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771.
资源是区域经济发展的基础,资源结构是区域产业结构赖以形成的重要条件。区域产业是经济发展的载体,它不仅支持着区域的增长,而且在很大程度上决策着经济增长的能力与潜力。据此,在分析湖南省资源及产业结构优化标准的基础上,提出了充分与合理利用资源的产业对策建议。  相似文献   
772.
分析了圆管压入扩径时内径变化的规律和影响因素.理论分析和实验结果相一致,对实际生产中产品质量的控制有参考价值.  相似文献   
773.
Selecting guidelines to evaluate elevated metals in urban brownfields is hindered by the lack of information for these sites on ecosystem structure and function. A study was performed to compare three trace metal-contaminated sites in the metropolitan Montreal area. The goal was to obtain an idea of the organisms that may be present on urban brownfields and to measure if elevated metals alter the presence and activity of the indigenous biota. Field and laboratory studies were conducted using simple methodologies to determine the extent to which microbial activity affected by trace metal content, to assess diversity of plant and soil invertebrate communities and to measure phytoaccumulation of trace metals. It was found that microbial activity, as measured by substrate-induced respiration (SIR) and nitrification, was not affected by the levels of soil Cd, Cu, Ni, Pb and Zn recorded on the sites. Seven of the 12 invertebrate groups collected were sampled on soils with similar Cd, Cu, Ni, Pb and Zn concentrations. Diversity of plant species increased as a function of the length of time the sites had been inactive. Levels of metals in plant tissue were influenced by soil characteristics and not by total soil Cd, Cu, Ni, Pb and Zn.  相似文献   
774.
The aphid alarm pheromone (E)-β-farnesene (EβF) is an efficient signal that warns aphids of attack by natural enemies. In this field study, eight open-top chambers (OTCs) located in Beijing, China (40°11′N, 116°24′E) with spring wheat Triticum aestivum were used to examine the response of the grain aphid Sitobion avenae to CO2 (ambient vs. double ambient) and EβF (applied zero, two, or five times each day). We experimentally tested the hypotheses that, depending on frequency of EβF release, elevated CO2 reduces the response (in terms of population density) of S. avenae to EβF, and that lower activity of acetylcholinesterase (AChE) in S. avenae may be involved in its reduced sensitivity to EβF under elevated CO2. Numbers of S. avenae declined with increased frequency of EβF application under ambient CO2 but were unaffected by EβF application under elevated CO2. Additionally, the mean relative growth rate (MRGR) and the dry material and amino acid content of S. avenae increased with elevated CO2 but declined when with EβF application. Activities of superoxide dismutase and catalase were higher in S. avenae under elevated vs. ambient CO2. Under elevated CO2, however, AChE activity remained low when S. avenae was exposed to the lower EβF frequency, while the highest AChE activity occurred in aphids exposed to the higher EβF frequency. These results indicate that aphids become insensitive to EβF under elevated CO2, perhaps because of decreased AChE activity.  相似文献   
775.
数字水准仪DiNi11/12原理及应用中应注意的问题   总被引:2,自引:0,他引:2  
本文介绍了数字水准仪的原理、特点,着重分析了对台站跨断层观测精度影响较大的几个因素,并结合台站工作实际提出了减弱这些影响的措施,实测结果表明:采取这些措施可以有效地提高测量精度.  相似文献   
776.
在城市环境目益恶化的今天,景观生态设计问题越来越受到人们的重视。此文从环境和生态的观点出发分析现代景观设计,并以中山岐江公园为例探讨景观设计与环境保护和生态主义之议题,提出景观设计创作之初应先进行环境评估,立足于环境保护和生态主义的景观设计才更具生命力。  相似文献   
777.
选择三户典型城市家庭作为研究对象,对其家庭生活污水进行调查与分析.结果表明:城市家庭生活用水类型较多,主要分为洗澡水、洗衣水、淘米水、洗漱水、洗莱水、洗碗水、厕所用水和其它用水八个类型.所调查城市家庭人均用水量为217.84L/人·d,其范围在151.51~264.00L/人·d.所调查城市家庭生活污水的pH值的范围为6.14—7.43;浊度范周为13-221.6度;TP浓度的范围为0.69—3.18mg/L;COD浓度范围为5.9—1368.8mg/L。  相似文献   
778.
A spectacular new terrestrial Konzentratlagerst?tte is introduced from the Turpan Basin of Xinjiang, China that probably belongs to the late Middle Jurassic Qigu Formation. It contains a mass accumulation of “xinjiangchelyid” turtles preliminarily identified as Annemys sp. In the zone with the highest turtle concentration, complete and articulated turtle skeletons are tightly packed at a density of up to 36 turtles per square meter. The fossiliferous layer is thickened here and shows an erosional base. This high concentration zone outcrops approximately 10?m in length and shows no decrease in turtle density after exposing 2?m of the layer into the hillside. Adjacent is a more expansive zone of at least 10?m by 30?m. In this region, the fossiliferous layer is evenly thick, and approximately five, fully disarticulated turtles are present per square meter. A conservatively estimated 1,800 turtles may, therefore, have been deposited at this site. It is likely that these aquatic turtles gathered in a retreating water hole in a riverine environment during a drought, much as some aquatic turtles will do today, but perished when the habitat dried up completely. A following catastrophic rainfall event caused a debris flow, possibly channelized in a dry river bed, which transported complete turtles, disarticulated turtles, and mudstone clasts and deposited them after a short distance. This taphonomic model is consistent with previous environmental reconstructions of the Turpan Basin during the late Middle Jurassic in predicting the episodic breakdown of regional monsoonal circulation resulting in a seasonally dry climate with severe episodic droughts.  相似文献   
779.
为了实现小区生活污水再利用,进行以聚丙烯腈活性炭纤维(PAN-ACF)为载体的生物膜法处理小区生活污水的实验研究,以生活污水中COD、NH3-N、SS、浊度、pH等为检测指标来研究反应器的处理效果,实验结果表明该反应器对生活污水中COD、NH3-N、SS、浊度有非常高的去除效率,而且抗冲击负荷能力较强,以上指标出水均符合"城市污水再生利用城市杂用水水质标准"(GB/T18920-2002)中城市绿化规定的水质标准。此外,实验表明聚丙烯腈活性炭纤维(PAN-ACF)作为生物膜载体具有很好的生物亲和性。  相似文献   
780.
尹宜舟  高歌  王国复 《灾害学》2021,(2):19-23,29
该文拓展了面向气象灾害损失评价的灾体模型,使得其适用性增强。基于新模型,对2003-2018年我国主要气象灾害损失及总损失年景进行了评价分析,结果显示,存在极端偏重灾害损失年景的有暴雨洪涝(2003、2010年)、台风(2005、2006年)、低温冷冻害和雪灾(2005、2008年),另外各气象灾害偏重及以上的年景主要分布在2003-2013年,2014-2018年相对灾体量指数平均值较2003-2013年(不含极端年份)偏少65%~90%;在气象灾害总损失年景评价中增加考虑倒塌房屋和饮水困难人口两个损失要素后,评价涉及的信息更加全面,评价结果更趋完善。  相似文献   
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