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Nitrogen (N) losses from agriculture are negatively impacting groundwater, air, and surface water quality. National, state, and local policies and procedures that can mitigate these problems are needed. Market-based approaches where waste treatment plants (point sources) can purchase nutrient credits from upstream agricultural operations (non-point sources) to meet their National Pollutant Discharge Elimination System permit requirements within the Clean Water Act are being explored. This paper reviews these market-based approaches for enhancing air and water quality at a lower cost than simple command-and-control regulation, and describes new tools that are being developed, such as Nitrogen Trading Tool (NTT), that can be used to assess nitrogen losses to the environment under different management scenarios. The USDA-NRCS, EPA and several other state and local agencies are interested in these new tools. The NTT, though primarily designed for water quality markets, also estimates savings in nitrous oxide (N2O) emissions that can be traded in carbon markets. For example, an analysis using NTT shows that for 100 ha of crop land, a C sequestration equivalent of approximately 25–38 Mg C y?1 for a farm in Ohio, and 13–21 Mg C y?1 for a farm in Virginia could be achieved with better nitrogen management practices. These numbers across a watershed could be much larger with improved N and conservation management practices that contribute to better water quality and lower global warming potential. There is a need to further develop, calibrate, and validate these tools to facilitate nitrogen and carbon trading future markets around the globe to increase environmental conservation across agro-ecosystems worldwide.  相似文献   
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Environmental Science and Pollution Research - Mining and extraction of stones and minerals play a significant role in many countries economic growth in the world. The production of dolomite...  相似文献   
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One approach for reducing the level of environmental contamination threats around the world is to use renewable energy-harvesting equipment. Wind is a potential environmental resource that has become a desirable aspect of urban use due to advances in wind turbine design technology. Other variants have been developed based on the classic vertical-axis Savonius rotor model, which, according to experimental test findings and computational calculations, show higher operational characteristics performance. Generated power and shaft torque operational results are obtained by providing specific rotor blade shapes in these models, one of the most common designs, among small-scale rotor which uses a drag-based vertical axis whereas Savonius turbines having large-scale rotors not developed yet. This kind of rotor has the advantages of being simple to design, affordable, performing well at low speeds, and turns to flow direction independently. However, it was discovered that the Savonius rotor suffers through high quantity of negative torques created by the returning blade after a number of examinations into its performance. Many studies on various rotor types have been conducted to resolve the Savonius turbine’s performance constraints. The research showed and analyzed the difficulties and modification in design parameters of rotor, as well as their major impact on rotor performance.

  相似文献   
55.
The distributed lag effects of ambient particulate air pollution exposure on respiratory hospital admissions in Kathmandu Valley are modelled using daily time series data. The extended exposure to PM10 is accounted for by assigning weights to daily average PM10 which decline geometrically as the lag period increases in days. Results show that the percent increase in chronic obstructive pulmonary disease (COPD) hospital admissions and respiratory admissions including COPD, asthma, pneumonia, and bronchitis per 10 μg/m3 rise in PM10 are found to be 4.85% for 30 days lag effect, about 15.9% higher than that observed for same-day lag effect and 3.52% for 40 days lag effect, about 28.9% higher than the observed value for same-day lag effect, respectively.  相似文献   
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Soil samples were collected from four aquaculture ponds (yellow perch culture), a control pond (without aquaculture activities, fallow pond), crop land (under corn), and forest land to estimate the carbon (C) sequestration potential in the Piketon county, Ohio, USA. The averaged total of C was 6.5?±?2, 8.8?±?2, 8.53?±?0.2 and 10.49?±?1.1 Mg/ha (Mg=106g) in <?0.25 mm fraction; 15.2?±?2, 16.0?±?3, 11.49?±?0.8 and 17.23?±?3.4 Mg/ha in micro aggregates (0.25–2.5 mm); and 22.1?±?3, 26.4?±?3, 12.16?±?1.6 and 18.51?±?4.3 Mg/ha in macro aggregates (?>?2.5mm), for aquaculture ponds, control ponds, cropland and forest land, respectively. The soil/sediment C pool followed the order of forest?>?crop land soils?>?aquaculture pond soils.  相似文献   
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A study of villus samples from eight random sites on five electively aborted chorion sacs was performed to determine any significant differences in yield, quality and composition of DNA, iduronate sulphate sulphatase activity and karyoptype status. The villi were also examined for their histological characteristics (e.g. stem, intermediate or terminal villi) and for HCG and BGP immuno-reactivities. The overall findings indicated no significant site to site variations in any of the parameters studied. It is therefore proposed that any villus should be equally suitable for prenatal diagnosis.  相似文献   
59.
Soil carbon dynamics in cropland and rangeland   总被引:36,自引:0,他引:36  
Most soils in the Midwestern USA have lost 30 to 50% of their original pool, or 25 to 40 Mg C/ha, upon conversion from natural to agricultural ecosystems. About 60 to 70% of the C thus depleted can be resequestered through adoption of recommended soil and crop management practices. These practices include conversion from plow till to no till, frequent use of winter cover crops in the rotation cycle, elimination of summer fallow, integrated nutrient management along with liberal use of biosolids and biological nitrogen fixation, precision farming to minimize losses and enhance fertilizer use efficiency, and use of improved varieties with ability to produce large root biomass with high content of lignin and suberin. The gross rate of soil organic carbon (SOC) sequestration ranges from 500 to 800 kg/ha/year in cold and humid regions and 100 to 300 kg/ha/year in dry and warm regions. The rate of SOC sequestration can be measured with procedures that are cost effective and credible at soil pedon level, landscape level, regional or national scale. In addition to SOC, there is also a large potential to sequester soil inorganic carbon (SIC) in arid and semi-arid regions. Soil C sequestration has numerous ancillary benefits. It is truly a win-win situation: extremely cost-effective, and a bridge to the future until alternative energy options take effect.  相似文献   
60.
The effects of three insecticides, dieldrin, dimethoate and permethrin, on the growth of a holotrichous ciliate, Tetrahymena pyriformis, were studied for 5 days. The ciliate was very sensitive to dieldrin and dimethoate. Both these insecticides produced approximately 81% and 84% inhibition of growth within two days. Dieldrin caused rounding of cells, while dimethoate induced cell lysis. Dimethoate also triggered a general mucocyst discharge. Of the three insecticides, permethrin was the least toxic and induced no morphological alterations.  相似文献   
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