全文获取类型
收费全文 | 46篇 |
免费 | 0篇 |
专业分类
地质学 | 46篇 |
出版年
2022年 | 1篇 |
2018年 | 1篇 |
2015年 | 1篇 |
2013年 | 1篇 |
2012年 | 2篇 |
2011年 | 3篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2001年 | 1篇 |
1999年 | 2篇 |
1997年 | 2篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1952年 | 1篇 |
1950年 | 1篇 |
1948年 | 1篇 |
1939年 | 2篇 |
1937年 | 1篇 |
1934年 | 1篇 |
1933年 | 1篇 |
1917年 | 1篇 |
1913年 | 1篇 |
排序方式: 共有46条查询结果,搜索用时 15 毫秒
31.
Peter Stille Anne-Désirée Schmitt François Labolle Marie-Claire Pierret Sophie Gangloff Florian Cobert Eric Lucot Florence Guéguen Laure Brioschi Marc Steinmann François Chabaux 《Comptes Rendus Geoscience》2012,344(5):297-311
The combination of the Sr, Nd and Pb isotope systems, recognized as tracers of sources, with the Ca isotope system, known to reveal biology-related fractionations, allowed us to test the reliability of spruce (Picea abies) growth rings as environmental archives through time (from 1916 to 1983) in a forest ecosystem affected by acid atmospheric deposition. Sr and Pb isotopes have already been applied in former tree-ring studies, whereas the suitability of Nd and Ca isotope systems is checked in the present article. Our Sr and Nd isotope data indicate an evolution in the cation origin with a geogenic origin for the oldest rings and an atmospheric origin for the youngest rings. Ca isotopes show, for their part, an isotopic homogeneity which could be linked to the very low weathering flux of Ca. Since this flux is weak the spruces’ root systems have pumped the Ca mainly from the organic matter-rich top-soil over the past century. In contrast, the annual growth rings studied are not reliable and suitable archives of past Pb pollution. 相似文献
32.
Dorothee Hippler Anne-Désirée Schmitt Nikolaus Gussone Alexander Heuser Peter Stille Anton Eisenhauer Thomas F. Nägler 《Geostandards and Geoanalytical Research》2003,27(1):13-19
A compilation of δ44/40 Ca (δ44/40 Ca) data sets of different calcium reference materials is presented, based on measurements in three different laboratories (Institute of Geological Sciences, Bern; Centre de Géochimie de la Surface, Strasbourg; GEOMAR, Kiel) to support the establishment of a calcium isotope reference standard. Samples include a series of international and internal Ca reference materials, including NIST SRM 915a, seawater, two calcium carbonates and a CaF2 reference sample. The deviations in δ44/40 Ca for selected pairs of reference samples have been defined and are consistent within statistical uncertainties in all three laboratories. Emphasis has been placed on characterising both NIST SRM 915a as an internationally available high purity Ca reference sample and seawater as representative of an important and widely available geological reservoir. The difference between δ44/40 Ca of NIST SRM 915a and seawater is defined as -1.88 O.O4%o (δ44/42 CaNISTSRM915a/Sw = -0.94 0.07%o). The conversion of values referenced to NIST SRM 915a to seawater can be described by the simplified equation δ44/40 CaSa/Sw =δ44/40 CaSa/NIST SRM 915a - 1.88 (δ44/42 CaSa/Sw =δ44/42 CaSa/NIST SRM 915a - 0.94). We propose the use of NIST SRM 915a as general Ca isotope reference standard, with seawater being defined as the major reservoir with respect to oceanographic studies. 相似文献
33.
The magnitude of clamping forces has a significant influence on the estimated ultimate pullout force of a block. The Crawford–Bray equation, which is fundamental in considering clamping forces, is only a function of horizontal stress and block height. Further research to incorporate the influence of induced stress in block stability analysis was considered, but all the previous analytical solutions for analyzing block stability assume a continuum medium to estimate clamping forces and do not allow joint deformations to occur before block movement due to gravity. Assuming a continuous medium to estimate clamping forces leads to an overestimation of block stability and therefore unsafe design. In this paper, an attempt has been made to deepen the understanding of the block failure mechanism and correct the estimated magnitude of clamping forces in a discontinuous medium. A conceptual model is proposed based on the loading–unloading of the block from an in‐situ state to failure. Based on this model, an analytical solution has been developed that calculates clamping forces in a discontinuous medium. The validity and model uncertainty of the solution were checked for different conditions. The new analytical solution is both precise and accurate and can be used as a design tool to estimate block stability. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
34.
The impact of vegetation on fractionation of rare earth elements (REE) during water–rock interaction
P. Stille M. Steinmann M.-C. Pierret F. Gauthier-Lafaye D. Aubert A. Probst D. Viville F. Chabaux 《Journal of Geochemical Exploration》2006,88(1-3):341
Previous studies on waters of a streamlet in the Vosges mountains (eastern France) have shown that Sr and rare earth elements (REE) principally originate from apatite dissolution during weathering. However, stream water REE patterns normalized to apatite are still depleted in light REE (LREE, La–Sm) pointing to the presence of an additional LREE depleting process. Speciation calculations indicate that complexation cannot explain this additional LREE depletion. In contrast, vegetation samples are strongly enriched in LREE compared to water and their Sr and Nd isotopic compositions are comparable with those of apatite and waters. Thus, the preferential LREE uptake by the plants at the root–water–soil (apatite) interface might lead to an additional LREE depletion of the waters in the forested catchment. Mass balance calculations indicate that the yearly LREE uptake by vegetation is comparable with the LREE export by the streamlet and, therefore, might be an important factor controlling the LREE depletion in river waters. 相似文献
35.
François Chabaux Lin Ma Peter Stille Eric Pelt Mathieu Granet Damien Lemarchand Raphael di Chiara Roupert Susan L. Brantley 《Applied Geochemistry》2011
The development of U-series nuclides for investigating weathering processes has been significantly stimulated by the analytical improvement made over the last decades in measuring the 238U series with intermediate half-lives (i.e., 234U–230Th–226Ra). It is proposed in this paper to present principles and methods that are now being developed to determine weathering rates from the study of U-series nuclides in soils and weathering profiles. Mathematical approaches, developed to calculate such rates, are based on some implicit assumptions that are also presented and must be kept in mind if one wants to correctly interpret the obtained ages. 相似文献
36.
Florian Cobert Pascale Bourgeade Pierre-Marie Badot Peter Stille 《Geochimica et cosmochimica acta》2011,75(19):5467-5482
Hydroponic experiments have been performed in order to identify the co-occurring geochemical and biological processes affecting the Ca isotopic compositions within plants. To test the influence of the Ca concentration and pH of the nutritive solution on the Ca isotopic composition of the different plant organs, four experimental conditions were chosen combining two different Ca concentrations (5 and 60 ppm) and two pHs (4 and 6). The study was performed on rapid growing bean plants in order to have a complete growth cycle. Several organs (root, stem, leaf, reproductive) were sampled at two different growth stages (10 days and 6 weeks of culture) and prepared for Ca isotopic measurements.The results allow to identify three Ca isotopic fractionation levels. The first one takes place when Ca enters the lateral roots, during Ca adsorption on cation-exchange binding sites in the apoplasm. The second one takes place when Ca is bound to the polygalacturonic acids (pectins) of the middle lamella of the xylem cell wall. Finally, the last fractionation occurs in the reproductive organs, also caused by cation-exchange processes with pectins. However, the cell wall structures of these organs and/or number of available exchange sites seem to be different to those of the xylem wall. These three physico-chemical fractionation mechanisms allow to enrich the organs in the light 40Ca isotope. The amplitude of the Ca isotopic fractionation within plant organs is highly dependent on the composition of the nutritive solution: low pH (4) and Ca concentrations (5 ppm) have no effect on the biomass increase of the plants but induce smaller fractionation amplitudes compared to those obtained from other experimental conditions. Thus, Ca isotopic signatures of bean plants are controlled by the external nutritive medium. This study highlights the potential of Ca isotopes to be applied in plant physiology (to identify Ca uptake, circulation and storage mechanisms within plants) and in biogeochemistry (to identify Ca recycling, Ca content and pH evolutions in soil solutions through time). 相似文献
37.
We present dissolved load (< 0.45 μm) rare earth element (REE) patterns of small streams from a catchment basin in the Massif Central in order to characterize the individual fractionation stages for the dissolved REE from the source to the catchment outlet. The upper part of the catchment is located on a basalt plateau, followed downstream by deep and narrow valleys with granitic and orthogneissic bedrock. Stream water has basalt-like REE patterns on the basaltic plateau close to the source, followed by a continuous depletion in light REE (La-Sm, LREE) downstream. Strontium and neodymium isotope ratios of stream water demonstrate that the dissolved REE are essentially of basaltic origin, even in the lower, granitic and gneissic part of the catchment. Mixing with gneiss or granite derived REE thus cannot explain the observed evolution of the REE patterns. There seems also to be no link with the calculated speciation of the dissolved REE. In contrast, a correlation between saturation indexes for hematite and La/Yb ratios suggests that REE fractionation is mainly controlled by precipitation of Fe-oxide particles that preferentially remove LREE from solution. 相似文献
38.
Anton Eisenhauer Thomas F. Nägler Peter Stille Jan Kramers Nikolaus Gussone Barbara Bock Jan Fietzke Dorothee Hippler Anne-Désirée Schmitt 《Geostandards and Geoanalytical Research》2004,28(1):149-151
A proposal is made to standardise the reporting of Ca isotope data to the δ44 Ca/40 Ca notation (or δ44 Ca/42Ca) and to adopt NIST SRM 915a as the reference standard. 相似文献
39.
The Rb-Sr and Sm-Nd isotope data emphasize the importance of mantle crust interaction, wall-rock assimilation and fractional crystallization for the generation of the Lugano volcanic rocks. It is suggested that the parental magma generation occurs in hot upwelling asthenosphere in the wedge above a subducting slab. In the lower crust the rising mantle derived melts became strongly modified by crust assimilation and formed andesitic melts. These andesitic melts, rising from this lower crustal region, became additionally modified by fractional crystallization and further assimilation of lower and upper crustal components to form the dacites, rhyolites, granophyres and Mt. OrfanoBaveno granites. The best fit lines to the Rb-Sr and Sm-Nd isotope whole rock data points correspond to ages of 346+/– 2 m.y. and 341+/–40 m.y., respectively. These lines are considered to be pseudo-isochrons and the result of simultaneously running fractional crystallization and wallrock assimilation. The best age estimate of the investigated volcanites is given by a Rb-Sr mineral isochron of 262+/–I m.y.. It dates a single volcanic event of the Permo-Carboniferous magmatism. Since it is suggested, that the calc-alkaline rock sequence has been generated in an Andean type subduction environment, synchronous with the final phase of convergence of Gondwana and Laurasia, the Rb-Sr mineral isochron indicates, that parts of the Proto-Tethys closed later than 262 m.y. ago. The crustal source material of the Irvea and Strona-Ceneri paragneisses, Lugano volcanites and Mt. Orfano-Baveno intrusive rocks may not necessarily be derived from a shield area in Northern Europe or Africa but may come from a Proterozoic European continental lithosphere. 相似文献
40.
The Calcium Isotope Composition of Modern Seawater Determined by Thermal Ionisation Mass Spectrometry 总被引:1,自引:0,他引:1
Anne-Désirée Schmitt Guido Bracke Peter Stille Bernard Kiefel 《Geostandards and Geoanalytical Research》2001,25(2-3):267-275
The Ca isotopic composition of modern seawater has been determined using a 43 Ca-48 Ca double spike, which was calibrated using a 42 Ca/44 Ca seawater ratio of 0.30587 ± 0.00026. This ratio was determined from a total evaporation experiment in which the ion beam was measured from the beginning to the end of the emission. With integration of the peak intensities, the fractionation effects can be minimised, since total evaporation of the reservoir cancels out the effect of vapour enrichment in the light isotopes. This experiment avoids the gravimetric uncertainty inherent in the double spike calibration. This calibration allows the precise redetermination of the seawater isotopic composition of Ca. A mean 40 Ca/44 Ca ratio for two Atlantic water samples of 45.143 (2smean = 0.003) was found. The good reproducibility of the Ca isotope ratios in present seawater and the very strong isotopic homogeneity of Ca in the oceans illustrate the advantage of using seawater as the common standard, with the advantage of decreasing interlaboratory bias. 相似文献