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101.
An assessment of levels of endosulfan and endosulfan sulphate in rats collected from a plot sprayed with endosulfan was carried
out for a period of four months. The analysis was carried out in the livers, muscles and fatty tissues of the rats using Gas
Chromatography. Samples were ground with sodium sulphate and aluminium oxide and the analyte soxhlet extracted with hexane.
The extract was then cleaned by florisil column chromatography. Levels of endosulfan in rats were found to range in livers
from 0.356 to 5.807 ppb, in muscles from 0.089 to 5.167 ppb and in fatty tissues from 0.083 to 4.785 ppb. Levels of endosulfan
sulphate correlated well with those of endosulfan and ranged in livers from 0.00 to 3.96 ppb, in muscles from 0.00 to 3.37 ppb
and in fatty tissue from 0.00 to 2.93 ppb. In the control rats samples, collected from an unsprayed area in the city of Harare
(University of Zimbabwe), no endosulfan could be detected. 相似文献
102.
J. V. Zidek R. White W. Sun R.T. Burnett N.D Le 《Environmental and Ecological Statistics》1998,5(2):99-105
This paper presents the results of a reconsideration of earlier work that finds an association between daily hospital admissions for respiratory distress and daily concentrations of sulphate (lag 1) as well as daily maximum concentrations of ozone (lags 1 and 3). These associations are found even after clustering the data by hospital of admission and accounting for the effects of temperature. We use an adaptation of their generalized estimating equation technique for clustered data, that daily data being for southern Ontario summers from 1983 to 1988. Like them, we adjust for daily maximum temperatures. However, unlike the earlier work returned to ours includes daily average humidity as a potential explanatory variable in our model. Our analysis also differs from theirs in that we cluster the data by census subdivision to reduce the risk of confounding pollutant levels with population size within regions. Moreover, we log-transform the explanatory variables and then high-pass filter the resulting data. We also deviate from the earlier analysis by taking account of measurement error incurred in using surrogate measures of the explanatory variables. To do so we use new methodology designed for our study but of potential value in other applications. That methodology requires a spatial predictive distribution for the unmeasured explanatory variables. Each day about 700 missing measurements for each of these variables can then be imputed over the geographical domain of the study. With these imputations we get a measure of imputation error through the covariance of the predictive distribution. Along with the predictive distribution we require an impact model to link-up with the predictive distribution. We describe that model and show how it uses the imputed measurements of the missing values of the explanatory variables. We also show how through that model, uncertainty about these values is reflected in our analysis and in commensurate uncertainties in the inferences made. Apart from its substantive objectives, our analysis serves to test the new methods with the earlier results serving as a foil. The reassuring qualitative agreement between our findings and the earlier results seems encouraging. 相似文献
103.
乙草胺与硫酸铜对黑土微生物的复合生态影响 总被引:3,自引:1,他引:2
为了探究2种不同类型农药联合施用对土壤微生物的复合生态影响,以除草剂乙草胺和杀菌剂硫酸铜为例,采用传统毒理学方法和BIOLOG法对其进行评价.结果表明,乙草胺和硫酸铜的联合施用对细菌、放线菌和真菌活菌量以及土壤脱氢酶活性基本呈现急性抑制效应,但随时间延长其作用逐渐减弱甚至发生逆转,而对土壤底物诱导呼吸强度表现为明显促进.利用Shannon、Simpson和McIntosh多样性指数模型和主成分分析法对BIOLOG数据进行分析,表明2种农药的联合施用显著破坏了黑土微生物群落物种多样性的丰富度和均一性,主成分分析法也表明土壤微生物群落碳源利用多样性发生了改变. 相似文献
104.
105.
Adsorption and desorption of 137Cs by acid sulphate soils from the Nakhon Nayok province, South Central Plain of Thailand located near the Ongkarak Nuclear Research Center (ONRC) were investigated using a batch equilibration technique. The influence of added limestone (12 and 18 tons ha?1) on 137Cs adsorption–desorption was studied. Based on Freundlich isotherms, both adsorption and desorption of 137Cs were nonlinear. A large portion (98.26–99.97%) of added 137Cs (3.7?×?103?7.03?×?105 Bq l?1) was sorbed by the soils with or without added lime. The higher lime treatments, however, favoured stronger adsorption of 137Cs as compared with soil with no lime, which was supported by higher K ads values. The addition of lime, the cation exchange capacity and pH of the soil increased and hence favoured the stronger adsorption of 137Cs. Acid sulphate soils with a high clay content, medium to high organic matter, high CEC, and predominant clay types consisting of a mixture of illite, kaolinite, and montmorillonite were the main soil factors contributing to the high 137Cs adsorption capacity. Competing cations such as NH4 +, K+, Na+, Ca2+, and Mg2+ had little influence on 137Cs adsorption as compared with liming, where a significant positive correlation between K ads and soil pH was observed. The 137Cs adsorption–desorption characteristics of the acid sulphate soils studied exhibited a very strong irreversible sorption pattern. Only a small portion (0.09–0.58%) of 137Cs adsorbed at the highest added initial 137Cs concentration was desorbed by four successive soil extractions. Results clearly demonstrated that Nakhon Nayok province acid sulphate soils have a high 137Cs adsorption capacity, which limits the 137Cs bioavailability. 相似文献
106.
107.
J. Ovadnevaite D. Ceburnis K. Plauskaite-Sukiene R. Modini R. Dupuy I. Rimselyte M. Ramonet K. Kvietkus Z. Ristovski H. Berresheim C.D. O'Dowd 《Atmospheric environment (Oxford, England : 1994)》2009,43(32):4968-4974
High time resolution aerosol mass spectrometry measurements were conducted during a field campaign at Mace Head Research Station, Ireland, in June 2007. Observations on one particular day of the campaign clearly indicated advection of aerosol from volcanoes and desert plains in Iceland which could be traced with NOAA Hysplit air mass back trajectories and satellite images. In conjunction with this event, elevated levels of sulphate and light absorbing particles were encountered at Mace Head. While sulphate concentration was continuously increasing, nitrate levels remained low indicating no significant contribution from anthropogenic pollutants. Sulphate concentration increased about 3.8 μg m−3 in comparison with the background conditions. Corresponding sulphur flux from volcanic emissions was estimated to about 0.3 TgS yr−1, suggesting that a large amount of sulphur released from Icelandic volcanoes may be distributed over distances larger than 1000 km. Overall, our results corroborate that transport of volcanogenic sulphate and dust particles can significantly change the chemical composition, size distribution, and optical properties of aerosol over the North Atlantic Ocean and should be considered accordingly by regional climate models. 相似文献
108.
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