全文获取类型
收费全文 | 203篇 |
免费 | 16篇 |
国内免费 | 54篇 |
专业分类
安全科学 | 20篇 |
废物处理 | 9篇 |
环保管理 | 21篇 |
综合类 | 109篇 |
基础理论 | 22篇 |
污染及防治 | 60篇 |
评价与监测 | 2篇 |
社会与环境 | 4篇 |
灾害及防治 | 26篇 |
出版年
2023年 | 3篇 |
2022年 | 11篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 12篇 |
2014年 | 15篇 |
2013年 | 22篇 |
2012年 | 15篇 |
2011年 | 13篇 |
2010年 | 18篇 |
2009年 | 14篇 |
2008年 | 17篇 |
2007年 | 11篇 |
2006年 | 17篇 |
2005年 | 4篇 |
2004年 | 7篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 1篇 |
排序方式: 共有273条查询结果,搜索用时 15 毫秒
271.
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
272.
Niedobová Jana Ouředníčková Jana Michalko Radek Skalský Michal 《Environmental Chemistry Letters》2022,20(2):983-990
Environmental Chemistry Letters - Glyphosate is an herbicide which was previously considered safe for non-target organisms. 825.8 million kilograms of glyphosate-based products were used... 相似文献
273.
Vertical distribution and temporal evolution of formaldehyde and glyoxal derived from MAX-DOAS observations: The indicative role of VOC sources 下载免费PDF全文
Zhenfeng Wu Qianqian Hong Cheng Liu Qihou Hu Yanli Zhang Chengzhi Xing Jinping Ou Wei Tan Haoran Liu Xiaoqing Huang 《环境科学学报(英文版)》2022,34(12):92-104
Formaldehyde (HCHO) and glyoxal (CHOCHO) are important oxidization intermediates of most volatile organic compounds (VOCs), but their vertical evolution in urban areas is not well understood. Vertical profiles of HCHO, CHOCHO, and nitrogen dioxide (NO2) were retrieved from ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations in Hefei, China. HCHO and CHOCHO vertical profiles prefer to occur at higher altitudes compared to NO2, which might be caused by the photochemistry-oxidation of longer-lived VOCs at higher altitudes. Monthly means of HCHO concentrations were higher in summer, while enhanced amounts of NO2 were mainly observed in winter. CHOCHO exhibited a hump-like seasonal variation, with higher monthly-averaged values not only occurred in warm months (July-August) but also in cold months (November-December). Peak values mainly occurred during noon for HCHO but emerged in the morning for CHOCHO and NO2, suggesting that HCHO is stronger link to photochemistry than CHOCHO. We further use the glyoxal to formaldehyde ratio (GFR) to investigate the VOC sources at different altitudes. The lowest GFR value is almost found in the altitude from 0.2 to 0.4 km, and then rises rapidly as the altitude increases. The GFR results indicate that the largest contributor of the precursor VOC is biogenic VOCs at lower altitudes, while at higher altitudes is anthropogenic VOCs. Our findings provide a lot more insight into VOC sources at vertical direction, but more verification is recommended to be done in the future. 相似文献