全文获取类型
收费全文 | 132篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 8篇 |
大气科学 | 16篇 |
地球物理 | 34篇 |
地质学 | 48篇 |
海洋学 | 10篇 |
天文学 | 15篇 |
自然地理 | 9篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 9篇 |
2018年 | 9篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 3篇 |
2013年 | 8篇 |
2012年 | 6篇 |
2011年 | 11篇 |
2010年 | 9篇 |
2009年 | 12篇 |
2008年 | 5篇 |
2007年 | 3篇 |
2006年 | 7篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1941年 | 1篇 |
1940年 | 1篇 |
1934年 | 2篇 |
排序方式: 共有140条查询结果,搜索用时 12 毫秒
111.
Ping Fu Arjen P. Stroeven Jonathan M. Harbor Jakob Heyman Clas Hättestrand Marc W. Caffee 《地球表面变化过程与地形》2019,44(4):918-932
Quantifying glacial erosion contributes to our understanding of landscape evolution and topographic relief production in high altitude and high latitude areas. Combining in situ 10Be and 26Al analysis of bedrock, boulder, and river sand samples, geomorphological mapping, and field investigations, we examine glacial erosion patterns of former ice caps in the Shaluli Shan of the southeastern Tibetan Plateau. The general landform pattern shows a zonal pattern of landscape modification produced by ice caps of up to 4000 km2 during pre-LGM (Last Glacial Maximum) glaciations, while the dating results and landforms on the plateau surface imply that the LGM ice cap further modified the scoured terrain into different zones. Modeled glacial erosion depth of 0–0.38 m per 100 ka bedrock sample located close to the western margin of the LGM ice cap, indicates limited erosion prior to LGM and Late Glacial moraine deposition. A strong erosion zone exists proximal to the LGM ice cap marginal zone, indicated by modeled glacial erosion depth >2.23 m per 100 ka from bedrock samples. Modeled glacial erosion depths of 0–1.77 m per 100 ka from samples collected along the edge of a central upland, confirm the presence of a zone of intermediate erosion in-between the central upland and the strong erosion zone. Significant nuclide inheritance in river sand samples from basins on the scoured plateau surface also indicate restricted glacial erosion during the last glaciation. Our study, for the first time, shows clear evidence for preservation of glacial landforms formed during previous glaciations under non-erosive ice on the Tibetan Plateau. As patterns of glacial erosion intensity are largely driven by the basal thermal regime, our results confirm earlier inferences from geomorphology for a concentric basal thermal pattern for the Haizishan ice cap during the LGM. © 2018 John Wiley & Sons, Ltd. 相似文献
112.
Hydrometeorological thresholds for landslide initiation and forest operation shutdowns on the north coast of British Columbia 总被引:2,自引:3,他引:2
Debris flows and debris avalanches are the most widespread and hazardous types of landslides on the British Columbia north coast. Triggered by heavy rain, they pose risks to forestry workers in sparsely developed regions. The scarcity of long-term quality rain gauges and the lack of weather radar information create significant challenge in predicting the timing of landslides, which could be used to warn and, when necessary, evacuate forestry personnel. Traditional methods to relate rainfall antecedents and rainfall intensity to known landslide dates have proven to be unsatisfactory in this study due to extreme spatial variability of rainfall, enhanced by the orographic effect and the scarcity of rain gauges in a very large area. This has led to an integration of meteorological variables in a landslide advisory system that classifies three types of approaching storms by the 850-mbar wind speed and direction, the occurrence of subtropical moisture flow, and the existence of a warm layer characterized by high thickness values of the 500- to 1,000-mbar pressure levels. The storm classification was combined with a 4-week antecedent rainfall and the 24-h rainfall measured near or in the watershed where logging operations are taking place. This system, once implemented, is thought to reduce loss of life, injury, and economic losses associated with forestry works in the study area. 相似文献
113.
An unstable rock slump, estimated at 5 to 10 × 106 m3, lies perched above the northern shore of Tidal Inlet in Glacier Bay National Park, Alaska. This landslide mass has the potential
to rapidly move into Tidal Inlet and generate large, long-period-impulse tsunami waves. Field and photographic examination
revealed that the landslide moved between 1892 and 1919 after the retreat of the Little Ice Age glaciers from Tidal Inlet
in 1890. Global positioning system measurements over a 2-year period show that the perched mass is presently moving at 3–4 cm
annually indicating the landslide remains unstable. Numerical simulations of landslide-generated waves suggest that in the
western arm of Glacier Bay, wave amplitudes would be greatest near the mouth of Tidal Inlet and slightly decrease with water
depth according to Green’s law. As a function of time, wave amplitude would be greatest within approximately 40 min of the
landslide entering water, with significant wave activity continuing for potentially several hours. 相似文献
114.
The separation between the reference surfaces for orthometric heights and normal heights—the geoid and the quasigeoid—is typically
in the order of a few decimeters but can reach nearly 3 m in extreme cases. The knowledge of the geoid–quasigeoid separation
with centimeter accuracy or better, is essential for the realization of national and international height reference frames,
and for precision height determination in geodetic engineering. The largest contribution to the geoid–quasigeoid separation
is due to the distribution of topographic masses. We develop a compact formulation for the rigorous treatment of topographic
masses and apply it to determine the geoid–quasigeoid separation for two test areas in the Alps with very rough topography,
using a very fine grid resolution of 100 m. The magnitude of the geoid–quasigeoid separation and its accuracy, its slopes,
roughness, and correlation with height are analyzed. Results show that rigorous treatment of topographic masses leads to a
rather small geoid–quasigeoid separation—only 30 cm at the highest summit—while results based on approximations are often
larger by several decimeters. The accuracy of the topographic contribution to the geoid–quasigeoid separation is estimated
to be 2–3 cm for areas with extreme topography. Analysis of roughness of the geoid–quasigeoid separation shows that a resolution
of the modeling grid of 200 m or less is required to achieve these accuracies. Gravity and the vertical gravity gradient inside
of topographic masses and the mean gravity along the plumbline are modeled which are important intermediate quantities for
the determination of the geoid–quasigeoid separation. We conclude that a consistent determination of the geoid and quasigeoid
height reference surfaces within an accuracy of few centimeters is feasible even for areas with extreme topography, and that
the concepts of orthometric height and normal height can be consistently realized and used within this level of accuracy. 相似文献
115.
In this paper, a time series from 1999 to 2007 of absolute total electron content (TEC) values has been computed and analyzed
using singular value decomposition (SVD). The data set has been computed using a Kalman Filter and is based on dual frequency
GPS data from three reference stations in Denmark located in the midlatitude region. The station separation between the three
stations is 132–208 km (the time series of the TEC can be freely downloaded at ). For each year, a SVD has been performed on the TEC time series in order to identify the three time varying (daily, yearly,
and 11 yearly) characteristics of the ionosphere. The applied SVD analysis provides a new method for separating the daily
from the yearly components. The first singular value is very dominant (approximately six times larger than the second singular
value), and this singular value corresponds clearly to the variation of the daily cycle over the year. The second singular
value corresponds to variations of the width of the daily peak over the year, and the third singular value shows a clear yearly
variation of the daily signal with peaks around the equinoxes. The singular values for each year show a very strong correlation
with the sunspot number for all the singular values. The correlation coefficients for the first 5 sets of singular values
are all above 0.96. Based on the SVD analysis yearly models of the TEC in the ionosphere can be recomposed and illustrate
the three time varying characteristics of the ionosphere very clearly. By prediction of the yearly mean sunspot number, future
yearly models can also be predicted. These can serve as a priori information for a real time space weather service providing
information of the current status of the ionosphere. They will improve the Kalman filter processing making it more robust,
but can also be used as starting values in the initialization phase in case of gaps in the data stream. Furthermore, the models
can be used to detect variations from the normal local ionospheric activity. 相似文献
116.
The formation of sub-seafloor gas hydrates in marine environments can be described as a coupled transport and thermodynamic process inside a host sediment matrix undergoing structural evolution. The transport processes are driven by the sedimentary load and induced overpressure gradients, controlled by sediment permeability. In order to accurately model the resulting fluid flow profile, the decrease of sediment permeability during hydrate precipitation has to be taken into account, which affects both the transport of solutes and sediment compaction. In this paper, we investigate how total hydrate abundance is affected by regions of low permeability which deflect the flow field in their vicinity. For this purpose, a two-dimensional numerical hydrate system model was set up which permits to quantify this effect in scenarios where changes in water depth cause lateral variations of the thickness of the hydrate stability field, as well as of hydrate saturation and sediment permeability. The microscopic structure of gas hydrate crystals in the host sediment matrix defines the evolution of the permeability reduction during hydrate formation. Grain-coating precipitates have a stronger tendency to clog flow paths through pore throats than do pore-filling precipitates. Our results clearly show that these pore-scale processes affect the large-scale flow field and hydrate abundance. The sensitivity depends on the model geometry and, for a 5° slope of the seafloor, 4.1% relative difference is predicted for the hydrate saturation according to different porosity-permeability relationships. 相似文献
117.
118.
High-quality seismic data document a Maastrichtian-Paleocene rift episode on the Vøring margin lasting for 20 m.y. prior to continental breakup. The rift structures are well imaged in the Fenris Graben and Gjallar Ridge region in the western Vøring Basin, and are characterized by low-angle detachment faults with variable fault geometries from south to north. The structural restoration has facilitated the division of pre- and syn-rift sediments across the extensional terrain, which is subsequently used to evaluate mode and mechanism for the lithospheric deformation. Extension estimates based on the structural restoration, subsidence analysis and crustal thickness evaluations yield stretching factors ranging between 1.5 to 2.3 across the main fault zone just landward of the early Tertiary flood basalts. The structural restoration also shows that a middle crustal dome structure, observed beneath the low-angle faults, can be explained by extensional unroofing. Thus, the dome structure may represent a possible metamorphic core complex. Calculations of the effects on vertical motion, assuming uniform and two-layer differential stretching models combined with the arrival of the Iceland mantle plume during rifting, indicate that the uniform extension model may account for both observed early rift subsidence and subsequent late rift uplift and erosion. Although the differential model can not be excluded, it implies early rift uplift which is not compatible with our seismic interpretation. The direct and indirect effects of the Iceland mantle plume may have caused as much as 1.2 km of late rift uplift. Comparison of the volcanic Vøring margin and the non-volcanic West Iberian margin shows similarities in terms of structural style as well as in mode and distribution of extension. 相似文献
119.
Spatio‐temporal controls of snowmelt and runoff generation during rain‐on‐snow events in a mid‐latitude mountain catchment
下载免费PDF全文
![点击此处可从《水文研究》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A network of 30 standalone snow monitoring stations was used to investigate the snow cover distribution, snowmelt dynamics, and runoff generation during two rain‐on‐snow (ROS) events in a 40 km2 montane catchment in the Black Forest region of southwestern Germany. A multiple linear regression analysis using elevation, aspect, and land cover as predictors for the snow water equivalent (SWE) distribution within the catchment was applied on an hourly basis for two significant ROS flood events that occurred in December 2012. The available snowmelt water, liquid precipitation, as well as the total retention storage of the snow cover were considered in order to estimate the amount of water potentially available for the runoff generation. The study provides a spatially and temporally distributed picture of how the two observed ROS floods developed in the catchment. It became evident that the retention capacity of the snow cover is a crucial mechanism during ROS. It took several hours before water was released from the snowpack during the first ROS event, while retention storage was exceeded within 1 h from the start of the second event. Elevation was the most important terrain feature. South‐facing terrain contributed more water for runoff than north‐facing slopes, and only slightly more runoff was generated at open compared to forested areas. The results highlight the importance of snowmelt together with liquid precipitation for the generation of flood runoff during ROS and the large temporal and spatial variability of the relevant processes. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
120.
Kremer Thomas Irons Trevor Mller-Petke Mike Juul Larsen Jakob 《Surveys in Geophysics》2022,43(4):999-1053
Surveys in Geophysics - Surface nuclear magnetic resonance (sNMR) is an electromagnetic hydrogeophysical method directly sensitive to liquid phase water in the upper $$\approx $$ 100 m of the... 相似文献