全文获取类型
收费全文 | 799篇 |
免费 | 106篇 |
国内免费 | 1篇 |
出版年
2020年 | 9篇 |
2018年 | 12篇 |
2017年 | 7篇 |
2016年 | 12篇 |
2015年 | 19篇 |
2014年 | 14篇 |
2013年 | 33篇 |
2012年 | 31篇 |
2011年 | 24篇 |
2010年 | 24篇 |
2009年 | 19篇 |
2008年 | 24篇 |
2007年 | 24篇 |
2006年 | 21篇 |
2005年 | 37篇 |
2004年 | 44篇 |
2003年 | 13篇 |
2002年 | 34篇 |
2001年 | 24篇 |
2000年 | 25篇 |
1999年 | 36篇 |
1998年 | 11篇 |
1997年 | 13篇 |
1996年 | 13篇 |
1995年 | 14篇 |
1994年 | 15篇 |
1993年 | 12篇 |
1992年 | 19篇 |
1991年 | 14篇 |
1990年 | 20篇 |
1989年 | 33篇 |
1988年 | 15篇 |
1987年 | 10篇 |
1986年 | 13篇 |
1985年 | 15篇 |
1984年 | 17篇 |
1983年 | 10篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1978年 | 9篇 |
1976年 | 13篇 |
1975年 | 8篇 |
1973年 | 6篇 |
1972年 | 9篇 |
1971年 | 8篇 |
1970年 | 7篇 |
1969年 | 9篇 |
1967年 | 5篇 |
1966年 | 5篇 |
1962年 | 5篇 |
排序方式: 共有906条查询结果,搜索用时 390 毫秒
131.
132.
133.
Hugh H. Weir 《BMJ (Clinical research ed.)》1904,2(2283):863-864
134.
135.
J O Boles R J Cisneros M S Weir J D Odom J E Villafranca R B Dunlap 《Biochemistry》1991,30(46):11073-11080
Replacement of methionine (Met) residues by selenomethionine (SeMet) was recently shown to facilitate the crystallographic analysis of protein structure through the application of multi-wavelength anomalous diffraction techniques [Yang et al. (1990) Science (Washington, D.C.) 249, 1398-1405]. The availability of SeMet-containing proteins provides an excellent opportunity to evaluate the effects of the complete replacement of Met by SeMet. We chose to compare the properties of selenomethionyl thymidylate synthase isolated from Escherichia coli DL41 (a methionine auxotroph) and wild-type (wt) enzyme obtained from E. coli Rue10. An improved purification procedure for thymidylate synthase was developed which permitted the isolation of 25 mg of pure protein from 2 g of E. coli in 90% yield in no more than 8 h. The pure wt and SeMet enzymes exhibited specific activities 40% higher than published values. Thermal stability studies at 30 degrees C in degassed buffer showed that the SeMet enzyme (t1/2 67 h) was 8-fold less stable than wt enzyme (t1/2 557 h). The half-lives for the latter enzymes in nondegassed buffers at 30 degrees C were decreased by 2-fold, thus indicating the sensitivity of the enzyme to dissolved oxygen. Both enzymes exhibited essentially the same kinetic and binding properties, including Km(dUMP) (1.2 x 10(-6) M), specificity constant (1.6 x 10(6) s-1 M-1), and Kd for 5-fluorodeoxyuridylate binding (1.2 nM) in covalent inhibitory ternary complexes. In addition, X-ray crystallographic analysis by difference Fourier synthesis showed there was no significant difference in conformation between the SeMet enzyme and the wt enzyme. 相似文献
136.
137.
138.
139.
Inhibition of Helicobacter pylori haemagglutination activity by human salivary mucins 总被引:1,自引:0,他引:1
A Mentis L Tzouvelekis C Spiliadis C C Blackwell D M Weir 《FEMS microbiology immunology》1990,2(3):125-127
Thirty isolates of Helicobacter pylori from gastric biopsies agglutinated human erythrocyte suspensions. Crude mucin preparations derived from saliva of 20 different donors were examined for their ability to inhibit haemagglutination. All mucin preparations exhibited strong inhibitory activity. Removal of sialic residues from mucin preparations by treatment with neuraminidase resulted in a substantial reduction of their inhibitory activity. The mucin preparations had no bactericidal or aggregation activity for H. pylori. These results are discussed in the context of the role of mucins in colonization of the gastric mucosa by H. pylori. 相似文献
140.