全文获取类型
| 收费全文 | 225篇 |
| 免费 | 114篇 |
| 国内免费 | 22篇 |
学科分类
| 地球科学 | 361篇 |
出版年
| 2025年 | 2篇 |
| 2024年 | 12篇 |
| 2023年 | 7篇 |
| 2022年 | 2篇 |
| 2021年 | 12篇 |
| 2020年 | 17篇 |
| 2019年 | 11篇 |
| 2018年 | 6篇 |
| 2017年 | 11篇 |
| 2016年 | 14篇 |
| 2015年 | 8篇 |
| 2014年 | 10篇 |
| 2013年 | 17篇 |
| 2012年 | 13篇 |
| 2011年 | 22篇 |
| 2010年 | 11篇 |
| 2009年 | 15篇 |
| 2008年 | 27篇 |
| 2007年 | 23篇 |
| 2006年 | 19篇 |
| 2005年 | 15篇 |
| 2004年 | 13篇 |
| 2003年 | 9篇 |
| 2002年 | 12篇 |
| 2001年 | 12篇 |
| 2000年 | 8篇 |
| 1999年 | 5篇 |
| 1998年 | 5篇 |
| 1997年 | 5篇 |
| 1996年 | 2篇 |
| 1995年 | 2篇 |
| 1994年 | 2篇 |
| 1993年 | 2篇 |
| 1992年 | 2篇 |
| 1991年 | 2篇 |
| 1990年 | 3篇 |
| 1986年 | 1篇 |
| 1977年 | 2篇 |
排序方式： 共有361条查询结果，搜索用时 15 毫秒
1.
2.
Atsushi Yamaji 《Island Arc》2016,25(1):72-83
The clustering of fracture orientations is important for tectonic studies and for geotechnical engineering. In this study, a real‐coded genetic algorithm was adopted to fitting a mixed Bingham distribution to orientation data by maximizing the log‐likelihood function of the distribution. The maximization is a difficult problem, because the function has multimodality and singularity. It was found that the algorithm was effective for this problem. Given the orientations of dilational fractures, the present method determines not only the stress axes and stress ratio of each of the fracture groups but also the maximum non‐dimensionalized fluid pressure at the time of their formation. In addition, the software calculates the 95 % error ellipses of the concentration axes. The present method found that the orientations of ore veins of the Akenobe Mine, SW Japan, should be partitioned into three clusters. It is shown that two of the groups had distinctive Zn and Sn contents, and that the ore fluids had overpressures only slightly greater than the minimum principal stress at the time of the deposition of Zn‐ and Sn‐rich veins. 相似文献
3.
《China Geology》2021,4(1):56-66
The timing of the initial Indo-Asian collision is a subject of debate for a long time. Besides, the magmatic trace of the collisional process is also unclear. In the present study, the authors report Early Eocene leucocratic sill/dike swarms in the northern edge of the Nymo intrusive complex of the Gangdese belt, southern Tibet. The Nymo intrusive complex was emplaced at ca. 50 –47 Ma and surrounded by the metamorphosed Jurassic-aged Bima Formation volcano-sedimentary sequence along its northern side. At outcrops, the leucocratic sills/dikes intruded along or truncated the deformed foliations of the host Bima Formation, which has been subject to high-temperature amphibolite-facies metamorphism at ca. 50 –47 Ma. Detailed cathodoluminescence image analyses reveal that the zircon grains of the leucocratic sills/dikes have core-mantle textures. The cores yield the Jurassic ages comparable to the protolith ages of the Bima Formation. In contrast, the mantles of zircon grains yield weighted mean ages of ca. 49–47 Ma, representing the crystallization timing of these leucocratic sills/dikes. The coeval ages for the Nymo intrusive complex, the high-temperature metamorphism, and the leucocratic sills/dikes indicate that a close relationship exists among them. The authors tentatively suggest that these leucocratic sills/dikes were generated from partial melting of the Jurassic-aged Bima Formation volcanic rocks, triggered by the high heat from the magma chamber of the Nymo intrusive complex. This Early Eocene tectono-thermal event of coeval magmatism, metamorphism and partial melting was most likely formed during the Indo-Asian collisional setting.©2021 China Geology Editorial Office. 相似文献
4.
为了探索分支河流体系河网分布规律,为创建储层建模训练图像提供知识库信息。利用Google Earth、Global Mapper、91卫图助手等现代地理信息软件,系统测量了现代格尔木河流扇表面河道分叉特征,应用Horton定律和分形方法建立了河流扇的河网形态模型。结果表明：①格尔木河流扇从顶点到入湖段共识别出26级河道,882个节点和2162个河道段,泉线上、下的河道表现出不同的河网形态;②泉线上部共发育64个节点,每级河道数目增长是上一级河道的RB=1.8900倍,每级河道平均长度是下一级河道的RL=1.0095倍,即河网形态特征参数RB=1.8900和RL=1.0095;泉线下部共发育818个节点,每级河道数目增长是上一级河道的RB=1.0279倍,每级河道平均长度是下一级河道的RL=0.9899倍,即河网形态特征参数是RB=1.0279和RL=0.9899;③河网形态特征参数受坡度影响变化较大,坡度较大则河网形态特征参数较大,坡度较小则河网形态特征参数较小。河网形态特征参数定量表征促进了分支河流体系沉积学发展,为开展陆相盆地储层建模和砂体预测提供了新的知识库信息 相似文献
5.
TM极化时,当测点越过界面时视电阻率均发生变化,基底较深时能放大界面附近的异常,当基底较深、频率较高时,高阻一侧相位低于45°,低阻一侧相位高于45°。TE极化时,只有基底为高阻时越过界面时视电阻率才发生变化,当基底为高阻且频率较高时,相位在界面两侧发生变化。通过岩脉时若相位无变化,岩脉是窄的。 相似文献
6.
新疆库科西鲁克地区广泛发育基性岩脉,多呈岩墙、岩枝和小岩滴。基性岩脉岩石类型为辉长岩和辉绿岩。辉长岩属于碱性玄武岩,而辉绿岩属于过铝质碱性系列碱玄武岩与粗面玄武岩过渡型,其形成深度（浅成相）比辉长岩浅（中深成相）。区内基性岩脉形成于闭合边缘岛弧、活动陆缘造山带环境,是由幔源原生岩浆经过分异并同化混染地壳物质而形成,结晶分异是控制岩浆演化的主要因素。辉长岩中δEu具有弱的亏损。辉绿岩δEu为正异常,而C e均具弱亏损,成岩氧逸度较高,其成因与典型的I型花岗岩类相似,为壳幔混合型。辉长岩偏幔源,而辉绿岩偏壳源,可能为幔源岩浆上侵受围岩混染所致。辉长岩年龄（119 M a）要比辉绿岩年龄（46.1M a）老,辉长岩为冈底斯陆块向欧亚大陆板块碰撞拼贴过程中,逆冲挤压结束的标志,辉绿岩为大规模逆冲挤压剪切结束,青藏高原隆升初期拉张作用的产物。 相似文献
7.
Sm/Nd isotopic age determination showed that Xiongshan dike swarm was at 585.7 Ma ± 30 Ma. The trace element geochemistry
and Sr/Nd/Pb isotope gemhemistry studies indicate that the dike swarm was products of back-arc basin spreading ridge and the
magma originated from the depleted mantle region which was metasomatized by LILE-rich liquids/melts derived from subduction
slab.
Project supported by the National Natural Science Foundation of China. 相似文献
8.
9.
甘肃马坞金矿床位于西秦岭岷礼成矿带东段,中川岩体外接触带,属于微细浸染型金矿床,达中型规模。针对矿区发育的火成岩开展野外地质学、岩相学、年代学和地球化学等研究,以揭示致矿火成岩组合及其特征,进而探讨岩石成因及金矿形成的地质背景等。野外观察显示马坞矿区金矿脉常与煌斑岩脉、石英闪长岩脉及细晶岩脉等相伴生或相互穿切,说明金矿与上述脉岩的形成时间近乎一致,故认为该脉岩群为致矿火成岩组合。马坞矿区煌斑岩和花岗质脉岩LA-MC-ICP-MS锆石U-Pb测年结果表明其形成于(153.5±3.5)~(154.9±0.9)Ma,推测金矿可能形成于晚侏罗世。该脉岩群具有宽广的SiO2、K2O、Na2O、TFeO和MgO含量,属于不同的岩性,且来自不同的岩浆源区,因此属于宽谱系岩墙群,指示其形成于造山带岩石圈拆沉作用所引发的伸展环境中。脉岩和金矿赋存于以中川岩体为代表的花岗质岩基及其围岩,表明其形成于西秦岭造山运动后期的大规模岩浆活动及岩基隆升之后,属于岩基后成矿作用的产物。 相似文献
10.
为研究适用于洞庭湖区二元结构堤基的减压井结构型式,采用室内试验对比分析了土工织物包扎塑料花管式、钢管式、砂滤体式及无砂混凝土式井管的排水减压效果,并结合洞庭湖区何家堤减压井试验工程研究了合理的滤层结构。试验表明,塑料盲沟和毛细板减压井是适合洞庭湖区二元堤基的两种减压井结构型式。 相似文献
