全文获取类型
收费全文 | 607篇 |
免费 | 16篇 |
国内免费 | 17篇 |
专业分类
测绘学 | 54篇 |
大气科学 | 14篇 |
地球物理 | 38篇 |
地质学 | 67篇 |
海洋学 | 25篇 |
天文学 | 396篇 |
综合类 | 33篇 |
自然地理 | 13篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 8篇 |
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 7篇 |
2015年 | 11篇 |
2014年 | 16篇 |
2013年 | 13篇 |
2012年 | 17篇 |
2011年 | 19篇 |
2010年 | 15篇 |
2009年 | 60篇 |
2008年 | 28篇 |
2007年 | 70篇 |
2006年 | 58篇 |
2005年 | 61篇 |
2004年 | 47篇 |
2003年 | 35篇 |
2002年 | 32篇 |
2001年 | 18篇 |
2000年 | 23篇 |
1999年 | 13篇 |
1998年 | 29篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1987年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1919年 | 1篇 |
1900年 | 1篇 |
1897年 | 5篇 |
1882年 | 1篇 |
1880年 | 1篇 |
1877年 | 3篇 |
排序方式: 共有640条查询结果,搜索用时 0 毫秒
31.
32.
33.
34.
35.
36.
37.
T. Venturi S. Bardelli R. Morganti & R. W. Hunstead 《Monthly notices of the Royal Astronomical Society》1998,298(4):1113-1122
In this paper we present a detailed study of the radio galaxy J1324–3138, located at a projected distance of 2 arcmin from the centre of the Abell cluster of galaxies A3556, belonging to the core of the Shapley Concentration, at an average redshift of z = 0.05. We have observed J1324–3138 over a wide range of frequencies: at 327 MHz (VLA), 843 MHz (MOST), and at 1376, 2382, 4790 and 8640 MHz (ATCA). Our analysis suggests that J1324–3138 is a remnant of a tailed radio galaxy, in which the nuclear engine has switched off and the radio source is now at a late stage of its evolution, confined by the intracluster gas. The radio galaxy is not in pressure equilibrium with the external medium, as is often found for extended radio sources in clusters of galaxies. We favour the hypothesis that the lack of observed polarized radio emission in the source is a result of Faraday rotation by a foreground screen, i.e. the source is seen through a dense cluster gas, characterized by a random magnetic field. An implication of the head–tail nature of the source is that J1324–3138 is moving away from the core of A3556 and that, possibly, a major merging event between the core of A3556 and the subgroup hosting J1324–3138 has already taken place. 相似文献
38.
39.
Gavin Ramsay & Peter J. Wheatley 《Monthly notices of the Royal Astronomical Society》1998,301(1):95-100
We present low–medium resolution optical spectroscopy of the eclipsing AM Her system MN Hya (RX J0929–24). We determine the magnetic field strength at the primary accretion region of the white dwarf to be 42 MG from the spacing of cyclotron features visible during π ∼ 0.4–0.7. From spectra taken during the eclipse we find that the secondary has an M3–4 spectral type. Combined with the eclipse photometry of Sekiguchi, Nakada &38; Bassett and an estimate of the interstellar extinction we find a distance of ∼300–700 pc. We find unusual line variations at π ∼ 0.9: Hα is seen in absorption and emission. This is at the same point in the orbital phase at which a prominent absorption dip is seen in soft X-rays. 相似文献
40.
I. Zh. Stefanov 《Astronomische Nachrichten》2016,337(3):246-253
The observation of a pair of simultaneous twin kHz QPOs in the power density spectrum of a neutron star or a black hole allows its mass‐angular‐momentum relation to be constrained. Situations in which the observed simultaneous pairs are more than one allow the different models of the kHz QPOs to be falsified. Discrepancy between the estimates coming from the different pairs would call the used model into question. In the current paper, the relativistic precession model is applied to the twin kHz QPOs that appear in the light curves of three groups of observations of the accreting millisecond X‐ray pulsar IGR J17511–3057. It was found that the predictions of one of the groups are practically in conflict with the other two. Another interesting result is that the region in which the kHz QPOs have been born is rather broad and extends quite far from the ISCO. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献