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221.
222.
介绍放射性平行样品服从的统计分布,据此提出平行样品结果统计检验方法,用该方法对1组平行样品结果做统计检验,并与计算标准偏差的检验方法作比对。结果表明,虽然2种检验方法得出了相反的结论,但统计检验方法的结果更符合放射性测量的规律。 相似文献
223.
小白菜的干鲜状态对其铅的生物可给性的影响(Effects of Dry and Fresh States of Brassica chinensis on the Oral Bioaccessibility of Lead) 总被引:2,自引:0,他引:2
为了研究小白菜的干鲜状态对其铅的生物可给性的影响,设置了对照(不添加铅,本底值为32.37mg·kg-1)、300mg·kg-1和500mg·kg-13种土壤铅浓度处理的盆栽实验,并将收获的小白菜分别以干样和鲜样进行基于生理学的invitro人工胃肠模拟实验,测定其中铅的生物可给性.结果表明:栽种2个月后,小白菜铅含量分别达到0.38mg·kg-1、4.55mg·kg-1和12.50mg·kg-1(干重),对铅的富集系数分别为0.012、0.015和0.025,可能存在较高的健康风险.invitro实验表明:样品干鲜状态、铅浓度处理以及二者的交互效应是影响铅的生物可给性的重要因素.无论干样还是鲜样,铅在胃阶段和小肠阶段的溶解态量均随样品铅含量的增加而线性增加;对于同一铅浓度处理,鲜样中铅的生物可给性无论在胃阶段还是小肠阶段均显著高于干样(p<0.01).使用干样进行健康风险评价可能会低估小白菜中的铅对人体的健康风险. 相似文献
224.
External drift kriging of NOx concentrations with dispersion model output in a reduced air quality monitoring network 总被引:1,自引:0,他引:1
Jan van de Kassteele Alfred Stein Arnold L. M. Dekkers Guus J. M. Velders 《Environmental and Ecological Statistics》2009,16(3):321-339
In the mid nineteen eighties the Dutch NOx air quality monitoring network was reduced from 73 to 32 rural and city background stations, leading to higher spatial uncertainties.
In this study, several other sources of information are being used to help reduce uncertainties in parameter estimation and
spatial mapping. For parameter estimation, we used Bayesian inference. For mapping, we used kriging with external drift (KED)
including secondary information from a dispersion model. The methods were applied to atmospheric NOx concentrations on rural and urban scales. We compared Bayesian estimation with restricted maximum likelihood estimation and
KED with universal kriging. As a reference we also included ordinary least squares (OLS). Comparison of several parameter
estimation and spatial interpolation methods was done by cross-validation. Bayesian analysis resulted in an error reduction
of 10 to 20% as compared to restricted maximum likelihood, whereas KED resulted in an error reduction of 50% as compared to
universal kriging. Where observations were sparse, the predictions were substantially improved by inclusion of the dispersion
model output and by using available prior information. No major improvement was observed as compared to OLS, the cause presumably
being that much good information is contained in the dispersion model output, so that no additional spatial residual random
field is required to explain the data. In all, we conclude that reduction in the monitoring network could be compensated by
modern geostatistical methods, and that a traditional simple statistical model is of an almost equal quality.
相似文献
Jan van de KassteeleEmail: |
225.
Hosung Ahn 《Journal of the American Water Resources Association》1999,35(2):301-310
ABSTRACT: Atmospheric deposition can be a significant source of phosphorus to South Florida's aquatic system. Deposition samples are often contaminated to varying degrees by bird droppings or other foreign materials. This study attempted to use statistical and other methods to detect and remove the outliers in the rain-borne total phosphorus concentration data. Some outliers in the data were identified using field notes derived from visual inspection of the samples. Outlier detection statistics based on a simple linear regression were then used for additional data screening. As a result of these analyses, about 35 percent of the observed values were identified as outlying data which needed to be removed prior to further data analyses. Based on detected outliers in the data from 15 monitoring sites, a lumped cutoff value of 130 4mUg/L was determined. This lumped cutoff value may be useful for further quality control and analyses of the data from the region. 相似文献
226.
Although most post-season harvest surveys are conducted at the state level, the effective management of wildlife populations often requires estimates of hunting success rate, hunting pressure and harvest at the sub-area (such as management unit, regional, or county) level.Sample sizes for some sub-areas are often very small or even zero. Because of small sample sizes, estimates for small sub-areas often yield unacceptably large standard errors. In this article, a hierarchical Bayes model is used to estimate hunting success rates at the sub-area level from post-season harvest surveys. The computation is done by Gibbs sampling and adaptive rejection sampling techniques. The method is illustrated using data from the Missouri Turkey Hunting Survey 1994 Spring Season. The Bayesian estimates are close to the frequency estimates for the sub-areas with large sample sizes and more stable than the frequency estimates for those with small sample sizes. The Bayesian estimates will be more useful to wildlife biologists in estab-lishing hunting regulation on small sub-areas at no additional survey cost. 相似文献
227.
水中微量甲基膦酸类化合物的树脂富集与GC/MS分析 总被引:3,自引:0,他引:3
本文使用三种阴离子交换树脂(即大孔弱碱型D-301-R,强碱型D-296,201X7)柱对水中微量甲基膦酸类化合物的富集方法进行了研究。含磷毒剂降解产物的水样用气相色谱/质谱法进行定性定量分析。结果表明,D-301-R阴离子交换树脂柱对甲基膦酸的富集回收率高于60%。 相似文献
228.
DX—100型离子色谱仪用于冰雪样品中阴,阳离子的测定 总被引:9,自引:0,他引:9
本文介绍了DX-100型离子色谱仪用于冰雪样品中阴,阳离子的测定,以东北五大连池地区白龙洞和水晶宫为例,介绍了阴,阳离子测定在分析化学物质来源和成冰过程中的重要作用。 相似文献
229.
230.
以无锡市区5个省级开发区为研究对象,基于抽样调查资料,从土地利用结构、土地利用强度和投入产出等方面分析了无锡市区省级开发区土地利用现状,对不同行业土地集约利用状况进行了定量评价。结果显示:电气机械及器材制造业土地集约利用水平较高,在08以上;交通运输设备制造业、通用设备制造业和通信设备、计算机及其他电子设备制造业的土地集约利用水平在075以上;橡胶制品业的综合集约度在07以上;其次是专用设备制造业和仪器仪表及文化、办公用机械制造业,为06以上;塑料制品业、金属制品业、纺织业和化学原料及化学制品制造业的土地集约利用水平相对较低,不到06。要合理控制开发区规模,不断提高开发区的经济效益;对新进项目设置明确的入园门槛,加大开发区内部的空间挖潜力度;完善土地利用的管理机制,严格开发区内工业用地的招拍挂出让制度。建立集约用地的考核制度,加强对集约用地的监督 相似文献