全文获取类型
| 收费全文 | 219篇 |
| 免费 | 9篇 |
| 国内免费 | 13篇 |
专业分类
| 测绘学 | 47篇 |
| 大气科学 | 13篇 |
| 地球物理 | 40篇 |
| 地质学 | 37篇 |
| 海洋学 | 40篇 |
| 天文学 | 2篇 |
| 综合类 | 15篇 |
| 自然地理 | 47篇 |
出版年
| 2024年 | 1篇 |
| 2023年 | 2篇 |
| 2022年 | 4篇 |
| 2021年 | 6篇 |
| 2020年 | 10篇 |
| 2019年 | 10篇 |
| 2018年 | 8篇 |
| 2017年 | 8篇 |
| 2016年 | 14篇 |
| 2015年 | 3篇 |
| 2014年 | 12篇 |
| 2013年 | 28篇 |
| 2012年 | 10篇 |
| 2011年 | 14篇 |
| 2010年 | 4篇 |
| 2009年 | 8篇 |
| 2008年 | 8篇 |
| 2007年 | 11篇 |
| 2006年 | 14篇 |
| 2005年 | 7篇 |
| 2004年 | 2篇 |
| 2003年 | 11篇 |
| 2002年 | 8篇 |
| 2001年 | 6篇 |
| 2000年 | 4篇 |
| 1999年 | 3篇 |
| 1998年 | 5篇 |
| 1997年 | 5篇 |
| 1996年 | 3篇 |
| 1995年 | 1篇 |
| 1994年 | 3篇 |
| 1991年 | 2篇 |
| 1990年 | 1篇 |
| 1987年 | 1篇 |
| 1986年 | 1篇 |
| 1985年 | 1篇 |
| 1983年 | 1篇 |
| 1979年 | 1篇 |
排序方式： 共有241条查询结果，搜索用时 15 毫秒
41.
Adequate access to healthy food has become a social issue due to the recent Great Recession and heightened levels of unemployment. Geographers have focused their attention on how to accurately evaluate food access and how to identify and delineate food deserts; that is, low-income neighborhoods where affordable and healthy food is lacking or limited. Findings of recent food access studies are, however, dramatically inconsistent. We argue that spatial scale and the level of aggregation used in constructing food access measures could account for a major portion of the varying results. We draw on an empirical study in the Tucson, Arizona, metropolitan area, to examine how varying geographic scales and aggregation methods affect food access assessment. We also provide an analysis to show how spatial scale and aggregation practices lead to inconsistent conclusions about food access and designation of food deserts. 相似文献
42.
43.
44.
Northern Adriatic Rocky Reef Fishes at Low Winter Temperatures 总被引：1，自引：0，他引：1
Abstract. The behavioural ecology of certain northern Adriatic fishes was observed from January to April at a water temperature of 7–11 o C. The fishes studied here do not migrate to deeper waters. Most of the benthic fishes show a similar distribution over the substrate in winter and in summer; in winter, however, they are very inactive and hide in the substrate. Suprabenthic fishes aggregate in littoral caves where they form dense, inactive, mixed aggregations. Certain hemipelagic and pelagic fishes join to form very dense aggregations at specific sites in the open waters of bays. Littoral predators display high feeding activity at a time when their prey is inactive. I present a hypothesis concerning possible implications of seasonally cyclic environmental temperatures for a sympatric community of non-migrating fishes. 相似文献
45.
46.
47.
中国历史文化研究一直是中国文学研究的热点,大量的研究都是基于文学作品本身或文人个体特征进行,缺乏大数据的支持;历史的发展是大量个体共同驱动的结果,文化地理中众多文人的行为潜在影响着古代文化分布和变迁。本文提出基于文人群体运动行为的位置关联和聚合的大数据分析方法,根据唐宋时期文人的移动足迹数据来论证中国历史上的文化中心城市的变迁。文化地理领域中的3次文化中心转移的观点,是基于3次历史事件驱动的定性推理分析,缺乏有效的古代文化方面的数据支撑。本文力图从数据科学、信息科学和GIS分析角度来审视这一结论。从人文领域已经出版的学术研究著作中采集唐宋时期具有代表性作家的11万条足迹数据,利用GIS的位置关联技术形成足迹图,构建了文人迁徙网络图;并采用空间化的PageRank算法计算出唐宋时期各城市的文化吸引力,直观地呈现出了不同时期文人聚集的中心城市,重塑唐宋文化中心变迁。同时,从定量、地理位置变化和时序角度剖析了中国不同时期城市的文化吸引力的分布和变化。为论证中国文化中心的南北变迁,对唐宋时期的城市文化吸引力聚合,以20年间隔来科学计算出南北文化中心的对比和演变,科学表现文化中心的南北随时间的变化,论证了中国文化中心3次南移的后2次,发现中国文化中心南移的时间早在北宋时期就已完成。 相似文献
48.
Problems related to scale continue to be at the forefront of research in hydrology. Past research into issues of scale has focused mainly on digital elevation model grid size, the appropriate number and size of sub‐areas for subdividing a watershed, parameter transferability between watersheds and appropriate scales for linking hydrological and general circulation models. Much less attention has been given to the effects of scale on the representation of land cover and hydrological model response. Recent studies with respect to changes in land cover and hydrologic response have tended to focus on the issue of land cover maturity and the conversion of land through agricultural and forestry practices. The focus of this study is to examine the impact of the level of detail at which land cover is represented in modelling the hydrological response of Wolf Creek Basin in northwest Canada. A grid‐based land cover map with a spatial resolution of 30 m is coarsened or smoothed using several common grid‐based methods of aggregating categorical data, including: pixel thinning, modal smoothing and modal aggregation. A majority rule method based on polygons is also applied to the 30 m base cover. The SLURP hydrologic model is calibrated for the base cover and used as a reference for comparing simulations for the coarsened or ‘generalized’ land cover maps. Results of the simulations are compared to examine the sensitivity of hydrologic response to generalized land cover information. Comparisons of the SLURP model runs for Wolf Creek suggest that reducing the level of detail of land cover information generally has a limited effect on hydrologic response at the outlet. However, results for averages of water balance components across the basin suggest that the local variability of hydrologic response is affected in general. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
49.
50.
S. H. Luk 《地球表面变化过程与地形》1979,4(3):241-255
This paper describes laboratory testing of 148 samples collected from Southern Alberta for erosion by wash and splash. Rainfall intensity was held constant during these tests. Soil aggregation was the most significant variable explaining soil loss. The significance of other soil properties, such as organic carbon and clay content is variable, depending on the interrelationships among aggregate stability, organic content, and clay content of particular soils. Variations in erodibility of the major soils examined are explained by the resistance of aggregates to compaction and dispersion. Splash detachment and wash transport are the dominant erosion mechanisms in inter-rill areas. 相似文献