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61.
Segura Hans Espinoza Jhan Carlo Junquas Clementine Lebel Thierry Vuille Mathias Garreaud Rene 《Climate Dynamics》2020,54(5):2613-2631
Climate Dynamics - Analyzing December–February (DJF) precipitation in the southern tropical Andes—STA ($$12^{circ },hbox {S}$$–$$20^{circ },hbox {S}$$; > 3000... 相似文献
62.
Jeremy C. Stalker Rene M. Price Victor H. Rivera-Monroy Jorge Herrera-Silveira Sara Morales Jorge A. Benitez David Alonzo-Parra 《Estuaries and Coasts》2014,37(6):1376-1387
Oxygen isotopes and strontium concentrations were used as geochemical tracers to discern the sources of water to Celestún Lagoon, a small subtropical estuary on the western side of the Yucatán Peninsula of Mexico. Celestún Lagoon is underlain by karstified limestone with numerous locations where groundwater is observed discharging directly to the lagoon. In this study, samples of groundwater, lagoon surface water, and seawater (SW) were collected in April 2008 and June 2009 and analyzed for salinity, stable isotopes of oxygen, and strontium (Sr2+) concentrations. These geochemical tracers were used in two tertiary mixing models to calculate the relative ratio inputs of fresh groundwater, brackish groundwater, and SW to the lagoon. Two sources of groundwater were found to contribute to the surface water in the lagoon; one fresh and the other brackish with an average salinity of 19 psu. The fresh groundwater had an oxygen isotopic signature (δ18O) and strontium concentration (Sr2+) of δ18O?=?-3.30‰ and Sr2+?=?0.03 mmol/l, respectively. The brackish groundwater observed in the northern end of the lagoon add a dissimilar oxygen isotopic signature and Sr2+ concentration of δ18O?=?3.01‰ and Sr2+?=?0.12 mmol/l, respectively. Local SW had an isotopic oxygen signature and Sr2+ concentration between the two fresher sources (δ18O?=?1.40‰, Sr2+?=?0.09 mmol/l). The lagoonwide results of the two tracer mixing models (δ18O and Sr2+) agreed well (within 5 %) and indicated a ratio of brackish groundwater–fresh groundwater– SW of 31 %–26 %–43 % (±5 %) for the Sr2+ model and 35 %–25 %–40 % (± 5 %) for the δ18O model. Brackish groundwater is dominant in the northern portion of the lagoon, while SW dominates the southern portion. Fresh groundwater discharge is a significant contributor of water along the entire eastern boundary of the lagoon where mangrove forests are the dominant vegetation. 相似文献
63.
Rene Westerholt Bernd Resch Franz-Benjamin Mocnik Dirk Hoffmeister 《International journal of geographical information science》2018,32(3):571-600
Spatial variance is an important characteristic of spatial random variables. It describes local deviations from average global conditions and is thus a proxy for spatial heterogeneity. Investigating instability in spatial variance is a useful way of detecting spatial boundaries, analysing the internal structure of spatial clusters and revealing simultaneously acting geographic phenomena. Recently, a corresponding test statistic called ‘Local Spatial Heteroscedasticity’ (LOSH) has been proposed. This test allows locally heterogeneous regions to be mapped and investigated by comparing them with the global average mean deviation in a data set. While this test is useful in stationary conditions, its value is limited in a global heterogeneous state. There is a risk that local structures might be overlooked and wrong inferences drawn. In this paper, we introduce a test that takes account of global spatial heterogeneity in assessing local spatial effects. The proposed measure, which we call ‘Local Spatial Dispersion’ (LSD), adapts LOSH to local conditions by omitting global information beyond the range of the local neighbourhood and by keeping the related inferential procedure at a local level. Thereby, the local neighbourhoods might be small and cause small-sample issues. In the view of this, we recommend an empirical Bayesian technique to increase the data that is available for resampling by employing empirical prior knowledge. The usefulness of this approach is demonstrated by applying it to a Light Detection and Ranging-derived data set with height differences and by making a comparison with LOSH. Our results show that LSD is uncorrelated with non-spatial variance as well as local spatial autocorrelation. It thus discloses patterns that would be missed by LOSH or indicators of spatial autocorrelation. Furthermore, the empirical outcomes suggest that interpreting LOSH and LSD together is of greater value than interpreting each of the measures individually. In the given example, local interactions can be statistically detected between variance and spatial patterns in the presence of global structuring, and thus reveal details that might otherwise be overlooked. 相似文献
64.
Wei Peng Rene V. Mayorga 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(4):541-550
Traffic noise can cause severe sound pollution for human communities. This paper proposes a hybrid approach to assess traffic
noise impact under uncertainty. There are many factors influencing traffic noise level, but only three traffic parameters,
namely, traffic flow, traffic speed and traffic component, are highly uncertain. These uncertain parameters are represented
by probability distributions, and Monte Carlo simulations are performed to generate a noise distribution after considering
about other certain influencing factors. Fuzzy set and binary fuzzy relations as well as probability analysis method are applied
to identify the predicted traffic noise impacts in qualitatively and quantitatively. The applicability of this proposed technique
is demonstrated using a case study. 相似文献
65.
66.
Vincent Cloutier René Lefebvre Martine M. Savard Édith Bourque René Therrien 《Hydrogeology Journal》2006,14(4):573-590
A comprehensive hydrogeochemical study was carried out in the Paleozoic Basses-Laurentides sedimentary rock aquifer system in Québec over a 1500 km2 study area. Groundwater samples were collected at 153 sites, characterizing all geological and hydrogeological units to a maximum depth of 140 m. Groundwater was analyzed for major, minor and trace inorganic constituents, stable isotopes δ 2H, δ 18O, and δ 13C of dissolved inorganic carbon (DIC), and some samples were analyzed for 3H, and 14C of DIC. The regional distribution of groundwater types shows that the hydrogeological conditions exert a dominant control on the major ions chemistry of groundwater. Preferential recharge areas are characterized by tritiated Ca-Mg-HCO3 groundwater, and confined conditions by submodern Na-HCO3 and Na-Cl groundwater types. Two groundwater end-members are identified in the aquifer system, modern meteoric water and Pleistocene Champlain Sea water. The region displays significant variations of groundwater geochemistry and quality controlled by glaciation, Champlain Sea invasion, lithological rock diversity, and flow system scales. This situation leads to varied groundwater types and origins within a restricted area. 相似文献
67.
This paper outlines evidence from Pakefield (northern Suffolk), eastern England, for sea‐level changes, river activity, soil development and glaciation during the late Early and early Middle Pleistocene (MIS 20–12) within the western margins of the southern North Sea Basin. During this time period, the area consisted of a low‐lying coastal plain and a shallow offshore shelf. The area was drained by major river systems including the Thames and Bytham. Changes in sea‐level caused several major transgressive–regressive cycles across this low‐relief region, and these changes are identified by the stratigraphic relationship between shallow marine (Wroxham Crag Formation), fluvial (Cromer Forest‐bed and Bytham formations) and glacial (Happisburgh and Lowestoft formations) sediments. Two separate glaciations are recognised—the Happisburgh (MIS 16) and Anglian (MIS 12) glaciations, and these are separated by a high sea level represented by a new member of the Wroxham Crag Formation, and several phases of river aggradation and incision. The principal driving mechanism behind sea‐level changes and river terrace development within the region during this time period is solar insolation operating over 100‐kyr eccentricity cycles. This effect is achieved by the impact of cold climate processes upon coastal, river and glacial systems and these climatically forced processes obscure the neotectonic drivers that operated over this period of time. © British Geological Survey/Natural Environment Research Council copyright 2005. Reproduced with the permission of BGS/NERC. Published by John Wiley & Sons, Ltd. 相似文献
68.
Graciano P. Yumul Jr Carla B. Dimalanta Rodolfo A. Tamayo Jr Rene C. Maury 《Island Arc》2003,12(2):77-91
Abstract The Philippines preserves evidence of the superimposition of tectonic processes in ancient and present‐day collision and subduction zone complexes. The Baguio District in northern Luzon, the Palawan–Central Philippine region and the Mati–Pujada area in southeastern Mindanao resulted from events related to subduction polarity reversal leading to trench initiation, continent‐arc collision and autochthonous oceanic lithosphere emplacement, respectively. Geological data on the Baguio District in Northern Luzon reveal an Early Miocene trench initiation for the east‐dipping Manila Trench. This followed the Late Oligocene cessation of subduction along the west‐dipping proto‐East Luzon Trough. The Manila Trench initiation, which is modeled as a consequence of the counter‐clockwise rotation of Luzon, is attributed to the collision of the Palawan microcontinental block with the Philippine Mobile Belt. In the course of rotation, Luzon onramped the South China Sea crust, effectively converting the shear zone that bounded them into a subduction zone. Several collision‐related accretionary complexes (e.g. Romblon, Mindoro) are present in the Palawan–Central Philippine region. The easternmost collision zone boundary is located east of the Romblon group of islands. The Early Miocene southwestward shift of the collision boundary from Romblon to Mindoro started to end by the Pliocene. Continuous interaction between the Palawan microcontinental block and the Philippine Mobile Belt is presently taken up again along the collisional boundary east of the Romblon group of islands. The Mati–Pujada Peninsula area, on the other hand, is underlain by the Upper Cretaceous Pujada Ophiolite. This supra‐subduction zone ophiolite is capped by chert and pelagic limestones which suggests its derivation from a relatively deep marginal basin. The Pujada Ophiolite could be a part of a proto‐Molucca Sea plate. The re‐interpretation of the geology and tectonic settings of the three areas reaffirm the complex geodynamic evolution of the Philippine archipelago and addresses some of its perceived geological enigmas. 相似文献
69.
Vincent Cloutier René Lefebvre Martine M. Savard René Therrien 《Environmental Earth Sciences》2010,59(5):977-994
The objective of this study was to identify geochemical processes and Quaternary geological events responsible for the variations
in groundwater geochemistry observed in a sedimentary rock aquifer system, including brackish to saline groundwater. Inorganic
constituents and environmental isotopes were analyzed for 146 groundwater samples. Dissolution of carbonates dominates in
recharge areas, resulting in Ca-, Mg-HCO3 groundwater. Further along flow paths, under confined conditions, Ca2+–Na+ ion exchange causes groundwater evolution to Na-HCO3 type. Na-Cl groundwater is also found and it falls on a seawater mixing line. Using conservative tracers, Cl− and Br−, the original Champlain Sea water is shown to have been, in the region, a mixture of about 34% seawater and 66% freshwater,
a composition still retained by some groundwater. Na-Cl groundwater thus results from mixing with former Champlain Sea water
and also from solute diffusion from overlying marine clay. The system is thus found to be at different stages of desalinization,
from the original Champlain Sea water still present in hydraulically stagnant areas of the aquifer to fully flushed conditions
in parts, where more flow occurs, especially in recharge zones. The geochemical processes are integrated within the hydrogeological
context to produce a conceptual geochemical evolution model for groundwater of the aquifer system. 相似文献
70.
Ralf Srama Thomas Stephan Eberhard Grün Norbert Pailer Anton Kearsley Amara Graps Rene Laufer Pascale Ehrenfreund Nicolas Altobelli Kathrin Altwegg Siegfried Auer Jack Baggaley Mark J. Burchell James Carpenter Luigi Colangeli Francesca Esposito Simon F. Green Hartmut Henkel Mihaly Horanyi Annette Jäckel Sascha Kempf Neil McBride Georg Moragas-Klostermeyer Harald Krüger Pasquale Palumbo Andre Srowig Mario Trieloff Peter Tsou Zoltan Sternovsky Oliver Zeile Hans-Peter Röser 《Experimental Astronomy》2009,23(1):303-328
The scientific community has expressed strong interest to re-fly Stardust-like missions with improved instrumentation. We
propose a new mission concept, SARIM, that collects interstellar and interplanetary dust particles and returns them to Earth.
SARIM is optimised for the collection and discrimination of interstellar dust grains. Improved active dust collectors on-board
allow us to perform in-situ determination of individual dust impacts and their impact location. This will provide important
constraints for subsequent laboratory analysis.
The SARIM spacecraft will be placed at the L2 libration point of the Sun–Earth system, outside the Earth’s debris belts and
inside the solar-wind charging environment. SARIM is three-axes stabilised and collects interstellar grains between July and
October when the relative encounter speeds with interstellar dust grains are lowest (4 to 20 km/s). During a 3-year dust collection
period several hundred interstellar and several thousand interplanetary grains will be collected by a total sensitive area
of 1 m2. At the end of the collection phase seven collector modules are stored and sealed in a MIRKA-type sample return capsule.
SARIM will return the capsule containing the stardust to Earth to allow for an extraction and investigation of interstellar
samples by latest laboratory technologies. 相似文献