全文获取类型
收费全文 | 139篇 |
免费 | 12篇 |
国内免费 | 3篇 |
学科分类
地球科学 | 154篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2021年 | 10篇 |
2020年 | 2篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 9篇 |
2013年 | 8篇 |
2012年 | 8篇 |
2011年 | 13篇 |
2010年 | 4篇 |
2009年 | 12篇 |
2008年 | 10篇 |
2007年 | 6篇 |
2006年 | 4篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1987年 | 2篇 |
1978年 | 3篇 |
1974年 | 1篇 |
排序方式: 共有154条查询结果,搜索用时 31 毫秒
41.
C.A. Alfonso P.E. Sacks D.T. Secor J. Rine V. Perez 《Journal of South American Earth Sciences》1994,7(3-4)
Surface geology and heophysical data, supplemented by regional structural interpretations, indicate that the Valle del Cauca basin and adjacent areas in west-central Colombia form a west-vergent, basement-involved fold and thrust belt. This belt is part of a Cenozoic orogen developed along the west side of the Romeral fault system. Structural analysis and geometrical constraints show that the Mesozoic ophiolitic basement and its Cenozoic sedimentary cover are involved in a “thick-skinned” west-vergent foreland style deformation. The rocks are transported and shortened by deeply rooted thrust faults and stacked in imbricate fashion. The faults have a NE---SW regional trend, are listric in shape, developed as splay faults which are interpreted as joining a common detachment at over 10 km depth. The faults carry Paleogene sedimentary strata and Cretaceous basement rocks westward over Miocene strata of the Valle del Cauca Basin. Fold axes trend parallel or sub parallel to the thrust faults. The folds are westwardly asymmetrical with parallel to kink geometry, and are interpreted to be fault-propagation folds stacked in an imbricate thrust system. Stratigraphic evidence suggests that the Valle del Cauca basin was deformed between Oligocene and upper Miocene time. The kinematic history outlined above is consistent with an oblique convergence between the Panama and South American plates during the Cenozoic.A negative residual Bouguer anomaly of 20–70 mgls in the central part of the Valle del Cauca basin indicates that a substantial volume of low density sedimentary rocks is concealed beneath the thrust sheets exposed at the land surface. The hydrocarbon potential of the Valle del Cauca should be reevaluated in light of the structural interpretations presented in this paper. 相似文献
42.
R. Alvarez J. Perez Reynoso L. Javier Alvarez M. Lopez Martinez 《Bulletin of Volcanology》1978,41(4):317-327
The conductivity of four igneous rocks with, 49, 65, 77, and 84% SiO2 was measured as a function of temperature in the interval from 20° to 1280°C; measurements were made in a vacuum of 10?3 torr. No simple relationships were found between conductivity and SiO2 content or versus major element groupings such as Na2O=K2O=CaO and TiO2=Cr2O3=Al2O3=Fe2O3=FeO. An analytical expression was obtained between conductivity and the albite-quartz ratio, valid for temperatures between 300° and 1200°C. It was necessary to compute the CIPW norm in order to obtain the albite and quartz percentages. The onset of melting apparently occurred between 600° and 700°C. Petrography performed on two samples after cooling showed 70 and 85% partial melting. Three conduction regions were identified: 1) below 300°C, 2) between 300°C and 600°C, and 3) above 600°C. Different activation energies obtained for the heating and cooling intervals confirm that the sample undergoes textural changes in the heating-cooling cycle. Activation energy increments of 0.1 and 0.2 eV per decade of albite-quartz ratio were obtained. 相似文献
43.
The present paper reports recent improvements in sealed tube combustion technique used for the determination of N isotopic composition in various rocks characterized by low N contents (i.e. few ppm). Nitrogen is extracted from samples by combustion in quartz tubes sealed under vacuum. The nitrogen gas purified using Cu, CuO and CaO, is quantified as dinitrogen N2 by capacitance manometry in ultra-high vacuum line. Nitrogen isotopic analysis is performed on a triple-collector static vacuum mass spectrometer, allowing measurement of nanomole quantity of N2. Nitrogen amount and isotopic composition of the analytical blanks are low and describe Gaussian distribution with mean values of 0.65 ± 0.30 nmol N and − 3.7‰ ± 2.7‰, respectively (2σ). Systematic analyses of international and internal standards demonstrate that this technique provides accurate and precise results. The precision on N content and isotopic composition are better than ± 8% and ± 0.5‰ respectively, even for samples containing less than 2 ppm N. The sealed tube combustion technique is shown to apply successfully to rocks of various lithologies such as metagabbros, metaperidotites and altered basalts. It is thus suitable for studying oceanic crust in a perspective to better constrain N exchanges between Earth mantle and surface reservoirs. The investigation can also be extended to analysis of small size samples, particularly when little sample exists and when high spatial resolution is required. 相似文献
44.
Sebastien Delmotte Filip J.R. Meysman Alain Boudou Magali Gerino 《Geochimica et cosmochimica acta》2007,71(4):844-862
Biogeochemistry of metals in aquatic sediments is strongly influenced by bioturbation. To determine the effects of biological transport on cadmium distribution in freshwater sediments, a bioturbation model is explored that describes the conveyor-belt feeding of tubificid oligochaetes. A stepwise modelling strategy was adopted to constrain the many parameters of the model: (i) the tubificid transport model was first calibrated on four sets of microspheres (inert solid tracer) profiles to constrain tubificid transport; (ii) the resulting transport coefficients were subsequently applied to simulate the distribution of both particulate and dissolved cadmium. Firstly, these simulations provide quantitative insight into the mechanism of tubificid bioturbation. Values of transport coefficients compare very well with the literature, and based on this, a generic model of tubificid bioturbation is proposed. Secondly, the application of the model to cadmium dataset sheds a light on the behaviour of cadmium under tubificid bioturbation. Cadmium enters the sediment in two ways. In one pathway, cadmium enters the sediment in the dissolved phase, is rapidly absorbed onto solid particles, which are then rapidly transported to depth by the tubificids. In the other pathway, cadmium is adsorbed to particles in suspension in the overlying water, which then settle on the sediment surface, and are transported downwards by bioturbation. In a final step, we assessed the optimal model complexity for the present dataset. To this end, the two-phase conveyor-belt model was compared to two simplified versions. A solid phase-only conveyor-belt model also provides good results: the dissolved phase should not be explicitly incorporated because cadmium adsorption is fast and bioirrigation is weak. Yet, a solid phase-only biodiffusive model does not perform adequately, as it does not mechanistically capture the conveyor-belt transport at short time-scales. 相似文献
45.
46.
Carlos Roberto de Souza Filho Alfredo Rossetto Nunes Emilson Pereira Leite Lena Virgínia Soares Monteiro Roberto Perez Xavier 《Surveys in Geophysics》2007,28(5-6):377-405
The Serra Leste region, located in the northeast portion of Carajás Mineral Province (PA), hosts important chrome-PGE, Au–Pd–Pt,
Cu–Mo–Au, iron, and manganese deposits and occurrences related to different geological settings. We present a regional prospective
model with focus on PGE mineralizations based on airborne geophysics (magnetometry, gamma-ray spectrometry and time domain
electromagnetometry) and geological data. Geological and geophysics data analysis indicate a plausible correspondence between
areas with meta-mafic–ultramafic rocks and low values in gamma spectrometry, mainly for the thorium channel. The meta-ultramafic
units of the complexes, the main host rock of the PGE mineralization, are well defined by analytic signal from the anomalous
magnetic field and by the apparent conductance anomalies derived from the GEOTEM system. The combination of the derivative
products with updated geological data of the Serra Leste region and PGE-Luanga deposit enable to establish a regional prospective
model for PGE and the identification of new targets within the studied area. 相似文献
47.
48.
Jorge Perez Melisa Menendez Fernando J. Mendez Inigo J. Losada 《Climate Dynamics》2014,43(9-10):2663-2680
One of the main sources of uncertainty in estimating climate projections affected by global warming is the choice of the global climate model (GCM). The aim of this study is to evaluate the skill of GCMs from CMIP3 and CMIP5 databases in the north-east Atlantic Ocean region. It is well known that the seasonal and interannual variability of surface inland variables (e.g. precipitation and snow) and ocean variables (e.g. wave height and storm surge) are linked to the atmospheric circulation patterns. Thus, an automatic synoptic classification, based on weather types, has been used to assess whether GCMs are able to reproduce spatial patterns and climate variability. Three important factors have been analyzed: the skill of GCMs to reproduce the synoptic situations, the skill of GCMs to reproduce the historical inter-annual variability and the consistency of GCMs experiments during twenty-first century projections. The results of this analysis indicate that the most skilled GCMs in the study region are UKMO-HadGEM2, ECHAM5/MPI-OM and MIROC3.2(hires) for CMIP3 scenarios and ACCESS1.0, EC-EARTH, HadGEM2-CC, HadGEM2-ES and CMCC-CM for CMIP5 scenarios. These models are therefore recommended for the estimation of future regional multi-model projections of surface variables driven by the atmospheric circulation in the north-east Atlantic Ocean region. 相似文献
49.
Magali Fabre Christophe Lcuyer Jean-Philip Brugal Romain Amiot Franois Fourel Franois Martineau 《Quaternary Research》2011,75(3):605-613
Oxygen isotope compositions of phosphate in tooth enamel from large mammals (i.e. horse and red deer) were measured to quantify past mean annual air temperatures and seasonal variations between 145 ka and 33 ka in eastern France. The method is based on interdependent relationships between the δ18O of apatite phosphate, environmental waters and air temperatures. Horse (Equus caballus germanicus) and red deer (Cervus elaphus) remains have δ18O values that range from 14.2‰ to 17.2‰, indicating mean air temperatures between 7°C and 13°C. Oxygen isotope time series obtained from two of the six horse teeth show a sinusoidal-like signal that could have been forced by temperature variations of seasonal origin. Intra-tooth oxygen isotope variations reveal that at 145 ka, winters were colder (? 7 ± 2°C) than at present (3 ± 1°C) while summer temperatures were similar. Winter temperatures mark a well-developed West–East thermal gradient in France of about ? 9°C, much stronger than the ?4°C difference recorded presently. Negative winter temperatures were likely responsible for the extent and duration of the snow cover, thus limiting the food resources available for large ungulates with repercussions for Neanderthal predators. 相似文献
50.
Vronique Lavastre Magali Ader Stphane Buschaert Eddy Petit Marc Javoy 《Applied Geochemistry》2011,26(5):818-827
Upper Dogger to Oxfordian Formations in the eastern part of the Paris basin (France) are currently being investigated by the French nuclear waste management agency (Andra), testing the feasibility of long-term deep nuclear waste disposal in the Callovo-Oxfordian claystones. Characterising the hydrogeological behaviour of the Callovo-Oxfordian claystones is, therefore, essential in evaluating its potential as a geological barrier. In order to evaluate and quantify water/rock interactions experienced over geological time by these Formations, bulk carbonate δ13C and δ18O were measured and calculations of water-rock ratios were used to explain carbonate-δ18O changes. Meteoric porewater and a maximum temperature reached of about 40 °C were considered. The Jurassic marine carbonate δ13C was preserved in the Callovo-Oxfordian claystones and in the overlying limestones (−0.28‰ to 3.39‰/PDB), while the δ18O values are lower by 0-5‰ (−6.25‰ to −1.32‰/PDB). Calculations show that Upper Dogger and Oxfordian Limestone δ18O data:
- (i)
- have random-like distribution through theoretical δ18O-W/R curves and
- (ii)
- suggest that water/rock ratios (0.08-0.4) needed to explain δ18O changes are higher by a factor of about 2-20 compared to the present-day water/rock ratio.