收费全文 | 1816篇 |
免费 | 105篇 |
国内免费 | 10篇 |
1931篇 |
2023年 | 12篇 |
2022年 | 40篇 |
2021年 | 63篇 |
2020年 | 27篇 |
2019年 | 33篇 |
2018年 | 45篇 |
2017年 | 50篇 |
2016年 | 52篇 |
2015年 | 92篇 |
2014年 | 124篇 |
2013年 | 128篇 |
2012年 | 120篇 |
2011年 | 130篇 |
2010年 | 96篇 |
2009年 | 62篇 |
2008年 | 104篇 |
2007年 | 86篇 |
2006年 | 75篇 |
2005年 | 87篇 |
2004年 | 64篇 |
2003年 | 64篇 |
2002年 | 51篇 |
2001年 | 23篇 |
2000年 | 17篇 |
1999年 | 20篇 |
1998年 | 13篇 |
1997年 | 5篇 |
1996年 | 9篇 |
1995年 | 10篇 |
1994年 | 9篇 |
1993年 | 10篇 |
1992年 | 20篇 |
1991年 | 18篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1983年 | 6篇 |
1982年 | 9篇 |
1980年 | 9篇 |
1976年 | 6篇 |
1974年 | 11篇 |
1973年 | 11篇 |
1972年 | 5篇 |
1971年 | 6篇 |
1970年 | 10篇 |
1969年 | 5篇 |
1965年 | 4篇 |
The level of phospholipid in the parasite was always higher than in its hosts. Phospholidyl choline and phosphatidyl ethanolamine constituted about 65% of the total phospholipid of Cuscuta. This was followed by phosphatidyl inositol (ca 20%) and phosphatidyl glycerol (ca 12%). Phosphatidic acid constituted only ca 3% of the phospholipids of Cuscuta. Although the total phospholipid levels of various host plants were not affected as a result of the infection by Cuscuta, a significant decrease occurred in the levels of phosphatidyl eholine and phosphatidyl ethanolamine as well as marked increases in phosphatidyl inositol and phosphatidic acid. The infected tissue showed an increase in phospholipase D activity as compared with the controls. The results have been discussed in relation to changes in permeability of the infected tissue. 相似文献
The use of azide dextrose broth, modified by the incorporation of bromthymol blue, and of ethyl violet azide broth as presumptive and confirmation tests, respectively, were found to be highly specific for the detection and enumeration of enterococci in these samples. Tetrazolium agar medium, when used as a third step after the confirmation test, provides a reliable differentiation of Streplococcus faecalis types from other group D streptococci. A simple procedure is described for further identification of S. faecalis varieties and other enterococcal species.
Incidence of biotypes within certain species is noted and relationships of these subgroups to the organisms described by other workers is discussed.
The striking resistance of all group D streptococci to dihydrostreptomycin and polymyxin B seems to offer promise for evolving a new selective medium for these organisms.
相似文献