共查询到11条相似文献,搜索用时 62 毫秒
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土地资源相对匮乏,耕地总量和人均占有量逐年减少,各类用地需求矛盾日益尖锐,是我国的基本国情。因此,近十几年来,国家采取了各种措施以抑制耕地减少的趋势。然而,伴随着经济社会的空前快速发展,建设用地规模也一直以前所未有的速度迅速增加,耕地面积仍在不断减少。如,2003年的土地利用变更调查结果显示,全国耕地面 相似文献
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针对影响当前征地补偿安置落实的多种因素,对改进和完善征地补偿制度.保障农民土地权益提出了5项措施:一是限制征用土地范围,减少圈占耕地行为;二是依法落实补偿政策.保证费用足额到位。三是实行以土地换社保,保障农民长远生计;四是探索集体土地流转,合理分配土地收益。五是加大土地.执法力度.严肃查处违法行为。 相似文献
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ISO19100地理信息系列标准特点及其本土化 总被引:6,自引:3,他引:6
采用国际标准和国外先进标准是国民经济发展的重要技术基础工作。文章简略介绍国际标准化组织地理信息技术委员会(ISO/TC211)研制ISO19100地理信息系列标准的概况,着重分析其结构体系、研制特点,讨论将这些标准转化为国家标准,即本土化工作应当遵循的原则、方法、国家标准与国际标准一致性程度划分等问题,并提出ISO19100地理信息系列标准本土化工作的建议。 相似文献
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教学评价是提升高等学校教育质量的重要手段,而课堂教学质量评价又是实施教学评价的关键性环节,直接关系到教学评价的指向和功能的发挥.通过对课堂教学评价系统多方面、内在的分析,提出需要建立一种符合社会最终需求的课堂教学评价系统导向性,即以学生为课堂教学评价的主体,以培养具有创新意识和发展潜能的人才作为教学评价的目标,并对相应解决方案进行了有针对性地研究与探讨. 相似文献
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Metabolism of polychaete Neanthes japonica Izuka: relations to temperature, salinity and body weight
Polychaete Neanthesjaponica is a species geographically specific in China and Japan with important scientific implication and commercial value. In this study, the relations of body weight, salinity and temperature to oxygen consumption and ammonia excretion of N. japonica were determined. Threedifferent groups in body weight (large: 2.34±0.36 g, middle: 1.50±0.21 g and small: 0.62±0.12 g) were set for all experiments. Results show that the body weight is negatively related to the rates of oxygen consumption and ammonia excretion; and the relationship is significant. The oxygen consumption and ammonia excretion at 24℃ decreased at salinity from 5 to 30 and increased above 30, indicating that both lower and higher salinity are adverse and certain degree of salinity stress is necessary for enhancing the energy demand. At salinity 30, rising temperature from 18℃ to 30℃, the oxygen consumption increased before 27℃ and then decreased. However, the relation of ammonia excretion and temperature seems more complex. Two-way ANOVA shows that salinity, temperature and body weight all have a significant effect on the oxygen consumption and ammonia excretion of the worm. Moreover, interaction between salinity/temperature and body weight is also significant. O:N (oxygen/nitrogen) ratio varies greatly in this case from 5.97 to 463.22, indicating that N. japonica can regulate the type of metabolic substrate against environment changes. 相似文献
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Metabolism of polychaete Neanthes japonica Izuka: relations to temperature, salinity and body weight
Polychaete Neanthes japonica is a species geographically specific in China and Japan with important scientific implication and commercial value. In this
study, the relations of body weight, salinity and temperature to oxygen consumption and ammonia excretion of N. japonica were determined. Three different groups in body weight (large: 2.34±0.36 g, middle: 1.50±0.21 g and small: 0.62±0.12 g) were
set for all experiments. Results show that the body weight is negatively related to the rates of oxygen consumption and ammonia
excretion; and the relationship is significant. The oxygen consumption and ammonia excretion at 24°C decreased at salinity
from 5 to 30 and increased above 30, indicating that both lower and higher salinity are adverse and certain degree of salinity
stress is necessary for enhancing the energy demand. At salinity 30, rising temperature from 18°C to 30°C, the oxygen consumption
increased before 27°C and then decreased. However, the relation of ammonia excretion and temperature seems more complex. Two-way
ANOVA shows that salinity, temperature and body weight all have a significant effect on the oxygen consumption and ammonia
excretion of the worm. Moreover, interaction between salinity/temperature and body weight is also significant. O:N (oxygen/nitrogen)
ratio varies greatly in this case from 5.97 to 463.22, indicating that N. japonica can regulate the type of metabolic substrate against environment changes.
Supported by the National Natural Science Foundation of China (No. 30490233) and the Three-Gorge Project and the Estuarine
Environment (No. SX2004-018) from the Three Gorges Project Construction Committee 相似文献
8.
This study examines the technical efficiency (TE) differences among typical cropping systems of smallholder farmers in the purple-soiled hilly region of southwestern China. Household-, plot-, and crop- level data and community surveys were conducted to explore TE levels and determinants of typical cropping systems by using a translog stochastic frontier production function. Results indicate significant difference in TE and its determinants among cropping systems. The mean TEs of the rice cropping system (R), the rice-rape cropping system (RR), the rice-rape-potato cropping system (RRP), and the oil cropping system (O) are 0.86, 0.90, 0.84, and 0.85, respectively, which are over 1.17 times higher than those of the maize-sweet potato-other crop cropping system (MSO) and the maize-sweet potato-wheat cropping system (MSW) at 0.78 and 0.69, respectively. Moreover, Technical inefficiency (TIE) of different cropping systems is significantly affected by characteristics of the household as well as plot. However, the impact of land quality, mechanical cultivation conditions, crop structure, farming system, farm radius, household type, cultivated land area per capita, and annual household income per capital on TIE vary by cropping system. Additionally, output elasticity of land, labor, and capital, as a group, is greater than the one of agricultural machinery and irrigation. Finally, when household-owned effective agricultural labor is at full farming capacity, optimal plot sizes for the R, RR, RRP, MSO, MSW, and O cropping systems are 1.12 hm2, 0.35 hm2, 0.25 hm2, 2.82 hm2, 1.87 hm2, and 1.17 hm2, respectively. 相似文献
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Md. Abu Sayeed Mostafa Ali Reza Hossain Md. Abdul Wahab Md. Tawheed Hasan Kumar Das Simon Sabuj Kanti Mazumder 《中国海洋湖沼学报》2015,33(4):895-904
A study was conducted to investigate the status of the water and sediment quality in the Chalan Beel——a major fresh water fish reservoir of the country for a period of one year from July 2007 to June 2008. The mean values of water quality parameters(depth: 214.73±152.22 cm, temperature 27.68±4.26℃, transparency 123±82 cm, p H 9.7±0.47, total alkalinity 137±42 mg/L, conductivity 307±147 μs/cm, total dissolved solids 183±89 mg/L, ammonia-N 0.27±0.39 mg/L, nitrate-N 0.09±0.07 mg/L, phosphate-P 2.01±2.53 mg/L) and sediment quality parameters(p H 7.21±0.35, organic matter 2.59±0.52%, total nitrogen 0.09±0.04%, available phosphorus 5.4±3.6 Meq./100 g and exchangeable potassium 0.43±0.14 Meq./100 g) were within the range recommended for most of the inland fishes of Bangladesh. Although the water and sediment quality parameters except ammonia and phosphate are in the suitable range, the overall results suggest that better management techniques should be practiced in order to overcome the declining trend of associated aquatic life(fauna and flora) of this important fresh water body of Bangladesh. 相似文献
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Two cruises were conducted in January and July 1986 in the Changjiang (Yangtse River) Estuary and its adjacent East China Sea (30°45′ -32°00′N,121°00′-124°00′E). Direct epifluorescence counts of planktonic bacteria and determinations of ATP concentrations were made. Subsamples were taken for measurement of oxygen consumption rates and chlorophyll concentrations.Bacteria and ATP concentrations were higher in summer than in winter, highest in the river and the river mouth, and gradually lower offshore. The bacteria number was correlated positively with suspended matter, nitrates and oxygen consumption rates, and negatively with salinity.In winter bacteria were the main contributors of ATP and the main consumers of dissolved oxygen in the whole studied area. In summer two maxima of ATP were found along the salinity gradient. The first one which coincided with the peak of turbidity near the river mouth was attributed to bacte -ria, and the second which occurred in the waters with a salinity range be 相似文献
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丽水凹陷作为东海陆架盆地具有较大勘探潜力的凹陷,其勘探程度较低,近年来钻探成果较小,因此亟需对烃源岩进行综合评价。通过烃源岩岩石热解实验,饱和烃气相色谱及饱和烃色质分析,对丽水凹陷烃源岩进行综合评价。结果表明,丽水凹陷烃源岩有机质类型以Ⅲ型为主,存在少量的Ⅱ1及Ⅱ2型。月桂峰组烃源岩处于成熟到过成熟阶段,灵峰组烃源岩处于成熟阶段,多数明月峰组烃源岩成熟度较低。根据烃源岩热解参数S1及有机碳含量(TOC)的关系确定月桂峰组有效烃源岩w(TOC)下限为0.7%,灵峰组有效烃源岩w(TOC)下限为1.0%,明月峰组有效烃源岩w(TOC)下限为0.9%。生标参数显示丽水凹陷烃源岩有机质具有混合来源特征,沉积于海陆过渡环境中。有效烃源岩平面分布预测显示,丽水凹陷有效烃源岩的分布较为局限,丽水凹陷西次凹的东北部为有效烃源岩的集中分布区。月桂峰组及灵峰组烃源岩具有较大的产气潜力,应加大丽水凹陷西次凹东北部的气藏勘探力度。 相似文献