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   50篇
  免费   4篇
测绘学   2篇
大气科学   18篇
地球物理   14篇
地质学   9篇
海洋学   4篇
天文学   2篇
自然地理   5篇
  2021年   1篇
  2020年   2篇
  2019年   1篇
  2018年   4篇
  2017年   3篇
  2016年   6篇
  2015年   6篇
  2014年   5篇
  2013年   6篇
  2012年   3篇
  2011年   2篇
  2010年   1篇
  2009年   1篇
  2008年   4篇
  2006年   1篇
  2004年   1篇
  2003年   1篇
  1998年   1篇
  1988年   1篇
  1980年   1篇
  1979年   2篇
  1968年   1篇
排序方式: 共有54条查询结果,搜索用时 8 毫秒
51.
52.
Previous studies have shown that aryl hydrocarbon receptor (AhR) agonists possess anti-estrogenic activities and several mechanisms have been proposed to explain the interactions between AhR and estrogen receptor (ER) signalling pathways. In the present study, we show that 3,3'4,4'5-pentachlorobiphenyl (PCB126 - a dioxin-like AhR agonist) produced estrogenic responses in the absence of ER agonist, in fish in vitro system. We exposed salmon primary hepatocytes to PCB126 (1, 10 and 50 pM) and the ER agonist nonylphenol (NP; 5 and 10 microM) singly and also in combination. Vitellogenin (Vtg) and zona radiata proteins (Zr-proteins) levels were analysed by semi-quantitative ELISA. We observed that the protein levels of Vtg and Zr-proteins were significantly induced in a concentration-specific manner in cells treated with PCB126 and NP, singly or in combination. In general, these results show a novel aspect of dioxin-like PCB effect not previously demonstrated in fish system.  相似文献   
53.
54.
Augustine Tanle 《GeoJournal》2014,79(5):577-590
In Ghana, studies on migration and livelihoods are mostly limited to migrants’ places of origin. This paper therefore assesses livelihood status of permanent migrants resident in the Obuasi Municipality who hail from the northern parts of Ghana. The instrument used was a survey questionnaire and the respondents were both migrants and indigenes aged 18 years and above. The findings showed no significant differences between migrants and indigenes in ownership of assets and consumer durable goods and housing quality. However, the indigenes earned relatively higher than the migrants due to access to various forms of capital and the influence of institutional structures and processes. But to the migrants, their livelihood status has improved since they have built houses, educated their children, remitted relations at home and have acquired some consumer durable goods. Improvement in the livelihood status of migrants could induce further north–south migration. There is therefore the need for government and other stakeholders to bridge the gap of unequal socio-economic development between the northern and southern parts of the country.  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