全文获取类型
收费全文 | 93篇 |
免费 | 2篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 5篇 |
地球物理 | 18篇 |
地质学 | 36篇 |
海洋学 | 10篇 |
天文学 | 16篇 |
综合类 | 1篇 |
自然地理 | 13篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 4篇 |
2013年 | 6篇 |
2012年 | 3篇 |
2011年 | 5篇 |
2009年 | 8篇 |
2008年 | 4篇 |
2007年 | 5篇 |
2006年 | 2篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1955年 | 1篇 |
1924年 | 1篇 |
1910年 | 2篇 |
1905年 | 2篇 |
1897年 | 1篇 |
排序方式: 共有99条查询结果,搜索用时 953 毫秒
81.
Physical modelling experiments have been carried out in a cold room to test on a small scale, the effects of water supply during the thaw of an experimental slope with permafrost. Permafrost was maintained at depth and a thin active layer was frozen and thawed from the surface. Data from the experiments relate to two different conditions, first with moderate rainfall, and second with heavy rainfall during the thaw period. When moderate rainfall is applied during thaw phases, the experimental slope is slightly degraded. At the scale of the experiment, erosion processes involve frost jacking of the coarse blocks, frost creep and gelifluction that induce slow and gradual down slope displacements of the active layer, but also small landslides leading to large but slow mass movements with short displacements. Changes in experimental slope morphology are marked by the initiation of a small‐scale drainage network and the development of a little crest line which shows a progressive upslope migration. With such boundary conditions, there is not enough water supply to evacuate downslope the whole of the eroded material and a topographic smoothing is observed. When heavy rainfall is applied during thaw periods, rapid mass wasting (small mud‐flows and debris flows) become prominent. Slope failures are largely controlled by the water saturation of the active layer and by the occurrence of steeper slopes. At the scale of the experiment, rates of erosion and maximum incision increase by about 100% leading to significant slope degradation with marked and specific scars comparable to gullying. These morphological changes are dependant on both the size and the frequency of catastrophic events. These experiments provide detailed data that could improve the knowledge of the physical parameters that control the initiation, at a small‐scale, of erosion processes on periglacial slopes with a thin active layer and/or with thin cover of mobilizable slope deposits. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
82.
C. B. Jones D. B. Kidner L. Q. Luo G. Ll. Bundy J. M. Ware 《International journal of geographical information science》2013,27(8):901-920
Abstract Growth in the available quantities of digital geographical data has led to major problems in maintaining and integrating data from multiple sources, required by users at differing levels of generalization. Existing GIS and associated database management systems provide few facilities specifically intended for handling spatial data at multiple scales and require time consuming manual intervention to control update and retain consistency between representations. In this paper the GEODYSSEY conceptual design for a multi-scale, multiple representation spatial database is presented and the results of experimental implementation of several aspects of the design are described. Object-oriented, deductive and procedural programming techniques have been applied in several contexts: automated update software, using probabilistic reasoning; deductive query processing using explicit stored semantic and spatial relations combined with geometric data; multiresolution spatial data access methods combining poini, line, area and surface geometry; and triangulation-based generalization software that detects and resolves topological inconsistency. 相似文献
83.
84.
85.
R. I. F. Trindade E. Font M. S. D'Agrella-Filho A. C. R. Nogueira C. Riccomini 《地学学报》2003,15(6):441-446
Palaeomagnetic study of the carbonates that ubiquitously cap glacial deposits may constrain the latitudinal extent of Neoproterozoic glaciations and the duration of the greenhouse recovery. We present the first palaeomagnetic data on the Neoproterozoic cap carbonates covering the Amazon craton, which are folded along the Paraguay Belt. Samples collected at deformed beds along the Paraguay Belt present a single‐polarity secondary magnetization acquired by the end of the Brasiliano orogeny (540–520 Ma). In the cratonic area, a dual‐polarity component was isolated in dolostones at the base of the sequence. The presence of a stratabound reversal stratigraphy along with high unblocking temperatures strongly suggest that this magnetization is primary. This result implies a low palaeolatitude (22+6/?5°) for the Amazon block just after deposition of Puga diamictites. In addition, the presence of multiple reversals across the first 20 m of the cap carbonate sequence suggests that their sedimentation must have spanned hundreds of thousands of years at least. 相似文献
86.
Assessing aquifer vulnerability to pollutants by electrical resistivity tomography (ERT) at a nitrate vulnerable zone in NE Spain 总被引:1,自引:0,他引:1
There is an increasing demand for groundwater vulnerability maps which illustrate the exposure of aquifers against pollution.
These maps show areas of greatest potential for groundwater contamination on the basis of local subsurface conditions. Parameters
affecting vulnerability are mainly permeability and thickness of each protective layer. For unconsolidated sediments, the
permeability is strongly related to the clay content, which can be deduced from indirect resistivity methods, like electrical-imaging.
Such geophysical methods can be of great help in groundwater vulnerability studies because they disturb neither the structure
nor the dynamics of the soil. Sensibility analysis was performed of the electrical resistivity tomography method for accurately
mapping soil media. Managers and public administrators may effectively use this method for assessing the potential risk of
groundwater contamination. In the studied zone, electrical resistivity exhibits a wide range of variability that can be easily
correlated to soil parameters, such as clay content and hydraulic conductivity. A numerical index of protection has been assessed
from the geophysical information derived from 2D electrical resistivity tomography. This work represents a preliminary approach
on the natural vulnerability evaluation of shallow aquifers at the Empordà basin (NE Spain) that is highly affected by diffuse
pollution by nitrates. 相似文献
87.
Smith S.M. An P.E. Holappa K. Whitney J. Burns A. Nelson K. Heatzig E. Kempfe O. Kronen D. Pantelakis T. Henderson E. Font G. Dunn R. Dunn S.E. 《Oceanic Engineering, IEEE Journal of》2001,26(4):453-465
The Advanced Marine Systems Lab at Florida Atlantic University has developed a new ultramodular plastic mini autonomous underwater vehicle (AUV), called the Morpheus, for littoral military and coastal oceanographic sampling, survey, and mapping. The name Morpheus was chosen because the Greek god Morpheus could change shape or "morph." The higher degree of modularity of the Morpheus AUV allows it to "morph" or change its size and components for different applications. This vehicle is composed of modular injection-molded plastic pressure vessels and a cabling system that allow the modules to be rearranged without rewiring bulkheads. The plastic pressure vessels are inexpensive, inherently mass-producible, extremely corrosion-resistant, and have low magnetic signatures. The pressure vessels are small but are sized to fit most standard electronic board standards. The mini AUV can be anywhere from 4 to 10 ft in length, depending on its mission. The vehicle architecture is an adaptation of the Ocean Explorer AUV system and uses an ANSI 709.1 (LonTalk) distributed control network for connecting all sensors and actuator subsystems as smart nodes. The modularity in containers, control, and power makes this vehicle rapidly reconfigurable and easy to repair or upgrade. This paper will present details of the motivation, design, and construction of the new mini AUV. The Morpheus was deployed during the summer of 2000 in field exercises for very shallow and shallow water mine counter measures. Some results from these tests will be presented 相似文献
88.
R. Ll.Brown J. R. Hollwey A. J. Van Der Weele E. H. Thompson 《The Photogrammetric Record》1971,7(38):182-200
Four papers were read during the first symposium to be held by the Photogrammetric Society, at the University of Birmingham on 3rd and 4th April. Major General R. LI. Brown examined the staff structure of the organisations engaged upon the photogrammetric production of maps in the United Kingdom. Mr. J. R. Hollwey outlined the syllabus for a new Higher National Certificate in photogrammetry during a session which was devoted to education and qualifications. Subsequently, Professor A. J. van der Weele explained the evolution of the courses at ITC. By way of contrast, Professor E. H. Thompson attempted a forecast of developments in photogrammetry during the next decade. The papers succeeded in initiating prolonged discussion among the 80 members who attended. 相似文献
89.
M. Font J.‐L. Lagarde D. Amorese J.‐P. Coutard A. Dubois G. Guillemet J.‐C. Ozouf E. Vedie 《地球表面变化过程与地形》2006,31(14):1731-1745
Physical modelling has been developed in order to simulate the effects of periglacial erosion processes on the degradation of slopes and scarps. Data from 41 experimental freeze–thaw cycles are presented. They attest to the efficiency of periglacial processes that control both erosion and changes in scarp morphology: (i) cryoexpulsion leads to an increase of scarp surface roughness and modifies significantly the internal structure of the active layer; (ii) combined effects of frost creep and gelifluction lead to slow and gradual downslope displacements of the active layer (0·3 cm/cycle); (iii) debris flows are associated with the most significant changes in scarp morphology and are responsible for the highest rate of scarp erosion; (iv) quantification of the erosion rate gives values close to 1 cm3 cm?2 for 41 freeze–thaw cycles. These experimental results are consistent with field data acquired along the La Hague fault scarp (Normandy, France) where an erosion rate of 4·6 ± 1 m3 m?2 per glacial stage has been computed from the volume of natural slope deposits stored during the Weichselian glacial stage. These results show that moist periglacial erosion processes could lead to an underestimation of Plio‐Quaternary deformation in the mid‐latitudes. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
90.