全文获取类型
收费全文 | 269篇 |
免费 | 25篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 9篇 |
地球物理 | 89篇 |
地质学 | 95篇 |
海洋学 | 48篇 |
天文学 | 28篇 |
自然地理 | 21篇 |
出版年
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 1篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 12篇 |
2014年 | 13篇 |
2013年 | 21篇 |
2012年 | 16篇 |
2011年 | 18篇 |
2010年 | 11篇 |
2009年 | 23篇 |
2008年 | 20篇 |
2007年 | 17篇 |
2006年 | 17篇 |
2005年 | 12篇 |
2004年 | 10篇 |
2003年 | 12篇 |
2002年 | 10篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有295条查询结果,搜索用时 15 毫秒
271.
Angela Schwering 《Transactions in GIS》2008,12(1):5-29
Semantic similarity is central for the functioning of semantically enabled processing of geospatial data. It is used to measure the degree of potential semantic interoperability between data or different geographic information systems (GIS). Similarity is essential for dealing with vague data queries, vague concepts or natural language and is the basis for semantic information retrieval and integration. The choice of similarity measurement influences strongly the conceptual design and the functionality of a GIS. The goal of this article is to provide a survey presentation on theories of semantic similarity measurement and review how these approaches – originally developed as psychological models to explain human similarity judgment – can be used in geographic information science. According to their knowledge representation and notion of similarity we classify existing similarity measures in geometric, feature, network, alignment and transformational models. The article reviews each of these models and outlines its notion of similarity and metric properties. Afterwards, we evaluate the semantic similarity models with respect to the requirements for semantic similarity measurement between geospatial data. The article concludes by comparing the similarity measures and giving general advice how to choose an appropriate semantic similarity measure. Advantages and disadvantages point to their suitability for different tasks. 相似文献
272.
273.
Angela B. Collins Michelle R. Heupel Colin A. Simpfendorfer 《Estuaries and Coasts》2008,31(6):1174-1183
Passive acoustic telemetry was used to monitor the movements of cownose rays (Rhinoptera bonasus) within the Caloosahatchee River estuary in Southwest Florida. Twelve rays were tracked within the river between January 2004 and May 2005 for periods up to 234 days. Linear home range was calculated for all individuals and ranged between 0 and 18.4 km (daily) and 1 and 22.3 km (overall). Ray position within the river was compared to changing water quality parameters throughout the study. Although home range size did not increase with increasing salinity, individuals did occur farther upriver with decreasing flow rates and increasing salinity. There were no differences detected between day and night distribution patterns. Movement and presence patterns demonstrated significant use of the estuarine river over all months, indicating that cownose rays in southwest Florida may not undertake long seasonal migrations as established for other parts of their range. 相似文献
274.
The sensitivity of ECHAM4/ML to a double CO2 scenario for the Late Miocene and the comparison to terrestrial proxy data 总被引:2,自引:2,他引:0
Anke Steppuhn Arne Micheels Angela A. Bruch Dieter Uhl Torsten Utescher Volker Mosbrugger 《Global and Planetary Change》2007,57(3-4):189-212
For the Tortonian, Steppuhn et al. [Steppuhn, A., Micheels, A., Geiger, G., Mosbrugger, V., 2006. Reconstructing the Late Miocene climate and oceanic heat flux using the AGCM ECHAM4 coupled to a mixed-layer ocean model with adjusted flux correction. Palaeogeography, Palaeoclimatology, Palaeoecology, 238, 399–423] perform a model simulation which considers a generally lower palaeorography, a weaker ocean heat transport and an atmospheric CO2 concentration of 353 ppm. The Tortonian simulation of Steppuhn et al. [Steppuhn, A., Micheels, A., Geiger, G., Mosbrugger, V., 2006. Reconstructing the Late Miocene climate and oceanic heat flux using the AGCM ECHAM4 coupled to a mixed-layer ocean model with adjusted flux correction. Palaeogeography, Palaeoclimatology, Palaeoecology, 238, 399–423] demonstrates some realistic trends: the high latitudes are warmer than today and the meridional temperature gradient is reduced. However, the Tortonian run also indicates some insufficiencies such as too cool mid-latitudes which can be due to an underestimated pCO2 in the atmosphere. As a sensitivity study, we perform a further model experiment for which we additionally increase the atmospheric carbon dioxide (700 ppm). According to this CO2 sensitivity experiment, we find a global warming and a globally more intense water cycle as compared to the previous Tortonian run. Particularly the high latitudes are warmer in the Tortonian CO2 sensitivity run which leads to a lower amount of Arctic sea ice and a reduced equator-to-pole temperature difference. Our Tortonian CO2 sensitivity study basically agrees with results from recent climate model experiments which consider an increase of CO2 during the next century (e.g. [Cubasch, U., Meehl, G.A., Boer, G.J., Stouffer, R.J., Dix, M., Noda, A., Senior, C.A., Raper, S., Yap, K.S., 2001. Projections of Future Climate Change. In: Houghton, J.T., Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K. Maskell, C.A. Johnson (eds.), Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, 525–582]) suggesting that the climatic response on a higher atmospheric CO2 concentration is almost independent from the different settings of boundary conditions (Tortonian versus today). To validate the Tortonian model simulations, we perform a quantitative comparison with terrestrial proxy data. This comparison demonstrates that the Tortonian CO2 sensitivity experiment tends to be more realistic than the previous Tortonian simulation by Steppuhn et al. [Steppuhn, A., Micheels, A., Geiger, G., Mosbrugger, V., 2006. Reconstructing the Late Miocene climate and oceanic heat flux using the AGCM ECHAM4 coupled to a mixed-layer ocean model with adjusted flux correction. Palaeogeography, Palaeoclimatology, Palaeoecology, 238, 399–423]. However, a high carbon dioxide concentration of 700 ppm is questionable for the Late Miocene, and it cannot explain shortcomings of our Tortonian run with ‘normal’ CO2. In order to fully understand the Late Miocene climate, further model experiments should also consider the palaeovegetation. 相似文献
275.
276.
277.
The ShakeMap software automatically generates maps of the peak ground motion parameters (shakemaps) and of instrumental intensity
soon after an earthquake. Recorded data are fundamental to obtaining accurate results. In case observations are not available,
ShakeMap relies on ground motion predictive equations, but due to unmodelled site conditions or finite fault effects, large
uncertainties may appear, mainly in the near-source area where damage is relevant. In this paper, we aim to account for source
effects in ShakeMap by computing synthetics to be used for integrating observations and ground motion predictive equations
when near-source data are not available. To be effective, the computation of synthetics, as well as of the finite fault, should
be done in near real time. Therefore, we computed rapid synthetic seismograms, by a stochastic approach, including the main
fault features that were obtained through inversion of regional and teleseismic data. The rapidity of calculation is linked
to a number of assumptions, and simplifications that need testing before the procedure can run in automatic mode. To assess
the performance of our procedure, we performed a retrospective validation analysis considered as case study of the M
w = 6.3 earthquake, which occurred in central Italy on April 6, 2009. In that case, the first shakemaps, generated a few minutes
after the earthquake, suffered large uncertainties on ground motion estimates in an area closer to the epicenter due to the
lack of near-field data. To verify our approach, we recomputed shakemaps for the L’Aquila earthquake, integrating data available
soon after the earthquake at different elapse times with synthetics, and we compared our shaking map with the final shakemap,
obtained when all the data were available. Our analysis evidences that (1) when near-source data are missing, the integration
of real data with synthetics reduces discrepancies between computed and actual ground shaking maps, mainly in the near-field
zone where the damage is relevant and (2) the approach that we adopted is promising in trying to reduce such discrepancies
and could be easily implemented in ShakeMap, but some a priori calibration is necessary before running in an automatic mode. 相似文献
278.
The ocean floor is one of the main accumulation sites of marine debris. The study of this kind of debris still lags behind that of shorelines. It is necessary to identify the methods used to evaluate this debris and how the results are presented and interpreted. From the available literature on benthic marine debris (26 studies), six sampling methods were registered: bottom trawl net, sonar, submersible, snorkeling, scuba diving and manta tow. The most frequent method used was bottom trawl net, followed by the three methods of diving. The majority of the debris was classified according to their former use and the results usually expressed as items per unity of area. To facilitate comparisons of the contamination levels among sites and regions some standardization requirements are suggested. 相似文献
279.
280.