全文获取类型
收费全文 | 86篇 |
免费 | 4篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 7篇 |
地球物理 | 22篇 |
地质学 | 30篇 |
海洋学 | 5篇 |
天文学 | 21篇 |
自然地理 | 1篇 |
出版年
2023年 | 1篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 2篇 |
2012年 | 1篇 |
2011年 | 5篇 |
2010年 | 9篇 |
2009年 | 8篇 |
2008年 | 7篇 |
2007年 | 1篇 |
2006年 | 6篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 3篇 |
1998年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1948年 | 2篇 |
排序方式: 共有90条查询结果,搜索用时 31 毫秒
1.
The abundances of 18O and deuterium in the present and past hydrologic cycle have proven to be an important tool in Earth systems science. In contrast, the abundance of 17O in precipitation has thus far been assumed to carry no additional information to that of 18O. Here, we demonstrate, using known constraints on oxygen isotope abundances from the O2 cycle and existing data about the natural abundance of 17O in water, that the relationship between the discrimination against 17O and 18O in water may vary. This relationship, presented here as θ = ln (17α)/ln (18α), is found to be 0.511 ± 0.005 for kinetic transport effects and 0.526 ± 0.001 for equilibrium effects, with very low temperature sensitivity. As a result, the 17Δ of precipitation is controlled primarily by kinetic effects during evaporation of the initial vapor and, in contrast to the deuterium excess, is independent of the temperature at the evaporation (and condensation) site. This makes 17Δ a unique tracer that complements 18O and deuterium, and may allow for a decoupling of changes in the temperature of the ocean, that serves as the vapor source, from changes in the relative humidity above it. In addition, the 17Δ of ice caps is influenced by the kinetic effects in ice formation, and therefore measurement of ice 17Δ can be used as an additional constraint for better understanding and parameterization of these effects. 相似文献
2.
A climatology of the stratosphere is determined from a 20-year integration with the stratospheric version of the Atmospheric
General Circulation Model LMDz. The model has an upper boundary at near 65 km, uses a Doppler spread non-orographic gravity
waves drag parameterization and a subgrid-scale orography parameterization. It also has a Rayleigh damping layer for resolved
waves only (not the zonal mean flow) over the top 5 km. This paper describes the basic features of the model and some aspects
of its radiative-dynamical climatology. Standard first order diagnostics are presented but some emphasis is given to the model’s
ability to reproduce the low frequency variability of the stratosphere in the winter northern hemisphere. In this model, the
stratospheric variability is dominated at each altitudes by patterns which have some similarities with the arctic oscillation
(AO). For those patterns, the signal sometimes descends from the stratosphere to the troposphere. In an experiment where the
parameterized orographic gravity waves that reach the stratosphere are exaggerated, the model stratosphere in the NH presents
much less variability. Although the stratospheric variability is still dominated by patterns that resemble to the AO, the
downward influence of the stratosphere along these patterns is near entirely lost. In the same time, the persistence of the
surface AO decreases, which is consistent with the picture that this persistence is linked to the descent of the AO signal
from the stratosphere to the troposphere. A comparison between the stratospheric version of the model, and its routinely used
tropospheric version is also done. It shows that the introduction of the stratosphere in a model that already has a realistic
AO persistence can lead to overestimate the actual influence of the stratospheric dynamics onto the surface AO. Although this
result is certainly model dependent, it suggests that the introduction of the stratosphere in a GCM also call for a new adjustment
of the model parameters that affect the tropospheric variability. 相似文献
3.
Experimental characterization of the impact of temperature and humidity on the breakdown of soil water repellency in sandy soils and composts
下载免费PDF全文
![点击此处可从《水文研究》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Soil water repellency is a widespread phenomenon with the capacity to alter hydrological and geomorphological processes. Water repellency decays with time, and the consequences are only of concern during the timescale at which the water repellency persists. This study aimed to characterize the influence of temperature and humidity on the breakdown of water repellency. Apparent contact angle measurements were carried out on samples consisting of sand treated with stearic acid as well as naturally repellent dune sands and composts. Temperature and humidity were controlled using a cooled incubator and a purpose designed enclosed box in which humidity could be raised or lowered. Results showed the contact angle of the stearic‐acid‐treated sands decayed with time and that there was a significant increase with stearic acid concentration. For all samples, the decay in apparent contact angle could be described with a continuous breakdown model. The stearic‐acid‐treated sands showed a significant increase in contact angle with relative humidity at a temperature of 10 and 20 °C. These differences diminished with increasing temperature. Similar results were seen for the dune sands and composts. Despite the influence of temperature and humidity on contact angles, there was no significant change in the rate at which the contact angle decayed in any sample. Absolute humidity was found to provide a more relevant indicator than relative humidity when assessing the influence of humidity on repellency over a range of temperatures. The contact angle initially increased with absolute humidity before plateauing owing to the confounding effect of temperature. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
4.
5.
Michel Faure Frederic Laleve Yoshihide Gusokujima Jean-Toshimichi Iiyama Jean-Paul Cadet 《Earth and Planetary Science Letters》1986,77(3-4)
The structures and microstructures of the Takanuki and Hitachi areas in the Abukuma massif, Northeast Japan are described. In the Takanuki area, the basic Gosaisho series thrusts the pelitic Takanuki ones in a HP metamorphic context. The nappe structure is afterwards refolded by a migmatitic dome: the Samegawa dome, in a HT metamorphic context. Microtectonic analysis shows that the nappe was transported from south to north along the stretching lineation. Geometric features suggest that the Samegawa dome was emplaced by diapirism. The role of the thrust surface as an instable interface promoting the doming is emphasized. The Hitachi metamorphic rocks composed of basic schist, limestone and sandstone shist thrust the pelitic rocks of the western Hitachi gneisses. As for the Takanuki area, the thrusting occurred in ductile synmetamorphic conditions with a north or northeastward displacement. Owing to lithologic, petrologic, structural similitudes, the nappe of the Hitachi metamorphic rocks and that of the Gosaisho series are unified into a unique nappe with a northward motion. The emplacement occurred between late Permian and late Cretaceous likely in late Jurassic. The allochthonous units of the Abukuma massif are correlated with the Green Schist nappe described in Southwest Japan, since they are surrounded by the same zones, namely the Tanba zone and the Kurosegawa-Kitakami one. Moreover both in Southwest and Northeast Japan, the emplacement of the Green Schist nappes is due to a shear deformation inducing rotational structures along the stretching lineation indicating the same sense of transport, that is eastward in Southwest Japan and northward in Northeast Japan, owing to the late bending of the Japanese Islands. The late Jurassic nappe structure is obliquely overprinted by a HT metamorphism, Ryoke in Southwest Japan, Abukuma in Northeast Japan, and afterwards cut by late faults as the Median Tectonic Line or the Tanakura fault, giving rise to the present complexity. 相似文献
6.
Storm deposits and storm-generated coarse carbonate breccias on a pelagic outer shelf (South-East Basin, France) 总被引:2,自引:0,他引:2
Michel Seguret Alexis Moussine-Pouchkine Guilherme Raja Gabaglia & Frederic Bouchette 《Sedimentology》2001,48(2):231-254
Uppermost Jurassic limestones of the South‐East Basin (France) are organized into four facies associations that were deposited in four distinct zones: (1) peritidal lagoonal limestones; (2) bioclastic and reefal limestones; (3) pelagic lime mudstones; (4) lime mudstones/calcarenites/coarse breccias. Calcarenite deposits of zone 4 exhibit sedimentary structures that are diagnostic of deposition under wave‐induced combined flow. In subzone 4a, both vertical and lateral transitions from lime mudstone/calcarenite to breccia indicate in situ brecciation under wave‐cyclic loading. Breccias were produced by heterogeneous liquefaction of material previously deposited on the sea floor. Deposits in subzone 4a record relatively long periods (>400 kyr) of sedimentation below wave base, alternating with periods of deposition under wave‐induced currents and periods of in situ deformation. In this zone, storm waves were attenuated by wave–sediment interaction, and wave energy was absorbed by the deformation of soft sediment. With reference to present‐day wave attenuation, water depths in this zone ranged between 50 and 80 m. Landwards of the attenuation zone, in zone 3, storm waves were reduced to fair‐weather wave heights. Storm wave base was not horizontal and became shallower landwards. As a consequence, water depth and wave energy were not linearly related. On a small area of the seaward edge of subzone 4a, cobbles were removed by traction currents and redeposited in subzone 4b. There, they formed a 100‐m‐thick wedge, which prograded over 3 km and was built up by the stacking of 5‐ to 20‐m‐thick cross‐stratified sets of coarse breccia. This wedge records the transport and redeposition of cobbles by a high‐velocity unidirectional component of a combined flow. The increase in flow velocity in a restricted area is proposed to result from flow concentration in a channel‐like structure of the downwelling in the gulf formed by the basin. In more distal subzone 4c, the hydrodynamic effect of wave‐induced currents was quasi‐permanent, and brecciation by wave–sediment interaction occurred only episodically. This indicates that, seawards of the attenuation zone, hydrodynamic storm wave base was deeper than mechanical storm wave base. Uppermost Jurassic carbonates were deposited and soft‐sediment deformed on a hurricane‐dominated ramp of very gentle slope and characterized by a zone of storm wave degeneration, located seawards of a zone of sedimentation below wave base. 相似文献
7.
Claire E. Lazareth Nury Guzman Frederic Candaudap 《Geochimica et cosmochimica acta》2007,71(22):5369-5383
Mollusk shells are increasingly used as records of past environmental conditions, particularly for sea-surface temperature (SST) reconstructions. Many recent studies tackled SST (and/or sea-surface salinity) tracers through variations in the elementary (Mg and Sr) or stable isotope (δ18O) composition within mollusk shells. But such attempts, which sometimes include calibration studies on modern specimens, are not always conclusive. We present here a series of Mg and Sr analyses in the calcitic layer of Concholepas concholepas (Muricidae, Gastropoda) with a very high time-resolution on a time window covering about 1 and a half month of shell formation, performed by Laser Ablation Inductively-Coupled Plasma Mass Spectrometry (LA-ICP-MS) and electron probe micro-analysis (EPMA). The selected specimen of this common Chilean gastropod was grown under controlled environmental conditions and precise weekly time-marks were imprinted in the shell with calcein staining. Strontium variations in the shell are too limited to be interpreted in terms of environmental parameter changes. In contrast, Mg incorporation into the shell and growth rate appear to change systematically between night and day. During the day, Mg is incorporated at a higher rate than at night and this intake seems positively correlated with water temperature. The nightly reduced Mg incorporation is seemingly related to metabolically controlled processes, formation of organic-rich shell increments and nocturnal feeding activity of the animals. The nyctemeral Mg changes in the C. concholepas shell revealed in this study might explain at least part of the discrepancies observed in previous studies on the use of Mg as a SST proxy in mollusk shells. In the case of C. concholepas, Mg cannot be used straightforwardly as a SST proxy. 相似文献
8.
Michael Feast Frederic Pont & Patricia Whitelock 《Monthly notices of the Royal Astronomical Society》1998,298(2):L43-L44
A value for the zero-point (ρ) of the Cepheid period–luminosity relation, < M V >= 2.81 log P + ρ, is deduced by comparing the value of the Oort constant, A , derived from radial velocities with that derived from Hipparcos proper motions. We find in this way that ρ =−1.47 ± 0.13, in excellent agreement with the value derived from Hipparcos trigonometrical parallaxes, ρ = −1.43 ± 0.10, by Feast &38; Catchpole in a recent paper. 相似文献
9.
The Bataan orogene: Eastward subduction, tectonic rotations, and volcanism in the western Pacific (Philippines) 总被引:1,自引:0,他引:1
Jelle de Boer Leroy A. Odom Paul C. Ragland Frederic G. Snider Norman R. Tilford 《Tectonophysics》1980,67(3-4)
The Philippine mobile belt represents a crustal fragment, wedged between two subduction systems exhibiting opposite polarity. The eastern (Philippine—Quezon) system probably originated in the Eocene during northwest—southeast spreading of the west Philippine basin. Westward subduction is continued, probably as a result of northward motion of the Philippine basin crust. The western (Manila—Bataan) system originated in the Oligocene by spreading and formation of the South China Sea basin. Eastward subduction dominates the tectonics in the northern part of the archipelago and resulted in the formation of the Bataan orogene, a sequence of three parallel volcanic arcs emplaced in obducted oceanic crust. Geochemical and radiometric data indicate that the arcs migrated eastward with time (Miocene to Present) while changing composition from tholeiitic via calc-alkaline to shoshonitic. Centers of the latter two types are presently active. Depocenters behind the arcs also migrated eastward with time, suggesting correction of the isostatic disequilibrium caused by geanticlinal uplift of the orogene. Paleomagnetic evidence suggests that central Luzon is rotating counterclockwise probably due to differential spreading in the South China Sea basin. The west Philippine basin rotates clockwise. This results in significant “Einengung” in the southern part of the archipelago. 相似文献
10.
Fishes present on small artificial reefs located 2 km off the central east coast of Florida (USA) were surveyed to determine the acceptability of using stabilized oil and coal ash residue as a component material in construction of artificial fishing reefs. Species richness was not significantly different over 2.5 yr on stabilized oil and coal ash reefs compared to concrete control reefs. Of 19 species tested for significant differences in mean abundance, lane snapper was observed at significantly higher mean abundances on fossil-fuel ash reefs (stabilized oil ash/coal fly ash), while three reef species (hairy blenny, porkfish and gray snapper) were significantly more common on concrete control reefs. Further study is needed to determine whether contaminants (Cu, V, Ni and Zn) from stabilized ash blocks can cause abundance differences for some fishes. Plausible alternate explanations for the differences in mean abundance include both interspecific interactions (competition and predation) and differences in the attraction or retention of fish among reef replicates due to slight variations in reef dimensions. 相似文献