全文获取类型
收费全文 | 228篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 24篇 |
地球物理 | 55篇 |
地质学 | 89篇 |
海洋学 | 22篇 |
天文学 | 14篇 |
综合类 | 2篇 |
自然地理 | 22篇 |
出版年
2024年 | 2篇 |
2021年 | 2篇 |
2020年 | 8篇 |
2019年 | 3篇 |
2018年 | 9篇 |
2017年 | 10篇 |
2016年 | 11篇 |
2015年 | 3篇 |
2014年 | 12篇 |
2013年 | 20篇 |
2012年 | 17篇 |
2011年 | 12篇 |
2010年 | 8篇 |
2009年 | 10篇 |
2008年 | 12篇 |
2007年 | 10篇 |
2006年 | 8篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 4篇 |
1943年 | 1篇 |
排序方式: 共有240条查询结果,搜索用时 31 毫秒
191.
Metamorphic core complexes are usually thought to be associated with regional crustal extension and crustal thinning, where deep crustal material is exhumed along gently dipping normal shear zones oblique to the regional extension direction. We present a new mechanism whereby metamorphic core complexes can be exhumed along crustal‐scale strike‐slip fault systems that accommodated crustal shortening. The Qazaz metamorphic dome in Saudi Arabia was exhumed along a gently dipping jog in a crustal‐scale vertical strike‐slip fault zone that caused more than 25 km of exhumation of lower crustal rocks by 30 km of lateral motion. Subsequently, the complex was transected by a branch of the strike‐slip fault zone, and the segments were separated by another 30 km of lateral motion. Strike‐slip core complexes like the Qazaz Dome may be common and may have an important local effect on crustal strength. 相似文献
192.
The simulation of European heat waves from an ensemble of regional climate models within the EURO-CORDEX project 总被引:4,自引:1,他引:3
Robert Vautard Andreas Gobiet Daniela Jacob Michal Belda Augustin Colette Michel Déqué Jesús Fernández Markel García-Díez Klaus Goergen Ivan Güttler Tomáš Halenka Theodore Karacostas Eleni Katragkou Klaus Keuler Sven Kotlarski Stephanie Mayer Erik van Meijgaard Grigory Nikulin Mirta Patarčić John Scinocca Stefan Sobolowski Martin Suklitsch Claas Teichmann Kirsten Warrach-Sagi Volker Wulfmeyer Pascal Yiou 《Climate Dynamics》2013,41(9-10):2555-2575
The ability of a large ensemble of regional climate models to accurately simulate heat waves at the regional scale of Europe was evaluated. Within the EURO-CORDEX project, several state-of-the art models, including non-hydrostatic meso-scale models, were run for an extended time period (20 years) at high resolution (12 km), over a large domain allowing for the first time the simultaneous representation of atmospheric phenomena over a large range of spatial scales. Eight models were run in this configuration, and thirteen models were run at a classical resolution of 50 km. The models were driven with the same boundary conditions, the ERA-Interim re-analysis, and except for one simulation, no observations were assimilated in the inner domain. Results, which are compared with daily temperature and precipitation observations (ECA&D and E-OBS data sets) show that, even forced by the same re-analysis, the ensemble exhibits a large spread. A preliminary analysis of the sources of spread, using in particular simulations of the same model with different parameterizations, shows that the simulation of hot temperature is primarily sensitive to the convection and the microphysics schemes, which affect incoming energy and the Bowen ratio. Further, most models exhibit an overestimation of summertime temperature extremes in Mediterranean regions and an underestimation over Scandinavia. Even after bias removal, the simulated heat wave events were found to be too persistent, but a higher resolution reduced this deficiency. The amplitude of events as well as the variability beyond the 90th percentile threshold were found to be too strong in almost all simulations and increasing resolution did not generally improve this deficiency. Resolution increase was also shown to induce large-scale 90th percentile warming or cooling for some models, with beneficial or detrimental effects on the overall biases. Even though full causality cannot be established on the basis of this evaluation work, the drivers of such regional differences were shown to be linked to changes in precipitation due to resolution changes, affecting the energy partitioning. Finally, the inter-annual sequence of hot summers over central/southern Europe was found to be fairly well simulated in most experiments despite an overestimation of the number of hot days and of the variability. The accurate simulation of inter-annual variability for a few models is independent of the model bias. This indicates that internal variability of high summer temperatures should not play a major role in controlling inter-annual variability. Despite some improvements, especially along coastlines, the analyses conducted here did not allow us to generally conclude that a higher resolution is clearly beneficial for a correct representation of heat waves by regional climate models. Even though local-scale feedbacks should be better represented at high resolution, combinations of parameterizations have to be improved or adapted accordingly. 相似文献
193.
Sven Kretschmer Walter Geibert Michiel M. Rutgers van der Loeff Sheng Xu 《Geochimica et cosmochimica acta》2011,75(22):6971-6987
This study centers on the question: How sensitive are 231Pa/230Th and 10Be/230Th to sediment composition and redistribution? The natural radionuclides 231Pa, 230Th and 10Be recorded in deep sea sediments are tracers for water mass advection and particle fluxes. We investigate the influence of oceanic particle composition on the element adsorption in order to improve our understanding of sedimentary isotope records. We present new data on particle size specific 231Pa and 10Be concentrations. An additional separation step, based on settling velocities, led to the isolation of a very opal-rich phase. We find that opal-rich particles contain the highest 231Pa and 10Be concentrations, and higher 231Pa/230Th and 10Be/230Th isotope ratios than opal-poor particles. The fractionation relative to 230Th induced by the adsorption to opal-rich particles is more pronounced for 231Pa than for 10Be. We conclude that bulk 231Pa/230Th in Southern Ocean sediments is most suitable as a proxy for past opal fluxes. The comparison between two neighboring cores with rapid and slow accumulation rates reveals that these isotope ratios are not influenced significantly by the intensity of sediment focusing at these two study sites. However, a simulation shows that particle sorting by selective removal of sediment (winnowing) could change the isotope ratios. Consequently, 231Pa/230Th should not be used as paleocirculation proxy in cases where a strong loss of opal-rich material due to bottom currents occurred. 相似文献
194.
A quantitative vulnerability function for fluvial sediment transport 总被引:11,自引:6,他引:5
In quantitative risk assessment, risk is expressed as a function of hazard, elements at risk exposed, and vulnerability. Vulnerability
is defined as the expected degree of loss for an element at risk as a consequence of a certain event, following a natural-scientific
approach combined with economic methods of loss appraisal. The resulting value ranges from 0 (no damage) to 1 (complete destruction).
With respect to torrent processes, i.e., fluvial sediment transport, this concept of vulnerability—though widely acknowledged—did
not result in sound quantitative relationships between process intensities and associated degrees of loss so far, even if
considerable loss occurred during recent years. To close this gap and establish this relationship, data from three well-documented
torrent events in the Austrian Alps were used to derive a quantitative vulnerability function applicable to residential buildings
located on torrent fans. The method applied followed a spatially explicit empirical approach within a GIS environment and
was based on process intensities, the spatial characteristics of elements at risk, and average reconstruction values on a
local scale. Additionally, loss data were collected from responsible administrative bodies and analysed on an object level.
The results suggest a modified Weibull distribution to fit best to the observed damage pattern if intensity is quantified
in absolute values, and a modified Frechet distribution if intensity is quantified relatively in relation to the individual
building height. Additionally, uncertainties resulting from such an empirical approach were studied; in relation to the data
quality a 90% confidence band was found to represent the data range appropriately. The vulnerability relationship obtained
allows for an enhanced quantification of torrent risk, but also for an inclusion in comprehensive vulnerability models including
physical, social, economic, and institutional vulnerability. As a result, vulnerability to mountain hazards might decrease
in the future. 相似文献
195.
Jonas Schwaab Kalyanmoy Deb Erik Goodman Sven Lautenbach Maarten J. van Strien Adrienne Grêt-Regamey 《International journal of geographical information science》2018,32(5):907-930
Multi-objective optimization can be used to solve land-use allocation problems involving multiple conflicting objectives. In this paper, we show how genetic algorithms can be improved in order to effectively and efficiently solve multi-objective land-use allocation problems. Our focus lies on improving crossover and mutation operators of the genetic algorithms. We tested a range of different approaches either based on the literature or proposed for the first time. We applied them to a land-use allocation problem in Switzerland including two conflicting objectives: ensuring compact urban development and reducing the loss of agricultural productivity. We compared all approaches by calculating hypervolumes and by analysing the spread of the produced non-dominated fronts. Our results suggest that a combination of different mutation operators, of which at least one includes spatial heuristics, can help to find well-distributed fronts of non-dominated solutions. The tested modified crossover operators did not significantly improve the results. These findings provide a benchmark for multi-objective optimization of land-use allocation problems with promising prospectives for solving complex spatial planning problems. 相似文献
196.
Vega-Jácome Fiorella Lavado-Casimiro Waldo Sven Felipe-Obando Oscar Gustavo 《Theoretical and Applied Climatology》2018,132(1-2):347-362
Theoretical and Applied Climatology - Hydrological changes were assessed considering possible changes in precipitation and regulation or hydraulic diversion projects developed in the basin since... 相似文献
197.
198.
Sven Illeris 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):120-131
Geografisk Tidsskrift, Danish Journal of Geography 97: 120–131, 1997. The location of services in the Copenhagen region is described and analyzed. Six types of services are distinguished: Local private and public services, serving the daily needs of the population, e.g. retailing, have suburbanized, closely following the distribution of population, though with a time-lag. The same goes for services which serve more special needs, e, g, hospitals. Among producer services, some remain in the centre of Copenhagen, e.g. lawyer firms, partly for historical reasons, partly to minimize costs of face-to-face contacts with business partners. But contrary to traditional theory, most producer services are suburbanizing, mainly in order to find large sites and to improve their accessibility for cars. Some have shifted to the western suburbs to reduce costs (back offices) or to be close to the traffic arteries which connect Copenhagen with the rest of Denmark (wholesaling). Business services, e.g. engineering consultants, have primarily moved to the northern, amenity-rich suburbs, for reasons of prestige and of proximity to their high-status labour force. Still other services have located in a more hap-hazard way where they could find large areas, e.g. the airport and military establishments. 相似文献
199.
Winter‐forest processes affect global and local climates. The interception‐sublimation fraction (F) of snowfall in forests is a substantial part of the winter water budget (up to 40%). Climate, weather‐forecast and hydrological modellers incorporate increasingly realistic surface schemes into their models, and algorithms describing snow accumulation and snow‐interception sublimation are now finding their way into these schemes. Spatially variable data for calibration and verification of wintertime dynamics therefore are needed for such modelling schemes. The value of F was determined from snow courses in open and forested areas in Hokkaido, Japan. The value of F was related to species and canopy‐structure measures such as closure, sky‐view fraction (SVF) and leaf‐area index (LAI). Forest structure was deduced from fish‐eye photographs. The value of F showed a strong linear correlation to structure: F = 0·44 ? 0·6 × SVF for SVF < 0·72 and F = 0 for SVF > 0·72, and F = 0·11 LAI. These relationships seemed valid for evergreen conifers, larch trees, alder, birch and mixed deciduous stands. Forest snow accumulation (SF) could be estimated from snowfall in open fields (So) and to LAI according to SF = So (1 ? 0·11 LAI) as well as from SVF according to SF = So (0·56 + 0·6 SVF) for SVF < 0·72. The value of SF was equal to So for SVF values above 0·72. The value of sky‐view fraction was correlated to the normalized difference snow index (NDSI) using a Landsat‐TM image for observation plots exceeding 1 ha. Variables F and SF were related to NDSI for these plots according to: F = ?0·37NDSI + 0·29 and SF = So (0·81 + 0·37NDSI). These relationships are somewhat hypothetical because plot‐size limitation only allowed one sparse‐forest observation of NDSI to be used. There is, therefore, a need to confirm these relationships with further studies. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献