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981.
玉米螟的发生程度与5~8月初的降雨和种群质量密切相关,降雨主要影响越冬种群的复苏、化蛹、羽化、成虫的活动及3令前幼虫的存活,5~6月份特别干旱不利于越冬种群的复苏、化蛹和羽化.对成虫的产卵量有影响;7月份的干旱或大暴雨严重影响成虫的活动、卵的孵化和3令前幼虫的存活。不同年度间一、二化种群在越冬种群中所占的比例影响越冬种群的质量,在以一化种群为主时,玉米螟繁殖力强、发生晚,危害重。 相似文献
982.
大豆性状整齐度与产量的关系 总被引:2,自引:0,他引:2
观察测定了同一品种在同一条件下大豆性状的整齐度,同一品种在不同条件下性状的整齐度,不同品种在同一条件下性状的整齐度,统计分析了性状整齐度与实收产量之间的关系,结果表明,要获得大豆高产稳产,应注意植株间荚数和粒数的整齐度。 相似文献
983.
一次防治大豆灰斑病籽粒灰斑 总被引:1,自引:1,他引:0
通过室内及田间大豆不同生育期接种试验证明,籽粒感染灰斑病的关键时期是R3-R5期.R2期以前侵染不造成籽粒斑驳,据此提出一次防治大豆籽粒灰斑病的关键时期为R2-R4期. 相似文献
984.
变截面构件的剪应力计算 总被引:1,自引:0,他引:1
变截面构件的弯曲变形是实际构件常见变形之一,现行钢筋混凝土设计规范提供的和实际设计计算应用的剪应力计算公式未考虑截面变化的影响,有较大的误差。本文用材料力学方法推出考虑变截面影响的剪应力计算公式,以便在实际设计计算应用。 相似文献
985.
Serum antibody (virus neutralisation, complement fixation, IgM and IgG) responses to equine herpesvirus-1 (EHV-1) infection were measured in six foals which were initially free from EHV-1 and EHV-4 infection and maternally-derived antibodies. Following primary infection, high titres of virus neutralisation and complement fixation antibodies were detectable against EHV-1, however, corresponding antibody levels against EHV-4 were low or inapparent, although the two viruses share a number of cross-reactive epitopes. In addition, following the primary infection with EHV-1, IgM levels increased before those of IgG, virus neutralisation and complement fixation antibodies, peaked sooner and thereafter declined. Stimulation of IgM levels was observed on secondary infection with EHV-1 given 61 days later. In contrast, IgG, virus neutralisation and complement fixation antibodies following primary infection were more sustained and no increase in their levels was observed on secondary infection. No consistent changes in IgM or IgG levels were seen after administration of dexamethasone to reactivate latent virus. 相似文献
986.
Ivermectin administered cutaneously at dosages of 2 mg/kg of body weight eliminated nematode infections in leopard frogs. Three clinical trials were conducted. In the first trial, 5 groups of 11 frogs were given ivermectin IM at dosages of 0, 0.2, 0.4, 2, or 20 mg/kg. All frogs given ivermectin IM at dosages of 2.0 mg/kg or greater died. In trial 2, 44 frogs, allotted to 5 groups, were given ivermectin cutaneously at 0, 0.2, 2, or 20 mg/kg. Cutaneously administered ivermectin was not toxic at dosages up to 20 mg/kg. In trial 3, nematode infections were eliminated in all 10 frogs treated cutaneously with ivermectin at 2.0 mg/kg. 相似文献
987.
本文以我国国民经济系统与河南省经济子系统的同构性为基础,利用河南省1987年投入产出表,计算出诺依曼最优生产强度和与之相应的最优价格,进而对照现行价格,提出了我国价格体系改革走向的基本构想,并对其合理性、可行性进行了初步研究。 相似文献
988.
A total of 105 nonboar-exposed, F2 ([Landrace x Yorkshire] x Duroc) gilts were used in two replicates of a randomized complete block experiment to evaluate the effect of dietary feed intake on pubertal onset and subsequent body composition. Feed intakes were established at 50% of ad libitum (AL-50), 75% of ad libitum (AL-75), or at ad libitum (AL-100) levels from 4.5 to 9 mo of age. A corn-soybean meal diet fed to all gilts was formulated to meet or exceed nutrient requirements except for energy. Puberty was measured by two methods: 1) monitored once daily by back pressure applied by the herdsman or 2) from elevated plasma progesterone concentrations. Body composition was evaluated by the deuterium oxide method after plasma progesterone concentrations were elevated. Daily feed intake for the experimental period averaged 1.6, 2.3, and 3.2 kg, and the BW of gilts at 8 mo of age were 111, 131, and 154 kg for the AL-50, AL-75, and AL-100 groups, respectively. Body weight, backfat thickness, and body fat content increased linearly (P < .01) as feed intake increased, but age at puberty was not severely influenced. A minimum body fat content or percentage did not seem to initiate pubertal onset. There was a trend for a lower percentage of the AL-50 gilts to ovulate (P = .08) than those fed the AL-75 and AL-100 intakes. An inverse relationship resulted between the percentage of gilts that ovulated to the percentage that showed behavioral estrus.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
989.
990.