首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   92篇
  免费   16篇
  国内免费   44篇
测绘学   4篇
地球物理   5篇
海洋学   109篇
天文学   1篇
综合类   32篇
自然地理   1篇
  2024年   1篇
  2023年   3篇
  2022年   5篇
  2021年   2篇
  2020年   6篇
  2019年   3篇
  2018年   7篇
  2017年   4篇
  2016年   7篇
  2015年   11篇
  2014年   6篇
  2013年   13篇
  2012年   14篇
  2011年   11篇
  2010年   9篇
  2009年   10篇
  2008年   10篇
  2007年   11篇
  2006年   12篇
  2005年   3篇
  2004年   2篇
  2003年   1篇
  1999年   1篇
排序方式: 共有152条查询结果,搜索用时 15 毫秒
41.
本研究目的为开展许氏平鲉(Sebastes schlegelii)遗传改良和优质新品系选育,选取荣成(R)和长岛(C)的野生许氏平鲉为基础群体,采用群体选育(群体内和群体间)和家系选育相结合的方法,获得R-F1、RC-F1两个群体选育群体和R-F2、RC-F2、R-F3、RC-F3四个家系选育群体。对4个选育家系的生长性能进行比较分析,并利用20对高多态性的微卫星标记对8个群体进行遗传多样性检测。结果表明:(1)群体内和群体间家系选育子3代比家系选育子2代生长速度分别提高21.59%和30.99%。4个选育家系后代的绝对增重率随着天数的增加而上升,群体内家系选育(R-F3)的生长速度、绝对增重率显著大于群体间的杂交选育系(RC-F3),杂交系未表现出生长的杂种优势。(2)20对微卫星位点在所有群体中均表现出较高多态性,8个群体的平均有效等位基因数(Νe)为2.9849—7.9598,平均观测杂合度(oH)和期望杂合度(He)分别为0.7230—0.8405和0.6315—0.8716,平均多态信息含量(PIC)为0.6472—0.8478。经两代家系选育的R-F3和RC-F3平均等位基因数显著降低,但观测杂合度(Ho)和期望杂合度(He)均值仍达到0.7230、0.7549和0.6527、0.6315,还有维持了较高的遗传多样性水平,遗传潜力较大。Hardy-Weinberg平衡检测结果和遗传偏离指数(d)表明各群体在大约10个位点上表现出一定程度的杂合子缺失现象。群体间平均遗传分化系数(Fst)为0.1279,各群体间存在中等遗传分化程度。R与R-F1分别与RC-F3遗传距离最远(0.9959、0.9848),预测利用两组群体中生长优良个体分别进行杂交育种有可能获得杂种优势。  相似文献   
42.
Ulva species can grow rapidly in nutrient-rich habitats causing green tides and marine fouling. A more complete understanding of the reasons behind these outbreaks is urgently required. Accordingly, this study attempts to use microsatellite markers based expressed sequence tag(EST) to analyze the genetic variation of several Ulva prolifera populations in the South Yellow Sea of China. Two hundred and thirty-eight SSRs were identified from 8 179 unique ESTs(6 203 newly sequenced and 1 976 downloaded from NCBI database) and 37 primer pairs were successfully designed according to the ESTs; 11 pairs were selected to detect the genetic diversity and relationship of 69 attached U. prolifera samples and 13 free-floating samples collected from coastal and off-coast areas of the South Yellow Sea. The results of cross-species transferability showed that six of the 11 EST-SSR primers could give good amplification in other five Ulva species and the average allele number was 4.67. Genetic variation analysis indicated that all 82 U. prolifera samples were clearly divided and most samples collected from the same site clustered together as a group in the dendrogram tree produced by unweighted pair-group mean analysis(UPGMA) method and the cluster results showed some consistency with the geographical origins. In addition, 13 free-floating samples(except HT-001-2) were grouped as a single clade separated from the attached samples.  相似文献   
43.
The genetic structure of populations is often shaped by the reproductive system and larval properties of the species. The waratah anemone (Actinia tenebrosa) reproduces through both asexual clones, which have very short-distance dispersal, and sexual larvae, which are believed to disperse much greater distances. The impact of this mixed strategy on the New Zealand population structure of Actinia tenebrosa was investigated using microsatellite markers. The analysis incorporated 24 sampling locations from around New Zealand and one Australian location, using four microsatellite markers, n = 420. We observed low connectivity and high genetic differentiation between all locations sampled, with a distinct pattern of isolation by distance. The most distinct grouping of locations sampled was the north-east of the North Island from Cape Reinga to East Cape, which was identified by SAMOVA and STRUCTURE analyses as being moderately diverged from the remainder of the country. A tentative correlation was observed between genetic clustering and biogeographic regionalisation, where the distribution of a number of genetic clusters matched previously defined biogeographic regions. Within each location sampled, large numbers of clones were present and a latitudinal cline was observed in the relative contribution of asexually and sexually generated recruits, with an increase in asexual recruits on the South Island's east coast.  相似文献   
44.
采用紫外线(UV)灭活的同源精子通过冷休克抑制第二极体排放诱导黄姑鱼(Nibea albiflora)的雌核发育。结果表明,黄姑鱼精子最适的灭活剂量为420mJ/cm2,紫外照射剂量与黄姑鱼精子和卵子授精后的受精率及孵化率之间表现出明显的Hertwig效应。多次试验筛选的黄姑鱼雌核发育的最适条件为授精后2min于3℃处理8min。雌核发育仔鱼经形态学和流式细胞仪鉴定为二倍体。进一步利用10对微卫星分析了遗传物质在亲本和子代中的传递情况,结果表明雌核发育后代的等位基因完全来自于母本,没有父本基因参与;雌核发育后代在5个微卫星位点具有较高的重组率,使其与母本保持了高度同质性。  相似文献   
45.
Ten novel polymorphic microsatellite loci were developed using an enrichment and colony hybridization protocol and characterized for the cuttlefish, Sepiella maindroni. Polymorphism was explored by using 30 individuals from the coastal waters of Zhanjiang, Guangdong province, China, in December 2007. The number of alleles ranged from 5 to 13. The ranges of observed and expected heterozygosity were from 0.578 9 to 1.000 0 and 0.682 8 to 0.925 7, respectively, and the average polymorphic information content (PIC) was 0.778 5. These microsatellite loci will certainly facilitate the detection of the genetic variation and population structure of S. maindroni.  相似文献   
46.
The relationship between microsatellite polymorphism and body weight of captive bred Chinese sea cucumber Apostichopus japonicus was investigated in two local populations in Dalian.Among ten loci discovered, nine show changes except for A J07 loci. Seven loci were found highly polymorphic in both populations. For each locus in two populations, the average number of alleles is 6.428 6 and 6.285 7, the average observed heterozygosity at 0.225 7 and 0.245 9, the expected heterozygosity at 0.776 8 and 0.748 8, the polymorphism information content (PIC) at 0.709 2 and 0.674 6, respectively. Further analysis show significant correlation between A. japonicus body weight and occurrence markers AJ02 and AJ04. The findings of the relation may be helpful for molecular breeding,as well as the marker-assisted selection of sea cucumbers.  相似文献   
47.
摘要:采用聚丙烯酰胺凝胶电泳技术,从20对西大西洋笛鲷(Lutjanus campechamus)的微卫星引物中筛选适用于红鳍笛鲷(L.erythopterus)、勒氏笛鲷(L.russellii)、紫红笛鲷(L.argentimaculatus)和约氏笛鲷(L.johnii)基因组分析的微卫星引物,分析4种笛鲷的遗传多样性及系统发生。经反应条件的优化,从20对引物中筛选出17对可稳定扩增出特异片段的引物。通过测序证实扩增产物含微卫星位点后,以该17对引物对4个种的群体进行遗传多样性分析。其中16对可在约氏笛鲷、勒氏笛鲷、紫红笛鲷基因组中扩增出重复性好的特异性条带,分别有65%、65%、60%呈现出种内多态:15对可在红鳍笛鲷中扩增出重复性好的特异性条带,并且全部呈现出种内多态。四种笛鲷中,红鳍笛鲷的多态性最高,高度多态基因座占检测座位的66.67%;勒氏笛鲷的多态性最低,低度多态基因座占43.75%。获得3个种间特异性分子标记。用风和DA两种方法计算4种笛鲷的遗传距离,构建了系统发生树。  相似文献   
48.
1 Introduction Microsatellites or simple sequence repeats (SSRs) are tandemly repeated motifs of one to six bases found in all prokaryotic and eukaryotic genomes analysed to date (Zane et al., 2002). Due to their hyper-variable and co-dominant nature, relatively high abundance and random distribution in the genome, microsatellites are among the most efficient class of molecular markers. Such repeats display high polymorphism because of variation in repeat length and can be rapidly analysed t…  相似文献   
49.
微卫星DNA标记技术及其在海洋生物遗传学中的应用   总被引:3,自引:0,他引:3  
DNA简单重复序列从1974年在海洋生物中被发现,到1989年“微卫星”术语开始使用这段时间是这种新型分子标记技术的发展阶段。伴随着PCR技术的发明、成熟与拓展,微卫星DNA以其多态性高、随机分布、共显性遗传、重复性好等特点在生物学的个体及系统发育方面得到很广泛的应用。本文从微卫星DNA的发展简史开始,较详细地介绍了它的原理、方法及策略,然后概括了在海洋动、植物的遗传学中,微卫星DNA在遗传多样性分析、遗传图谱构建、基因鉴定和标记以及系谱认证等领域的研究,展望了其在海洋生物分子育种、基因克隆、生物保护等方面的应用前景。  相似文献   
50.
福建太平洋牡蛎种群微卫星DNA分析   总被引:1,自引:0,他引:1  
陈曦  黄勤  江锦祥  马平 《台湾海峡》2007,26(4):548-554
本文采用Ucdcg153、157、202微卫星引物对福建两个太平洋牡蛎(学名为长牡蛎Crassostrea gigas)养殖种群进行扩增分析和序列测定.与采自漳浦旧镇的近江牡蛎(C. ariakensis)比较,前者对以上三种引物全部呈阳性反应,后者只对Ucdcg157显阳性.与Genebank提供的相关序列比较,福建太平洋牡蛎与Genebank样品应属同源,其中漳浦霞美和厦门白礁的样品则可能代表同一种群的两个衍生品系.本项调查结果同时显示,近亲繁殖的育苗方式已经导致福建太平洋牡蛎种群裂化;任其发展不利于维护良种优势.本次采集的样品中未发现显示葡萄牙牡蛎、熊本牡蛎和美洲牡蛎微卫星特征的个体.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号