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941.
论述了木材常规干燥各种控制方法的特点及应用,对比分析了各种控制方法间的联系与差异。  相似文献   
942.
据2006年森林资源二类调查数据,香格里拉县天然林面积计918594.2hm^2.乔木林分树种以冷杉、高山松为主,龄组以成过熟林为主.目前,对天然林的威胁因子主要有:森林火灾,森林病虫害,木材低价值消耗,畜牧业发展,生态旅游开发,矿产及水电资源开发.籍此提出对天然林的保护对策:提高林火监测和控制水平,加强病虫害监测和预防,加强自然保护区建设,增加林区群众经济收入等.  相似文献   
943.
三峡上游梯级水库蓄水发电后,三峡水库支流库湾水华情势有显著不同。为弄清新情势下影响三峡水库支流库湾水华的影响因素,于2015年对香溪河库湾开展了为期一年的跟踪监测研究。结果表明:叶绿素a浓度季节性变化显著,夏季最高,春秋季次之,冬季最低,全年平均值为14.38μg/L,变化范围为0.36μg/L ~108.00μg/L;春季,叶绿素a浓度与水温、pH、混合层深度表现为正相关,与浊度总氮、总氮溶解性硅、真光层深度表现为负相关;夏季,叶绿素a浓度与水温、pH、滞留时间、混合层深度表现正相关,而与总氮表现为负相关;秋季,叶绿素a浓度与水温、混合层深度表现正相关,与浊度、溶解性硅、真光层深度表现负相关;冬季,叶绿素a与溶解性硅表现为负相关,与其他环境因子具有一定的相关性,但相关性不显著。总氮、总磷和叶绿素a的浓度水平均指示香溪河水体处于富营养化状态。  相似文献   
944.
The study of the spatial distribution of soil organisms is one of the key research areas for understanding soil functioning. However, we still know little about the role of dispersal in the distribution of soil organisms such as earthworms. Critically, the relative strength of the external factors that trigger dispersal movements has not been documented. In this work, we test the relative importance of habitat quality and the cumulative use of habitat as drivers of dispersal of an anecic earthworm (Aporrectodea giardi) by observing their dispersal rates over 1, 2, 4, 8, 16 and 32 days. The results suggest that cumulative dispersal rates were higher and reached a maximum value more rapidly when individuals were introduced into unsuitable rather than suitable soil. This suggests that earthworm dispersal responded more rapidly and this response was more pronounced with respect to the cumulative use of the habitat. It seemed that there were two types of dispersal: one triggered quickly to escape unsuitable conditions and another in response to a cumulative use of the habitat.  相似文献   
945.
本文基于弹性薄壳理论提出分析任意边界条件下,环加筋壳体振动特性的改进方法,系统分析了环筋尺寸和数目变化及环筋偏心对环加筋壳体振动特性的影响。与有关文献的模型实验结果比较表明,本文方法是正确的。  相似文献   
946.
本文根据重庆市37年来粮食总产量的历史资料,分析了粮食总产量阶梯式上升的特点,运用系统理论对影响粮食总产增长的政策因素、技术因素、气候因素的作用机制和相互关系进行了深入研究,并用研完结论解释了重庆37年来,特别是近8年来的粮食总产变动过程。  相似文献   
947.
采用了横跨长白山10个林场的171块标准地材料。每块标准地共调查了11个立地条件因子。通过主成分分析,典型相关分析和相关分析研究了长白山区不同立地因子之间的复杂关系。为主导立地因子的应用奠定了基础。论述了应用主导立地因子的理论性和正确性。通过多元线性回归和偏相关系数的检验找出了影响落叶松、红松和樟子松三个树种生长的主导立地因子,并用其进一步说明了长白山在主导立地因子应用方面不同于我国南方山地,西北干旱地区和华北平原的自身的特点。  相似文献   
948.
Extracellular products in culture filtrates of Aeromonas salmonicida subsp. achromogenes and Vibrio anguillarum isolated from infected fish have been shown to possess skin inflammatory factor. The extracellular products from Vibrio anguillarum were cytotoxic in HeLa and CHO cells. In addition to the skin lesions, the culture filtrates of V. anguillarum caused necrotic reaction on the rabbit skin. Five of 6 strains of V. anguillarum were lethal to mice after intraperitoneal administration of 3×107 CFU. Only 1 strain of 5 A. salmonicida subsp. achromogenes produced extracellular products which elicited cytotoxic effects in the CHO cells. None of the A. salmonicida subsp. achromogenes strains were lethal to mice. The cytotoxins were inactivated when heated at 65°C for 30 min. The results indicate that the thermolabile exotoxins are non-enterotoxic since they failed to stimulate fluid accumulation in the rabbit ileal loop and did not cause elongation of the CHO cells. The rounding off of CHO cells, as well as of HeLa cells indicate that the exotoxins may play an important role in fish diseases.  相似文献   
949.
Two field experiments were carried out during 1982/83 and 1983/84 seasons at Experimental Farm of National Research Centre at Shalakan, Kalubia Governorate, Egypt, to study the effects of supplemental growth factors on the reversal of glyphosate-induced inhibition in photosynthetic pigments and protein in faba beans. A split plot design with four replications was used in both seasons. Glyphosate at 0,312 and 468 g.a.i./ha as well as the untreated treatment, arranged at random in main plots while, the growth factors, i.e., growth regulators, amino acids and nutrient elements at different concentrations distributed randomly in the sub plots. The results could be summarized as follows:
1. Glyphosate decreased chlorophyll a, b and carotenoides content and the total pigments content in the leaves of faba bean plants, as well as, the protein content of seeds and protein yield per hectare.
2. The treatments of phenylalanine at 500 ppm, urea at 1 %, cytolinin at 4/1000 and tryptophan at 500 ppm, reversed the glyphosate-induced-phytotoxicity on decreasing the chlorophyll a, b content and total pigments content in faba bean leaves. The same treatments, as well as, zinc sulfate at 1 %, reversed the glyphosate-induced-phytotoxicity on decreasing the carotenoids content in faba bean leaves.
3. The treatment of G a 3 at 100 ppm gave the highest percentage of crude protein in seeds, while the lowest value was obtained from cytokinin at 4/1000, in both seasons.
4. The treatments of cytokinin at 4/1000, phenylalanine at 500 ppm and tryptophan at both levels, reversed the glyphosate-induced-phytotoxicity on decreasing the protein yield per h.  相似文献   
950.
The influence of environment on animal health was studied in 40 bacon herds. These herds delivered approx. 11,000 baconers annually to the slaughter-house. The data from the meat inspection was studied in connection with the environmental recordings, and the relationship between 18 lesions and 20 environmental factors were estimated by statistical methods. The data was collected in the period 1975–1977.The influence of environmental factors upon the prevalence of different lesions showed considerable variation. Ten environmental factors were significantly associated with pleurisy and tail lesions (cannibalism). On the other hand none of the environmental factors bore any significant relation to atrophic rhinitis, pericarditis, peritonitis, perihepatitis, polyarthritis, arthritis and claw lesions. Eight environmental factors influenced the proportion of healthy animals.The recorded environmental factors influenced the overall health situation to a varying degree. For example, design of pen walls, insulation of pen floors, occasional use of supplementary feed and free access to drinking water were related to 5–7 lesions, while the nature of the concentrate (meal/pellets) had no significant influence.The study indicated that many details in environment and management could be of importance to the health of bacon pigs. However, statistical analysis also showed that production systems had a considerably stronger influence upon the health situation than any of the “pure” environmental factors – even when these factors were added.  相似文献   
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