Results 81 to 90 of about 317,448 (190)
, 1992 采用淀粉或聚丙烯酰胺凝胶电泳方法分析了长江中游武汉江段草鱼天然种群(n=81)中10种同工酶约28个基因座位的遗传变异型。该种群的多态座位比例为16.7%,平均杂合度为0.0739。而Utter和Folmar(1978)曾报道美国的5个草鱼人工繁殖种群的多态座位比例及平均杂合度分别为6%和0.021。比较结果表明,近交很可能是导致草鱼人工繁殖种群中遗传变异性降低的主要原因。我们认为生产上采用数量大、来源广的亲鱼进行人工繁殖 ...
吴力钊,王祖熊
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First, He Was Adam, and Then, She Was Eve
Sexuality, Gender &Policy, Volume 9, Issue 4, November 2026.ABSTRACT Trans* is an umbrella term that is used to describe people who identify with a gender that is different from their assigned sex at birth. There has been a marked increase in young people presenting to child and adolescent mental health services due to a lack of specialist gender clinics in the United Kingdom.
Corey Hartley +2 more
wiley +1 more source
, 2012 为了揭示准噶尔盆地西北缘梭梭种群的分布特点,结合径级结构、静态生命表和存活曲线,对准噶尔盆地西北缘两种典型生境条件下梭梭种群年龄结构和空间分布格局进行了研究。研究显示,在不同生境条件下,梭梭种群径级结构差异明显。山前戈壁梭梭种群Ⅰ、Ⅱ、Ⅲ径级个体数占所有径级个体总数的96.21%,大径级个体缺失,该种群发育时间较短,种群处于增长阶段;干涸湖底梭梭种群Ⅰ、Ⅱ、Ⅲ径级个体数占所有径级个体总数的63.38%,存在一定数量的大径级个体,该种群发育历史较长,种群处于稳定阶段。格局分析表明,在不同生境条件下 ...
张希明 +7 more
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Sexuality, Gender &Policy, Volume 9, Issue 4, November 2026.ABSTRACT The experiences of LGBTQIA+ students with disabilities may differ from those of peers who hold only one of these identities. In Greece, however, the educational system lacks clear guidelines for supporting this group. This study investigates LGBTQIA+ students' school experiences with the aim of formulating evidence‐based policy recommendations
Konstantinos Drosos +2 more
wiley +1 more source
野生动物学报, 1999 生物群落的概念很早以前就出现于生物学的各种论著中.本世纪初,对这一概念的理解有两种截然不同的观点,一是认为群落是物种的松散可重复的集合,能作为一个整体在功能上密切统一,并表现出单独机体（超有机体）的特征;第二种观点认为群落至多是物种在分布上的偶然巧合,缺乏内在的组织结构,群落中的物种各自独立地对环境条件做出反映.持不同观点的两大学派各持己见,展开了论战.争论之初,第一种观点占了上风,并统治了该领域几十年之久.到本世纪四十年代末,许多生态学家对第一种群落观点提出挑战认为群落的分类不应该严格不变 ...
赵鲁安 +3 more
doaj
基于线粒体Cyt b基因和CR序列的养殖貉（Nyctereutes procyonoides）种群遗传多样性和结构分析
野生动物学报, 2021 貉（Nyctereutes procyonoides）是一种重要的经济动物。经过50年的人工驯养繁育，国内养殖种群不断扩大，但对其遗传多样性和结构了解很少，难以开展有效的遗传管理。本研究分析了东北、华北地区养殖貉种群（N=160）的线粒体细胞色素b（Cyt b）基因和控制区（CR）序列，并与已经发表的同源序列进行比较。结果定义了5个Cyt b基因和6个CR序列单倍型，其中与俄罗斯产乌苏里亚种共享单倍型分别是3个和4个。种群遗传多样性分析表明，养殖貉种群单倍型多样性处于临界点（Hd=050 ...
魏宏达 李波 魏来 刘志平 姜春明 史迎秋 徐艳春
doaj
, 2010 基于为期3年的水文模拟实验,分析了长期干旱与淹水胁迫对三江平原典型湿草甸、沼泽化草甸及沼泽群落的优势种群——小叶章和毛苔草种群高度和密度的影响。结果显示,在不同群落中,小叶章和毛苔草种群高度总体均随水位升高而增加,毛苔草种群密度总体均随水位升高而下降,而小叶章种群密度随水位升高变化无明显规律性;随水分胁迫时间延长,各水位梯度下两种植物种群高度和密度具有波动性。研究表明,两优势种群在单优群落与混合群落中对水分胁迫均表现出不同的响应特征,种群竞争对两个种群的水分需求具有重要影响 ...
宫辉力, 胡金明, 王丽, 杨涛
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World Food Policy, Volume 12, Issue 2, November 2026.ABSTRACT Agricultural development initiatives in sub‐Saharan Africa have emphasized improved crop varieties as a pathway to food security, resilience, and rural poverty reduction. However, empirical evidence often focuses narrowly on plot‐level outcomes and overlooks whole‐farm effects and the substantial heterogeneity in farmers' management practices,
Kodjo Kondo +4 more
wiley +1 more source
, 2007 本文对黄喉拟水龟的两个种群进行了遗传分析与比较。南方种群与北方种群在体色、成熟个体大小、卵的大小及稚龟的大小方面有明显差异。南方种群背甲颜色较深,头顶为褐色;北方种群背甲颜色较浅,头顶为青绿色;南方种群的成熟个体、卵以及稚龟均明显大于北方种群。用30个随机引物,pcr扩增,28个引物产生了可重复的清晰的扩增图谱,其中有16个引物扩增出特异于南方或北方种群的dna片段,从中鉴定了20个特异于南方或北方种群的分子标记。种内的平均遗传距高为 0．229±0．108,遗传多样性较高。南方种群内的平均遗传距离为0．
陈永乐, 朱新平, 桂建芳, 周莉
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World Food Policy, Volume 12, Issue 2, November 2026.ABSTRACT Globally, there is collective agreement on the need to advance equity within food systems to promote health equity, food security, and social justice through structural transformation. Food systems are shaped by power asymmetries across scales and actors, which influence the realization of the right to food and constrain the agency of ...
Joan Kaburia, Susan J. Elliott
wiley +1 more source