全文获取类型
| 收费全文 | 962篇 |
| 免费 | 89篇 |
| 国内免费 | 119篇 |
专业分类
| 测绘学 | 111篇 |
| 大气科学 | 124篇 |
| 地球物理 | 90篇 |
| 地质学 | 146篇 |
| 海洋学 | 49篇 |
| 天文学 | 564篇 |
| 综合类 | 31篇 |
| 自然地理 | 55篇 |
出版年
| 2024年 | 11篇 |
| 2023年 | 24篇 |
| 2022年 | 28篇 |
| 2021年 | 33篇 |
| 2020年 | 26篇 |
| 2019年 | 24篇 |
| 2018年 | 24篇 |
| 2017年 | 32篇 |
| 2016年 | 29篇 |
| 2015年 | 39篇 |
| 2014年 | 38篇 |
| 2013年 | 29篇 |
| 2012年 | 40篇 |
| 2011年 | 28篇 |
| 2010年 | 31篇 |
| 2009年 | 57篇 |
| 2008年 | 67篇 |
| 2007年 | 64篇 |
| 2006年 | 71篇 |
| 2005年 | 63篇 |
| 2004年 | 47篇 |
| 2003年 | 64篇 |
| 2002年 | 58篇 |
| 2001年 | 31篇 |
| 2000年 | 39篇 |
| 1999年 | 33篇 |
| 1998年 | 27篇 |
| 1997年 | 16篇 |
| 1996年 | 20篇 |
| 1995年 | 22篇 |
| 1994年 | 12篇 |
| 1993年 | 8篇 |
| 1992年 | 5篇 |
| 1991年 | 12篇 |
| 1990年 | 2篇 |
| 1989年 | 6篇 |
| 1988年 | 4篇 |
| 1987年 | 4篇 |
| 1986年 | 1篇 |
| 1980年 | 1篇 |
排序方式： 共有1170条查询结果，搜索用时 390 毫秒
91.
利用星团谱样本的星族合成方法,研究了邻近巨椭圆星系NGC5018中的星族成分和其内部的恒星形成历史,给出了星系中不同年龄和金属丰度星族的成分占有比.星族合成结果表明,NGC5018中不仅存在大量金属丰度低的年老恒星成分,而且较年轻的星族成分(T=5×108yr)对星系光度贡献也很重要.星系吞并和相互作用过程可能是触发这些较年轻星族形成的物理原因,椭圆星系内部的恒星形成历史可能是2次爆发或者多次爆发过程.这些结果可以很好地解释NGC5018颜色偏蓝、Mg2谱指数强度偏弱等观测特征. 相似文献
92.
93.
A number of high resolution and high signal-to-noise ratio spectra of mildly metal-poor stars were obtained with the coudé echelle spectrograph attached to the 2.16m telescope at Xinglong Observation Base of Beijing Astronomical Observatory. The spectra of seven mildly metal-poor stars were processed with the MIDAS software package, and the equivalent widths of their spectral lines were measured. The measured equivalent widths together with an error analysis are presented. 相似文献
94.
ICE, the electric field experiment on DEMETER 总被引：9，自引：0，他引：9
95.
96.
97.
98.
具有硅酸盐尘埃特征碳星的新的候选者 总被引：1，自引：1，他引：0
本文根据红外天文卫星的宽波段测光及低分辨率光谱资料，给出了两颗新的可能具有硅酸尘埃特征的碳星及４颗可能的候选者。 相似文献
99.
To accomplish its mission, the spaceborne observatory SNAP (SuperNova Acceleration Probe) requires a pointing stability of
<0.03 arcseconds during exposures lasting up to 500 sec. A Monte Carlo simulation of the photoelectron statistics from the
guiding star investigates geometrical (such as the pixel size of the detector or the plate scale) and physical parameters
(such as the magnitude of the star). It is shown that simple centroiding calculations can lead to the desired accuracy with
guide stars as faint as magnitude 16. Availability of these stars is verified thanks to the HST Guide Star Catalog complemented
with a statistical model of the distribution of stars. Thus a through-the-lens sensor that uses stars as faint as magnitude
16 to provide the necessary guiding signals is feasible.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
100.
Guillermo Bosch † Elena Terlevich ‡ Roberto Terlevich § 《Monthly notices of the Royal Astronomical Society》2002,329(3):481-496
We have obtained accurate CCD narrow-band Hβ and Hα photometry of giant H ii regions (GEHRs) in M33, NGC 6822 and M101. Comparison with previous determinations of emission-line fluxes shows large discrepancies; their probable origins are discussed. Combining our new photometric data with global velocity dispersion ( σ ) derived from emission linewidths, we review the relation. A re-analysis of the properties of the GEHRs included in our sample shows that age spread and the superposition of components in multiple regions introduce a considerable spread in the regression. Combining the information available in the literature regarding ages of the associated clusters, evolutionary footprints on the interstellar medium, and kinematical properties of the knots that build up the multiple GEHRs, we find that a subsample – which we refer to as young and single GEHRs – do follow a tight relation in the plane. 相似文献