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   138028篇
  免费   5990篇
  国内免费   63篇
  144081篇
  2022年   836篇
  2021年   1476篇
  2020年   1000篇
  2019年   1188篇
  2018年   2454篇
  2017年   2420篇
  2016年   4660篇
  2015年   8495篇
  2014年   8417篇
  2013年   9264篇
  2012年   9083篇
  2011年   6448篇
  2010年   4745篇
  2009年   4386篇
  2008年   3962篇
  2007年   3849篇
  2006年   3558篇
  2005年   9128篇
  2004年   7704篇
  2003年   5752篇
  2002年   3190篇
  2001年   1775篇
  2000年   898篇
  1999年   2034篇
  1998年   871篇
  1992年   2183篇
  1991年   2250篇
  1990年   2317篇
  1989年   2198篇
  1988年   2133篇
  1987年   1967篇
  1986年   1760篇
  1985年   1811篇
  1984年   1241篇
  1983年   965篇
  1982年   595篇
  1979年   1177篇
  1978年   832篇
  1977年   688篇
  1976年   687篇
  1975年   960篇
  1974年   1053篇
  1973年   1076篇
  1972年   1013篇
  1971年   976篇
  1970年   852篇
  1969年   877篇
  1968年   763篇
  1967年   793篇
  1966年   619篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
The aim of this study was to identify plant species among the diverse flora of the caatinga ecosystem that are used therapeutically. Research was undertaken in the municipalities of Piranhas and Delmiro Gouveia, in the Xingó region (state of Alagoas, NE Brazil). In order to identify the medicinal plants used in this region, semi-structured questionnaires were applied. The species cited were collected and sent to the Xingó Herbarium for taxonomic analysis. The relative importance (RI) of each species cited was calculated to verify their cultural importance. The therapeutic indications attributed to the species were classified under 16 body systems. A total of 187 medicinal species were cited, from 64 families and 128 genera. The main indications for medicinal plant use were against common colds, bronchitis, cardiovascular problems, kidney problems, inflammations in general, and as tranquilizers. Approximately 16% (30 plant species) were versatile in relation to their use, with an Relative Importance value over 1, having been indicated for up to nine body systems. The body systems that stood out the most were: the respiratory system, the gastrointestinal system, and infectious diseases. Most cited plant parts used for medicinal purposes were flowers, leaves, and inner stem bark.  相似文献   
104.
105.
106.
The involvement of gibberellins in the control of flowering of sunflower was studied by direct application of GA3 to the apex of the plants, analysis of the endogenous levels of gibberellin-like substances at different plant ages, and indirectly by the application of paclobutrazol, an inhibitor of gibberellin synthesis. GA3 speeded-up flower initiation and floral apex development. The time of GA3 application was more critical than the amount of GA3 applied. The endogenous levels of gibberellin-like compounds increased significantly by day 15 after sowing. The application of paclobutrazol markedly delayed floral initiation and this effect was also depedent on plant age. Both GA3 and paclobutrazol had their greatest effects between 10 and 20 days after sowing suggesting that an increase in gibberellins in that time period plays a role in floral initiation.  相似文献   
107.
The concentrations of Legionella pneumophila in cooling towers may vary considerably over short periods of time, producing significant fluctuations throughout the year. Despite genetic variability, in small geographical areas the same indistinguishable pulsed-field gel electrophoresis patterns may be shared among different cooling towers and persist over time.  相似文献   
108.
In the present work an immunocytochemical characterisation of four endophytic bacterial species has been made by using polyclonal antiserum produced against each of the four bacterial strains previously heated at 60 °C. The aim of this researchsito identify common elements among bacteria associated with their endophytic behaviour. Analysis of extracts of each strain by immunoblotting and ELISA confirmed the presence of proteins from different bacterial strains made up of common epitopes. However, antisaproduced againstHerbaspirillum seropedicae andBurkholderia ambifaria show a high number of bands recognised on each extracts, while antisera againstAzospirillum brasilense andGluconacetobacter diazotrophicus show a low number of bands recognised on each extract. Immunogold labelling showed that epitopes are located both on the cell wall and in the cytoplasm; most likely they could be preursor cell wall proteins synthesized inside the cytoplasm and subsequently transported onto cell wall. Finally, the common bands amog bacterial strains revealed by immunoblotting could play a role as active hydrolases involved in host tissue penetration.  相似文献   
109.
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