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241.
242.
黄海夏季水域沉降颗粒物垂直通量的研究 总被引:13,自引:1,他引:12
20 0 2年 8月 ,沿穿过黄海冷水团的青岛至济州岛断面 ,在 4个站位放置沉积物捕获器采集沉降颗粒物。镜检发现无机颗粒物、生物粪球以及混杂聚合体是本断面沉降颗粒物主要类型。测定结果显示沉降颗粒物中的颗粒有机碳 (POC)、颗粒有机氮 (PON)、颗粒碳 (PC)、颗粒氮 (PN)和颗粒磷 (PP)的百分含量均呈现从表层到底层逐渐下降的趋势。采用两个改进的模型对底层颗粒物再悬浮比率进行了计算 ,显示黄海海域夏季底层沉降颗粒物再悬浮比率为 90 %— 96%,表明底层沉降颗粒物主要来源于沉积物的再悬浮。两模型所得结果一致 ,证明用温跃层底部颗粒物沉降通量代表水体中颗粒物净沉降通量的假设是合理的。水体中颗粒物、POC及PON的净沉降通量 (±SE)分别为 ( 1 2 65± 3 5 5 )g/(m2 ·d)、( 0 2 9± 0 0 4 )g/(m2 ·d)和( 0 0 6± 0 0 1 )g/(m2 ·d)。 相似文献
243.
Anthropogenic threats to cold-water coral reefs are trawling and hydrocarbon drilling, with both activities causing increased levels of suspended particles. The efficiency of Lophelia pertusa in rejecting local sediments and drill cuttings from the coral surface was evaluated and found not to differ between sediment types. Further results showed that the coral efficiently removed deposited material even after repeated exposures, indicating an efficient cleaning mechanism. In an experiment focusing on burial, fine-fraction drill cuttings were deposited on corals over time. Drill cutting covered coral area increased with repeated depositions, with accumulation mainly occurring on and adjacent to regions of the coral skeleton lacking tissue cover. Tissue was smothered and polyp mortality occurred where polyps became wholly covered by material. Burial of coral by drill cuttings to the current threshold level used in environmental risk assessment models by the offshore industry (6.3 mm) may result in damage to L. pertusa colonies. 相似文献
244.
http://www.sciencedirect.com/science/article/pii/S1674987111001095 总被引:11,自引:2,他引:9
During the Late Mesozoic Middle Jurassic-Late Cretaceous,basin and range tectonics and associated magmatism representative of an extensional tectonic setting was widespread in southeastern China as a r... 相似文献
245.
246.
Mercury contamination of active channel sediment and floodplain deposits from historic gold mining at Gold Hill,North Carolina,USA 总被引:2,自引:1,他引:1
A reconnaissance investigation of mercury contamination associated with historic gold mining in North Carolina, USA, revealed
high concentrations of mercury in channel and floodplain sediments downstream from the Gold Hill mining district. The most
intense period of mining activities in this region occurred in the 1840s and 1850s when mercury amalgamation was used to recover
fine gold particles from milled ore. This paper evaluates mercury concentrations measured in active channel sediments and
two cores recovered from historic floodplain deposits of the lower portion of Dutch Buffalo Creek. Mercury concentrations
in these cores range from 0.01 to 2.2 mg/kg, with maximum concentrations more than 35 times background levels. A later peak
in copper concentrations is associated with the operation of a large copper mine between 1899 and 1906. Following the most
intense periods of mining, both mercury and copper concentrations decrease upcore to constant levels of about twice pre-mining
background concentrations. Results suggest that vertical trends in mercury and other trace metals provide a useful tool for
interpreting rates of historic floodplain sedimentation in the Piedmont of North Carolina. 相似文献
247.
云南文山麻栗坡新寨锡矿成矿条件分析 总被引:3,自引:0,他引:3
早加里东期拗陷区沉积形成矿源层,晚加里东一印支期区域变质作用、混合岩化作用使锡质初步富集,后期热液叠加淬取使成矿元素得以重新活化转移到热液中,成为含矿热液(矿浆),运移到适当部位聚集形成工业锡矿体。 相似文献
248.
Based upon the analysis of about 10,000 line km of echosounding and bathymetric data and variations in mass accumulation rate along the NW continental margin of India (between Kori creek and Mumbai), we have deduced that in the northern region (in the vicinity of the River Indus) the shelf-break occurs at a shallower depth and the slope is shallower, has the steepest gradient (<1:20), is smoother with no major features, and has reduced width (slope edge at 1450 m; width 19 km than off Mumbai). The width and depth of the slope edge gradually increases southwards, and is at maximum off DamanMumbai (slope edge depth 2900 m; width 84 km). The intensity of the occurrence of physiographic features also increases southwards. The shelf edge off Saurashtra is undulating and on the slope, regional notches and benches (the most prominent at 560 m) are observed. Further southwards off Khambhat-Mumbai, the slope is characterized by the presence of bathymetric highs and lows. We have also observed numerous features on the shelf, with a variable depth of the shelf-break. The gradient of the continental slope is also reduced from the northern region to the southern region. The variations in the gradient of the slope and the presence of distinct physiographic features in this area are examined vis-a-vis fluvial supply of the sediments into the region. 相似文献
249.
V.N.Golosov 《国际泥沙研究》1996,(2)
SOMEAPPROACHESFORSTUDYINGTHEINTENSITYOFSMALLRIVERAGGRADATIONV.N.Golosov(LaboratoryofSoilandFluvialProcesses,FacultyofGeograph... 相似文献
250.