全文获取类型
收费全文 | 5863篇 |
免费 | 601篇 |
国内免费 | 2879篇 |
专业分类
安全科学 | 322篇 |
废物处理 | 301篇 |
环保管理 | 1241篇 |
综合类 | 4730篇 |
基础理论 | 1167篇 |
污染及防治 | 993篇 |
评价与监测 | 422篇 |
社会与环境 | 126篇 |
灾害及防治 | 41篇 |
出版年
2024年 | 26篇 |
2023年 | 141篇 |
2022年 | 262篇 |
2021年 | 286篇 |
2020年 | 296篇 |
2019年 | 282篇 |
2018年 | 281篇 |
2017年 | 253篇 |
2016年 | 347篇 |
2015年 | 302篇 |
2014年 | 331篇 |
2013年 | 641篇 |
2012年 | 457篇 |
2011年 | 498篇 |
2010年 | 366篇 |
2009年 | 350篇 |
2008年 | 347篇 |
2007年 | 364篇 |
2006年 | 345篇 |
2005年 | 263篇 |
2004年 | 236篇 |
2003年 | 329篇 |
2002年 | 336篇 |
2001年 | 296篇 |
2000年 | 290篇 |
1999年 | 242篇 |
1998年 | 183篇 |
1997年 | 157篇 |
1996年 | 281篇 |
1995年 | 125篇 |
1994年 | 77篇 |
1993年 | 58篇 |
1992年 | 33篇 |
1991年 | 40篇 |
1990年 | 11篇 |
1989年 | 19篇 |
1988年 | 14篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 24篇 |
1984年 | 42篇 |
1983年 | 39篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1972年 | 1篇 |
1971年 | 14篇 |
1967年 | 1篇 |
排序方式: 共有9343条查询结果,搜索用时 210 毫秒
571.
本文对西昌市大气污染现状进行调查分析,揭示了大气环境污染的特征及其变化规律,从宏观上提出了保护大气环境的对策。 相似文献
572.
John F Elder 《Journal of the American Water Resources Association》1994,30(2):251-259
ABSTRACT: A study of concentrations and distribution of major and trace elements in surficial bottom sediments of Little Rock Lake in northern Wisconsin included examination of spatial variation and grain-size effects. No significant differences with respect to metal distribution in sediments were observed between the two basins of the lake, despite the experimental acidification of one of the basins from pH 6.1 to 4.6. The concentrations of most elements in the lake sediments were generally similar to soil concentrations in the area and were well below sediment quality criteria. Two exceptions were lead and zinc, whose concentrations in July 1990 exceeded the criteria of 50 μg/g and 100 μg/g, respectively, in both littoral and pelagic sediments. Concentrations of some elements, particularly Cu, Pb, and Zn, increased along transects from nearshore to midlake, following a similar gradient of sedimentary organic carbon. In contrast, Mn, Fe, and alkali/alkaline-earth elements were at maximum concentrations in nearshore sediments. These elements are less likely to partition to organic particles, and their distribution is more dependent on mineralogical composition, grain size, and other factors. Element concentrations varied among different sediment grain-size fractions, although a simple inverse relation to grain size was not observed. Fe, Mn, Pb, and Zn were more concentrated in a grain-size range 20–60 tm than in either the very fine or the coarse fractions, possibly because of the aggregation of smaller particles cemented together by organic and Fe/Mn hydrous-oxide coatings. 相似文献
573.
James P. Hughes Steven P. Millard 《Journal of the American Water Resources Association》1988,24(3):521-531
ABSTRACT: A common problem arises in testing for trends in water quality when observations are reported as “less than detection limit.” If a single detection limit is used for the entire study, existing non-parametric statistical methods, modified for ties, are applicable. If, however, the detection limit varies during the course of the study, resulting in multiple detection limits, then the commonly used trend detection methods are not appropriate. A statistic similar to Kendall's tau, but based on expected ranks, is proposed. Monte Carlo simulations show that the normal approximation to the distribution of this statistic is quite good, even for small samples and a large proportion of censored observations. The statistic is also shown to have greater power than the ad-hoc method of treating all observations less than the target censored observation as tied. 相似文献
574.
G. William Page 《Journal of the American Water Resources Association》1988,24(4):847-854
ABSTRACT: Contamination of ground water supplies with volatile organic compounds is a new and significant problem. Municipalities and their community water systems are often the first to discover ground water contamination because of the monitoring programs they are required to carry out. When contamination exceeds standards, some action is required. The responses of Wisconsin municipalities to volatile organic compounds that exceed standards in their ground water sources is described. Actions to protect human health are prompt, but the survey results indicate plumes of contaminated ground water are usually not treated. They may continue to migrate and contaminate other private and public wells. 相似文献
575.
Robert Leconte Rangesan Narayanan Trevor C. Hughes 《Journal of the American Water Resources Association》1988,24(2):247-253
ABSTRACT: A general methodology to study the economics of dual water systems (defined here as a separate distribution system for untreated low quality local surface Water for outdoor municipal water supply) is summarized and the application of the method to a rapidly growing city is presented. In the first step, a cost-benefit criterion for evaluating dual systems is developed. The criterion is then extended to a dynamic case where the population to be served increases with time and where the dual system is allowed to expand. The optimal investment time to introduce the dual water supply project is obtained by maximizing social welfare. The model is applied to the city of West Jordan, Utah, where a dual system is currently being proposed. Model results indicate that for the city as a whole dual supply is not economically feasible. However, when the model is applied to a part of the city, it is found feasible and the optimal time to initiate the project would be in the year 1989. 相似文献
577.
甲胺磷农药废水生化处理高效菌选育的研究 总被引:23,自引:1,他引:23
从用甲胺磷农药废水长期驯化的活污泥中,筛选得到两株降解甲胺磷农药废水中有机磷的高效菌,经鉴定一株为蜡样芽孢杆菌(Bacilluscereus)。另一株为嗜中温假单胞菌(Pseudomonasmesophilica)。确定了上述高效菌的最适生长条件和降解有机磷的能力,混合高效菌的有机磷去除率达99.7%。 相似文献
578.
579.
本文提出一种利用静电场的印染废水处理方法,印染废水中的污染颗粒在电场的作用下,朝一定的方向迁移,从而发生“强制电中和”作用,这种电中和作用的场能消耗极小,而被中和的污染物颗粒由于凝聚作用,则会不断长大而易于通令过滤去除,这一处理工艺在经“自数”预处理之后,可继续使COD和色度的去除百分数分别达60%和63%以上。 相似文献
580.
ABSTRACT: The Hallett Quarry gravel pit lakes are an active sand and gravel extraction operation located 0.4 km north of the City of Ames, Iowa. During periods of drought, these lakes serve as a supplemental water supply for Ames. A modified version of the Vollenweider input-output model was used to predict future water quality under various watershed land use, drainage, and lake configurations. The dominant factor controlling the future water quality of the lakes was found to be the nutrient input. It is recommended that a management plan to protect the future water quality should be oriented towards reducing the sources of phosphorus to the lakes. 相似文献