全文获取类型
收费全文 | 73篇 |
免费 | 4篇 |
专业分类
大气科学 | 5篇 |
地球物理 | 15篇 |
地质学 | 38篇 |
海洋学 | 6篇 |
天文学 | 10篇 |
自然地理 | 3篇 |
出版年
2023年 | 1篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 1篇 |
2011年 | 11篇 |
2010年 | 10篇 |
2009年 | 5篇 |
2008年 | 6篇 |
2007年 | 3篇 |
2006年 | 6篇 |
2005年 | 2篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
排序方式: 共有77条查询结果,搜索用时 296 毫秒
41.
New insight into the structure of nanocrystalline ferrihydrite: EXAFS evidence for tetrahedrally coordinated iron(III) 总被引:1,自引:0,他引:1
Fabien Maillot Yuheng Wang Philippe Ildefonse Corinne Chaneac 《Geochimica et cosmochimica acta》2011,75(10):2708-9890
Ferrihydrite (Fh) is a short-range ordered nanocrystalline iron(III) (oxyhydr)oxide that has been recognized to play an important role in contaminant sequestration and in iron cycling in geological and biological systems. Despite intensive research for the two last decades, the structure of Fh is still a subject of debate. In the present study, we report extended X-ray absorption fine structure (EXAFS) spectroscopy data collected on a large set of ferrihydrites and model compounds samples including especially nano-crystalline maghemite (Mh), goethite (Gt), and akaganeite (Aka). This set of EXAFS data recorded at cryogenic temperature over a wide energy range allows us to precisely determine the Fe-O mean distance (〈Fe-O〉) in the first coordination shell of iron for this large set of iron (oxyhydr)oxides. Our EXAFS analysis includes both classical shell-by-shell fits of Fourier-filtered and unfiltered data as well as analysis of Fe-O distance distribution in the first coordination shell of iron using the Landweber iteration method. 〈Fe-O〉 determined by these complementary EXAFS analyses are similar: 〈Fe-O〉 is shorter in Mh (1.96 ± 0.01 Å) that contains 37.5% of tetrahedral iron, than in Gt (2.01 ± 0.01 Å), Aka (2.00 ± 0.01 Å) and hematite (Hm) (2.01 ± 0.01 Å) that do not contain tetrahedral iron. 〈Fe-O〉 for the five Fh samples investigated (1.97 ± 0.01 Å) was found to be slightly longer than in Mh and significantly shorter than those in Gt, Aka and Hm. This short 〈Fe-O〉 distance in Fh indicates the presence of significant amount of tetrahedrally coordinated iron(III) in all Fh samples studied, which ranges between 20 ± 5% and 30 ± 5% of total iron. In addition, our analysis of Fe-Fe distances observed by EXAFS is consistent with a Keggin-like motif at a local scale (∼5 Å) in the Fh structure. 相似文献
42.
Corinne A. Locke Simon A. Johnson John Cassidy Jeffrey L. Mauk 《Journal of Geochemical Exploration》1999,65(2):91
The Puhipuhi epithermal area, which occurs in a region of graywacke basement partially covered by basalt and lake-bed deposits, is characterized by both large-scale and small-scale geophysical anomalies. Known occurrences of locally intense alteration or silicification are typically associated with strong gravity, resistivity or IP anomalies. Gravity data define a complex negative residual anomaly (up to −50 gu) which has been used to identify and delineate a large area (about 20 km2) of low-density, presumably clay-altered, graywacke basement rocks. This zone, modeled as extending to a few kilometers depth, encompasses, but is more extensive than, the known areas of alteration and has a close spatial association with the basalt cover rocks. Short-wavelength gravity minima and maxima, which indicate that the most intense alteration of the basement rocks occurs below the basalt, correlate, in part, with the inferred location of hydrothermal upflow zones. The control on the location of these zones and their relationship to the location of the basalts is not well known; however, if the basalts acted as a cap rock to the geothermal system, then these areas merit further exploration. High (≥100 ohm-m) and low (≤10 ohm-m) resistivity and high (≥30 mS) IP anomalies occur in association with known silicification, clay alteration and sulfide mineralisation, respectively. In addition, magnetic data help constrain the relative timing of hydrothermal alteration and basaltic volcanism and indicate that mineralisation was broadly synchronous with volcanism. 相似文献
43.
Corinne Casiot Marc Leblanc Odile Bruneel Jean-Christian Personné Kouadio Koffi Françoise Elbaz-Poulichet 《Aquatic Geochemistry》2003,9(4):273-290
The distribution of arsenic (As(III), As(V)) and iron (Fe(II), Fe(III)) species was monitored during 1 year in a borehole drilled in the Carnoulès tailings impoundment which contains As-rich pyrite. The concentrations of total As and Fe in subsurface waters exhibited strong variations over one year, which were controlled by dissolved oxygen concentrations. At high oxygen levels, extremely high As (up to 162 mM) and Fe (up to 364 mM) concentrations were reached in the borehole, with the oxidised species predominant. As and Fe concentrations decreased 10-fold under oxygen-deficient conditions, as a result of pH increase and subsequent precipitation of As(V) and Fe(III). From drill core sections, it appeared that at low dissolved oxygen levels, As(III) was primarily released into water by the oxidation of As-rich pyrite in the unsaturated zone. Subsequent As and Fe precipitation was promoted during transport to the saturated zone; this reaction resulted in As enrichments in the sediment below the water table compared to the original content in pyrite, together with the formation of As-rich (up to 35 wt% As) ferruginous material in the unsaturated zone. High amounts of As(V) were released from these secondary phases during leaching experiments with oxygenated acid sulfate-rich waters; this process is believed to contribute to As(V) enrichment in the subsurface waters of the Carnoulès tailings during periods of high dissolved oxygen level. 相似文献
44.
45.
Ca2SiO4 dicalcium silicate has been transformed at high pressure in a diamond-anvil cell (DAC) coupled with a YAG laser heater, in order to study the high-pressure modifications of this compound. Starting material was the olivine form of Ca2SiO4 (γ-polymorph). Several samples have been synthesized at loading pressures of 4.5, 10 and 15 GPa respectively, at room temperature. Other samples have been obtained at pressures ranging between 4.5 and 45 GPa and temperatures estimated to be about 2500 °C. The study of the quenched high pressure and/or high temperature phases has been performed using analytical transmission electron microscopy (ATEM) and X-ray diffraction (XRD). All the polymorphs of Ca2SiO4 usually produced with high temperatures, including α-Ca2SiO4, have been observed in the samples recovered from the high-pressure experiments. The α′-Ca2SiO4 and α-Ca2SiO4 polymorphs have been obtained at ambient conditions for the first time without stabilizing impurities. A new modification of α′-Ca2SiO4 has also been synthesized. Finally, the breakdown at high-pressure and temperature of Ca2SiO4 into CaSiO3 and CaO is reported. 相似文献
46.
Helen A. Williams John Cassidy Corinne A. Locke K. Bernhard Sprli 《Tectonophysics》2006,424(1-2):119-133
Gravity studies have delineated the largest ultramafic massif in New Zealand, embedded within a buried major SW Pacific crustal suture zone. This suture records terrane collision onto the Gondwana margin during the Mesozoic and separates a forearc terrane from an outboard accretionary prism terrane. It can be traced throughout the length of New Zealand as the Junction Magnetic Anomaly and contains the Permian Dun Mountain Ophiolite Belt, which in the South Island of New Zealand is characterized by a string of isolated ultramafic massifs in a sheared matrix of serpentinite and sediment. Our analysis reveals a steep gravity gradient at the suture boundary which is attributed to a newly recognised density contrast (0.1 Mg m− 3) between terranes of the forearc and the accretionary prism. The massif itself is marked by the occurrence of a strong, elongate residual gravity anomaly (+ 120 g.u.) extending 50 km along the suture and coincident with the Junction Magnetic Anomaly. It is modelled, at its southern end, as a dense, 15 km wide source body, extending to at least 6 km in depth. In conjunction with detailed aeromagnetic data, this modeling indicates the presence of a spindle-shaped ultramafic massif, analogous to, but larger than similar bodies found within the Dun Mountain Ophiolite Belt elsewhere. This fabric of sheared serpentinites enclosing ultramafic massifs therefore extends at least the length of New Zealand and probably beyond. In part it may result from accretion of asperities in the subducting plate, but it is also due to disruption of larger ultramafic bodies during subsequent strike-slip motion, which caused the remarkable linearity of the Dun Mountain Belt. Given the common occurrence of the plate tectonic processes involved, it is likely that such structures can be found in other regions around the world using similar geophysical potential field methods. 相似文献
47.
Sbastien Lamontagne Corinne Le Gal La Salle Gary J. Hancock Ian T. Webster Craig T. Simmons Andrew J. Love Julianne James-Smith Anthony J. Smith Jochen Kmpf Howard J. Fallowfield 《Marine Chemistry》2008,109(3-4):318
The input of groundwater-borne nutrients to Adelaide's (South Australia) coastal zone is not well known but could contribute to the ongoing decline of seagrass in the area. As a component of the Adelaide Coastal Waters Study (ACWS), the potential for using the radium quartet (223Ra, 224Ra, 226Ra and 228Ra) and 222Rn to evaluate submarine groundwater discharge (SGD) was evaluated. Potential isotopic signatures for SGD were assessed by sampling groundwater from three regional aquifers potentially contributing SGD to the ACWS area. In addition, intertidal groundwater was sampled at two sand beach sites. In general, the regional groundwaters were enriched in long-lived Ra isotopes (226Ra and 228Ra) and in 222Rn relative to intertidal groundwater. Radium activity (but not 222Rn activity) was positively correlated to salinity in groundwater from one of the regional aquifers and in intertidal groundwater. Radium isotope ratios (223Ra/226Ra, 224Ra/226Ra and 228Ra/226Ra) were less variable than individual Ra isotope activities within potential SGD sources. Recirculated seawater (estimated from the intertidal groundwater samples with seawater-like salinities) also had distinctly higher Ra isotope ratios than the regional groundwaters. The activities for all radioisotopes were relatively low in seawater. The activity of the short-lived 223Ra and 224Ra were highest at the shoreline and declined exponentially with distance offshore. In contrast, 228Ra and 226Ra activities had a weak linear declining trend with distance offshore. Rn-222 activity was at or near background in all seawater samples. The pattern of enrichment in short-lived Ra isotopes and the lack of 222Rn in seawater suggest that seawater recirculation is the main contributor to SGD in the ACWS area. Preliminary modeling of the offshore flux of 228Ra and 226Ra suggest that the SGD flux to the ACWS area ranges between 0.2 and 3 · 10− 3 m3 (m of shoreline)− 1 s− 1. 相似文献
48.
Remy Albrecht Jean Christophe GourryMarie-Odile Simonnot Corinne Leyval 《Journal of Applied Geophysics》2011,75(3):558-564
Several laboratory studies have recently demonstrated the utility of geophysical methods for the investigation of microbial-induced changes over contaminated sites. However, it remains difficult to distinguish the effects due to the new physical properties imparted by microbial processes, to bacterial growth, or to the development of bacterial biofilm. We chose to study the influence of biofilm formation on geophysical response using complex conductivity measurements (0.1-1000 Hz) in phenanthrene-contaminated media. Biotic assays were conducted with two phenanthrene (PHE) degrading bacterial strains: Burkholderia sp (NAH1), which produced biofilm and Stenophomonas maltophilia (MATE10), which did not, and an abiotic control. Results showed that bacterial densities for NAH1 and MATE10 strains continuously increased at the same rate during the experiment. However, the complex conductivity signature showed noticeable differences between the two bacteria, with a phase shift of 50 mrad at 4 Hz for NAH1, which produced biofilm. Biofilm volume was quantified by Scanning Confocal Laser Microscopy (SCLM). Significant correlations were established between phase shift decrease and biofilm volume for NAH1 assays. Results suggest that complex conductivity measurements, specifically phase shift, can be a useful indicator of biofilm formation inside the overall signal of microbial activity on contaminated sites. 相似文献
49.
Ian McKendry Eric Christensen Corinne Schiller Roxanne Vingarzan Anne Marie Macdonald Yimei Li 《大气与海洋》2014,52(3):271-280
At Amphitrite Point, ozone (O3) mixing ratios are observed to drop steadily to 5–15?ppb over a period of 12 hours or less with a frequency approaching one event per week (with highest frequencies occurring in summer and fall). Analysis of 47 such O3 depletion events reveals that low O3 episodes are a predominantly nocturnal phenomenon associated with anticyclonic conditions characterized by light onshore or alongshore winds and an absence of fog and mist. Back-trajectories show air carried to the Amphitrite Point Observatory (APO) during depletion events remains in the marine boundary layer and is not brought to the surface from aloft. There is no strong correlation with other “criteria” pollutants (CO, NOx, SO2, PM2.5) that might be indicative of a mechanism for O3 destruction linked to human, terrestrial, or marine pollutant sources. However, CO2 mixing ratios are observed to increase, coincident with O3 depletion. Together, these results point to a natural marine boundary layer phenomenon in which O3 destruction dominates O3 production and/or replenishment by vertical mixing. While there are several candidate mechanisms, the conditions for O3 depletion (and CO2 buildup) to occur are set by meteorology and, in particular, development of a stable marine boundary layer in which vertical mixing is suppressed. Support for this interpretation is provided by simultaneous increases in CO2 in the stable marine boundary that are indicative of an important role played by marine biogenic processes (respiration). Future research should be directed at elucidating the chemical mechanisms responsible for O3 destruction in the coastal zone, which means that there would be a need for a much broader range of measurements at APO (including halogenated species) as well as offshore measurements of both chemical and marine boundary layer meteorological variables. 相似文献
50.
Jean-Pierre Jolivet Corinne Chanéac David Chiche Sophie Cassaignon Olivier Durupthy Julien Hernandez 《Comptes Rendus Geoscience》2011,343(2-3):113-122
This overview features the chemical background on condensation phenomena of the aluminum cation in aqueous solution. The formation of polycationic molecular clusters and nanosized solid phases of aluminum oxy(hydroxi)des is interpreted with illustrative mechanisms, building a bridge between solution chemistry and solid-state chemistry. The formation of the main structural types of aluminosilicates (zeolites, clays, imogolite) is also illustrated through the aqueous chemistry of aluminum and silicates. 相似文献