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991.
Morville S Scheyer A Mirabel P Millet M 《Environmental science and pollution research international》2006,13(2):83-89
Goal, Scope and Background Atmospheric sampling (gas and particles) of 5 phenols (phenol, m-cresol, p-cresol, o-cresol, pentachlorophenol) and 15 nitrophenols
(3-methyl-2-nitrophenol, 3-nitrophenol, 4-methyl-2-nitrophenol, 5-methyl-2-nitrophenol, 2-methyl-3nitrophenol, 3-methyl-4-nitrophenol,
2,6-dinitrophenol, bromoxynil, 2,5-dinitrophenol, 2,6-dinitro-p-cresol, 2,4-dinitrophenol, ioxynil, DNOC, 3,4-dinitrophenol,
dinoseb) on XAD-2 resin (20 gr) and glass fibre filters, respectively, were performed in 2002 by using 'Digitel DA80' high
volume samplers. These measurements were undertaken in order to show spatial and geographical variations of concentrations
and the role of traffic in the emissions of these compounds to the atmosphere.
Methods Sampling were performed in Strasbourg (eastern France), in its vicinity (Schiltigheim) and in Erstein. Sites were chosen
to be representative of urban (Strasbourg), suburban (Schiltigheim) and rural (Erstein) conditions. Field campaigns were undertaken
simultaneously in urban and suburban sites during all the seasons during 4 hours at a flow rate of 60 m3.h-1, which gives
a total of 240 m3 of air per sample. Period of sampling varied between 06h00 to 10h00, 11h00 to 15h00 and 18h00 to 22h00 in
order to evaluate a variation of concentration during automobile traffic between urban, suburban and rural areas. Gas and
particle samples were separately Soxhlet extracted for 12 h with a mixture of CH2Cl2 / n-hexane (50:50 v/v), concentrated
to about 1 mL with a rotary evaporated and finally dried under nitrogen. Dry extracts were dissolved in 1 mL of CH3CN. Before
analysis, extracts were sylilated by using MTBSTFA. Analysis was performed by GC/MSD in the SIM mode.
Results and Discussion Partitioning of phenolic compounds between gas and particle phases seems to be mainly correlated with vapour pressure. Among
phenolic compounds analysed, phenol, p-cresol, pentachlorophenol and 2.4-dinitrophenol were detected in all samples and emissions
from traffic seems to be the major source for the presence of these compounds to the atmosphere. No increase of concentrations
in autumn tend to confirm this hypothesis since, with the use of domestic heating in colder months, increases of PAHs concentrations
were observed and these compounds are known to be emitted by all combustion processes.
Pentachlorophenol is a special case since this molecule is only used as wood preservative. Its presence in all atmospheric
samples, whatever the locations and the period of time is the consequence of its persistence.
Conclusions and Perspectives These measurements demonstrate that phenols and nitrophenols are emitted to the atmosphere and further measurements, in order
to confirm their sources, their behaviour and their potential impact to the air quality and to human health should be undertaken
especially since the literature collected is relatively old. Concentrations of pentachlorophenol measured are very low and,
due to its toxicity, further investigations should be undertaken.
- * The basis of this peer-reviewed paper is a presentation at the 9th FECS Conference on 'Chemistry and Environment', 29 August
to 1 September 2004, Bordeaux, France. 相似文献
992.
In settings where measurements are costly and/or difficult to obtain but ranking of the potential sample data is relatively easy and reliable, the use of statistical methods based on a ranked-set sampling approach can lead to substantial improvement over analogous methods associated with simple random samples. Previous nonparametric work in this area has been concentrated almost exclusively on the one- and two-sample location problems. In this paper we develop ranked-set sample procedures for the m-sample location setting where the treatment effect parameters follow a restricted umbrella pattern. Distribution-free testing procedures are developed for both the case where the peak of the umbrella is known and for the case where it is unknown. Small sample and asymptotic null distribution properties are provided for the peak-known test statistic. 相似文献
993.
994.
一种基于Logistic回归的全损飞行事故分析与预测 总被引:3,自引:0,他引:3
运用Logistic回归方法分析全损飞行事故的影响因素,并构建预测模型,然后利用飞行事故案例进行了实证检验。通过对样本数据过离散、空单元、多元共线性和特异值、特殊影响案例的诊断,以及对模型的拟合程度和预测效果的检验,表明所构建的模型比较符合现实情况,而且具有较好的拟合程度和预测效果。模型指出航班类型和机龄因素具有统计学意义,国内航班比国际航班的全损概率要高;机龄越老,全损概率越高。 相似文献
995.
Stream macroinvertebrate communities vary naturally among types of habitats where they are sampled, which affects the results of environmental assessment. We analyzed macroinvertebrates collected from riffle and snag habitats to evaluate influences of habitat-specific sampling on taxon occurrence, assemblage measures, and biotic indices. We found considerably more macroinvertebrate taxa unique to snags (143 taxa) than to riffles (75 taxa), and the numbers of taxa found in both riffles and snags (149 taxa) were similar to that found in snags. About 64% of the 47 macroinvertebrate measures we tested differed significantly between riffles and snags. Eighty percent intercepts of regressions between biotic indices and urban or agricultural land uses differed significantly between riffles and snags. The Hilsenhoff biotic index calculated from snag samples explained 69% of the variance of riffle samples and classified 66% of the sites into the same stream health group as the riffle samples. However, four multimetric indices for snag samples explained less than 50% of the variance of riffle samples and classified less than 50% of the sites into the same health group as the riffle samples. We concluded that macroinvertebrate indices developed for riffle/run habitat should not be used for snag samples to assess stream impairment. We recommend developing an index of biotic integrity specifically for snags and using snags as an alternate sampling substrate for streams that naturally lack riffles. 相似文献
996.
Patchy Distribution Fields: Sampling Distance Unit of an Interleaved Survey and Reconstruction Adequacy 总被引:1,自引:1,他引:0
Kalikhman I 《Environmental monitoring and assessment》2006,118(1-3):147-163
A mathematical model was used to examine the effects of choosing various units of sampling distance of an interleaved (two-pass)
acoustic survey on the adequacy of reconstructing patchy distribution fields. The model simulates fish or plankton patches
(or gaps) of different shapes and spatial orientations, and an interleaved survey by parallel or zigzag transects, along which
a unit of sampling distance is set. The efficiency of a survey is determined by the adequacy of a reconstructed field to that
originally generated, which is evaluated by calculating their correlations (r). Regarding immovable fields, the experiments conducted indicate that a patchy field can be reconstructed properly (r
2 > 0.70) if the distance between transects D < (1.5–2.0)R and the unit of sampling distance d < (1.5– 2.0)R
p. As, for regular surveys d < (1.0–1.5)R
p, it may be concluded that interleaved surveys are more efficient than regular ones because of the factor studied. In regard
to movable fields, a comparison of the results of interleaved surveys with those of regular surveys directly indicates that
the former may ensure a more adequate field reconstruction than the latter do. This fact confirms the previous conclusion
that an interleaved survey is expedient in cases where there is no preference regarding the position of a vessel for further
work. 相似文献
997.
Paul L. Mosquin Jeremy Aldworth Phillip S. Kott Wenlin Chen Shanique Grant 《Journal of the American Water Resources Association》2023,59(1):16-28
The estimation of upper percentiles of chemical concentrations in surface water systems within sites and regions may be necessary for the assessment of potential risk to ecosystems and human health. Limited sample sizes at monitoring sites often limit the use of direct methods to estimate upper percentiles. In such cases, upper percentiles within regions within a time frame may be estimated by pooling data across sites and years, and then deriving percentile estimates from the pooled dataset. The method uses the observations resulting from either a known probability-sampling design or a sampling design treated like one because its observations come close to matching that of a probability-sample. These observations are then weighted to ensure that estimates are representative of a target population across all the sites within the region and the range of years in the time frame. This method of estimating upper percentiles of annual site concentration profiles is demonstrated using atrazine and validated using the monitoring data from both sparsely sampled and high-frequency water monitoring programs, where point and interval estimates of the 90th, 95th, and 99th pooled population percentiles are provided. This method shows that the pooled data from multiple sparse datasets can be used to provide estimates of near-peak concentrations with greater certainty, which are consistent with those generated by high-frequency sampling monitoring programs. 相似文献
998.
扩散采样法观测氨的环境浓度 总被引:1,自引:0,他引:1
用被动的扩散采样方法,以磷酸溶液为浸渍试剂吸收室内,外大气环境中的气态氨,然后用分光光度法测定水提取液中的NH^+4,在被观测的3个公寓住宅中,室内氨的平均浓度均高于同期室外氨的平均浓度,初步表明在人类本身可能也是氨的一个来源。 相似文献
999.
将计算机技术应用于采样仪中,实现人-机对话,同时配以运行可靠,成本较低的水样采集,贮存和转换等部件,实现自动采样,达到智能化的目的。采样仪的控制采用单片机技术,以8031芯片作为微处理器,配以外围接口电路和功能键盘,体积小,成本低。采集贮存系统由蠕动泵,电磁铁及配套的机械传动装置,水样贮存盘和容器等组成,结构简单,运行平稳。采样有连续采样和间歇采样2种功能,并可按需要任意调节采样时间,采样周期,切 相似文献
1000.
As an effective way to construct and maintain various life pipelines in urban areas and industrial parks, the underground utility tunnel has been developed rapidly in China in recent years. However, the natural gas pipeline leakage in a utility tunnel may cause fire, explosion or other coupling disastrous accidents that could result in fatal consequences. The effective source term estimation (STE) of natural gas leakage can provide technical supports for emergency response during natural gas leakage accidents in utility tunnels. In this paper, a STE model with the combination of gas transport model, Bayesian inference and slice sampling method is proposed to estimate the source parameters of natural gas leakage in underground utility tunnels. The observed data can be integrated into the gas transport model and realize the inversion of natural gas leakage location and release rates. The parameter sensitivity analysis is presented to evaluate the robustness of the proposed model with good practicability, and the gas sensor layouts in the utility tunnel are analyzed and optimized. The spatio-temporal distribution of the leaked gas could be well predicted based on the estimation source parameters by the proposed STE model. The results show that the proposed model is an alternative and effective tool to provide technical supports for loss prevention and mitigation for natural gas leakage accidents in urban utility tunnels. 相似文献