全文获取类型
收费全文 | 461篇 |
免费 | 14篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 44篇 |
地球物理 | 21篇 |
地质学 | 279篇 |
海洋学 | 24篇 |
天文学 | 5篇 |
自然地理 | 97篇 |
出版年
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 8篇 |
2013年 | 26篇 |
2012年 | 7篇 |
2011年 | 14篇 |
2010年 | 11篇 |
2009年 | 17篇 |
2008年 | 13篇 |
2007年 | 16篇 |
2006年 | 11篇 |
2005年 | 22篇 |
2004年 | 15篇 |
2003年 | 14篇 |
2002年 | 5篇 |
2001年 | 7篇 |
2000年 | 10篇 |
1999年 | 12篇 |
1998年 | 17篇 |
1997年 | 35篇 |
1996年 | 26篇 |
1995年 | 12篇 |
1994年 | 20篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 16篇 |
1990年 | 20篇 |
1989年 | 10篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1963年 | 3篇 |
1962年 | 1篇 |
排序方式: 共有477条查询结果,搜索用时 437 毫秒
211.
212.
213.
CORNELIA WINGUTH DAVID M. MICKELSON EILIV LARSEN JESSICA R. DARTER CAROLYN A. MOELLER KNUT STALSBERG 《Boreas: An International Journal of Quaternary Research》2005,34(2):176-185
Winguth, C., Mickelson, D. M., Larsen, E., Darter, J. R., Moeller, C. A. & Stalsberg, K. 2005 (May): Thickness evolution of the Scandinavian Ice Sheet during the Late Weichselian in Nordfjord, western Norway: evidence from ice-flow modeling. Boreas , Vol. 34, pp. 176–185. Oslo. ISSN 0300–9483.
Results from experiments with a two-dimensional ice-flow model, applied along a west-east transect in western Norway, provide new constraints on the thickness evolution of the Scandinavian Ice Sheet throughout the Late Weichselian glaciation and deglaciation. Investigations took place along an E-W flowline of the former ice sheet at c. 62N, from the modern glacier Jostedalsbreen, through the Nordfjord, and across the continental shelf. A paleoclimate record from Kråkenes, which is located directly at the flowline, provides temperature and precipitation information for the time between 13 800 and 9200 cal. yr BP. LGM climate conditions for the study area are estimated from various GCM studies. The GISP2 δ18 O record has been tuned to the local data in order to provide a continuous temperature record as input for time-transgressive model runs. The results of all experiments suggest that the ice did not cover the highest mountain peaks in this area, and that nunataks persisted throughout the Late Weichselian glaciation. These findings are in contrast to results from many previous model studies and other ice-sheet reconstructions, but agree well with minimum thickness estimates from cosmogenic dating and with vertical ice limits inferred from lower block field boundaries and trimlines. 相似文献
Results from experiments with a two-dimensional ice-flow model, applied along a west-east transect in western Norway, provide new constraints on the thickness evolution of the Scandinavian Ice Sheet throughout the Late Weichselian glaciation and deglaciation. Investigations took place along an E-W flowline of the former ice sheet at c. 62N, from the modern glacier Jostedalsbreen, through the Nordfjord, and across the continental shelf. A paleoclimate record from Kråkenes, which is located directly at the flowline, provides temperature and precipitation information for the time between 13 800 and 9200 cal. yr BP. LGM climate conditions for the study area are estimated from various GCM studies. The GISP2 δ
214.
215.
216.
217.
218.
219.
Current views on the internal structure of many glacial landforms need further definition. For example, drumlinized Halton till plain near the Scarborough Bluffs, Ontario would traditionally be. viewed as a lodgement till sheet, but it was found to consist of complex sedimentary assemblages including sediment flows, melt-out, deformation and lodgement tills. These facies vary spatially depending on whether deposition occurred beneath grounded ice or within subglacial cavities. Proglacial sediments bury portions of the till plain. Surface Rutings and drumlins clearly indicate the action of subglacial processes on the surface of Halton drift. Sedimentary structures at the contact between stratified sediments and diamictons within the Late Wisconsinan Halton drift are similar to those in older beds exposed at Scarborough Bluffs. The demonstration of the role of grounded ice in Halton drift and the similarity of sedimentary structures to those of the underlying Thorncliffe and Sunnybrook sediments suggests that the action of grounded ice cannot be ruled out in the case of the lower beds, as has been done by Eyles & Eyles ( Geology 11 , 146–152, 1983). Thus, surface Halton drift may be a model for recognition of similar environments of deposition in older beds beneath Halton. This analysis indicates flaws in a recent re-evaluation of Scarborough Bluffs sediment interpreted as solely lacustrine and not directly affected by glaciers. 相似文献
220.
DAVID MITCHELL 《International journal of geographical information science》2013,27(2):255-256
Studies on the structural properties of road network and its close relationship with the traffic flow distribution have received intensive interdisciplinary attention. However, most of these attempts were theoretical. It is also a challenge to understand the relationship between the structure and morphology of a road network and peoples' movement. We developed a new methodology to deal with this challenge in this study. The first attempt was to apply the ego network analysis (which is rooted in social science) to the formation of hierarchical road networks. Then, the ego network was improved to become weighted ego network by assigning a weight to each of the links in a network. A measure called weighted average centrality rank is developed to define the order of links in a complex network. The ego network and the weighted ego network are both evaluated with a notional network and two sets of real-life road networks. Traffic flow data were used as a benchmark for the evaluation of the two approaches. The results show that they both perform well. But the hierarchies formed by weighted ego network analysis are more consistent with the real-life traffic flow, and the improvement is clearly observable. 相似文献