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   256篇
  免费   11篇
  2016年   6篇
  2015年   9篇
  2014年   5篇
  2013年   3篇
  2012年   7篇
  2011年   3篇
  2010年   11篇
  2009年   3篇
  2008年   6篇
  2007年   9篇
  2006年   5篇
  2005年   4篇
  2004年   3篇
  2002年   2篇
  2001年   2篇
  1999年   3篇
  1998年   4篇
  1997年   3篇
  1996年   9篇
  1995年   9篇
  1994年   2篇
  1993年   4篇
  1992年   5篇
  1991年   3篇
  1990年   5篇
  1988年   5篇
  1986年   4篇
  1985年   2篇
  1984年   3篇
  1983年   5篇
  1980年   4篇
  1979年   6篇
  1975年   2篇
  1962年   3篇
  1959年   9篇
  1958年   5篇
  1957年   5篇
  1956年   11篇
  1955年   3篇
  1954年   6篇
  1953年   6篇
  1952年   8篇
  1951年   2篇
  1950年   11篇
  1949年   3篇
  1948年   2篇
  1946年   4篇
  1937年   3篇
  1935年   2篇
  1930年   3篇
排序方式: 共有267条查询结果,搜索用时 15 毫秒
101.
One hundred and ten cervical smears were circulated to five specialist consultant cytopathologists and five consultant histopathologists. Of these smears, 100 were randomized and re‐circulated. The cytopathologists reported endocervical cells and wart virus infection more frequently than the histopathologists, although neither group showed good inter‐observer agreement for either assessment. Apart from smear adequacy and the presence of endocervical cells, both groups showed good intra‐observer agreement in all the parameters measured. This suggests that overall individuals were applying their own personal criteria with consistency over time, although a previous study had shown considerable lack of inter‐observer agreement among the histopathologists on the grade of dyskaryosis and the management recommendation. The results indicate that specialist cytopathologists bring a different viewpoint to the reporting of cervical smears than histopathologists. They also show a lack of standardization in the reporting of smears despite the guidelines issued by the British Society for Clinical Cytology.  相似文献   
102.
103.
SUMMARY: Two methods have been developed for isolating and enumerating group D faecal streptococci from localities such as bacon factories where they are heavily outnumbered by other organisms. The first depends on presumptive counts in a Lab-Lemco-peptone-glucose broth (pH 6·0) containing 0·1% of thallous acetate with confirmation by streaking on tetrazolium agar. The other method involves direct plating on tetrazolium-glucose agar (pH 6·0) containing 0·1% of thallous acetate. On the tetrazolium medium differentiation can be made between Streptococcus faecalis and its variants zymogenes and liquefaciens and the other group D organisms, Strep. faecium, Strep. durans and Strep. bovis .  相似文献   
104.
Fully fed larvae of the wheat-blossom midges need moist conditions in order to descend from the ears to the soil. A dry spell coinciding with the fully fed stage therefore causes an accumulation of larvae, which subsequently leave the ears in a body when rain comes. Conversely, in wet weather each larva leaves the wheat as soon as it finishes feeding, and, since all the eggs are not laid on the same day, the descent will then be a gradual process.
A method is described of taking small samples of wheat ears at frequent intervals, thus facilitating the determination of the correct date on which to take the main sample for the assessment of infestation by the two wheat-blossom midges.  相似文献   
105.
The genes for the large and small subunits of anthranilate synthase (trpE and trpG, respectively) have been cloned from Pseudomonas aeruginosa PAC174 into E. coli by R-prime formation with the broad-host- range plasmid R68.44. Sequential subcloning into plasmid vectors reduced the active Pseudomonas DNA fragment to a length of 3.1 kb. We obtained evidence that this region contains the promoter for its own expression and retains a vestigial regulatory response to tryptophan scarcity or excess.   相似文献   
106.
107.
Polypterids, the most basal actinopterygians, are a group of fish long-considered living fossils and holding a key position for understanding fish and tetrapod evolution. Knowledge of the natural history of Polypterus is limited, their having been studied in little detail since the early 1900s. The locomotory habits of wild Polypterus senegalus from Lake Albert, Uganda, were investigated in 2014. High-speed videography demonstrated the capability of large Polypterus to move overland successfully. Contrary to previous evidence, field observations found that terrestrial locomotion in Polypterus is not inherently restricted by body size. Evidence that Polypterus exhibit this behaviour as part of their natural life history can be found in the existence of environmental challenges and the presence of adaptations for amphibious life.  相似文献   
108.
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