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31.
Jorge Yáñez Marjory Guajardo Cristian Miranda César Soto Héctor D. Mansilla A. Russell Flegal 《Marine pollution bulletin》2013
Anomalously high levels of mercury in sediment in the Lenga estuary, Chile are comparable to the most contaminated sites previously reported elsewhere. Total mercury (Hgtotal) concentrations range from 0.5 to 129 mg kg−1 and organic mercury (Hgorg) from 11 to 53 μg kg−1. The highest levels are in areas near the previous wastewater outfall of a chlo-alkali plant. The results show that the proportion of Hgorg/Hgtotal in the sediment varies by more than two orders of magnitude (0.02–5.7%) according to the concentration of Hgtotal. No correlation between the concentration of Hgorg and Hgtotal was found. The lack of correlation does contrast with the findings of other authors in culture media. Our results indicate that even at very high concentrations of Hgtotal and organic matter do not influence organic mercury formation in estuary sediments. The disparity in Hgtotal and Hgorg concentrations also attests to environmental differences in the formation. 相似文献
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Natural Hazards - As a result of the massive deforestation and windfalling in Romania last year, catastrophic floods frequently occur with historic high-water marks only to be registered every 500... 相似文献
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We studied, separately, the effect of the cladocerans Alona glabra and Macrothrix triserialis on the population growth of the rotifer Euchlanis dilatata using three different food types (Chlorella and Scenedesmus, live or dead, offered on a comparable dry weight basis, 3.16 μg C ml−1). Regardless of the presence or absence of competition, E. dilatata cultured using Chlorella (live or dead) showed a higher population growth as compared to Scenedesmus. Compared to heat-killed C. vulgaris, E. dilatata cultured alone and fed on live algae reached higher abundances. Both cladoceran species had an adverse effect on the population growth of Euchlanis, but did not eliminate the rotifers. Of the two cladocerans, M. triserialis had a far more adverse effect on the population densities of E. dilatata as compared to A. glabra. E. dilatata also influenced the population growth of A. glabra and M. triserialis, the former being more adversely affected than the latter. When the egg ratios of E. dilatata were plotted as a function of population density, a significantly inverse relation was obtained only in treatments containing Chlorella but not for other treatments. Statistically the rate of population increase (r) per day of E. dilatata was adversely affected by the diet type and the presence of competing species. The interaction of diet type X competition was also significant. For A. glabra, the presence of E. dilatata and the diet type, but not their interaction, significantly influenced the r. On the other hand for M. triserialis, only the diet type was significant. Our results suggest that the competitive outcome between rotifers and cladocerans was dependent on diet type. 相似文献
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Diana Jordanova Petar Petrov Viktor Hoffmann Tilman Gocht Cristian Panaiotu Tsenka Tsacheva Neli Jordanova 《Studia Geophysica et Geodaetica》2010,54(3):417-442
Detailed magnetic study on vegetation samples from several strongly polluted and clean sites in Bulgaria is carried out in
order to evaluate suitability of different species as passive dust collectors in magnetometry. From each location, available
species among lichens, mosses, poplar leaves, dandelion, needles have been sampled. Magnetic susceptibility calculated on
mass-specific basis shows wide variability between diamagnetic signal up to 846 × 10−8 m3/kg. Lichens and mosses are found to be the species, showing magnetic signals with the strongest contrast between clean and
polluted environment. The main magnetic phase is magnetite-like according to the results from thermomagnetic analysis of susceptibility
on magnetic extracts. Scanning electron microscopy (SEM) microphotographs reveal the presence of abundant particulate matter
on vegetation surface both with anthropogenic (spherules) and lithogenic origin. Magnetic grain size deduced by the ratio
of saturation remanent magnetization (SIRM) and mass-specific magnetic susceptibility (χ) and coercivities (Bc and Bcr) suggest that different species accumulate preferentially small SD-like grains from pollution emissions. Contrasting relationship
of the ratio of anhysteretic remanent magnetization (ARM) and χ for polluted vs clean sites deduced by needles and lichens
may be related to transformation of the accumulated dust particles within lichens’ tissue. This finding indicates that the
exact species used as biological dust collector is of importance when studying spatial grain size distribution of magnetic
dust particles. Pilot study on polycyclic aromatic hydrocarbons (PAH) content and its relation to magnetic parameters shows
good correspondence between high levels of PAHs and high SIRM values for locations affected by non-ferrous industrial production. 相似文献
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Natural Hazards - Empirical relationships between MSK macroseismic intensity and several engineering ground motion parameters are developed using the macroseismic and instrumental data available... 相似文献
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We investigated the relative distribution of allochthonous (i.e., terrigenous) organic matter in the complex, continuous, river–fjord–sound–channel–gulf system of Chile’s North Patagonia (41.5–46.5°S) in order to establish whether this organic matter can reach the open ocean or whether it is largely retained near its fluvial sources. Grain size distribution, total organic carbon and total nitrogen contents, and carbon stable isotope contents (δ13C) were quantified in 53 surface sediment samples collected during the CIMAR Fiordos cruises 1, 4, 8, and 10, as were salinity and silicic acid concentrations in the surface waters. A principal component analysis segregated the Chiloé and Aysén interior seas into two zones: (i) the continental fjords, with sediment enriched in allochthonous organic matter, having higher C:N molar ratios (10–14) and lower δ13C composition (?23‰ to ?27‰); and (ii) the channels and gulfs, with a prevalent autochthonous marine source, having lower C:N values (6–10) and higher δ13C composition (?20‰ to ?23‰). Estuarine waters with low salinity (2–30) and high silicic acid (10–90 μM) were associated with high C:N ratios and low δ13C in surface sediments, meaning that terrestrial organic matter was transported up to the mouth of the continental fjords. A two-source mixing model confirmed that allochthonous (terrestrial) organic matter contents (50–90%) associated with local river discharges were present within the continental fjords. On the contrary, autochthonous (marine) organic matter was prevalent (50–90%) at the sites in the marine influenced channels, sounds, and gulfs. 相似文献