全文获取类型
收费全文 | 71篇 |
免费 | 3篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 22篇 |
地球物理 | 18篇 |
地质学 | 27篇 |
海洋学 | 3篇 |
天文学 | 1篇 |
自然地理 | 2篇 |
出版年
2023年 | 3篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 8篇 |
2015年 | 2篇 |
2014年 | 5篇 |
2013年 | 4篇 |
2012年 | 7篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2008年 | 4篇 |
2007年 | 1篇 |
2006年 | 3篇 |
2005年 | 5篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 4篇 |
1999年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1989年 | 1篇 |
1966年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有74条查询结果,搜索用时 171 毫秒
31.
There is no monitoring technology available to observe possible changes of stress in the rock mass of a CO2 reservoir or its cap rock formations. Any development of a stress-monitoring technique must be related to the natural regional stress conditions and must be adjusted to the possibly changing in situ stress conditions due to CCS activity. As a step towards an in situ stress-monitoring probe, a lab scale device was developed and used for investigations on the practicability of a hard-inclusion tool for stress monitoring. In situ stress conditions, as deduced from the Altmark Gas Field, were applied to evaluate the efficiency and the limits of this stress-monitoring technique. At lab-scale the applied stresses resp. stress differences with moderate amounts of 9?C15?% of the vertical stress component Sv coincide sufficiently with the resulting strain answers of the hard inclusion tool (i.e., a steel tube corresponding to the liner in the borehole). Therefore, it was possible to re-calculate the stresses and to compare them with the applied ones. The resulting coincidence, however, can be disturbed at high pressure levels due to rock failure around the borehole with extended deformations. In addition, the results are influenced by the mechanical behaviour of the surrounding rock mass type. Nevertheless, a further development of a hard inclusion probe for monitoring of stress changes in deep boreholes can be successful and may be the only possible way to detect stress changes without fracturing damages in deep boreholes. 相似文献
32.
33.
Spatio-Temporal Surface Shear-Stress Variability in Live Plant Canopies and Cube Arrays 总被引:3,自引:2,他引:1
Benjamin Walter Christof Gromke Katherine C. Leonard Costantino Manes Michael Lehning 《Boundary-Layer Meteorology》2012,143(2):337-356
This study presents spatiotemporally-resolved measurements of surface shear-stress τ
s in live plant canopies and rigid wooden cube arrays to identify the sheltering capability against sediment erosion of these
different roughness elements. Live plants have highly irregular structures that can be extremely flexible and porous resulting
in considerable changes to the drag and flow regimes relative to rigid imitations mainly used in other wind-tunnel studies.
Mean velocity and kinematic Reynolds stress profiles show that well-developed natural boundary layers were generated above
the 8 m long wind-tunnel test section covered with the roughness elements at four different roughness densities (λ = 0, 0.017, 0.08, 0.18). Speed-up around the cubes caused higher peak surface shear stress than in experiments with plants
at all roughness densities, demonstrating the more effective sheltering ability of the plants. The sheltered areas in the
lee of the plants are significantly narrower with higher surface shear stress than those found in the lee of the cubes, and
are dependent on the wind speed due to the plants ability to streamline with the flow. This streamlining behaviour results
in a decreasing sheltering effect at increasing wind speeds and in lower net turbulence production than in experiments with
cubes. Turbulence intensity distributions suggest a suppression of horseshoe vortices in the plant case. Comparison of the
surface shear-stress measurements with sediment erosion patterns shows that the fraction of time a threshold skin friction
velocity is exceeded can be used to assess erosion of, and deposition on, that surface. 相似文献
34.
Lenz Dawn D. DeLuca Edward E. Golub Leon Rosner Robert Bookbinder Jay A. Litwin Christof Reale Fabio Peres Giovanni 《Solar physics》1999,190(1-2):131-138
An initial study of long-lived loops observed with TRACE (Lenz et al., 1999) shows that they have no significant temperature stratification and that they are denser than the classic loop model
predicts. Models that agree better with the observations include a loop consisting of a bundle of filaments at different temperatures
and a loop with momentum input by MHD waves. Some implications for coronal heating models and mechanisms are discussed. 相似文献
35.
Olivia Steinemann Susan Ivy-Ochs Sandra Grazioli Marc Luetscher Urs H. Fischer Christof Vockenhuber Hans-Arno Synal 《地球表面变化过程与地形》2020,45(6):1401-1417
Glacial erosion is the basic process that has shaped the landscapes of the Alps. Despite intense research over centuries, and the use of various techniques, determination of glacial erosion rates remains challenging. This is not only because the location where the process occurs is almost inaccessible, but also because it is dependent on many different factors, including ice thickness and velocity, glacier thermal regime and lithology. Reported glacial erosion rates range over several orders of magnitude (0.01 to >10 mm a−1). Most studies focus on crystalline bedrock, whereas few researchers have investigated glacial erosion on limestone. Here we analyse glacially polished bedrock surfaces at the recently deglaciated forefield of the Tsanfleuron glacier, Swiss Alps. The nearly horizontally bedded limestone hosts a well-developed karst system. Meltwater from the glacier drains into the subsurface within a few metres of the ice margin. By combining geomorphological mapping, measurement of cosmogenic 36Cl concentrations of glacially eroded bedrock surfaces and a numerical model (MECED), we quantify at each sample location the amount of rock removed during glacier occupation. The glacial erosion rates calculated from these values range from 0 to 0.08 mm a−1. These are orders of magnitude lower than values measured at comparable sites on crystalline bedrock. The high 36Cl concentrations we measured show that the Tsanfleuron glacier was unable to effectively erode the gently dipping, strongly karstified limestone. We suggest that this effect may play a key role in formation and preservation over many glacial cycles of high-elevation, low-relief limestone plateaus in the Alps. © 2020 John Wiley & Sons Ltd. 相似文献
36.
The concept of drag partitioning to parameterise the surface roughness of sea ice is validated using topography data of regions with high sea ice concentrations. The parameterised drag is compared to measurements obtained by aircraft and ship. The form drag can well be expressed as a function of mean ridge heights and spacings averaged over flight legs of 12 km, if an improved approximation for the coefficient of resistance of a single ridge is used. We find a good agreement between the parameterised and observed drag coefficients. The highest sea ice roughness was encountered close to coastal regions and the lowest in the central Arctic. 相似文献
37.
Dedong Li Sebastian Bauer Katharina Benisch Bastian Graupner Christof Beyer 《Acta Geotechnica》2014,9(1):67-79
Sequestration of CO2 into a deep geological reservoir causes a complex interaction of different processes such as multiphase flow, phase transition, multicomponent transport, and geochemical reactions between dissolved CO2 and the mineral matrix of the porous medium. A prognosis of the reservoir behaviour and the feedback from large-scale geochemical alterations require efficient process-based numerical models. For this purpose, the multiphase flow and multicomponent transport code OpenGeoSys-Eclipse have been coupled to the geochemical model ChemApp. The newly developed coupled simulator was successfully verified for correctness and accuracy of the implemented reaction module by benchmarking tests. The code was then applied to assess the impact of geochemical reactions during CO2 sequestration at a hypothetical but typical Bunter sandstone formation in the Northern German Basin. Injection and spreading of 1.48 × 107 t of CO2 in an anticline structure of the reservoir were simulated over a period of 20 years of injection plus 80 years of post-injection time. Equilibrium geochemical calculations performed by ChemApp show only a low reactivity to the geochemical system. The increased acidity of the aqueous solution results in dissolution of small amounts of calcite, anhydrite, and quartz. Geochemical alterations of the mineral phase composition result in slight increases in porosity and permeability, which locally may reach up to +0.02 and 0.1 %, respectively. 相似文献
38.
In this article, different strategies for estimating first-order degradation rate constants from measured field data are compared by application to multiple, synthetic, contaminant plumes. The plumes were generated by numerical simulation of contaminant transport and degradation in virtual heterogeneous aquifers. These sites were then individually and independently investigated on the computer by installation of extensive networks of observation wells. From the data measured at the wells, that is, contaminant concentrations, hydraulic conductivities, and heads, first-order degradation rates were estimated by three 1D centerline methods, which use only measurements located on the plume axis, and a two-dimensional method, which uses all concentration measurements available downgradient from the contaminant source. Results for both strategies show that the true rate constant used for the numerical simulation of the plumes in general tends to be overestimated. Overestimation is stronger for narrow plumes from small source zones, with an average overestimation factor of about 5 and single values ranging from 0.5 to 20, decreasing for wider plumes, with an average overestimation factor of about 2 and similar spread. Reasons for this overestimation are identified in the velocity calculation, the dispersivity parameterization, and off-centerline measurements. For narrow plumes, the one- and the two-dimensional strategies show approximately the same amount of overestimation. For wider plumes, however, incorporation of all measurements in the two-dimensional approach reduces the estimation error. No significant relation between the number of observation wells in the monitoring network and the quality of the estimated rate constant is found for the two-dimensional approach. 相似文献
39.
Elias M. Zubler Andreas M. Fischer Mark A. Liniger Mischa Croci-Maspoli Simon C. Scherrer Christof Appenzeller 《Climatic change》2014,125(2):237-252
There is a growing need of the climate change impact modeling and adaptation community to have more localized climate change scenario information available over complex topography such as in Switzerland. A gridded dataset of expected future climate change signals for seasonal averages of daily mean temperature and precipitation in Switzerland is presented. The basic scenarios are taken from the CH2011 initiative. In CH2011, a Bayesian framework was applied to obtain probabilistic scenarios for three regions within Switzerland. Here, the results for two additional Alpine sub-regions are presented. The regional estimates have then been downscaled onto a regular latitude-longitude grid with a resolution of 0.02° or roughly 2 km. The downscaling procedure is based on the spatial structure of the climate change signals as simulated by the underlying regional climate models and relies on a Kriging with external drift using height as auxiliary predictor. The considered emission scenarios are A1B, A2 and the mitigation scenario RCP3PD. The new dataset shows an expected warming of about 1 to 6 °C until the end of the 21st century, strongly depending on the scenario and the lead time. Owing to a large vertical gradient, the warming is about 1 °C stronger in the Alps than in the Swiss lowlands. In case of precipitation, the projection uncertainty is large and in most seasons precipitation can increase or decrease. In summer a distinct decrease of precipitation can be found, again strongly depending on the emission scenario. 相似文献
40.
Elias M. Zubler Simon C. Scherrer Mischa Croci-Maspoli Mark A. Liniger Christof Appenzeller 《Climatic change》2014,123(2):255-271
Climate indices facilitate the interpretation of expected climate change impacts for many sectors in society, economy, and ecology. The new localized data set of climatic change signals for temperature and precipitation presented by Zubler et al. (Clim Change, 2013) is applied for an analysis of frequently used climate indices in Switzerland. The indices considered are: number of summer days and tropical nights, growing season length, number of frost days and ice days, heating and cooling degree days, and the number of days with fresh snow. For the future periods 2020-49, 2045-74 and 2070–2099 the indices are computed using a delta-change approach based on the reference period 1980–2009 for the emission scenarios A1B, A2, and RCP3PD. The scenario data suggest the following relevant findings: (1) a doubling of the number of summer days by the end of the century under the scenarios A1B and A2, (2) an appearance of tropical nights even above 1500 m asl, (3) a possible reduction of the number of frost days by more than 3 months at altitudes higher than 2500 m asl, (4) a decline of heating degree days by about 30 % until the end of the century, and (5) the near disappearance of days with fresh snow at low altitudes. It is also shown that the end-of-the-century projections of all indices strongly depend on the chosen emission scenario. 相似文献