全文获取类型
收费全文 | 154篇 |
免费 | 15篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 18篇 |
地球物理 | 44篇 |
地质学 | 48篇 |
海洋学 | 30篇 |
天文学 | 22篇 |
综合类 | 2篇 |
自然地理 | 7篇 |
出版年
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 8篇 |
2018年 | 10篇 |
2017年 | 8篇 |
2016年 | 12篇 |
2015年 | 11篇 |
2014年 | 6篇 |
2013年 | 12篇 |
2012年 | 10篇 |
2011年 | 8篇 |
2010年 | 11篇 |
2009年 | 14篇 |
2008年 | 13篇 |
2007年 | 7篇 |
2006年 | 2篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1998年 | 1篇 |
1996年 | 2篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有172条查询结果,搜索用时 15 毫秒
171.
Valentina G. Tsimbalist Gennady N. Anoshin Valentin N. Mitkin Ljudmila I. Razvorotneva Nadezhda P. Golovanova 《Geostandards and Geoanalytical Research》2000,24(2):171-182
Some recent experiments on the determination of Au and the platinum-group elements (PGE) in geochemical samples are reviewed. Emphasis is given to the determination of ultra-low levels of PGE concentrations in resistant matrices, including chromites, molybdenites and ultrabasic ores. The problems and features of PGE determination in samples of various chemical composition are considered. For each sample type studied, a series of sample preparation techniques are proposed. These techniques included acid digestion, fusion with sodium peroxide, cold sintering with an oxidizing mixture of Na2 O2 + Na2 CO3 and also oxidizing fluorination with bromine trifluoride. A new approach for preparing geochemical material prior to digestion, based on mechano-chemical activation with simultaneous hyperfine grinding, is proposed and studied. The instrumental determination of PGE contents was carried out directly by AAS from extracted organic phases. It was found that a combination of digestion processes was required to achieve geochemical background levels of Au and PGE concentrations with the following detection limits: Pd, Rh - 1 ng g−1 , Pt, Ru - 10 ng g−1 , Au - 0.2 ng g−1 , Ag - 0.1 ng g−1. The uncertainty in PGE and Au determination in geochemical samples is dependent on metal concentration, and also on their distribution in samples. The total analytical uncertainty of the proposed method is between 15-30%. 相似文献
172.
We consider 16 earthquakes with Mw?=?4.2–5.2 that occurred in the south-eastern part of the Laptev Sea shelf, Lena River Delta, and North Verkhoyanye (Russia) in 1990–2014. Focal mechanisms, scalar seismic moments, moment magnitudes, and hypocentral depths of the seismic events have been calculated from the data on amplitude spectra of surface waves and P wave first-motion polarities. The obtained results sufficiently implement the existing dataset on reliable earthquake source parameters for the study region and prove the change of the stress-strain state of the crust from extension on the Laptev Sea shelf to compression on the continent providing finer spatial details of the deformation field in the transition zones such as Buor-Khaya Bay and the Lena River Delta. 相似文献