全文获取类型
收费全文 | 211篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 57篇 |
地球物理 | 47篇 |
地质学 | 65篇 |
海洋学 | 13篇 |
天文学 | 15篇 |
综合类 | 1篇 |
自然地理 | 20篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 12篇 |
2017年 | 5篇 |
2016年 | 12篇 |
2015年 | 5篇 |
2014年 | 17篇 |
2013年 | 24篇 |
2012年 | 14篇 |
2011年 | 10篇 |
2010年 | 16篇 |
2009年 | 11篇 |
2008年 | 14篇 |
2007年 | 10篇 |
2006年 | 9篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 4篇 |
2002年 | 6篇 |
2001年 | 2篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有222条查询结果,搜索用时 46 毫秒
71.
An analysis is presented of an ensemble of regional climate model (RCM) experiments from the ENSEMBLES project in terms of mean winter snow water equivalent (SWE), the seasonal evolution of snow cover, and the duration of the continuous snow cover season in the European Alps. Two sets of simulations are considered, one driven by GCMs assuming the SRES A1B greenhouse gas scenario for the period 1951–2099, and the other by the ERA-40 reanalysis for the recent past. The simulated SWE for Switzerland for the winters 1971–2000 is validated against an observational data set derived from daily snow depth measurements. Model validation shows that the RCMs are capable of simulating the general spatial and seasonal variability of Alpine snow cover, but generally underestimate snow at elevations below 1,000 m and overestimate snow above 1,500 m. Model biases in snow cover can partly be related to biases in the atmospheric forcing. The analysis of climate projections for the twenty first century reveals high inter-model agreement on the following points: The strongest relative reduction in winter mean SWE is found below 1,500 m, amounting to 40–80 % by mid century relative to 1971–2000 and depending upon the model considered. At these elevations, mean winter temperatures are close to the melting point. At higher elevations the decrease of mean winter SWE is less pronounced but still a robust feature. For instance, at elevations of 2,000–2,500 m, SWE reductions amount to 10–60 % by mid century and to 30–80 % by the end of the century. The duration of the continuous snow cover season shows an asymmetric reduction with strongest shortening in springtime when ablation is the dominant factor for changes in SWE. We also find a substantial ensemble-mean reduction of snow reliability relevant to winter tourism at elevations below about 1,800 m by mid century, and at elevations below about 2,000 m by the end of the century. 相似文献
72.
Instrumentation built to record seeing data automatically via image motion measurements of bright stars in small telescopes is described. The centroid of the star image is found 256 times s-1 in one dimension and is analyzed on-line. The device works over a range of FWHM values as would be seen through a large telescope between <0.1 and 3.0 arcsec. The first results for two identical instruments set up at two locations near the duPont Telescope at Las Campanas Observatory are reported. For a total of 61 nights of data (450 h at each site), the median seeing is 0.6 arcsec, with quartiles at 0.4 and 0.8 arcsec. These are FWHM values referred to 5000 Å at the zenith. So far, the two sites are indistinguishable on average. 相似文献
73.
The transformation of marine and glaciomarine clay deposits into high sensitive and quick clays is largely dependent on the influence of local and regional geologic history and the resulting stratigraphy. The general conditions that facilitate quick-clay development are well known from numerous laboratory investigations during the last century, but their local and regional in-field variation is less understood. In this study, the geographic distribution of quick clay in SW Sweden is predicted using a multicriteria evaluation model that incorporates both qualitative information (established theory and expert judgment concerning the influences on both quick-clay development and the stratigraphic and geomorphologic distribution of sediment types) and observational data (maps of surficial deposits, geotechnical records and digital elevation data). This information duality cannot be avoided if knowledge from different disciplines is utilized. Considering this, model transparency is important for improvements and for characterizing its reliability for risk analysis. The model was constructed stepwise by an initial parameterization with subsequent hierarchical structuring, weighting and standardization of criteria, before running the full analysis. Comparisons between regional model results and geotechnically documented localities have yielded promising results concerning the model’s ability to predict general trends. However, the large natural and site-specific variability of clay sensitivities is not always captured by the model. These deviations are examined and suggestions are given for minimizing their effect. Applications of model methodology and results are briefly discussed. 相似文献
74.
Many countries around the world respond to global warming and its consequences with various policy instruments. In the economic literature, policy instruments have typically been analysed with respect to efficiency, but little effort has been expended to understand public preferences for these instruments. In an internet-based choice experiment to address this shortcoming, Swedes were asked to choose between two alternative hypothetical policy instruments, each of which reduces CO2 emissions by the same amount. The hypothetical policy instruments were characterized by a number of specific attributes. By varying the levels of each of the attributes, respondents indirectly reveal their preferences for these attributes. Half of the respondents are faced with choices labelled ‘tax’ and ‘other’, and the other half are faced with unlabelled choices (hypothetical instruments). The results show that Swedes tend to dislike the term ‘tax’ and show a preference for instruments with a positive effect on environment-friendly technology and climate awareness. A progressive-like cost distribution is preferred to a regressive cost distribution, and the private cost is negatively related to the choice of policy. 相似文献
75.
da Silveira Lucas Cardoso de Oliveira Amauri Pereira Sánchez Maciel Piñero Codato Georgia Ferreira Maurício Jonas Marques Filho Edson Pereira Božnar Marija Zlata Mlakar Primož 《Boundary-Layer Meteorology》2022,185(2):161-195
Boundary-Layer Meteorology - Statistical properties of turbulence, specifically variances of velocity components, temperature, water vapor, and carbon dioxide densities, are observationally... 相似文献
76.
Dmitrij V. Titov Wojciech J. Markiewicz Nikolay I. Ignatiev Li Song Sanjay S. Limaye Agustin Sanchez-Lavega Jonas Hesemann Miguel Almeida Thomas Roatsch Klaus-Dieter Matz Frank Scholten David Crisp Larry W. Esposito Stubbe F. Hviid Ralf Jaumann Horst U. Keller Richard Moissl 《Icarus》2012,217(2):682-701
Since the discovery of ultraviolet markings on Venus, their observations have been a powerful tool to study the morphology, motions and dynamical state at the cloud top level. Here we present the results of investigation of the cloud top morphology performed by the Venus Monitoring Camera (VMC) during more than 3 years of the Venus Express mission. The camera acquires images in four narrow-band filters centered at 365, 513, 965 and 1010 nm with spatial resolution from 50 km at apocentre to a few hundred of meters at pericentre. The VMC experiment provides a significant improvement in the Venus imaging as compared to the capabilities of the earlier missions. The camera discovered new cloud features like bright “lace clouds” and cloud columns at the low latitudes, dark polar oval and narrow circular and spiral “grooves” in the polar regions, different types of waves at the high latitudes. The VMC observations revealed detailed structure of the sub-solar region and the afternoon convective wake, the bow-shape features and convective cells, the mid-latitude transition region and the “polar cap”. The polar orbit of the satellite enables for the first time nadir viewing of the Southern polar regions and an opportunity to zoom in on the planet. The experiment returned numerous images of the Venus limb and documented global and local brightening events. VMC provided almost continuous monitoring of the planet with high temporal resolution that allowed one to follow changes in the cloud morphology at various scales.We present the in-flight performance of the instrument and focus in particular on the data from the ultraviolet channel, centered at the characteristic wavelength of the unknown UV absorber that yields the highest contrasts on the cloud top. Low latitudes are dominated by relatively dark clouds that have mottled and fragmented appearance clearly indicating convective activity in the sub-solar region. At ~50° latitude this pattern gives way to streaky clouds suggesting that horizontal, almost laminar, flow prevails here. Poleward from about 60°S the planet is covered by almost featureless bright polar hood sometimes crossed by dark narrow (~300 km) spiral or circular structures. This global cloud pattern can change on time scales of a few days resulting in global and local “brightening events” when the bright haze can extend far into low latitudes and/or increase its brightness by 30%. Close-up snapshots reveal plenty of morphological details like convective cells, cloud streaks, cumulus-like columns, wave trains. Different kinds of small scale waves are frequently observed at the cloud top. The wave activity is mainly observed in the 65–80° latitude band and is in particular concentrated in the region of Ishtar Terra that suggests their possible orographic origin. The VMC observations have important implications for the problems of the unknown UV absorber, microphysical processes, dynamics and radiative energy balance at the cloud tops. They are only briefly discussed in the paper, but each of them will be the subject of a dedicated study. 相似文献
77.
78.
ABSTRACTThe groundwater contamination risk in future climates was investigated at three locations in Sweden. Solute transport penetration depths were simulated using the HYDRUS-1D model using historical data and an ensemble of climate projections including two global climate models (GCMs), three emission scenarios and one regional climate model. Most projections indicated increasing precipitation and evapotranspiration until mid-century with a further increase at end-century. Results showed both increasing and decreasing groundwater contamination risks depending on emission scenario and GCM. Generally, the groundwater contamination risk is likely to be unchanged until mid-century, but higher at the end of the century. Soil and site specific relationships between Δ(P – PET) (i.e. change in the difference between precipitation, P, and potential evapotranspiration, PET) and changes in solute transport depths were determined. Using this, changes in solute transport depths for other climate projections can be assessed. 相似文献
79.
David Valença Dantas Mario Barletta André Ricardo Araújo Lima Jonas de Assis Almeida Ramos Monica Ferreira da Costa Ulrich Saint-Paul 《Estuaries and Coasts》2012,35(2):587-602
The seasonal and spatial distribution (density and biomass) of five size classes of two catfish species (Cathorops spixii and Cathorops agassizii) were studied along an estuarine ecocline to test the relative importance of the nursery function of each habitat. Seasonal
vs. area interactions were significant for all size classes of both species. During the early rainy season, the middle estuary
is an important nursery habitat for juveniles of both species. When environmental conditions change during the late rainy
season, the C. spixii primary nursery habitat shifts to the lower estuary. During this period, juveniles of C. agassizii remain in the middle estuary. Another important ecological area is the upper estuary, which becomes a breeding, spawning
and hatchery area during the late dry season for both species. The nursery function of habitats shifts according to the seasonal
fluctuation of salinity and dissolved oxygen, and each species responds differently to this change. 相似文献
80.
The sandhopper Talitrus saltator (Crustacea: Amphipoda) as a biomonitor of trace metal bioavailabilities in European coastal waters 总被引:1,自引:0,他引:1
Fialkowski W Calosi P Dahlke S Dietrich A Moore PG Olenin S Persson LE Smith BD Spegys M Rainbow PS 《Marine pollution bulletin》2009,58(1):39-44
The amphipod crustacean Talitrus saltator is an established, easily accessible, biomonitor of trace metal bioavailabilities in coastal waters. We have carried out a geographically widespread collection of T. saltator from European shores, stretching from the north-west Atlantic through the Baltic to the Mediterranean. A primary aim of the work was to establish a database of accumulated trace metal concentrations (Cd, Cr, Cu, Fe, Mn and Zn) in this biomonitor. Statistical analysis has shown significant geographical differences in the bioavailabilities of all the metals, the most distinct being copper, iron and manganese. It has proved possible to identify unusually high accumulated concentrations of Cd, Cr, Cu, Fe, Mn and Zn in this biomonitor, indicative of high metal bioavailability at a particular site. These may serve as reference points for future biomonitoring programmes seeking to identify metal contamination in coastal waters. 相似文献