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41.
Rodrigo L. Moura Ronaldo B. Francini-Filho Eduardo M. Chaves Carolina V. Minte-Vera Kenyon C. Lindeman 《Estuarine, Coastal and Shelf Science》2011
The early life history of Western Atlantic snappers from the Southern hemisphere is largely unknown. Habitat use of different life stages (i.e. size categories) of the dog snapper (Lutjanus jocu) was examined across the largest South Atlantic reef–estuarine complex (Abrolhos Shelf, Brazil, 16–19° S). Visual surveys were conducted in different habitats across the shelf (estuary, inner-shelf reefs and mid-shelf reefs). Lutjanus jocu showed higher densities on inner-shelf habitats, with a clear increase in fish size across the shelf. Individuals <7 cm were associated with both the estuary (mangrove and rocky habitats) and inner-shelf reefs (particularly shallow fore-reefs and tide pools). Individuals ranging 10–30 cm were broadly distributed, but consistently more abundant on inner-shelf reefs. Individuals between 30 and 40 cm were more common on mid-shelf reefs, while individuals >40 cm were recorded only on mid-shelf reefs. Literature data indicate that individuals ranging 70–80 cm are common on deep offshore reefs. This pattern suggests that the dog snapper performs ontogenetic cross-shelf migrations. Protecting portions of the different habitats used by the dog snapper during its post-settlement life cycle is highlighted as an important conservation and management measure. 相似文献
42.
J.CRAIG HAMILTON Shared Research Resource Laboratories School of Medicine East Carolina University Greenville NC U.S.A.PAUL J.GEMPERLINE Department of Chemistry East Carolina University Greenville NC U.S.A. 《地理学报(英文版)》1990,(1)
One of the major applications of factor analysis in the chemical literature,self-modeling curve resolution(SMCR),is covered in this review,including a historical account of the inethods derived from Lawtonand Sylvestre's original method.Papers treating the theory or applications of SMCR are included.Qualitative and quantitative applications are described where appropriate. 相似文献
43.
Anthropogenic activities have become an important source of heavy metals to the marine environments. Biological sentinels like seabirds’ chicks have been widely used to monitorize the levels of some heavy metals. Due to its mainly marine foraging habits, Audouin’s gull fits well for this purpose. Mercury and lead levels were measured in mantle feathers of Audouin’s gull chicks from two colonies in NE Iberian Peninsula: the Ebro Delta and the Llobregat Delta. Both are anthropized areas subject to differential pollutant inputs. Lead levels were significantly higher in the Llobregat Delta probably due to the use of leaded fuel in the nearby Barcelona airport. On the other side, mercury concentrations were higher in the Ebro Delta, in relation with the disposal of the toxic sediments at the Flix site carried down by the Ebro River. These mercury levels in the Ebro chicks reached values that have been described as toxic. 相似文献
44.
Carolina Montero‐López Manfred R. Strecker Taylor F. Schildgen Fernando Hongn Silvina Guzmán Bodo Bookhagen Masafumi Sudo 《地学学报》2014,26(6):454-460
A valley‐filling ignimbrite re‐exposed through subsequent river incision at the southern margin of the Andean (Puna) plateau preserves pristine geological evidence of pre‐late Miocene palaeotopography in the north western Argentine Andes. Our new 40Ar/39Ar dating of the Las Papas Ignimbrites yields a plateau age of 9.24 ± 0.03 Ma, indicating valley‐relief and orographic‐barrier conditions comparable to the present‐day. A later infill of Plio–Pleistocene coarse conglomerates has been linked to wetter conditions, but resulted in no additional net incision of the Las Papas valley, considering that the base of the ignimbrite remains unexposed in the valley bottom. Our observations indicate that at least 550 m of local plateau margin relief (and likely >2 km) existed by 9 Ma at the southern Puna margin, which likely aided the efficiency of the orographic barrier to rainfall along the eastern and south eastern flanks of the Puna and causes aridity in the plateau interior. 相似文献
45.
Organic carbon,phosphorus and nitrogen in surface sediments of the marine-coastal region north and south of the Paria Peninsula,Venezuela 总被引:2,自引:1,他引:1
The organic carbon, phosphorus and nitrogen content of silt and clay fractions of surface sediments from the marine-coastal
region north and south of the Paria Peninsula (PP) were quantified. Organic carbon concentrations (Corg) were determined by
dry combustion after decarbonation with 10% hydrochloric acid, and total phosphorus (TP) and total nitrogen (TN). This information
was then used to produce maps of the iso-concentrations of the distribution of these elements in the sub-marine continental
shelf north of the PP and in the Gulf of Paria (GP). In the silt fraction, the Corg concentration, TP and TN showed average
values of 1.53, 0.04 and 0.03%, respectively. The highest Corg, PT and NT values were recorded from silts from the PP with
a gradual increase towards the west and the lowest figures were found in the GP. In the clay fraction, Corg, TN and TP had
mean values of 1.64, 0.13 and 0.04%, respectively, and showed a spatial distribution very similar to the silt fraction, indicating
the influence of ocean currents and coastal upwelling patterns. The C/N ratio had an average of 23.67 and showed that the
Corg present in the PP sediments is of marine origin, resulting from primary productivity, especially towards the west. This
zone has been identified as the most productive in this region due to coastal upwelling and the influence of the Orinoco and
Amazon rivers (Gomez 1996; Monente 1997). In contrast, a greater variability in the parameters measured was found in the GP sediments, probably due to the mixing
of marine and continental Corg, confirming the influence of the Orinoco and Amazon waters brought by the Guyana Current. 相似文献
46.
Ana Carolina Ruiz-Fernández Mario Sprovieri Mauro Frignani Joan Albert Sanchez-Cabeza Maria Luisa Feo Luca Giorgio Bellucci Libia Hascibe Pérez-Bernal Michel Preda María Luisa Machain-Castillo 《Environmental Earth Sciences》2012,67(3):727-742
The Isthmus of Tehuantepec corresponds to the shortest distance (~200?km) between the Gulf of Mexico and the Pacific Ocean in Southern Mexico, and the main economical activity of this region is oil extraction and refining. Polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPHs) were determined in a 210Pb dated sediment core collected from the continental shelf of Tehuantepec Gulf, in the vicinity of the oil refinery of Salina Cruz, Oaxaca, the main oil refining facility of the country. The sediments were mostly of coarse nature and hence PAHs and TPHs concentrations throughout the core (61?C404???g?g?1 and 29?C154?mg?kg?1, respectively) were below international quality benchmarks. Depth profiles of both PAHs and TPHs concentrations showed increasing trends since the early 1900s but the higher values were found from the 1950s to present. PAH congener ratios showed that these contaminants had both petrogenic and pyrolitic sources, although the former has been predominant since the 1970s. The Salina Cruz refinery started operations in 1978 but the oil industry activities in the Tehuantepec Isthmus go back to the beginning of the twentieth century with the operation of Minatitlan refinery in the Gulf of Mexico, and the Gulf of Tehuantepec being the main conduit for oil distribution in the Pacific coast. The observed changes in contaminant distributions described well the oil industry development in the area. 相似文献
47.
Maria Carolina de Morais Paulo Pereira Martins Junior Waldir Renato Paradella 《Environmental Earth Sciences》2012,66(7):2085-2096
Mining activities cause a wide range of changes to the environment, substantially affecting both the physical and biological
environmental sectors. In the Carajás Mineral Province, located in the Amazon rainforest, environmental regulations tend to
be more rigorous, due to the fragility of the environment in which large iron deposits are found. The characterization of
the impact of mining on environment considers: the type and extent of the impact, the physical chemistry differences and similarities
of the mineral deposits, the deposit size, the adopted mining process, and the environment (both natural and economic) in
which the mining process was developed. Remote sensing technology is utilized in this study, in particular, the use of ortho-aerial
photograph, and optical and radar images with distinct spatial resolution. These permit the elaboration in synoptic maps,
multi-scale and dynamic, of the changes wrought upon the environment: deforestation, removal of vegetation cover, topographic
surface and landscape alteration, and slope instabilities among others. In this aspect, determining the extent of influence
of the mining activity is directly tied to the characterization of its impact on various natural systems at the observed scale,
and not by simply defining a predetermined Euclidean distance. The results showed that remote sensing technology, optical
and radar images, proved to be efficient in the study of environmental information and the areas of influence on the semi-regional
and local scales in the Amazon forest. 相似文献
48.
49.
Jeroen Ritsema Wenbo Xu Lars Stixrude Carolina Lithgow-Bertelloni 《Earth and Planetary Science Letters》2009,277(1-2):244-252
Partial melting of mantle peridotite generates a physically and chemically layered oceanic lithosphere that is cycled back into the mantle in subduction zones. Stirring times of the mantle are too long to allow for complete re-homogenization of subducted basalt and harzburgite, given the low chemical diffusivity of the solid mantle. This suggests that the Earth's mantle is a mechanical mixture of basaltic and harzburgitic components. Using a recently developed thermodynamic formulism we determine the phase equilibria and the seismic properties of a mantle comprised of a mechanical mixture of basalt and harzburgite (MM) and a homogeneous mantle (EA) with identical pyrolitic bulk chemistry. We use the theoretical shear velocity profiles as a new thermometer of the mantle below the magma-genetic zone by modeling the difference ΔT410-660 between traveltimes of shear wave reflections off the 410-km and 660-km with the potential temperature TP. ΔT410-660 are measured from waveform stacks. They indicate that, over 1000+ km wave lengths, the temperature varies by about 200 K. Lowest and highest temperatures are resolved for the western Pacific subduction zones and the central Pacific, respectively. This variation is similar for the EA and MM and is in excellent agreement with estimates of transition zone thickness and shear velocity variations. The median value of TP for the EA is 1720 K. It is about 1625 K for the MM, a value that is in better agreement with the Normal-MORB values of 1610 ± 40 K inferred from olivine-liquid equilibria given that our sampling region encompasses the Western Pacific subduction zones and the oldest parts of the Pacific Plate. We argue therefore that a mechanical mixed mantle, with generally higher velocities and steeper velocities gradients, represents a better physical reference model than a model based on a fully equilibrated assemblage. 相似文献
50.
Luca Mao Andrea Dell'Agnese Carolina Huincache Michal Engel Georg Niedrist Francesco Comiti 《地球表面变化过程与地形》2014,39(7):964-976
Sediment transport during flood events often reveals hysteretic patterns because flow discharge can peak before (counterclockwise hysteresis) or after (clockwise hysteresis) the peak of bedload. Hysteresis in sediment transport has been used in the literature to infer the degree of sediment availability. Counterclockwise and clockwise hysteresis have been in fact interpreted as limited and unlimited sediment supply conditions, respectively. Hysteresis has been mainly explored for the case of suspended sediment transport, but it was rarely reported for bedload transport in mountain streams. This work focuses on the temporal variability of bedload transport in an alpine catchment (Saldur basin, 18.6 km2, Italian Alps) where bedload transport was monitored by means of an acoustic pipe sensor which detects the acoustic vibrations induced by particles hitting a 0.5m‐long steel pipe. Runoff dynamics are dominated by snowmelt in late spring/early summer, mostly by glacier melt in late summer/early autumn, and by a combination of the snow and glacier melt in mid‐summer. The results indicate that hysteretic patterns during daily discharge fluctuations are predominantly clockwise during the snowmelt period, likely due to the ready availability of unpacked sediments within the channel or through bank erosion in the lower part of the basin. On the contrary, counterclockwise hysteresis tend to be more frequent during late glacier melting period, possibly due to the time lag needed for sediment provided by the glacial and peri‐glacial area to be transported to the monitoring section. However, intense rainfall events occurring during the glacier melt period generated predominantly clockwise hysteresis, thus indicating the activation of different sediment sources. These results indicate that runoff generation processes play a crucial role on sediment supply and temporal availability in mountain streams. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献