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2.
The auriferous veins at Jinniushan occurs within the Jinniushan faulted zone in the Kunyushan Granite. Optical observation reveals that gold ore body formed during the main stage of hydrothermal activity. Detailed geothermometric studies of fluid inclusions from the veins show that the forming temperature ranges between 130℃ and 370℃ and the salinity is from 4.01 to 15.21 wvt percent NaCl. The ore-forming fluid is featured by low to moderate salinity, and low to moderate temperature. According to investigations of the values of vapor/liquid and temperatures of the ore-forming fluids, we propose that the boiling fluid inclusions exist in the main mineralization stages. Fluid boiling is suggested as a mechanism for the precipitation of gold from the hydrothermal fluid in the Jinniushan gold deposit. 相似文献
3.
西藏搭格架热泉型铯矿床矿物学与矿石组构特征及地质意义 总被引:5,自引:1,他引:4
在查明搭格架铯矿床产出的地质背景、成矿阶段及其年龄、地球化学与同位素组成的基础上,本文较为系统地研究了硅华的矿物学与组构特征,加深了对硅华形成演化过程的认识.研究表明成矿早期,矿石中存在大量的石英,晚期全为蛋白石.粒状蛋白石自早到晚均有出现,胶状蛋白石主要出现于晚期.早期矿石出现脱水造成的菜花状、粗粒块状与粗大孔隙状构造及溶蚀结构.晚期出现细粒块状与细小孔隙状构造.在第3阶段存在硅藻Denticula属,体现出低温阶段的特征.由早到晚,矿石的SiO2呈降低趋势,而(Na2O Al2O3 K2O CaO)与Cs2O呈升高趋势,是随着矿石中SiO2有序度的降低而其它成分被保留在晶格中所致. 相似文献
4.
岩矿显微组构对水银洞金矿成因的指示 总被引:1,自引:0,他引:1
黔西南水银洞金矿为产于上二叠统龙潭组中的超大型、高品位金矿床,矿床由多个金矿体组成.工业金矿体顺层产于龙潭组含煤地层所夹的玄武质、硅质、生物碎屑碳酸盐岩中.对水银洞金矿赋矿地层岩石以及矿石显微组构进行了研究,矿石中主要载金矿物为细粒黄铁矿,具再生边、粒内孔隙、铸模孔隙结构及镶边生物矿化构造、铸模式生物矿化构造,是一典型的具沉积一成岩组构.金矿化与硅化有密切的成因联系,金与SiO2来源于峨嵋山玄武岩的喷溢活动,主要金矿体更多显示与峨嵋山玄武岩准同生特征.矿床为沉积一成岩弱改造成囚金矿床. 相似文献
5.
黑海西北部冷泉碳酸盐岩的沉积岩石学特征及氧化还原条件的稀土元素地球化学示踪 总被引:3,自引:1,他引:2
黑海西北部罗马尼亚大陆架(水深120m)和乌克兰陆坡(水深190m)发育冷泉碳酸盐岩结壳。XRD测试表明此结壳主要由高镁方解石和文石组成。结壳中与渗漏系统微生物活动有关的凝块和葡萄状文石等特殊的沉积组构非常发育。冷泉碳酸盐岩酸可溶部分(碳酸盐岩相矿物)的稀土元素含量很低(0.068×10-6~2.817×10-6),稀土元素页岩标准化配分模式显示罗马尼亚大陆架冷泉碳酸盐岩具有明显的Ce负异常,乌克兰陆坡冷泉碳酸盐岩具Ce的正异常,表明它们是分别在氧化和还原环境中沉积的。稀土元素和V、Cd和U等微量元素的含量在泥晶中最高,亮晶中最低,可能反映成岩过程对元素含量有控制作用。 相似文献
6.
The behaviour of quartz during metamorphism is studied based on two case studies from the Barrovian terrains of Sulitjelma in arctic Scandinavia and Loch Tay in the Central Highlands Dalradian of Scotland. Both terrains preserve evidence for metamorphism in pelites involving nucleation and growth of garnet at different times in the deformation history. Data are presented on the size, shape and crystallographic orientation of quartz preserved as inclusions in garnet and as grains in the surrounding matrix. While quartz-grains remain small and dispersed between mica grains, deformation appears to be dominated by grain-boundary sliding accommodated by dissolution–precipitation. At amphibolite facies, textural coarsening occurs by dissolution of small quartz grains and growth of larger quartz grains, coupled with segregation of quartz from mica. As a result, quartz deforms by dislocation creep, developing crystallographic preferred orientations (CPO) consistent with both coaxial and non-coaxial strain. Quartz CPOs with <0001> axes lying parallel to foliation and stretching direction are commonly developed, and best explained by mechanical rotation of inequant (detrital?) quartz grains. There is no evidence for selective entrapment of quartz inclusions in garnet on the basis of quartz crystallographic orientation. 相似文献
7.
Postcollisional flow of aqueous fluid within ultrahigh-pressure eclogite in the Dabie orogen 总被引:1,自引:0,他引:1
Tian-Shan Gao Song-Shan Wang Bing Gong Yuan-Bao Wu Yong-Fei Zheng 《Journal of Geochemical Exploration》2006,89(1-3):115
A combined study of chronometric dating and oxygen isotope analysis for minerals from vein and host eclogite as well as regional country-rock gneiss in the Dabie orogen provides a direct constraint on timing of fluid flow in this orogen formed by continental collision. Oxygen isotope ratios of vein minerals are significantly lower than those of the host eclogite, but comparable with those of the regional gneiss. This suggests the veining fluid came from the regional gneiss (i.e. exhumed slab itself) rather than the host eclogite. While zircon U–Pb and phengite Ar–Ar dating yields ages of 214 to 222 Ma for the eclogite and gneiss, the vein gives a quartz–muscovite Rb–Sr isochron age of 181 Ma and a muscovite K–Ar age of 179 Ma. Thus the veining postdates the Triassic ultrahigh pressure metamorphic event, witnessing postcollisional fluid flow after the orogenic cycle of continental collision. 相似文献
8.
Yang Liu Alfred T. Anderson Colin J. N. Wilson Andrew M. Davis Ian M. Steele 《Contributions to Mineralogy and Petrology》2006,151(1):71-87
Large pyroclastic rhyolites are snapshots of evolving magma bodies, and preserved in their eruptive pyroclasts is a record
of evolution up to the time of eruption. Here we focus on the conditions and processes in the Oruanui magma that erupted at
26.5 ka from Taupo Volcano, New Zealand. The 530 km3 (void-free) of material erupted in the Oruanui event is comparable in size to the Bishop Tuff in California, but differs
in that rhyolitic pumice and glass compositions, although variable, did not change systematically with eruption order. We
measured the concentrations of H2O, CO2 and major and trace elements in zoned phenocrysts and melt inclusions from individual pumice clasts covering the range from
early to late erupted units. We also used cathodoluminescence imaging to infer growth histories of quartz phenocrysts. For
quartz-hosted inclusions, we studied both fully enclosed melt inclusions and reentrants (connecting to host melt through a
small opening). The textures and compositions of inclusions and phenocrysts reflect complex pre-eruptive processes of incomplete
assimilation/partial melting, crystallization differentiation, magma mixing and gas saturation. ‘Restitic’ quartz occurs in
seven of eight pumice clasts studied. Variations in dissolved H2O and CO2 in quartz-hosted melt inclusions reflect gas saturation in the Oruanui magma and crystallization depths of ∼3.5–7 km. Based
on variations of dissolved H2O and CO2 in reentrants, the amount of exsolved gas at the beginning of eruption increased with depth, corresponding to decreasing
density with depth. Pre-eruptive mixing of magma with varying gas content implies variations in magma bulk density that would
have driven convective mixing.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献
9.
Michael Stipp Holger Stünitz Rene Heilbronner Stefan M. Schmid 《Journal of Structural Geology》2002,24(12)
Near the eastern end of the Tonale fault zone, a segment of the Periadriatic fault system in the Italian Alps, the Adamello intrusion produced a syn-kinematic contact aureole. A temperature gradient from 250 to 700 °C was determined across the Tonale fault zone using critical syn-kinematic mineral assemblages from the metasedimentary host rocks surrounding deformed quartz veins. Deformed quartz veins sampled along this temperature gradient display a transition from cataclasites to mylonites (frictional–viscous transition) at 280±30 °C. Within the mylonites, zones characterized by different dynamic recrystallization mechanisms were defined: Bulging recrystallization (BLG) was dominant between 280 and 400 °C, subgrain rotation recrystallization (SGR) in the 400–500 °C interval, and the transition to dominant grain boundary migration recrystallization (GBM) occurred at 500 °C. The microstructures associated with the three recrystallization mechanisms and the transitions between them can be correlated with experimentally derived dislocation creep regimes. Bulk texture X-ray goniometry and computer-automated analysis of preferred [c]-axis orientations of porphyroclasts and recrystallized grains are used to quantify textural differences that correspond to the observed microstructural changes. Within the BLG- and SGR zones, porphyroclasts show predominantly single [c]-axis maxima. At the transition from the SGR- to the GBM zone, the texture of recrystallized grains indicates a change from [c]-axis girdles, diagnostic of multiple slip systems, to a single maximum in Y. Within the GBM zone, above 630±30 °C, the textures also include submaxima, which are indicative of combined basal a- and prism [c] slip. 相似文献
10.