全文获取类型
收费全文 | 1048篇 |
免费 | 51篇 |
国内免费 | 11篇 |
专业分类
测绘学 | 30篇 |
大气科学 | 182篇 |
地球物理 | 248篇 |
地质学 | 437篇 |
海洋学 | 34篇 |
天文学 | 119篇 |
综合类 | 6篇 |
自然地理 | 54篇 |
出版年
2023年 | 6篇 |
2022年 | 2篇 |
2021年 | 26篇 |
2020年 | 27篇 |
2019年 | 25篇 |
2018年 | 38篇 |
2017年 | 30篇 |
2016年 | 60篇 |
2015年 | 46篇 |
2014年 | 61篇 |
2013年 | 79篇 |
2012年 | 61篇 |
2011年 | 75篇 |
2010年 | 59篇 |
2009年 | 68篇 |
2008年 | 58篇 |
2007年 | 44篇 |
2006年 | 55篇 |
2005年 | 48篇 |
2004年 | 31篇 |
2003年 | 23篇 |
2002年 | 25篇 |
2001年 | 22篇 |
2000年 | 14篇 |
1999年 | 19篇 |
1998年 | 13篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1974年 | 1篇 |
1965年 | 1篇 |
1962年 | 1篇 |
1960年 | 1篇 |
1958年 | 1篇 |
1957年 | 2篇 |
1951年 | 1篇 |
1950年 | 1篇 |
排序方式: 共有1110条查询结果,搜索用时 140 毫秒
911.
912.
913.
High crustal diversity preserved in the lunar meteorite Mount DeWitt 12007 (Victoria Land,Antarctica)
下载免费PDF全文
![点击此处可从《Meteoritics & planetary science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Alberto Collareta Massimo D'Orazio Maurizio Gemelli Andreas Pack Luigi Folco 《Meteoritics & planetary science》2016,51(2):351-371
The meteorite Mount DeWitt (DEW) 12007 is a polymict regolith breccia mainly consisting of glassy impact‐melt breccia particles, gabbroic clasts, feldspathic clasts, impact and volcanic glass beads, basaltic clasts, and mingled breccia clasts embedded in a matrix dominated by fine‐grained crystals; vesicular glassy veins and rare agglutinates are also present. Main minerals are plagioclase (typically An>85) and clinopyroxene (pigeonites and augites, sometimes interspersed). The presence of tranquillityite, coupled with the petrophysical data, the O‐isotope data (Δ17O = ?0.075), and the FeOtot/MnO ratios in olivine (91), pyroxene (65), and bulk rock (77) indicate a lunar origin for DEW 12007. Impactites consist of Al‐rich impact‐melt splashes and plagioclase‐rich meta‐melt clasts. The volcanic products belong to the very low titanium (VLT) or low titanium (LT) suites; an unusual subophitic fragment could be cryptomare‐related. Gabbroic clasts could represent part of a shallow intrusion within a volcanic complex with prevailing VLT affinity. DEW 12007 has a mingled bulk composition with relatively high incompatible element abundances and shows a high crustal diversity comprising clasts from the Moon's major terranes and rare lithologies. First‐order petrographic and chemical features suggest that DEW 12007 could be launch‐paired with other meteorites including Y 793274/981031, QUE 94281, EET 87521/96008, and NWA 4884. 相似文献
914.
915.
916.
Jukka M. Krisp Andreas Keler 《International journal of geographical information science》2015,29(11):1988-2000
Personalized navigation and way-finding are prominent research areas of location-based service (LBSs). This includes innovative concepts for car navigation. Within this paper, we investigate the idea of providing drivers a routing suggestion which avoids ‘complicated crossings’ in urban areas. Inexperienced drivers include persons who have a driver’s license but, for whatever reason, feel uncomfortable to drive in a city environment. Situations where the inexperienced driver has to depend on a navigation device and reach a destination in an unfamiliar territory may be difficult. Preferences of inexperienced drivers are investigated. ‘Fears’ include driving into ‘complicated crossings’. Therefore, the definition and spatial characteristics of ‘complicated crossings’ are investigated. We use OpenStreetMap as a road dataset for the routing network. Based on the topological characteristics of the dataset, measured by the number of nodes, we identify crossings that are ‘complicated’. The user can choose to compute an alternative route that avoids these complicated crossings. This methodology is one step in building a full ‘inexperienced drivers’ routing system, which includes additional preferences from the user group, for example, as avoiding left turns where no traffic light is present. 相似文献
917.
918.
Andreas J. Scheib Jonathan R. Lee Neil Breward James B. Riding 《Proceedings of the Geologists' Association. Geologists' Association》2011,122(3):432-444
High-density regional geochemical data for surface soils in central England and East Anglia reveal that much of their geochemical character is inherited from the tills that they are developed upon. Multivariate statistical analysis highlighted three significant element associations of Al–Fe–Ga–K–La–Mg–Rb, Ca–Sr and K–Fe accounting for almost 93% of the geochemical variability of soils derived from tills. Provenancing the geochemical signatures of the latter elements enabled the construction of ice flow paths associated with two different Middle Pleistocene ‘chalky’ till sheets. A lower till sheet relating to ‘Pennine’ ice flowing from west to east across the region, and an upper till sheet deposited by North Sea ice moving into northern East Anglia, and to the west of the Fen Basin, before fanning-out across central England. Overall, geochemical signatures of different till units are largely derived from local bedrock sources, with dilution and a new geochemical signature acquired as the ice flows over and incorporates new bedrock lithologies. The results show that high resolution soil geochemical data provides a further proxy with which the flow paths of former ice sheets can be delineated. 相似文献
919.
Ulrich?CalliesEmail author Andreas?Plü? Jens?Kappenberg Hartmut?Kapitza 《Ocean Dynamics》2011,61(12):2121-2139
Station Helgoland Roads in the south-eastern North Sea (German Bight) hosts one of the richest long-term time series of marine
observations. Hydrodynamic transport simulations can help understand variability in the local data brought about by intermittent
changes of water masses. The objective of our study is to estimate to which extent the outcome of such transport simulations
depends on the choice of a specific hydrodynamic model. Our basic experiment consists of 3,377 Lagrangian simulations in time-reversed
mode initialized every 7 h within the period Feb 2002–Oct 2004. Fifty-day backward simulations were performed based on hourly
current fields from four different hydrodynamic models that are all well established but differ with regard to spatial resolution,
dimensionality (2D or 3D), the origin of atmospheric forcing data, treatment of boundary conditions, presence or absence of
baroclinic terms, and the numerical scheme. The particle-tracking algorithm is 2D; fields from 3D models were averaged vertically.
Drift simulations were evaluated quantitatively in terms of the fraction of released particles that crossed each cell of a
network of receptor regions centred at the island of Helgoland. We found substantial systematic differences between drift
simulations based on each of the four hydrodynamic models. Sensitivity studies with regard to spatial resolution and the effects
of baroclinic processes suggest that differences in model output cannot unambiguously be assigned to certain model properties
or restrictions. Therefore, multi-model simulations are needed for a proper identification of uncertainties in long-term Lagrangian
drift simulations. 相似文献
920.
CBM and CO2-ECBM related sorption processes in coal: A review 总被引:1,自引:0,他引:1
This article reviews the state of research on sorption of gases (CO2, CH4) and water on coal for primary recovery of coalbed methane (CBM), secondary recovery by an enhancement with carbon dioxide injection (CO2-ECBM), and for permanent storage of CO2 in coal seams.Especially in the last decade a large amount of data has been published characterizing coals from various coal basins world-wide for their gas sorption capacity. This research was either related to commercial CBM production or to the usage of coal seams as a permanent sink for anthropogenic CO2 emissions. Presently, producing methane from coal beds is an attractive option and operations are under way or planned in many coal basins around the globe. Gas-in-place determinations using canister desorption tests and CH4 isotherms are performed routinely and have provided large datasets for correlating gas transport and sorption properties with coal characteristic parameters.Publicly funded research projects have produced large datasets on the interaction of CO2 with coals. The determination of sorption isotherms, sorption capacities and rates has meanwhile become a standard approach.In this study we discuss and compare the manometric, volumetric and gravimetric methods for recording sorption isotherms and provide an uncertainty analysis. Using published datasets and theoretical considerations, water sorption is discussed in detail as an important mechanisms controlling gas sorption on coal. Most sorption isotherms are still recorded for dry coals, which usually do not represent in-seam conditions, and water present in the coal has a significant control on CBM gas contents and CO2 storage potential. This section is followed by considerations of the interdependence of sorption capacity and coal properties like coal rank, maceral composition or ash content. For assessment of the most suitable coal rank for CO2 storage data on the CO2/CH4 sorption ratio data have been collected and compared with coal rank.Finally, we discuss sorption rates and gas diffusion in the coal matrix as well as the different unipore or bidisperse models used for describing these processes.This review does not include information on low-pressure sorption measurements (BET approach) to characterize pore sizes or pore volume since this would be a review of its own. We also do not consider sorption of gas mixtures since the data base is still limited and measurement techniques are associated with large uncertainties. 相似文献