全文获取类型
收费全文 | 375篇 |
免费 | 30篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 13篇 |
大气科学 | 28篇 |
地球物理 | 79篇 |
地质学 | 198篇 |
海洋学 | 18篇 |
天文学 | 46篇 |
自然地理 | 25篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 12篇 |
2020年 | 14篇 |
2019年 | 17篇 |
2018年 | 18篇 |
2017年 | 20篇 |
2016年 | 30篇 |
2015年 | 24篇 |
2014年 | 17篇 |
2013年 | 28篇 |
2012年 | 15篇 |
2011年 | 42篇 |
2010年 | 37篇 |
2009年 | 27篇 |
2008年 | 17篇 |
2007年 | 14篇 |
2006年 | 11篇 |
2005年 | 13篇 |
2004年 | 14篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1995年 | 3篇 |
1992年 | 1篇 |
1986年 | 1篇 |
1978年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有407条查询结果,搜索用时 31 毫秒
91.
Delphine Denis Xavier Crosta Sabine Schmidt Damien S. Carson Raja S. Ganeshram Hans Renssen Viviane Bout-Roumazeilles Sebastien Zaragosi Bernard Martin Michel Cremer Jacques Giraudeau 《Quaternary Science Reviews》2009,28(13-14):1291-1303
This study presents a high-resolution multi-proxy investigation of sediment core MD03-2601 and documents major glacier oscillations and deep water activity during the Holocene in the Adélie Land region, East Antarctica. A comparison with surface ocean conditions reveals synchronous changes of glaciers, sea ice and deep water formation at Milankovitch and sub-Milankovitch time scales. We report (1) a deglaciation of the Adélie Land continental shelf from 11 to 8.5 cal ka BP, which occurred in two phases of effective glacier grounding-line retreat at 10.6 and 9 cal ka BP, associated with active deep water formation; (2) a rapid glacier and sea ice readvance centred around 7.7 cal ka BP; and (3) five rapid expansions of the glacier–sea ice systems, during the Mid to Late Holocene, associated to a long-term increase of deep water formation. At Milankovich time scales, we show that the precessionnal component of insolation at high and low latitudes explains the major trend of the glacier–sea ice–ocean system throughout the Holocene, in the Adélie Land region. In addition, the orbitally-forced seasonality seems to control the coastal deep water formation via the sea ice–ocean coupling, which could lead to opposite patterns between north and south high latitudes during the Mid to Late Holocene. At sub-Milankovitch time scales, there are eight events of glacier–sea ice retreat and expansion that occurred during atmospheric cooling events over East Antarctica. Comparisons of our results with other peri-Antarctic records and model simulations from high southern latitudes may suggest that our interpretation on glacier–sea ice–ocean interactions and their Holocene evolutions reflect a more global Antarctic Holocene pattern. 相似文献
92.
Alla Skaskevych Jejung Lee Hahn Chul Jung John Bolten John L. David Frederick S. Policelli Ibrahim B. Goni Guillaume Favreau Soma San Charles M. Ichoku 《水文研究》2020,34(4):941-955
The present study is to explore the feasibility of GRACE-based estimation of a groundwater storage change in a data-poor region using a case study of the Ngadda catchment in the Lake Chad Basin. Although the Ngadda catchment has only one set of in situ time series data of groundwater from 2006 to 2009 and a limited number of groundwater measurements in 2005 and 2009, GRACE-based groundwater storage change can be evaluated against the in situ groundwater measurements combined with specific yield data. The cross-correlation analysis in the Ngadda catchment shows that maximum rainfall reached in July and August, whereas both the maximum total water storage anomaly and the maximum groundwater storage anomaly occurred 2months later. Whereas the mean annual amplitude of total water storage anomaly is about 17cm from both the average total water storage anomaly from three mascon products and the one from three spherical harmonic products, the mean annual amplitude of soil moisture storage anomaly is substantially varied from 5.58cm for CLM to about 14cm for NOAH and Mosaic. The goodness-of-fit tests show that CLM soil moisture produces the closest estimation of groundwater storage anomaly to the in situ groundwater measurements. The present study shows that GRACE-based estimation for groundwater storage anomaly can be a cost-effective and alternative tool to observe how groundwater changes in a basin scale under the limitation of modelling and in situ data availability. 相似文献
93.
Philippe Grosso Marc Le Menn Jean-Louis De Bougrenet De La Tocnaye Zong Yan Wu Damien Malardé 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(1):151-156
Optical salinity sensors described here measure directly the seawater refractive index and thus enable a measurement of the seawater density and composition variation. We detail the measurement dependence to environmental parameters (in particular temperature and pressure) compared to conductivity sensors, and demonstrate that it may be advantageous to directly measure refractive index rather than electrical conductivity and so obtain a more direct route to density and absolute salinity. 相似文献
94.
95.
Anita Moldenhauer-Roth Guillaume Piton Sebastian Schwindt Mona Jafarnejad Anton JSchleiss 《国际泥沙研究》2021,36(1):136-150
Sediment detention basins are implemented on mountain rivers to trap solid material that may aggravate the flooding of downstream settlements.However,retention structures built in the past may unnecessarily retain sediment during non-hazardous flood events,resulting in high maintenance costs and sediment deficit downstream.In addition,the so-called spontaneous self-flushing of previously retained sediment during floods has occasionally been observed.Recent research suggests to design sediment detention basins for controlling sediment passage with a guiding channel across the deposition area upstream of a hybrid barrier.Such barriers consist of a check dam with a slot orifice and an upstream bar screen with a bottom clearance in order to benefit from a combined mechanical-hydraulic retention control.The present paper enhances this pioneering research with the help of new experimental data,including a wide range of sediment mixtures and large wood,as well as variable barrier heights.Improved design criteria are provided regarding the bar screen and the basin storage capacity.The functionality of the enhanced concept for sediment detention is illustrated by a case study on a physical model:the protection of the Villard-Bonnot village(France)against torrential hazards. 相似文献
96.
Marc Blanchard Guillaume Morin Michele Lazzeri Etienne Balan 《Geochimica et cosmochimica acta》2010,74(14):3948-14056
A series of hematite structures containing various amounts of aluminum and hydroxyl groups was modeled using first-principles methods based on the density functional theory. Evolution of the lattice parameters was quantified as a function of Al and H concentrations. The a and c lattice parameters decrease with the aluminum content and increase with the water content. This allows explaining experimental data reported for synthetic hematites, in particular the observed deviation from the Vegard’s rule. Investigation of several hydroxyl configurations associated with cationic vacancies suggests that the speciation of water also significantly affects the hematite structure. The 57Fe and 18O reduced partition functions (β-factor) were determined. Results show a linear dependence of the iron and oxygen β-factors on the aluminum content. An incorporation of 18 mole % Al2O3 in hematite would increase the iron β-factor of about 0.6‰ and the oxygen β-factor of about 5.5‰ at 0 °C. This effect is sufficiently large to be measurable and to affect the interpretation of natural isotopic compositions. On the other hand, the effect of water is found to be negligible for the hydroxyl configuration investigated. 相似文献
97.
Zircon texture and chemical composition as a guide to magmatic processes and mixing in a granitic environment and coeval volcanic system 总被引:3,自引:0,他引:3
Damien Gagnevin J. Stephen Daly Andreas Kronz 《Contributions to Mineralogy and Petrology》2010,159(4):579-596
This study documents the chemical and textural responses of zircon in the Elba igneous complex, with particular reference
to the 7- to 7.8-Ma-old Monte Capanne pluton in relation to its coeval volcanic counterpart (Capraia), using BSE imaging and
quantitative electron microprobe analyses. The Monte Capanne pluton displays multiple field and geochemical evidence for magma
mixing. The samples we have investigated (including monzogranitic, mafic enclave and dyke samples) display similar zircon
textures and are associated with an extremely large range of trace and minor element (Hf, Y, HREE, Th, U) compositions, which
contrast with relatively simple textures and zoning patterns in zircons from a Capraia dacite. We have used a relatively simple
textural classification (patchy zoning, homogenous cores, oscillatory zoning and unzoned zircon) as the basis for discussing
the chemical composition and chemical variation within zircons from the Monte Capanne pluton. Based on these data and other
works (Dini et al. 2004 in Lithos 78:101–118, 2004) , it is inferred that mixing between metaluminous and peraluminous melts occurred early in the
evolution of the Monte Capanne magma chamber. In particular, mixing was responsible for the development of the patchy-zoning
texture in the zircon cores, which was associated with reactions between other accessory phases (including monazite, apatite,
allanite), which we infer to have significantly affected the Th distribution in zircon. Zircons from the MC pluton displaying
“homogeneous cores” have chemical affinities with zircons in the coeval Capraia volcanic system, consistent with the participation
of a Capraia-like mantle end-member during mixing. Further zircon growth in the MC pluton produced the oscillatory zoning
texture, which records both long-term (crystal fractionation) and transient (recharge with both silicic and mafic magmas)
events in a hybrid magma chamber. It is inferred that Hf and the Th/U ratio cannot be used alone to infer magmatic processes
due to their dependency on temperature, nor are they a diagnostic feature of xenocrystic grains. This study shows that zircon
chemistry coupled with detailed textural analysis can provide a powerful tool to elucidate the complex evolution of a magma
system. 相似文献
98.
The Central Plateau Member rhyolites have been erupted between 173 and 70 ka and are the youngest Yellowstone intracaldera
rhyolites. They mostly comprise very voluminous lava flows totaling ~600 km3 in volume. Their eruptive vents define two NNW-trending lineaments which are aligned with regional faults. We present new
whole rock, glass, and mineral analyses and propose a petrogenetic and volcano-tectonic model for these rhyolites. At a caldera-wide
scale, there is a temporal enrichment in elements such as Nb, Y and HREE, and a depletion in Sr, Ba, and Ce/Yb. Simultaneously,
clinopyroxene becomes less magnesian while Ti contents in quartz decrease. By contrast, quartz in all rhyolites is rounded
and bears long glass re-entrants, suggesting heating. Based on these data and observations, we propose that the Central Plateau
Member rhyolites have been generated as follows. A hydrothermally altered low-δ18O rhyolitic protolith beneath the Mallard Lake Resurgent Dome in the southwestern part of the caldera started to melt at ~250 ka.
Repeated heating pulses caused the melting front to expand radially, and a large crystal mush formed beneath much of the caldera.
The mush was able to differentiate but not erupt due to its high crystallinity and viscosity. Further inputs of heat and silicic
magma in this mush increased the degree of melting, forming crystal-poor magma batches which erupted a few hundred to a few
thousand years later through regional faults to form the Central Plateau Member rhyolites. 相似文献
99.
3D structural modeling is a major instrument in geosciences, e.g. for the assessment of groundwater and energy resources or nuclear waste underground storage. Fault network modeling is a particularly crucial step during this task, for faults compartmentalize rock units and plays a key role in subsurface flow, whether faults are sealing barriers or drains. Whereas most structural uncertainty modeling techniques only allow for geometrical changes and keep the topology fixed, we propose a new method for creating realistic stochastic fault networks with different topologies. The idea is to combine an implicit representation of geological surfaces which provides new perspectives for handling topological changes with a stochastic binary tree to represent the spatial regions. Each node of the tree is a fault, separating the space in two fault blocks. Changes in this binary tree modify the fault relations and therefore the topology of the model. 相似文献
100.
Jean Manfroid Damien Hutsemékers Anita L. Cochran William M. Jackson Rita Schulz 《Icarus》2007,187(1):144-155
UVES and HIRES high-resolution spectra of Comet 9P/Tempel 1 are used to investigate the impact and rotational light curves of various species with a view toward building a simple model of the distribution and activity of the sources. The emission by OH, NH, CN, C3, CH, C2, NH2, and OI, are analyzed, as well as the light scattered by the dust. It is found that a simple model reproduces fairly well the impact light curves of all species combining the production of the observed molecules and the expansion of the material throughout the slit. The impact light curves are consistent with velocities of 400-600 m/s. Their modeling requires a three-step dissociation sequence “Grand-Parent → Parent → Daughter” to produce the observed molecules. The rotational light curve for each species is explained in terms of a single model with three sources. The dust component can however not easily be explained that way. 相似文献