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121.
We have shown that municipal wastewater and sewage sludge are contaminated by organotins. Here, we investigate the behaviour and fate of tributyltin (TBT) in laboratory-scale sewage sludge treatment at various conditions including both aerobic and anaerobic, and mesophilic and thermophilic. Organotins were determined by capillary GC-FPD. Fresh raw sewage sludge was stored in a tank that was connected to five chemostats maintained at different conditions. Raw sludge contained TBT, dibutyltin (DBT) and monobutyltin (MBT) residues in the range of 0·28 to 0·83 mg/kg (dry weight). The volumetric TBT concentration was 10·5 μg/litre in the influent, and ranged from 7·4 to 8·3 μg/litre in the effluent of the different chemostats. In the anaerobic mesophilic treatment, concentrations of TBT did not decrease with increasing sludge residence time, DBT increased and MBT showed no clear trend. The DBT increase is suggested to be due to leaching from the PVC walls of the chemostats, and not to degradation of TBT alone. The TBT reduction did not show significant differences between the mesophilic and thermophilic anaerobic fermentors. These findings indicate that the degradation of TBT during sludge treatment is only low under all conditions tested. 相似文献
122.
The loss of coherence of seismic waves, even over small distances, can become significant and consequently important for engineering applications. This coherence loss depends on several parameters (frequency, inter-station distance), but their dependencies are not well understood yet. We show the results of a detailed analysis of the spatial variability of the coherence between two signals. This analysis is based on a simple model which is an exponential function of inter-station distance and frequency. Data from a temporary network of 36 weak-motion instruments installed at the EURO-SEISTEST site, north-east of Thessaloniki (Greece), is used in this work. The data offers the unique possibility to study the loss of coherence over a wide range of distances, as the inter-station distances are between 8 m and 5488 m. We test the influence on the coherence of the length of the time-window of the signals, of the type of the waves present in the time-window and of the common energy of the signals. We also show that, at least at this particular site, the loss of coherence with distance is probably marked by a "cross over" distance, distinguishing two different ranges: one for inter-station distances up to 100 m and the other above 100 m. Finally, we find that the coherence determined from noise recordings behaves in a rather similar way to the one determined from coda-waves and more stationary (longer) signals. Therefore, noise can be useful for a rough, but quick estimation of the loss of coherence, at least for inter-station distances larger than 100 m. 相似文献
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Aaron Zimmerman Holly J. Stein Judith L. Hannah Dejan Koželj Kamen Bogdanov Tudor Berza 《Mineralium Deposita》2008,43(1):1-21
The Apuseni–Banat–Timok–Srednogorie magmatic–metallogenic belt (ABTS belt), forms a substantial metallogenic province in the
Balkan-South Carpathian system in southeastern Europe. The belt hosts porphyry, skarn, and epithermal deposits mined since
pre-Roman times. Generally, the deposits, prospects, and occurrences within the belt are linked to magmatic centers of calc-alkaline
affinity. Fifty-one rhenium-osmium (Re–Os) ages and Re concentration data for molybdenites define systematic geochronologic
trends and constrain the geochemical-metallogenic evolution of the belt in space and time. From these data and additional
existing geologic-geochemical data, a general tectonic history for the belt is proposed. Mineralization ages in Apuseni-Banat,
Timok, and Panagyurishte (the central district of the larger E–W Srednogorie Zone) range from 72–83, 81–88, and 87–92 Ma,
respectively, and clearly document increasing age from the northwestern districts to the southeastern districts. Further,
Re–Os ages suggest rapidly migrating pulses of Late Cretaceous magmatic–hydrothermal activity with construction of deposits
in ~1 m.y., districts in ~10 m.y., and the entire 1,500 km belt in ~20 m.y. Ages in both Timok and Panagyurishte show systematic
younging, while deposit ages in Banat and Apuseni are less systematic reflecting a restricted evolution of the tectonic system.
Systematic differences are also observed for molybdenite Re concentrations on the belt scale. Re concentrations generally
range from hundreds to thousands of parts per million, typical of subduction-related Cu–Au–Mo–(PGE) porphyry systems associated
with the generation of juvenile crust. The geochronologic and geochemical trends are compatible with proposed steepening of
subducting oceanic slab and relaxation of upper continental plate compression. Resulting influx of sub-continental mantle
lithosphere (SCML) and asthenosphere provide a fertile metal source and heat, while the subducting slab contributes connate
and mineral dehydration fluids, which facilitate partial melting and metal leaching of SCML and asthenosphere. Cu–Au–Mo–(PGE)
porphyry deposits may develop where melts are trapped at shallow crustal levels, often with associated volcanism and epithermal-style
deposits (South Banat, Timok, and Panagyurishte). Mo–Fe–Pb–Zn skarn deposits may develop where felsic melts are trapped adjacent
to Mesozoic limestones at moderate crustal levels (North Banat and Apuseni). Systematic spatial variations in deposit style,
commodity enrichment, Re–Os ages, and Re concentrations support specific tectonic processes that led to ore formation. In
a post-collisional setting, subduction of Vardar oceanic crust may have stalled, causing slab steepening and rollback. The
slab rollback relaxes compression, facilitating and enhancing orogenic collapse of previously thickened Balkan-South Carpathian
crust. The progression of coupled rollback-orogenic collapse is evidenced by the width of Late Cretaceous extensional basins
and northward younging of Re–Os ages, from Panagyurishte (~60 km; 92–87 Ma) to Timok (~20 km; 88–81 Ma) to Apuseni-Banat (~5 km;
83–72 Ma). Generation of a well-endowed mineral belt, such as the ABTS, requires a temporally and spatially restricted window
of magmatic–hydrothermal activity. This window is quickly opened as upper plate compression relaxes, thereby inducing melt
generation and ingress of melt to higher crustal levels. The window is just as quickly closed as upper plate compression is
reinstated. The transient tectonic state responsible for economic mineralization in the ABTS belt may be a paleo-analogue
to transient intervals in the present subduction tectonics of SE Asia where much mineral wealth has been created in the last
few million years. 相似文献
127.
A field experiment was established in Bocas Del Toro, Panama to examine the relationship between sessile organisms living
on mangrove prop roots and fish communities. Artificial mangrove roots (AMR) with different sets of artificial (AE) or real
epibionts were established in five different locations in two separate years. Fish species in each plot were identified, counted,
and their size estimated by visual census for 15 days in each replicate. In the artificial mangrove plots, the treatments
with the most heterogeneous structure had significantly greater abundance of most families and species richness of fish in
both years of the experiment. AMR plots with AEs attracted a more abundant and diverse fish assemblage than those with live
epibionts, which had lower three-dimensional structure. All of the AMR plots had significantly greater fish abundance than
comparable plots of sea grass alone. The location of the replicate also made a significant difference to fish abundance. The
data indicate that prop-root epibionts can enhance fish abundance and diversity in mangroves, although the relationship may
depend on the specific nature of the epibionts and fishes present. 相似文献
128.
Konstantin Kröniger Frederik De Roo Peter Brugger Sadiq Huq Tirtha Banerjee Judith Zinsser Eyal Rotenberg Dan Yakir Shani Rohatyn Matthias Mauder 《Boundary-Layer Meteorology》2018,169(2):209-232
Afforestation in semi-arid regions can potentially enhance the global carbon sink by increasing the terrestrial biomass. However, the survival of planted forests under such extreme environmental conditions is not guaranteed a priori, and critically depends on the surface–atmosphere exchange of energy. We investigate the pine forest Yatir in Israel, an example of a man-made semi-arid ecosystem, by means of large-eddy simulations. We focus on the interaction between surface–atmosphere exchange and secondary circulations that couple the isolated forest to the surrounding shrubland. The large-eddy simulations feature a grid resolution that resolves the forest canopy in several layers, and are initialized by satellite data and Doppler lidar, eddy-covariance and radiosonde measurements. We perform three large-eddy simulations with different geostrophic wind speeds to investigate the influence of those wind speeds on the surface–atmosphere exchange. We reproduce the measured mean updrafts above the forest and mean downdrafts above the shrubland, which increase in strength with decreasing geostrophic wind speed. The largest updrafts emerge above the older, denser part of the forest, triggering secondary circulations. The spatial extent of these circulations does not cover the entire forest area, although we observe a reduced aerodynamic resistance in the regions of updraft. Our simulations indicate that the enhanced surface–atmosphere exchange of the Yatir forest is not sufficient to compensate for the increased net radiation, due to the lower albedo of the forest with respect to the surroundings, resulting in higher air temperatures inside the forest. However, the difference between the forest and shrubland temperatures decreases with increasing geostrophic wind speed due to reduction in the aerodynamic resistance. 相似文献
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