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771.
High density polyethylene (HDPE)/bamboo composites with different nanoclay and maleated polyethylene (MAPE) contents were
fabricated by melt compounding. The compounding characteristics, clay dispersion, HDPE crystallization, and mechanical properties
of the composites were studied. The equilibrium torque during compounding decreased with use of clay masterbatch and increased
with the addition of MAPE. The X-ray diffraction (XRD) data showed that the clay was exfoliated only when 1% clay was added
to pure HDPE without MAPE. For HDPE/bamboo systems, MAPE was necessary to achieve clay exfoliation. For pure HDPE system,
both dynamic and static bending moduli increased, while impact strength decreased with increased clay loading. For the HDPE/bamboo
fiber composites, tensile strength, bending modulus and strength were improved with the use of MAPE. The use of the clay in
the system led to reduced mechanical properties. Techniques such as pre-coating fibers with clay–MAPE mixture are needed to
enhance the synergetic effect of the clay and bamboo fiber on the composite properties in the future study. 相似文献
772.
Commercial composting operations generally do not accept organic wastes with plastic twines from the greenhouse vegetable industry and the bulk of the waste materials ends up in landfills. The objectives of this paper are to identify environmentally compatible substitutes that could replace the current use of petrochemically derived plastic twines in greenhouse vegetable production, thus diverting them from landfills, and to assess the extent of their degradation via composting. Physical properties of the twines, including linear density, percent weight loss and tensile strength were monitored for the biodegradation tests. A pilot-scale composting trial was conducted in an in-vessel composting system. Results showed that the three biodegradable twine materials (cotton, jute and EcoPLA) could degrade readily in a composting environment within a reasonable time frame. Specifically, at the end of 105 days of composting, 85.3%, 84.8% and 81.1% of weight loss was observed for cotton, jute and EcoPLA, respectively. Furthermore, EcoPLA exhibited a slower decline in tensile strength with time, when compared to jute and cotton. 相似文献
773.
We used a GIS-based approach to examine the influence of road density and physical watershed features (watershed size, wetland
cover, and bedrock type) on water quality in coastal marshes of Georgian Bay, Ontario. We created a GIS that included landscape
information and water-quality data from a 9-year synoptic survey of 105 coastal marshes covering 28 quaternary watersheds.
Multiple regressions and partial correlations were used to discern confounding effects of human-induced (road density) versus
natural physical watershed determinants of water quality. Road density was the dominant factor influencing many water quality
variables, showing positive correlations with specific conductivity (COND), total suspended solids (TSS), and inorganic suspended
solids (ISS) and a negative correlation with overall Water Quality Index scores. Road density also showed positive correlations
with total nitrate nitrogen (TNN) and total phosphorus (TP). By comparison, larger watershed area was the main factor leading
to elevated TP concentrations. The proportion of the watershed occupied by wetlands explained the largest amount of variation
in TNN concentrations (negative correlation) and was also negatively correlated with COND and positively correlated with TSS
and ISS when we controlled for road density. Bedrock type did not have a significant effect in any of the models. Our findings
suggest that road density is currently the overriding factor governing water quality of coastal marshes in Georgian Bay during
the summer low-flow period. We recommend that natural variation in physical watershed characteristics be considered when developing
water quality standards and management practices for freshwater coastal areas. 相似文献
774.
Phase partitioning modeling of ethanol, isopropanol, and methanol with BTEX compounds in water 总被引:2,自引:0,他引:2
Lee KY 《Environmental pollution (Barking, Essex : 1987)》2008,154(2):320-329
This study investigates the equilibrium phase partitioning behavior of ethanol, isopropanol, and methanol in a two-phase liquid-liquid system consisting of water and an individual BTEX (Benzene, Toluene, Ethylbenzene, and Xylenes) compound. A previously developed computer program is enhanced to generate ternary phase diagrams for analysis of each three-component cosolvent-nonaqueous phase liquid (NAPL)-water mixture combination. The required activity coefficients are estimated using the UNIFAC (Universal Quasichemical Functional group Activity Coefficient) model. The UNIFAC-derived ternary phase diagrams generally show good agreement against published experimental data, and similar phase partitioning behavior is observed for every BTEX compound in the presence of the same cosolvent. Furthermore, a set of laboratory experiments is conducted to determine the maximum single-phase water content for every mixture combination considered in this study where the volume composition of the cosolvent and the NAPL components is a blend of 85% alcohol and 15% BTEX compound. Comparison of experimentally-derived maximum single-phase water contents against UNIFAC-derived results shows good agreement for mixtures containing ethanol and methanol, but relatively poor agreement for mixtures containing isopropanol. 相似文献
775.
Sinkkonen A Strömmer R Penttinen OP 《Environmental pollution (Barking, Essex : 1987)》2008,153(3):523-525
Very low toxicant concentrations reduce the frequency of most vital seedlings in dense stands in vitro. 相似文献
776.
长江三角洲地区土壤无机碳库研究 总被引:5,自引:0,他引:5
土壤碳库变化对于全球温室效应、全球碳循环有重大的影响。研究基于最新完成的1〖DK〗∶250 000多目标地球化学调查及相关研究成果,运用地理信息系统软件ARCGIS 92、统计分析软件SPSS130,对长江三角洲地区0~20、0~100、0~180 cm深度土壤无机碳密度及储量做出实测统计。长江三角洲地区0~20、0~100、0~180 cm深度土壤无机碳库储量分别为5099、35647、67726Tg,无机碳密度分别为070、490、930 kg/m2。研究区主要分布土壤为水稻土、潮土,水稻土0~20、0~100、0~180 cm深度土壤无机碳密度分别为057、385、886 kg/m2;潮土无机碳密度分别为117、854 、1537 kg/m2。研究提供最新的土壤无机碳库实测统计信息,弥补中国区域土壤无机碳库清单的空白,完善了中国区域土壤碳库清单,为研究中国区域土壤碳固定潜力、深入全面理解区域碳循环提供了基准数据. 相似文献
777.
778.
I-Fang Mao Chih-Hung Lin Chun-Ji Lin Yi-Ju Chen Fung-Chang Sung Mei-Lien Chen 《Atmospheric environment (Oxford, England : 1994)》2009,43(35):5622-5629
Metropolitan Taipei, which is located in the subtropical area, is characterized by high population and automobile densities. For convenience, most primary schools are located near major roads. This study explores the exposure of acid aerosols for schoolchildren in areas in Taipei with different traffic densities. Acid aerosols were collected by using a honeycomb denuder filter pack sampling system (HDS). Experimental results indicated that the air pollutants were significantly correlated with traffic densities. The ambient air NO2, SO2, HNO3, NO3−, SO42−, and aerosol acidity concentrations were 31.3 ppb, 4.7 ppb, 1.3 ppb, 1.9 μg m−3, 18.5 μg m−3, and 49.5 nmol m−3 in high traffic density areas, and 6.1 ppb, 1.8 ppb, 0.9 ppb, 0.7 μg m−3, 8.8 μg m−3 and 14.7 nmol m−3 in low traffic density areas. The exposure levels of acid aerosols for schoolchildren would be higher than the measurements because the sampling height was 5 m above the ground. The SO2 levels were low (0.13–8.03 ppb) in the metropolitan Taipei. However, the SO42− concentrations were relatively high, and might be attributed to natural emissions of sulfur-rich geothermal sources. The seasonal variations of acid aerosol concentrations were also observed. The high levels of acidic particles in spring time may be attributed to the Asian dust storm and low height of the mixture layer. We conclude that automobile contributed not only the primary pollutants but also the secondary acid aerosols through the photochemical reaction. Schoolchildren were exposed to twice the acid aerosol concentrations in high traffic density areas compared to those in low traffic density areas. The incidence of allergic rhinitis of schoolchildren in the high traffic density areas was the highest in spring time. Accompanied by high temperature variation and high levels of air pollution in spring, the health risk of schoolchildren had been observed. 相似文献
779.
Heavy metal sources identification and sampling uncertainty analysis in a field-scale vegetable soil of Hangzhou, China 总被引:4,自引:0,他引:4
Tao Chen Xingmei Liu Keli Zhao Jianming Xu Jiachun Shi Randy A. Dahlgren 《Environmental pollution (Barking, Essex : 1987)》2009,157(3):1003-1010
At a field-scale (6.7 ha), 100 surface soil samples were collected from a vegetable field to determine total concentrations of Cd, Co, Cu, Hg, Mn, Ni and Zn. To identify possible sources of these metals and characterize their spatial variation, classic statistic and geostatistic techniques were applied. Through correlation and geostatistical analysis, it was found that the primary inputs of Co, Mn and Ni were due to pedogenic sources, whereas the sources of Hg and Cd were mainly due to human activities. Because of their different sources, their variations followed: Hg > Cd ≈ Cu > Zn ≈ Co ≈ Mn ≈ Ni. Based on their relationships with other soil properties, co-kriging was used to minimize sampling density. Sampling numbers for Cd, Cu, Zn, Mn, Co and Ni can be reduced from 100 to 90, 80, 70, 60, 60 and 60, respectively, without losing accuracy relative to ordinary kriging. 相似文献
780.
于2012年4—10月逐月月末采集重庆缙云山4种典型林分(常绿阔叶林、毛竹林、针阔混交林和针叶林)样地中不同深度(0~15、>15~30、>30~60 cm)的土壤样品,测定土壤中w(TN)、w(NH4+-N)和w(NO3--N),分析土壤氮素含量的分布特征,并探讨土壤理化性质对土壤氮素含量的影响. 结果表明:①不同林分土壤中氮素含量的垂直分布规律相一致,均表现为随土壤深度的增加而不断降低,并且w(NH4+-N)>w(NO3--N);②不同林分0~60 cm土壤平均氮密度表现为毛竹林(1.037 kg/m2)>针阔混交林(0.783 kg/m2)≈常绿阔叶林(0.778 kg/m2)>针叶林(0.747 kg/m2);③不同林分土壤中w(TN)的季节性变化规律不明显,而w(NH4+-N)和w(NO3--N)的季节性变化规律相似,均表现为春季<夏季<秋季;④不同林分土壤中w(TN)、w(NH4+-N)和w(NO3--N)与容重、w(SOC)均呈显著线性相关(P<0.05),而且与土壤其他养分含量之间也存在一定的相关性. 相似文献