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191.
192.
Seema Awasthi Mukesh Khare Prashant Gargava 《Environmental Modeling and Assessment》2006,11(3):267-276
Gaussian-based dispersion models are widely used to estimate local pollution levels. The accuracy of such models depends on
stability classification schemes as well as plume rise equations. A general plume dispersion model (GPDM) for a point source
emission, based on Gaussian plume dispersion equation, was developed. The program complex was developed using Java and Visual
basic tools. It has the flexibility of using five kinds of stability classification schemes, i.e., Lapse Rate, Pasquill–Gifford
(PG), Turner, σ–θ and Richardson number. It also has the option of using two types of plume rise formulations – Briggs and
Holland’s. The model, applicable for both rural and urban roughness conditions, uses meteorological and emission data as its
input parameters, and calculates concentrations of pollutant at the center of each cell in a predefined grid area with respect
to the given source location. Its performance was tested by comparing with 4-h average field data of continuous releases of
SO2 from Dadri thermal power plant (Uttar Pradesh, India). Results showed that the Turner scheme used with Holland’s equation
gives the best outcome having a degree of agreement (d) of 0.522. 相似文献
193.
Sébastien Raymond Alain Mailhot Guillaume Talbot Patrick Gagnon Alain N. Rousseau Florentina Moatar 《Journal of the American Water Resources Association》2014,50(3):791-804
Load estimates obtained using an approach based on statistical distributions with parameters expressed as a function of covariates (e.g., streamflow) (distribution with covariates hereafter called DC method) were compared to four load estimation methods: (1) flow‐weighted mean concentration; (2) integral regression; (3) segmented regression (the last two with Ferguson's correction factor); and (4) hydrograph separation methods. A total of 25 datasets (from 19 stations) of daily concentrations of total dissolved solids, nutrients, or suspended particulate matter were used. The selected stations represented a wide range of hydrological conditions. Annual flux errors were determined by randomly generating 50 monthly sample series from daily series. Annual and interannual biases and dispersions were evaluated and compared. The impact of sampling frequency was investigated through the generation of bimonthly and weekly surveys. Interannual uncertainty analysis showed that the performance of the DC method was comparable with those of the other methods, except for stations showing high hydrological variability. In this case, the DC method performed better, with annual biases lower than those characterizing the other methods. Results show that the DC method generated the smallest pollutant load errors when considering a monthly sampling frequency for rivers showing high variability in hydrological conditions and contaminant concentrations. 相似文献
194.
珠江三角洲土地利用变化对特征大气污染物扩散的影响 总被引:1,自引:0,他引:1
在珠江三角洲两种下垫面条件下,应用CALPUFF大气污染扩散模式,对特征污染物SO2、SO42-的扩散进行数值模拟,探讨大规模土地利用变化,尤其是城镇建设用地增加,对珠江三角洲地区大气污染物扩散的影响,并通过对4个典型区污染物月均质量浓度变化特征分析,揭示土地利用变化对不同地区的污染物分布的影响机制。模拟结果表明:土地利用变化,尤其是城镇建设用地增加,不利于污染物扩散,污染源下风方向地区受影响较大,污染物质量浓度明显升高,SO2和 SO42-年均质量浓度分别增加14.07%和3.31%;受影响范围、变化幅度与污染源排污强度呈正相关,变化幅度亦与污染源距离远近呈负相关。土地利用变化后,尤其是城镇建设用地增加,四个典型区 SO2月均质量浓度都表现为升高趋势,且冬季 SO2质量浓度升高幅度最大,夏季升高幅度最小,临近污染源密集区的两个典型区SO2月均质量浓度分别增加33.6%和26.3%。土地利用变化不仅改变局地的污染扩散,也会对区域的污染扩散有一定影响,尤其对污染源分布密集区的大气污染物扩散影响强度最大。因此,建议人类在城市化建设过程中尽可能保留自然斑块,消除人工下垫面对污染物扩散的负面影响。 相似文献
195.
J. L. Verdolin 《Behavioral ecology and sociobiology》2009,63(6):789-799
Few studies have experimentally tested the resource dispersion hypothesis (RDH). In this study, I tested whether space use
and social organization of Gunnison’s prairie dog responded to changes in the dispersion and abundance of resources. Food
manipulations were carried out during the reproductive and nonreproductive seasons across 2 years. Gunnison’s prairie dog
adults responded to the experiments by decreasing territory size as food became patchier in space and time. Both males and
females modified their home ranges, with no detectable difference between sexes, either prior to or during the experiments.
As food became patchier in space and time, the spatial overlap of adults increased, whereas it decreased as food became more
evenly dispersed. The average size of a group, defined as those individuals occupying the same territory, did not change significantly
as a result of the experiments. Where changes in the composition and size of groups did occur, there was no indication that
such changes were sex specific. Results from this study support critical components of the RDH and strongly suggest that patterns
of space use and social structure in Gunnison’s prairie dogs are the result of individual responses to resource abundance
and distribution. 相似文献
196.
《Process Safety and Environmental Protection》2014,92(6):616-624
Products of a hydrocarbon fire accident have both chronic and acute health effects. They cause respiratory issues to lung cancer. While fire is the most frequent phenomenon among the offshore accidents, predicting the contaminants’ concentration and their behavior are key issues. Safety measures design, such as ventilation and emergency routes based only on predicted contaminants’ concentration seems not to be the best approach. In a combustion process, various harmful substances are produced and their concentration cannot be added. The time duration that any individual spends in different locations of an offshore installation also varies significantly. A risk-based approach considers the duration a person is exposed to contaminants at various locations and also evaluates the hazardous impacts. A risk-based approach has also an additivity characteristic which helps to assess overall risk.Through the current study, an approach is proposed to be used for risk assessment of combustion products dispersion phenomenon in a confined or semi-confined facility. Considering CO, NO2 and CH4 as the contaminants of concern, the dispersion of the substances over the layout of the facility after a LNG fire is modeled. Considering different exposure times for three major parts of the facility including the processing area, office area and the accommodation module, the risk contours of CO, NO2 and CH4 over the entire facility are developed. The additivity characteristic of the risk-based approach was used to calculate the overall risk. The proposed approach helps to better design safety measures to minimize the impacts and effective emergency evacuation planning. 相似文献
197.
A tool for the quantification of the consequences of toxic dispersions coming from fires in warehouses has been developed. This tool is expected to be applied in the framework of the risk assessment in Catalonia, specifically in the Quantitative Risk Assessment. The present study is based on the criteria gathered in the technical guide BEVI 3.2 and the methodology CPR-15 used in the Netherlands. Hence, the approach performed accepts the main body of the foresaid methodology but implements a different and free source dispersion model, a modified Gaussian model that takes into account the warehouse effect. In the work conducted, a historical analysis of accidents involving fire in warehouses has been performed in order to justify the importance of assessing their potential toxic dispersions. Furthermore, the tool has been tested in different case studies providing results that have been compared with other methodologies, observing similar results that can be useful for the stakeholders and decision makers in the framework of the risk assessment. 相似文献
198.
为分析不同粉尘因密度的差异对20 L球形爆炸装置球罐内粉尘分散过程流场变量变化和点火延迟时间的影响,利用CFD数值模拟的方法,研究了3种不同密度的粉尘在球罐分散过程中湍流动能、流场速度、粉尘浓度3种流场变量在球心处的变化规律。研究结果表明:在其他条件一致的情况下,粉尘密度越小,湍流动能的峰值越小,粉尘云浓度和流场速度的峰值则越大;粉尘密度对湍流动能的增值速率没有影响,而粉尘密度越小,流场速度和粉尘浓度的增值速率越快,粉尘浓度衰减至稳定值的时间也越短。表明粉尘密度越小,点火延迟时间也越小,因此,建议铝粉点火延迟时间在50~60 ms之间,锆粉和锌粉在60~80 ms之间。 相似文献
199.
利用CALPUFF对安徽和河南秸秆焚烧的模拟与研究 总被引:2,自引:1,他引:1
秸秆焚烧会产生大量的颗粒物(PM)、氮氧化物、有机碳、苯以及多环芳烃等污染物,不仅影响空气质量,危害人体健康,而且大大降低能见度,对交通运输构成威胁. 针对安徽和河南2009年6月严重的秸秆焚烧现象,对CALPUFF模拟系统和FEPS模型进行重新编译与整合,对空气动力学直径小于10 μm的颗粒物(PM10)进行扩散模拟,得到逐时ρ(PM10)的烟羽扩散,并对模拟结果进行分析. 结果表明,秸秆焚烧过程中焚烧点附近的ρ(PM10)较大,研究区域内部分区域的日均ρ(PM10)大于我国二级标准(150 μg/m3)甚至三级标准(350 μg/m3). 如果考虑二次粒子,其影响程度会更加严重. 相似文献
200.
An ecological risk assessment model for a pulsed contaminant emission into a wetland channel flow 总被引:1,自引:0,他引:1
As a continuation of the modelling on ecological degradation and hydraulic dispersion of pollutant emission into an idealized two-dimensional free-surface wetland flow (Zeng, L., Chen, G.Q., 2009b. Ecological degradation and hydraulic dispersion of contaminant in wetland. Ecol. Model., doi:10.1016/j.ecolmodel.2009.10.024), an ecological risk assessment model for the typical case of a pulsed contaminant emission into a realistic three-dimensional wetland channel flow is presented in this paper for the fate of cross-sectional mean concentration under environmental dispersion. An environmental dispersion model for the mean concentration is devised as an extension of Taylor’s classical analysis on dispersion in fluid flows. The velocity distribution and the environmental dispersivity in the fully developed steady flow through the wetland is found and illustrated with limiting cases covering various known solutions for the porous media flow between parallel plates, flow in a shallow wetland, sweeping flow in a densely vegetated wetland, and single phase flow in a channel. Obtained by Aris’s method of moments, the environmental dispersivity is shown characterized with multi-scale asymptotic time variations with stem dominated stage, transitional stage, and width-depth-stem dominated stage. Based on the solution for the evolution of contaminant cloud in the wetland channel flow, critical length and duration of the contaminant cloud with concentration beyond given environmental standard level are concretely illustrated for typical pollutant constituents in wastewater emission. Under the same emission intensity and environmental standard, the duration of contaminant cloud in the wetland channel is revealed shorter than that in a free surface wetland, due to the lateral effect. 相似文献