全文获取类型
收费全文 | 1221篇 |
免费 | 153篇 |
国内免费 | 12篇 |
专业分类
财政金融 | 4篇 |
工业经济 | 77篇 |
计划管理 | 136篇 |
经济学 | 63篇 |
综合类 | 37篇 |
运输经济 | 1篇 |
旅游经济 | 7篇 |
贸易经济 | 125篇 |
农业经济 | 139篇 |
经济概况 | 112篇 |
水利工程 | 685篇 |
出版年
2024年 | 1篇 |
2023年 | 15篇 |
2022年 | 24篇 |
2021年 | 25篇 |
2020年 | 24篇 |
2019年 | 36篇 |
2018年 | 33篇 |
2017年 | 31篇 |
2016年 | 46篇 |
2015年 | 46篇 |
2014年 | 75篇 |
2013年 | 122篇 |
2012年 | 92篇 |
2011年 | 121篇 |
2010年 | 97篇 |
2009年 | 88篇 |
2008年 | 70篇 |
2007年 | 83篇 |
2006年 | 100篇 |
2005年 | 91篇 |
2004年 | 67篇 |
2003年 | 22篇 |
2002年 | 20篇 |
2001年 | 24篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1989年 | 3篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
排序方式: 共有1386条查询结果,搜索用时 718 毫秒
101.
针对印染废水水质水量变化大、可生化性差、COD和色度去除不稳定和脱氮效率低等问题,采用高效厌氧处理、生物强化处理以及深度处理技术路线,开发了折流式厌氧水解(ABR水解)-A/O(PACT)-深度处理工艺,建立了中试研究基地和示范工程,根据处理规模为2万m3/d的示范工程处理效果,出水COD、总氮、氨氮、总磷和色度去除率分别为90.9%、78.5%、89.2%、92.2%和91.4%,出水水质可稳定达到《太湖地区城镇污水处理厂及重点工业行业主要水污染物排放限值》(DB 32/1072—2007),工程投资为1 650元/m3,直接运行费用1.7元/m3。 相似文献
102.
为研究水库水经国内常规给水处理工艺的各阶段出水中有机提取物对细胞DNA损伤的情况,于8月和1月取水库水作为原水,设定采集4个水样:原水(A)、经混凝沉淀后的沉后水(B)、滤后水(C)和经氯消毒的出水(D)。提取水样中的有机物配成不同浓度溶液,喂食小白鼠,取小白鼠脾脏细胞做彗星实验。结果无论在枯水期还是丰水期,水处理工艺各阶段出水对DNA都有不同程度的损伤,损伤程度顺序:A〉B〉D〉C;丰水期水样对DNA损伤程度高于枯水期水样对DNA的损伤。结果表明,水库水中的有机物污染物具有一定的遗传毒性,常规给水处理工艺对遗传毒性有削减作用,但不能消除。加氯消毒增加了水库水的遗传毒性。 相似文献
103.
John Leju Celestino LADU Xi-wu Lü 《水科学与水工程》2014,7(2):168-182
With rural population expansion and improvement of the socio-economic standard of living, treatment of rural domestic wastewater has rapidly become a major aspect of environmental concern. Selection of a suitable method for treatment of rural domestic wastewater depends on its efficiency, simplicity, and cost-effectiveness. This study investigated the effects of hydraulic retention time(HRT), temperature, and effluent recycling on the treatment efficiency of an anaerobic filter(AF) reactor. The first round of experimental operations was run for three months with HRTs of one, two, and three days, temperatures of 18℃, 21℃, and 24℃, and no effluent recycling. The second round of experimental operations was conducted for another three months with HRTs of three and four days; temperatures of 30.67℃, 30.57℃, and 26.91℃; and three effluent recycling ratios of 1:1, 1:2, and 2:1. The first round of operations showed removal rates of 32% to 44% for COD, 30% to 35% for TN, 32% to 36% for +4NH-N, 19% to 23% for 3NO-N-, and 12% to 22% for TP. In the second round of operations, the removal rates varied from 75% to 81% for COD, 35% to 41% for TN, 31% to 39% for +4NH-N, 30% to 34% for 3NO-N-, and 41% to 48% for TP. The average gas production rates were 6.72 L/d and 7.26 L/d for the first and second rounds of operations, respectively. The gas production rate increased in the second round of operations as a result of applied effluent recycling. The best removal efficiency was obtained for an optimum HRT of three days, a temperature of 30℃, and an effluent recycling ratio of 2:1. The results show that the removal efficiency of the AF reactor was affected by HRT, temperature, and effluent recycling. 相似文献
104.
Based on the experiments of utilization of garlic processing wastewater in a lotus pond, this study demonstrates that lotus pond wetlands have a remarkable ability to remove organic pollutants and decrease chemical oxygen demand(CODCr), biochemical oxygen demand(BOD5), and suspended substances(SS) in garlic processing wastewater. Results also show evident effects of lotus roots on absorption of NH3-N. The pH value in a lotus pond with wastewater discharged was relatively stable. The water quality in the lotus pond reached the class Ⅱ emission standard, according to the Integrated Wastewater Discharge Standard(GB8978-1996), seven days after pretreated garlic processing wastewater had been discharged into the lotus pond. Garlic processing wastewater irrigation does not produce pollution in the pond sediment and has no negative effect on the growth of lotus roots. Due to utilization of garlic processing wastewater, the output of lotus roots increased by 3.0% to 8.3%, and the quality of lotus roots was improved. Therefore, better purification and utilization results can be achieved. 相似文献
105.
It has been widely recognized that urban wastewater reuse is an alternative for water shortage problem. Although the improvement
on urban wastewater reuse in China is quite significant, the further development still requires more strategic regulating
and directing at the national level. However, due to the huge spatial differences in social–economic and resource conditions
among different areas in China, it is difficult to apply a same policy framework to the whole country. In the paper, the mainland
of China has been divided into 342 research regions and each region has one large-scale or medium-scale central city. The
paper tried to answer the question how to select the development pattern of urban wastewater reuse for each region. Firstly,
in order to evaluate the necessity and regional economic feasibility to develop urban wastewater reuse, an indicator system
with three indexes at the upper level and seven indicators at the lower level was build up. And valuing method and the weight
for each indicator was given. All the research regions covering the mainland of China has been scored with the indicator system.
Secondly, the national strategic zoning has been done with the key method of cluster analysis. All regions have been sorted
into five types of strategic development zones. Each zone has its own wastewater reuse development option such as Preferential
Imperative Development, State Supporting Development, Self Supporting Development, Waiting for Development, and Non-Mandatory
Development. Thirdly, the corresponding policy suggestion for each zone was given to the government. The possible updates
between the different development patterns have been discussed as well. 相似文献
106.
TNT炸药废水三维电解氧化实验研究 总被引:2,自引:0,他引:2
以不锈钢作为阳极的三维电解反应器对废水的实验研究表明:在最佳电解条件下(极板间距4 cm、电压15 V、pH为3,绝缘粒子与活性炭粒子质量比为0.3,电流强度0.15 A时),电解3 h后TNT和COD的去除率分别为93 %和78 %.并探讨了电化学氧化处理TNT废水的机理. 相似文献
107.
采用厌氧—缺氧—ALMBR工艺处理焦化废水。在充填了横断面具有蜂窝胞壁结构纤维滤料的厌氧池和缺氧池中收集池内出气作为气源回曝气池中,在缺氧的条件下形成气升循环。好氧池为气提升三相循环流化床结构的MBR(ALMBR),不设二沉池,MLSS高达11~12 g/L。连续3个月的试验表明,焦化废水进水COD_(Cr)1950 mg/L、NH_3—N 150 mg/L时,出水COD_(Cr) 144 mg/L、NH_3—N 9.8 mg/L。工艺具有良好的抗冲击负荷能力,能够维持较高的污泥浓度,运行稳定,操作简单且管理方便。装有蜂窝胞壁填料的缺氧池COD_(Cr)去除率明显高于装有软性纤维填料缺氧池。 相似文献
108.
Aija Kosk 《Lakes & Reservoirs: Research and Management》2001,6(3):231-235
Lake Peipsi is the fourth largest lake in Europe and the largest international lake in Europe. Lake Peipsi is shallow, eutrophic, biologically very productive and is bordered by many wetland areas along its coasts. Large peat deposits in the Lake Peipsi basin are protected under national legislation. The lake is most important as a resource for recreation and fisheries. The fish stock in Lake Peipsi is one of the richest in Europe. The most critical environmental issues for the Peipsi watershed are eutrophication and unregulated fishing in the lake. During the Soviet period, large collective farms dramatically accelerated eutrophication. Despite the drop in fertilizer use during the last 10 years and a decrease in the number of domestic animals in the watershed, the impact of the earlier agricultural pollution is still significant. Untreated sewage has also been dumped in the Narva River tributary as a result of an international dispute concerning water supply and wastewater treatment. People living in the Lake Peipsi region have faced traumatic changes as a result of the re‐establishment of the border between Russia and Estonia in 1992. The establishment of an international border on the waters of the lake has resulted in fishermen losing access to many of their traditional fishing areas. Political and economic transformations of the last 10 years have seriously interrupted information exchange between different institutions and organizations concerned with the health of the lake. The Centre for Transboundary Cooperation facilitates international communication and cooperation between the Estonian and Russian governments and promotes public participation in environmental, social and economic development and decision‐making. The centre is in the process of guiding the development of a watershed management plan for the Lake Peipsi watershed and a vision for watershed development that is truly sustainable. 相似文献
109.
110.
深圳河湾水系生态需水的污水资源化 总被引:1,自引:0,他引:1
以深圳河湾水系为例,探讨以污水资源化再生水满足城市水系生态需水的方法。该方法统一考虑河流的水量水质需求,计算不同截污率和补水水质条件下河流的生态需水量;根据生态用水的供需平衡情况,确定污水资源化规模与水质要求。在此基础上,设计污水资源化的处理工艺以及再生水厂等的分布;并通过数学模型预测补水方案对水环境改善的效果。本研究为面向城市水系生态补水的污水资源化工程规划提供了科学的方法。 相似文献