全文获取类型
收费全文 | 99篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 17篇 |
地球物理 | 5篇 |
地质学 | 43篇 |
海洋学 | 13篇 |
天文学 | 12篇 |
自然地理 | 9篇 |
出版年
2020年 | 1篇 |
2019年 | 10篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 5篇 |
2012年 | 8篇 |
2011年 | 9篇 |
2010年 | 6篇 |
2009年 | 2篇 |
2008年 | 5篇 |
2007年 | 2篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1998年 | 3篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1958年 | 1篇 |
1957年 | 2篇 |
1955年 | 1篇 |
1954年 | 1篇 |
1952年 | 1篇 |
1951年 | 2篇 |
1948年 | 1篇 |
排序方式: 共有103条查询结果,搜索用时 15 毫秒
71.
During an early phase of the Last Ice Age (Weichselian, Valdaian), about 90 000 yr ago, an ice sheet formed over the shallow Barents and Kara seas. The ice front advanced on to mainland Russia and blocked the north‐flowing rivers (Yenissei, Ob, Pechora, Dvina and others) that supply most of the freshwater to the Arctic Ocean. The result was that large ice‐dammed lakes were formed between the ice sheet in the north and the continental water divides to the south. Here we present reconstructions and calculations of the areas and volumes of these lakes. The lake on the West Siberian Plain was nearly twice as large as the largest lake on Earth today. The well‐mapped Lake Komi in northeast Europe and a postulated lake in the White Sea Basin would also rank before the present‐day third largest lake. The lakes overflowed towards the south and thus the drainage of much of the Eurasian continent was reversed. The result was a major change in the water balance on the continent, decreased freshwater supply to the Arctic Ocean, and increased freshwater flow to the Aral, Caspian, Black and Baltic seas. A sudden outburst of the lakes' water to the Arctic Ocean when the ice sheet thinned is postulated. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
72.
73.
74.
Tomas Crols Roger White Inge Uljee Guy Engelen Lien Poelmans Frank Canters 《International journal of geographical information science》2013,27(10):1757-1781
Urban growth and population growth are used in numerous models to determine their potential impacts on both the natural and the socio-economic systems. Cellular automata (CA) land-use models became popular for urban growth modelling since they predict spatial interactions between different land uses in an explicit and straightforward manner. A common deficiency of land-use models is that they only deal with abstract categories, while in reality, several activities are often hosted at one location (e.g. population, employment, agricultural yield, nature…). Recently, a multiple activity-based variable grid CA model was proposed to represent several urban activities (population and economic activities) within single model cells. The distance-decay influence rules of the model included both short- and long-distance interactions, but all distances between cells were simply Euclidean distances. The geometry of the real transportation system, as well as its interrelations with the evolving activities, were therefore not taken into account. To improve this particular model, we make the influence rules functions of time travelled on the transportation system. Specifically, the new algorithm computes and stores all travel times needed for the variable grid CA. This approach provides fast run times, and it has a higher resolution and more easily modified parameters than the alternative approach of coupling the activity-based CA model to an external transportation model. This paper presents results from one Euclidean scenario and four different transport network scenarios to show the effects on land-use and activity change in an application to Belgium. The approach can add value to urban scenario analysis and the development of transport- and activity-related spatial indicators, and constitutes a general improvement of the activity-based CA model. 相似文献
75.
Edward L. King Hans Petter Sejrup Haflidi Haflidason Anders Elverhi Inge Aarseth 《Marine Geology》1996,130(3-4):293-315
Approximately 1000 km of high resolution sleeve-gun array transects on the North Sea Fan, located at the mouth of the Norwegian Channel, reveal three dominant styles of sedimentation within a thick (> 900 m) Quaternary sediment wedge comprising numerous sequences. These are interpreted as: terrigenous hemipelagic sedimentation, large scale translational slides, and aprons of glaciogenic debris flow deposits contributing to considerable fan construction. Four large, buried translational slides involved sediment volumes upwards of 3000 km3 each and preceded the similarly dimensioned “first” Storegga Slide on the NE fan flank. Several thick (> 100 m) terrigenous hemipelagic deposits apparently represent long-lived (150–200 kyr) periods of sedimentation whose distribution indicates fan input via the Norwegian Channel. The upper sequences are each made upper sequences are each made up of one or several thick (> 100 m) aprons comprising stacked lensoid and/or lobate forms which range from 2 to 40 km in width and 15 to 60 m in thickness. They characterize debris flows attributed to periodic input from several phases of a Norwegian Channel ice stream reaching the shelf edge. Subsidence in the outer Norwegian Channel allowed preservation of several glaciation cycles represented by sheet erosion-bounded tills and progradational units. Much of the shelf/slope transition has been preserved, allowing a preliminary chronology of the fan sequences through correlation with borehole sediments in the Norwegian Channel. Debris flows, which signal the initial shelf-edge glaciation, are not recognized from the initial glaciation in the Channel (> 1.1 Myr) but are associated with a Middle Pleistocene and all following glacial erosion surfaces (GES) in the outer Norwegian Channel. This was followed by six further sequences, probably totalling over 13,000 km3 of sediment. At least four of these were shelf-edge ice-maximum events the last of which was Late Weichselian age (14C AMS). Considering earlier glaciation-related hemipelagic sedimentation, material since removed by the large slides, and extensive unmapped areas, total Quaternary fan sedimentation was in the vicinity of 20,000 km3. 相似文献
76.
Dieu Tien Bui Tran Anh Tuan Harald Klempe Biswajeet Pradhan Inge Revhaug 《Landslides》2016,13(2):361-378
Preparation of landslide susceptibility maps is considered as the first important step in landslide risk assessments, but these maps are accepted as an end product that can be used for land use planning. The main objective of this study is to explore some new state-of-the-art sophisticated machine learning techniques and introduce a framework for training and validation of shallow landslide susceptibility models by using the latest statistical methods. The Son La hydropower basin (Vietnam) was selected as a case study. First, a landslide inventory map was constructed using the historical landslide locations from two national projects in Vietnam. A total of 12 landslide conditioning factors were then constructed from various data sources. Landslide locations were randomly split into a ratio of 70:30 for training and validating the models. To choose the best subset of conditioning factors, predictive ability of the factors were assessed using the Information Gain Ratio with 10-fold cross-validation technique. Factors with null predictive ability were removed to optimize the models. Subsequently, five landslide models were built using support vector machines (SVM), multi-layer perceptron neural networks (MLP Neural Nets), radial basis function neural networks (RBF Neural Nets), kernel logistic regression (KLR), and logistic model trees (LMT). The resulting models were validated and compared using the receive operating characteristic (ROC), Kappa index, and several statistical evaluation measures. Additionally, Friedman and Wilcoxon signed-rank tests were applied to confirm significant statistical differences among the five machine learning models employed in this study. Overall, the MLP Neural Nets model has the highest prediction capability (90.2 %), followed by the SVM model (88.7 %) and the KLR model (87.9 %), the RBF Neural Nets model (87.1 %), and the LMT model (86.1 %). Results revealed that both the KLR and the LMT models showed promising methods for shallow landslide susceptibility mapping. The result from this study demonstrates the benefit of selecting the optimal machine learning techniques with proper conditioning selection method in shallow landslide susceptibility mapping. 相似文献
77.
78.
The climate history of western Spitsbergen, Svalbard is deduced from variations of glaciers during the last 20 000 years. A major depression of the regional equilibrium line altitude (ELA) occurred during the Late Weichselian glacial maximum (18000–13000y ago) when low summer temperatures may have caused year-round snow accumulation on the ground. This rapid expansion of the glaciers also indicates nearby moisture sources, suggesting partly open conditions in the Norwegian Sea during the summers. A rapid glacial retreat around 13 000–12 500 y BP was caused by a sudden warming. During the Younger Dryas the ELA along the extreme western coast of Spitsbergen was not significantly lower than at present. In contrast to Fennoscandia, the British Isles and the Alps, there is no evidence for readvance of local glaciers during Younger Dryas on western Spitsbergen. This difference is attributed to a much dryer climate on Spitsbergen and probably only slight changes in sea surface temperatures. In addition, summer melting in this high arctic area is more sensitive to orbitally increased insolation. Around 10 000 y BP another rapid warming occurred and during early and mid Holocene the summer temperatures were significantly higher than at present. A temperature decline during the late Holocene caused regrowth of the glaciers which reached their maximum Holocene position during the last century.Contribution to Clima Locarno — Past and Present Climate Dynamics; Conference September 1990, Swiss Academy of Sciences — National Climate Program 相似文献
79.
80.