全文获取类型
收费全文 | 274篇 |
免费 | 32篇 |
国内免费 | 108篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 11篇 |
地球物理 | 53篇 |
地质学 | 297篇 |
海洋学 | 2篇 |
天文学 | 45篇 |
自然地理 | 4篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 10篇 |
2021年 | 19篇 |
2020年 | 9篇 |
2019年 | 20篇 |
2018年 | 21篇 |
2017年 | 19篇 |
2016年 | 15篇 |
2015年 | 20篇 |
2014年 | 28篇 |
2013年 | 48篇 |
2012年 | 79篇 |
2011年 | 8篇 |
2010年 | 9篇 |
2009年 | 9篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2006年 | 1篇 |
2005年 | 2篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 2篇 |
2001年 | 8篇 |
2000年 | 40篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1991年 | 8篇 |
1988年 | 1篇 |
1983年 | 1篇 |
1875年 | 2篇 |
1872年 | 1篇 |
排序方式: 共有414条查询结果,搜索用时 296 毫秒
101.
Le Zhang Jia‐Lin Wu Jia‐Run Tu Dan Wu Nan Li Xiao‐Ping Xia Zhong‐Yuan Ren 《Geostandards and Geoanalytical Research》2020,44(1):133-145
Matrix‐matched reference materials are necessary for accurate microbeam U‐Pb dating and Hf isotopic determination. This study introduces the RMJG rutile as a new potential reference material, which was separated from Palaeoproterozoic pelitic granulites collected in Hebei Province, China. LA‐ICP‐MS measurements indicate the RMJG rutile has extremely low Th (< 0.003 ± 0.01 µg g?1) and common Pb contents, but high Hf (102 ± 34 µg g?1), U (61 ± 11 µg g?1), and radiogenic Pb (~ 20 µg g?1) contents. Moreover, the rutile yields relatively constant U‐Pb ages and Hf isotopic data. The LA‐ICP‐MS analyses suggest that this rutile has a concordant U‐Pb age with a statistical mean 206Pb/238U and 207Pb/235U ages of 1749.9 ± 32.1 Ma and 1750.0 ± 26.4 Ma, respectively (2s), which are statistically indistinguishable from its ID‐TIMS ages (1750.6 ± 8.4 and 1750.1 ± 4.7 Ma). Precise determination of the 176Hf/177Hf ratio by MC‐ICP‐MS in solution mode (0.281652 ± 0.000006) is in good agreement with the statistical mean of the LA‐MC‐ICP‐MS measurements (0.28166 ± 0.00018). Therefore, the limited variations of RMJG U‐Pb age and Hf isotopic composition together with its extremely low common Pb and high Hf, U and Pb contents make it an ideal calibration and monitor reference material for LA‐ICP‐MS measurements. 相似文献
102.
103.
J.J. Peucat P. Ruffault E. Fritsch M. Bouhnik-Le Coz C. Simonet B. Lasnier 《Lithos》2007,98(1-4):261-274
Using ICP-MS–LA analyses, we demonstrate that the use of the Ga/Mg ratio, in conjunction with the Fe concentration, is an efficient tool in discriminating between “metamorphic” and “magmatic” blue sapphires. Magmatic blue sapphires found in alkali basalts (e.g. southeastern Asia, China, Africa) are commonly medium-rich to rich in Fe (with average contents between 2000 and 11000 ppm), high in Ga (> 140 ppm), and low in Mg (generally < 20 ppm) with high Ga/Mg ratios (> 10). Conversely, metamorphic blue sapphires found in basalts (e.g. Pailin pastel) and in metamorphic terrains (e.g. Mogok, Sri Lanka, Ilakaka) are characterized by low average iron contents (< 3000 ppm), low Ga contents (< 75 ppm), and high Mg values (> 60 ppm) with low average Ga/Mg ratios (< 10). Basaltic magmatic sapphires have Fe, Ga and Mg contents similar to those obtained for primary magmatic sapphires found in the Garba Tula syenite. This suggests that these both sets of sapphires have a possible common “syenitic” origin, as previously proposed from other criteria. In addition, plumasite-related sapphires and metamorphic sapphires also exhibit similar composition in trace elements. Based on results from the present study, we suggest that fluid circulations during a metamorphic stage produced metasomatic exchanges between mafic and acidic rocks (plumasite model), thus explaining the high Mg contents and converging Ga/Mg ratios observed in metamorphic sapphires. 相似文献
104.
揭示地质现象的本质与核心 总被引:8,自引:0,他引:8
青藏高原的形成与演化是举世瞩目的现代地学前缘 ,岩石圈结构及其演变对于探讨高原隆升及其资源环境效应具有重要意义。多年来 ,对于青藏高原岩石圈结构的认识主要基于地球物理探测结果和地质研究 ,尚未发现深达地幔的物质。我们在西昆仑地区康西瓦新生代火山岩中首次发现了以含金云母方辉橄榄岩为主的深源包体 ,其主要组成矿物为橄榄石和斜方辉石 ,含有少量单斜辉石、尖晶石和金云母。橄榄岩具有平衡粒状变晶结构 ,部分橄榄石颗粒仍保留有扭折带。电子探针分析结果表明 ,尖晶石的x(Cr) /x(Cr +Al)变化为 2 5%~ 8% ,属于尖晶石铬铁矿系列。根据CarrollWebb和Wood(1986 )提出的温压图解 ,橄榄岩形成压力大致为16 0 0MPa ,约相当于深度 56km。据此 ,认为康西瓦新生代玄武岩中产出的橄榄岩包体系岩浆活动过程中从岩石圈地幔携带上来的幔源物质 ,对于探讨青藏高原北部的岩石圈结构及其演化具有重要意义。 相似文献
105.
106.
BIOGEOGRAPHIC RELATIONS OF THE JURASSIC PECTINOIDA AND OSTREOIDA (BIVALVIA) BETWEEN TANGGULA AND OTHER AREAS 总被引:2,自引:0,他引:2
Sha Jingeng 《地学前缘》2000,(Z1)
BIOGEOGRAPHIC RELATIONS OF THE JURASSIC PECTINOIDA AND OSTREOIDA (BIVALVIA) BETWEEN TANGGULA AND OTHER AREAS 相似文献
107.
FINITE STAIN MEASUREMENT AND SHORTENING ANALYSIS IN THE NORTHERN MARGIN OF QINGHAI—TIBET PLATEAU 相似文献
108.
LONG TERM HISTORY (DEXTRAL TO SINISTRAL AND DUCTILE TO BRITTLE) OF THE DAMXUNG—JIALI SHEAR ZONE IN SOUTHERN TIBET 相似文献
109.
TECTONIC CHARACTERISTICS AND EVOLUTION OF THE QIANGTANG BASIN IN NORTHERN TIBET PLATEAU 相似文献
110.
PRESENT LANDFORMS, ACTIVE TECTONIC ZONES, DEEP STRUCTURES AND UPLIFT MECHANISMS OF THE LONGSHOUSHAN BLOCK ON THE NORTHERN MARGIN OF THE QINGHAI—TIBET PLATEAU 相似文献