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981.
杜卓勋 《湖南环境生物职业技术学院学报》2001,7(2):49-50
针对“极限”概念提出了一些见解,并从理论上描述和给出了“极限”的精确定义,从该定义出发,更有助正确理解和掌握“极限”的内在含义。 相似文献
982.
Han Zhenzhen Yang Luze Du Meijin Li Yu 《Environmental science and pollution research international》2020,27(31):38805-38818
Environmental Science and Pollution Research - In the proposed model, the estrogen activity values and thyroid hormone activity values of PAEs molecules were normalized using the TOPSIS method by... 相似文献
983.
山东新汶矿业集团翟镇煤矿通过不断引进、消化和吸收国内外先进生产技术,走科技创新之路,这个昔日饱受顶板破碎干扰、生产条件复杂的大型矿井在短短几年的时间内实现了采掘机械化、辅助自动化、控制智能化,先后有136项科技项目首开国内先河,其中32项达到了国际先进水平。为推动“科技兴矿”战略的实施,翟镇煤矿采取了一系列有效措施: 相似文献
984.
Xuan Ban Qiuzhen Wu Baozhu Pan Yun Du Qi Feng 《Environmental monitoring and assessment》2014,186(7):4237-4247
Composite Water Quality Identification Index (CWQII) and multivariate statistical techniques were used to investigate the temporal and spatial variations of water quality in Honghu Lake. The aims are to explore the characteristics of water quality trends in annual, monthly, and site spatial distribution and to identify the main pollution factors. The results showed that the values of CWQII increased from 2.0 to 4.0 from the years 2001 to 2005, then decreased from 2006 and kept a balance between 2.0 and 3.0 from 2006 to 2011, indicating that the water quality of Honghu Lake deteriorated from 2001 to 2005 and has gradually improved since 2006, which were likely achieved after water protection measurements taken since 2004. The monthly change rules of water quality were influenced by a superposition of natural processes and human activities. In samples numbered 1–9 from upstream to downstream, the maximum values of CWQII often occurred in sample site 9 while the minimum ones often occurred in sample site 2, indicating that the water quality near the upstream tributary was the poorest and that in the core zone was the best. Incoming water from the trunk canal of the Sihu area upstream was the largest pollution source. The sensitive pollution nutrients were mainly caused by the total nitrogen, followed by the total phosphorus. 相似文献
985.
Malaj E Rousseau DP Du Laing G Lens PN 《Environmental monitoring and assessment》2012,184(4):1823-1839
The heavy metal contamination in Lake Ohrid, a lake shared between Albania and Macedonia, was studied. Lake Ohrid is believed
to be one of the oldest lakes in the world, with a large variety of endemic species. Different anthropogenic pressures, especially
heavy metal influxes from mining activities, might have influenced the fragile equilibrium of the lake ecosystem. Heavy metal
concentrations in water, sediment, emergent vegetation, and fish were investigated at selected sites of the lake and a study
of the heavy metals in five tributaries was conducted. The lake surface water was found to have low levels of heavy metals,
but sediments contained very high levels mostly near river mouths and mineral dump areas with concentrations reaching 1,501 mg/kg
for Ni, 576 mg/kg for Cr, 116.8 mg/kg for Co and 64.8 g/kg for Fe. Sequential extraction of metals demonstrates that heavy
metals in the sediment are mainly present in the residual fraction varying from 75% to 95% in different sites. High heavy
metal levels (400 mg/kg Ni, 89 mg/kg Cr, and 39 mg/kg Co) were found in plants (stem of Phragmites australis), but heavy metals could not be detected in fish tissue (gill, muscle, and liver of Salmo letnica and Salmothymus ohridanus). 相似文献
986.
The concentrations of polycyclic aromatic hydrocarbons (PAHs) were determined in groundwater and soil profiles from upland field and paddy field in the Hunpu wastewater-irrigated area of northeast China. In the study area, the peak concentrations of total PAHs were within or just below the topsoil, and the contents decline with depth at various trend verified by the Spearman's rank correlation test. The total PAH concentrations in upland soil layers ranged from 46.8 to 2,373.0 microg/kg (dry wt.), while the concentrations in paddy soil layers ranged from 23.1 to 1,179.1 microg/kg (dry wt.). The 16 priority PAHs were all detected in the analyzed soil samples, and naphthalene (Nap), phenanthrene (Phe), fluoranthene (Fla), chrysene (Chr), and benzo[a]pyrene (Bap) were selected for further study in terms of their vertical distributions. The concentrations of both total and individual PAHs in upland soil were generally higher than those in the corresponding layers of paddy soil. The concentrations of total and individual PAH were notably different between the corresponding horizons in upland and paddy soil were probably attribute to the different sources and properties of the PAHs and soil; different methods of soil tillage and plant growing. Special PAH compound ratios, such as phenanthrene/anthracene, fluoranthene/pyrene, LMW/HMW, and parent PAH ratios (Ant/178, Fla/202, BaA/228, and Ilp/276) were used to identify the source of soil PAHs. The data suggests that the possible sources of PAHs in the Hunpu wastewater-irrigation area are the incomplete combustion of coal, petroleum and crude oil, automobile exhausts. These sources lead to pollution of the soil and groundwater by wet/dry deposition and vertical downward migration. 相似文献
987.
Yujie Sha Huan Wu Yue Guo Xi Liu Yan Mo Qiyuan Yang Shumao Wei Kunling Long Du Lu Ying Xia Weiwei Zheng Zhiheng Su Xiao Wei 《环境科学学报(英文版)》2022,34(7):91-104
Iodoacetic acid(IAA) is an unregulated disinfection byproduct in drinking water and has been shown to exert cytotoxicity, genotoxicity, tumorigenicity, and reproductive and developmental toxicity. However, the effects of IAA on gut microbiota and its metabolism are still unknown, especially the association between gut microbiota and the metabolism and toxicity of IAA. In this study, female and male Sprague–Dawley rats were exposed to IAA at 0 and 16 mg/kg bw/day daily for 8 weeks by oral gavage.... 相似文献
988.
989.
990.
Formation characteristics of aerosol particles from pulverized coal pyrolysis in high-temperature environments 总被引:1,自引:0,他引:1
Chen WH Du SW Yang HH Wu JS 《Journal of the Air & Waste Management Association (1995)》2008,58(5):702-710
The formation characteristics of aerosol particles from pulverized coal pyrolysis in high temperatures are studied experimentally. By conducting a drop-tube furnace, fuel pyrolysis processes in industrial furnaces are simulated in which three different reaction temperatures of 1000, 1200, and 1400 degrees C are considered. Experimental observations indicate that when the reaction temperature is 1000 degrees C, submicron particles are produced, whereas the particle size is dominated by nanoscale for the temperature of 1400 degrees C. Thermogravimetric analysis of the aerosol particles stemming from the pyrolysis temperature of 1000 degrees C reveals that the thermal behavior of the aerosol is characterized by a three-stage reaction with increasing heating temperature: (1) a volatile-reaction stage, (2) a weak-reaction stage, and (3) a soot-reaction stage. However, with the pyrolysis temperature of 1400 degrees C, the volatile- and weak-reaction stages almost merge together and evolve into a chemical-frozen stage. The submicron particles (i.e., 1000 degrees C) are mainly composed of volatiles, tar, and soot, with the main component of the nanoscale particles (i.e., 1400 degrees C) being soot. The polycyclic aromatic hydrocarbons (PAHs) contained in the aerosols are also analyzed. It is found that the PAH content in generated aerosols decreases dramatically as the pyrolysis temperature increases. 相似文献