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151.
Anders Stigebrandt Lars Rahm Lena Viktorsson Malin Ödalen Per O. J. Hall Bengt Liljebladh 《Ambio》2014,43(5):634-643
The external phosphorus (P) loading has been halved, but the P content in the water column and the area of anoxic bottoms in Baltic proper has increased during the last 30 years. This can be explained by a temporary internal source of dissolved inorganic phosphorus (DIP) that is turned on when the water above the bottom sediment becomes anoxic. A load-response model, explaining the evolution from 1980 to 2005, suggests that the average specific DIP flux from anoxic bottoms in the Baltic proper is about 2.3 g P m−2 year−1. This is commensurable with fluxes estimated in situ from anoxic bottoms in the open Baltic proper and from hydrographic data in the deep part of Bornholm Basin. Oxygenation of anoxic bottoms, natural or manmade, may quickly turn off the internal P source from anoxic bottoms. This new P-paradigm should have far-reaching implications for abatement of eutrophication in the Baltic proper.
Electronic supplementary material
The online version of this article (doi:10.1007/s13280-013-0441-3) contains supplementary material, which is available to authorized users. 相似文献152.
Levels,profile and distribution of Dechloran Plus (DP) and Polybrominated Diphenyl Ethers (PBDEs) in the environment of Pakistan 总被引:1,自引:0,他引:1
Jabir Hussain Syed Riffat Naseem Malik Jun Li Yan Wang Yue Xu Gan Zhang Kevin C. Jones 《Chemosphere》2013
No scientific data is available on emerging contaminants including Polybrominated Diphenyl Ethers (PBDEs) and Dechloran Plus (DP) levels in the environment in Pakistan. Levels of PBDEs and DP were determined in the soil, sediment and atmospheric samples along the stretch of River Ravi in Punjab Province. Average concentrations of ΣPBDEs in atmosphere, soils and sediments were 36 pg m−3, 40 ng g−1 and 640 ng g−1. BDE-209 was the most abundant PBDE congener, showing that deca-BDE accounts for most of the total PBDE emitted in the environment of Pakistan. Total DP levels were calculated as 88 pg m−3, 0.8 ng g−1 and 1.9 ng g−1 in air, soil and sediment samples, respectively. The lower average fractions of anti-DP showed significant differences to those of the technical mixtures, indicating the lack of DP production source in Pakistan. 相似文献
153.
Monitoring morphological and vegetation changes and flow events in dryland river channels 总被引:1,自引:0,他引:1
Hooke JM 《Environmental monitoring and assessment》2007,127(1-3):445-457
Monitoring of impacts of floods in river valleys of dryland regions has become important with the onset and threats of desertification
and is likely to become even more vital with predictions of increased effects of climate and land use change. It is also needed
in order to conform to requirements of the EU Water Framework Directive. Monitoring in such regions sets particular challenges.
This paper explains a system of low-cost monitoring of changes in morphology, vegetation and sediment cover in channels and
valley floors of ephemerally flowing streams. It has been applied in SE Spain for 10 years and has proved very effective.
In particular, the use of simple crest-stage recorders for measuring flow height and the use of real-time differential GPS
for rapid and accurate survey and for relocating points have proved very valuable. Part of the monitoring is focused on the
interaction of plants and channel processes. Small changes in and around vegetation associated with flow events have been
detected by a combination of quadrat surveys and cross-profiling of the channel. A range of flow events has been measured
over the period of monitoring, demonstrating their differing effects and the varying sensitivity and responsiveness of different
sites. The sporadic occurrence of flood events in such an environment means that a strategy of monitoring several sites and
of continuation over many years has great benefits. 相似文献
154.
Distribution and contamination assessment of heavy metals in sediment of the Second Songhua River, China 总被引:2,自引:0,他引:2
The Second Songhua River was subjected to a large amount of raw or primary effluent from chemical industries in Jilin city
in 1960s to 1970s, resulting in serious mercury pollution. However, an understanding of other trace metal pollution has remained
unclear. The objective of this study was to investigate trace metal contamination in the sediment of the river. Bottom sediment
samples were taken in the river between Jilin city and Haerbin city in 2005. An uncontaminated sediment profile was taken
in the Nen River at the same time. Total concentrations of Al, Fe, Mg, Ca, K, Na, Ti, Mn, V, Sc, Co, Cu, Cr, Ni, Pb and Zn
in the sediment samples were measured by ICP-MS or ICP-OES, following digestion with various acids. Concentrations of Co,
Cu, Cr, Ni, Pb and Zn in the surface sediments were 5.1–14.7, 18.5–78.9, 2.4–75.4, 7.2–29.0, 13.5–124.4, and 21.8–403.1 mg/kg,
respectively, generally decreasing along the course of the river from Jilin city to Haerbin city. Background concentrations
of trace metals were reconstructed by geochemical normalization to a conservative element scandium. Results showed that concentrations
of Co, Cr, and Ni in the sediment were generally only slightly higher than or equal to their background values, while concentrations
of Cu, Pb, and Zn in the some sediment samples were significantly higher than their background values. In detail, the sediment
at Jilin city was moderately contaminated by Cu, and the sediment of the Second Songhua River was moderately contaminated
by Pb and Zn. The top layer (0–10 cm depth) and bottom layers (30–46 cm depth) of one sediment profile at Wukeshu town were
generally moderately polluted by Pb and Zn. Synthetically, the surface sediment in the studied river section was classified
as natural sediment without ecological risk by the sediment pollution index (SPI) of Cu, Cr, Ni, Pb and Zn. Only the 30–45 cm
depth of the sediment profile at Wukeshu town was classified as low polluted sediment by the SPI of these metals, recording
a historical contamination of the river in the 1960s to 1970s. This buried contamination of trace metals might pose a potential
risk to water column under disturbance of sediment.
Foundation item: The National Basic Research Priorities Program of China (2004CB418502) 相似文献
155.
The Bothnian Bay, which is the northernmost part of the Gulf of Bothnia in Northern Finland, is affected by effluents discharged from point sources such as the pulp and paper mills of Stora Enso Oyj Veitsiluoto Mill and Oy Metsä-Botnia Ab Kemi Mill at Kemi, and the Kemi municipal sewage plant, as well as the River Kemijoki. In this paper we discuss, how modernisation of the wastewater treatment plant at the mills, and process investments in the Best Available Techniques (BAT) for effluent treatment, have decreased the effluent discharges of biological oxygen demand (BOD), chemical oxygen demand (COD), total phosphorus (Tot-P), total nitrogen (TOT-N), total suspended solids (TSS) and adsorbable organically bound halogens (AOX) from the mills since 1988. One specific aim of the study was to determine the EOX (Extractable Organically Bound Halogens) concentrations in bottom sediment of the Bothnian Bay in order to assess whether the EOX concentrations reflect the reduction in discharges of chlorinated compounds. According to the monitoring program carried out every third year between 1997–2006, the decreasing trend in EOX concentrations in the top 2 cm of the bottom sediment reflect the decrease in organochlorine discharges (AOX) from the mills. In 1997 the EOX concentrations in bottom sediment varied between 3–70 μg of Cl g?1 (dry weight), and in 2006 between 3.3–32 μg of Cl g?1 (dry weight). 相似文献
156.
157.
应用模糊综合-加权模型,以及温州市3个典型湿地沉积物中7种重金属含量数据,对温瑞塘河重金属污染进行评价。模糊综合评价结果表明,温州市居民区河流三垟湿地沉积物属于Ⅴ级重金属污染水平,主要污染元素为Zn和Cd;山前上游河段卧龙河沉积物为Ⅲ级污染,主要污染物是Cd。工业区河流牛桥底河沉积物虽然也是Ⅴ级,但是Cu、Cr、Ni、Zn和Cd 5种重金属污染分值为1.0,小于前2个典型河段的1.2和3.3。内梅罗指数法和潜在生态危害系数法评价结果显示,沉积物的重金属污染程度为牛桥底河三垟湿地卧龙河,这与模糊综合评价结果相符。 相似文献
158.
Natural gamma radiation of beach sand deposits was measured along the south coast of Rio de Janeiro State, Brazil, with the aim of studying the provenance and transport processes of sediments in this area. Concentrations of thorium, uranium and potassium were evaluated using γ-ray spectrometry and a behavioral study of eTh/eU and eTh/K cross plots was performed, reflecting the mineralogical properties of beach sands, as well as their history of transport and sorting processes. The results show that such technique can be efficiently used to map heavy mineral distributions and to distinguish the different origins of coastal sediments disclosing the influence of nearby rivers. 相似文献
159.
Samples from a marine sediment core from the Irish Sea (54.416 N, 3.563 W) were analyzed for the isotopic composition of uranium, plutonium and americium by a combination of radiometric methods and AMS. The radiochemical procedure consisted of a Pu separation step by anion exchange, subsequent U separation by extraction chromatography using UTEVA® and finally Am separation with TRU® Resin.Additionally to radiometric determination of these isotopes by alpha spectrometry, the separated samples were also used for the determination of 236U/238U and plutonium isotope ratios by Accelerator Mass Spectrometry (AMS) at the VERA facility. 相似文献
160.
Yunuén CL Vinicio MZ Miguel Angel HD Wee Kwong LL Sanchez-Cabeza JA 《Environmental pollution (Barking, Essex : 1987)》2011,159(2):487-494
This paper describes the first report of dioxins and furans (PCDDs/Fs) in sediment cores from Mexico. Sedimentation rates and vertical fluxes were estimated using 210Pb dating. Two cores correspond to marine sediments and one to an endorheic lake. Concentrations of PCDDs/Fs found in the three sites are typical of non-impacted areas with low concentrations when compared to reference values. However the PCDDs/Fs sediment profiles show an increasing concentration trend in the upper core sections. This behavior is different from that found at many sites around the globe where diminishing concentrations have been reported. A strong predominance of OCDD was observed, and a comparison to typical composition profiles of industrial and other sources did not result in clear origin assignments for these measured compounds. We suggest that local sources may be responsible for the increase in concentration and, because these undetermined sources have not been curtailed, their importance is still growing. 相似文献