全文获取类型
收费全文 | 415篇 |
免费 | 47篇 |
国内免费 | 74篇 |
专业分类
测绘学 | 10篇 |
大气科学 | 11篇 |
地球物理 | 59篇 |
地质学 | 354篇 |
海洋学 | 24篇 |
天文学 | 8篇 |
综合类 | 31篇 |
自然地理 | 39篇 |
出版年
2023年 | 2篇 |
2022年 | 8篇 |
2021年 | 19篇 |
2020年 | 8篇 |
2019年 | 16篇 |
2018年 | 10篇 |
2017年 | 10篇 |
2016年 | 11篇 |
2015年 | 14篇 |
2014年 | 36篇 |
2013年 | 24篇 |
2012年 | 26篇 |
2011年 | 42篇 |
2010年 | 37篇 |
2009年 | 39篇 |
2008年 | 39篇 |
2007年 | 31篇 |
2006年 | 27篇 |
2005年 | 22篇 |
2004年 | 13篇 |
2003年 | 15篇 |
2002年 | 17篇 |
2001年 | 18篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有536条查询结果,搜索用时 359 毫秒
431.
玲珑金矿田东风矿床171号脉金矿,产于胶西北地区著名的玲珑金矿田南东部,受NEE向破头青断裂控制。矿脉、矿体形态、产状与断裂带基本相同,带内岩石蚀变分带现象较明显;矿体主要分布于断裂带下盘,呈似层状、大脉状,沿走向及倾向显舒缓波状,局部具分支、复合特征;厚度变化较稳定,有用组分分布较均匀;矿石类型包括黄铁绢英岩型和黄铁绢英岩质碎裂岩型。研究表明,中生代燕山晚期的构造—岩浆活动为成矿提供了热源及定位空间,成矿物质具壳、幔混合源特征,成矿流体主要来源于幔源,有大气水和岩浆水的加入;矿床成因为中温热液型金矿。 相似文献
432.
近年的研究表明,渤海海域428凸起地区沙一二段具有良好的油气勘探前景。通过钻井、岩心、薄片、地震资料的综合分析,识别出研究区发育扇三角洲、湖泊相以及一种特殊的沉积类型——混合沉积,并对其平面分布和相互关系进行了研究。本区沉积体系的发育主要受控于物源体系、同沉积断裂样式、古地形等因素。其中,物源体系控制了砂体发育的规模,同沉积断裂样式控制了砂体的平面展布,有利的古地形条件控制了混合沉积的发育位置。 相似文献
433.
Formation Age and Evolution Time Span of the Koktokay No. 3 Pegmatite,Altai, NW China: Evidence from U–Pb Zircon and 40Ar–39Ar Muscovite Ages
下载免费PDF全文
![点击此处可从《Resource Geology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Qifeng Zhou Kezhang Qin Dongmei Tang Ye Tian Mingjian Cao Chunlong Wang 《Resource Geology》2015,65(3):210-231
The Koktokay No. 3 pegmatite is the largest Li–Be–Nb–Ta–Cs pegmatitic rare‐metal deposit of the Chinese Altai orogenic belt, and is famous for its concentric ring zonation pattern (nine internal zones). However, the formation age and evolution time span have been controversial. Here, we present the results of LA‐ICP–MS zircon U–Pb dating and muscovite 40Ar–39Ar dating. Four groups of zircon U–Pb ages (~210 Ma, ~193–198 Ma, ~186–187 Ma and ~172 Ma) for Zones II, V, VI, VII, and VIII, and a weighed mean 206Pb/238U age of 965 ± 11 Ma for Zone IV are identified. Also, Zones II, IV, and VI have muscovite 40Ar–39Ar plateau ages of 179.7 ± 1.1 Ma, 182.1 ± 1.0 Ma, and 181.8 ± 1.1 Ma, respectively. Considering previous U–Pb age studies (Zones I, V, and VII), the ages of emplacement, Li mineralization peak, hydrothermal stage of the No. 3 pegmatite are in ranges of 193–198 Ma, 184–187 Ma and 172–175 Ma, with weighted mean 206Pb–238U ages of 194.8 ± 2.3 Ma, 186.6 ± 1.3 Ma and 173.1 ± 3.9 Ma, respectively. The No. 3 pegmatite formed in the early Jurassic. The results of xenocrysts suggest that there is another pegmatite forming event of around 210 Ma in the mining district and the old zircon U–Pb ages imply that Neoproterozoic crustal rocks pertain to sources of the No. 3 pegmatite. Including the previous muscovite 40Ar–39Ar age studies (Zones I and V), a cooling age range of 177–182 Ma is considered as the time of hydrothermal stage and end of formation. The evolution process of the No. 3 pegmatite lasted 16 Ma. Therein, the magmatic stage continued for 9–11 Myr and the magmatic–hydrothermal transition and hydrothermal stages were sustained at 5–7 Ma. These time spans are long because of huge scale, cupola shape, large formation depth, and complex internal zoning patterns and formation processes. Considering some pegmatite dikes in the Chinese Altai, there is an early Jurassic pegmatite forming event. 相似文献
434.
Nitrogen and Phosphorus Recovery from Human Urine by Struvite Precipitation and Air Stripping in Vietnam 总被引:1,自引:0,他引:1
A “No Mix” sanitation system was installed in a dormitory at the University of CanTho in South Vietnam, with the objective of recycling nutrients from source separated wastewater streams. This paper presents the “Yellow Water” treatment plant and its efficiency in recovering phosphorus and nitrogen from human urine. The pilot plant achieved phosphorus removal efficiencies of 98% with both diluted and undiluted urine. Phosphorus was recovered in the form of struvite, a solid mineral fertilizer with heavy metal concentrations being below the German Fertilizer Regulation's threshold limits. About 110 g of struvite could be generated after one treatment cycle, during which 50 L of urine were processed. Nitrogen removal by air stripping showed best results when circulating the urine for 3 h through the stripping column at a high flow rate (80 L/h). With these settings, more than 90% of the nitrogen could be removed from the urine, and virtually 100% of this nitrogen could be recovered in the form of liquid ammonium sulfate. In the future, treatment costs could be further reduced by making use of the solar energy that is available during daytime in South Vietnam. 相似文献
435.
436.
以粤北302铀矿床ZK23-2钻孔为研究对象,通过显微镜下薄片鉴定、岩石地球化学和流体包裹体分析等对该矿床的围岩蚀变进行研究。结果表明,302矿床蚀变种类繁多,蚀变类型主要有:碱性长石化、硅化、绢云母化、红化、绿泥石化、绿(褐)帘石化、碳酸盐化、高岭石化等。矿床表现出明显的垂直分带和水平分带特征。从上至下,将ZK23-2划分为4个蚀变带:红化、绢云母化带→硅化、红化、强绢云母化带(铀富集带)→绿泥石化、绢云母化带→弱蚀变或正常花岗岩带。岩石的主量元素、微量元素和稀土元素均规律变化,微量元素分布模式和稀土元素配分模式均与赋矿围岩长江岩体的趋势一致,说明蚀变作用对它们的影响小,致使蚀变岩石基本保持原岩的地球化学特征。各蚀变带包裹体的均一温度均低于220℃,属于中低温热液,惰性气体N2在各蚀变带包裹体中普遍存在,强蚀变带的包裹体气相成分中均含CO2,表明在铀矿的形成过程中,铀的溶解、迁移以及富集成矿作用与CO2气体密切相关并发生在N2环境中。此外,成矿期脉石矿物包裹体的均一温度和压力为正相关的平滑曲线,表明围岩蚀变的分带特征主要是由成矿热液流体的混合作用引起的。 相似文献
437.
438.
Similar to most mountain glaciers in the world, Urumqi Glacier No. 1 (UG1), the best observed glacier in China with continued glaciological and climatological monitoring records of longer than 50 years has experienced an accelerated recession during the past several decades. The purpose of this study is to investigate the acceleration of recession. By taking UG1 as an example, we analyze the generic mechanisms of acceleration of shrinkage of continental mountain glaciers. The results indicate that the accel... 相似文献
439.
This article, based on the field work took place on the zone of Tuomuer (托木尔) Peak, western Tian Shan (天山) during the period May 2008 to September 2009, obtained the spatial distribution of debris layer on the reference glaciers (Glacier No. 72, Glacier No. 74, Tuomuer Glacier) by detailed measurements of debris thickness and ablation rates on glacier and further by Spot-5 (5 m, 2005) high-resolution satellitic image applying remote sensing and geographic information systems approach to research the spatial... 相似文献
440.