全文获取类型
收费全文 | 751篇 |
免费 | 16篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 47篇 |
地球物理 | 85篇 |
地质学 | 246篇 |
海洋学 | 54篇 |
天文学 | 276篇 |
综合类 | 1篇 |
自然地理 | 49篇 |
出版年
2020年 | 4篇 |
2019年 | 9篇 |
2018年 | 8篇 |
2017年 | 13篇 |
2016年 | 10篇 |
2015年 | 18篇 |
2014年 | 19篇 |
2013年 | 24篇 |
2012年 | 17篇 |
2011年 | 12篇 |
2010年 | 15篇 |
2009年 | 32篇 |
2008年 | 32篇 |
2007年 | 36篇 |
2006年 | 34篇 |
2005年 | 20篇 |
2004年 | 40篇 |
2003年 | 23篇 |
2002年 | 21篇 |
2001年 | 20篇 |
2000年 | 21篇 |
1999年 | 12篇 |
1998年 | 10篇 |
1997年 | 10篇 |
1996年 | 7篇 |
1995年 | 11篇 |
1994年 | 13篇 |
1993年 | 11篇 |
1992年 | 6篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 10篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1985年 | 24篇 |
1984年 | 15篇 |
1983年 | 17篇 |
1982年 | 15篇 |
1981年 | 13篇 |
1980年 | 10篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 11篇 |
1976年 | 7篇 |
1975年 | 19篇 |
1974年 | 11篇 |
1973年 | 6篇 |
1972年 | 4篇 |
1971年 | 10篇 |
排序方式: 共有769条查询结果,搜索用时 15 毫秒
91.
Stephen R. Kane T. A. Lister rew Collier Cameron Keith Horne David James Don L. Pollacco Rachel A. Street Yiannis Tsapras 《Monthly notices of the Royal Astronomical Society》2005,362(1):117-126
Recent wide field photometric surveys, which target a specific field for long durations, are ideal for studying both long- and short-period stellar variability. Here, we report on 75 variable stars detected during the observations of a field in Pegasus using the Wide Angle Search for Planets Prototype (WASP0) instrument, 73 of which are new discoveries. The variables detected include 16 δ Scuti stars, 34 eclipsing binaries, 3 BY Draconis stars and 4 RR Lyraes. We estimate that the fraction of stars in the field brighter than V ∼ 13.5 exhibiting variable behaviour with an amplitude greater than 0.6 per cent rms is ∼0.4 per cent. These results are compared with other wide field stellar variability surveys, and implications for detecting transits due to extra-solar planets are discussed. 相似文献
92.
T. D. Thoroughgood V. S. Dhillon D. Steeghs C. A. Watson D. A. H. Buckley S. P. Littlefair D. A. Smith M. Still † K. J. van der Heyden B. Warner 《Monthly notices of the Royal Astronomical Society》2005,357(3):881-894
We present time-resolved spectroscopy and photometry of the double-lined eclipsing cataclysmic variable V347 Pup (=LB 1800). There is evidence of irradiation on the inner hemisphere of the secondary star, which we correct for using a model to give a secondary-star radial velocity of K R = 198 ± 5 km s−1 . The rotational velocity of the secondary star in V347 Pup is found to be v sin i = 131 ± 5 km s−1 and the system inclination is i = 840 ± 23 . From these parameters we obtain masses of M 1 = 0.63 ± 0.04 M⊙ for the white dwarf primary and M 2 = 0.52 ± 0.06 M⊙ for the M0.5V secondary star, giving a mass ratio of q = 0.83 ± 0.05 . On the basis of the component masses, and the spectral type and radius of the secondary star in V347 Pup, we find tentative evidence for an evolved companion. V347 Pup shows many of the characteristics of the SW Sex stars, exhibiting single-peaked emission lines, high-velocity S-wave components and phase-offsets in the radial velocity curve. We find spiral arms in the accretion disc of V347 Pup and measure the disc radius to be close to the maximum allowed in a pressureless disc. 相似文献
93.
94.
Ricardo Génova-Santos José Alberto Rubiño-Martín Rafael Rebolo † Kieran Cleary ‡ Rod D. Davies Richard J. Davis Clive Dickinson § Nelson Falcón ‡‡ Keith Grainge Carlos M. Gutiérrez Michael P. Hobson Michael E. Jones ¶ Rüdiger Kneissl Katy Lancaster Carmen P. Padilla-Torres Richard D. E. Saunders Paul F. Scott Angela C. Taylor ¶ Robert A. Watson †† 《Monthly notices of the Royal Astronomical Society》2005,363(1):79-92
95.
J. R. Barnes Travis S. Barman L. Prato D. Segransan H. R. A. Jones C. J. Leigh A. Collier Cameron D. J. Pinfield 《Monthly notices of the Royal Astronomical Society》2007,382(1):473-480
We obtained 238 spectra of the close-orbiting extrasolar giant planet HD 189733b with resolution R ∼ 15 000 during one night of observations with the Near-Infrared High-Resolution Spectrograph (NIRSPEC), at the Keck II Telescope. We have searched for planetary absorption signatures in the 2.0–2.4 μm region where H2 O and CO are expected to be the dominant atmospheric opacities. We employ a phase-dependent orbital model and tomographic techniques to search for the planetary absorption signatures in the combined stellar and planetary spectra. Because potential absorption signatures are hidden in the noise of each single exposure, we use a model list of lines to apply a spectral deconvolution. The resulting mean profile possesses a signal-to-noise ratio (S/N) that is 20 times greater than that found in individual lines. Our spectral time series thus yields spectral signatures with a mean S/N = 2720. We are unable to detect a planetary signature at a contrast ratio of log10 ( F p / F * ) =−3.40 , with 63.8 per cent confidence. Our findings are not consistent with model predictions which nevertheless give a good fit to mid-infrared observations of HD 189733b. The 1σ result is a factor of 1.7 times less than the predicted 2.185-μm planet/star flux ratio of log10 ( F p / F * ) ∼−3.16 . 相似文献
96.
97.
98.
99.
100.