全文获取类型
收费全文 | 1784篇 |
免费 | 187篇 |
国内免费 | 251篇 |
专业分类
测绘学 | 168篇 |
大气科学 | 159篇 |
地球物理 | 297篇 |
地质学 | 460篇 |
海洋学 | 99篇 |
天文学 | 925篇 |
综合类 | 62篇 |
自然地理 | 52篇 |
出版年
2024年 | 6篇 |
2023年 | 13篇 |
2022年 | 35篇 |
2021年 | 50篇 |
2020年 | 41篇 |
2019年 | 40篇 |
2018年 | 25篇 |
2017年 | 46篇 |
2016年 | 63篇 |
2015年 | 55篇 |
2014年 | 58篇 |
2013年 | 51篇 |
2012年 | 59篇 |
2011年 | 71篇 |
2010年 | 65篇 |
2009年 | 122篇 |
2008年 | 103篇 |
2007年 | 99篇 |
2006年 | 123篇 |
2005年 | 119篇 |
2004年 | 122篇 |
2003年 | 125篇 |
2002年 | 107篇 |
2001年 | 113篇 |
2000年 | 100篇 |
1999年 | 106篇 |
1998年 | 95篇 |
1997年 | 40篇 |
1996年 | 22篇 |
1995年 | 26篇 |
1994年 | 35篇 |
1993年 | 10篇 |
1992年 | 13篇 |
1991年 | 12篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 12篇 |
1987年 | 3篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1971年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有2222条查询结果,搜索用时 490 毫秒
941.
J.-K. Lee † A.J. Walsh‡ M.G. Burton M.C.B. Ashley 《Monthly notices of the Royal Astronomical Society》2001,324(4):1102-1108
We report the discovery of H2 line emission associated with 6.67-GHz methanol maser emission in massive star-forming regions. In our UNSWIRF/AAT observations, H2 1–0 S(1) line emission was found associated with an ultracompact H ii region IRAS 14567–5846 and isolated methanol maser sites in G318.95–0.20 , IRAS 15278–5620 and IRAS 16076–5134 . Owing to the lack of radio continuum in the latter three sources, we argue that their H2 emission is shock excited, while it is UV-fluorescently excited in IRAS 14567–5846 . Within the positional uncertainties of 3 arcsec, the maser sites correspond to the location of infrared sources. We suggest that 6.67-GHz methanol maser emission is associated with hot molecular cores, and propose an evolutionary sequence of events for the process of massive star formation. 相似文献
942.
Bojan Nikolic Paul Alexander Garret Cotter Malcolm Longair Marcel Clemens 《Astrophysics and Space Science》2003,284(2):573-576
We present preliminary results of recent spatially resolved mid infrared (Mid-IR) spectroscopy with the MICHELLE instrument
on UKIRT of NGC 7469, observed as part of a larger programme to study a sample of starburst and AGN in the Mid-IR.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
943.
944.
945.
Spectral and morphological studies of an infrared nebula in the neighborhood of Cyg OB7 discovered in 2007 are reported. It
is shown that over the last several years the brightness and shape of the nebula have changed significantly. Spectral observations
of the nebula made with the 2.6-m telescope at the Byurakan Observatory in 2004 and 2005 reveal the existence of a faint trace
of continuum spectrum, indicating the existence of a star inside the dark cloud. Classification of these spectra shows that
over one year the star’s spectral class changed from late G to early K. It is also shown that the absorption in the direction
of the nebula is as high as 8m–10m.
__________
Translated from Astrofizika, Vol. 50, No. 1, pp. 17–27 (February 2007). 相似文献
946.
Patrick F. Roche Christopher Packham David K. Aitken Rachel E. Mason 《Monthly notices of the Royal Astronomical Society》2007,375(1):99-104
Spectroscopy at 8–13 μm with T-ReCS on Gemini-S is presented for three galaxies with substantial silicate absorption features, NGC 3094, NGC 7172 and NGC 5506. In the galaxies with the deepest absorption bands, the silicate profile towards the nuclei is well represented by the emissivity function derived from the circumstellar emission from the red supergiant, μ Cephei which is also representative of the mid-infrared absorption in the diffuse interstellar medium in the Galaxy. There is spectral structure near 11.2 μm in NGC 3094 which may be due to a component of crystalline silicates. In NGC 5506, the depth of the silicate absorption increases from north to south across the nucleus, suggestive of a dusty structure on scales of tens of parsecs. We discuss the profile of the silicate absorption band towards galaxy nuclei and the relationship between the 9.7-μm silicate and 3.4-μm hydrocarbon absorption bands. 相似文献
947.
瑞雷面波勘探的过去、现在和未来 总被引:2,自引:0,他引:2
回顾了瑞雷面波勘探发展的历史,剖析了面波频散曲线正反演的进展及存在的问题,重点指出在石油和煤炭反射地震中,应从剔除面波转变为利用面波,并借助现有石油“大炮”反射地震资料中“有害的”瑞雷面波提取浅层地质结构信息,为反射地震静校正、近地表工程地质评价等提供物性参数,把反射地震的面波干扰变为对勘探十分有利的参数提取源,实现以强干扰面波为主要数据源的浅层结构探测,以促进瑞雷面波勘探技术的进一步发展。 相似文献
948.
949.
M. A. T. Groenewegen P. R. Wood G. C. Sloan J. A. D. L. Blommaert M.-R. L. Cioni M. W. Feast S. Hony † M. Matsuura J. W. Menzies E. A. Olivier E. Vanhollebeke J. Th. van Loon P. A. Whitelock A. A. Zijlstra H. J. Habing E. Lagadec 《Monthly notices of the Royal Astronomical Society》2007,376(1):313-337
950.
M. H. Jones † 《Monthly notices of the Royal Astronomical Society》2001,327(1):191-198
The infrared properties of barium stars are studied using published data in the K band and from IRAS . At 12 and 25 μm the emission from barium stars shows no excess over photospheric emission. Thus the claim made by Hakkila that some barium stars show evidence of the presence of warm (∼300 K ) circumstellar material is not supported. The 60-μm properties of barium stars are studied using survival analysis methods, and it is found that very few (3.7 ± 2.6 per cent) barium stars exhibit far-infrared excesses. Furthermore, it is found that the incidence of excess emission at 60 μm is lower in barium stars than for normal G and K giants. This may indicate that the mass-transfer event that is assumed to have taken place in barium stars has removed any cool circumstellar material that may have existed in these systems. Alternatively, it is suggested that the incidence of infrared excesses in normal G and K giants may have been over-estimated as a result of not fully accounting for foreground contamination by interstellar cirrus. 相似文献