貉精子发生的研究     

房秀 《黑龙江动物繁殖》1999,7(2):8-10

本文应用光镜和电镜技术,研究了雄貉生殖细胞,支持细胞的细胞学变化及发育规律。结果表明,貉生精细胞的细胞结构和精子发生与其它哺乳动物相似,从精子细胞经过四个阶段的变态而形成分化完善的精子,支持细胞内微管参与生精上皮的构筑,精子细胞的运动和释放,在附睾内随着精子的迁移,胞质脂滴逐渐减少,同时在附睾内有假顶体反应精子。  相似文献   

中国岩溶地区农业持续发展战略问题与对策研究   总被引：9，自引：2，他引：7  

Research Group of Sustainable Agricultural Development in Karst Regions of China  Chinese Academy of Engineering 《草业学报》1999,(Z1)

我国岩溶地区存在许多发展经济的困难 ,如水土流失严重 ,石漠化加剧 ;人口过度增长 ,贫困面大 ;农耕土地质量差 ,农业生产水平低 ;半年干旱 ,地表水缺乏 ;地方交通不便 ,商品经济发展滞后 ;教育文化落后 ,科技普及困难等。同时也存在巨大潜力 ,如水热资源、生物资源、能源、矿产资源丰富 ,旅游资源独具特色 ,以及地缘优势。在制订农业发展战略目标时 ,应坚持以下原则 :可持续发展的大农业原则 ;以生态经济区域为依据、分类指导的原则 ;占有市场一定份额的大产业原则 ;国内和国际大交换原则 ;提高全民素质的大科技原则。为中国岩溶地区农业持续发展提出 5项重大建议 :加大对岩溶地区扶贫攻坚的支持力度 ,分类指导 ,着力解决特困地区、特困乡村和特困农户的脱贫问题 ;建立以林为主的生态恢复与重建示范工程 ;建立以草地畜牧业为主的资源开发利用产业化示范工程 ;适当加大政策倾斜力度 ,支持岩溶山区支柱产业发展和基础设施建设 ;将“岩溶地区农业持续发展的战略问题与对策研究”列入国家重点攻关研究项目和国家级农业发展综合示范工程项目 ,组织协同攻关  相似文献   

江西棉铃虫综合治理措施   总被引：1，自引：0，他引：1  

江西省棉铃虫猖獗成因及治理措施的研究课题组 《江西植保》1999,(1):1-3

近几年来江西棉铃虫几乎年年大发生。本文提出适合江西棉区推广应用的棉铃虫综合治理措施,包括种植抗虫棉、农业防治、化学防治等。冬耕、中耕和灌水灭蛹,整枝灭卵,杨柳枝把或高压汞灯诱蛾都是有效的综防措施。防治策略、防治指标和施药技术是化学防治的关键。  相似文献   

The impact of maternal employment on breast-feeding duration in the UK Millennium Cohort Study     

Hawkins SS  Griffiths LJ  Dezateux C  Law C;Millennium Cohort Study Child Health Group 《Public health nutrition》2007,10(9):891-896

OBJECTIVE: To examine the relationship of maternal employment characteristics, day care arrangements and the type of maternity leave pay to breast-feeding for at least 4 months. DESIGN: Cohort study. SETTING: Babies aged 9 months in the Millennium Cohort Study, born between September 2000 and January 2002. SUBJECTS: A total of 6917 British/Irish white employed mothers with singleton babies. RESULTS: Mothers employed part-time or self-employed were more likely to breast-feed for at least 4 months than those employed full-time (adjusted rate ratio (aRR) and 95% confidence interval (CI) 1.30 (1.17-1.44) and 1.74 (1.46-2.07), respectively). The longer a mother delayed her return to work postpartum, the more likely she was to breast-feed for at least 4 months (P for trend < 0.001). Mothers were less likely to breast-feed for at least 4 months if they returned to work for financial reasons (aRR 0.86, 95% CI 0.80-0.93) or used informal day care arrangements rather than care by themselves or their partner (aRR 0.81, 95% CI 0.71-0.91). Mothers were more likely to breastfeed for at least 4 months if their employer offered family-friendly (aRR 1.14, 95% CI 1.02-1.27) or flexible work arrangements (aRR 1.24, 95% CI 1.00-1.55), or they received Statutory Maternity Pay (SMP) plus additional pay during their maternity leave rather than SMP alone (aRR 1.13, 95% CI 1.02-1.26). These findings were independent of confounding factors, such as socio-economic status and maternal education. CONCLUSIONS: Current policies may encourage mothers to enter or return to employment postpartum, but this may result in widening inequalities in breast-feeding and persistence of low rates. Policies should aim to increase financial support and incentives for employers to offer supportive work arrangements.  相似文献   

白斑狗鱼耗氧率和窒息点研究     

乔德亮李思发  凌去非殷建国蔡晓琴  李岩平何智杰 《上海海洋大学学报》2005,14(2):202-206

白斑狗鱼(Esoxlucius)属鲑形目(Salmoniformes)、狗鱼科(Esocidae)、狗鱼属(Esox),北半球北部亚冷水性大型凶猛淡水鱼类,我国仅产于新疆北部额尔齐斯河流域,如额尔齐斯河、布尔津河、哈巴河等及附属水体。鱼类大多数代谢活动都和氧的利用有关,耗氧率直接或间接地反映新陈代  相似文献   

Mode of Action of the Novel Rice Blast Fungicide KTU 3616     

Y. Kurahashi  the late T. Hattori  S. Kagabu  R. Pontzen 《Pest management science》1996,47(2):199-200

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我国水土保持生态补偿机制研究(续)   总被引：3，自引：1，他引：2  

中国水土保持生态补偿机制研究课题组 《中国水土保持》2009,(9):1-4

4生产建设类水土保持生态补偿机制 4．1水土流失特点 本研究中所指生产建设活动,是人类为了进行正常的生产与生活而开展的扰动地表和地下物质、可能造成水土流失的一切活动。生产建设活动的一个显著特点是要扰动地表或地下岩土层、排放废弃固体物、构筑各种人工地貌,造成水土资源的破坏和损失,加剧土壤侵蚀。根据生产建设活动的性质,可以将其划分为资源开发类和非资源开发类两大类。生产建设活动水土流失具有以下特点：①与人类扰动地表程度密切相关。  相似文献   

Deliberations of an Advisory Committee regarding priorities, sources, and methods for collecting animal antimicrobial use data in the United States     

DeVincent SJ  Viola C;Advisory Committee on Animal Antimicrobial Use Data Collection in the United States of the Alliance for the Prudent Use of Anitibiotics 《Preventive veterinary medicine》2006,73(2-3):133-151

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World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of acaricides against (mange and itch) mites on ruminants     

Vercruysse J  Rehbein S  Holdsworth PA  Letonja T  Peter RJ;World Association for the Advancement of Veterinary Parasitology 《Veterinary parasitology》2006,136(1):55-66

These guidelines have been prepared to assist in the planning, conduct and interpretation of studies for the assessment of the efficacy of acaricides against mange and itch mites on ruminants. Information is provided on the selection of animals, dose determination, dose confirmation and field studies, record keeping and result interpretation. These guidelines also are intended to assist the investigators on how to conduct specific experiments, to provide specific information for registration authorities involved in the decision-making process, to assist in the approval and registration of new ectoparasiticides, and to facilitate the worldwide adoption of standard procedures.  相似文献   

耐密型玉米育种相关问题的思考   总被引：7，自引：0，他引：7  

赵保献  梁晓伟  雷晓兵  陈润玲  李林  卫勇强  赵合林 《中国农学通报》2009,25(14):108-112

玉米种植密度逐步提高不仅是玉米产量不断提高的主要途径,也是育种中提高选择效果的重要手段。本文结合我国玉米生产和育种的实际情况,对耐密型玉米品种选育的育种目标、种质选择、自交系选育技术和杂交种鉴定技术进行了探讨。  相似文献