全文获取类型
收费全文 | 600篇 |
免费 | 3篇 |
专业分类
地球物理 | 1篇 |
天文学 | 602篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2021年 | 1篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 3篇 |
2012年 | 10篇 |
2011年 | 5篇 |
2010年 | 6篇 |
2009年 | 27篇 |
2008年 | 41篇 |
2007年 | 44篇 |
2006年 | 60篇 |
2005年 | 71篇 |
2004年 | 64篇 |
2003年 | 63篇 |
2002年 | 30篇 |
2001年 | 36篇 |
2000年 | 35篇 |
1999年 | 40篇 |
1998年 | 41篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有603条查询结果,搜索用时 0 毫秒
41.
42.
V. Firpo G. Bosch † N. Morrell †‡ 《Monthly notices of the Royal Astronomical Society》2005,356(4):1357-1361
We present results of a search for giant H ii regions in southern galaxies. Using high-resolution spectra, obtained with the Magellan Inamori Kyocera Echelle (MIKE) at the Las Campanas Magellan II telescope, we were able to resolve the emission-line profiles and determine the intrinsic velocity dispersion of the ionized gas. Out of four observed regions, selected from previous CCD narrow-band photometry, we detected three H ii regions showing supersonic velocity dispersion, characteristic of giant H ii regions, and their location in diagnostic diagrams suggests that a powerful starburst is the source of ionization energy. 相似文献
43.
Edward M. Cackett Keith Horne 《Monthly notices of the Royal Astronomical Society》2006,365(4):1180-1190
Emission-line regions in active galactic nuclei (AGNs) and other photoionized nebulae should become larger in size when the ionizing luminosity increases. This 'breathing' effect is observed for the Hβ emission in NGC 5548 by using Hβ and optical continuum light curves from the 13-yr (1989–2001) AGN Watch monitoring campaign. To model the breathing, we use two methods to fit the observed light curves in detail: (i) parametrized models and, (ii) the memecho reverberation-mapping code. Our models assume that optical continuum variations track the ionizing radiation, and that the Hβ variations respond with time-delays τ due to light travel-time. By fitting the data using a delay-map Ψ(τ, F c ) that is allowed to change with continuum flux F c , we find that the strength of the Hβ response decreases and the time-delay increases with ionizing luminosity. The parametrized breathing models allow the time-delay and the Hβ flux to depend on the continuum flux so that, τ∝ F β c and F Hβ ∝ F α c . Our fits give 0.1 < β < 0.46 and 0.57 < α < 0.66. α is consistent with previous work by Gilbert and Peterson, and Goad, Korista and Knigge. Although we find β to be flatter than previously determined by Peterson et al. using cross-correlation methods, it is closer to the predicted values from recent theoretical work by Korista and Goad. 相似文献
44.
45.
Frédéric Zagury 《Journal of Astrophysics and Astronomy》2005,26(4):377-394
This paper examines the variations, because of atmospheric extinction, of broad-band visible spectra, obtained from long-slit
spectroscopy, in the vicinity of some stars, nebulae, and one faint galaxy. 相似文献
46.
Paul D. Allen Simon P. Driver Alister W. Graham Ewan Cameron Jochen Liske Roberto De Propris 《Monthly notices of the Royal Astronomical Society》2006,371(1):2-18
We present near-infrared (NIR) adaptive optics-assisted spectroscopic observations of the CO (Δμ= 2) absorption bands towards the centre of the giant elliptical galaxy NGC 1399. The observations were made with NAOS-CONICA (on the European Southern Observatory's Very Large Telescope) and have a full width at half-maximum resolution of 0.15 arcsec (14 pc). Kinematic analysis of the observations reveals a decoupled core and strongly non-Gaussian line-of-sight velocity profiles in the central 0.2 arcsec (19 pc). NIR imaging also indicates an asymmetric elongation of the central isophotes in the same region.
We use spherical orbit-superposition models to interpret the kinematics, using a set of orthogonal 'eigen-velocity profiles' that allow us to fit models directly to spectra. The models require a central black hole of mass 1.2+0.5 −0.6 × 109 M⊙ , with a strongly tangentially biased orbit distribution in the inner 40 pc. 相似文献
We use spherical orbit-superposition models to interpret the kinematics, using a set of orthogonal 'eigen-velocity profiles' that allow us to fit models directly to spectra. The models require a central black hole of mass 1.2
47.
48.
49.
50.
B. S. Shylaja 《Journal of Astrophysics and Astronomy》1988,9(3):161-172
Two Wolf-Rayet members of the cluster NGC 6231 are studied spectrophotometrically. HD 151932, a suspected variable, shows
variations in the emission line flux as well as continuum magnitude measurements. An attempt is made to understand this variation
as due to the asymmetric atmospheric structure. The other, HD 152270, a (WC7 + O) binary, shows variation of emission line
flux for C III and C IV lines only. This variation is studied as a possible phenomenon of atmospheric eclipses. 相似文献