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81.
Shallow-water hydrothermal activity is widely present at Azores archipelago. Organisms in such environments present great potential as sentinels of the effects derived from chronically exposure to increased temperature, metal concentrations and reduced pH. This study aimed to evaluate metal concentration in Corallina elongata collected at locations exposed and not exposed to shallow-water hydrothermal activity and evaluate changes in its calcareous structure. Elemental concentration was determined and morphometric analysis was performed by scanning electron microscopy. Thicker cell walls and a bleached appearance were observed on C. elongata specimens from the hydrothermally active location, as well as increased concentrations of elements associated to volcanic activity.This study reports on metal accumulation and morphometric changes in the calcareous structure of C. elongata from a hydrothermally active location, adding new data for further research on such habitats and communities, providing an insight on how coralline algae might be affected by ocean acidification. 相似文献
82.
G. Melián F. Tassi N. Pérez P. Hernández F. Sortino O. Vaselli E. Padrón D. Nolasco J. Barrancos G. Padilla F. Rodríguez S. Dionis D. Calvo K. Notsu H. Sumino 《Bulletin of Volcanology》2012,74(6):1465-1483
The present work reports the results of 15 studies of diffuse CO2 degassing performed at Teide Volcano crater (Canary Island, Spain) and the chemical and isotopic compositions of fluids discharged from a fumarolic field located at the top of the volcano as measured between 1991 and 2010. A higher contribution of magmatic gases accompanied by enhanced total diffuse CO2 emissions were observed in relation with a seismic crisis that occurred in Tenerife Island between 2001 and 2005, with the main peak of seismic activity between April and June 2004. A significant pulse in total diffuse CO2 emission was observed at the crater of Teide (up to 26.3?t day?1) in 2001. In December 2003, the chemical composition of the Teide fumarole changed significantly, including the appearance of SO2, an increase in the HCl and CO concentrations and in the C2H6/C2H4 and C3H8/C3H6 ratios, and a decrease in the H2S, CH4, and C6H6 concentrations and in the gas/steam ratio. A few months after a drastic decrease in seismic activity, the SO2, HCl, and CO concentrations and the C2H6/C2H4 and C3H8/C3H6 ratios strongly decreased, whereas the CH4 and C6H6 concentrations and the gas/steam ratios increased. According to the trends shown by both the geochemical parameters and the seismic signals late in the observation period, the risk of a rejuvenation of volcanic activity at Teide is considered to be low. The associated temporal changes in seismic activity and magmatic degassing indicate that geophysical and fluid geochemistry signals in this system are related. Future monitoring programs aimed at mitigating volcanic hazard on Tenerife Island should involve coupled geophysical and geochemical studies. 相似文献
83.
84.
Anomalous Diffuse CO2 Emissions at the Masaya Volcano (Nicaragua) Related to Seismic-Volcanic Unrest
Germán D. Padilla Pedro A. Hernández Nemesio M. Pérez Ernesto Pereda Eleazar Padrón Gladys Melián José Barrancos Fátima Rodríguez Samara Dionis David Calvo Martha Herrera Wilfried Strauch Angélica Muñoz 《Pure and Applied Geophysics》2014,171(8):1791-1804
Anomalous changes in the diffuse emission of carbon dioxide within the Masaya caldera have been observed before two seismic events that occurred at 10 and 30 km from the observation site. Their epicenters are located, respectively, south of Managua in Las Colinas (4.3 magnitude) and the Xiloa caldera (3.6 magnitude), in 2002 and 2003, recorded by the geochemical station located at El Comalito, Masaya volcano (Nicaragua). Anomalous increases were observed, which occurred around 50 and 8 days before the main seismic event that took place in Las Colinas, and 4 days before the seismic swarm at the Xiloa caldera, with a maximum CO2 efflux of 9.3 and 10.7 kg m?2 day?1, respectively. The anomalous CO2 efflux increases remained after filtering with multiple regression analysis was applied to the CO2 efflux time series, which indicated that atmospheric variables, during the first 4 months, explained 23 % CO2 variability, whereas, during the rest of the time series, CO2 efflux values are poorly controlled with only 6 %. The observed anomalies of the diffuse CO2 emission rate might be related to pressure changes within the volcanic–hydrothermal system and/or to geostructural changes in the crust due to stress/strain changes caused before and during the earthquakes’ formation, and seem not to be related to the activity of the main crater of Masaya volcano. 相似文献
85.
Naraya Carrasco Ruben Kretzschmar Jide Xu Stephan M Kraemer 《Geochemical transactions》2009,10(1):5-9
Siderophore-promoted iron acquisition by microorganisms usually occurs in the presence of other organic molecules, including
biosurfactants. We have investigated the influence of the anionic surfactant sodium dodecyl sulfate (SDS) on the adsorption
of the siderophores DFOB (cationic) and DFOD (neutral) and the ligand EDTA (anionic) onto goethite (α-FeOOH) at pH 6. We also
studied the adsorption of the corresponding 1:1 Fe(III)-ligand complexes, which are products of the dissolution process. Adsorption
of the two free siderophores increased in a similar fashion with increasing SDS concentration, despite their difference in
molecule charge. In contrast, SDS had little effect on the adsorption of EDTA. Adsorption of the Fe-DFOB and Fe-DFOD complexes
also increased with increasing SDS concentrations, while adsorption of Fe-EDTA decreased. Our results suggest that hydrophobic
interactions between adsorbed surfactants and siderophores are more important than electrostatic interactions. However, for
strongly hydrophilic molecules, such as EDTA and its iron complex, the influence of SDS on their adsorption seems to depend
on their tendency to form inner-sphere or outer-sphere surface complexes. Our results demonstrate that surfactants have a
strong influence on the adsorption of siderophores to Fe oxides, which has important implications for siderophore-promoted
dissolution of iron oxides and biological iron acquisition. 相似文献
86.
Fernando Calvo Canales 《Pure and Applied Geophysics》1965,62(1):215-223
Résumé L'analyse des sondages effecturés au cours de quinze mois à partir de la Station Scientifique du Val-Joyeux près de Paris, montre que les couches où la pression partielle d'ozone est maximale ne sont pas celles où la température est maximale. La pression partielle d'ozone de ces couches n'est pas en relation avec la température de la tropopause, mais est conditionnée par la position géographique sur l'Europe du plus proche thalweg.L'épaisseur réduite totale d'ozone est indépendante de la direction du flux à 100mb, mais présente une relation non linéaire avec l'altitude de la deuxieme tropopause.L'existence d'une relation entre l'allure de la courbe de répartition verticale de l'ozone et la situation météorologique au niveau du sol quarte jours après le sondage, est mise en évidence.
Summary An analysis of the soundings launched at the Val-Joyeux Scientific Station during 15 months shows that the layers containing higher ozone partial pressure are not those of higher absolute temperature. Their ozone pressure has no relation with the temperature of the tropopause but is conditioned by the position of Europe nearest through.The total ozone amounts are independent of the direction of the 100-mb flow but present a non-linear correlation with the second tropopause height.The existence of certain relations between ozone vertical profiles and the meteorological situation at the surface four days after the sounding is pointed out.相似文献
87.
Leonardo Alvarez Julio García Franco Vaccari Giuliano F. Panza Bertha González Carmen Reyes Bárbara Fernández Ramón Pico José A. Zapata Enrique Arango 《Pure and Applied Geophysics》2004,161(5-6):1041-1059
— The expected ground motion in Santiago de Cuba basin from earthquakes which occurred in the Oriente fault zone is studied. Synthetic SH-waves seismograms have been calculated along four profiles in the basin by the hybrid approach (modal summation for the path source-profile and finite differences for the profile) for a maximum frequency of 1 Hz. The response spectra ratio (RSR) has been determined in 49 sites, distributed along all considered profiles with a spacing of 900 m. The corresponding RSR versus frequency curves have been classified using a logical-combinatorial algorithm. The results of the classification, in combination with the uppermost geological setting (geotechnical information and geological geometry of the subsoil) are used for the seismic zoning of the city. Three different main zones are identified, and a small sector characterized by major resonance effects, due to the particular structural conditions. Each zone is characterized in terms of its expected ground motion parameters for the most probable strong earthquake (MS=7), and for the maximum possible (MS=8). 相似文献
88.
Bryn Hubbard Andrew Heald John M. Reynolds Duncan Quincey Shaun D. Richardson Marco Zapata Luyo Nelson Santillan Portilla Michael J. Hambrey 《地球表面变化过程与地形》2005,30(10):1251-1264
Moraines that dam proglacial lakes pose an increasing hazard to communities in the Andes and other mountain ranges. The moraines are prone to failure through collapse, overtopping by lake waters or the effect of displacement waves resulting from ice and rock avalanches. Resulting floods have led to the loss of thousands of lives in the Cordillera Blanca mountains of Peru alone in the last 100 years. On 22 April 2002 a rock avalanche occurred immediately to the south‐west of Laguna Safuna Alta, in the Cordillera Blanca. The geomorphic evidence for the nature, magnitude and consequences of this event was investigated in August 2002. Field mapping indicated that the avalanche deposited 8–20 × 106 m3 of rock into the lake and onto the surface of the frontal region of Glaciar Pucajirca, which flows into the lake. Repeated bathymetric surveying indicated that ~5 × 106 m3 of this material was deposited directly into the lake. The immediate effect of this event was to create a displacement wave that gained in height as it travelled along the lake basin, overtopping the impounding moraine at the lake's northern end. To achieve overtopping, the maximum wave height must have been greater than 100 m. This, and subsequent seiche waves, caused extensive erosion of both the proximal and distal faces of the impounding terminal moraine. Further deep gullying of the distal face of this moraine resulted from the supply of pressurized water to the face via a relief overflow tunnel constructed in 1978. Two‐dimensional, steady‐state analysis of the stability of the post‐avalanche moraine rampart indicates that its proximal face remains susceptible to major large‐scale rotational failure. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
89.
Carolyn Lampe Kristijan Kornpihl Simone Sciamanna Toms Zapata Gonzalo Zamora Roberto Varad 《Journal of Geochemical Exploration》2006,89(1-3):201
A roughly 30 km 2D section across the Faja Plegada y Corrida del Agrio in the Neuquen Basin, Argentina, is the basis for a petroleum systems study, including structural restoration through time, deposition and erosion, pressure, temperature and migration modeling. Integrating tectonic and petroleum systems modeling proved critical to properly evaluate sub-thrust plays. Multi-dimensional modeling of dynamic processes allows accurate assessment and prediction of the potential of petroleum systems in tectonically complex areas such as the Neuquen Basin. 相似文献
90.
P. A. Hernández N. M. Pérez J. C. Varekamp B. Henriquez A. Hernández J. Barrancos E. Padrón D. Calvo G. Melián 《Pure and Applied Geophysics》2007,164(12):2507-2522
A sudden eruption at Santa Ana occurred on 1 October 2005, producing an ash-and-gas plume to a height in excess of 10 km above
the volcano. Several days before, thermal infrared images of the crater provided precursory signals of the eruption. A significant
increase in the extent and intensity of the fumarolic field inside the crater rim and of the surface temperature of the crater’s
lake was observed. Changes in energy input was also estimated to explain the increase in lake temperature based on energy/mass
balance calculations. 相似文献