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81.
ABSTRACT: This study was undertaken to investigate the cost effectiveness of selected arsenic avoidance methods. Annual costs of reverse osmosis (RO), activated alumina (AA), bottled water, and rented and purchased water coolers for various household sizes in Maine were compared. Relative ranking of systems shows that RO ($411 annually) is the most cost effective, followed by AA ($518) and one‐gallon jugs of water ($321 to $1,285), respectively, for households larger than one person. One‐gallon jugs ($321) followed by 2.5‐gallon jugs ($358) of water were found to be the most cost effective for households of one person or for households with arsenic III concentrations of 0.02 to 0.06 mg/L and arsenic V concentrations of 0.08 to 1.0 mg/L. Point‐of‐entry systems and water coolers were not found to be cost effective under any of the study's conditions. The research reported here will help states make more definitive treatment recommendations to households regarding the cost effectiveness of alternative treatment systems to reduce arsenic concentrations below 0.01 mg/L. While arsenic removal technologies are improving, which enhances removal rates and reduces costs, the major insights from this analysis appear to be reinforced by technological improvements.  相似文献   
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ABSTRACT: We measured diurnal changes in water levels in three swamps dominated by pondcypress trees (Taxodium distichum var. nuans) in central Florida for four years in order to obtain additional documentation of relatively low evapotranspiration (ET) rates. Two of these swamps were monitored for another three years after one of them was clearcut. Estimated annual ET from undisturbed cypress swamps varied from 38 cm/yr to 86 cm/yr, averaging 60 cm (not including interception). Faster ET rates may have been related to faster pondcypress growth rates, a greater proportion of hardwoods in the canopy, and clearcutting in the surrounding pine plantation. The average ET rate was considerably lower than ET rates that have been estimated for north Florida pine plantations. However, incorporating estimates of interception indicates that overall ET rates in pondcypress swamps may be only slightly lower than ET from pine plantations. ET decreased only 5 percent in one swamp after it was clearcut, indicating that this management practice is not likely to affect regional water balances.  相似文献   
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ABSTRACT: Techniques were developed using vector and raster data in a geographic information system (GIS) to define the spatial variability of watershed characteristics in the north-central Sierra Nevada of California and Nevada and to assist in computing model input parameters. The U.S. Geological Survey's Precipitation-Runoff Modeling System, a physically based, distributed-parameter watershed model, simulates runoff for a basin by partitioning a watershed into areas that each have a homogeneous hydrologic response to precipitation or snowmelt. These land units, known as hydrologic-response units (HRU's), are characterized according to physical properties, such as altitude, slope, aspect, land cover, soils, and geology, and climate patterns. Digital data were used to develop a GIS data base and HRIJ classification for the American River and Carson River basins. The following criteria are used in delineating HRU's: (1) Data layers are hydrologically significant and have a resolution appropriate to the watershed's natural spatial variability, (2) the technique for delineating HRU's accommodates different classification criteria and is reproducible, and (3) HRU's are not limited by hydrographic-subbasin boundaries. HRU's so defined are spatially noncontiguous. The result is an objective, efficient methodology for characterizing a watershed and for delineating HRU's. Also, digital data can be analyzed and transformed to assist in defining parameters and in calibrating the model.  相似文献   
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Environmental consulting is a relatively new and rapidly growing field. It involves traditional engineering and construction risks as well as the specter of potential—and likely uninsured or uninsurable—liability for environmental conditions and professional errors. To succeed in today's litigious society, environmental consultants and contractors need to understand the risks inherent in their work. They must conduct their operations in a manner conducive to quality assurance, risk control, and effective project management. Constant and clear communication with the client is essential to a good working relationship and repeat business. Effective project control, risk management, file documentation, and contract negotiation are critical tools for profitable growth and our professional liability defense.  相似文献   
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We investigated the hypothesis that the endogenous role of the commercially important inducible steroid hydroxylase cytochrome P450s of fungi was in defense against plant toxophores/secondary metabolites. Two plant defense compounds, the aglycones tomatidine and solanidine, the steroidal glycoalkaloid alpha-tomatine and the triterpene saponin beta-escin were tested as inducers of 11beta/14alpha-steroid hydroxylase in the filamentous fungus Cochliobolus lunatus. The extracts of saponins from the roots of Primula veris and green oat leaves were also tested as inducers of 11beta/14alpha-hydroxylation activity in progesterone biotransformation with the same fungus. Induction of steroid hydroxylase and inhibition of activity in some cases support our hypothesis that their endogenous function is in biochemical defence against secondary metabolites. 4-Pregnene-3,11,20-trione was added as a substrate for biotransformation with C. lunatus. We isolated from culture broth 14alpha-hydroxy-4-pregnene-3,11,20-trione, and the hitherto unreported compounds, 7alpha,14alpha-dihydroxy-4-pregnene-3,11,20-trione and 7alpha-hydroxy-pregna-4,8(14)-diene-3,11,20-trione.  相似文献   
90.
To determine useful metrics for assessing stream water quality in the Southeastern Coastal Plain, we examined differences among two buffered and three unbuffered streams in an agricultural landscape in southwestern Georgia. Potential indicators included amphibian diversity and abundance, aquatic macroinvertebrate populations, riparian vegetative structure, water quality, and stream physical parameters. Variability among sites and treatments (buffered vs. unbuffered) existed, with sites in the same treatment as most similar, and disturbances from a nearby eroding gully strongly affecting one unbuffered site. Of the invertebrate metrics examined, percentages of clingers, Ephemeroptera-Plecoptera-Trichoptera (EPT), Elmidae (Coleoptera), Crustacea (Decapoda and Amphipoda), and dipterans were found to be possible indicators of stream health for perennial streams within this region. Overall, buffered sites showed higher percentages of sensitive invertebrate groups and showed lower and more stable concentrations of nitrate N, suspended solids, and fecal coliforms (FCs). Percent canopy cover was similar among sites; however, riparian vegetative coverage and percent leaf litter were greatest at buffered sites. No differences in amphibian abundance, presence, and absence within the riparian area were apparent between sites; however, instream larval salamanders were more abundant at buffered streams. In this study, stream buffers appeared to decrease nutrient and sediment loads to adjacent streams, enhancing overall water quality. Selected benthic macroinvertebrate metrics and amphibian abundance also appeared sensitive to agricultural influences. Amphibians show potential as indicator candidates, however further information is needed on their responses and tolerances to disturbances from the microhabitat to landscape levels.  相似文献   
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