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931.
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   
932.
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   
933.
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   
934.
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   
935.
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   
936.
937.
A cross-sectional study was conducted to determine the seroprevalence of anti-Toxoplasma gondii and anti-Neospora caninum antibodies and to investigate the risk factors related to antibodies against T. gondii and N. caninum in dogs of the city of Campina Grande, state of Paraiba, Northeast region of Brazil. For this purpose, 286 blood samples were collected from dogs during the rabies vaccination campaign, in September 2003, and on this occasion questionnaires addressing epidemiological aspects of the infections were given to each dog owner. The sera were analyzed for anti-T. gondii and anti-N. caninum antibodies by indirect fluorescent antibody tests. Of the total of 286 dogs, 129 were positive for T. gondii (titer16) with a prevalence value of 45.1% (95% CI=39.24-51.07%). For N. caninum, 24 dogs were positive (titer50), with a prevalence value of 8.4% (95% CI=5.45-12.23%). Antibodies to T. gondii and N. caninum were found simultaneously in 14 dogs (4.9%; 95% CI=2.7-8.08%). For T. gondii infection, the risk factors associated with seroprevalence was the age of the animals, with dogs older than one year presenting higher values of odds ratio, and co-habitation of cats in the household. For N. caninum infection, dogs that have street contact had higher odds of seropositivity than dogs that remained exclusively in a domestic environment.  相似文献   
938.
通过在控制灌溉的条件下进行的水稻不同插植密度试验,得出了插植规格为30cm×13cm、每穴3苗、即插植密度为76.5万苗/hm2的水稻群体透光性最佳、叶面积系数最合理,为宁夏银川灌区控制灌溉条件下水稻旱育稀植栽培的最佳插植密度。  相似文献   
939.
A retrospective cohort study was designed to examine the effect of sex, season of birth, type and year of birth, and birth weight on lamb mortality. The method used involved analysis of breeding records for Sahelian sheep kept on a breeding station at Pong-Tamale in northern Ghana from 1994 to 2000. The pre-weaning and post-weaning mortalities were 10% (n = 505) and 19% (n = 453), respectively, while the overall mortality from birth up to 12 months of age was 28% (n = 505). Compared to the pre-weaning period, the post-weaning period recorded significantly higher proportions of deaths in male, single-born, lambs born in the rainy or dry seasons, and in lambs with low (<3 kg) or high (> or =3 kg) birth weight. The odds and risks of death for male lambs were about one and a half times those for females at post-weaning. Lambs born in the dry season had significantly higher mortality than those born in the rainy season. Lambs that died by the time of weaning were not significantly different in weight at birth from those that survived. The mean birth and weaning weights of single-born lambs were significantly higher than those for twins. The mean pre-weaning ADG was significantly higher in lambs born as singles compared to that for twins. The season of birth had influence on mean birth weight, with those born in the rainy season having significantly higher weights than those born in the dry season. The year of birth significantly affected birth weight, weaning weight, weight at 12 months and ADG at all stages of the lambs' life. The study concluded that the most significant risk factors for lamb mortality included sex of the lamb, season of birth and birth weight. The last two could be manipulated, to some extent, to reduce lamb mortality.  相似文献   
940.
认为我国企业在适当继续搞好“有形因素”竞争的同时,还应该进一步加大“无形因素”这一竞争手段的实施力度。  相似文献   
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