全文获取类型
收费全文 | 124篇 |
免费 | 0篇 |
专业分类
系统科学 | 3篇 |
教育与普及 | 5篇 |
现状及发展 | 11篇 |
研究方法 | 6篇 |
综合类 | 98篇 |
自然研究 | 1篇 |
出版年
2012年 | 3篇 |
2011年 | 6篇 |
2010年 | 1篇 |
2009年 | 2篇 |
2008年 | 14篇 |
2007年 | 10篇 |
2006年 | 6篇 |
2005年 | 11篇 |
2004年 | 11篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 2篇 |
1994年 | 2篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1986年 | 5篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1966年 | 3篇 |
1965年 | 1篇 |
排序方式: 共有124条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
45.
46.
Berger E Ball S Becker KM Clarke M Frail DA Fukuda TA Hoffman IM Mellon R Momjian E Murphy NW Teng SH Woodruff T Zauderer BA Zavala RT 《Nature》2001,410(6826):338-340
Brown dwarfs are not massive enough to sustain thermonuclear fusion of hydrogen at their centres, but are distinguished from gas-giant planets by their ability to burn deuterium. Brown dwarfs older than approximately 10 Myr are expected to possess short-lived magnetic fields and to emit radio and X-rays only very weakly from their coronae. An X-ray flare was recently detected on the brown dwarf LP944-20, whereas previous searches for optical activity (and one X-ray search) yielded negative results. Here we report the discovery of quiescent and flaring radio emission from LP944-20, with luminosities several orders of magnitude larger than predicted by the empirical relation between the X-ray and radio luminosities that has been found for many types of stars. Interpreting the radio data within the context of synchrotron emission, we show that LP944-20 has an unusually weak magnetic field in comparison to active M-dwarf stars, which might explain the previous null optical and X-ray results, as well as the strength of the radio emissions compared to those at X-ray wavelengths. 相似文献
47.
48.
49.
50.