共查询到20条相似文献，搜索用时 15 毫秒
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Zimmerman DW 《Science (New York, N.Y.)》1971,174(4011):818-819
Small mineral grains (10 to 50 micrometers) of high uranium concentration (100 to 3000 parts per million) were located in polished sections of eight potsherds from Cyprus, England, Greece, and Mexico by induced fission-track mapping. Most of the grains were identified as zircons or apatites by a microprobe attachment to a scanning electron microscope. The advantages in using such radioactive grains for thermoluminescence dating and alpha-recoil track dating are discussed. 相似文献
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Carrigy MA 《Science (New York, N.Y.)》1986,234(4783):1515-1518
Low world oil prices represent a serious threat to expanded commercial development of the Canadian oil sands in the near term, as they do to all of the higher cost alternatives to crude oil such as oil shales and coal liquefaction. Nonetheless, research and field testing of new technology for production of oil from oil sands are being pursued by industry and government in Alberta. New production technology is being developed in Canada to produce synthetic oil from the vast resources of bitumen trapped in the oil sands and bituminous carbonates of northern Alberta. This technology includes improved methods of mining, extraction, and upgrading of bitumen from near-surface deposits as well as new drilling and production techniques for thermal production of bitumen from the more deeply buried reservoirs. Of particular interest are the cluster drilling methods designed to reduce surface disturbance and the techniques for horizontal drilling of wells from underground tunnels to increase the contact of injection fluids with the reservoir. 相似文献
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通过赤霉素浸种和表土掺砂对结缕草成坪的影响试验表明,５ｍｇ／Ｌ 赤霉素浸种２ｄ 和３ｃｍ 表土内每平方米掺砂１０ｋｇ 能显著提高出苗数,但对坪苗质量影响不显著。 相似文献
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[目的]以王不留行中总黄酮得率为指标,确定王不留行的最佳炮制工艺。[方法]通过紫外分光光度法测定王不留行不同炮制品中总黄酮含量。[结果]王不留行不同炮制品中总黄酮含量由大到小为:油砂炒法>清炒法>中火酒炒法>润炒法>砂炒法。[结论]不同炮制方法对王不留行总黄酮成分的含量有着明显的影响,且油砂炒法为王不留行最佳炮制工艺。 相似文献
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福建沿海沙质地巨尾桉防护林生长效应 总被引：2，自引：0，他引：2
通过对沿海沙质地巨尾桉防护林的生长进程、造林效果及抗风性的研究表明:巨尾桉能够适应干旱瘠薄的沙质立地条件,生长迅速且抗风性较强,其早期速生的特性在沿海防护林造林更新中的应用可以达到快速成林、减少林地裸露时间的效果;巨尾桉对沿海沙质地的立地条件反应敏感、不同立地亚类型的林分生长量差异很大;良好的径高比、对大风环境的生态适应性及本身具有的深根性是福建沿海沙质地巨尾桉防护林抗风能力较强的主要原因. 相似文献
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主要研究不同栽培基质对不同品种风信子生长发育的影响。将紫皮风信子(Atlantic)和黄皮风信子(City ofhearlem)分别种植在混合有砂或蛭石的基质中。结果表明在含砂的基质中种植风信子,更有利于其发芽,能够延长其生长期,从而促进植株长高、鳞茎膨大和种球增殖。总之,混有砂的基质比蛭石代替砂的基质,对风信子的生长发育更有利。 相似文献
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罗辉勇 《福建农业大学学报(哲学社会科学版)》2008,(5):66-69
宽严相济的刑事政策作为一项基本的刑事政策,是建设和谐司法的重要指导思想。但目前对宽严相济刑事政策的理论研究多侧重于政策解读和制度建设,而在司法实务方面则又多从检、法职能出发,忽略了诉讼三大功能之一的辩护职能。本文从内涵界定、制度设计、功能冲突、职能缺失等方面分析了辩护职能实现宽严相济刑事政策时存在的障碍,并就如何在宽严相济刑事政策发挥辩护职能的作用提出制度保障、坚持的原则、司法理念、完善制度、加强协调等方面的对策。 相似文献
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[目的]测定并分析压砂甜瓜白粉病病原菌的18S rDNA序列。[方法]从宁夏中部干旱带压砂甜瓜主栽品种＂玉金香＂发病植株上分离白粉病病原菌,采用Chelex-100法从其分生孢子中提取基因组DNA,PCR扩增18S rDNA序列,测序后进行Blast分析比对,并构建系统发育树。[结果]18S rDNA序列分析表明压砂甜瓜白粉病病原菌属单囊壳属（Podosphaera）。[结论]为生物防治压砂甜瓜白粉病和抗白粉病育种研究提供了参考。 相似文献
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对浑善达克沙地进行野外考察和采集表层沙样,通过激光粒度仪测量其沙粒粒径,分析其内部不同区域沉积物粒度特征、空间分异规律和沉积环境,为治理该沙地提供理论依据。结果表明,浑善达克沙地内部不同区域表层沉积物粒度组成上有较大的差异,总体以细沙和中沙为主,平均含量分别为43.9%和34.72%;粉沙、极细沙、粗砂含量较少。中值粒径从西到东逐渐变细;分选系数为0.94Φ,分选性整体较差,沿盛行风向有变好的趋势;偏度和峰度均值分别为0.16和1.23。粒度频率曲线指示该沙地沉积环境多样,沉积过程复杂。中西部沙物质以河流及湖泊沉积为主;东部则主要分布风成沉积,其部分物质可能来源于沙地内部的河流碎屑物或更西部的河湖相沉积。 相似文献
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本文采用空间换时间的研究方法,对毛乌素沙地南缘流动沙地、半固定沙地、半固定沙地与固定沙地过渡带和固定沙地内的植物群落物种多样性进行了研究。结果表明：不同演替阶段沙地内植物群落多样性呈不断增加的变化趋势,各演替阶段均有不同的植物群落和优势物种。豆科和藜科植物作为流动沙地的先锋物种,表现出较强的适应能力;禾本科和菊科植物由流动沙地到固定沙地,其种类变化较大,表明其在沙地恢复中发挥着巨大的作用;萝摩科植物可作为区分流动沙地和其它沙地类型的指示性植物;马齿苋科和紫薇科植物仅在固定沙地中出现,已成为判断固定沙地的标志性植物。除沙地恢复过程中人为播种的柠条和沙蒿外,流动沙地阶段的优势物种是沙米,半固定阶段是沙生冰草,半固定沙地与固定沙地过渡地带是老瓜头和地梢瓜,而固定沙地则为花棒和地梢瓜。因此,在沙漠化治理中应根据不同的沙地类型选择不同的植物种类。 相似文献
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宿根福禄考嫩枝的扦插繁殖 总被引：1，自引：0，他引：1
选取宿根福禄考作为研究对象,对不同务件下宿根福禄考扦插苗的生根情况及生长势进行了比较,以确定扦插繁殖的最佳栽培条件。试验结果表明：以土为基质的扦插苗生根较早,早期生长较快,6月初之前为各组中长度最长的,但在6月后生长趋于平缓,蛭石和沙为基质各组在早期生长速度都较以土为基质的慢且速度基本相同;生根粉溶液浓度对扦插苗生长早期影响较大,尤其是以腐殖土 沙(3：1)为基质时,早期影响尤为明显,但在后期各种基质生根速率及生根长度趋于相同;生根粉溶液浓度对于存活率作用较为明显,以腐殖土 沙(3：1)为基质时,不使用生根粉的扦插苗存活率达到100%,使用生根粉的扦插苗不能达到这一效果,扦插苗存活率与使用生根粉溶液浓度成反比,以蛭石 沙(1：1)及沙为基质时,扦插苗存活率都较高,其中以蛭石 沙(1：1)为基质时,使用生根粉的扦插苗100%存活,不使用生根粉的扦插苗存活率只能达到57．14%,以沙为基质时,使用生根粉的扦插苗存活率几乎为100%,而不使用生根粉的扦插苗存活率只能达到64．29%。 相似文献
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XUJing-gang LIShu-qin SHANDe-xin 《东北农业大学学报(英文版)》2003,10(1):19-24
The objectives of this experiment were to evaluate the performance of different plant species growing in different kinds of oil sands fine tailings,and to estimate the uptake of organic contaminants by plants from the oil sands fine tailings. In general,total hydrocarbon in the plant could be ranked (beginning with the highest)as :unweathered plant 4 tailings (UWT),Freeze-Thawtailings(FT) ,weathered plant 4 tailings(WT),and consolidated tailings(CT) for the willow,poplar and cattails.For grass ,CT amended with tailings sand and muskeg had the highest hydrocarbon level in the field treatment ,however,other three kinds of tailings(FT,WT and UWT) had lower but similar to each other hydrocarbon levels. 相似文献
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Study of 18 Cenozoic South Pacific deep-sea cores indicates an association of glacially derived ice-rafted sands and relatively low planktonic foraminiferal diversity with cooling of the Southern Ocean during the Lower Eocene, upper Middle Eocene, and Oligocene. Increased species diversity and reduction or absence of ice-rafted sands in Lower and Middle Miocene cores indicate a warming trend that ended in the Upper Miocene. Antarctic continental glaciation appears to have prevailed throughout much of the Cenozoic. 相似文献
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Christensen PR Wyatt MB Glotch TD Rogers AD Anwar S Arvidson RE Bandfield JL Blaney DL Budney C Calvin WM Fallacaro A Fergason RL Gorelick N Graff TG Hamilton VE Hayes AG Johnson JR Knudson AT McSween HY Mehall GL Mehall LK Moersch JE Morris RV Smith MD Squyres SW Ruff SW Wolff MJ 《Science (New York, N.Y.)》2004,306(5702):1733-1739
The Miniature Thermal Emission Spectrometer (Mini-TES) on Opportunity investigated the mineral abundances and compositions of outcrops, rocks, and soils at Meridiani Planum. Coarse crystalline hematite and olivine-rich basaltic sands were observed as predicted from orbital TES spectroscopy. Outcrops of aqueous origin are composed of 15 to 35% by volume magnesium and calcium sulfates [a high-silica component modeled as a combination of glass, feldspar, and sheet silicates (approximately 20 to 30%)], and hematite; only minor jarosite is identified in Mini-TES spectra. Mini-TES spectra show only a hematite signature in the millimeter-sized spherules. Basaltic materials have more plagioclase than pyroxene, contain olivine, and are similar in inferred mineral composition to basalt mapped from orbit. Bounce rock is dominated by clinopyroxene and is close in inferred mineral composition to the basaltic martian meteorites. Bright wind streak material matches global dust. Waterlain rocks covered by unaltered basaltic sands suggest a change from an aqueous environment to one dominated by physical weathering. 相似文献
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为探讨干旱荒漠区白刺灌丛沙堆土壤粒度特征，以民勤不同演替阶段（发育、稳定、衰退、严重衰退）白刺灌丛沙堆为对象，分别采集0~100 cm土层土壤样本，测定土壤粒度组成，计算并分析粒度参数。结果表明:1）干旱荒漠区发育阶段白刺灌丛沙堆土壤以细砂（50.04%~57.10%）和中砂（16.05%~22.03%）为主，稳定、衰退、严重衰退演替阶段白刺灌丛沙堆土壤以细砂（46.71%~64.06%）和极细砂（17.14%~29.06%）为主。2）平均粒径介于极细砂、细砂和中砂（1.92~3.17ф），分选系数介于较好和较差之间（0.69~1.41），偏度负偏至正偏（-0.141~0.299），峰度中等至很尖锐（1.01~1.99），分形维数（1.665~2.242）。随着白刺灌丛沙堆的演替发展，平均粒径变细、细粒物质所占比重增大，分选系数从中等、较好-中等之间、较差、中等-较差，粒度频率曲线变窄。3）从垂直分布来看，4个演替阶段不同土层粒度参数差异不显著。在0~10 cm土层中，不同演替阶段白刺灌丛沙堆土壤粒度参数存在极显著差异（P＜0.01）。 相似文献
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本文研究了巴里坤湖初制卤虫卵深加工过程中泥沙、空壳等杂质与完整卵分离技术的４种途径。结果表明．最优途径为长时间高浓度盐水──淡水途径。 相似文献