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   212篇
  免费   22篇
  国内免费   182篇
  2022年   1篇
  2021年   2篇
  2020年   26篇
  2019年   20篇
  2018年   2篇
  2017年   2篇
  2016年   17篇
  2015年   42篇
  2014年   12篇
  2013年   33篇
  2012年   20篇
  2011年   1篇
  2010年   29篇
  2009年   16篇
  2008年   13篇
  2007年   4篇
  2006年   3篇
  2005年   6篇
  2004年   5篇
  2003年   10篇
  2002年   4篇
  2001年   11篇
  2000年   10篇
  1999年   8篇
  1998年   18篇
  1997年   8篇
  1996年   8篇
  1995年   2篇
  1994年   2篇
  1993年   3篇
  1992年   6篇
  1991年   3篇
  1990年   3篇
  1988年   2篇
  1987年   1篇
  1986年   3篇
  1984年   4篇
  1983年   3篇
  1982年   9篇
  1981年   6篇
  1980年   3篇
  1979年   5篇
  1978年   3篇
  1977年   4篇
  1976年   9篇
  1975年   4篇
  1974年   2篇
  1973年   3篇
  1972年   5篇
排序方式: 共有416条查询结果,搜索用时 15 毫秒
131.
132.
133.
A diketopiperazine derivative isolated from the soy-bean meal hydrolysates, AMINOSAN-EKI, has been proved as l-isoleucyl-l-valine anhydride by elemental analysis, melting point, and by paper chromatography. l-Isoleucyl-l-valine anhydride must be derived from the dipeptide produced by hydrolysis of the proteins.  相似文献   
134.
135.
136.
现生的鼹科动物分布于欧亚大陆和北美大陆,包括54种已知物种。鼹科动物有丰富的生态类型,是研究适应性进化的较好模型。本研究通过二代测序的方法分别获得了长吻鼩鼹和库氏长吻鼹两个物种心脏和肺脏以及脾脏和肺脏的转录组数据。这两个物种分别代表了分布于中国西南部、缅甸北部的没有特化的原始类群鼩鼹亚科以及高度适应地下生活的鼹亚科鼹族。我们首次报道了库氏长吻鼹在中国的分布。通过从头拼接,分别获得长吻鼩鼹和库氏长吻鼹197 092个和225 956个转录本,以及125 427个和94 023个unigene。通过与GenBank中的基因组注释文件比对,得到鼹科物种同源基因家族8 376个,及鼹科鼩鼱科同源基因家族8 114个。差异表达基因中各组织的高表达基因中均找到10个以上组织特异性基因。然而BUSCO分析确定完整单拷贝基因在两个物种中分别为43.0%和56.6%,提示死后mRNA迅速降解并影响转录组拼接。比较两个物种肺部基因的表达差异发现库氏长吻鼹335个相对高表达的基因,其中包括HMGB1HSPD1SF3B1COL3A1SUMO1JUNB等,有报道上述基因可能与低氧或高海拔适应有关。  相似文献   
137.
138.
139.
The modified population dynamics of pests targeted by the Cry1Ac toxin in Bacillus thuringiensis (Bt) transgenic cotton (Bt cotton) and possible reduced insecticide use in these transgenic varieties may exert a variety of effects on ground‐dwelling predator communities. A survey of ground‐dwelling arthropods was carried out weekly each of 3 years (during the cropping season) in commercial Bt and non‐Bt cotton fields. Sixty‐five taxa of ground‐dwelling arthropods (carabids, cicindelines, staphylinids, dermapterans, heteropterans and araneids) of importance for cotton pest management were recorded in the survey. Species abundance and dynamics across seasons were evaluated with univariate analysis of variance for higher taxa or multivariate principal response curve analysis for the whole community of 65 taxa. Diversity and richness indices and cumulative species curves also were calculated. The analyses demonstrated no differences in the ground‐dwelling arthropod communities between cotton types. One araneid species, Pardosa pauxilla, comprised ~80% of all araneids, Labidura riparia comprised ~96% of all dermapterans, Megacephala carolina comprised ~97% of cicindelines and four carabid species (Selenophorus palliatus, Apristus latens, Harpalus gravis and Anisodactylus merula) comprised ~80% of carabid species. M. carolina outnumbered all other collected species in each of the 3 years. When only predatory carabid species were considered, A. merula, Calosoma sayi, Harpalus pennsylvanicus and Stenolophus ochropezus were predominant and numbers trapped were similar between cotton types. The abundance of dermapterans, staphylinids, araneids and heteropterans varied among sample dates and across seasons but did not differ between cotton types. The frequent capture of M. carolina, S. palliatus and P. pauxilla in all fields and seasons in both cottons suggests that these species may be important for monitoring further changes in local communities as result of agricultural practices.  相似文献   
140.
The growth and development of the endangered Mahogany Glider (Petaurus gracilis) was monitored in a captive population at Burleigh Heads, Queensland, Australia. Video surveillance confirmed that the gestation period for this species was 16 days. Morphometric data and developmental milestones were recorded from 10 Mahogany Gliders from birth to weaning. Growth curves were developed for head length, ulna length, tail length, and body weight. Weekly inspections of female pouches revealed the young's eyelid margins were visible by Day 21, the first hair erupted on the bridge of the nose at Day 30, pigmentation of the body developed at Day 63, and they started detaching from the teat intermittently, and the body was covered in short fur by Day 70. The young were left in the nest alone from Days 84 to 87, their eyes opened between Days 84 and 94, and there was a rapid increase in length and density of fur from Day 98 onwards. At Days 101 to 105 of age the young left the nest box with its mother as back young. Weaning occurred from 184 to 187 days. Typically, the reproductive rate was two young per annum per pair, but one pair produced five young in 19 months. Females produced young from 12 months to 7 years of age, males up to 9.4 years of age. The average longevity of Mahogany Gliders in the studbook in 2018 was 11.6 years. This study provides data on the reproductive biology of the Mahogany Glider that will assist in its captive breeding, management, and conservation.  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