全文获取类型
收费全文 | 69篇 |
免费 | 7篇 |
国内免费 | 31篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 7篇 |
2014年 | 6篇 |
2013年 | 4篇 |
2012年 | 7篇 |
2011年 | 8篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 10篇 |
2007年 | 6篇 |
2006年 | 1篇 |
2005年 | 3篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1997年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有107条查询结果,搜索用时 62 毫秒
71.
Rates, controls and potential adverse effects of nitrate removal in a denitrification bed 总被引:2,自引:0,他引:2
Sören Warneke Louis A. SchipperDenise A. Bruesewitz Ian McDonaldStewart Cameron 《Ecological Engineering》2011,37(3):511-522
Denitrification beds are a simple approach for removing nitrate (NO3−) from a range of point sources prior to discharge into receiving waters. These beds are large containers filled with woodchips that act as an energy source for microorganisms to convert NO3− to nitrogen (N) gases (N2O, N2) through denitrification. This study investigated the biological mechanism of NO3− removal, its controlling factors and its adverse effects in a large denitrification bed (176 m × 5 m × 1.5 m) receiving effluent with a high NO3− concentration (>100 g N m−3) from a hydroponic glasshouse (Karaka, Auckland, New Zealand). Samples of woodchips and water were collected from 12 sites along the bed every two months for one year, along with measurements of gas fluxes from the bed surface. Denitrifying enzyme activity (DEA), factors limiting denitrification (availability of carbon, dissolved organic carbon (DOC), dissolved oxygen (DO), temperature, pH, and concentrations of NO3−, nitrite (NO2−) and sulfide (S2−)), greenhouse gas (GHG) production - as nitrous oxide (N2O), methane (CH4), carbon dioxide (CO2) - and carbon (C) loss were determined. NO3−-N concentration declined along the bed with total NO3−-N removal rates of 10.1 kg N d−1 for the whole bed or 7.6 g N m−3 d−1. NO3−-N removal rates increased with temperature (Q10 = 2.0). In laboratory incubations, denitrification was always limited by C availability rather than by NO3−. DO levels were above 0.5 mg L−1 at the inlet but did not limit NO3−-N removal. pH increased steadily from about 6 to 7 along the length of the bed. Dissolved inorganic carbon (C-CO2) increased in average about 27.8 mg L−1, whereas DOC decreased slightly by about 0.2 mg L−1 along the length of the bed. The bed surface emitted on average 78.58 μg m−2 min−1 N2O-N (reflecting 1% of the removed NO3−-N), 0.238 μg m−2 min−1 CH4 and 12.6 mg m−2 min−1 CO2. Dissolved N2O-N increased along the length of the bed and the bed released on average 362 g dissolved N2O-N per day coupled with N2O emission at the surface about 4.3% of the removed NO3−-N as N2O. Mechanisms to reduce the production of this GHG need to be investigated if denitrification beds are commonly used. Dissolved CH4 concentrations showed no trends along the length of the bed, ranging from 5.28 μg L−1 to 34.24 μg L−1. Sulfate (SO42−) concentrations declined along the length of the bed on three of six samplings; however, declines in SO42− did not appear to be due to SO42− reduction because S2− concentrations were generally undetectable. Ammonium (NH4+) (range: <0.0007 mg L−1 to 2.12 mg L−1) and NO2− concentrations (range: 0.0018 mg L−1 to 0.95 mg L−1) were always very low suggesting that anammox was an unlikely mechanism for NO3− removal in the bed. C longevity was calculated from surface emission rates of CO2 and release of dissolved carbon (DC) and suggested that there would be ample C available to support denitrification for up to 39 years.This study showed that denitrification beds can be an efficient tool for reducing high NO3− concentrations in effluents but did produce some GHGs. Over the course of a year NO3− removal rates were always limited by C and temperature and not by NO3− or DO concentration. 相似文献
72.
空心莲子草叶甲Agasicles hygrophila是入侵杂草空心莲子草Alternan thera philoxeroide的重要天敌,冬春季低温冰冻是影响其安全越冬的关键胁迫因子。为了探明采取保护措施是否能提高越冬后的种群基数问题,在低温冰冻天气来临前,用塑料膜覆盖网室构建空心莲子草与空心莲子草叶甲保护生境(PH),分低温期(2009年1月21日至4月9日)、升温期(4月15日至5月1日)与自然生境(NH)中叶甲成虫初现期(从6月1日至29日)3个阶段,调查比较PH与NH两类生境中空心莲子草叶甲种群数量、结构、空间生态位分布特征及控害效能。结果表明:在保护生境中,低温期空心莲子草叶甲不休眠,且能安全越冬,当晴天温度较高时,成虫主要在直立茎或嫩枝上活动取食、补充营养,而在阴雨低温天气则停留在匍匐草层或土壤表层、缝隙中,少活动。随着气温回升,成虫转移到直立茎生态位上活动取食,并于4月上旬开始产卵繁殖,种群数量迅速增加,对空心莲子草的地上部分有较好的控制效果。在自然生境中,直到6月初才见少量成虫活动,此时草生长茂密,较低的空心莲子草叶甲种群难以发挥生防因子的作用。比较两种生境中6月1日与6月15日的控草效果显示,空心莲子草株高增长率分别为:PH-13.91%,NH-2.94%,NH中空心莲子草株高极显著高于PH,且单株生物量的控制率为PH(47.56%)极显著高于NH(4.89%)。在6月15日与29日的调查表明,单株叶片控制效果PH极显著优于NH,PH中的空心莲子草茎上均无叶,叶片或被取食殆尽、或被害后干枯脱落。茎被害率、茎蛀孔数与蛀茎率均为PH极显著高于NH。结果说明覆膜保护能显著提高叶甲越冬种群基数,使其提前进入繁殖期,从而能更有效地控制生境中的空心莲子草。 相似文献
73.
74.
烟草内生菌对烟草根结线虫病的防治效果 总被引:3,自引:0,他引:3
从烟草中筛选到几株内生菌进行防治根结线虫的盆栽试验,以研究其防治效果.结果表明,内生细菌发酵液的防治效果优于内生细菌菌体,内生放线菌则相反.内生菌普遍对植物具有促生作用,但内生菌菌体的促生效果优于内生菌的发酵液.H3号内生细菌对根结线虫防治效果最好,病情指数为4.16,防效为91.68%,明显优于对照,优于阿维菌素处理,H3号内生细菌处理的烟草形态指标明显优于阿维菌素处理.Abstract: Several tobacco endophyte strains were screened out, and their controlling effect against tobacco root-knot nematodes was studied with pot experiment. The fermentation broth of endophytic bacteria was more effective than the bacterial thallus, while that of endophytic actino-mycetes was less effective than the actinomycete fermentation broth. All test endophytes promoted tobacco growth, and the promotion effect of their thalli was better than that of their fermentation broths. Endophytic bacterial strain H3 was the best in controlling tobacco root-knot nematode dis-ease, with 91.68% controlling effect and a disease index of 4. 16, much better than the treat-ments CK and avermectin. Moreover, the morphological feature of tobacco plant treated with H3 was better than that treated with avermectin. 相似文献
75.
76.
77.
78.
79.
鲜切花保鲜相关调控基因研究进展 总被引:9,自引:0,他引:9
对切花保鲜相关调控基因:ACC氧化酶基因(CAO),ACC合成酶基因(ACS),ert-1基因和切花保鲜相关调控因子;乙醇、乙醛、DPSS和钴等做一综述。 相似文献
80.
喀斯特脆弱生态系统复合退化控制与重建模式 总被引:25,自引:3,他引:22
以西南喀斯特地区为例,通过总结前人的研究成就和采集中国科学院亚热带农业生态研究所喀斯特生态实验站部分收集整理和试验数据,系统分析了喀斯特脆弱生态系统及其退化的机理,从"人-自然-经济复合生态系统"的观点出发,以干扰程度、群落类型、服务功能、土地退化和贫困状况为指标,创新性地提出了喀斯特脆弱生态系统的复合退化模式(含4个阶段),运用现代生态恢复学原理、方法和现代管理学创新理论,建立了喀斯特脆弱生态系统复合退化的控制模型.以此为基础,在喀斯特石山区、半石山区和土山丘陵区3个区域环境尺度范围内,针对性地建立了生态保护型、外向经济型和双三重螺旋3种生态恢复与重建模式,以促进喀斯特区域生态、经济、社会的全面协调与可持续发展. 相似文献