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排序方式: 共有1301条查询结果,搜索用时 109 毫秒
971.
972.
根据毒理学试验数据讨论四氯乙烯急性吸入毒性的剂量-反应关系.首先总结了有关四氯乙烯急性暴露的毒理学试验数据,并利用分类回归的方法,得出了小鼠、大鼠与人类暴露于四氯乙烯时,暴露时间、暴露浓度与健康后果之间的关系,同时分析了不同受试动物的种间差异.结果表明,健康效应的发生概率随暴露浓度和时间的增大而增大,而当暴露浓度达到某一值的时候,健康后果的发生概率不再随浓度变化而变化,将这一浓度视为饱和浓度;不利效应(AE)对应的饱和浓度要低于剧烈效应(SE),且暴露时间越长,饱和浓度则越低,同时饱和浓度随受试动物的不同而变化,人类的饱和浓度最低,大鼠的则最高. 相似文献
973.
针对工业区急救点布局存在的问题,综合考虑多种影响因素,建立多目标多约束数学模型.将成本、急救时间和急救点数量作为3个优化目标,并根据实际情况构建相应的约束条件.运用NSGA-II(带精英策略的快速非支配排序遗传算法)解决多目标优化问题,最终得到一系列Pareto最优解,其解空间分布均匀,并且具有良好的收敛性和鲁棒性.文章结合某工业区急救点优化问题对算法进行验证,结果与实际情况匹配良好,此研究具有重要的现实意义. 相似文献
974.
华北型煤田岩溶陷落柱导水性研究 总被引:9,自引:2,他引:7
岩溶陷落柱在华北型煤田广泛发育和分布。本文研究了华北型煤田岩溶陷落柱的导水类型、导水条件及突水规律特点。这对华北型煤田煤矿安全生产有重要意义。 相似文献
975.
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
976.
977.
Antibiotic effect of exogenously applied salicylic acid on in vitro soilborne pathogen, Fusarium oxysporum f.sp.niveum 总被引:1,自引:0,他引:1
Wu HS Raza W Fan JQ Sun YG Bao W Liu DY Huang QW Mao ZS Shen QR Miao WG 《Chemosphere》2008,74(1):45-50
Salicylic acid, which is biosynthesized inside plant and is often found and accumulated in soil due to plant debris decaying, is considered as a signaling substance during plant-microbe interactions. It is involved in the cycling of biogeochemistry and related to plant resistance to biotic and abiotic stress. The antibiotic effect of salicylic acid on Fusarium oxysporum f.sp.niveum (FON) was studied to investigate the relationships between the salicylic acid and the fungus in the ecological interaction of plant-microbe. Results showed that the biomass, colony diameter, number of conidium germination and conidium production of FON were decreased by 52.0%, 25.7%, 100% and 100% at concentrations of 800 mg L(-1). However, mycotoxin yield was increased by 233%, pectinase activity raised by 168.0% and cellulase activity increased by 1325% compared to control at higher concentrations. It was concluded that salicylic acid as an allelochemical greatly inhibited FON growth and conidia formation and germination, though stimulated mycotoxin production and activities of hydrolytic enzymes by FON. 相似文献
978.
979.
980.
反相乳液聚合制备阳离子聚丙烯酰胺及其絮凝性能评价 总被引:2,自引:0,他引:2
研究了单体浓度、单体配比、反应温度、引发剂用量等因素对所制备的阳离子聚丙烯酰胺特性粘度、转化率、阳离子度的影响,并对产品的污水絮凝性能进行了评价。较佳的制备条件为:单体浓度为45%,单体配比为7∶3,引发剂用量m(引发剂)/m(单体)为0.5%,引发温度为45℃。用红外光谱对共聚物进行了结构表征,结果表明聚合物中有六元氮杂环的存在,达到预定要求。对共聚物进行了油田污水絮凝性能评价,研究表明单独使用自制阳离子聚丙烯酰胺(CPAM)时浊度的去除率为86.22%,COD去除率为87.95%,与聚合氯化铝复配使用时浊度去除率提高到92.91%,COD去除率提高到92.68%。 相似文献