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921.
Irena Ciglenečki Srđan Pichler Esad Prohić Božena Ćosović 《Water, Air, & Soil Pollution: Focus》2006,6(5-6):537-545
Geochemical, mineralogical and sedimentological analyses were carried out to contrast two different sites (respectively characterized
by permanently oxic and anoxic conditions) in a small, meromictic, seawater lake. In fact, due to relatively high organic
matter content, and reduced water exchange, the Rogoznica Lake has almost permanent anoxic conditions below the depth of 12 m,
where sediment can be considered an anoxic–sulphidic sedimentary environment. Different water column and sediments redox conditions
affect the distribution and speciation of major redox-sensitive metals (Fe, Mn, Mo), reduced sulphur species (RSS) and dissolved
organic C (DOC). Trace metals, especially those that accumulate in anoxic–sulphidic environments (Fe, Mo) showed a marked
enrichment in the solid phase, whereas the low solubility of sulphides leads to low porewater concentrations. The relatively
high sedimentary enrichment of Mo (up to 81 mg/kg) also confirms highly anoxic conditions within the Rogoznica Lake sediments.
Results clearly show that chemical species within the sediments will tend towards equilibrium between porewater and solid
phase according the prevailing environment conditions such as redox, pH, salinity, DOC. 相似文献
922.
Cohesive sediments besides their typical heterogeneity are characterised by structural discontinuity. Particularly, organic
consolidated muds are a good example of sediments that consist of vast aggregates, pore water and gaseous products. The texture
of a cohesive sediment bed is a result of a number of mutually affecting factors, such as deposition history, mineral and
organic composition, kind of biota and oxygen uptake. The presented work attempts to quantify the effect of sediment physical
properties and sediments structure on the sediment erosion potential, considering incipient motion and erosion rate. This
quantification is made on the basis of comparative testing of both unremoulded and remoulded samples of a river mud. Due attention
is paid to sediment handling to preserve the delicate structure of the sediment for the laboratory experiments. Mud with two
degrees of consolidation has been examined in a tilting flume under different flow situations. The test results show a typical
increase of erosion strength with dry matter concentration of the mud. It has also been found that the structural properties
increase the erosion strength for the less consolidated mud. An opposite effect has been recorded for a more consolidated
deposit. As a consequence, due to the sediment structure, the original beds differ much less in erosion resistance in relation
to the dry mass concentration than their disturbed analogues. Finally, the erosion resistance of the examined mud is compared
with data from the literature. 相似文献
923.
W. H. Blake R. P. D. Walsh A. M. Sayer K. Bidin 《Water, Air, & Soil Pollution: Focus》2006,6(5-6):615-623
Detailed information on post-logging sediment dynamics in tropical catchments is required for modelling downstream impacts
on communities and ecosystems. Sediment tracing methods, which are potentially useful in extending to the large catchment
scale and longer time scales, are tested in primary and selectively logged rainforest catchments of Sabah, Borneo. Selected
nutrient (P and N) and trace metal (Ni and Zn) concentrations are shown to discriminate surface, shallow subsurface and deep
subsurface sediment sources. Analysis of channel-stored fine-sediment samples and use of an unmixing model allow the relative
importance of these vertical sediment sources to be estimated and erosion processes to be inferred for catchments of contrasting
size. 相似文献
924.
A benthic in situ flume and a 1D biogeochemical sediment model to evaluate solute fluxes across the sediment–water interface have been developed.
The flume was successfully used to determine oxygen and nutrient fluxes at various locations of the Neckar River in Germany.
The experimental results were linked with vertical pore water concentration profiles and independently verified with the model.
By combining experimental and model results we assessed the influence of dissolved oxygen concentrations in the water column
and the availability of degradable organic matter on sediment oxygen demand. The results and the derived relations can be
used to parameterize the sediment module of large scale water quality models, allowing one to assess the influence of sediment–water
interactions on various aspects of river water quality. Moreover, the biogeochemical sediment model can help to improve the
general understanding of the processes governing solute concentrations and fluxes in sediments and across their interfaces. 相似文献
925.
Ester Heath Nives Ogrinc Jadran Faganeli Stefano Covelli 《Water, Air, & Soil Pollution: Focus》2006,6(5-6):605-614
To reconstruct a history of polycyclic aromatic hydrocarbon (PAH) pollution in the Gulf of Trieste, one of the largest urbanized
areas in the Adriatic Sea, we analyzed three long sediment cores collected between 1996 and 1997. Concentrations of total
PAHs, the sum of 16 PAH compounds and six of their methylated analogues, in all three cores show a decrease from 600–800 ng
g−1, at the surface, to levels below 250 ng g−1 in deepest layers (down to 3 m). The same trend was shown with separate representative pyrogenic PAHs (pyrene, benzofluoranthene
and phenanthrene). Using Hg as a recent geochronological tracer, we observe an increasing input of PAHs since the beginning
of the 20th Century and, especially, after the Second World War coinciding with increasing industrialization and urbanization
of the region. This correlation is supported by PAH ratios that are indication of combustion processes and represent a marker
for anthropogenic inputs. No correlation exists between PAHs and black carbon within the core profiles, indicating two different
fractions of the ‘black carbon continuum’. 相似文献
926.
Rasmus B. Lauridsen Brian Kronvang Nikolai Friberg 《Water, Air, & Soil Pollution: Focus》2006,6(5-6):423-432
In a total of 189 water samples collected from Danish streams no traces of the pyrethroid esfenvalerate were detected. However,
pyrethroids have previously been found in sediments in 9 out of 30 streams investigated. We found that the shredding activity
of the Trichopteran Sericostoma personatum and the amphipod Gammarus pulex was significantly reduced with increased concentration of the pyrethroid lambda-cyhalohtrin adsorbed to the leaves on which
they fed. Predation rate on the Plecopteran Leuctra nigra by the leech Erpobdella octoculata increased significantly with increasing concentration of lambda-cyhalothrin on the leaves on which L. nigra was fed. Our results clearly indicate that the ongoing monitoring of pesticides is likely to underestimate pyrethroid occurrence
and that sediment-bound pyrethroids have a potential negative impact on ecosystem function and biotic interactions in streams. 相似文献
927.
底泥疏浚是清除江河湖库内源污染的重要措施,其疏浚方案的制定有其重要的内涵,应对疏挖深度、疏挖形式、疏浚设备、底泥处置等问题给予科学的分析,真正实现通过疏浚改善水环境的目标,并能为进一步修复和重建良好的水生态系统创造条件。对疏浚可能带来的不利影响及疏浚效果欠佳的可能原因等进行了一定的分析。 相似文献
928.
ESTIMATING TMDL BACKGROUND SUSPENDED SEDIMENT LOADING TO GREAT LAKES TRIBUTARIES FROM EXISTING DATA1
Peter J. Whiting 《Journal of the American Water Resources Association》2006,42(3):769-776
ABSTRACT: The total maximum daily load (TMDL) for suspended sediment is the maximum quantity of suspended sediment that can enter a waterway without affecting the beneficial uses of the waterway. It is calculated as the sum of permissible allotments of point sources of suspended sediment, permissible allotments of nonpoint sources of suspended sediment, background (natural) loading of suspended sediment, and a margin of safety. The goal of this project was to develop methods for estimating background levels of sediment loads in tributaries of the Great Lakes. Such quantification is key to determining permissible TMDL in waters that do not meet water quality standards under the Clean Water Act of 1972. Suspended sediment loading for 46 rivers was estimated from data collected at U.S. Geological Survey (USGS) gages. Land use and physiographic attributes were estimated for these gaged basins with a geographic information system (GIS). Basin attributes and sediment yield data are the basis for examining two approaches to estimating background suspended sediment loads. One method, based upon envelope curves of sediment yield and drainage area, will be shown to have considerable merit. A second method, based upon correlation of sediment yield to various basin attributes such as drainage area and land use, will be shown to be fraught with difficulties. 相似文献
929.
Steven W. Effler David A. Matthews Josef W. Kaser Anthony R. Prestigiacomo David G. Smith 《Journal of the American Water Resources Association》2006,42(6):1697-1710
Abstract: The impacts of runoff events on external suspended solids loading to Schoharie Reservoir, New York, and patterns of light scattering and sediment deposition in this reservoir are assessed. The assessment is based on monitoring of suspended solids concentrations in the reservoir's primary tributary, detailed vertical profiles of optical backscattering (a surrogate measure of light scattering) in the reservoir water column, and analysis of sediment trap collections, over a seven-month interval of high runoff. These impacts are reported to be tightly temporally coupled and strongly positively related to the magnitude of runoff events. The primary tributary entered the reservoir as a plunging inflow during runoff events, causing conspicuous subsurface peaks in light scattering, with vertical patterns that varied strongly for different events. Deposition quantified by near-bottom trap deployments is reported to be more representative than results from metalimnetic deployments that were generally within, rather than below, the turbid layers. Direct inputs of sediment, transported by density currents, are found to drive deposition, rather than resuspension/redeposition. More than 50 percent of the reported deposition occurred in less than 15 percent of the study period, associated with the four largest runoff events. 相似文献
930.
Richard A. McLaughlin Tabitha T. Brown 《Journal of the American Water Resources Association》2006,42(3):675-684
ABSTRACT: Polyacrylamide (PAM) has been demonstrated to greatly reduce erosion in furrow irrigation, but much less is known about its effectiveness on the much steeper slopes typical of construction sites. The purpose of this study was to determine if anionic PAM would enhance erosion control either alone on bare soil or in combination with four types of ground covers commonly used for grass establishment: straw, straw erosion control blanket (ECB), wood fiber, and mechanically bonded fiber matrix (MBFM). Tests were conducted under natural rainfall and vegetation on a 4 percent slope (bare soil, straw, ECB, and MBFM) or using a rainfall simulator (bare soil, straw, wood fiber, MBFM) on either 10 percent or 20 percent slope on three different soil substrates. All ground cover treatments were evaluated with and without PAM applied in solution at 19 kg/ha. The straw, ECB, and MBFM significantly reduced runoff volume, average turbidity, and total sediment lost over five rainfall events on the vegetated plots. The addition of PAM to ground covers only occasionally had significant effects on runoff parameters but did significantly increase vegetative coverage overall. The rainfall simulator tests produced similar results after four events, with the straw, wood fiber, and MBFM all having significantly lower turbidity than the bare soil. The PAM significantly reduced turbidity for both the first and second events but did not consistently improve runoff quality after multiple rainfall events for any ground cover‐soil combinations tested. Separate tests of PAM applied before or after straw did not indicate a clear advantage of either approach, but runoff turbidity was often significantly reduced with PAM, especially at the 20 percent slope. Turbidity reductions were attributed to flocculation of eroded sediment. 相似文献