全文获取类型
收费全文 | 694篇 |
免费 | 105篇 |
国内免费 | 643篇 |
专业分类
安全科学 | 48篇 |
废物处理 | 124篇 |
环保管理 | 50篇 |
综合类 | 758篇 |
基础理论 | 163篇 |
污染及防治 | 272篇 |
评价与监测 | 19篇 |
社会与环境 | 6篇 |
灾害及防治 | 2篇 |
出版年
2024年 | 4篇 |
2023年 | 30篇 |
2022年 | 51篇 |
2021年 | 59篇 |
2020年 | 52篇 |
2019年 | 77篇 |
2018年 | 82篇 |
2017年 | 73篇 |
2016年 | 82篇 |
2015年 | 89篇 |
2014年 | 86篇 |
2013年 | 84篇 |
2012年 | 84篇 |
2011年 | 80篇 |
2010年 | 41篇 |
2009年 | 71篇 |
2008年 | 32篇 |
2007年 | 64篇 |
2006年 | 39篇 |
2005年 | 43篇 |
2004年 | 26篇 |
2003年 | 22篇 |
2002年 | 28篇 |
2001年 | 33篇 |
2000年 | 19篇 |
1999年 | 26篇 |
1998年 | 10篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有1442条查询结果,搜索用时 15 毫秒
931.
Methane emissions of differently fed dairy cows and corresponding methane and nitrogen emissions from their manure during storage 总被引:1,自引:0,他引:1
Külling DR Dohme F Menz H Sutter F Lischer P Kreuzer M 《Environmental monitoring and assessment》2002,79(2):129-150
This study investigated the effects of supplementing 40 g lauric acid (C12) kg-1 dry matter (DM) in feed on methane emissions from early-lactating dairy cows and the associated effects on methane, nitrous oxide and ammonia release from the manure during storage. Stearic acid (C18), a fatty acid without assumed methane-suppressing potential in the digestive tract of ruminants, was added at 40 g kg-1 DM to a control diet. The complete feed consisted of forage and concentrate in a ratio of 1.5:1 (DM basis). The manure was stored for 14 weeks either as complete slurry or, separately, as urine-rich slurry and farmyard manure representing two common storage systems. Methane release of the cows, as measured in respiratory chambers, was lower with C12 by about 20%, but this was mostly resulting from a reduced feed intake and, partly, from a lower rate of fibre digestion. As milk yield declined less than feed intake, methane emission per kg of milk was significantly lower with C12 (11.4 g) than with C18 (14.0 g). Faeces of C12-fed cows had a higher proportion of undigested fibre and accordingly methane release from their manure was higher compared with the manure obtained from the C18-fed cows. Overall, manure-derived methane accounted for8.2% and 15.4% of total methane after 7 and 14 weeks of storage, respectively. The evolution of methane widely differed between manure types and dietary treatments, with a retarded onset of release in complete slurry particularly in the C12 treatment. Emissions of nitrous oxide were lower in the manures from the C12 treatment. This partially compensated for the higher methane release from the C12 manure with respect to the greenhouse gas potential. The total greenhouse gas potential (cow and manure together) accounted for 8.7 and 10.5 kg equivalents of CO2 cow-1 d-1with C12 and C18, respectively. At unaffected urine-N proportion ammonia and total nitrogen losses from stored manure were lower with C12 than with C18 corresponding to the differences in feed and nitrogen intake. The present results suggest that manure storage significantly contributes to total methane emission from dairy husbandry, and that the identification of effective dietary mitigation strategies has to consider both the digestive tract of the animals and the corresponding manure. 相似文献
932.
针对轧钢废水中含有磁性铁氧化物 ,为使废水处理回用 ,研制了集预磁、磁吸、固液分离、自动清渣于一体的新型内构式稀土磁盘水处理器 ,并阐明了其应用的方法 相似文献
933.
讨论了氧化铝对腐殖酸的吸附性能,以及吸附操作条件的影响。结果表明,500℃以上的热处理,可有效地提高氧化铝水合物对腐殖酸的吸附效果;中性偏酸的溶液和吸附质溶液中铝离子的存在,可明显提高腐殖酸的去除率;氧化铝对腐殖酸有较快的去除速度,在22.3mgTOC/l的浓度范围内,腐殖酸去除量与其浓度呈线性相关。 相似文献
934.
选取CH4、O2、CO2、Ar、NO、NH3,等气体,作为混合气和煤粉一起送入一维沉降炉内,以模拟O2/CO2气氛下煤中燃料氮、循环NO以及二者的相互作用对NO排放的影响,结果显示,在还原性气氛下NH3、HCN、CH4、CO与循环NO间的反应是NO排放下降的主要因素,且煤焦与NO的异相反应、吸附反应对NO的降解效果要明显高于氧化性气氛,同时,CO2体积分数的增加使得燃料中氮的氧化率升高,循环NO的降解率下降;氧化性气氛下随CO2体积分数的增加,燃料中氮的氧化率也增加,但循环NO的降解率升高.当CO2体积分数不变时,其对NO降解的作用随循环NO体积分数的增加愈加明显,在循环NO也不变且CO2体积分数较低时,随过量空气系数的增加,循环NO的降解率下降,而CO2体积分数较高时则出现相反情况。 相似文献
935.
根据硫酸钠熔炼法处理废合金所得钴渣组成特点 ,通过氧化焙烧、酸分解、水解除杂、沉钴和煅烧等工序制取氧化钴。焙烧最佳工艺条件为 :NaNO3用量为钴渣量的 0 8倍 ,焙烧温度 75 0℃ ,时间 2 5h。盐酸分解、喷淋水解除铁、草酸铵沉钴和煅烧阶段钴的回收率 ( % )分别为 97 5、96 6、99 5和 99 0 ,使Co、Ta的回收率分别达到 92 78%和 85 %。 相似文献
936.
937.
938.
LI Zhe SHEN Lin-tao HUANG Wei~* XIE Ke-chang Key Laboratory of Coal Science Technology Ministry of Education Shanxi Province Taiyuan University of Technology Taiyuan China. 《环境科学学报(英文版)》2007,19(12)
The catalyst of Fe-Mo/ZSM-5 has been found to be more active than Fe-ZSM-5 and Mo/ZSM-5 separately for selective catalytic reduction (SCR) of nitric oxide (NO) with NH_3.The kinetics of the SCR reaction in the presence of O_2 was studied in this work.The results showed that the observed reaction orders were 0.74-0.99,0.01-0.13,and 0 for NO,O_2 and NH_3 at 350-450℃,respectively. And the apparent activation energy of the SCR was 65 kJ/mol on the Fe-Mo/ZSM-5 catalyst.The SCR mechanism was also deduced. Adsorbed NO species can react directly with adsorbed ammonia species on the active sites to form N_2 and H_2O.Gaseous O_2 might serve as a reoxidizing agent for the active sites that have undergone reduction in the SCR process.It is also important to note that a certain amount of NO was decomposed directly over the Fe-Mo/ZSM-5 catalyst in the absence of NH_3. 相似文献
939.
湿法吸收法处理氮氧化物废气 总被引:6,自引:0,他引:6
介绍了湿法吸收氮氧化物工业废气的方法,并对吸收液和吸收塔进行了深入的探讨和研究。 相似文献
940.
Kazuhiko Sakamoto Katsunori Kimijima Tadao Suzuki Masahiro Uchiyama Yoshikazu Hashimoto Hisao ohta Yasuaki maeda Nobutoshi Horiuchi Shin Suzuki 《环境科学学报(英文版)》1990,(1)
The conversion rates of SO2 to SO42- and NO2 to HNO3+NO3- are estimated from the field-data obtained in Beijing in summer, 1988. The results show that the conversion rate of NO2 is about four times as much as that of SO2; The conversion rates have a diurnal variation in a day. On the average, the rate of SO2 is estimated to be 4.7% h-1 during the daytime and 3.4% h-1 during the nighttime. Similarly, the rate of NO2 is estimated to be 17.2% h-1 and 12% h-1 respectively. 相似文献