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131.
ABSTRACT: Wetlands exist in a transition zone between aquatic and terrestrial environments which can be altered by subtle changes in hydrology. Twentieth century climate records show that the United States is generally experiencing a trend towards a wetter, warmer climate; some climate models suggest that this trend will continue and possibly intensify over the next 100 years. Wetlands that are most likely to be affected by these and other potential changes (e.g., sea‐level rise) associated with atmospheric carbon enrichment include permafrost wetlands, coastal and estuanne wetlands, peat lands, alpine wetlands, and prairie pothole wetlands. Potential impacts range from changes in community structure to changes in ecological function, and from extirpation to enhancement. Wetlands (particularly boreal peat‐lands) play an important role in the global carbon cycle, generally sequestering carbon in the form of biomass, methane, dissolved organic material and organic sediment. Wetlands that are drained or partially dried can become a net source of methane and carbon dioxide to the atmosphere, serving as a positive biotic feedback to global warming. Policy options for minimizing the adverse impacts of climate change on wetland ecosystems include the reduction of current anthropogenic stresses, allowing for inland migration of coastal wetlands as sea‐level rises, active management to preserve wetland hydrology, and a wide range of other management and restoration options. 相似文献
132.
Carroll KC Oostrom M Truex MJ Rohay VJ Brusseau ML 《Journal of contaminant hydrology》2012,128(1-4):71-82
Soil vapor extraction (SVE) is typically effective for removal of volatile contaminants from higher-permeability portions of the vadose zone. However, contamination in lower-permeability zones can persist due to mass transfer processes that limit the removal effectiveness. After SVE has been operated for a period of time and the remaining contamination is primarily located in lower-permeability zones, the remedy performance needs to be evaluated to determine whether the SVE system should be optimized, terminated, or transitioned to another technology to replace or augment SVE. Numerical modeling of vapor-phase contaminant transport was used to investigate the correlation between measured vapor-phase mass discharge, MF(r), from a persistent, vadose-zone contaminant source and the resulting groundwater contaminant concentrations. This relationship was shown to be linear, and was used to directly assess SVE remediation progress over time and to determine the level of remediation in the vadose zone necessary to protect groundwater. Although site properties and source characteristics must be specified to establish a unique relation between MF(r) and the groundwater contaminant concentration, this correlation provides insight into SVE performance and support for decisions to optimize or terminate the SVE operation or to transition to another type of treatment. 相似文献
133.
García R Rubio V Vegas I Frías M 《Environmental science and pollution research international》2009,16(3):274-277
Background, aim and scope One of the problems to affect Portland cement matrices is low resistance to aggressive agents, due principally to the presence
of a high content of portlandite in the hydrated cements. Pozzolanic materials have played an important role in the improving
the durability of cement-based materials for decades. This work studies the behaviour of cement mortar matrices blended with
10% calcined paper sludge (source for metakaolinite) and exposed to different environmental conditions (saline and non-saline
environments) after 6 and 12 months of exposure.
Materials and methods Two cements were studied: an ordinary Portland cement (CEM 1, 42.5R), acting as reference cement, and a blended cement formulated
by mixing 90% (by mass) of CEM 1, 42.5R with 10% (by mass) of paper sludge calcined at 700°C for 2 h. The specimens were exposed
1 year to saline and non-saline environments. All the mineralogy samples were studied through X-ray diffraction and scanning
electron microscopy (SEM) equipped with an energy dispersive X-ray analyser. The in-depth study on ionic mobility was performed
on samples subjected to natural exposure (coast and tableland) for 6 and 12 months.
Results Portland cement was composed of quartz, calcite, calcium hydroxide and tobermorite gels. The pozzolanic cement (10% calcined
paper sludge) is of the same composition but a high calcite concentration and barium carbonate. SEM analysis from coastline
show deposits of variable composition. The deposits are identified on the surface of different mineral components. The minerals
from tableland are much fractured, i.e. calcite and feldspars. Inside the fractures, the deposits and the ions are located
and trapped superficially.
Discussion SEM analysis of control cement Portland and 10% calcined paper sludge shows deposits on quartz and calcite with a very high
concentration of Pb, Zn, Cl and barium sulphate. A very porous aspect is due to the presence of the different aggregate types.
This porous configuration permits retention of the ion environment. The pozzolanic cement in environments subject to the saline
mist favours the retention and transport of ions observed. Something similar also happens with the increase in exposure to
outdoor weather. Non-saline samples show temperature changes (ice or thaw cycles). Barium retention is kept on the surface
in fracture lines by the gelification processes. In general, it may be inferred that an increase in exposure time increases
the diffusion of ions towards test piece interiors. The chemical composition profiles show that the ions present different
penetration speeds.
Conclusions The results indicate the better vulnerability of pozzolanic cements from calcined paper sludge in saline and non-saline environments.
The cements with a 10% addition of calcined paper sludge favour retention and transport of ion has been observed.
Recommendations and perspectives Today, projects are centred on a new recycling line for industrial waste of this kind, with special attention on its incorporation
in cement manufacture as a pozzolanic material, setting the most appropriate activation conditions of the mineralogical compound
in this waste (kaolinite and metakaolinite) and taking them as a starting point for this project. The use of pozzolanic cement
with 10% addition of calcined paper sludge is a system which favours ionic retention. 相似文献
134.
The condition of coral reefs in South Florida (2000) using coral disease and bleaching as indicators 总被引:2,自引:0,他引:2
Santavy DL Summers JK Engle VD Harwell LC 《Environmental monitoring and assessment》2005,100(1-3):129-152
The destruction of coral reef habitats has occurred at unprecedented levels during the last three decades. Coral disease and bleaching in the Caribbean and South Florida have caused extensive coral mortality with limited recovery, often coral reefs are being replaced with turf algae. Acroporids were once dominant corals and have diminished to the state where they are being considered as endangered species. Our survey assessed the condition of reef corals throughout South Florida. A probability-based design produced unbiased estimates of the spatial extent of ecological condition, measured as the absence or presence and frequency or prevalence of coral diseases and bleaching intensity over large geographic regions. This approach allowed us to calculate a quantifiable level of uncertainty. Coral condition was estimated for 4100 hectares (ha) (or 41.0 km2) of coral reefs in South Florida, including reefs in the Florida Keys National Marine Sanctuary (FKNMS), New Grounds, Dry Tortugas National Park (DTNP), and Biscayne National Park (BNP). The absence or presence of coral disease, causal coral bleaching, partial bleaching and coral paling were not good indicators of overall coral condition. It was more useful to report the prevalence of anomalies that indicated a compromised condition at both the population and community levels. For example, 79% of the area in South Florida had less than 6% of the coral colonies diseased, whereas only 2.2% (97.15 ha) of the sampled area had a maximum prevalence of 13% diseased coral colonies at any single location. The usefulness of causal bleaching might be more important when considering the prevalence of each of the three different states at a single location. For example, paling was observed over the entire area, whereas bleaching and partial bleaching occurred at 19 and 41% of the area, respectively. An index for coral reef condition might integrate the prevalence and species affected by each bleaching state at individual locations. By establishing these baselines, future surveys can examine changes and trends in the spatial distribution of coral conditions in South Florida and able to score the reefs as to their health status. 相似文献
135.
Janet A. Nestlerode Virginia D. Hansen Aarin Teague Matthew C. Harwell 《Environmental monitoring and assessment》2014,186(6):3477-3493
A multi-level coastal wetland assessment strategy was applied to wetlands in the northern Gulf of Mexico (GOM) to evaluate the feasibility of this approach for a broad national scale wetland condition assessment (US Environmental Protection Agency’s National Wetlands Condition Assessment). Landscape-scale assessment indicators (tier 1) were developed and applied at the sub-watershed (12-digit hydrologic unit code (HUC)) level within the GOM coastal wetland sample frame with scores calculated using land-use maps and geographic information system. Rapid assessment protocols (tier 2), using a combination of data analysis and field work, evaluated metrics associated with landscape context, hydrology, physical structure, and biological structure. Intensive site monitoring (tier 3) included measures of soil chemistry and composition, water column and pore-water chemistry, and dominant macrophyte community composition and tissue chemistry. Relationships within and among assessment levels were evaluated using multivariate analyses with few significant correlations found. More detailed measures of hydrology, soils, and macrophyte species composition from sites across a known condition gradient, in conjunction with validation of standardized rapid assessment method, may be necessary to fully characterize coastal wetlands across the region. 相似文献
136.
137.
Christopher M. Zarzar Hossein Hosseiny Ridwan Siddique Michael Gomez Virginia Smith Alfonso Mejia Jamie Dyer 《Journal of the American Water Resources Association》2018,54(4):807-819
While deterministic forecasts provide a single realization of potential inundation, the inherent uncertainty associated with forecasts also needs to be conveyed for improved decision support. The objective of this study was to develop an ensemble framework for the quantification and visualization of uncertainty associated with flood inundation forecast maps. An 11‐member ensemble streamflow forecast at lead times from 0 to 48 hr was used to force two hydraulic models to produce a multimodel ensemble. The hydraulic models used are (1) the International River Interface Cooperative along with Flow and Sediment Transport with Morphological Evolution of Channels solver and (2) the two‐dimensional Hydrologic Engineering Center‐River Analysis System. Uncertainty was quantified and augmented onto flood inundation maps by calculating statistical spread among the ensemble members. For visualization, a series of probability flood maps conveying the uncertainty in forecasted water extent, water depth, and flow velocity was disseminated through a web‐based decision support tool. The results from this study offer a framework for quantifying and visualizing model uncertainty in forecasted flood inundation maps. 相似文献
138.
Current methods for assessing the environmental impact of point source discharges in the United States are reviewed. The emphasis of many assessments of damage from pollution is shifting from chemical or technological standards to biological standards, i.e., the protection of biological integrity in the receiving system. The importance of integrating information from chemical measurements, toxicity tests, and field surveys in impact assessment is re-emphasized. Ways in which environmental professionals can improve methods for assessing damage from pollution and its control are discussed. 相似文献
139.
“我想把荒山变成玫瑰田”,严景玉(音)先生充满信心地说到。作为江油市巽牌有机农业有限责任公司的拥有者,从1969年第一次收获大马士革玫瑰开始,严先生就一直梦想着将有机耕作变为他的家乡——四川省的通行耕作方式。从那时起,严先生不仅将退化土地修复为可耕作农田,他还将有机耕作的理念引入中国偏远山区,成为一个创业者。当巽牌开始与国际买家合作时,公司的质量标准和分级方法在整个地区的农业领域中传播。 相似文献
140.
Charles Hostovsky Virginia MacLaren Geoffrey McGrath 《Journal of Environmental Planning and Management》2010,53(3):405-425
This paper explores the extent to which Western approaches to public involvement in environmental impact assessment (EIA) have been transferred to Vietnam, constraints on their use, and their appropriateness for the Vietnamese context. The research is based on an analysis of the public involvement content found in 26 EIA reports from development banks and interviews with 26 key informants. The study found that public involvement in Vietnam is generally technocratic, expert-driven and non-transparent, similar to the early days of EIA in the West and emerging economies. Public involvement usually occurs through authorised state channels such as commune leaders, mass organisations and professional organisations. The lack of a participatory culture for EIA, the nascent nature of grassroots democracy in the country, and Vietnamese cultural norms regarding respect for authority provide a challenging context for involving the public in EIA. The paper concludes by offering a number of suggestions for culturally appropriate public involvement at a time when Vietnam has just introduced mandatory public consultation for EIAs. 相似文献