to Mars is the critical instrument for determining the interior structure of Mars, the current level of tectonic activity and the meteorite flux. Meeting the performance requirements of the SEIS instrument is vital to successfully achieve these mission objectives. The InSight noise model is a key tool for the InSight mission and SEIS instrument requirement setup. It will also be used for future operation planning. This paper presents the analyses made to build a model of the Martian seismic noise as measured by the SEIS seismometer, around the seismic bandwidth of the instrument (from 0.01 Hz to 1 Hz). It includes the instrument self-noise, but also the environment parameters that impact the measurements. We present the general approach for the model determination, the environment assumptions, and we analyze the major and minor contributors to the noise model. 相似文献
106.
D. J. McComas E. R. Christian N. A. Schwadron N. Fox J. Westlake F. Allegrini D. N. Baker D. Biesecker M. Bzowski G. Clark C. M. S. Cohen I. Cohen M. A. Dayeh R. Decker G. A. de Nolfo M. I. Desai R. W. Ebert H. A. Elliott H. Fahr P. C. Frisch H. O. Funsten S. A. Fuselier A. Galli A. B. Galvin J. Giacalone M. Gkioulidou F. Guo M. Horanyi P. Isenberg P. Janzen L. M. Kistler K. Korreck M. A. Kubiak H. Kucharek B. A. Larsen R. A. Leske N. Lugaz J. Luhmann W. Matthaeus D. Mitchell E. Moebius K. Ogasawara D. B. Reisenfeld J. D. Richardson C. T. Russell J. M. Sokół H. E. Spence R. Skoug Z. Sternovsky P. Swaczyna J. R. Szalay M. Tokumaru M. E. Wiedenbeck P. Wurz G. P. Zank E. J. Zirnstein 《Space Science Reviews》2018,214(8):116
The Interstellar Mapping and Acceleration Probe (IMAP) is a revolutionary mission that simultaneously investigates two of the most important overarching issues in Heliophysics today: the acceleration of energetic particles and interaction of the solar wind with the local interstellar medium. While seemingly disparate, these are intimately coupled because particles accelerated in the inner heliosphere play critical roles in the outer heliospheric interaction. Selected by NASA in 2018, IMAP is planned to launch in 2024. The IMAP spacecraft is a simple sun-pointed spinner in orbit about the Sun-Earth L1 point. IMAP’s ten instruments provide a complete and synergistic set of observations to simultaneously dissect the particle injection and acceleration processes at 1 AU while remotely probing the global heliospheric interaction and its response to particle populations generated by these processes. In situ at 1 AU, IMAP provides detailed observations of solar wind electrons and ions; suprathermal, pickup, and energetic ions; and the interplanetary magnetic field. For the outer heliosphere interaction, IMAP provides advanced global observations of the remote plasma and energetic ions over a broad energy range via energetic neutral atom imaging, and precise observations of interstellar neutral atoms penetrating the heliosphere. Complementary observations of interstellar dust and the ultraviolet glow of interstellar neutrals further deepen the physical understanding from IMAP. IMAP also continuously broadcasts vital real-time space weather observations. Finally, IMAP engages the broader Heliophysics community through a variety of innovative opportunities. This paper summarizes the IMAP mission at the start of Phase A development. 相似文献
107.
108.
The equations of the mathematical model are solved in terms of special functions. The results for the design scheme of the aircraft forebody are obtained with a guaranteed accuracy by the stable method of functional normalization. 相似文献
109.