全文获取类型
收费全文 | 3812篇 |
免费 | 3篇 |
国内免费 | 9篇 |
专业分类
航空 | 1714篇 |
航天技术 | 1402篇 |
综合类 | 10篇 |
航天 | 698篇 |
出版年
2021年 | 28篇 |
2018年 | 56篇 |
2017年 | 51篇 |
2016年 | 47篇 |
2014年 | 65篇 |
2013年 | 104篇 |
2012年 | 88篇 |
2011年 | 153篇 |
2010年 | 108篇 |
2009年 | 150篇 |
2008年 | 197篇 |
2007年 | 111篇 |
2006年 | 79篇 |
2005年 | 112篇 |
2004年 | 127篇 |
2003年 | 123篇 |
2002年 | 81篇 |
2001年 | 117篇 |
2000年 | 61篇 |
1999年 | 86篇 |
1998年 | 107篇 |
1997年 | 77篇 |
1996年 | 70篇 |
1995年 | 109篇 |
1994年 | 125篇 |
1993年 | 64篇 |
1992年 | 76篇 |
1991年 | 32篇 |
1990年 | 42篇 |
1989年 | 68篇 |
1988年 | 30篇 |
1987年 | 26篇 |
1986年 | 38篇 |
1985年 | 125篇 |
1984年 | 111篇 |
1983年 | 91篇 |
1982年 | 77篇 |
1981年 | 155篇 |
1980年 | 31篇 |
1979年 | 34篇 |
1978年 | 37篇 |
1977年 | 34篇 |
1976年 | 29篇 |
1975年 | 34篇 |
1974年 | 29篇 |
1973年 | 31篇 |
1972年 | 41篇 |
1971年 | 22篇 |
1970年 | 22篇 |
1969年 | 21篇 |
排序方式: 共有3824条查询结果,搜索用时 953 毫秒
561.
The observation of the galactic anticenter region by the balloon borne gamma-ray telescope Natalya-I
A.F. Iyudin V.G. Kirillov-Ugryumov Yu.D. Kotov Yu.V. Smirnov L.V. Kurnosova M.I. Fradkin S.V. Damle B.V. Sreekantan G.S. Gokhale P.K. Kunte 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(4):53-56
This paper presents the results of measurements of gamma radiation with energies above 5 MeV, from the galactic anticenter region. The balloon-borne gamma ray telescope “Natalya-I”, was launched on 6 November, 1980 from the Tata Institute of Fundamental Research's Balloon Facility (Hyderabad, India) and reached ceiling altitude of 35 km. The results on the accelerator calibration of the telescope, using a “tagged” gamma ray beam are also presented. 相似文献
562.
The transmission of integrity information using a signal format compatible with the Global Positioning System (GPS) and relayed through a geostationary satellite repeater, which will be critical in achieving high integrity and availability of global navigation by satellite is discussed. The inclusion of navigation repeaters designed to fulfil this function, the next generation of INMARSAT spacecraft, INMARSAT-3 is examined. The global navigation satellite system (GNSS) integrity channel (GIC) will employ pseudorandom codes in the same family as, but distinct from, the codes reserved by GPS. The data format of the basic integrity channel is designed to convey user range error information for 24 to 40 satellites. A closed-loop timing compensation technique will be used at the uplinking Earth station, to make the signal's clock and carrier Doppler variations identical to those that would result from an onboard signal source. Therefore, the INMARSAT-3 satellites will increase the number of useful navigation satellites available to any user, and can also function as sources of precise timing. There is also a possibility that wide area differential corrections can be carried on the same signal 相似文献
563.
P. Cerroni G. Martelli 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(12):97-102
It is suggested that the UV radiation, and shock and plasma phenomena which accompanied the hypervelocity impacts of solid bodies (meteorites and comets) onto the surface of the young Earth may have contributed to the synthesis of prebiotic organic molecules in the primitive atmosphere in a larger amount than was thought previously. The mechanisms responsible for this synthesis are discussed using information obtained from recent experimental and theoretical work on macroscopic hypervelocity impacts. 相似文献
564.
S. Cazes J. Charra N. Coron B. Cougrand J.-F. Crifo J. Crovisier C. Emerich R. Gispert B. Gondet G. Guyot D. Harduin J.-M. Lamarre G. Levanti C. Maurel D. Parisot F. Rocard P. Salvetat A. Soufflot T. Encrenaz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(9):273-276
The IKS infrared spectro-photometer will fly on board the VEGA platforms. It is designed to characterize the size, temperature and emissivity of the Comet Halley nucleus, to identify the major gaseous components of the inner coma and to detect the emission of the cometary grains. This paper presents the “calibration” experiments required to reduce the raw data: (i) absolute wavelength calibration of the filter wheels; (ii) modeling of the internal signal, as a function of the temperature of the different sub-systems; (iii) absolute and spectral responsivities of each of the spectrometric and photometric channels, as a function of the wavelength and position of the source in the field of view. Finally, we shall indicate the expected S/N ratios. 相似文献
565.
566.
E. Costa M. Salvati G. Agnetta R. Di Raffaele G. Gerardi B. Sacco L. Scarsi E. Massaro B. Agrinier J.C. Christi J.L. Masnou A. Bui-Van J.P. Chabaud P. Frabel P. Mandrou J. Narbonne M. Niel G. Rouaix G. Vedrenne 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(4):113-116
We present a large area, balloon borne, NaI(Tl) detector for low-energy gamma rays with temporal signature : FIGARO.The main detector is a mosaic of 12 NaI(Tl) tiles 22.5 × 15 × 5 cm, for a total geometric area of 4050 cm2.In the energy band 140 keV - 6 MeV, the expected background counting rate at float altitude is in the range of two to three thousands counts per second.For pulsar analysis the expected 3δ sensitivity for 5 hours exposition time is 2.5 10?4 ph/cm2.s.MeV (150–500 keV) 1.5 10?4 ph/cm2.s.MeV (1–6 MeV). This performance, together with the large effective area and the relatively short duration of a balloon flight, make FIGARO particularly suitable for the identification of sources by means of temporal analysis.For objectives in the Northern sky, including the Crab pulsar, a transmediterranean flight is planned for the summer of 1982 ; a Southern mission is scheduled in Brazil for the fall of 1983 (Vela, PSR 1822-09). 相似文献
567.
V. Sch nfelder K. Bennett H. Bloemen H. de Boer M. Busetta W. Collmar A. Connors R. Diehl J. W. den Herder W. Hermsen L. Kuiper G. G. Lichti J. Lockwood J. Macri M. McConnell D. Morris R. Much J. Ryan G. Stacy H. Steinle A. Strong B. Swanenburg M. Varendorff C. de Vries C. Winkler 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1993,13(12):647-655
COMPTEL is the first imaging telescope to explore the MeV gamma-ray range (0.7 to 30 MeV). At present, it is performing a complete sky survey. In later phases of the mission selected celestial objects will be studied in more detail. The data from the first year of the mission have demonstrated that COMPTEL performs very well. First sky maps of the inner part of the Galaxy clearly identify the plane as a bright MeV-source (probably due to discrete sources as well as diffuse radiation). The Crab and Vela pulsar lightcurves have been measured with unprecedented accuracy. The quasars 3C273 and 3C279 have been seen for the first time at MeV energies. Both quasars show a break in their energy spectra in the COMPTEL energy range. The 1.8 MeV line from radioactive 26A1 has been detected from the central region of the Galaxy and a first sky map of the inner part of the Galaxy has been obtained in the light of this line. Upper limits to gamma-ray line emission at 847 keV and 1.238 MeV from SN 1991T have been derived. Upper limits to the interstellar gamma-ray emissivity have been determined at MeV-energies. Several cosmic gamma-ray bursts within the field-of-view have been located with an accuracy of about 1°. On 1991 June 9, 11 and 15, COMPTEL observed gamma-ray emission (continuum and line) from three solar flares. Also neutrons were detected from the June 9 and June 15 flares. 相似文献
568.
R. Buccheri K. Bennett M. Busetta A. Carrami ana W. Collmar A. Connors W. Hermsen L. Kuiper G. G. Lichti V. Sch nfelder J. G. Stacy A. W. Strong 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1993,13(12):727-730
Pulsar measurements performed by the experiment COMPTEL, aboard the Compton Gamma Ray Observatory, are described. The main results refer to the Crab and Vela pulsars whose pulse shape characteristics are given in some detail and light curves are compared with those above 50 MeV, as observed by the COS-B satellite. No other gamma-ray pulsars have been detected to date by COMPTEL, the upper limit on the pulsed signal from Geminga being compatible with indications by other experiments. 相似文献
569.
A. G. A. Brown 《Space Science Reviews》1993,66(1-4):81-84
We present a photometric investigation, using the VBLUW system, of the stellar content of Orion OB1. Physical parameters (logg, logT
eff) for the stars are derived with the aid of model atmospheres. From these, visual extinctions, absolute magnitudes and distance moduli are derived. The distance moduli are used to determine membership for the stars in each of the subgroups and distances to the subgroups are calculated. The ages of the subgroups are derived through isochrone fitting and the IMF is derived for each subgroup. The energy deposited into the ISM through stellar winds and supernovae is calculated and compared to observed large scale features in the ISM around Orion OB1. 相似文献
570.
Attitude and Oribit Estimation Using Stars and Landmarks 总被引:2,自引:0,他引:2
White R.L. Adams M.B. Geisler E.G. Grant F.D. 《IEEE transactions on aerospace and electronic systems》1975,(2):195-203
An extended Kalman filter is used to process line-of-sight measurements to stars and known landmarks providing a statistical indication of performance in estimating spacecraft attitude, orbital ephemeris, and the bias drift of a set of three strapdown gyros. The landmark measurements were assumed to have been taken from the imagery of an Earth-observing multispectral scanner. It is shown that filtering of these noisy measurements results in highly accurate estimates of the above parameters. Results are given showing the sensitivity of performance to various system parameters such as star tracker accuracy, errors in the knowledge of landmark position, and number of stars and landmarks processed. 相似文献