全文获取类型
收费全文 | 2234篇 |
免费 | 135篇 |
国内免费 | 833篇 |
专业分类
安全科学 | 114篇 |
废物处理 | 152篇 |
环保管理 | 182篇 |
综合类 | 1284篇 |
基础理论 | 396篇 |
环境理论 | 2篇 |
污染及防治 | 728篇 |
评价与监测 | 123篇 |
社会与环境 | 91篇 |
灾害及防治 | 130篇 |
出版年
2024年 | 1篇 |
2023年 | 39篇 |
2022年 | 116篇 |
2021年 | 124篇 |
2020年 | 73篇 |
2019年 | 72篇 |
2018年 | 81篇 |
2017年 | 94篇 |
2016年 | 97篇 |
2015年 | 127篇 |
2014年 | 164篇 |
2013年 | 198篇 |
2012年 | 165篇 |
2011年 | 200篇 |
2010年 | 174篇 |
2009年 | 150篇 |
2008年 | 151篇 |
2007年 | 104篇 |
2006年 | 134篇 |
2005年 | 85篇 |
2004年 | 76篇 |
2003年 | 76篇 |
2002年 | 84篇 |
2001年 | 60篇 |
2000年 | 68篇 |
1999年 | 67篇 |
1998年 | 62篇 |
1997年 | 73篇 |
1996年 | 54篇 |
1995年 | 52篇 |
1994年 | 35篇 |
1993年 | 41篇 |
1992年 | 31篇 |
1991年 | 15篇 |
1990年 | 11篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 11篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 6篇 |
1930年 | 1篇 |
排序方式: 共有3202条查询结果,搜索用时 500 毫秒
931.
932.
933.
934.
935.
It was discovered that a green alga strain had the capacity of producing up to 5 g/L high viscosity biopolymers from lactose
under mixotrophic cultivation conditions. The weight-average molecular weight of the polymer was determined to be around 505,000
Da. The ability of this strain to utilize lactose for biopolymer production promises the potential of valuable biopolymer
production from cheese whey, a waste liquor stream of the cheese industry that contains approximately 50 g/L lactose. Using
Plackett-Burnman experiment design and statistical analysis, it was determined that the major parameters affecting biopolymer
production were the concentrations of sodium nitrate and lactose and temperature as well. Further studies on polymer characterization,
production optimization, and applications are under way. 相似文献
936.
Cadmium (Cd) is a highly toxic element in water. Its toxicity has been attributed to oxidative stress mediated by free radicals. Here we investigated the effects of Cd on the histopathology, antioxidant enzymes and lipid peroxidation of crustacean heart. The freshwater crabs Sinopotamon yangtsekiense were exposed to different concentrations of Cd for 1, 3, 5 and 7 d. After exposure, histological abnormalities were discovered, including myocardial edema, vacuolar and vitreous degeneration, and infiltration of inflammatory cells. Additionally, alterations in nuclei, mitochondria, rough endoplasmic reticulum as well as myofibrils were observed. Meanwhile, superoxide dismutase (SOD) activity was significantly increased after Cd exposure. Catalase (CAT) activity was only increased in the group exposed to 14.50 mg L−1 Cd on day 5 and decreased with increasing Cd concentration and exposure time. Glutathione peroxidase (GPx) activity was increased in groups treated with 29.00, 58.00 and 116.00 mg L−1 on days 1 and 3, and decreased thereafter. Besides, malondialdehyde (MDA) levels were significantly increased after 3 d of Cd exposure at all the indicated concentrations. These results showed that acute Cd exposure led to harmful effects on the histology of crab heart, which are most likely linked to Cd-induced oxidative stress. 相似文献
937.
938.
城市环境承载力分析与评估——以湛江市为例 总被引:1,自引:0,他引:1
介绍了环境承载力的涵义以及城市环境承载力的评估方法,以PSR模型研究环境压力所对应的环境状态,以此评估城市环境承载状态,并以湛江市为对象,展开城市环境承载力的现状分析,在此基础上对未来不同发展阶段的环境承载力做情景分析,从减压—改善—优化层次上提出湛江市环境承载力提升的对策建议。 相似文献
939.
J.N. Cape L.J. Sheppard A. Crossley N. van Dijk Y.S. Tang 《Environmental pollution (Barking, Essex : 1987)》2010,158(9):2926-2933
The content of organic N has been shown in many studies to increase during the passage of rain water through forest canopies. The source of this organic N is unknown, but generally assumed to come from canopy processing of wet or dry-deposited inorganic N. There have been very few experimental studies in the field to address the canopy formation or loss of organic N. We report two studies: a Scots pine canopy exposed to ammonia gas, and a Sitka spruce canopy exposed to ammonium and nitrate as wet deposition. In both cases, organic N deposition in throughfall was increased, but only represented a small fraction (<10%) of the additional inorganic N supplied, suggesting a limited capacity for net organic N production, similar in both conifer canopies under Scottish summertime conditions, of less than 1.6 mmol N m−2 mth−1 (equivalent to 3 kg N ha−1 y−1). 相似文献
940.
设计了异波折板水解酸化-A2O一体化反应器,进行生活污水处理的实验研究。10个月的实验结果表明,系统的最佳水力停留时间(HRT)为8 h时,最适COD进水浓度为240-100mg/L,最佳混合液回流比(r)-污泥回流比(R)为250%-100%。控制反应器于以上运行参数下,25±2℃所对应的COD、TN和TP去除率分别为96.84%、67.55%和81.92%。当温度降至7℃时,其COD、TP和TN分别降至86.35%、50.25%和65.68%。基于实验分析结果,阐明了一体化反应器高效性的机理在于异波折板水解酸化段具有高效传质特性和A2O段具有复合式活性污泥-接触氧化好氧池的特点。 相似文献