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741.
Size-segregated ambient particulate matter (PM) samples were collected seasonally in suburban Nanjing of east China from 2016 to 2017 and chemically speciated. In both fine (< 2.1 µm, PM2.1) and coarse (> 2.1 µm, PM>2.1) PM, organic carbon (OC) accounted for the highest fractions (26.9% ± 10.9% and 23.1% ± 9.35%) of all measured species, and NO3− lead in average concentrations of water-soluble inorganic ions (WSIIs). The size distributions of measured components were parameterized using geometric mean diameter (GMD). GMD values of NO3−, Cl−, OC, and PM for the whole size range varied from < 2.1 µm in winter to > 2.1 μm in warm seasons, which was due to the fact that the size distributions of semi-volatile components (e.g., NH4NO3, NH4Cl, and OC) had a dependency on the ambient temperature. Unlike OC, elemental carbon (EC), and elements, NH4+, NO3−, and SO42− exhibited an increase trend in GMD values with relative humidity, indicating that the hygroscopic growth might also play a role in driving seasonal changes of PM size distributions. Positive matrix factorization was performed using compositional data of fine and coarse particles, respectively. The secondary formation of inorganic salts contributing to the majority (> 70%) of fine PM and 20.2% ± 19.9% of speciated coarse PM. The remaining coarse PM content was attributed to a variety of dust sources. Considering that coarse and fine PM had comparable mass concentrations, more attention should be paid to local dust emissions in future air quality plans. 相似文献
742.
Qiongfang Zhuo Xiaofeng Xu Shuibo Xie Xiuwen Ren Zhongying Chen Bo Yang Yanliang Li Junfeng Niu 《环境科学学报(英文版)》2022,34(6):103-113
The simultaneous electro-oxidation of Ni (II)-citrate and electrodeposition recovery of nickel metal were attempted in a combined electro-oxidation-electrodeposition reactor with a boron-doped diamond (BDD) anode and a polished titanium cathode. Effects of initial nickel citrate concentration, current density, initial pH, electrode spacing, electrolyte type, and initial electrolyte dosage on electrochemical performance were examined. The efficiencies of Ni (II)-citrate removal and nickel metal recovery were determined to be 100% and over 72%, respectively, under the optimized conditions (10 mA/cm2, pH 4.09, 80 mmol/L Na2SO4, initial Ni (II)-citrate concentration of 75 mg/L, electrode spacing of 1 cm, and 180 min of electrolysis). Energy consumption increased with increased current density, and the energy consumption was 0.032 kWh/L at a current density of 10 mA/cm2 (pH 6.58). The deposits at the cathode were characterized by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). These characterization results indicated that the purity of metallic nickel in cathodic deposition was over 95%. The electrochemical system exhibited a prospective approach to oxidize metal complexes and recover metallic nickel. 相似文献
743.
The Stakeholder Preference for Best Management Practices in the Three Gorges Reservoir Region 总被引:1,自引:0,他引:1
Jiali Qiu Zhenyao Shen Lei Chen Hui Xie Chengchun Sun Qin Huang 《Environmental management》2014,54(5):1163-1174
A qualitative analysis of in-depth interviews with 92 farmers and 42 policy managers in Wuxi County, the Three Gorges Reservoir Region, was conducted to identify stakeholder preferences for alternative best management practices (BMPs) and to determine the factors that affect their acceptance. Policy manager support for most of the practices was relatively stronger than support by farmers, except for the grade stabilization structure (GSS), hillside ditch (HD) and constructed wetland alternative, owing to their perceptions of soil benefits, economic advantages and environmental advantages. Farmers opposed those practices that occupied cultivated lands or changed the conventional planting methods, such as field border, conservation tillage (CT) and contour buffer strips. They tended to accept the BMPs with off-farm pollution reduction, such as GSS, riparian forest buffer and HD, and the BMPs associated with soil benefits, such as nutrient management and Terrace. The result that almost all respondents did not accept CT differed from reports in the existing literature. There is a significant correlation between the acceptance of some BMPs and the townships where the farmers lived (P ≤ 0.05). The environmental conditions and social factors would affect farmer support for BMPs, including local soil conditions, farming methods, economic income, education level and age. The economic advantages of the BMPs were the main motivation for farmers to accept the practices. Furthermore, intensive education efforts, financial incentives or economic subsidies may promote the adoption of the BMPs in our study area. 相似文献
744.
有机溴代苯酚类污染物在水体中普遍存在,尤其在海洋环境中,除人为污染源外,它还存在广泛的天然来源.以2,4,6-三溴苯酚为模型化合物,以氙灯(λ290 nm)作为模拟太阳光源,研究了海水中溴代苯酚的光化学过程,并系统考察了溴代苯酚初始浓度、Cl~-、Fe(Ⅲ)和pH值等环境因素的影响.实验结果表明,在海水中,2,4,6-三溴苯酚能够快速发生光化学反应,通过产物分析发现其主要产物为通过光致脱溴氯代过程产生的2,4-二溴-6-氯苯酚,并且该产物随2,4,6-三溴苯酚初始浓度、Cl~-浓度、Fe(Ⅲ)浓度的增大及溶液pH值的降低而增加.以明亮发光杆菌为受试生物的毒理学实验表明,2,4,6-三溴苯酚在海水中光化学的前期,系统的毒性效应增强,而毒性的增加可能主要由光致氯代过程导致. 相似文献
745.
PM_(2.5), formally defined as particulate matter with diameter less than 2.5 μm, is one of most harmful air pollutants threatening human health. Numerous epidemiological studies have shown that both short-term and long-term exposures to PM_(2.5) are strongly linked with respiratory diseases. In this study, various types of spatio-temporal data were collected and used to estimate the spatio-temporal variation of PM_(2.5) exposure in Beijing in 2014. The seasonal and daily variation of the population-weighted exposure level(PWEL) in 2014 was estimated and compared. The results show that the population exposure to ambient air pollution differs significantly in the four seasons, and the exposure levels in winter and spring are notably higher than the other seasons; the exposure level changes greatly from North to South, and each sub-district maintains similarity to neighboring sub-districts. 相似文献
746.
Lingyun Wang Gangdou Ding Zhiguang Zhou Xun Liu Yixiao Wang Heidi Qunhui Xie Tuan Xu Pu Wang Bin Zhao 《环境科学学报(英文版)》2017,29(1):165-172
The health risk of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like PCBs (dl-PCBs) to human being should be assessed regularly. To evaluate the contamination levels in various food products in the Chinese market and to assess the dietary exposure of the Chinese population, 11 varieties of food groups totaling 634 samples including beef and mutton, chicken and duck, pork, fish and seafood, milk and dairy products were evaluated. The average concentrations of PCDD/Fs in all groups ranged from 0.291 to 8.468 pg/g whole weight (w.w.). The average toxic equivalency concentrations were from 0.012 pg TEQ/g w.w. for cereal to 0.367 pg TEQ/g fat for marine oil. OCDD and 2,3,7,8-TCDF were the dominant congeners in foodstuffs. The dietary estimated mean intake for the Chinese rural and urban populations were 0.656 and 0.514 pg TEQ/kg body weight/day, respectively, however, the cereal group exposure were higher to the estimate daily intake and contributed 81% for rural and 48% for urban population, followed by fish and seafood which contributed 4% and 16% to the estimate daily intake. The estimated dietary intakes were compared with the toxicological reference values and showed that both rural and urban populations were well below those values. 相似文献
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748.
749.
750.
在全球变化背景下,青藏高原降水格局发生改变,并影响高寒草地温室气体排放.为了更好地认识降水变化与高寒草地温室气体排放的关系,在2015年7月24日,通过人工降水6.7 mm,研究了单次降水对高寒草地温室气体昼夜变化的影响.表明:(1)单次降水没有改变土壤温度,但显著增加了土壤湿度;(2)单次降水后24小时内,高寒草地CH4吸收量降低了2.46倍,CO2和N2 O排放量分别提高15.3%和98.9%;(3)单次降水弱化了高寒草地CH4和N2 O排放量与土壤温度的关系. 相似文献