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U型渠道移动式流线型量水槽扩散段水力特性及结构优化方法
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作者 王玉宝 周仁宇 +1 位作者 张晨昊 李鑫 《农业工程学报》 EI CAS CSCD 北大核心 2024年第11期128-138,共11页
移动式量水槽较固定式具有不易淤积、可移动多处重复使用等优点,流线型外形的量水槽水力性能好,量水槽的扩散段对水力性能影响大,然而当前还缺乏扩散段的设计原理与方法方面的研究。为了研究量水槽结构型式对水力特性的影响,为流线型量... 移动式量水槽较固定式具有不易淤积、可移动多处重复使用等优点,流线型外形的量水槽水力性能好,量水槽的扩散段对水力性能影响大,然而当前还缺乏扩散段的设计原理与方法方面的研究。为了研究量水槽结构型式对水力特性的影响,为流线型量水槽结构设计提供理论指导,该研究建立D40U型渠道模拟模型,其后用FLOW-3D对35、45和55 L/s流量下的半椭圆+半椭圆、半椭圆+抛物线、半椭圆+圆弧、半椭圆+Myring曲线和鱼形量水槽进行模拟,结合原型试验验证数值模拟效果,探讨扩散段设计原则与方法。最后基于isight平台对水力性能较好的半椭圆+Myring曲线和鱼形量水槽进行结构优化。结果表明,45 L/s流量下不同进水口距离下水深数值模拟与试验值相对误差为0.1%~1.3%,上游、喉口和下游断面流速相对误差分别为0.19%~6.63%、0.06%~6.15%和0.02%~6.22%,模拟结果精度高。5种量水槽上游佛汝德数均小于0.5,最大壅水高度为5.71 cm,均满足测流精度和渠道安全要求。其中,半椭圆+Myring曲线量水槽水头损失和壅水高度最低,半椭圆+半椭圆量水槽临界淹没度最高,佛汝德数最小。量水槽扩散段设计原则为:在略微减少临界淹没度的条件下,扩散段前半段设计为曲率较大的曲线,以降低上游壅水高度;后半段设计为曲率相反且曲率较小的曲线,以改善过流流态,平顺水流,降低水头损失。优化后的半椭圆+Myring曲线和鱼形前半段曲率增大,后半段曲率减小,壅水高度和佛汝德数均有所降低,水头损失分别降低5.5%和6.3%,优化后曲线线型满足扩散段设计原则。研究可为流线型量水槽结构设计与优化提供理论指导。 展开更多
关键词 渠道 优化 设计 数值模拟 水力性能 扩散段
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培育农业科技推广中介组织的路径探讨 被引量:9
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作者 范秀荣 马晓旭 《西北农林科技大学学报(社会科学版)》 2002年第5期36-39,共4页
农技推广组织缺位 ,实施主体单一等问题 ,严重影响了农业科技成果向生产力的转化 ,造成资源的巨大浪费。要彻底解决上述问题 ,我国必须尽快建立一个以市场为导向 ,以效益为核心 ,以政府为主体的多元化农技推广组织体系。具体为 :确立政... 农技推广组织缺位 ,实施主体单一等问题 ,严重影响了农业科技成果向生产力的转化 ,造成资源的巨大浪费。要彻底解决上述问题 ,我国必须尽快建立一个以市场为导向 ,以效益为核心 ,以政府为主体的多元化农技推广组织体系。具体为 :确立政府在农技推广体系中的主体地位 ;充分利用农业高等院校的智力资源和人力资源 ;建立一支以公司、企业为骨干的农业科技产业化队伍 ; 展开更多
关键词 农业 科技推广 中介组织 中国 农业产业化 农业高等院校
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Re-identifying beef cattle using improved AlignedReID++
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作者 YING Xiaoyi ZHAO Jizheng +7 位作者 YANG Lingling ZHOU Xinyi WANG Lei GAO Yannian ZAN Linsen YANG Wucai LIU Han SONG Huaibo 《农业工程学报》 EI CAS CSCD 北大核心 2024年第18期132-146,共15页
Accurate and continuous identification of individual cattle is crucial to precision farming in recent years.It is also the prerequisite to monitor the individual feed intake and feeding time of beef cattle at medium t... Accurate and continuous identification of individual cattle is crucial to precision farming in recent years.It is also the prerequisite to monitor the individual feed intake and feeding time of beef cattle at medium to long distances over different cameras.However,beef cattle can tend to frequently move and change their feeding position during feeding.Furthermore,the great variations in their head direction and complex environments(light,occlusion,and background)can also lead to some difficulties in the recognition,particularly for the bio-similarities among individual cattle.Among them,AlignedReID++model is characterized by both global and local information for image matching.In particular,the dynamically matching local information(DMLI)algorithm has been introduced into the local branch to automatically align the horizontal local information.In this research,the AlignedReID++model was utilized and improved to achieve the better performance in cattle re-identification(ReID).Initially,triplet attention(TA)modules were integrated into the BottleNecks of ResNet50 Backbone.The feature extraction was then enhanced through cross-dimensional interactions with the minimal computational overhead.Since the TA modules in AlignedReID++baseline model increased the model size and floating point operations(FLOPs)by 0.005 M and 0.05 G,the rank-1 accuracy and mean average precision(mAP)were improved by 1.0 percentage points and 2.94 percentage points,respectively.Specifically,the rank-1 accuracies were outperformed by 0.86 percentage points and 0.12 percentage points,respectively,compared with the convolution block attention module(CBAM)and efficient channel attention(ECA)modules,although 0.94 percentage points were lower than that of squeeze-and-excitation(SE)modules.The mAP metric values were exceeded by 0.22,0.86 and 0.12 percentage points,respectively,compared with the SE,CBAM,and ECA modules.Additionally,the Cross-Entropy Loss function was replaced with the CosFace Loss function in the global branch of baseline model.CosFace Loss and Hard Triplet Loss were jointly employed to train the baseline model for the better identification on the similar individuals.AlignedReID++with CosFace Loss was outperformed the baseline model by 0.24 and 0.92 percentage points in the rank-1 accuracy and mAP,respectively,whereas,AlignedReID++with ArcFace Loss was exceeded by 0.36 and 0.56 percentage points,respectively.The improved model with the TA modules and CosFace Loss was achieved in a rank-1 accuracy of 94.42%,rank-5 accuracy of 98.78%,rank-10 accuracy of 99.34%,mAP of 63.90%,FLOPs of 5.45 G,frames per second(FPS)of 5.64,and model size of 23.78 M.The rank-1 accuracies were exceeded by 1.84,4.72,0.76 and 5.36 percentage points,respectively,compared with the baseline model,part-based convolutional baseline(PCB),multiple granularity network(MGN),and relation-aware global attention(RGA),while the mAP metrics were surpassed 6.42,5.86,4.30 and 7.38 percentage points,respectively.Meanwhile,the rank-1 accuracy was 0.98 percentage points lower than TransReID,but the mAP metric was exceeded by 3.90 percentage points.Moreover,the FLOPs of improved model were only 0.05 G larger than that of baseline model,while smaller than those of PCB,MGN,RGA,and TransReID by 0.68,6.51,25.4,and 16.55 G,respectively.The model size of improved model was 23.78 M,which was smaller than those of the baseline model,PCB,MGN,RGA,and TransReID by 0.03,2.33,45.06,14.53 and 62.85 M,respectively.The inference speed of improved model on a CPU was lower than those of PCB,MGN,and baseline model,but higher than TransReID and RGA.The t-SNE feature embedding visualization demonstrated that the global and local features were achieve in the better intra-class compactness and inter-class variability.Therefore,the improved model can be expected to effectively re-identify the beef cattle in natural environments of breeding farm,in order to monitor the individual feed intake and feeding time. 展开更多
关键词 method IDENTIFY beef cattle precision livestock re-identification AlignedReID++ deep learning
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Effect of Apis mellifera on community composition of local pollinator bees and their pollination network in Qinling Mountains and surrounding areas
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作者 Cheng'en ZHONG Qingle XIE +1 位作者 Yaoyao SI Yalin ZHANG 《Entomotaxonomia》 CSCD 2024年第3期167-205,共39页
The Qinling Mountains, known for their rich vegetation and diverse pollinating insects, have seen a significant decline in bee species richness and abundance over recent decades, largely due to the introduction and sp... The Qinling Mountains, known for their rich vegetation and diverse pollinating insects, have seen a significant decline in bee species richness and abundance over recent decades, largely due to the introduction and spread of Apis mellifera. This decline has caused cascading effects on the region's community structure and ecosystem stability. To improve the protection of native bees in the natural and agricultural landscape of the Qinling Mountains and its surrounding areas, we investigated 33 sampling sites within three habitats: forest, forest-agriculture ecotones, and farmland. Using a generalized linear mixing model, t-test, and other data analysis methods, we explored the impact of Apis mellifera on local pollinator bee richness, abundance, and the pollination network in different habitats in these regional areas. The results show that(1)Apis mellifera significantly negatively affects the abundance and richness of wild pollinator bees,while Apis cerana abundance is also affected by beekeeping conditions.(2)There are significant negative effects of Apis mellifera on the community structure of pollinator bees in the Qinling Mountains and its surrounding areas: the Shannon-Wiener diversity index, Pielou evenness index, and Margalef richness index of bee communities at sites with Apis mellifera influence were significantly lower than those at sites without Apis mellifera influence.(3)The underlying driver of this effect is the monopolization of flowering resources by Apis mellifera. This species tends to visit flowering plants with large nectar sources, which constitute a significant portion of the local plant community. By maintaining a dominant role in the bee-plant pollination network, Apis mellifera competitively displaces native pollinator bees, reducing their access to floral resources. This ultimately leads to a reduction in local bee-plant interactions, decreasing the complexity and stability of the pollination network. These findings highlight the need for targeted conservation efforts to protect native pollinator species and maintain the ecological balance in the Qinling Mountains. 展开更多
关键词 Apis mellifera Pollinator bees Species richness ABUNDANCE Interaction networks
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A review of Vietanna(Hemiptera:Cicadidae)with descriptions of two new species from China
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作者 Jiali WANG Lei FENG +1 位作者 Jinyuan JIANG Cong WEI 《Entomotaxonomia》 CSCD 2024年第3期228-240,共13页
The cicada genus Vietanna is reviewed based on the descriptions of two new species,V.perparva sp.nov.and V.longiloba sp.nov.,from China.The relationship of this genus to related taxa is discussed based on the phylogen... The cicada genus Vietanna is reviewed based on the descriptions of two new species,V.perparva sp.nov.and V.longiloba sp.nov.,from China.The relationship of this genus to related taxa is discussed based on the phylogeny of Vietanna and representative species from subtribes Puranina,Leptopsaltriina,Euterpnosiina and Leptosemiina based on the mitochondrial gene COI and nuclear genes EF-1αand ARD1. 展开更多
关键词 CICADOIDEA Cicadinae Leptopsaltrini revision PHYLOGENY
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Two new species in the bamboo-feeding genus Tiaobeinia(Hemiptera:Cicadellidae:Deltocephalinae)from China
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作者 Mengshu SHEN Wu DAI 《Entomotaxonomia》 CSCD 2024年第3期220-227,共8页
Two new species of Mukariini,Tiaobeinia coarseata sp.nov.from Shaanxi and Tiaobeinia yuani sp.nov.from Gansu,are described.Detailed morphological descriptions and illustrations of these new species are given.A checkli... Two new species of Mukariini,Tiaobeinia coarseata sp.nov.from Shaanxi and Tiaobeinia yuani sp.nov.from Gansu,are described.Detailed morphological descriptions and illustrations of these new species are given.A checklist of all known species in this tribe from China is provided and a key is proposed for all species of Tiaobeinia. 展开更多
关键词 AUCHENORRHYNCHA taxonomy key
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Vertical distribution characteristics of soil saturated hydraulic conductivity under different land use patterns in the Mu Us sandy land
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作者 LIU Xingting QIAO Jiangbo +4 位作者 YANG Tao MA Yali TIAN Hanyang HAN Xiaoyang ZHU Yuanjun 《地球环境学报》 CSCD 2024年第4期665-674,共10页
Background,aim,and scope Soil saturated hydraulic conductivity(K_(s))is a key parameter in the hydrological cycle of soil;however,we have very limited understanding of K_(s) characteristics and the factors that inf lu... Background,aim,and scope Soil saturated hydraulic conductivity(K_(s))is a key parameter in the hydrological cycle of soil;however,we have very limited understanding of K_(s) characteristics and the factors that inf luence this key parameter in the Mu Us sandy land(MUSL).Quantifying the impact of changes in land use in the Mu Us sandy land on K_(s) will provide a key foundation for understanding the regional water cycle,but will also provide a scientific basis for the governance of the MUSL.Materials and methods In this study,we determined K_(s) and the basic physical and chemical properties of soil(i.e.,organic matter,bulk density,and soil particle composition)within the first 100 cm layer of four different land use patterns(farmland,tree,shrub,and grassland)in the MUSL.The vertical variation of K_(s) and the factors that influence this key parameter were analyzed and a transfer function for estimating K_(s) was established based on a multiple stepwise regression model.Results The K_(s) of farmland,tree,and shrub increased gradually with soil depth while that of grassland remained unchanged.The K_(s) of the four patterns of land use were moderately variable;mean K_(s)values were ranked as follows:grassland(1.38 mm·min^(-1))<tree(1.76 mm·min^(-1))<farmland(1.82 mm·min^(-1))<shrub(3.30 mm·min^(-1)).The correlation between K_(s) and organic matter,bulk density,and soil particle composition,varied across different land use patterns.A multiple stepwise regression model showed that silt,coarse sand,bulk density,and organic matter,were key predictive factors for the K_(s) of farmland,tree,shrub,and grassland,in the MUSL.Discussion The vertical distribution trend for K_(s) in farmland is known to be predominantly influenced by cultivation,fertilization,and other factors.The general aim is to improve the water-holding capacity of shallow soil on farmland(0-30 cm in depth)to conserve water and nutrients;research has shown that the K_(s) of farmland increases with soil depth.The root growth of tree and shrub in sandy land exerts mechanical force on the soil due to biophysical processes involving rhizospheres,thus leading to a significant change in K_(s).We found that shallow high-density fine roots increased the volume of soil pores and eliminated large pores,thus resulting in a reduction in shallow K_(s).Therefore,the K_(s) of tree and shrub increased with soil depth.Analysis also showed that the K_(s) of grassland did not change significantly and exhibited the lowest mean value when compared to other land use patterns.This finding was predominantly due to the shallow root system of grasslands and because this land use pattern is not subject to human activities such as cultivation and fertilization;consequently,there was no significant change in K_(s) with depth;grassland also had the lowest mean K_(s).We also established a transfer function for K_(s) for different land use patterns in the MUSL.However,the predictive factors for K_(s) in different land use patterns are known to be affected by soil cultivation methods,vegetation restoration modes,the distribution of soil moisture,and other factors,thus resulting in key differences.Therefore,when using the transfer function to predict K_(s) in other areas,it will be necessary to perform parameter calibration and further verification.Conclusions In the MUSL,the K_(s) of farmland,tree,and shrub gradually increased with soil depth;however,the K_(s) of grassland showed no significant variation in terms of vertical distribution.The mean K_(s) values of different land use patterns were ranked as follows:shrub>farmland>tree>grassland;all land use patterns showed moderate levels of variability.The K_(s) for different land use patterns exhibited differing degrees of correlation with soil physical and chemical properties;of these,clay,silt,sand,bulk density,and organic matter,were identified as important variables for predicting K_(s) in farmland,tree,shrub,and grassland,respectively.Recommendations and perspectives In this study,we used a stepwise multiple regression model to establish a transfer function prediction model for K_(s) for different land use patterns;this model possessed high estimation accuracy.The ability to predict K_(s) in the MUSL is very important in terms of the conservation of water and nutrients. 展开更多
关键词 Mu Us sandy land saturated hydraulic conductivity vertical distribution transfer function
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不同碎石含量及直径对土壤水分入渗过程的影响 被引量:69
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作者 周蓓蓓 邵明安 《土壤学报》 CAS CSCD 北大核心 2007年第5期801-807,共7页
由于成土原因或人类活动,一些土壤中含有不同含量及大小的碎石。碎石的存在改变了土壤的某些物理特性,入渗过程也因此受到影响。本研究采用定水头入渗试验装置,对7种不同碎石含量(0%,10%,20%,30%,40%,50%,60%)及4种... 由于成土原因或人类活动,一些土壤中含有不同含量及大小的碎石。碎石的存在改变了土壤的某些物理特性,入渗过程也因此受到影响。本研究采用定水头入渗试验装置,对7种不同碎石含量(0%,10%,20%,30%,40%,50%,60%)及4种不同碎石直径(0.2~0.5cm,0.5~1.0cm,1.0~3.0cm,3.0~4.0cm)的土壤水分入渗过程进行室内研究,旨在分析碎石含量及直径对土壤入渗过程的影响及其原因,为土石混合介质的研究提供一些理论基础。 展开更多
关键词 累积入渗量 湿润峰 碎石含量 碎石直径
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中国大中城市生猪大规模养殖模式的成本效率分析 被引量:13
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作者 宁攸凉 乔娟 王征兵 《技术经济》 2010年第2期81-84,97,共5页
本文利用2002—2008年《全国农产品成本收益资料汇编》中有关大中城市生猪大规模养殖模式的成本收益数据,采用DEA方法测算与分析了中国大中城市生猪大规模养殖模式的成本效率(包括技术效率与配置效率)。得到如下结论:我国大中城市生猪... 本文利用2002—2008年《全国农产品成本收益资料汇编》中有关大中城市生猪大规模养殖模式的成本收益数据,采用DEA方法测算与分析了中国大中城市生猪大规模养殖模式的成本效率(包括技术效率与配置效率)。得到如下结论:我国大中城市生猪大规模养殖模式的成本效率的改进可以通过提高技术效率与配置效率实现;2001—2007年我国大中城市生猪大规模养殖模式的技术效率与配置效率都较高,且有不断提高的趋势;2001—2007年我国大中城市生猪大规模养殖模式的配置效率总体上低于技术效率。 展开更多
关键词 生猪大规模养殖模式 DEA 成本效率 技术效率 配置效率
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热处理对牛、羊、猪肉肌内脂肪过氧化程度影响 被引量:7
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作者 田万强 刘永锋 +2 位作者 李林强 梅楚刚 昝林森 《家畜生态学报》 北大核心 2016年第3期34-38,共5页
为分析不同热处理方式对动物肌肉脂肪过氧化程度的影响,采用硫代巴比妥酸比色法测定热处理后3种肉肌内脂肪过氧化反应终产物丙二醛生成量,气相色谱-质谱联用法、索氏抽提法测定其肌间脂肪的脂肪酸组成和肌内脂肪含量,并用扫描电镜观察3... 为分析不同热处理方式对动物肌肉脂肪过氧化程度的影响,采用硫代巴比妥酸比色法测定热处理后3种肉肌内脂肪过氧化反应终产物丙二醛生成量,气相色谱-质谱联用法、索氏抽提法测定其肌间脂肪的脂肪酸组成和肌内脂肪含量,并用扫描电镜观察3种肉的肌纤维形貌研究炒、蒸、烤三种不同热处理方式对牛、羊、猪肉肌内脂肪过氧化程度的影响。结果表明:炒制后羊肉肌内脂肪中MDA含量显著高于牛、猪肉(P<0.05),蒸煮后牛、羊肉肌内脂肪中MDA含量高于猪肉(P<0.05),烤制后牛肉肌内脂肪中MDA含量显著高于羊、猪肉(P<0.05);牛、羊、猪肉肌内饱和脂肪酸(SFA)相对含量依次为52.60、38.49、39.81g/100g;单不饱和脂肪酸(MUFA)含量依次为56.61、54.63、44.73g/100g;多不饱和脂肪酸依次为2.70、4.90、5.56g/100g;猪肉肌内脂肪含量(30.03g/100g)显著高于牛、羊肉(P<0.05),羊肉肌内脂肪含量(20.48g/100g)显著高于牛肉(8.31g/100g)(P<0.05);牛和羊肌纤维排列方向一致,结构紧密,猪肌纤维排列结构则较为松散。热处理温度是影响脂质过氧化程度大小的主要因素,肌纤维排列结构影响肌内脂肪过氧化产物MDA的含量。 展开更多
关键词 牛肉 羊肉 猪肉 热处理 脂肪过氧化
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沙棘果渣中异鼠李素和槲皮素的提取与分离 被引量:9
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作者 马养民 姜少娟 史清华 《西北林学院学报》 CSCD 北大核心 2009年第5期121-124,共4页
以沙棘果渣为原料从中提取分离出异鼠李素和槲皮素2个黄酮类化合物,实现了沙棘废料的利用。利用超声辅助方法进行总黄酮的提取,采用柱层析方法以及重结晶技术进行纯品化合物的分离纯化,借助紫外光谱、核磁共振谱以及红外光谱进行分析鉴... 以沙棘果渣为原料从中提取分离出异鼠李素和槲皮素2个黄酮类化合物,实现了沙棘废料的利用。利用超声辅助方法进行总黄酮的提取,采用柱层析方法以及重结晶技术进行纯品化合物的分离纯化,借助紫外光谱、核磁共振谱以及红外光谱进行分析鉴定。结果显示,沙棘果渣中的黄酮类化合物主要为异鼠李素和槲皮素,其中异鼠李素得率为0.55%。 展开更多
关键词 沙棘果渣 异鼠李素 槲皮素 分离 结构鉴定
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两种黄瓜接穗在同一砧木上对生长状况影响的研究 被引量:2
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作者 孙艳 冯贵颖 黄炜 《西北植物学报》 CAS CSCD 2002年第1期163-167,共5页
试验以黑籽南瓜为砧木 ,津优 1号和农城 4号为接穗的 2种嫁接苗的生长状况进行了比较研究。结果表明 :2种嫁接苗 A- CK1和 A- CK2 ,其最大侧根长的平均增长率分别为87.42 %和 47.1 3 % ;根系重量分别增加 77.89%和 6 7.5 1 % ;茎粗分别... 试验以黑籽南瓜为砧木 ,津优 1号和农城 4号为接穗的 2种嫁接苗的生长状况进行了比较研究。结果表明 :2种嫁接苗 A- CK1和 A- CK2 ,其最大侧根长的平均增长率分别为87.42 %和 47.1 3 % ;根系重量分别增加 77.89%和 6 7.5 1 % ;茎粗分别增加 2 1 .90 %和1 4.2 5 % ;壮苗指数分别增加 83 .0 8%和 78.83 % ;根 /冠比 A- CK1增加 45 .77% ,A- CK2 展开更多
关键词 黄瓜 接穗 嫁接苗 生长
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黄土状盐渍土的工程特点及地基处理方法 被引量:6
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作者 范恩让 张炜 +1 位作者 李凯 费秉胜 《岩土工程技术》 2001年第1期27-30,共4页
黄土状盐渍土在西北地区诸省均有分布。通过工程实例分析 ,论述了黄土状盐渍土的工程特点 ,指出了在西部大开发过程中对黄土状盐渍土的勘察设计应该注意的问题 。
关键词 黄土状盐渍土 湿陷性 灰土垫层 强夯加固
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论西部大开发中林业生态环境保护和建设 被引量:2
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作者 张秋良 李卫忠 莎如拉 《内蒙古农业大学学报(自然科学版)》 CAS 2001年第2期113-116,共4页
生态环境保护和建设是实施西部大开发战略的一个重大课题 ,是发展和繁荣西部地区经济的基础和重点。本文分析了严重制约西部地区经济 ,社会发展的生态环境问题 ,以及林业在生态环境建设中的地位和作用。提出加快西部地区林业生态环境保... 生态环境保护和建设是实施西部大开发战略的一个重大课题 ,是发展和繁荣西部地区经济的基础和重点。本文分析了严重制约西部地区经济 ,社会发展的生态环境问题 ,以及林业在生态环境建设中的地位和作用。提出加快西部地区林业生态环境保护和建设的关键是 :林业生态环境建设的布局和规划 ;现有林的管护和经营 ;退耕还林 ,还草 ;林业生态工程建设 ;科技和经费的投入等对策和建议。 展开更多
关键词 西部大开发 林业生态环境建设 生态环境保护
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益生菌对雏鸡生长性能和胴体品质的影响 被引量:12
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作者 楚渠 龚月生 +1 位作者 马红艳 赵振涛 《四川畜牧兽医》 2004年第1期27-27,共1页
本试验选用108只商品代蛋鸡公雏,分成三组,每组三个重复,每个重复12只。三组分别设为对照组、添加0.2%益生菌组、添加50mg/kg土霉素组,试验期为28d。结果表明:与对照组相比,益生菌组鸡只增重提高6.59%,料重比改善6.45%,全净膛率提高3.82%。
关键词 益生菌 雏鸡 生长性能 胴体品质 影响因素
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绿原酸的提取与分离——现代分离技术实验课程教学内容改革初探
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作者 汪玉秀 王俊儒 +2 位作者 常君成 来冬梅 高锦明 《教育教学论坛》 2014年第6期241-242,共2页
根据现代分离技术课程的特点,选择任课教师科研课题中与现代分离技术密切相关的内容:金银花中绿原酸的提取与分离,将原本孤立的分离技术基础实验改为综合性实验,其内容涉及固体中有效成分的提取技术、减压浓缩技术、紫外检测技术以及硅... 根据现代分离技术课程的特点,选择任课教师科研课题中与现代分离技术密切相关的内容:金银花中绿原酸的提取与分离,将原本孤立的分离技术基础实验改为综合性实验,其内容涉及固体中有效成分的提取技术、减压浓缩技术、紫外检测技术以及硅胶吸附柱层析、硅胶吸附薄层层析和高效液相色谱等现代分离技术。使学生在系统地掌握实验技能的同时,亲身体验了现代分离技术在天然产物研究中的重要作用。 展开更多
关键词 提取 分离 现代分离技术 实验课程
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黄土丘陵区植被恢复对深层土壤有机碳的影响 被引量:40
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作者 王征 刘国彬 许明祥 《生态学报》 CAS CSCD 北大核心 2010年第14期3947-3952,共6页
以恢复9、15、24a和34a的刺槐林为研究对象,探究黄土丘陵区深层土壤有机碳(SOC)积累以及对植被恢复的响应。区域深层土壤(50-200cm)SOC含量高达1.35-2.39g·kg-1,约为浅层土壤(0-50cm)SOC含量的25%;深层土壤SOC储量高达26.28-46.50t... 以恢复9、15、24a和34a的刺槐林为研究对象,探究黄土丘陵区深层土壤有机碳(SOC)积累以及对植被恢复的响应。区域深层土壤(50-200cm)SOC含量高达1.35-2.39g·kg-1,约为浅层土壤(0-50cm)SOC含量的25%;深层土壤SOC储量高达26.28-46.50t.hm-2,占2m土层SOC储量的50%以上,显著高于浅层SOC储量;植被恢复20多年后与恢复9a相比,深层SOC含量和储量都有极显著提高。2m土层SOC含量随植被恢复20多年后较9a提高1倍左右;2m土层SOC储量增幅为43.02.thm-2(9-34a),明显高于1m土层SOC储量增幅34.65t.hm-2(9-34a)。浅层土壤中的0-30cm相邻土层间SOC含量差异显著,而深层SOC含量较稳定。深层SOC含量与刺槐盖度、基径、高度呈极显著正相关。在评价黄土丘陵区植被恢复的土壤固碳效应时应充分考虑深层土壤有机碳储量和变化。 展开更多
关键词 植被恢复 土壤有机碳 深层土壤 刺槐 黄土丘陵区
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硒对山羊细胞免疫功能的影响 被引量:2
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作者 李引乾 王建华 +2 位作者 靳亚平 沈文正 马勇江 《西北农林科技大学学报(自然科学版)》 CSCD 北大核心 2008年第3期49-53,共5页
【目的】探讨硒对山羊细胞免疫功能的影响。【方法】12只试验羊随机分为4组,分别灌服0.3,0.5和0.7 mg/kg的硒以及1 mL/kg的蒸馏水,每周1次,连续3周,检测硒对山羊外周血单个核细胞(Peripheral bloodmononuclear cell,PBMC)的活化作用... 【目的】探讨硒对山羊细胞免疫功能的影响。【方法】12只试验羊随机分为4组,分别灌服0.3,0.5和0.7 mg/kg的硒以及1 mL/kg的蒸馏水,每周1次,连续3周,检测硒对山羊外周血单个核细胞(Peripheral bloodmononuclear cell,PBMC)的活化作用。无菌分离未服硒山羊PBMC,分别加入4,8,12和16μg/mL亚硒酸钠进行体外培养,检测硒在体外对PBMC的活化作用及其分泌IL-2的影响。【结果】山羊灌服0.7 mg/kg硒2周后及灌服0.5mg/kg硒3周后,其PBMC对PHA刺激的反应性显著提高。8-16μg/mL亚硒酸钠在体外培养中可显著促进山羊PBMC的活化,且呈剂量依赖关系,4μg/mL亚硒酸钠对PBMC的活化作用较弱,与对照组间差异不显著;山羊PB-MC体外培养时,加入8-12μg/mL亚硒酸钠可显著促进山羊PBMC的IL-2分泌,4和16μg/mL亚硒酸钠虽能诱导PBMC分泌IL-2,但与对照组差异不显著。【结论】山羊灌服一定量的硒,可显著提高其免疫细胞对抗原刺激的反应性。亚硒酸钠在一定质量浓度范围内可显著促进山羊PBMC的活化,且能促进其IL-2分泌。 展开更多
关键词 山羊 外周血单个核细胞(PBMC) 细胞免疫
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我国婴幼儿配方奶粉生产现状和发展趋势探讨 被引量:8
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作者 赵静 林清 +2 位作者 荣建琼 牛鹏飞 李林强 《中国牛业科学》 2016年第5期64-66,共3页
探讨我国婴幼儿配方奶粉生产现状和发展趋势。分析了婴幼儿配方奶粉的起源和发展、我国婴幼儿配方奶粉发展与现状。婴幼儿配方奶粉生产的规模化、配方科学性和可靠性将是其未来发展趋势。
关键词 婴幼儿配方奶粉 生产现状 发展趋势
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植物叶子枯萎变形虚拟方法研究 被引量:1
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作者 邢方山 何东健 《计算机工程》 CAS CSCD 北大核心 2011年第5期238-240,共3页
为真实表现叶子在枯萎过程中的形态变化,提出一种植物叶子枯萎造型方法。该方法采用图像处理技术提取叶子轮廓,用Runions的方法生成叶脉,基于叶子轮廓和生成的叶脉产生叶子的2D网络,在此基础上提出基于控制曲线控制网格来实现枯萎过程... 为真实表现叶子在枯萎过程中的形态变化,提出一种植物叶子枯萎造型方法。该方法采用图像处理技术提取叶子轮廓,用Runions的方法生成叶脉,基于叶子轮廓和生成的叶脉产生叶子的2D网络,在此基础上提出基于控制曲线控制网格来实现枯萎过程中的弯曲变形,并通过实验设计出控制曲线。实验结果表明,该方法能较好地模拟植物叶子枯萎过程中的形态变化。 展开更多
关键词 叶子 枯萎变形 虚拟 控制曲线
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