全文获取类型
收费全文 | 154篇 |
免费 | 13篇 |
国内免费 | 42篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 7篇 |
地球物理 | 14篇 |
地质学 | 144篇 |
海洋学 | 21篇 |
天文学 | 8篇 |
自然地理 | 14篇 |
出版年
2022年 | 5篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 11篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 7篇 |
2012年 | 4篇 |
2011年 | 12篇 |
2010年 | 7篇 |
2009年 | 9篇 |
2008年 | 11篇 |
2007年 | 13篇 |
2006年 | 10篇 |
2005年 | 3篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1983年 | 2篇 |
1981年 | 1篇 |
排序方式: 共有209条查询结果,搜索用时 31 毫秒
61.
62.
63.
64.
Yoko-Dovyren层状纯橄岩-橄长岩-辉长岩地块位于西伯利亚克拉通南部的一处褶皱构造框架中(俄罗斯贝加尔湖地区北部)。该地块的结构在其厚度最大的中部得到了着重研究。剖面底部主体成分为斜长橄榄岩,并依据内部的堆晶成分变化从下往上可分为五个主要的地层序列:纯橄岩→橄长岩→橄榄辉长岩→橄榄辉长苏长岩→石英辉长苏长岩以及含易变辉石的辉长岩。该地块的矿化包括铜-镍矿化、低硫型富铂族元素(PGE)矿化以及铬铁矿化等。另外,该地块也含多种非金属矿物原材料,如硼矿化、透辉石、各种镁质硅酸盐岩等。它们也包括纯橄岩、异剥橄榄岩和橄长岩,并以较高的品质产出,有望采掘加工成为建筑材料(水泥、混凝土、沥青混凝土和建筑陶瓷)。综合利用矿物原材料可增加矿床价值,并有助于建设环保型采矿工作体系。 相似文献
65.
Omri Gadol Gideon Tibor Uri ten Brink John K. Hall Gavrielle Groves-Gidney Gideon Bar-Am Christian Hübscher Yizhaq Makovsky 《Basin Research》2020,32(5):1156-1183
Understanding continental-slope morphological evolution is essential for predicting basin deposition. However, separating the imprints and chronology of different seafloor shaping processes is difficult. This study explores the utility of bathymetric spectral decomposition for separating and characterizing the variety of interleaved seafloor imprints of mass wasting, and clarifying their role in the morphological evolution of the southeastern Mediterranean Sea passive-margin slope. Bathymetric spectral decomposition, integrated with interpretation of seismic profiles, highlights the long-term shape of the slope and separates the observed mass transport elements into several genetic groups: (1) a series of ~25 km wide, now-buried slide scars and lobes; (2) slope-parallel bathymetric scarps representing shallow faults; (3) slope-perpendicular, open slope slide scars; (4) bathymetric roughness representing debris lobes; (5) slope-confined gullies. Our results provide a multi-scale view of the interplay between sediment transport, mass transport and shallow faulting in the evolution of the slope morphology. The base of the slope and focused disturbances are controlled by ~1 km deep salt retreat, and mimic the Messinian base of slope. The top of the open-slope is delimited by faults, accommodating internal collapse of the margin. The now-buried slides were slope-confined and presumably cohesive, and mostly nucleated along the upper-slope faults. Sediment accumulations, infilling the now-buried scars, generated more recent open-slope slides. These latter slides transported ~10 km3 of sediments, depositing a significant fraction (~3 m in average) of the sediments along the base of the studied slope during the past < 50 ka. South to north decrease in the volume of the open-slope slides highlight their role in counterbalancing the northwards diminishing sediment supply and helping to maintain a long-term steady-state bathymetric profile. The latest phase slope-confined gullies were presumably created by channelling of bottom currents into slide-scar depressions, possibly establishing incipient canyon headword erosion. 相似文献
66.
Evolving factor analysis is used to estimate the concentration profiles and spectra of Bi~(3 )and the bismuthchloride complexes BiCl~(2 )through BiCl_6~(3-)formed by injection of bismuth percblorate into a flowingstream of 1.0 mol l~(-1) HCl.The estimated spectra compare favorably with previously published spectraof the complexes. 相似文献
67.
68.
Alvaro Nivia Giselle F. Marriner Andrew C. Kerr John Tarney 《Journal of South American Earth Sciences》2006,21(4):423
The Quebradagrande Complex of Western Colombia consists of volcanic and Albian–Aptian sedimentary rocks of oceanic affinity and outcrops in a highly deformed zone where spatial relationships are difficult to unravel. Berriasian–Aptian sediments that display continental to shallow marine sedimentary facies and mafic and ultramafic plutonic rocks are associated with the Quebradagrande Complex. Geochemically, the basalts and andesites of the Quebradagrande Complex mostly display calc-alkaline affinities, are enriched in large-ion lithophile elements relative to high field strength elements, and thus are typical of volcanic rocks generated in supra-subduction zone mantle wedges. The Quebradagrande Complex parallels the western margin of the Colombian Andes’ Central Cordillera, forming a narrow, discontinuous strip fault-bounded on both sides by metamorphic rocks. The age of the metamorphic rocks east of the Quebradagrande Complex is well established as Neoproterozoic. However, the age of the metamorphics to the west – the Arquía Complex – is poorly constrained; they may have formed during either the Neoproterozoic or Lower Cretaceous. A Neoproterozoic age for the Arquía Complex is favored by both its close proximity to sedimentary rocks mapped as Paleozoic and its intrusion by Triassic plutons. Thus, the Quebradagrande Complex could represent an intracratonic marginal basin produced by spreading-subsidence, where the progressive thinning of the lithosphere generated gradually deeper sedimentary environments, eventually resulting in the generation of oceanic crust. This phenomenon was common in the Peruvian and Chilean Andes during the Uppermost Jurassic and Lower Cretaceous. The marginal basin was trapped during the collision of the Caribbean–Colombian Cretaceous oceanic plateau, which accreted west of the Arquía Complex in the Early Eocene. Differences in the geochemical characteristics of basalts of the oceanic plateau and those of the Quebradagrande Complex indicate these units were generated in very different tectonic settings. 相似文献
69.
The speciation and thermodynamic properties of ferric chloride complexes in hydrothermal solutions and hypersaline brines are still poorly understood, despite the importance of this element as a micronutrient and ore-component. Available experimental data are limited to room temperature and relatively low chloride concentrations. This paper reports results of UV-Vis spectrophotometric and synchrotron XAFS experiments of ferric chloride complexes in chloride concentrations up to 15 m and at temperatures of 25-90 °C. Qualitative interpretation of the UV-Vis spectra shows that FeCl2+, FeCl2+, FeCl3(aq) and FeCl4− were present in the experimental solutions. As chloride concentrations increase, higher ligand number complexes become important with FeCl4− predominating in solutions containing more than 10 m at 25 °C. The predominance fields of FeCl3(aq) and FeCl4− expand to lower Cl concentrations with increasing T. Both XANES and UV-Vis spectra reveal a major change in the geometry of the complex between FeCl2+ and FeCl3(aq). EXAFS data confirm that the number of chloride ligands increases with increasing chloride concentration and show that Fe3+, FeCl2+ and FeCl2+ share an octahedral geometry. FeCl3(aq) could be either tetrahedral or trigonal dipyramidal, while FeCl4− is expected to be tetrahedral. EXAFS data support a tetrahedral geometry for FeCl4−, especially at 90 °C, but do not allow to distinguish between a tetrahedral or trigonal dipyramidal geometry for FeCl3(aq) because of similar Fe-Cl distances. At room temperature, EXAFS data suggest that FeCl3(aq) may be a mixture of octahedral and tetrahedral or trigonal dipyramidal forms.The room temperature formation constants for three ferric chloride complexes (FeCl2+, FeCl3(aq) and FeCl4−) determined from the UV data are generally in good agreement with previous studies. Calculations based on the properties extrapolated to 300 °C show that hematite solubility is much higher than previously estimated, and that the high orders complexes FeCl3(aq) and FeCl4− are important at high temperatures even in solutions with low chloride concentrations. The accuracy of these properties is limited by a poor understanding of activity-composition relationships in concentrated electrolytes, and by limitations in the available experimental techniques and extrapolation algorithms; however, the inclusion of higher order complexes in numerical models of ore transport and deposition allows for a more accurate qualitative prediction of Fe behaviour in hydrothermal and hypersaline systems. 相似文献
70.
藏北羌塘泛非和印支事件的记录:来自俄久卖变质杂岩地球化学与锆石U-Pb年代学的证据 总被引:3,自引:2,他引:1
藏北羌塘盆地大地构造属性是长期争议的议题,深入研究有助于对该问题的探讨。俄久卖杂岩体产出于羌塘盆地中央隆起带北缘,包括夕线石片麻岩和片麻状花岗岩,以及侵位于其中的淡色花岗岩脉。在中央隆起北侧,高级变质岩仅发现于俄久卖杂岩体内。因此,该杂岩为研究羌塘盆地构造演化的重要窗口。在区域地质调查的基础上,本文重点对片麻状花岗岩和淡色花岗岩开展了岩石学、锆石U-Pb年代学与地球化学研究。其中,片麻状花岗岩加权平均年龄为476.6±4.8Ma,且岩石中大离子亲石元素Rb、Ba、Th和Pb相对富集,高场强元素Nb、Ta、Ti和P较亏损,显示弧火山岩的地球化学特征。淡色花岗岩中的锆石呈明显的核-幔-边环带结构,其核部测得年龄介于2052±25Ma~541±8Ma之间,幔部加权平均年龄为463.7±7.5Ma,边部内侧为214.6±2Ma,边部外侧为189.4±1.1Ma。地球化学特征表明该淡色花岗岩形成于典型的同碰撞构造环境。综合研究表明,俄久卖杂岩体包括早古生代泛非晚期岩浆事件产物(~470Ma),且在印支运动期遭受深埋作用并发生部分熔融,分别形成了~214Ma和~189Ma的淡色花岗岩。因此,羌塘盆地内泛非时期的地质记录可延伸至中央隆起带北缘。 相似文献