全文获取类型
收费全文 | 1328篇 |
免费 | 190篇 |
国内免费 | 341篇 |
专业分类
安全科学 | 209篇 |
废物处理 | 40篇 |
环保管理 | 100篇 |
综合类 | 862篇 |
基础理论 | 186篇 |
污染及防治 | 215篇 |
评价与监测 | 78篇 |
社会与环境 | 88篇 |
灾害及防治 | 81篇 |
出版年
2024年 | 5篇 |
2023年 | 34篇 |
2022年 | 106篇 |
2021年 | 95篇 |
2020年 | 123篇 |
2019年 | 87篇 |
2018年 | 77篇 |
2017年 | 94篇 |
2016年 | 72篇 |
2015年 | 87篇 |
2014年 | 103篇 |
2013年 | 129篇 |
2012年 | 109篇 |
2011年 | 121篇 |
2010年 | 109篇 |
2009年 | 88篇 |
2008年 | 61篇 |
2007年 | 62篇 |
2006年 | 50篇 |
2005年 | 52篇 |
2004年 | 36篇 |
2003年 | 33篇 |
2002年 | 22篇 |
2001年 | 19篇 |
2000年 | 16篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1966年 | 1篇 |
1965年 | 3篇 |
1964年 | 2篇 |
1963年 | 3篇 |
1962年 | 1篇 |
1961年 | 3篇 |
1960年 | 4篇 |
1959年 | 2篇 |
1958年 | 1篇 |
1957年 | 4篇 |
1955年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1859条查询结果,搜索用时 517 毫秒
981.
982.
983.
从城市尺度空气质量模型和平流扩散理论出发,通过对气象要素归类,利用空气质量与各类气象条件对应排放源强表征量的关联,建立了气象要素变化对城市空气质量影响的评估方法.该方法考虑了包括风(风速和风向)、云量、太阳辐射强度、大气稳定度、混合层高度等基本气象要素,能定量有效评估长期气象要素变化对空气质量的改善幅度.该方法在河南省鹤壁市的应用表明,相对2020年,2021年PM2.5浓度下降7.2μg/m3,气象要素变化和人为减排分别下降0.4和6.8μg/m3,占改善浓度的5.6%和94.4%,人努力起到主导作用;从季度来看,大气污染防治工作使夏、秋、冬季PM2.5浓度均有所降低,其中冬季下降27.8μg/m3,减排措施贡献16.8μg/m3,人努力效果尤为显著. 相似文献
984.
Heavy metal concentrations in urban soils are likely to increase over time because of continuous urbanization and heavy metal emissions. To estimate the accumulation rates of heavy metals in urban soils, we collected soil samples from residential areas with different building ages in the metropolitan cities of Shanghai, Shenzhen, and Beijing, China. Heavy metal concentrations in the soils varied among the cities and were primarily affected by soil parent material and the intensity of anthropogen... 相似文献
985.
基于人工神经网络的空气质量预测模型优于传统的逐步回归模型,但由于性能差异不明显而较少在空气质量预报中应用. 设计了将遗传算法和神经网络算法相结合的基于GA-ANN的空气质量预测模型,并利用天津市2003—2007年气象和污染物监测资料对该模型进行验证. 对2007年全年的ρ(SO2),ρ(NO2)和ρ(PM10)进行预测,预测值与实测值的相关系数分别为0.899 6,0.828 3和0.600 0. 与一般的人工神经网络预测模型相比较,GA-ANN模型将空气质量等级预报的准确率从77.57%提高到79.67%. GA-ANN模型可结合其他方法进行日常空气质量预报. 相似文献
986.
987.
白腐菌去除氯代酚动力学研究 总被引:3,自引:0,他引:3
使用Volterra模型描述 2 ,4-二氯酚体系中白腐菌生长动力学 ,建立氯代酚去除部分偶联型动力学方程 ,描述了生物降解体系中降解菌与目标化合物的反应历程 ,利用动力学方法初步探讨批次反应时生物吸附在氯代酚去除过程中的作用 相似文献
988.
Kai Lindström 《Behavioral ecology and sociobiology》1998,42(2):101-106
This study tested experimentally whether clutch size and the cost of care affect filial cannibalism in the sand goby, Pomatoschistus minutus. Evolutionary models of filial cannibalism suggest that egg eating has evolved as a way for the male parent to prolong his
breeding season. These models assume that eggs function as an alternative energy source for the constrained parent. I manipulated
clutch size by allowing males to mate with either one or two females, representing a small and a large clutch, respectively.
The addition of a small male shore crab, a common egg predator, increased the cost of care. I quantified fat reserves as a
measure of the condition of guarding males. Males who did not build nests had lower fat reserves than males who built nests,
suggesting that males with low energy reserves do not start breeding. Males with small clutches lost their nest to the crab
more often than males with large clutches. Neither filial cannibalism nor the amount of eggs eaten were affected by the treatments.
Males who consumed eggs had a higher fat percentage than males who did not eat eggs. The result that males with small clutches
lost their nests to the crabs supports the idea that eggs are defended only if the benefit from continued care will outweigh
the cost and that males therefore are sensitive to the trade-off between present and future reproductive success.
Received: 15 May 1997 / Accepted after revision: 15 November 1997 相似文献
989.
Biodegradation of triclosan and formation of methyl-triclosan in activated sludge under aerobic conditions 总被引:1,自引:0,他引:1
Triclosan is an antimicrobial agent which is widely used in household and personal care products. Widespread use of this compound has led to the elevated concentrations of triclosan in wastewater, wastewater treatment plants (WWTPs) and receiving waters. Removal of triclosan and formation of triclosan-methyl was investigated in activated sludge from a standard activated sludge WWTP equipped with enhanced biological phosphorus removal. The removal was found to occur mainly under aerobic conditions while under anoxic (nitrate reducing) and anaerobic conditions rather low removal rates were determined. In a laboratory-scale activated sludge reactor 75% of the triclosan was removed under aerobic conditions within 150 h, while no removal was observed under anaerobic or anoxic conditions. One percent of the triclosan was converted to triclosan-methyl under aerobic conditions, less under anoxic (nitrate reducing) and none under anaerobic conditions. 相似文献
990.
The feasibility of partially substituting raw materials with municipal solid waste incineration (MSWI) fly ash in sulfoaluminate cement (SAC) clinker production was investigated by X-ray diffraction (XRD), compressive strength and free expansion ratio testing. Three different leaching tests were used to assess the environmental impact of the produced material. Experimental results show that the replacement of MSWI fly ash could be taken up to 30% in the raw mixes. The good quality SAC clinkers are obtained by controlling the compositional parameters at alkalinity modulus (C(m)) around 1.05, alumina-sulfur ratio (P) around 2.5, alumina-silica ratio (N) around 2.0~3.0 and firing the raw mixes at 1250 °C for 2h. The compressive strengths of SAC are high in early age while that develop slowly in later age. Results also show that the expansive properties of SAC are strongly depended on the gypsum content. Leaching studies of toxic elements in the hydrated SAC-based system reveal that all the investigated elements are well bounded in the clinker minerals or immobilized by the hydration products. Although some limited positive results indicate that the SAC prepared from MSWI fly ash would present no immediate thread to the environment, the long-term toxicity leaching behavior needs to be further studied. 相似文献