全文获取类型
收费全文 | 1577篇 |
免费 | 200篇 |
国内免费 | 388篇 |
专业分类
安全科学 | 376篇 |
废物处理 | 52篇 |
环保管理 | 300篇 |
综合类 | 816篇 |
基础理论 | 183篇 |
污染及防治 | 174篇 |
评价与监测 | 93篇 |
社会与环境 | 77篇 |
灾害及防治 | 94篇 |
出版年
2024年 | 7篇 |
2023年 | 21篇 |
2022年 | 51篇 |
2021年 | 71篇 |
2020年 | 77篇 |
2019年 | 73篇 |
2018年 | 51篇 |
2017年 | 73篇 |
2016年 | 94篇 |
2015年 | 84篇 |
2014年 | 106篇 |
2013年 | 130篇 |
2012年 | 145篇 |
2011年 | 151篇 |
2010年 | 101篇 |
2009年 | 94篇 |
2008年 | 89篇 |
2007年 | 146篇 |
2006年 | 109篇 |
2005年 | 62篇 |
2004年 | 57篇 |
2003年 | 51篇 |
2002年 | 37篇 |
2001年 | 34篇 |
2000年 | 44篇 |
1999年 | 29篇 |
1998年 | 23篇 |
1997年 | 27篇 |
1996年 | 19篇 |
1995年 | 10篇 |
1994年 | 16篇 |
1993年 | 13篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1985年 | 13篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有2165条查询结果,搜索用时 924 毫秒
281.
选用SO2、NO2、PM10作为评价因子,采用时间序列的方法对西安市2009年-2014年大气环境质量进行分析评价.结果表明:2009年-2012年西安市空气质量达到了国家二级标准,SO2和NO2的年平均含量下降,2013年都略有上升,但总体上呈下降趋势,而颗粒物的年平均含量呈上升趋势且为影响该市空气质量的主要污染物,主要污染时间为1季度和4季度;利用GM(1,1)模型,预测2015年空气质量变化趋势,提出2015年应该采取措施降低颗粒物的含量,提高本市空气质量. 相似文献
282.
Millions of tons of waste activated sludge (WAS) produced from biological wastewater treatment processes cause severe adverse environmental consequences. A better understanding of WAS composition is thus very critical for sustainable sludge management. In this work, the occurrence and distribution of several fundamental sludge constituents were explored in WAS samples from nine full-scale wastewater treatment plants (WWTPs) of Beijing, China. Among all the components investigated, active heterotrophic biomass was dominant in the samples (up to 9478 mg/L), followed by endogenous residues (6736 mg/L), extracellular polymeric substances (2088 mg/L), and intracellular storage products (464 mg/L) among others. Moreover, significant differences (p < 0.05) were observed in composition profiles of sludge samples among the studied WWTPs. To identify the potential parameters affecting the variable fractions of sludge components, wastewater source as well as design and operational parameters of WWTPs were studied using statistical methods. The findings indicated that the component fraction of sewage sludge depends more on wastewater treatment alternatives than on wastewater characteristics among other parameters. A principal component analysis was conducted, which further indicated that there was a greater proportion of residual inert biomass in the sludge produced by the combined system of the conventional anaerobic/anoxic/oxic process and a membrane bioreactor. Additionally, a much longer solids retention time was also found to influence the sludge composition and induce an increase in both endogenous inert residues and extracellular polymeric substances in the sludge. 相似文献
283.
As an important intermediate product, short-chain fatty acids(SCFAs) can be generated after hydrolysis and acidification from waste activated sludge, and then can be transformed to methane during anaerobic digestion process. In order to obtain more SCFA and methane,most studies in literatures were centered on enhancing the hydrolysis of sludge anaerobic digestion which was proved as un-efficient. Though the alkaline pretreatment in our previous study increased both the hydrolysis and acidification processes, it had a vast chemical cost which was considered uneconomical. In this paper, a low energy consumption pretreatment method, i.e. enhanced the whole three stages of the anaerobic fermentation processes at the same time, was reported, by which hydrolysis and acidification were both enhanced, and the SCFA and methane generation can be significantly improved with a small quantity of chemical input. Firstly, the effect of different pretreated temperatures and pretreatment time on sludge hydrolyzation was compared. It was found that sludge pretreated at 100°C for 60 min can achieve the maximal hydrolyzation. Further, effects of different initial p Hs on acidification of the thermal pretreated sludge were investigated and the highest SCFA was observed at initial p H 9.0with fermentation time of 6 d, the production of which was 348.63 mg COD/g VSS(6.8 times higher than the blank test) and the acetic acid was dominant acid. Then, the mechanisms for this new pretreatment significantly improving SCFA production were discussed. Finally,the effect of this low energy consumption pretreatment on methane generation was investigated. 相似文献
284.
285.
固体发动机装药热安全性数值分析 总被引:3,自引:1,他引:2
目的研究固体火箭发动机遭受火烤时的安全性。方法建立发动机有限元模型,计算推进剂在慢速烤燃和快速烤燃工况下的温度分布和爆炸延迟时间。结果推进剂慢烤47 h后达到临界温度,其值为352℃;快烤推进剂加热697 s后达到临界温度,临界温度为355℃。结论推进剂在快速烤燃模式下的热扩散速率大于慢速烤燃工况下,但是温度梯度则相反。两种工况下推进剂达到临界温度后开始反应的位置不同,推进剂厚度决定了其储热能力。 相似文献
286.
乌海市作为资源型城市,加之基础设施不完善,在经济快速发展的同时,产生了工业企业固体废物乱排、乱放、不按规定要求处置的现象,本文针对乌海市工业固废存在的突出问题提出了几点整治的建议。 相似文献
287.
288.
疏水性超高交联吸附树脂对氯代烃蒸气的固定床吸附特性研究 总被引:1,自引:1,他引:0
采用固定床吸附法研究了三氯乙烯(TCE)、 1,2-二氯乙烷(DCE)和三氯甲烷(TCM)共3种氯代烃类蒸气在疏水性超高交联吸附树脂LC-1上的动态吸附行为.结果表明, TCE、 DCE和TCM蒸气的初始浓度、 气体流速和吸附温度均会影响动态吸附过程,随着初始浓度、 气体流速和吸附温度的增大,穿透时间变短,传质区长度增大,其中气体流速的影响最大;采用半经验数学模型Yoon-Nelson模型对吸附穿透实验数据进行拟合,拟合相关性系数R2≥0.994. 相似文献
289.
290.
影响三沟式氧化沟脱氮效果的2个重要参数 总被引:2,自引:0,他引:2
运行周期中反硝化运行和硝化运行的时间比tDN/tN是平衡处理系统反硝化,硝化能力的重要参数,实验室条件下分别比较了tDN/tN为0.27,0.40,0.47,0.75和1.0的5种不同组合的运行效果。结果表明,当tDN/tN为0.40时,即硝化能力略大于反硝化潜能时,脱氮效果最好。 相似文献