全文获取类型
收费全文 | 52篇 |
免费 | 2篇 |
专业分类
测绘学 | 1篇 |
地球物理 | 17篇 |
地质学 | 16篇 |
海洋学 | 6篇 |
天文学 | 11篇 |
自然地理 | 3篇 |
出版年
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 3篇 |
2012年 | 2篇 |
2011年 | 2篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2008年 | 4篇 |
2007年 | 4篇 |
2006年 | 2篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有54条查询结果,搜索用时 15 毫秒
31.
In semi‐arid areas, high‐intensity rainfall events are often held responsible for the main part of soil erosion. Long‐term landscape evolution models usually use average annual rainfall as input, making the evaluation of single events impossible. Event‐based soil erosion models are better suited for this purpose but cannot be used to simulate longer timescales and are usually applied to plots or small catchments. In this study, the openLISEM event‐based erosion model was applied to the medium‐sized (~50 km2) Prado catchment in SE Spain. Our aim was to (i) test the model's performance for medium‐sized catchments, (ii) test the ability to simulate four selected typical Mediterranean rainfall events of different magnitude and (iii) explore the relative contribution of these different storms to soil erosion using scenarios of future climate variability. Results show that because of large differences in the hydrologic response between storms of different magnitudes, each event needed to be calibrated separately. The relation between rainfall event characteristics and the calibration factors might help in determining optimal calibration values if event characteristics are known. Calibration of the model features some drawbacks for large catchments due to spatial variability in Ksat values. Scenario calculations show that although ~50% of soil erosion occurs as a result of high frequency, low‐intensity rainfall events, large‐magnitude, low‐frequency events potentially contribute significantly to total soil erosion. The results illustrate the need to incorporate temporal variability in rainfall magnitude–frequency distributions in landscape evolution models. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
32.
33.
Achim?KopfEmail author Annette?Deyhle Vasili?Y.?Lavrushin Boris?G.?Polyak Joris?M.?Gieskes Guram?I.?Buachidze Klaus?Wallmann Anton?Eisenhauer 《International Journal of Earth Sciences》2003,92(3):407-425
The Caucasian orogenic wedge formed as a consequence of the closure of the Tethyan Ocean, and numerous fields of active mud volcanoes pepper the area adjacent to the Black and Caspian Seas. Stable isotope ratios of boron, helium, and carbon have been measured for gas, fluid and sediment samples from active mud volcanoes of Taman Peninsula and Georgia to estimate the sources and mobilization depths of the fluid phase and mud. Boron concentrations in mud volcano fluids were found to be 5–35× higher than seawater. Fluid isotope ratios vary between 11B=22 and 39, while isotope ratios of the smectite- and illite-rich extruded mud are considerably depleted in heavy 11B (11B=–8 to +7). B contents of these muds are ~8× higher than modern marine sediments. This suggests that liquefaction prior to mud volcanism was accompanied by both B enrichment and isotope fractionation, most likely at an intermediate depth mud reservoir at 2–4 km.The hydrocarbon-generating source beds to the mud volcanoes are located at 7 to >10 km depth in the folded Maikop Formation and are of proposed Oligocene–Miocene age. The most likely mechanism is re-hydration of these shales by both hydrocarbons and a geochemically mature fluid from greater depth within the orogenic wedge. Such a deep fluid source is supported by our results from gas analyses, which imply an admixture of minor amounts (less than 1%vol) of 3He (Georgia), thermogenic 13C in methane as well as "ultraheavy" 13C in CO2 (both Taman and Georgia). The overall results attest active local flow of geochemically different fluids along deep-seated faults penetrating the two study areas in the Caucasian orogenic wedge, with the waters as well as the gases coming from below the Maikop Formation. 相似文献
34.
35.
Angela Boley Joris Mergaert Claude Muller Henning Lebrenz Margo C. Cnockaert Wolf‐Rüdiger Müller Jean Swings 《洁净——土壤、空气、水》2003,31(3):195-203
A combination of denitrification and pesticide sorption with the biodegradable polymer poly(?‐caprolactone) (PCL) was examined. The function of PCL is to act as carbon source and carrier for the bacteria and simultaneously as sorbent for the pesticide endosulfan. In a short‐term examination (1 month) the addition of the pesticide endosulfan to a continuous‐flow fixed‐bed reactor resulted in an inhibition of biomass production without reduction of the denitrification performance. However in a long‐term semi‐batch reactor test (6 months) biomass production and partly denitrification rates were affected. No significant differences in microbial composition between the reactors were observed. Regardless of the type of reactor or presence of endosulfan, Acidovorax facilis was the main constituent. 相似文献
36.
37.
Environmental chemicals may modulate the endocrine system through interaction with plasma sex steroid-binding proteins (SBP) and SBP-regulated processes. Some of these chemicals, which are known to interact with the estrogen receptor (ER), were found to bind competitively to the Atlantic salmon (Salmo salar) SBP and potentially disrupt the endocrine function of these proteins. Furthermore, both weakly acting (di-n-butyl phthalate) and potent estrogen mimics (ethynylestradiol), were able to induce a substantial up-regulation of circulating levels of SBP in vivo. Interestingly, modulation of SBP-levels was found to be a more sensitive endpoint than chemically induced interference with classical ER-mediated mechanisms for weakly acting estrogen mimics like di-(n-butyl) phthalate. Interference with the endocrine function of SBPs may thus introduce a novel mechanism for endocrine disruption. and give additional answers to the question why some weakly acting xenoestrogens are causing "estrogen-like" reproductive disturbances in developing males. 相似文献
38.
The exchange flow of water and sediment between a harbor and the surrounding waters can be geometrically decomposed into three main components: tidal filling, horizontal, and vertical exchange flows. The method is applied to analyze available measurements at two important harbor basins in Belgium. The geometric analysis can also be applied to the results of a numerical model of hydrodynamics and sediment transport, provided it has sufficient horizontal, vertical, and temporal resolutions to capture the dynamics at the harbor mouth. As such, it can be used as a tool in model calibration. The presented method can provide some insight into the complex relationship (phasing and spatial correlations) between hydrodynamics and sediment concentration that determines harbor siltation. 相似文献
39.
The stratigraphic record and processes of turbidity current transformation across deep‐marine lobes
下载免费PDF全文
![点击此处可从《Sedimentology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ian A. Kane Anna S. M. Pontén Brita Vangdal Joris T. Eggenhuisen David M. Hodgson Yvonne T. Spychala 《Sedimentology》2017,64(5):1236-1273
Sedimentary facies in the distal parts of deep‐marine lobes can diverge significantly from those predicted by classical turbidite models, and sedimentological processes in these environments are poorly understood. This gap may be bridged using outcrop studies and theoretical models. In the Skoorsteenberg Formation (South Africa), a downstream transition from thickly bedded turbidite sandstones to argillaceous, internally layered hybrid beds, is observed. The hybrid beds have a characteristic stratigraphic and spatial distribution, being associated with bed successions which generally coarsen and thicken‐upward reflecting deposition on the fringes of lobes in a dominantly progradational system. Using a detailed characterization of bed types, including grain size, grain‐fabric and mineralogical analyses, a process‐model for flow evolution is developed. This is explored using a numerical suspension capacity model for radially spreading and decelerating turbidity currents. The new model shows how decelerating sediment suspensions can reach a critical suspension capacity threshold beyond which grains are not supported by fluid turbulence. Sand and silt particles, settling together with flocculated clay, may form low yield strength cohesive flows; development of these higher concentration lower boundary layer flows inhibits transfer of turbulent kinetic energy into the upper parts of the flow ultimately resulting in catastrophic loss of turbulence and collapse of the upper part of the flow. Advection distances of the now transitional to laminar flow are relatively long (several kilometres) suggesting relatively slow dewatering (several hours) of the low yield strength flows. The catastrophic loss of turbulence accounts for the presence of such beds in other fine‐grained systems without invoking external controls or large‐scale flow partitioning and also explains the abrupt pinch‐out of all divisions of these sandstones. Estimation of the point of flow transformation is a useful tool in the prediction of heterogeneity distribution in subsurface systems. 相似文献
40.
Daphne van der Wal Thijs van Kessel Marieke A. Eleveld Joris Vanlede 《Ocean Dynamics》2010,60(3):519-533
The fate of mud in an estuary over an entire year was unravelled using complementary, independent, spatially explicit techniques.
Sequential ERS-2 SAR and Envisat MERIS-FR data were used to derive synoptic changes in intertidal bottom mud and suspended
particulate matter (SPM) in the top of the water column, respectively. These satellite data were combined with in situ measurements
and with a high resolution three-dimensional cohesive sediment model, simulating mud transport, resuspension, settling and
deposition under the influence of tides, wind, waves and freshwater discharge. The spatial distribution of both bottom mud
and SPM as observed by in situ and satellite techniques was largely explained by modelled estuarine circulation, tidal and
wind-induced variations in vertical mixing and horizontal advection. The three data sources also showed similar spring-neap
and seasonal variations in SPM (all factor 1.5 to 2), but semi-diurnal tidal variations were underestimated by the model.
Satellite data revealed that changes in intertidal bottom mud were spatially heterogeneous, but on average mud content doubled
during summer, which was confirmed by in situ data. The model did not show such seasonal variation in bed sediment, suggesting
that seasonal dynamics are not well explained by the physical factors presently implemented in the model, but may be largely
attributed to other (internal) factors, including increased floc size in summer, temporal stabilisation of the sediment by
microphytobenthos and a substantially lower roughness of the intertidal bed in summer as observed by the satellite. The effects
of such factors on estuarine mud dynamics were evaluated. 相似文献