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151.
３细部调整 物体的细部刻画可以被认为是一项比较复杂而细致的工作,但在 Ａｕｔｏ ＣＡＤ中则变得很简单了,使用有关命令可以让您轻松自如地完成每一项工作,对于图６中的视图,还需做如下工作： （１）将门的边和抽屉的边倒成圆角; （２）在经理台的面上添加一块柔性的书写 相似文献
152.
153.
We estimated forest biomass carbon storage and carbon density from 1949 to 2008 based on nine consecutive forest inventories in Henan Province,China.According to the definitions of the forest inventory,Henan forests were categorized into five groups: forest stands,economic forests,bamboo forests,open forests,and shrub forests.We estimated biomass carbon in forest stands for each inventory period by using the continuous biomass expansion factor method.We used the mean biomass density method to estimate carbon stocks in economic,bamboo,open and shrub forests.Over the 60-year period,total forest vegetation carbon storage increased from34.6 Tg(1 Tg = 1×10~(12)g) in 1949 to 80.4 Tg in 2008,a net vegetation carbon increase of 45.8 Tg.By stand type,increases were 39.8 Tg in forest stands,5.5 Tg in economic forests,0.6 Tg in bamboo forests,and-0.1 Tg in open forests combine shrub forests.Carbon storageincreased at an average annual rate of 0.8 Tg carbon over the study period.Carbon was mainly stored in young and middle-aged forests,which together accounted for 70–88%of the total forest carbon storage in different inventory periods.Broad-leaved forest was the main contributor to forest carbon sequestration.From 1998 to 2008,during implementation of national afforestation and reforestation programs,the carbon storage of planted forest increased sharply from 3.9 to 37.9 Tg.Our results show that with the growth of young planted forest,Henan Province forests realized large gains in carbon sequestration over a 60-year period that was characterized in part by a nation-wide tree planting program. 相似文献
154.
噪声对人体及生活等有很大的危害,塔里木大学现有学生宿舍楼12栋,教职工住宅楼20栋。通过调查研究,分析本校现有的宿舍楼及教职工家属楼室内声环境的基本情况及产生噪声的各种原因,提出相应的改进措施,为建筑室内声环境的提高和建筑的设计提供改进参考。并且在声环境方面通过具体的调查找出对振动和噪声的控制、解决方法,从而消除或适当的减少室内外噪声,以创造一个可接受的声学环境。 相似文献
155.
156.
双马来海松酸酯多元醇的合成研究 总被引：7，自引：0，他引：7
利用马来海松酸中酸酐和羧基反应活性的差异，合成了两种类型的双马来海松酸酯多元醇．测试了酯化产物的分子量、聚合度、粘度、羟值和官能度等理化参数；并对各产物的耐热性和红外光谱进行了讨论．研究结果表明，所有酯化产物均可作为耐热的多元醇原料使用． 相似文献
157.
Li ZM Ma Y Guddat L Cheng PQ Wang JG Pang SS Dong YH Lai CM Wang LX Jia GF Li YH Wang SH Liu J Zhao WG Wang BL 《Pest management science》2012,68(4):618-628
BACKGROUND: The herbicide sulfonylurea (SU) belongs to one of the most important class of herbicides worldwide. It is well known for its ecofriendly, extreme low toxicity towards mammals and ultralow dosage application. The original inventor, G Levitt, set out structure–activity relationship (SAR) guidelines for SU structural design to attain superhigh bioactivity. A new approach to SU molecular design has been developed. RESULTS: After the analysis of scores of SU products by X‐ray diffraction methodology and after greenhouse herbicidal screening of 900 novel SU structures synthesised in the authors' laboratory, it was found that several SU structures containing a monosubstituted pyrimidine moiety retain excellent herbicidal characteristics, which has led to partial revision of the Levitt guidelines. CONCLUSIONS: Among the novel SU molecules, monosulfuron and monosulfuron‐ester have been developed into two new herbicides that have been officially approved for field application and applied in millet and wheat fields in China. A systematic structural study of the new substrate–target complex and the relative mode of action in comparison with conventional SU has been carried out. A new mode of action has been postulated. Copyright © 2011 Society of Chemical Industry 相似文献
158.
不同种源地沙枣种子在萌发期的耐盐性比较 总被引：1，自引：0，他引：1
沙枣(Elaeagnus angustifolia L.)是一种耐盐碱、耐干旱、耐贫瘠的木本粮食树种,在我国西北地区广泛种植,因其优良特性,近几年来,人们尝试在盐碱地区和退耕贫瘠地区引种。本研究共收集了11个不同种源地的沙枣种子,分别用不同浓度NaCl(0%、0.3%、0.6%、0.9%和1.2%)处理,统计在不同处理条件下沙枣种子的发芽率、发芽势和发芽指数,并利用隶属函数对不同种源地沙枣种子萌发期的耐盐性进行排序。结果表明,11个种源地沙枣萌发期耐盐性由强到弱顺序为:甘肃民勤大果沙枣、甘肃石羊河大果沙枣、宁夏银北沙枣、新疆大果沙枣、新疆吐鲁番大果沙枣、新疆吐鲁番沙枣、甘肃金昌沙枣、宁夏陶乐沙枣、甘肃临泽沙枣、甘肃民勤沙枣、宁夏中宁沙枣。并选出适于在黄河三角洲引种的甘肃石羊河大果沙枣、新疆吐鲁番沙枣和宁夏陶乐沙枣。 相似文献
159.
Temperate and boreal forests act as major sinks for atmospheric CO2. To assess the magnitude and distribution of the sinks more precisely, an accurate estimation of forest biomass is required. However, the determinants of large-scale biomass pattern (especially root biomass) are still poorly understood for these forests in China. In this study, we used 515 field measurements of biomass across the northeast part of China, to examine factors affecting large-scale biomass pattern and root–shoot biomass allocation. Our results showed that, Picea & Abies forest and coniferous & broadleaf mixed forest had the highest mean biomass (178–202 Mg/ha), while Pinus sylvestris forest the lowest (78 Mg/ha). The root:shoot (R/S) biomass ratio ranged between 0.09 and 0.67 in northeast China, with an average of 0.27. Forest origin (primary/secondary/planted forest) explained 31–37% of variation in biomass (total, shoot and root), while climate explained only 8–15%, reflecting the strong effect of disturbance on forest biomass. Compared with shoot biomass, root biomass was less limited by precipitation as a result of biomass allocation change. R/S ratio was negatively related to water availability, shoot biomass, stand age, height and volume, suggesting significant effects of climate and ontogeny on biomass allocation. Root–shoot biomass relationships also differed significantly between natural and planted forests, and between broadleaf and coniferous forests. Shoot biomass, climate and forest origin were the most important predictors for root biomass, and together explained 83% of the variation. This model provided a better way for estimating root biomass than the R/S ratio method, which predicted root biomass with a R2 of 0.71. 相似文献
160.