全文获取类型
收费全文 | 207篇 |
免费 | 17篇 |
国内免费 | 14篇 |
专业分类
测绘学 | 92篇 |
大气科学 | 8篇 |
地球物理 | 15篇 |
地质学 | 70篇 |
海洋学 | 7篇 |
综合类 | 15篇 |
自然地理 | 31篇 |
出版年
2022年 | 1篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 11篇 |
2015年 | 14篇 |
2014年 | 16篇 |
2013年 | 19篇 |
2012年 | 17篇 |
2011年 | 25篇 |
2010年 | 15篇 |
2009年 | 22篇 |
2008年 | 25篇 |
2007年 | 20篇 |
2006年 | 5篇 |
2005年 | 15篇 |
2004年 | 10篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 1篇 |
排序方式: 共有238条查询结果,搜索用时 31 毫秒
231.
232.
Sources and implications of particulate organic matter from a small tropical river—Zuari River,India
Fernandes Dearlyn Wu Ying Shirodkar Prabhaker Vasant Pradhan Umesh Kumar Zhang Jing 《海洋学报(英文版)》2020,39(4):18-32
Transitional ecosystems,estuaries and the coastal seas,are distinctively affected by natural and anthropogenic factors.Organic matter(OM)originating from terrestrial sources is exported by rivers and forms a key component of the global biogeochemical cycles.Most previous studies focused on the bulk biochemical and anthropogenic aspects affecting these ecosystems.In the present study,we examined the sources and fate of OM entrained within suspended particulate matter(SPM)of the Zuari River and its estuary,west coast of India.Besides using amino acid(AA)enantiomers(L-and D-forms)as biomarkers,other bulk biochemical parameters viz.particulate organic carbon(POC),δ13C,particulate nitrogen(PN),δ15N and chlorophyll a were analyzed.Surprisingly no significant temporal variations were observed in the parameters analyzed;nonetheless,salinity,POC,δ13C,PN,δ15N,glutamic acid,serine,alanine,tyrosine,leucine and D-aspartic acid exhibited significant spatial variability suggesting source differentiation.The POC content displayed weak temporal variability with low values observed during the post-monsoon season attributed to inputs from mixed sources.Estuarine samples were less depleted than the riverine samples suggesting contributions from marine plankton in addition to contributions from river plankton and terrestrial C3 plants detritus.Labile OM was observed during the monsoon and post-monsoon seasons in the estuarine region.More degraded OM was noticed during the pre-monsoon season.Principal component analysis was used to ascertain the sources and factors influencing OM.Principally five factors were extracted explaining 84.52%of the total variance.The first component accounted for 27.10%of the variance suggesting the dominance of tidal influence whereas,the second component accounted for heterotrophic bacteria and their remnants associated with the particulate matter,contributing primarily to the AA pool.Based on this study we ascertained the role of the estuarine turbidity maximum(ETM)controlling the sources of POM and its implications to small tropical rivers.Thus,changes in temporal and regional settings are more likely to affect the natural biogeochemical cycles of small tropical rivers. 相似文献
233.
基于遥感的长沙市城市热岛与土地利用/覆盖变化研究 总被引:9,自引:0,他引:9
基于多时相Landsat TM/ETM+影像,首先计算长沙市地表亮度温度,然后利用NDVI(归一化植被指数)、MNDWI(改进
的归一化水体指数)、NDBI(归一化建筑指数)和NDBaI(归一化裸土指数)4个指数,采用决策树分类方法对长沙市影像进行
土地利用/覆盖分类。在此基础上,对长沙市城市热岛的空间分布特征、时空演变特征以及城市热岛与土地利用/覆盖变化和各种影
响因子之间的关系进行研究。结果表明,随着长沙市城区范围的不断扩张,城市热岛范围也不断增大; 土地利用/覆盖类型的变化
会改变地表温度的空间分布,城市用地和裸地是城市热岛强度的主要贡献因素,水体和林地具有较好的降温作用。地表温度与4种
归一化指数的回归分析表明,它们之间存在明显的相关性,不同土地利用/覆盖类型的地表温度存在较大差异。 相似文献
234.
基于MODIS数据的Landsat-7 SLC-off影像修复方法研究 总被引:2,自引:0,他引:2
研究如何修复由于扫描行校正器SLC故障而造成的数据坏行,成为国际遥感研究的热点.文章在总结现有的修复方法基础上提出用相同时相的MODIS09数据修复SLC-off数据的方法.该方法采用时空自适应反射率融合模型(STARFM)算法实现MODIS09数据和TM/ETM+数据的融合,获得与SLC-off数据相同时相和空间分辨率的融合数据,然后采用局部线性直方图匹配完成对SLC-off数据填充.实验证明该方法修复效果明显好于传统方法,解决了传统修复方法中存在的一些问题,一定程度上提高了ETM+SLC-off数据的利用率. 相似文献
235.
236.
237.
Glacier Extent and Volume Change (1966-9000) on the Su-lo Mountain in Northeastern Tibetan Plateau,China 总被引:2,自引:2,他引:0
The topographic maps of 1:50, 000 scales, aerial photographs taken in 1966, one Landsat image taken in 1999, and SRTM data from 2000 were used to quantify the losses in area and volume of the glaciers on the Su-lo Mountain, in the northeastern Tibetan Plateau, China in the past 30 years. The total glacier area decreased from 492.9 km^2 in 1966 to 458.2 km^2 in 1999. The volume loss of the studied glaciers reached 1.4 km^3 from 1966 to 2000. This agrees with documented changes in other mountain glaciers of the whole Tibetan Plateau. 相似文献
238.