全文获取类型
收费全文 | 273篇 |
免费 | 17篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 19篇 |
地球物理 | 73篇 |
地质学 | 92篇 |
海洋学 | 32篇 |
天文学 | 32篇 |
自然地理 | 38篇 |
出版年
2024年 | 2篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 7篇 |
2017年 | 5篇 |
2016年 | 13篇 |
2015年 | 4篇 |
2014年 | 13篇 |
2013年 | 21篇 |
2012年 | 21篇 |
2011年 | 32篇 |
2010年 | 26篇 |
2009年 | 22篇 |
2008年 | 8篇 |
2007年 | 13篇 |
2006年 | 9篇 |
2005年 | 14篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1996年 | 1篇 |
1994年 | 5篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1979年 | 1篇 |
1973年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有293条查询结果,搜索用时 15 毫秒
31.
Determination of Rare Earth Elements, Sc, Y, Zr, Ba, Hf and Th in Geological Samples by ICP-MS after Tm Addition and Alkaline Fusion 总被引:2,自引:0,他引:2
Germain Bayon Jean Alix Barrat Joël Etoubleau Mathieu Benoit Claire Bollinger Sidonie Révillon 《Geostandards and Geoanalytical Research》2009,33(1):51-62
We present a revised method for the determination of concentrations of rare earth (REE) and other trace elements (Y, Sc, Zr, Ba, Hf, Th) in geological samples. Our analytical procedure involves sample digestion using alkaline fusion (NaOH-Na2 O2 ) after addition of a Tm spike, co-precipitation on iron hydroxides, and measurement by sector field-inductively coupled plasma-mass spectrometry (SF-ICP-MS). The procedure was tested successfully for various rock types (i.e., basalt, ultramafic rock, sediment, soil, granite), including rocks with low trace element abundances (sub ng g−1 ). Results obtained for a series of nine geological reference materials (BIR-1, BCR-2, UB-N, JP-1, AC-E, MA-N, MAG-1, GSMS-2, GSS-4) are in reasonable agreement with published working values. 相似文献
32.
Jean-Alix Barrat Akira Yamaguchi Claire Bollinger Marcel Bohn 《Geochimica et cosmochimica acta》2010,74(21):6218-6231
The eucrites and diogenites are meteorites that probably originate from asteroid 4-Vesta. The upper part of the crust of this body is certainly composed of eucrites which are basaltic or gabbroic rocks. Diogenites are ultramafic cumulates whose relationships with eucritic lithologies are unknown. Here, we show that the orthopyroxenes of some diogenites display very deep negative Eu anomalies (Eu/Eu∗ close to 0.1 or lower). The contamination of the parental magmas of diogenites by melts derived by partial melting of the eucritic crust can satisfactorily explain the range of the Eu anomalies displayed by diogenites. Thus, these anomalies are the first firm indication that parental melts of diogenites have intruded the eucritic crust, and consequently are younger than eucrites. 相似文献
33.
Stephen J. Eaton David M. Hodgson Natasha L. M. Barlow Estelle E. J. Mortimer Claire L. Mellett 《第四纪科学杂志》2020,35(6):760-775
Offshore stratigraphic records from the North Sea contain information to reconstruct palaeo-ice-sheet extent and understand sedimentary processes and landscape response to Pleistocene glacial–interglacial cycles. We document three major Middle to Late Pleistocene stratigraphic packages over a 401-km2 area (Norfolk Vanguard/Boreas Offshore Wind Farm), offshore East Anglia, UK, through the integration of 2D seismic, borehole and cone penetration test data. The lowermost unit is predominantly fluviatile [Yarmouth Roads Formation, Marine Isotope Stage (MIS) 19–13], including three northward-draining valleys. The middle unit (Swarte Bank Formation) records the southernmost extent of tunnel valley-fills in this area of the North Sea, providing evidence for subglacial conditions most likely during the Anglian stage (MIS 12) glaciation. The Yarmouth Roads and Swarte Bank deposits are truncated and overlain by low-energy estuarine silts and clays (Brown Bank Formation; MIS 5d–4). Smaller scale features, including dune-scale bedforms, and abrupt changes in cone penetration test parameters, provide evidence for episodic changes in relative sea level within MIS 5. The landscape evolution recorded in deposits of ~MIS 19–5 are strongly related to glacial–interglacial cycles, although a distinctive aspect of this low-relief ice-marginal setting are opposing sediment transport directions under contrasting sedimentary process regimes. 相似文献
34.
Andreas Günther Paola Reichenbach Jean-Philippe Malet Miet Van Den Eeckhaut Javier Hervás Claire Dashwood Fausto Guzzetti 《Landslides》2013,10(5):529-546
In the framework of the European Soil Thematic Strategy and the associated proposal of a Framework Directive on the protection and sustainable use of soil, landslides were recognised as a soil threat requiring specific strategies for priority area identification, spatial hazard assessment and management. This contribution outlines the general specifications for nested, Tier-based geographical landslide zonings at small spatial scales to identify priority areas susceptible to landslides (Tier 1) and to perform quantitative susceptibility evaluations within these (Tier 2). A heuristic, synoptic-scale Tier 1 assessment exploiting a reduced set of geoenvironmental factors derived from common pan-European data sources is proposed for the European Union and adjacent countries. Evaluation of the susceptibility estimate with national-level landslide inventory data suggests that a zonation of Europe according to, e.g. morphology and climate, and performing separate susceptibility assessments per zone could give more reliable results. To improve the Tier 1 assessment, a geomorphological terrain zoning and landslide typology differentiation are then applied for France. A multivariate landslide susceptibility assessment using additional information on landslide conditioning and triggering factors, together with a historical catalogue of landslides, is proposed for Tier 2 analysis. An approach is tested for priority areas in Italy using small administrative mapping units, allowing for relating socioeconomic census data with landslide susceptibility, which is mandatory for decision making regarding the adoption of landslide prevention and mitigation measures. The paper concludes with recommendations on further work to harmonise European landslide susceptibility assessments in the context of the European Soil Thematic Strategy. 相似文献
35.
Anouska Panton Claire Mahaffey Naomi Greenwood Joanne Hopkins David Montagnes Jonathan Sharples 《Ocean Dynamics》2012,62(2):295-306
Regions of freshwater influence (ROFIs) are dynamic areas within the coastal seas that experience cycles of stability driven
by density gradients and the spring-neap tidal cycle. As a result, pulses of biological production may occur on a more frequent
timescale than the classic seasonal cycle. Net community production (NCP) rates and chlorophyll a concentration are presented from a site within the ROFI of Liverpool Bay and compared to similar measurements made at a site
outside the ROFI during 2009. The influence of water column stability on biological production in the ROFI was also investigated
using high-frequency observations from a Cefas Smartbuoy. Both sites were autotrophic from spring to autumn before becoming
heterotrophic over winter. NCP at the inshore site was estimated to range from 30.8 to 50.4 gC m−2 year−1. A linear relationship detected between chlorophyll a and NCP from both sites was used to estimate metabolic balance over 1 year at the ROFI site using high-resolution chlorophyll
a concentrations from the Smartbuoy but was found to poorly replicate NCP rates compared to those derived from dissolved oxygen
fluxes. There was no clear biological response to periods of stratification within the ROFI, and it is proposed that changes
in light attenuation in the Liverpool Bay ROFI, driven not only by stratification but also by fluctuations in riverine sediment
load, most likely play an important role in controlling phytoplankton growth in this region. 相似文献
36.
Determining sediment provenance allows a better understanding of fluvial palaeo-dynamics, and identifying involved watersheds, at broad spatio-temporal scales. Conventional approaches for source identification are usually based on the physical, mineralogical, geochemical, magnetic or isotopic properties of sediments. Rapid, non-destructive and, in well-established contexts, highly accurate, mid-infrared spectroscopy is an alternative method for investigating sediment sources. The present research objectives are: (i) to use the mid-infrared spectroscopy method to discriminate the provenance of fine sediments, by applying discriminant analysis on a large set of reference samples from three different watersheds in the Upper Rhine area (associated with the Rhine, Ill and Vosges tributaries); (ii) to clarify whether the provenance spectra signatures are influenced by riverine depositional contexts (bars versus banks) and, to some extent, by grain size and/or high organic matter content; and (iii) to apply the mid-infrared spectroscopy – discriminant analysis method to a study of fluvial palaeo-dynamics and determine the provenance of palaeo-channel infillings. Three main sedimentary sources, divided into eight sub-categories, have been characterized by 196 modern reference samples from 78 collecting sites. Discriminant analysis displayed a strong separating power by classifying correctly the origin of samples without any inter-group overlap, independently from the geomorphological context (bar or bank) and associated slight changes in organic matter contents or grain size. Mid-infrared spectroscopy – discriminant analysis investigations of the palaeo-channel infill, complemented by radiocarbon dates and mineralogical data, allowed reconstructing general trends for the local morpho-sedimentary dynamics over the last ca 12 millennia. 相似文献
37.
Claire E. Lazareth Nury Guzman Frederic Candaudap 《Geochimica et cosmochimica acta》2007,71(22):5369-5383
Mollusk shells are increasingly used as records of past environmental conditions, particularly for sea-surface temperature (SST) reconstructions. Many recent studies tackled SST (and/or sea-surface salinity) tracers through variations in the elementary (Mg and Sr) or stable isotope (δ18O) composition within mollusk shells. But such attempts, which sometimes include calibration studies on modern specimens, are not always conclusive. We present here a series of Mg and Sr analyses in the calcitic layer of Concholepas concholepas (Muricidae, Gastropoda) with a very high time-resolution on a time window covering about 1 and a half month of shell formation, performed by Laser Ablation Inductively-Coupled Plasma Mass Spectrometry (LA-ICP-MS) and electron probe micro-analysis (EPMA). The selected specimen of this common Chilean gastropod was grown under controlled environmental conditions and precise weekly time-marks were imprinted in the shell with calcein staining. Strontium variations in the shell are too limited to be interpreted in terms of environmental parameter changes. In contrast, Mg incorporation into the shell and growth rate appear to change systematically between night and day. During the day, Mg is incorporated at a higher rate than at night and this intake seems positively correlated with water temperature. The nightly reduced Mg incorporation is seemingly related to metabolically controlled processes, formation of organic-rich shell increments and nocturnal feeding activity of the animals. The nyctemeral Mg changes in the C. concholepas shell revealed in this study might explain at least part of the discrepancies observed in previous studies on the use of Mg as a SST proxy in mollusk shells. In the case of C. concholepas, Mg cannot be used straightforwardly as a SST proxy. 相似文献
38.
Sedimentological analyses of 289 years (AD 1718-2006) of varved sediment from Shadow Bay, southwest Alaska, were used to investigate hydroclimate variability during and prior to the instrumental period. Varve thicknesses relate most strongly to total annual discharge (r2 = 0.75, n = 43, p < 0.0001). Maximum annual grain size depends most strongly on maximum spring daily discharge (r2 = 0.63, n = 43, p < 0.0001) and maximum annual daily discharge (r2 = 0.61, n = 43, p < 0.0001), while varve thickness is poorly correlated with maximum annual grain size (r2 = 0.004, n = 287, p = 0.33). Relations between varve thickness and annual climate variables (temperature, precipitation, North Pacific (NP) and Pacific Decadal Oscillation (PDO) indices) are insignificant. On multidecadal timescales, however, regime shifts in varve thickness and total annual discharge coincide with shifts in NP and PDO indices. Periods with increased varve thickness and total annual discharge were associated with warm PDO phases and a strengthened Aleutian Low. The varve-inferred record of PDO suggests that any periodicity in the PDO varied over time, and that the early 19th century marked a transition to a more frequent or detectable shifts. 相似文献
39.
Abstract: Landslide research at the British Geological Survey (BGS) is carried out through a number of activities, including surveying, database development and real-time monitoring of landslides. Landslide mapping across the UK has been carried out since BGS started geological mapping in 1835. Today, BGS geologists use a combination of remote sensing and ground-based investigations to survey landslides. The development of waterproof tablet computers (BGS·SIGMAmobile), with inbuilt GPS and GIS for field data capture provides an accurate and rapid mapping methodology for field surveys. Regional and national mapping of landslides is carried out in conjunction with site-specific monitoring, using terrestrial LiDAR and differential GPS technologies, which BGS has successfully developed for this application. In addition to surface monitoring, BGS is currently developing geophysical ground-imaging systems for landslide monitoring, which provide real-time information on subsurface changes prior to failure events. BGS’s mapping and monitoring activities directly feed into the BGS National Landslide Database, the most extensive source of information on landslides in Great Britain. It currently holds over 14?000 records of landslide events. By combining BGS’s corporate datasets with expert knowledge, BGS has developed a landslide hazard assessment tool, GeoSure, which provides information on the relative landslide hazard susceptibility at national scale. 相似文献
40.