全文获取类型
收费全文 | 556篇 |
免费 | 6篇 |
国内免费 | 86篇 |
专业分类
安全科学 | 20篇 |
废物处理 | 9篇 |
环保管理 | 58篇 |
综合类 | 257篇 |
基础理论 | 70篇 |
污染及防治 | 163篇 |
评价与监测 | 63篇 |
社会与环境 | 8篇 |
出版年
2023年 | 13篇 |
2022年 | 17篇 |
2021年 | 12篇 |
2020年 | 18篇 |
2019年 | 14篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 20篇 |
2015年 | 38篇 |
2014年 | 30篇 |
2013年 | 29篇 |
2012年 | 30篇 |
2011年 | 48篇 |
2010年 | 31篇 |
2009年 | 45篇 |
2008年 | 54篇 |
2007年 | 47篇 |
2006年 | 33篇 |
2005年 | 18篇 |
2004年 | 16篇 |
2003年 | 16篇 |
2002年 | 15篇 |
2001年 | 12篇 |
2000年 | 20篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有648条查询结果,搜索用时 15 毫秒
641.
Pesch R Schröder W Schmidt G Genssler L 《Environmental pollution (Barking, Essex : 1987)》2008,155(3):528-536
In order to assess whether nitrogen (N) loads in mosses reflect different land uses, 143 sites in North Rhine-Westphalia, the Weser-Ems Region and the Euro Region Nissa were sampled between 2000 and 2005. The data were analysed statistically with available surface information on land use and forest conditions. N bioaccumulation in mosses in the Weser-Ems Region with high densities of agricultural land use and livestock exceeded the concentrations in the more industrialised Euro Region Nissa. In all three study areas agricultural and livestock spatial densities were found to be positively correlated with N bioaccumulation in mosses. In North Rhine-Westphalia, the N concentrations in mosses was also moderately correlated with N concentrations in leaves and needles of forest trees. The moss method proved useful to assess the spatial patterns of N bioaccumulation due to land use. 相似文献
642.
Urine source separation (NoMix technology) is a promising innovation in wastewater management. To improve and further develop NoMix technology, it has been implemented in four Swiss households and at our research institute (Eawag). We conducted measurements during one year on frequency of toilet usage (in households 5.2/person/day for weekdays, and 6.3/person/day for weekends), flushing behavior (30–85% small flushes), and recovered urine. We calculate the amount of urine effectively recovered per voiding in NoMix toilets (138 ml/flush in households; 309 ml/flush in women's toilets at Eawag), and waterfree urinals (225 ml/usage). We estimate urine recovery in the households to be maximally 70–75% of the expected quantity, leaving room for technical and behavioral improvements. Based on sampling of N and P concentrations, we suspect nitrogen losses in the extended urine piping system. For households and workplaces, the daily and weekly flushing pattern is recorded. Our results are in accordance with literature data from a shorter period but with more people. These results represent a good dimensioning basis for future urine source separation applications. An example of extrapolation to an entire watershed is presented. The flushing pattern corresponds well with the typical nitrogen loading of a treatment plant. 相似文献
643.
644.
Maintenance of soil organic carbon (SOC) is important for sustainable use of soil resources due to the multiple effects of
SOC on soil nutrient status and soil structural stability. The objective of this study was to identify the changes in soil
aggregate distribution and stability, SOC, and nitrogen (N) concentrations after cropland was converted to perennial alfalfa
(Medicago sativa L. Algonguin) grassland for 6 years in the marginal oasis of the middle of Hexi Corridor region, northwest China. Significant
changes in the size distribution of dry-sieving aggregates and water-stable aggregates, SOC, and N concentrations occurred
after the conversion from crop to alfalfa. SOC and N stocks increased by 20.2% and 18.5%, respectively, and the estimated
C and N sequestration rates were 0.4 Mg C ha−1 year−1 and 0.04 Mg N ha−1 year−1 following the conversion. The large aggregate (>5 mm) was the most abundant dry aggregate size fraction in both crop and
alfalfa soils, and significant difference in the distribution of dry aggregates between the two land use types occurred only
in the >5 mm aggregate fraction. The percentage of water-stable macroaggregates (>2, 2–0.25 mm) and aggregate stability (mean
weight diameter of water-stable aggregates, WMWD) were significantly higher in alfalfa soils than in crop soils. There was
a significant linear relationship between total SOC concentration and aggregate parameters (mean weight diameter) for alfalfa
soils, indicating that aggregate stability was closely associated with increased SOC concentration following the conversion
of crops to alfalfa. The SOC and N concentrations and the C/N ratio were greatest in the >2 mm water-stable aggregates and
the smallest in the 0.25–0.05 mm aggregates in crop and alfalfa soils. For the same aggregate, SOC and N concentrations in
aggregate fractions increased with increasing total SOC and N concentrations. The result showed that the conversion of annual
crops to alfalfa in the marginal land with coarse-texture soils can significantly increase SOC and N stocks, and improve soil
structure. 相似文献
645.
Wetland ecosystems are profoundly affected by altered nutrient and sediment loads received from anthropogenic activity in
their surrounding watersheds. Our objective was to compare a gradient of agricultural and urban land cover history during
the period from 1949 to 1997, with plant and soil nutrient concentrations in, and sediment deposition to, riparian wetlands
in a rapidly urbanizing landscape. We observed that recent agricultural land cover was associated with increases in Nitrogen
(N) and Phosphorus (P) concentrations in a native wetland plant species. Conversely, recent urban land cover appeared to alter
receiving wetland environmental conditions by increasing the relative availability of P versus N, as reflected in an invasive,
but not a native, plant species. In addition, increases in surface soil Fe content suggests recent inputs of terrestrial sediments
associated specifically with increasing urban land cover. The observed correlation between urban land cover and riparian wetland
plant tissue and surface soil nutrient concentrations and sediment deposition, suggest that urbanization specifically enhances
the suitability of riparian wetland habitats for the invasive species Japanese stiltgrass [Microstegium vimenium (Trinius) A. Camus]. 相似文献
646.
Ebrayi KN Pathak H Kalra N Bhatia A Jain N 《Environmental monitoring and assessment》2007,131(1-3):451-465
Nitrogen is the most widely used fertilizer nutrient, and it is a universally deficient nutrient too, which often severely
restricts the growth and yield of crops. To improve N fertilizer management, soil–plant system models can be applied to simulate
adequate N supply for both, optimal crop growth and minimal N losses. The likely impact of climate change on the cereal production
is of paramount importance in the planning strategies to meet the future growing needs on sustainable grounds. In this scenario
models are the effective tools to foresee the probable impacts and for choosing appropriate land use options. The study reported
in this thesis, employs field experiments and use of simulation tools to understand the dynamics of soil N balance and relate
growth and yield of rice under varying nitrogen inputs. The InfoCrop model was used in this study, which was calibrated with
the historic data sets, and subsequently validated with the field experiment conducted at IARI Farm, New Delhi. Simulated
results matched well with the observed values in terms of growth and yield of rice and seasonal nitrogen uptake. The components
of soil nitrogen balance differed among varying nitrogen level treatments, which was also captured by use of InfoCrop. The
model was then taken to climate change impact analysis. The results clearly revealed that when temperature increased, the
soil N losses, like denitrification, volatilization, N2O emission increased, whereas grain and biomass yields decreased. The
further scope of the study is to validate the study in contrasting agroenvironments. 相似文献
647.
Xiang Zhang Yue Xuan Bin Wang Chuan Gao Shengli Niu Gaiju Zhao Dong Wang Junhua Li Chunmei Lu John C. Crittenden 《Frontiers of Environmental Science & Engineering》2022,16(7):88
648.
Research on biofuel production pathways from algae continues because among other potential advantages they avoid key consequential effects of terrestrial oil crops, such as competition for cropland. However, the economics, energetic balance, and climate change emissions from algal biofuels pathways do not always show great potential, due in part to high fertilizer demand. Nutrient recycling from algal biomass residue is likely to be essential for reducing the environmental impacts and cost associated with algae-derived fuels. After a review of available technologies, anaerobic digestion (AD) and hydrothermal liquefaction (HTL) were selected and compared on their nutrient recycling and energy recovery potential for lipid-extracted algal biomass using the microalgae strain Scenedesmus dimorphus. For 1 kg (dry weight) of algae cultivated in an open raceway pond, 40.7 g N and 3.8 g P can be recycled through AD, while 26.0 g N and 6.8 g P can be recycled through HTL. In terms of energy production, 2.49 MJ heat and 2.61 MJ electricity are generated from AD biogas combustion to meet production system demands, while 3.30 MJ heat and 0.95 MJ electricity from HTL products are generated and used within the production system.Assuming recycled nutrient products from AD or HTL technologies displace demand for synthetic fertilizers, and energy products displace natural gas and electricity, the life cycle greenhouse gas reduction achieved by adding AD to the simulated algal oil production system is between 622 and 808 g carbon dioxide equivalent (CO2e)/kg biomass depending on substitution assumptions, while the life cycle GHG reduction achieved by HTL is between 513 and 535 g CO2e/kg biomass depending on substitution assumptions. Based on the effectiveness of nutrient recycling and energy recovery, as well as technology maturity, AD appears to perform better than HTL as a nutrient and energy recycling technology in algae oil production systems. 相似文献