首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   662篇
  免费   148篇
  国内免费   248篇
测绘学   1篇
地球物理   22篇
地质学   974篇
海洋学   28篇
天文学   2篇
综合类   17篇
自然地理   14篇
  2024年   1篇
  2023年   8篇
  2022年   20篇
  2021年   20篇
  2020年   15篇
  2019年   30篇
  2018年   20篇
  2017年   25篇
  2016年   20篇
  2015年   22篇
  2014年   44篇
  2013年   36篇
  2012年   47篇
  2011年   46篇
  2010年   45篇
  2009年   45篇
  2008年   55篇
  2007年   59篇
  2006年   42篇
  2005年   34篇
  2004年   43篇
  2003年   23篇
  2002年   44篇
  2001年   31篇
  2000年   35篇
  1999年   27篇
  1998年   34篇
  1997年   30篇
  1996年   34篇
  1995年   19篇
  1994年   23篇
  1993年   25篇
  1992年   11篇
  1991年   13篇
  1990年   11篇
  1989年   7篇
  1988年   6篇
  1987年   7篇
  1986年   1篇
排序方式: 共有1058条查询结果,搜索用时 31 毫秒
1.
A combined geochronological and geochemical investigation for the same domain of zircon provides valuable information on timing and genesis, particularly in the case of multi‐growth metamorphic zircon. A high spatial resolution concurrent analytical method for zircon U‐Pb age and rare earth element content was successfully achieved in this study, using a multi‐collector secondary ion mass spectrometer (SIMS) at a ~ 8 μm diameter scale. Special instrument parameters were employed, including a high mass resolution of approximately 15000 applied to replace the previous energy filter method, and a dynamic multi‐collector mode used to reduce the measurement time to 18 min per analysis. Six zircon reference materials yielded precise and accurate 206Pb/238U ages, which are comparable to those obtained by the ordinary mono‐collector method, but with 2–3 times higher spatial resolution. All zircon grains measured in this study showed enriched heavy‐REE (HREE) contents consistent with previously reported values determined by LA and solution ICP‐MS methods. The light‐REE (LREE) mass fractions measured using both SIMS and LA‐ICP‐MS methods in this study, although with quite different volume, show consistent results within uncertainties.  相似文献   
2.
赵保具  颜开  肖荣阁 《现代地质》2021,35(3):608-624
稀土元素的示踪作用在地质学、地球化学研究中具有重要意义,稀土参数图解可以揭示岩石的形成机理、条件和成因分类,追踪各种复杂地质作用的演化历史。利用稀土元素参数REE与SiO2REE与LREE/HREEδEu与LREE/HREE图解,在内蒙古拜仁达坝-维拉斯托铅锌银多金属矿区从偏基性端元向偏酸性端元演化的闪长岩类野外岩相学观察和室内测试的基础上,发现其全岩稀土参数之间的相关关系,进而结合岩石地球化学数据、稀土参数图解新方法与微量元素聚类分析,判别其闪长岩的成因和岩浆源区。结果显示,拜仁达坝赋矿的闪长岩具有高硅、富钠及较高MgO和Al2O3含量的特征,属钙碱性系列,显示地幔岩浆分异与下地壳熔融岩浆混合的特点;拜仁达坝-维拉斯托闪长岩LREE/HREE-REEδEu-LREE/HREE曲线显示,稀土高值组端元分别呈负相关和正相关关系,负Eu异常明显,相对富集Rb、Th、U、K等大离子亲石元素,亏损Nb、Ta、Sr、P、Ti等高场强元素,而稀土低值组端元反之。上述特征表明, 拜仁达坝-维拉斯托闪长岩为一套活动大陆边缘幔源为主、壳幔混合成因的钙碱性岩浆岩系列。实例研究初步证实,提出的稀土参数图解新方法是有效的,具有较强的普适性,适合在常规的地质科研中完善并推广。  相似文献   
3.
A 43 cm long E271 sediment core collected near the East Pacific Rise(EPR) at 13°N were studied to investigate the origin of smectite for understanding better the geochemical behavior of hydrothermal material after deposition.E271 sediments are typical metalliferous sediments. After removal of organic matter, carbonate, biogenic opal,and Fe-Mn oxide by a series of chemical procedures, clay minerals(2 μm) were investigated by X-ray diffraction,chemical analysis and Si isotope analysis. Due to the influence of seafloor hydrothermal activity and close to continent, the sources of clay minerals are complex. Illite, chlorite and kaolinite are suggested to be transported from either North or Central America by rivers or winds, but smectite is authigenic. It is enriched in iron, and its contents are highest in clay minerals. Data show that smectite is most likely formed by the reaction of hydrothermal Fe-oxyhydroxide with silica and seawater in metalliferous sediments. The Si that participates in this reaction may be derived from siliceous microfossils(diatoms or radiolarians), hydrothermal fluids, or detrital mineral phases. And their δ30 Si values are higher than those of authigenic smectites, which implies that a Si isotope fractionation occurs during the formation because of the selective absorption of light Si isotopes onto Feoxyhydroxides. Sm/Fe mass ratios(a proxy for overall REE/Fe ratio) in E271 clay minerals are lower than those in metalliferous sediments, as well as distal hydrothermal plume particles and terrigenous clay minerals. This result suggests that some REE are lost during the smectite formation, perhaps because their large ionic radii of REE scavenged by Fe-oxyhydroxides preclude substitution in either tetrahedral or octahedral lattice sites of this mineral structure, which decreases the value of metalliferous sediments as a potential resource for REE.  相似文献   
4.
《地学前缘(英文版)》2020,11(6):2141-2156
The rare earth elements and high-field-strength elements (REE-HFSE) exploration sector conducts most evaluations at deposit and smaller scales. It is not evident how the sector performs a preceding exploration stage—rating and prioritising REE-HFSE mineralised provinces—to determine which provinces are prospective enough to warrant investment. Here we present an objective, repeatable, low-cost method to screen any REE-HFSE province, as a foundation for district-scale investigations or asset evaluations. It is original for REE-HFSE screening, and adapted from regional scale copper, cobalt and petroleum exploration, and CO2 storage, screening methods. It is centred upon a mineralised province’s favourability for potential value creation, and to identify: (a) its main information gaps; (b) its weakest links; (c) its exploration maturity and remaining potential category; (d) how it compares against other REE-HFSE provinces; and (e) if further investigation is justified. This method incorporates geoscience, strategy, economic and socio-environmental factors in a way that is understandable and directly usable across stakeholder groups. The workflow is systematic, yet flexible enough to accommodate organisation-specific criteria, and usable for other commodities. It provides the platform to build a global REE-HFSE province map and database consistently across national boundaries and organisations. Categories for the extent of province exploration maturity and remaining mineral potential are proposed. We illustrate the applicability of these methods using the Gardar REE-HFSE Province (GRHP) of south Greenland. We conclude that it is a moderate size, frontier province that is currently of questionable favourability for value creation. To move GRHP into a positive favourability class, its current weak links need strengthening by research, government policy and industry stakeholders: evaluate the mineral system; integrate all information geospatially and place it in the public domain; help the region improve some community health and safety issues; convert some mineral resources into an Ore Reserves category; commence mining and sales production.  相似文献   
5.
舒小超  刘琰  李德良  贾玉衡 《岩石学报》2019,35(5):1372-1388
霓长岩化作用是指碳酸岩(或碱性岩)流体对围岩的交代蚀变,它是碳酸岩型稀土(REE)矿床常见的蚀变类型,其所形成的岩石即为霓长岩。对霓长岩的深入研究可以鉴别碳酸岩体的存在,厘定碳酸岩岩浆(或流体)的地球化学性质及源区特征,这对于找寻碳酸岩相关的矿产资源(尤其是REE)以及剖析矿床成因机制有着重要的地质意义。川西冕宁-德昌稀土矿带是中国最重要的轻稀土矿带之一,包括牦牛坪超大型、大陆槽大型、木落寨和里庄中小型REE矿床以及一系列矿点。REE矿化与碳酸岩-碱性岩杂岩体密切相关,受一系列新生代走滑断裂的控制。该矿带广泛发育霓长岩化蚀变带,尤以大陆槽及里庄矿床为显著。岩相学分析表明,大陆槽和里庄霓长岩中的矿物多呈他形粒状结构,主要由长石、黑云母、霓辉石以及少量副矿物组成;主微量元素分析表明,霓长岩的碱质(K_2O+Na_2O)、MgO、Fe_2O_3T含量较高,且富集REE、Sr、Ba等微量元素;电子探针分析表明,霓长岩中的霓辉石Fe OT含量较高,长石Na_2O及K_2O含量较高,Ca O含量极低。An-Ab-Or三角图解显示长石主要为透长石和钠长石,属碱性长石系列;黑云母的地球化学成分图解表明云母的成因类型为交代型且具有相对富镁、贫铁等特征,属镁质黑云母。霓长岩化作用的交代流体含有较高的CO_2组分,且富含碱质、Mg、Fe及REE、Sr、Ba等元素。对比霓长岩与原岩的主微量元素发现:相比于正长岩原岩,在主量元素中,霓长岩的Fe、Mg、Ca等元素含量增加,Si、Al等元素含量降低;微量元素中,霓长岩的REE及Sr、Ba等元素显著增加。这意味着交代流体含有的Fe_2O_3T、MgO、CaO等组分在霓长岩化过程中被带进了围岩,而SiO_2和Al_2O_3等从围岩中被逐出。大陆槽及里庄矿区发育的角砾岩指示了矿区曾经历过频繁的角砾岩化事件,这提高了霓长岩作用的强度,并且为矿脉的穿插及REE矿物的沉淀提供了空间。在霓长岩化过程中,流体-围岩的组分交换反复发生,这削弱了REE络合物的稳定性,伴随多期次的热液活动及构造事件,最终完成REE活化→迁移→沉淀的过程。  相似文献   
6.
《地学前缘(英文版)》2019,10(2):769-785
The Weishan REE deposit is located at the eastern part of North China Craton (NCC), western Shandong Province. The REE-bearing carbonatite occur as veins associated with aegirine syenite. LA-ICP-MS bastnaesite Th-Pb ages (129 Ma) of the Weishan carbonatite show that the carbonatite formed contemporary with the aegirine syenite. Based on the petrographic and geochemical characteristics of calcite, the REE-bearing carbonatite mainly consists of Generation-1 igneous calcite (G-1 calcite) with a small amount of Generation-2 hydrothermal calcite (G-2 calcite). Furthermore, the Weishan apatite is characterized by high Sr, LREE and low Y contents, and the carbonatite is rich in Sr, Ba and LREE contents. The δ13CV-PDB (−6.5‰ to −7.9‰) and δ13OV-SMOW (8.48‰–9.67‰) values are similar to those of primary, mantle-derived carbonatites. The above research supports that the carbonatite of the Weishan REE deposit is igneous carbonatite. Besides, the high Sr/Y, Th/U, Sr and Ba of the apatite indicate that the magma source of the Weishan REE deposit was enriched lithospheric mantle, which have suffered the fluid metasomatism. Taken together with the Mesozoic tectono-magmatic activities, the NW and NWW subduction of Izanagi plate along with lithosphere delamination and thinning of the North China plate support the formation of the Weishan REE deposit. Accordingly, the mineralization model of the Weishan REE deposit was concluded: The spatial-temporal relationships coupled with rare and trace element characteristics for both carbonatite and syenite suggest that the carbonatite melt was separated from the CO2-rich silicate melt by liquid immiscibility. The G-1 calcites were crystallized from the carbonatite melt, which made the residual melt rich in rare earth elements. Due to the common origin of G-1 and G-2 calcites, the REE-rich magmatic hydrothermal was subsequently separated from the melt. After that, large numbers of rare earth minerals were produced from the magmatic hydrothermal stage.  相似文献   
7.
程林 《地质与勘探》2020,56(4):745-758
黄陵断穹核部石墨矿是我国鳞片(晶质)石墨矿的主要产区,对该区石墨矿的研究具有重要理论和实际意义。该区已有石墨矿研究成果多侧重于矿床地质方面,对矿床成因分析缺乏地球化学支撑。为此,本文从地球化学层面查明石墨矿原岩类型,碳质富集岩相、变质作用和晶质石墨的形成,为矿床成因和成矿作用提供地球化学依据。通过系统采集区内主要石墨矿样品,进行主量元素、微量元素、稀土元素和同位素分析,根据矿床地球化学原理和分析方法,阐明石墨矿的物质来源,成矿元素集散行为和矿床形成机制。根据主量元素含量和组合,推断石墨的原岩为碳质粉砂质泥岩。微量元素的双重性指示石墨矿的物质有两个来源:中太古代野马洞岩组和中太古代东冲河片麻杂岩。独特的稀土元素配分型式说明物源转化为原岩时存在着强烈的地球化学反应。石墨矿的碳同位素组成支持碳质来自有机物的观点。  相似文献   
8.
林宇 《地质与勘探》2014,50(1):58-66
[摘要]桂西靖西念寅铝土矿不整合于早二叠茅口灰岩之上,分析其稀土元素地球化学特征对研究其物质来源具有重要意义。对念寅原生铝土矿、堆积型铝土矿及其围岩的11个样品进行稀土元素含量测试,并同靖西、平果等地各类铝土矿、茅口灰岩等样品对比分析,结果表明: (1)念寅铝土矿主量元素主要SiO2、Fe2O3、Al2O3、TiO2组成,Al2O3与Fe2O3和SiO2呈负相关;(2)念寅铝土矿球粒陨石标准化曲线与茅口灰岩配分曲线趋势一致,具有ΣREE富集、LREE与HREE分异且LREE相对富集、Eu负异常等显著特征;(3)念寅铝土矿显示出被动大陆边缘地带海相沉积的典型特征,原生铝土矿成矿物质来源主要为下伏的茅口灰岩。  相似文献   
9.
The quartz vein-type gold deposits are widely hosted by the Neoproterozoic (Xiajiang Group) epimeta- morphic clastic rock series in southeastern Guizhou Province, China. The Zhewang gold deposit studied in this paper occurs in the second lithologieal member of the Pinglue Formation of the Xiajiang Group. Trace element geochemis- try of host rocks, quartz veins and arsenopyrite has revealed that ore-forming fluid was enriched in sulphophile ele- ments such as Au, Ag, As, Sb, Pb and Zn, and simultaneously concentrated some magmaphile elements such as W and Mo, which probably provides some evidence for multi-stage mineralization or overprinting of magmatic hydro- therm. Quartz veins and arsenopyrite were characterized by depletion in HFSE and enrichment in LREE. Hf/Sm, Nb/La and Th/La imply that the ore-forming fluid was probably a NaC1-H20 solution system enriched in more C1 than F; Th/U values reflect the strong reducibility of the ore-forming fluid, coincident with the sulfide assemblages. The values of Co/Ni reflect that magmatic fluids may have partly participated in the ore-forming process and Y/Ho values have proved that the ore-forming fluid was associated with metamorphism and exotic hydrotherm which has reformed former quartz veins during late mineralization. The concentrations of REE, Eu anomalies and Ce anomalies of this deposit display that ore-forming elements mainly were derived from host rocks and possibly from a mixed deep source, and the ore-forming fluid was mixed by dominant metamorphic fluid and minor other sources. The physical-chemical conditions of ore-forming fluid changed from the initial stage to the late stage. The metamorphic fluid is responsible for the mineralization. Therefore, the Zhewang gold deposit is classified as a quartz vein-type gold deposit which may have been reformed by magmatic fluids during the late stage.  相似文献   
10.
Shallow groundwater and hot springs were collected from northeastern Guangdong Province, Southeast China, to determine the concentrations and fractionation patterns of rare-earth elements(REE). The results show that the La, Ce and Nd of REEs are abundant in groundwater and rock samples, and the ∑REE contents in groundwater and rock samples range from 126.5 to 2875.3 ng/L, and 79.44 to 385.85 mg/L, respectively. The shallow groundwater has slightly HREE-enriched PAAS-normalized patterns. However, the granitic rocks PAAS-normalized patterns, with remarkable negative Eu anomalies, are different from that of shallow groundwater. The enrichment of HREE is considered to be controlled by REE complexation and readsorption for most groundwater has Ce and Eu positive anomalies. The Ce and Eu anomalies in groundwater are controlled by redox conditions. Moreover, the Fe-contain sediments dissolution and/or the reduction of Fe oxyhydroxides are another factor contributing to Ce anomalies. The Eu anomalies in groundwater are controlled by the preferential mobilization of Eu2+ during water-rock interaction compared to Eu3+.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号