全文获取类型
收费全文 | 744篇 |
免费 | 24篇 |
国内免费 | 15篇 |
专业分类
测绘学 | 17篇 |
大气科学 | 42篇 |
地球物理 | 169篇 |
地质学 | 293篇 |
海洋学 | 79篇 |
天文学 | 103篇 |
综合类 | 8篇 |
自然地理 | 72篇 |
出版年
2023年 | 5篇 |
2022年 | 9篇 |
2021年 | 11篇 |
2020年 | 12篇 |
2019年 | 20篇 |
2018年 | 23篇 |
2017年 | 24篇 |
2016年 | 30篇 |
2015年 | 22篇 |
2014年 | 22篇 |
2013年 | 41篇 |
2012年 | 27篇 |
2011年 | 44篇 |
2010年 | 30篇 |
2009年 | 31篇 |
2008年 | 45篇 |
2007年 | 34篇 |
2006年 | 29篇 |
2005年 | 31篇 |
2004年 | 24篇 |
2003年 | 22篇 |
2002年 | 12篇 |
2001年 | 18篇 |
2000年 | 6篇 |
1999年 | 11篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1976年 | 10篇 |
1975年 | 4篇 |
1974年 | 9篇 |
1971年 | 6篇 |
1969年 | 3篇 |
1963年 | 4篇 |
排序方式: 共有783条查询结果,搜索用时 31 毫秒
761.
J. L. Gonzalez-Compean Victor J. Sosa-Sosa Arturo Diaz-Perez Jesus Carretero Ricardo Marcelin-Jimenez 《International Journal of Digital Earth》2018,11(7):730-751
Earth observation satellites produce large amounts of images/data that not only must be processed and preserved in reliable geospatial platforms but also efficiently disseminated among partners/researchers for creating derivative products through collaborative workflows. Organizations can face up this challenge in a cost-effective manner by using cloud services. However, outages and violations of integrity/confidentiality associated to this technology could arise. This article presents FedIDS, a suite of cloud-based components for building dependable geospatial platforms. The Fed component enables organizations to build shared geospatial data infrastructure through federation of independent cloud resources to withstand outages, whereas IDS avoids violations of integrity/confidentiality of images/data in sharing information and collaboration workflows. A FedIDS prototype, deployed in Spain and Mexico, was evaluated through a study case based on a satellite imagery captured by a Mexican antenna and another based on a satellite imagery of a European observation mission. The acquisition, storage and sharing of images among users of the federation, the exchange of images between Mexican and Spanish sites and outage scenarios were evaluated. The evaluation revealed the feasibility, reliability and efficiency of FedIDS, in comparison with available solutions, in terms of performance, storage consume and integrity/confidentiality when sharing images/data in collaborative scenarios. 相似文献
762.
Cabral Victor Carvalho Reis Fábio Augusto Gomes Vieira D’Affonseca Fernando Mazo Lucía Ana dos Santos Corrêa Claudia Vanessa Veloso Vinicius Gramani Marcelo Fischer Ogura Agostinho Tadashi Lazaretti Andrea Fregolente Vemado Felipe Pereira Filho Augusto José dos Santos Claudia Cristina Lopes Eymar Silva Sampaio Rabaco Lis Maria Reoni do Carmo Giordano Lucilia Zarfl Christiane 《Natural Hazards》2021,108(3):3021-3043
Natural Hazards - Debris flows represent great hazard to humans due to their high destructive power. Understanding their hydrogeomorphic dynamics is fundamental in hazard assessment studies,... 相似文献
763.
Acta Geotechnica - Currently, there are debates on the relationship between the effective stress and shear strength of unsaturated soils. Thus, it is imperative to present an efficient method that... 相似文献
764.
正1.Introduction In response to the proposal by the Earth Science community of China,we are delighted to organize this special issue of Geoscience Frontiers(GSF)in honor of the work by Xuanxue Mo,Professor of Petrology and Geochemistry of China University of Geosciences(Beijing)and Academician of the Chinese Academy of Sciences,as a tribute to him on his 80th birthday.In his over 50 years of profes- 相似文献
765.
Thomas Poulet Juan Felipe Giraldo Erick Ramanaidou Agnieszka Piechocka Victor M. Calo 《Basin Research》2023,35(2):572-591
The Hamersley Basin in Western Australia is one of the world's largest iron ore-producing regions, hosting two types of ore in banded iron formations: the high-grade martite-microplaty haematite and the supergene martite-goethite ores. With the high-grade ores almost entirely mined in the last decade, the supergene ores have more recently become the dominant resource of interest. Consequently, understanding the genesis of these martite-goethite deposits is a critical step for exploration. Yet, although various models exist, there is still no consensus on how these mineral resources formed, complicating the prediction of resource volume and location. Here, we show that the paleo-stratigraphic permeability anisotropy (with higher permeability along strata than across) controls the supergene mimetic enrichment transport process and, subsequently, the mineralisation distribution. We introduce a flow model that implicitly represents strata with a potential function that orients the permeability tensor accurately. The numerical solver uses automatic mesh adaptivity to deliver robust solutions. By accurately reproducing the mineralisation patterns in specific deposits, we identify and quantify the paleo-water table level and permeability anisotropy ratio as the two main controlling parameters for the mineralisation distribution. These insights provide new timing constraints for the mineralisation and the physical process of iron enrichment, suggesting much more potential mineralisation volume in the paleo-reconstructed zones than previously anticipated. These flow models allow us to draw geological conclusions with few a priori assumptions required for the genetic model in which the transport component is dominant. The predictive power of this methodology will allow targeted drilling to narrow down the prospective areas and lower exploration costs. Furthermore, the methodology's generality applies to other commodities in sedimentary basins involving supergene processes and will improve our understanding of various genetic models. 相似文献
766.
Simon Belle Claire Parent Victor Frossard Valérie Verneaux Laurent Millet Panagiota-Myrsini Chronopoulou Pierre Sabatier Michel Magny 《Journal of Paleolimnology》2014,52(3):215-228
Freshwater lakes are important sources of methane (CH4) emissions, by organic matter degradation under anaerobic conditions (methanogenesis). Previous studies suggest that lakes contribute up to 16 % of natural emissions. About 60 % of the CH4 produced is used as an energy source by methane-oxidizing bacteria (MOB—methanotrophs), which could support higher trophic levels, especially Chironomidae (Diptera). Because biogenic methane has a very low stable carbon isotope value, evidence of methane-derived organic-matter assimilation can be tracked by stable carbon isotope analysis in consumers such as chironomids. In some cases, however, chironomid δ13C values are not low enough to unambiguously demonstrate methanotroph assimilation and an alternative line of evidence is required. Analysis of ancient DNA (aDNA) from the methanotroph community preserved in lake sediment provides reliable information about past methane oxidation in freshwater lakes. A combination of these two approaches was used to study a sediment core from the deepest zone of Lake Narlay (Jura, France), which covers the last 1,500 years of sediment accumulation. Results show a significant change ca. AD 1600, with an increase in the proportion of MOB in the total bacteria community, and a decrease in chironomid head-capsule δ13C. These trends suggest assimilation of MOB by chironomid larvae, and account for up to 36 % of the chironomid biomass. The data also provide information about the feeding behavior of chironomids, with evidence for preferential assimilation of methanotroph type I and the NC10 phylum. The combination of aDNA analysis and carbon stable isotopes strengthens the reliability of inferences about carbon sources incorporated into chironomid biomass. 相似文献
767.
Mauro Valdés-Barrón Roberto Bonifaz-Alfonzo David Riveros-Rosas Victor Velasco-Herreora Hector Estévez-Pérez Juan Carlos Peláez-Chávez 《Geofísica Internacional》2013,52(1):31-42
The measurement of solar B band Ultraviolet radiation (UVB) should be considered a priority in Mexico due to implications on public health throughout the country (total population, 108 million), but this is not carried out at present. Installed sensors cover only 0.12% of the country. However, there are alternative methods for estimating UVB radiation to overcome the lack of surface data. The most successful of these are based on the use of satellites for environmental monitoring. In the present work, UVB maps are constructed for the entire country using a single, daily satellite measurement of UVB at solar noon from 1978-2003. Satellite-derived values are compared with the ground measurements by a surface station located in Mexico City in order to validate the former. Wavelet spectrum analysis is employed to this end. A close correlation is observed between the two sets of data. Moreover, there is qualitative correspondence between the spatial distribution of the satellite-derived data and the surface topography. The difference resulting throughout the period mentioned is <2% of the average annual cumulative energy. 相似文献
768.
Daniel Kelterbaum Helmut Brückner Vasiliy Dikarev Stefanie Gerhard Anna Pint Alexey Porotov Victor Zin'ko 《Geoarchaeology》2012,27(3):206-219
This project has reconstructed the palaeogeographic and environmental evolution of Lake Chokrak on the Kerch Peninsula, Ukraine, during the mid‐ and late‐Holocene. This record has been evaluated in association with a regional archaeological data set to explore human–environment interactions over this period. The results show major changes in the palaeogeographic setting of Lake Chokrak since the 3rd millennium B.C., when the postglacial marine transgression had started to fill the study area. Microfaunal analyses reveal the long persistence of an open marine embayment that only became separated from the Sea of Azov when a sand barrier developed during the late 2nd millennium B.C. When colonizing the Black Sea region after the 8th century B.C., the Greek settlers erected a fortification with a small settlement on a promontory that was by then a peninsula‐like headland extending into the lake. The colonists abandoned their settlement at the end of the 1st millennium B.C. when the depth of the surrounding lake decreased from 1.5 m to less than 1 m. Today, Lake Chokrak dries up completely during summer. A detailed relative sea level (RSL) curve for the northern coast of Kerch has been established. Sea level reached its highest position at the present day. Since the 3rd millennium B.C., sea level continuously rose, without any of the previously postulated regression/transgression cycles. The RSL curve indicates differential subsidence rates within short distances in relatively stable areas, exceeding 40 cm per 1000 years. © 2012 Wiley Periodicals, Inc. 相似文献
769.
Myint Win Bo Ming-Fang Chang A. Arulrajah Victor Choa 《Geotechnical and Geological Engineering》2012,30(1):45-62
Geotechnical ground investigation is important in all construction works particularly, land reclamation projects. The Changi
East reclamation project is a mega project that involves creation of land space as large as 3,000 hectares in multiple phases
between 1991 and 2005. Ground investigation plays a critical role in the Changi project which involved substantial amount
of ground improvement works after reclamation by sand filling. One important aspect of the investigation was to evaluate the
geotechnical characteristics of the underlying compressible soils beneath the original seabed for the selection of suitable
methods of ground improvement. The other important aspect of the investigation was to characterize and verify the compactness
of the reclaimed sand fill. Many types of in situ tests were extensively used in the project. The field vane shear test provides
correlations between the undrained shear strength and depth for the upper and the lower marine clay strata in the Northern
part and the Southern Part of the reclaimed site. Combined with laboratory undrained shear strength tests, the field vane
strength profiles allow the derivation of the undrained shear strength over effective stress ratios for the upper and the
lower marine clays. In addition, results from three other in situ tests, the piezocone cone penetration test, the flat dilatometer
test, and the self boring pressuremeter test provided useful verification of these correlations. A field-performance based
method of assessing degree of consolidation in the underlying clay was developed by combining field monitoring, laboratory
testing and conventional as well as specialized in situ testing. An effective use of in situ testing methods for assessment,
the outcome of ground improvement and for fill quality control in the densification of granular soils is illustrated with
field observation data collected at the project site. 相似文献
770.
Amartya K. Saha Christopher S. Moses René M. Price Victor Engel Thomas J. SmithIII Gordon Anderson 《Estuaries and Coasts》2012,35(2):459-474
Water budget parameters are estimated for Shark River Slough (SRS), the main drainage within Everglades National Park (ENP)
from 2002 to 2008. Inputs to the water budget include surface water inflows and precipitation while outputs consist of evapotranspiration,
discharge to the Gulf of Mexico and seepage losses due to municipal wellfield extraction. The daily change in volume of SRS
is equated to the difference between input and outputs yielding a residual term consisting of component errors and net groundwater
exchange. Results predict significant net groundwater discharge to the SRS peaking in June and positively correlated with
surface water salinity at the mangrove ecotone, lagging by 1 month. Precipitation, the largest input to the SRS, is offset
by ET (the largest output); thereby highlighting the importance of increasing fresh water inflows into ENP for maintaining
conditions in terrestrial, estuarine, and marine ecosystems of South Florida. 相似文献