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农业生态经济系统分区方法研究——以四川盆周山区为例 总被引：1，自引：0，他引：1
郭守前 《四川农业大学学报》1997,(3)
农业生态经济系统分区，涉及到自然、生态、经济、社会等多方面因素，边界具有很强的模糊性。运用模糊聚类方法与判别分析相结合，既能适应上述特点，又有效解决了独立样本的合理归类问题。利用主分量分析选取聚类指标，并以各指标对主分量的负荷和作用为依据确定其聚类时的权重。 相似文献
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通过定位试验，分析了四川盆地马尾松低效防护林系统改造恢复６年后群落学及土壤理化性质的效应变化，探讨了改造措施对马尾松低效防护林效应的影响。 相似文献
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分别就农村金融组织体系中的商业性金融、政策性金融、农村信用合作社和农业保险等同改革与完善提出相应的对策,以发挥农村金融体系的整体作用支持农业和农村经济的发展。 相似文献
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《Southern Forests》2013,75(2):125-132
The spotted gum species complex represents a group of four eucalypt hardwood taxa that have a native range that spans the east coast of Australia, with a morphological cline from Victoria to northern Queensland. Of this group, Corymbia citriodora subsp. variegata (CCV) is widespread in south-eastern Queensland and northern New South Wales. It is currently the most commonly harvested native hardwood in Queensland. However, little basic knowledge of the reproductive biology of the species is available to inform genetic improvement and resource management programmes. Here we take an integrative approach, using both field and molecular data, to identify ecological factors important to mating patterns in native populations of CCV. Field observation of pollinator visitation and flowering phenology of 20 trees showed that foraging behaviour of pollinator guilds varies depending on flowering phenology and canopy structure. A positive effect of tree mean flowering effort was found on insect visitation, while bat visitation was predicted by tree height and by the number of trees simultaneously bearing flowers. Moreover, introduced honeybees were observed frequently, performing 73% of detected flower visits. Conversely, nectar-feeding birds and mammals were observed sporadically with lorikeets and honeyeaters each contributing to 11% of visits. Fruit bats, represented solely by the grey-headed flying fox, performed less than 2% of visits. Genotyping at six microsatellite markers in 301 seeds from 17 families sampled from four of Queensland's native forests showed that CCV displays a mixed-mating system that is mostly outcrossing (t m = 0.899 ± 0.021). Preferential effective pollination from near-neighbours was detected by means of maximum-likelihood paternity analysis with up to 16% of reproduction events resulting from selfing. Forty to 48% of fertilising pollen was also carried from longer distance (>60 m). Marked differences in foraging behaviour and visitation frequency between observed pollinator guilds suggests that the observed dichotomy of effective pollen movement in spotted gums may be due to frequent visit from introduced honeybees favouring geitonogamy and sporadic visits from honeyeaters and fruit bats resulting in potential long-distance pollinations. 相似文献
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本文以沐川县森林经营所柳杉、杉木人工林的材积生长率调查资料为例,分别用7个龄阶的材积生长率数据,建立材积生长率计算的GM(1,1)模型,用以模拟并预测材积生长率,获得了满意的预测效果,不仅预测的精度高,而且符合林木生长规律。在林业生产实践中,用灰色系统模型预测人工林材积生长率有其适用价值。 相似文献
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本试验采用了三元杂交配套模式（即M♂×J♀→MJ♀×F♂→GMJ），以亲本M、J为对照，测定了单杂交母本MJ的繁殖性能，研究杂交鸭GMJ、GM、GJ和亲本G、M、J六个组合在放牧补饲和合饲方式下的肉用性能．结果表明：MJ40周产蛋量为203．7个，比J（147．2个）提高56．5个，MJ为全年产蛋，无季节性．舍饲7周龄，GMJ重2726．5g．比J提高全净膛重34．5％，胸肌63．9％，腿肌23．0％．杂交显著提高了建白羽系的生长速度和产肉量，改变了J胸肌薄弱的缺点． 相似文献
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齐口裂腹鱼和重口裂腹鱼消化道形态和组织结构的观察 总被引：5，自引：2，他引：5
本文对齐口裂腹鱼和重口裂腹鱼消化道的大体形态及显微结构进行了观察和比较，并探讨了结构与食性的关系。两种鱼消化管分为口腔、咽、食道、肠等四个部分；消化道管壁除口腔、咽外均由粘膜、粘膜下层、肌层和浆膜构成；食道上皮均为复层扁平上皮；肠上皮主要由柱状细胞和杯状细胞组成，其间有嗜酸性颗粒细胞；杯状细胞的数量在前、中肠少，后肠增多；两种鱼在口腔、咽形态组织结构，肠长度和盘曲程度方面差异较大，与其食性密切相关。 相似文献
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邓跃宁 《四川农业大学学报》1994,(4)
职技师范专业是为职业中学培养专业课师资的一个新型专业。它不仅具有应用技术和师范的特征，而且还具有其自身的规律和特点。随着我国职教事业和市场经济的建立和发展，新的教学体系的建立势在必行。本文通过对农技师范专业的研究，提出了职技师范体育教学新体系的培养目标、规格、大纲教材等基本内容。 相似文献
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王宗尧 《四川农业大学学报》1988,(1)
本文是茶园不同种植规格及密度试验结果。种植规格和密度对于茶树个体与群体的生长发育关系极为密切。在栽培技术措施基本一致时,较为合理的种植规格和增加密度是实现茶园速成投产、高产稳产的关键措施。同时,茶园投产早迟和产量高低,直接关系到生产成本和经济效益的大小。 相似文献