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801.
802.
Tlili A Marechal M Montuelle B Volat B Dorigo U Bérard A 《Environmental pollution (Barking, Essex : 1987)》2011,159(1):18-24
Understanding the ecological status of aquatic ecosystems and the impact of anthropogenic contamination requires correlating exposure to toxicants with impact on biological communities. Several tools exist for assessing the ecotoxicity of substances, but there is still a need for new tools that are ecologically relevant and easy to use. We have developed a protocol based on the substrate-induced respiration of a river biofilm community, using the MicroResp™ technique, in a pollution-induced community tolerance approach. The results show that MicroResp™ can be used in bioassays to assess the toxicity toward biofilm communities of a wide range of metals (Cu, Zn, Cd, Ag, Ni, Fe, Co, Al and As). Moreover, a community-level physiological profile based on the mineralization of different carbon substrates was established. Finally, the utility of MicroResp™ was confirmed in an in-situ study showing gradient of tolerance to copper correlated to a contamination gradient of this metal in a small river. 相似文献
803.
Gillis PL 《Environmental pollution (Barking, Essex : 1987)》2011,159(6):1702-1708
Chloride concentrations in surface waters have increased significantly, a rise attributed to road salt use. In Canada, this may be a concern for endangered freshwater mussels, many with ranges limited to southern Ontario, Canada’s most road-dense region. The acute toxicity of NaCl was determined for glochidia, the mussel’s larval stage. The 24 h EC50s of four (including two Canadian endangered) species ranged from 113-1430 mg Cl L−1 (reconstituted water, 100 mg CaCO3 L−1). To determine how mussels would respond to a chloride pulse, natural river water (hardness 278-322 mg CaCO3 L−1) was augmented with salt. Lampsilis fasciola glochidia were significantly less sensitive to salt in natural water (EC50s 1265-1559 mg Cl L−1) than in reconstituted water (EC50 285 mg L−1). Chloride data from mussel habitats revealed chloride reaches levels acutely toxic to glochidia (1300 mg L−1). The increased salinization of freshwater could negatively impact freshwater mussels, including numerous species at risk. 相似文献
804.
Little EE Calfee RD Fabacher DL Carey C Blazer VS Middleton EM 《Environmental science and pollution research international》2003,10(3):167-172
Background Exposure to harmful levels of ultraviolet-B radiation (UVB), a component of solar radiation, has been suggested as a potential
cause of amphibian declines.
Methods We measured solar radiation (UVB, ultraviolet-A, and visible) wavebands in breeding ponds of Bufo boreas (boreal toad, a montane species that has undergone severe population declines) and Bufo woodhousii (Woodhouse’s toad, a plains toad that has not experienced declines) and examined tolerances of these species to simulated
solar UVB exposures in the laboratory.
Results We found larvae of both species to be tolerant of simulated solar UVB in excess of solar UVB levels observed in their breeding
ponds. B. boreas tadpoles were more tolerant of simulated solar UVB exposure than B. woodhousii tadpoles, possibly because of greater amounts of photoprotective melanin in B. boreas skin.
Conclusions UVB levels observed in B. boreas habitats do not currently appear to constitute a threat to the survival of these animals; however, long-term (>1 month) exposure
to UVB levels comparable to levels associated with the water interface appears to reduce survival in B. woodhousii tadpoles. Therefore, future increases in surface and water column UVB radiation in bufonid habitats might pose significant
survival risks to B. boreas or B. woodhousii populations. 相似文献
805.
Metabolic responses of weeping willows to selenate and selenite 总被引:2,自引:0,他引:2
Goal, Scope and Background Selenium (Se) is one of the most widely distributed elements of the earth’s crust at low concentrations. The extensive use
of Se-containing chemicals due to anthropogenic activities has increased the ecological risk to environmental compartments.
Plants, under unfavorable environmental conditions, often increase the formation of reactive oxygen species (ROS), and consequently
plant antioxidant enzymatic systems have been proposed to be important in plant stress tolerance. The goal of this study was
to find out the metabolic responses of plants to Se, to provide quantitative information whether exogenous Se has a beneficial
role in plants, and to investigate the potential of vegetation management of Se for potential phytoremediation.
Material and Methods Pre-rooted plants of weeping willows (Salix babylonica L.) were grown hydroponically in growth chambers and treated with Na2SeO4 or Na2SeO3 at 24.0 ± 1°C for 168 h. Five different treatment concentrations were used, ranging from 0.44 to 8.72 mg Se/L for the treatments
exposed to SeO42− and from 0.50 to 10.0 mg Se/L for the treatments exposed to SeO32−, respectively. Transpiration rates, soluble protein contents and antioxidative enzyme activities of the plants were monitored
to evaluate toxicity from exogenous Se exposure. At the end of the study, total Se in the hydroponic solution was analyzed
by hydride generation-atomic fluorescence spectrometry (HG-AFS).
Results Both chemical forms of Se at low concentrations showed growth-promoting effects on plants. A significant decrease of transpiration
rates and of soluble protein contents of plants was observed at higher Se concentrations after 168 h of exposure. Measurable
change of superoxide dismutases (SOD) activity in leaves was only detected under high Se treatments. Catalase (CAT) activity
was significantly affected by the Se application. Slight change of peroxidase (POD) activity was measured in all treatments,
whereas significant inhibition of POD activity was detected for the plants exposed to SeO32− of 10.0 mg Se/L. Se-induced stress appeared in all treatments, thus resulting in measurable increase of glutathione peroxidase
(GSH-Px) activity of the plants. Although both chemical forms of Se were taken up by weeping willows efficiently, their uptake
rates were different.
Discussion Of all measured parameters, POD and CAT activities in leaves were noted the most sensitive indicator for the plants exposed
to SeO42− and SeO32−, respectively. Deleterious effects on plant physiological functions due to Se application were not observed over 168 h of
exposure. This is largely due to the fact that well-established antioxidant enzymatic systems in plants and higher activities
of GSH-Px largely reduced the negative effects on plants; SeO32− caused much more severe stress to plants than SeO42− at higher Se application rates. The uptake mechanisms between the two chemical species were quite different.
Conclusions Neither visible toxic symptoms nor metabolic lesions were observed at low concentrations of Se, probably due to the effective
established enzymatic systems in weeping willows. All selected parameters for toxicity determination were significantly correlated
to Se application, but metabolic responses of plants to SeO42− and SeO32− were quite different. GSH-Px in leaves was probably the principle enzyme responsible for stress reduction from Se exposure.
Due to their different chemical properties, weeping willows showed a faster uptake rate for SeO42− than for SeO32−.
Recommendations Exogenous Se has a beneficial role in plants and vegetation management of Se is a potential remediation strategy in cleaning
up Se-contaminated sites. Further investigation on the biochemical mechanism of Se metabolism will provide insight to the
specific interactions between Se and plants on the molecular level.
Perspectives Weeping willow has a sound potential for phytoremediation of Se-contaminated sediment and groundwater because the tree is
not only tolerant to Se but also uptakes chemical species from the environment. 相似文献
806.
807.
研究聚丙烯酸钠(PAAS)溶液的超滤行为,考察各操作参数对膜通量(J)和截留系数(R)的影响,结果表明,J随运行时间延长衰减不明显,随压差增大呈线性递增,随温度升高而增大,pH高于5时J基本不变;R随压差增大或温度升高均下降,随pH增大而增大。建立膜阻力(rf)模型,研究影响rf的主要因素,发现,rf随压差增大而增大,随温度升高而减少,pH低于5时rf随pH增大而迅速下降。研究PAAS溶液浓缩过程,当体积浓缩因子为16时,J衰减明显,截留液PAAS浓度(Cr)呈线性递增,渗透液PAAS浓度(Cp)在较长时期内基本不变,至浓缩后期,Cp轻微下降。以去离子水对浓缩液予以洗涤,随着洗涤液体积增大,Cr轻微下降,Cp逐渐趋于零。 相似文献
808.
809.
810.