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长期秸秆覆盖免耕对土壤某些理化性质及玉米产量的影响 被引量:131
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作者 张志国 徐琪 R.L.Blevins 《土壤学报》 CAS CSCD 北大核心 1998年第3期384-391,共8页
免耕农作是一项重要的农业生态管理系统。长期秸秆覆盖免耕条件下土壤性质的变化及作物产量可以反映这一系统的可持续性。研究表明,长期(1970年—1994年)免耕与犁耕相比土壤容重并未增加;而表层(0—5cm)土壤有机C和有机N显著增加;... 免耕农作是一项重要的农业生态管理系统。长期秸秆覆盖免耕条件下土壤性质的变化及作物产量可以反映这一系统的可持续性。研究表明,长期(1970年—1994年)免耕与犁耕相比土壤容重并未增加;而表层(0—5cm)土壤有机C和有机N显著增加;并有随N肥施用量增加而增加的趋势。土壤pH随NH4NO3化肥施用量的增加而明显降低。免耕表层土壤的交换性Ca、Mg、K和可提取P与犁耕比较有明显的表聚现象。交换性Ca、Mg、及可提取P随NH4NO3施用量的增加而减少。交换性K的分布则不受N肥施用量的影响,从1984至1994年,免耕玉米的产量显著高于犁耕玉米的产量,从1970至1982年犁耕玉米的产量略高于免耕,但并不显著。 展开更多
关键词 免耕 持续性农业 土壤理化性质 玉米产量
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扩散火焰合成碳纳米管研究 被引量:38
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作者 潘春旭 Liming Yuan Kozo Saito 《新型炭材料》 SCIE EI CAS CSCD 2001年第3期24-27,共4页
利用扩散火焰合成碳纳米管是一项新的技术和方法。介绍了这种新方法的基本原理 ,较系统地研究了火焰参数、基板材料、合成时间等对碳纳米管形态的影响。初步研究表明它在无外加催化剂的情况下也能合成碳纳米管 ,具有“自生催化”
关键词 碳纳米管 扩散燃烧 自生催化 扩散火焰合成
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我国不同类型烟叶烟碱向降烟碱转化研究 被引量:33
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作者 史宏志 L.P.Bush +1 位作者 J.Wang 刘国顺 《中国烟草科学》 CSCD 2001年第4期6-8,共3页
对我国不同类型烟叶生物碱含量和烟碱向降烟碱转化的株间变异研究表明,白肋烟和沙姆逊香料烟降烟碱占总生物碱比例高,不同样品间变化幅度和变异性大,烟碱向降烟碱转化问题比较突出。单株分析表明,白肋烟JB80和TN9O群体中转化株比例分别... 对我国不同类型烟叶生物碱含量和烟碱向降烟碱转化的株间变异研究表明,白肋烟和沙姆逊香料烟降烟碱占总生物碱比例高,不同样品间变化幅度和变异性大,烟碱向降烟碱转化问题比较突出。单株分析表明,白肋烟JB80和TN9O群体中转化株比例分别为20.0%和18.3%,且50%以上的转化株为转化率在20%以上的高转化株。烤烟转化株比例和转化程度较低。去除转化株后的纯化群体,其生物碱组成得到优化。 展开更多
关键词 烟叶 类型 烟碱 降烟碱转化 生物碱含量
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Iron Phosphate Coating: A Novel Approach to Controlling Pyrite Oxidation 被引量:2
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作者 HUANGXIAO V.P.EVANGELOU 《Pedosphere》 SCIE CAS CSCD 1997年第2期103-110,共8页
A novel coating technique was developed for controlling Pyrite oxidation. The technique invo1ved leachingpyrite particles with a solution containing low concentrations of phosphate and hydrogen peroxide. Duringthe lea... A novel coating technique was developed for controlling Pyrite oxidation. The technique invo1ved leachingpyrite particles with a solution containing low concentrations of phosphate and hydrogen peroxide. Duringthe leaching process, the iron released from pyrite by hydrogen proxide was precipitated by phosphate as aferric phosphate coating. This coating was shown to be able to effectively prevent Pyrite from oxidation and itcould be established at the expense of only surface portions of Pyrite. The emergence of this technique couldprovide a unique potential route for abating acid mine drainage and reclaiming sulfide-containing degradedmining land. 展开更多
关键词 酸性矿山 排水装置 覆盖 黄铁矿 磷酸盐 保护 氧化作用
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Influence of nitrogen fertilization rate and alleles at the yellow burley loci on TSNA formation in air cured to- bacco.
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作者 RamseyS.Lewis RobbieParker +3 位作者 AnneJack DavidDanehower ScottWhiteley LowellBush 《中国烟草学报》 EI CAS CSCD 2011年第6期31-31,共1页
关键词 摘要 编辑部 编辑工作 读者
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Tracking White Matter Fiber in Human Brain
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作者 KANGNing ZHANGJun EricSCarlson 《上海大学学报(自然科学版)》 CAS CSCD 2004年第B10期13-17,共5页
A new approach for noninvasively tracing brain white matter fiber tracts is presented using diffusion tensor magnetic resonance imaging (DT-MRI) data. This technique is based on successive anisotropic diffusion simula... A new approach for noninvasively tracing brain white matter fiber tracts is presented using diffusion tensor magnetic resonance imaging (DT-MRI) data. This technique is based on successive anisotropic diffusion simulations over the human brain, which are utilized to construct three dimensional diffusion fronts. The fiber pathways are determined by evaluating the distance and orientation from fronts to their corresponding diffusion seeds. Real DT-MRI data are used to demonstrate the tracking scheme. It is shown that several major white matter fiber pathways can be reproduced noninvasively, with the tract branching being allowed. Since the diffusion simulation,which is a truly physical phenomenon reflecting the underlying architecture of cerebral tissues, makes full use of the entire diffusion tensor data, the proposed approach is expected to enhance robustness and reliability of the DT-MRI based fiber tracking techniques in white matter fiber reconstruction. 展开更多
关键词 人脑 各项异性扩散模拟 DT-MRI 神经纤维 图像处理
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Experiment and research on development and characterizations of anodic alumina membrane for use in hemodialysis
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作者 ZHANG Wei-ming QIANJia-qi +2 位作者 HUANG Zhong-ping YU Jian-ping GAO Da-yong 《上海第二医科大学学报》 CSCD 北大核心 2005年第7期721-721,共1页
Objective: The correlation between various formative conditions and the pore characterizations of the anodic alumina membrane is investigated to seek the optimal conditions for the formation of anodic alumina membrane... Objective: The correlation between various formative conditions and the pore characterizations of the anodic alumina membrane is investigated to seek the optimal conditions for the formation of anodic alumina membrane. Methods: High purity aluminum foils are used as the starting materials. The anodization is conducted in three types of electrolytes, 3% sulfuric acid, 5% sulfuric acid and 2.7% oxalic acid, respectively, with different voltages at 0℃ for 48h. The characterizations of the pore size, the effective porosity and the pore porosity are observed and determined by scanning electron microscopy. The hydraulic conductances of the membranes are measured to confirm that the pores are open and evaluate the permselectivity of the membranes. Results: The experimental result shows that the ordered pore arrays are obtained for oxidation under our experimental conditions. With the increasing of the voltage, the pore size and pore porosity increased significantly ( P < 0.05) , while the effective porosity decreased significantly ( P < 0.05 ) with the same electrolyte. The pore size formed in 3% sulfuric acid or 5% sulfuric acid is much smaller than in 2.7% oxalic acid as an electrolyte. The hydraulic conductance of anodic alumina membrane that formed under our experimental condition is higher than those of the membranes are available currently used in clinical. Conclusion: The results suggest that the optimal conditions for the formation of anodic alumina membrane that used in hemodialysis are in 3% or 5% sulfuric acid with 12.5V to 17.5V at 0℃ for 48h. 展开更多
关键词 显微镜 氧化铝 人工膈膜 临床实验
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降低缺血性卒中病人同型半胱氨酸以预防再发卒中、心肌梗死和死亡——维生素干预预防卒中(VISP)随机对照试验
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作者 JamesF.Tbole M.ReneMalinow +8 位作者 LIoydE.Chambless J.DavidSpence LCreedPettigrew VirginiaJ.Howard ElizabethG.Sides Chin—HuaWang MeirStampher 张少衡 诸骏仁 《美国医学会杂志(中文版)》 2005年第1期12-17,共6页
背景:在观察性研究中,血浆总同型半胱氨酸水平升高与发生缺血型卒中的危险呈正相关。但是用同型半胱氨酸治疗降低卒中危险的效果尚未经随机试验证实。目的:与低剂量维生素比较,确定高剂量叶酸、维生素B6和B12降低总同型半胱氨酸水... 背景:在观察性研究中,血浆总同型半胱氨酸水平升高与发生缺血型卒中的危险呈正相关。但是用同型半胱氨酸治疗降低卒中危险的效果尚未经随机试验证实。目的:与低剂量维生素比较,确定高剂量叶酸、维生素B6和B12降低总同型半胱氨酸水平是否可降低2年再发卒中的危险。设计:双盲随机对照试验(1996年9月至2003年5月)。地点和参试者:美国、加拿大和苏格兰56所大学附属医院、社区医院、私人神经科诊所和退伍军人医学中心收治的3680例非致残脑梗死成年人。干预:所有参试者均接受最好的内、外科处理,每日服用多种维生素,包括美国食品与药物管理局参考建议每天摄取的其他维生素;病人随机接受每天一次内含维生素B6 25mg、维生素B12 0.4mg和叶酸2.5mg的高剂量制剂(n=1827)或者内含维生素B6 200μg、维生素B12 6μg和叶酸20μg的低剂量制剂(n=1853)。主要观察指标:再发脑梗死(一级结局);冠心病(coronary heart disease,CHD)事件和死亡(二级结局)。结果:高剂量组比低剂量组同型半胱氨酸总平均降低2μmoL/L,但对任何终点均无治疗作用。对任何卒中、CHD事件或死亡的未矫正危险比为1.0(95%CI,0.8~1.1),2年内发生一次事件的概率高剂量组为18.0%,低剂量组为18.6%。2年内发生缺血型卒中的危险高剂量组为9.2%,低剂量组为8.8%(危险比,1.0;95%CI,0.8~1.3)(治疗组间缺血型卒中差异一级假设log秩检验,P=0.8)。基线同型半胱氨酸总水平与结局呈恒定的梯度关系。总同型半胱氨酸下降3μmoL/L,低剂量组卒中危险减低10%(P=0.05),CHD事件危险减低26%(P<0.001),死亡危险减低16%(P=0.001);高剂量组危险的下降无显著性卒中为2%,CHD事件为7%,死亡为7%。结论:在本研究,非致残脑梗死后中度降低总同型半胱氨酸对2年随访期间血管结局并无明显影响。然而,总同型半胱氨酸与血管危险恒定相关的发现提示,对此仍值得进一步探索,可能还需要在不同的总同型半胱氨酸升高的人群进行更长时间的试验。 展开更多
关键词 降低缺血性卒中 同型半胱氨酸 预防 再发卒中 心肌梗死 死亡 维生素 干预 随机对照试验
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A EPC Approach to the Residual Water in Erythrocytes
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作者 ZHAOGang GUOXiao-jie +2 位作者 HELi-qun LIUZhong GAODa-yong 《Chinese Journal of Biomedical Engineering(English Edition)》 2004年第1期21-27,共7页
A novel approach has been developed to determine the amount of residual water in human erythrocyte at room temperature by electronic particle counter. Nacl solutions of 13 osmolalities were prepared and the equilibriu... A novel approach has been developed to determine the amount of residual water in human erythrocyte at room temperature by electronic particle counter. Nacl solutions of 13 osmolalities were prepared and the equilibrium cell volumes in which were measured one by one.The isotonic volume, V0, was obtained under the isotonic condition. The mean RBC volumes of 5 donors at each osmolality were fitted according to Boyle van’t Hoff relationship, and the osmotically inactive volume, Vb, of erythrocyte was then determined. The results show that Vb50% V0. More importantly, the final cell volume with regard to the solution of the highest concentration found to be kept at about 0.5 V0. The difference between these two volumes is unconspicuous. According to the published data that non-water volume of human erythrocyte is about 28.3% of its isotonic volume, residual water of human erythrocyte can be gained by subtracting V dry from Vf, that is V rw =21.7% V0. Then it was concluded that the residual water of human lays in 2 states, one is bound water, and the other is free water. 展开更多
关键词 EPC 红血球 残留水 血液循环
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A novel theoretical model for mass transfer of hollow fiber hemodialyzers 被引量:4
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作者 DINGWeiping HELiqun +3 位作者 ZHAOGang SHUZhiquan CHENGShuxia GAODayong 《Chinese Science Bulletin》 SCIE EI CAS 2003年第21期2386-2390,共5页
A novel theoretical model for mass transfer of hollow fiber bundles in hemodialyzers is presented. In the model, a hemodialyzer is considered as a porous zone which is composed of two non-interpenetrating porous flow ... A novel theoretical model for mass transfer of hollow fiber bundles in hemodialyzers is presented. In the model, a hemodialyzer is considered as a porous zone which is composed of two non-interpenetrating porous flow zones. Firstly, the dialysate side (shell side) is thought as a porous medium zone. Then by solidifying the dialysate flow zone and the occupied zone by hollow fiber membrane, the rest zone of hemodialyzer (i.e. blood side or lumen side) is con-sidered as a porous medium zone too. Finally, the interface of the two flow zones is the fiber membrane through which mass transfer is performed. The dialysate and blood flows are all described by Navier-Stokes equations with Darcy momentum source terms. Kedem-Katchalsky equations as other source terms are added into Navier-Stokes equations to simulate the permeating flux through the membrane. All equations must be coupled together in the process of com-puting. The model is validated by the experimental data in literature. The simulative results show that the predicted clearances agree well with the experimental data, and the model in this paper is better than other models for the fore-cast of clearance. 展开更多
关键词 血液透析器 中空纤维膜 转移系数 NAVIER-STOKES方程
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Nanotube photovoltaic configuration for enhancement of carrier generation and collection 被引量:1
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作者 Hongmei Dang Vijay P. Singh Sai Guduru Suresh Rajaputra Zhi David Chen 《Nano Research》 SCIE EI CAS CSCD 2015年第10期3186-3196,共11页
我们通过阳极的铝氧化物的申请在透明底层上在几何特征的生长上报导调节半导体 nanotubes 帮助膜的方法。三维的 nanotube 太阳能电池在在哪个半导体,吸收器是被开发不仅过去常充满 nanotubes 的内部核心,而且代替膜并且充满在 nanotu... 我们通过阳极的铝氧化物的申请在透明底层上在几何特征的生长上报导调节半导体 nanotubes 帮助膜的方法。三维的 nanotube 太阳能电池在在哪个半导体,吸收器是被开发不仅过去常充满 nanotubes 的内部核心,而且代替膜并且充满在 nanotubes 之间的 intertube 空间。nanotube 太阳能电池也就是,在 nanotubes 的核心内在三种尺寸产生并且分开搬运人在在沿着光线的方向的 nanotubes 之间的 intertube 空间,并且在沿着轴的方向的 nanotubes 上面。在进行表明这条途径的潜力的初步的实验, nanotube CdS-CdTe 太阳能电池被制作。分别地,有一条内部直径,墙厚度和 35, 20,和 35 nm 的 intertube 间距的 CdS nanotubes 被种;孔和 CdS nanotube 密度是 36.5% 和 2. 展开更多
关键词 载流子收集 碳纳米管 CDTE太阳电池 太阳能电池 纳米CDS 半导体材料 结构 光伏
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加入WTO对中国农产品进入美国市场的影响
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作者 张桂林 MichaelReed +1 位作者 MaryA.Marchant 宋宝辉 《China & World Economy》 SCIE 2004年第4期66-78,共13页
Agricultural trade between the U.S. and China is very important for both countries. Focusing on the potential of China's agricultural products entering the U.S. markets, this research introduced the development of... Agricultural trade between the U.S. and China is very important for both countries. Focusing on the potential of China's agricultural products entering the U.S. markets, this research introduced the development of agricultural trade between the U.S. and China and analyzed the impacts of the U.S.-China bilateral trade agreement and China's WTO membership on agricultural trade between the two countries. The authors also examined current and potential competitiveness of China's agricultural products and provided suggestions to increase China's agricultural exports to the United States. 展开更多
关键词 WTO 中国 农产品 美国市场 国际贸易 世界贸易组织
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