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   143篇
  免费   11篇
  国内免费   14篇
  2023年   3篇
  2022年   6篇
  2021年   2篇
  2020年   7篇
  2019年   9篇
  2018年   4篇
  2017年   4篇
  2016年   4篇
  2015年   7篇
  2014年   3篇
  2013年   10篇
  2012年   3篇
  2011年   3篇
  2010年   3篇
  2009年   11篇
  2008年   11篇
  2007年   11篇
  2006年   10篇
  2005年   6篇
  2004年   7篇
  2003年   12篇
  2002年   6篇
  2001年   5篇
  2000年   1篇
  1999年   2篇
  1998年   1篇
  1997年   2篇
  1996年   1篇
  1994年   1篇
  1989年   2篇
  1988年   1篇
  1987年   3篇
  1986年   1篇
  1985年   2篇
  1984年   1篇
  1982年   1篇
  1981年   1篇
  1972年   1篇
排序方式: 共有168条查询结果,搜索用时 15 毫秒
101.
华南虎目前处于极危状态。野生个体已极为少见,只有中国一些动物园内饲养着 53只。按其亲缘关系分为上海系和贵阳系,上海系的华南虎携带优秀的多子基因,但其子代的生活力不强;而贵阳系的虎虽然产子率不高,但子代的生活力很强,现存的6只贵阳系华南虎具有极高的基因保存与基因研究价值,应建立基因库。这些虎分散饲养于22个单位,大大降低了适龄虎的交配繁殖机会,浪费了本已有限的珍贵资源,是抑制其种群发展的最主要因素。目前其种群的年龄结构非常合理,育龄虎占种群的62.3%,幼龄虎为28.3%,高龄虎很少,仅为9.4%,今后种群的发展乐观。  相似文献   
102.
圈养华南虎交配行为的初步观察   总被引:2,自引:0,他引:2  
1 研究方法 1.1研究地点 在上海动物园虎山进行观察,虎山由半放养区和笼舍区构成。半放养区模仿野外环境,面积约250m^2。笼舍在半放养区后,共5间,每间由活动铁门隔开。  相似文献   
103.
Eighteen polymorphic microsatellite loci from the highly endangered Sumatran tiger (Panthera tigris sumatrae) were isolated and characterized. Upon polymerase chain reaction amplification, 16 of these markers produced a single, sharp band in all three tiger and 10 non‐tiger felid species examined. Of the two remaining loci, 6HDZ057 and 6HDZ635 failed to amplify genomic DNA from puma (Felis concolor) and cheetah (Acinonyx jubatus), respectively. The amplification of these markers across four genera is an indication of their usefulness for population genetics studies and conservation work in a wide range of felid species.  相似文献   
104.
吉林省东北虎的调查   总被引:26,自引:4,他引:22  
经过8年的调查研究,确定了东北虎在吉林省的分布区有3处,数量为7-9只。即大龙岭分布区3-5只,哈尔巴岭分布区1只,张广才岭分布区3只。东北虎的适宜生境为海拔800-1100m的中低山:人口压力在15人/km^2以下,被捕食动物野猪、狍、马鹿的密度在2.5只/km^2以上。林型为以柞木为主的阔叶混交林,林龄为中成林。  相似文献   
105.
半散放东北虎产仔行为的初步观察   总被引:2,自引:0,他引:2  
张明海  张常智  刘丹 《兽类学报》2006,26(3):255-261
1999年4月至2003年6月,采用随机取样法、扫描取样法和目标取样法对黑龙江东北虎林园半散放条件12只成年雌性东北虎的产仔行为进行观察。结果表明,半散放雌性东北虎的产仔行为可分为9种:站立、行走、躺卧、嗅闻、努责、梳理、生产、亲仔和舔食。雌性东北虎的躺卧和亲仔行为时间最长,分别为42.9% 和34.5% ;躺卧、努责和亲仔行为发生频率较高,分别为21.1%、16. 9% 和24.6%。单因素方差分析表明,不同雌性东北虎个体间躺卧、亲仔等行为有显著差异;不同年份雌性成年东北虎的站立、躺卧、梳理等产仔行为也具有显著差异。相关分析显示,躺卧行为与亲子行为(rs= 0.602, P<0.05)、梳理行为(rs=0.589,P<0.05)均呈负相关。  相似文献   
106.
虎的保护遗传学研究进展   总被引:1,自引:0,他引:1  
陈珉  张恩迪  李冰 《四川动物》2007,26(1):216-220
回顾了关于虎的遗传变异、种群结构、系统分类等保护遗传学研究,发现虎在遗传进化上面临的最严重与最需要解决的问题是遗传多样性低,圈养种群存在近交退化。为了有效保护和管理好虎现存的种群,建议划分虎的进化单元与保护管理单元,人工促进同一进化单元虎的基因交流;同时建立虎的基因文库,保护虎的基因资源。  相似文献   
107.
The tiger is one of many species in which individuals can be identified by surface patterns. Camera traps can be used to record individual tigers moving over an array of locations and provide data for monitoring and studying populations and devising conservation strategies. We suggest using a combination of algorithms to calculate similarity scores between pattern samples scanned from the images to automate the search for a match to a new image. We show how using a three-dimensional surface model of a tiger to scan the pattern samples allows comparison of images that differ widely in camera angles and body posture. The software, which is free to download, considerably reduces the effort required to maintain an image catalogue and we suggest it could be used to trace the origin of a tiger skin by searching a central database of living tigers'' images for matches to an image of the skin.  相似文献   
108.
Abstract. 1. The tiger swallowtail butterfly, Papilio glaucus (L.) (Lepidoptera: Papilionidae), is commonly assumed to have a bivoltine life cycle in central New York State and other parts of the northeastern United States. The seasonal abundance of adults in Tompkins County, New York, shows a bimodal pattern in some years, and a skewed unimodal pattern in others. We studied the incidence of diapause, the potential for successful development of two generations in the field, and the dates of adult emergence from overwintering pupae to determine whether these seasonal patterns are the result of bivoltinism.
2. Insects from Tompkins County, reared as larvae under 16L:8D photoperiod, uniformly enter pupal diapause.
3. Comparison of the heat units required for successful development of two generations with the heat units available in the field during 11 years shows that emergence of non-diapausing individuals would occur too late in the summer to contribute to the second peak of butterfly abundance. Offspring of non-diapausing individuals could only rarely complete development before the end of the growth season.
4. Diapausing offspring of butterflies collected in early June and late July differed sufficiently in dates of emergence to account for the field pattern of seasonal abundance.
5. Electrophoretic studies revealed no evidence of genetic isolation between early and late emerging butterflies.
6. These results suggest that polymodal emergence of diapausing insects can masquerade as a bivoltine life cycle.  相似文献   
109.
Population dispersal and migration often indicate an expanded habitat and reduced inbreeding probability, and to some extend reflects improvement in the condition of the population. The Amur tiger population in the northern region of the Changbai mountain in China mostly distributes along the Sino–Russian border, next to the population in southwest Primorye in Russia. The successful dispersal westward and transboundary movement are crucial for the persistence of the Amur tiger in this area. This study explored the spatial dispersal of the population, transboundary migration, and the genetic condition of the Amur tiger population within the northern Changbai mountain in China, using occurrence data and fecal samples. Our results from 2003 to 2016 showed that the Amur tiger population in this area was spreading westward at a speed of 12.83 ± 4.41 km every three years. Genetic diversity of the Amur tiger populations in southwest Primorye was slightly different than the population in our study area, and the potential individual migration rate between these two populations was shown to be about 13.04%. Furthermore, the relationships between genetic distances and spatial distances indicated the existence of serious limitations to the dispersal of the Amur tiger in China. This study provided important information about spatial dispersal, transboundary migration, and the genetic diversity of Amur tigers in China, showed the urgent need for Amur tiger habitat restoration, and suggested some important conservation measures, such as corridor construction to eliminate dispersal barriers and joint international conservation to promote trans‐boundary movement.  相似文献   
110.
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