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101.
赣南横市地区基性岩墙的LA-ICP-MS锆石U-Pb年龄、地球化学特征及其地质意义 总被引:1,自引:0,他引:1
本文对江西赣南横市地区基性岩墙进行了年代学、岩石学和地球化学研究,主量元素特征和微量元素分析结果显示,基性岩墙为拉斑玄武岩系列和钙碱性系列,属于富钠基性岩类;Ti O2含量较高,平均含量1%,属于钛较高的基性岩类;A/NCK均小于1,属于准铝质基性岩类,具幔源型岩浆特征。基性岩墙LA-ICP-MS锆石U-Pb定年法测年结果为422.8±1.8 Ma和421.7±2.2 Ma,时代属于晚志留世,表明该基性岩墙是加里东期褶皱造山运动期后拉张(伸展)作用的产物。该地区不仅出露了加里东期同造山期和后造山期两类酸性花岗岩岩体,而且在该地区还同时出现加里东期的酸性岩类及基性岩类,大致反映了该地区从挤压型酸性岩浆侵位逐渐转换为拉张环境的基性岩浆侵位构造过程。 相似文献
102.
Caroline‐Emmanuelle Morisset James S. Scoates Dominique Weis André Rahier 《Geostandards and Geoanalytical Research》2014,38(2):159-176
The high abundances of the high field‐strength elements in ilmenite and rutile make these minerals particularly suitable for hafnium isotopic investigations. We present a technique for separating Hf by ion exchange chemistry from high‐TiO2 (> 40% m/m) minerals to achieve precise Hf isotopic composition analyses by MC (multiple collector)‐ICP‐MS. Following digestion and conversion to chlorides, the first elution column is used to separate iron and the rare earth elements, the second column is designed to separate most of the titanium from Hf, an evaporation step using HClO4 is then performed to remove any trace of HF in preparation for the third column, which is needed to eliminate any remaining trace of titanium. The modified chemistry helped to improve the yields from < 10 to > 78% as well as the analytical precision of the processed samples (e.g., sample 2033‐A1, 176Hf/177Hf = 0.282251 ± 25 before vs. 0.282225 ± 6 after). The technique was tested on a case study in which the Hf isotopic ratios of ilmenite and rutile (analysed prior to the chemistry improvement) were determined and permitted to evaluate that the origin of rutile‐bearing ilmenite deposits is from the same or similar magma than their, respectively, associated Proterozoic anorthosite massifs (Saint‐Urbain and Lac Allard) of the Grenville Province in Québec, Canada. 相似文献
103.
Colter J. Kelly Christopher R.M. McFarlane David A. Schneider Simon E. Jackson 《Geostandards and Geoanalytical Research》2014,38(4):389-407
Laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) was examined as a tool for measuring isotopic variation as a function of ablation depth in unpolished zircon from an Archaean metasediment specimen. This technique was able to identify micrometre‐thin (> 3 μm) isotopically distinct mineral domains characterised by ca. 100 Myr younger 207Pb/206Pb ages associated with 2s age uncertainties as low ~ 0.2%, as well as elevated U content relative to grain interiors (up to an order of magnitude). Our calculated drilling rate suggests that each laser pulse excavated depths of ~ 0.06 μm. Ages resolved through the LA‐ICP‐MS methods overlap the 2s uncertainties of 207Pb/206Pb ages measured using SIMS depth profiling on the same zircon population. The rims were further evinced by the detection of relative enrichment (> 3 orders of magnitude) in REE in the outermost micrometres of the same zircon, measured using a different and independent LA‐ICP‐MS depth profiling technique. We propose a LA‐ICP‐MS U–Pb technique capable of quickly identifying and quantifying rims, which are indication of late, yet geologically significant, fluid events that are otherwise undefined. 相似文献
104.
David M. Chew Ray A. Donelick Margaret B. Donelick Balz S. Kamber Michael J. Stock 《Geostandards and Geoanalytical Research》2014,38(1):23-35
Apatite incorporates variable and significant amounts of halogens (mainly F and Cl) in its crystal structure, which can be used to determine the initial F and Cl concentrations of magmas. The amount of chlorine in the apatite lattice also exerts an important compositional control on the degree of fission‐track annealing. Chlorine measurements in apatite have conventionally required electron probe microanalysis (EPMA). Laser ablation inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) is increasingly used in apatite fission‐track dating to determine U concentrations and also in simultaneous U‐Pb dating and trace element measurements of apatite. Apatite Cl measurements by ICP‐MS would remove the need for EPMA but the high (12.97 eV) first ionisation potential makes analysis challenging. Apatite Cl data were acquired using two analytical set‐ups: a Resonetics M‐50 193 nm ArF Excimer laser coupled to an Agilent 7700× quadrupole ICP‐MS (using a 26 μm spot with an 8 Hz repetition rate) and a Photon Machines Analyte Excite 193 nm ArF Excimer laser coupled to a Thermo Scientific iCAP Qc (using a 30 μm spot with a 4 Hz repetition rate). Chlorine concentrations were determined by LA‐ICP‐MS (1140 analyses in total) for nineteen apatite occurrences, and there is a comprehensive EPMA Cl and F data set for 13 of the apatite samples. The apatite sample suite includes different compositions representative of the range likely to be encountered in natural apatites, along with extreme variants including two end‐member chlorapatites. Between twenty‐six and thirty‐nine isotopes were determined in each apatite sample corresponding to a typical analytical protocol for integrated apatite fission track (U and Cl contents) and U‐Pb dating, along with REE and trace element measurements. 35Cl backgrounds (present mainly in the argon gas) were ~ 45–65 kcps in the first set‐up and ~ 4 kcps in the second set‐up. 35Cl background‐corrected signals ranged from ~ 0 cps in end‐member fluorapatite to up to ~ 90 kcps in end‐member chlorapatite. Use of a collision cell in both analytical set‐ups decreased the low mass sensitivity by approximately an order of magnitude without improving the 35Cl signal‐to‐background ratio. A minor Ca isotope was used as the internal standard to correct for drift in instrument sensitivity and variations in ablation volume during sessions. The 35Cl/43Ca values for each apatite (10–20 analyses each) when plotted against the EPMA Cl concentrations yield excellently constrained calibration relationships, demonstrating the suitability of the analytical protocol and that routine apatite Cl measurements by ICP‐MS are achievable. 相似文献
105.
Trace Element Geochemistry of Magnetite from the Fe(-Cu) Deposits in the Hami Region, Eastern Tianshan Orogenic Belt, NW China 总被引:5,自引:0,他引:5
Laser ablation–inductively coupled plasma–mass spectrometry(LA–ICP–MS) was used to determine the trace element concentrations of magnetite from the Heifengshan, Shuangfengshan, and Shaquanzi Fe(–Cu) deposits in the Eastern Tianshan Orogenic Belt. The magnetite from these deposits typically contains detectable Mg, Al, Ti, V, Cr, Mn, Co, Ni, Zn and Ga. The trace element contents in magnetite generally vary less than one order of magnitude. The subtle variations of trace element concentrations within a magnetite grain and between the magnetite grains in the same sample probably indicate local inhomogeneity of ore–forming fluids. The variations of Co in magnetite between samples are probably due to the mineral proportion of magnetite and pyrite. Factor analysis has discriminated three types of magnetite: Ni–Mn–V–Ti(Factor 1), Mg–Al–Zn(Factor 2), and Ga– Co(Factor 3) magnetite. Magnetite from the Heifengshan and Shuangfengshan Fe deposits has similar normalized trace element spider patterns and cannot be discriminated according to these factors. However, magnetite from the Shaquanzi Fe–Cu deposit has affinity to Factor 2 with lower Mg and Al but higher Zn concentrations, indicating that the ore–forming fluids responsible for the Fe–Cu deposit are different from those for Fe deposits. Chemical composition of magnetite indicates that magnetite from these Fe(–Cu) deposits was formed by hydrothermal processes rather than magmatic differentiation. The formation of these Fe(–Cu) deposits may be related to felsic magmatism. 相似文献
106.
Yali Sun Shengling Sun Christina Yan Wang Peng Xu 《Geostandards and Geoanalytical Research》2013,37(1):65-76
A method was developed for the determination of low‐level rare earth elements (REEs) and thorium in ultramafic samples by inductively coupled plasma‐mass spectrometry. The conventional method for the digestion of ultramafic rocks using HNO3 and HF results in considerable amounts of insoluble fluorides because of the high contents of Mg (generally up to 24% m/m) in these rocks. In this study, we used H3BO3 as a complexing agent to break down the insoluble fluorides, and then separated the REEs from Fe and Mg major and Ba, Ca, Cr minor matrices by anion exchange and co‐precipitation, respectively. The whole procedural blanks estimated from sample‐free analyses ranged from 0.232 ng for Ce to 0.006 ng for Tm and Lu. Limits of detection for this method, defined as three times the standard deviation of these blank analyses, varied from 0.51 ng g?1 for Ce to 0.03 ng g?1 for Lu. The recovery of REEs using this technique, as determined using the standard addition method, ranged from 92.9% for Y to 102.0% for Er with 3% (RSD) variation. The method was validated using GAS (GeoPT‐12), JP‐1 and PCC‐1, and the results were comparable to literature values, elucidating the applicability to the determination of ultra trace REEs in ultramafic rocks. 相似文献
107.
Here, we present determinations of thallium (Tl) concentrations in the USGS reference materials BIR‐1G, BHVO‐2G and BCR‐2G measured by solution ICP‐MS. The Tl content in these three glasses spans a range of about 2–230 ng g?1, which is similar to the values published for the respective powder materials. The determined range of Tl concentrations in these three glass reference materials makes them ideal for investigating Tl concentrations in basaltic and andesitic volcanic glasses. We also performed a series of laser ablation ICP‐MS measurements on the three samples, which show that this technique is able to determine Tl concentrations in glass samples with concentrations as low as 2 ng g?1. 相似文献
108.
Sukran Akkus Tulin Bal Nagihan M. Karaaslan Emre Yaman Ersin Kilinc Mehmet Yaman 《洁净——土壤、空气、水》2013,41(12):1229-1234
Five‐step sequential extractions were employed to fractionation of Ni, Cr and Cu in soil polluted by anthropogenic activities and determine the mobility of the metals. Twelve samples were collected on an agricultural area that was located near an airport and intercity roads in Elazig‐Turkey. Exchangeable, organically bounded, carbonate bounded, adsorbed species on Fe and Mn oxides and residual species (except silicates) of Ni, Cr and Cu were extracted into solution by using CaCl2, Na4P2O7, Na2EDTA, NH2OH–HCl and HNO3–H2O2, respectively. Mobile metal concentrations in fractions and total recoverable in soils were determined by using inductively coupled plasma‐optical emission spectrometry (ICP‐OES). Total recoverable Ni, Cr and Cu concentrations were in the range of 40–119, 45–126 and 23–72 mg kg?1, respectively. It was observed that total concentrations of metals in some of the samples were higher than the permitted values. The sum of the mobile percentages of metals was found to be lower than 50%. The Ni, Cr and Cu percentages for exchangeable species are in the ranges of 0.18–1.64, 0.03–0.59 and 0.42–2.53%, respectively. 相似文献
109.
Nguo Sylvestre KANOUO Khin ZAW Rose Fouateu YONGUE Frederick Lin SUTHERLAND Sebastien MEFFRE Emmanuel NJONFANG Changqian MA Milan Stafford TCHOUATCHA 《Resource Geology》2012,62(3):316-324
Zircons and other heavy minerals (corundum, rutile, ilmenite, magnetite, sillimanite) are identified in the Nsanaragati gem corundum placer deposit, in the western part of the Mamfe sedimentary basin, SW Cameroon. These alluvial minerals have different morphological characteristics and zircons, in particular, vary mostly in colour and shape. They are reddish, brownish, yellowish, pink or colourless. These minerals form rounded and sub‐rounded alluvial grains, prismatic, pyramidal or dipyramidal crystals. Reddish zircons retain their original crystallographic shape. Trace element and U–Pb isotopic geochemical analyses of these reddish zircons, using the LA‐ICP‐MS method give significant Hf (4576–6334 ppm), Th (46–1565 ppm) and U (66–687 ppm) contents, with Th/U ratio ranging from 0.6 to 3.0. The 206Pb/238U corrected mean age gave 12.39 ± 0.55 Ma, which characterizes an Upper Cenozoic (Serravallian) magmatic event. The zircons are probably sourced from a magmatic field in the South eastern boundary of the Cross River Formation. The Cameroon Volcanic Line of basaltic and alkaline lavas and intrusions which lie east of the Mamfe Basin mostly range in age from 37 Ma to <1 Ma. The zircons may also relate to the Mount Bambouto plateau lavas which lie northeast of the Mamfe sedimentary basin and have an eruptive age range of 21–14 Ma. The oldest Nsanaragati reddish zircon ages overlap within error with the end stages of the Bambouto eruptions. This eruptive or a related episode provides a potential source for megacrystic reddish zircons within the Nsanagarati placer deposit. 相似文献
110.
Patrick H. Donohue Antonio Simonetti Clive R. Neal 《Geostandards and Geoanalytical Research》2012,36(1):61-73
Seven ilmenite (FeTiO3) megacrysts derived from alnöite pipes (Island of Malaita, Solomon Islands) were characterised for their major and trace element compositions in relation to their potential use as secondary reference materials for in situ microanalysis. Abundances of thirteen trace elements obtained by laser ablation ICP‐MS analyses (using the NIST SRM 610 glass reference material) were compared with those determined by solution‐mode ICP‐MS measurements, and these indicated good agreement for most elements. The accuracy of the LA‐ICP‐MS protocol employed here was also assessed by repeated analysis of MPI‐DING international glass reference materials ML3B‐G and KL2‐G. Several of the Malaitan ilmenite megacrysts exhibited discrepancies between laser ablation and solution‐mode ICP‐MS analyses, primarily attributed to the presence of a titano‐magnetite exsolution phase (at the grain boundaries), which were incorporated solely in the solution‐mode runs. Element abundances obtained by LA‐ICP‐MS for three of the ilmenite megacrysts (CRN63E, CRN63H and CRN63K) investigated here had RSD (2s) values of < 20% and therefore can be considered as working values for reference purposes during routine LA‐ICP‐MS analyses of ilmenite. 相似文献