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71.
电子商务专业人才培养研究 总被引:4,自引:0,他引:4
本文论述了我国与国外电子商务专业人才培养情况 ,以及当前国内电子商务人才的需求状况 ,从而确立我国电子商务人才培养方向。 相似文献
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比较了不同类型虫袋和填充物对角倍春迁蚜产性蚜数量和存活率的影响,结果表明:采用柱状虫袋填充玉米苞皮及对玉米苞皮进行浸泡处理可以提高性蚜的数量和雌蚜/干母的存活数;与传统的三角纸袋填充棕丝相比较,柱状虫袋填充浸泡玉米苞皮的雌蚜数、雌蚜/干母存活数、雄蚜数和性蚜总数分别增加了107.6%、229.1%、71.1%和87.5%,雌蚜/干母存活率提高了21.1%。虫袋内的雌蚜数、雄蚜数和性蚜总数与春迁蚜数呈显著负相关;雌蚜数和雌蚜/干母存活数与雄蚜数、性蚜总数和雌雄性比分别呈极显著正相关。角倍产区的环境因子明显影响春迁蚜的羽化期,但对春迁蚜产性蚜的数量没有明显影响。 相似文献
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The plants of the genus Abies are dominant and key species in the dark coniferous forest in the Northern Hemisphere. There are 52 species, one subspecies
and 12 varieties in the genus Abies in the world. The history and modern distribution of Abies were discussed. The genus has three modern distribution centers: South Europe, North America and East Asia. These areas are
also rich in fossil records. The vertical distribution regions of Abies are from sea level to an elevation of 4,700 m, concentrated in 1,000–2,000 m (15 species). In China, the genus distributes
in 20 provinces, especially abundant in the Hengduan Mountains. Meanwhile, endemic and relic phenomena are obvious in this
genus. There are seven relic species with both limited individuals and limited distributed regions. Based on the fossil records
and the latest phylogenetic data, the following hypothesis was proposed: Abies originated from the middle and high altitudes of the Northern Hemisphere in the middle Cretaceous and it was dispersed southward
in the Eocene due to global climate cooling down. The distribution of Abies was deeply influenced by geological events such as the uplift of Himalaya, the Alps, the Rocky Mountains, the occurrence
of the Asian Monsoon as well as the Quaternary glaciers. Finally, the current distribution pattern appeared in the Quaternary.
The genus Abies has a fossil history and modern distribution pattern similar to that of Cathaya and Pseudolarix.
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Translated from Acta Botanica Yunnanica, 2006, 28(5): 439–452 [译自: 云南植物研究] 相似文献
77.
以酶解渣为碳源制备木聚糖酶的研究 总被引:3,自引:6,他引:3
以里氏木霉(Tichoderma reesei)Rut C-30为产酶菌,低聚木糖制备过程中酶解渣为碳源可透导产生含低纤维素酶活(0.106IU/mL)的木聚糖酶(154.67IU/mL),两种酶活的比值达1459,与粗木聚糖为碳源产木聚糖酶相比,木聚糖酶活提高了1.67倍,而纤维素酶活没有增加。此酶在50℃条件下酶解粗木聚糖和酶解渣时,pH值5时酶解效率最高,酶解产物通过HPLC分析,主要是木糖。该酶系的组成主要是外切-β-木糖苷酶。 相似文献
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Zhang Gong; Zeng Guang-Ming; Du Chun-Yan; Jiang Yi-Min; Su Xiao-Kang; Xiang Ren-Jun; Huang Lu; Xu Min; Zhang Chang 《Forestry》2007,80(2):211-221
The chemistry and deposition pattern in bulk precipitation andthroughfall (TF) were examined and evaluated based on the 3-yearobservations in Shaoshan subtropical deciduous-conifer mixedforest in central-south China. The TF chemistry was notablychanged when passing through canopies, which probably was attributedto the dry deposition (DD) on leaf surface and the canopy exchanges.Base cations' (Ca2+, Mg2+ and K+) fluxes were significantlyenriched in TF, in particular for K+. The annual K+ canopy exchangewas 12 times larger than DD, and canopy exchange of Ca2+, Mg2+and K+ was four times as high as the DD. The canopy exchangeof base cations in association with weak acid accounted for28.4 per cent of total leached base cations, which was one ofthe important factors to modify the TF chemistry. 相似文献
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