全文获取类型
收费全文 | 62篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 11篇 |
地球物理 | 10篇 |
地质学 | 21篇 |
海洋学 | 14篇 |
天文学 | 4篇 |
自然地理 | 2篇 |
出版年
2023年 | 2篇 |
2021年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 6篇 |
2015年 | 2篇 |
2013年 | 10篇 |
2012年 | 3篇 |
2011年 | 5篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2008年 | 3篇 |
2007年 | 1篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1994年 | 3篇 |
1990年 | 2篇 |
1980年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1962年 | 1篇 |
1885年 | 1篇 |
排序方式: 共有66条查询结果,搜索用时 46 毫秒
1.
2.
Jacco C. Kromkamp Edward P. Morris Rodney M. Forster Claire Honeywill Scott Hagerthey David M. Paterson 《Estuaries and Coasts》2006,29(2):183-196
Estimating biomass of microphytobenthos (MPB) on intertidal mud flats is extremely difficult due to their patchy occurrence,
especially at the scale of an entire mud flat. We tested two optical approaches that can be applied in situ: spectral reflectance
and chlorophyll fluorescence. These two approaches were applied in 4 European estuaries with different sediment characteristics.
At each site, paired replicate measurements of hyperspectral reflectance, chlorophyll fluorescence (after 15 min dark adaptation,
Fo
15), sediment water content, and chlorophylla concentrations were taken (including breakdown products: [chla+phaeo]). Sediments were further characterized by grain size and organic content analysis. The spectral signatures of tidal
flats dominated by benthic microalgae, mainly diatoms, could be easily distinguished from sites dominated by macrophytes;
we present a 3 waveband algorithm that can be used to detect the presence of macrophytes. The normalized difference vegetation
index (NDVI) was found to be most strongly correlated to sediment [chla+phaeo], except for the predominantly sandy Sylt stations. Fo
15 was also significantly correlated to sediment [chla+phaeo] in all but one grid (Sylt grid A). Our results suggest that the functional relationships (i.e., the slopes) between
NDVI or fluorescence and [chla+ phaeo] were not significantly different in the muddier grids, although the intercepts could differ significantly, especially
for Fo
15. This suggests a mismatch of the optical depth seen by the reflectometer or fluorometer and the depth sampled for pigment
analysis. NDVI appears to be a robust proxy for sediment [chla+phaeo] and can be used to quantify MPB biomass in muddy sediments of mid latitude estuaries. 相似文献
3.
Until recently, bryozoans have not been used as indicators for changes in bottom communities or climate control in the North Sea Basin, despite a 200-year history of bryozoan collecting. The epizoobiontic bryozoan fauna of Flustra foliacea (Linnaeus, 1758) was analysed on 51 sample stations kept in four German museums. The samples cover the entire North Sea and different time periods (1776–2008, mainly the period of 1904/1905 compared to 1980–87). Cluster analysis shows a differentiation into a northern and a southern North Sea assemblage. The northern assemblage is characterized by Amphiblestrum flemingii (Busk, 1854), Callopora dumerilii (Audouin, 1826) and Tricellaria ternata (Ellis & Solander, 1786), while the southern North Sea is characterized by Electra pilosa (Linnaeus, 1767), Crisia eburnea (Linnaeus, 1758) and Plagioecia patina (Lamarck, 1816). Spatial separation approximately follows the 50 m depth contour. The temporal distribution patterns of bryozoans are discussed in terms of NAO (North Atlantic Oscillation) and temperature variations. 相似文献
4.
PM Ross RM Fairweather DP Culliford S Park CA Pilditch CN Battershill 《新西兰海洋与淡水研究杂志》2016,50(1):56-69
ABSTRACTTo investigate the uptake and depuration of polycyclic aromatic hydrocarbons associated with the Rena oil spill we sampled the surf clam Paphies subtriangulata at two open coast locations (6?km apart) just prior to oil coming ashore (7 October 2011), then at 1–3 week intervals for the next 4 months. Total polycyclic aromatic hydrocarbons (tPAH) increased at both sites from 1 to 96–124?µg?kg?1 (wet weight) by 18 October before declining to low levels (<4?µg?kg?1) by February 2012. Ongoing sampling throughout 2012–2014 included three additional sites to the north east (up to 30?km away) and a site 5?km to the south east revealing tPAH levels generally <10?µg?kg?1 except in October 2013 where levels ranged between 39–45?µg?kg?1 at all sites. A comparison of PAH component profiles with oil-contaminated beach sediment indicated that the high levels observed in surf clams between October–December 2011 were clearly associated with the Rena spill. However, the October 2013 peak had a PAH profile inconsistent with weathered Rena oil, suggesting an alternative source of contamination. Our results highlight the potential for P. subtriangulata as a PAH monitoring tool but recognise more study is needed to better quantify baseline levels and uptake and depuration dynamics. 相似文献
5.
赣南地区石雷石英闪长岩的成因:岩石化学、副矿物微量元素、锆石U-Pb年代学与Sr-Nd-Hf同位素制约 总被引:5,自引:2,他引:3
石雷石英闪长岩是赣南崇-余-犹地区比较特殊的闪长质侵入体。锆石的原位U-Pb定年表明,该岩体侵位于433.5±3.4Ma。全岩主量元素特征上显示出中偏酸性(SiO2=56.92%~64.70%),富Al(Al2O3=14.10%~14.83%),富碱(Alk=6.41%~7.40%)特别是富钾(K2O=3.86%~4.85%),镁、铁含量较高,MgO:3.47%~5.95%,FeOT:5.23%~8.14%以及低磷(P2O5=0.27%~0.4%)的特点;微量元素上主要富集K、Rb、Cs等大离子亲石元素和轻稀土元素,亏损Nb、Ta、Ti、P等高场强元素。磷灰石微量元素特征上显示高度富集稀土元素特别是轻稀土元素的特征;具有Eu的负异常(δEu=0.37~0.45)。ISr位于0.7073~0.7132之间,εNd(t)变化于-8.41~-4.97之间,两阶段钕模式年龄介于1.58~1.86Ga之间,Hf同位素组成相对均一,εHf(t)主要集中变化于-8~-2之间,两阶段Hf模式年龄加权平均为1.77±0.09Ga,这些特征都暗示了该石英闪长质岩体的形成是强烈壳幔相互作用的产物,区内加里东晚期可能发生了局部的岩石圈的减薄。 相似文献
6.
7.
The impact of rain and spray on the ocean disturbs the sea surface and generates underwater ambient noise. The short scale roughness is influenced by impacting drops due to the momentum transfer. Radar and sonar signals are scattered by the short elements of the sea surface. Spray and rain impact change their characteristics, and consequently affect radar and sonar backscatter. In situ measurements of rain and spray impact are necessary to study their effects on the sea surface. Accurate sea measurements of rain momentum fluxes and drop size distributions are a complex problem, especially on buoys. A new measuring technique has been developed using hydrophones. Exposed to precipitation, these instruments are affected directly by the impact of rain. A drop falling on the hydrophone deforms its surface and is sensed by a piezoelectric transducer. The voltage output of the sensor is a rapidly decaying oscillation. The integral value of this signal is a measure of the drop momentum, and the drop size can be deduced. Laboratory studies of defined drops as well as field measurements of natural rain have shown that hydrophones can be used to determine drop momentums and drop size distributions. Based on simultaneous rain measurements by a Joss-Waldvogel Disdrometer and a hydrophone, an analytical function has been derived which relates drop size and hydrophone voltage output 相似文献
8.
Johanna Forster Peter W. Schuhmann Iain R. Lake Andrew R. Watkinson Jennifer A. Gill 《Climatic change》2012,114(3-4):745-768
Climate change could have major implications for the global tourism industry if changing environmental conditions alter the attractiveness of holiday destinations. Countries with economies dependent on tourism and with tourism industries reliant on vulnerable natural resources are likely to be particularly at risk. We investigate the implications that climate-induced variations in Atlantic hurricane activity may have for the tourism-dependent Caribbean island of Anguilla. Three hundred tourists completed standardised questionnaires and participated in a choice experiment to determine the influence hurricane risk has on their risk perceptions and decisions regarding holiday preferences. The hurricane season had been considered by 40?% of respondents when making their holiday choice, and the beaches, climate and tranquility of the island were more important than coral reef-based recreational activities in determining holiday destination choice. Choice models demonstrated that respondents were significantly less likely to choose holiday options where hurricane risk is perceived to increase, and significantly more likely to choose options that offered financial compensation for increased risk. However, these choices and decisions varied among demographic groups, with older visitors, Americans, and people who prioritize beach-based activities tending to be most concerned about hurricanes. These groups comprise a significant component of the island’s current clientele, suggesting that perceived increases in hurricane risk may have important implications for the tourism economy of Anguilla and similar destinations. Improved protection of key environmental features (e.g. beaches) may be necessary to enhance resilience to potential future climate impacts. 相似文献
9.
10.
Darkness on the Edge of Town: Mapping Urban and Peri-Urban Australia Using Nighttime Satellite Imagery 总被引:1,自引:1,他引:0
Paul C. Sutton Andrew R. Goetz Stephen Fildes Clive Forster Tilottama Ghosh 《The Professional geographer》2013,65(1):119-133
This article explores the use of nighttime satellite imagery for mapping urban and peri-urban areas of Australia. A population-weighted measure of urban sprawl is used to characterize relative levels of sprawl for Australia's urban areas. In addition, the expansive areas of low light surrounding most major metropolitan areas are used to map the urban–bush interface of exurban land use. Our findings suggest that 82 percent of the Australian population lives in urban areas, 15 percent live in peri-urban or exurban areas, and 3 percent live in rural areas. This represents a significantly more concentrated human settlement pattern than presently exists in the United States. 相似文献