全文获取类型
收费全文 | 138028篇 |
免费 | 5990篇 |
国内免费 | 63篇 |
专业分类
144081篇 |
出版年
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.
Legionella pneumophila in Cooling Towers: Fluctuations in Counts, Determination of Genetic Variability by Pulsed-Field Gel Electrophoresis (PFGE), and Persistence of PFGE Patterns 下载免费PDF全文
Sonia Ragull Marian Garcia-Nuez Maria Luisa Pedro-Botet Nieves Sopena Maria Esteve Rafael Montenegro Miquel Sabri 《Applied microbiology》2007,73(16):5382-5384
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.
Antonella Canini Lorena Canuti Maria Grilli Caiola Maddalena Del Gallo 《Annals of microbiology》2006,56(4):393-398
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.