全文获取类型
收费全文 | 696篇 |
免费 | 72篇 |
国内免费 | 1篇 |
专业分类
769篇 |
出版年
2022年 | 9篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2018年 | 6篇 |
2017年 | 8篇 |
2016年 | 16篇 |
2015年 | 31篇 |
2014年 | 38篇 |
2013年 | 35篇 |
2012年 | 42篇 |
2011年 | 53篇 |
2010年 | 24篇 |
2009年 | 24篇 |
2008年 | 30篇 |
2007年 | 30篇 |
2006年 | 45篇 |
2005年 | 33篇 |
2004年 | 24篇 |
2003年 | 26篇 |
2002年 | 34篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 14篇 |
1998年 | 18篇 |
1997年 | 11篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 15篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 11篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1974年 | 7篇 |
1973年 | 3篇 |
1970年 | 8篇 |
1969年 | 4篇 |
1968年 | 3篇 |
排序方式: 共有769条查询结果,搜索用时 15 毫秒
761.
762.
763.
764.
765.
766.
767.
Angelo C. Pinto Paul M. Baker Benjamin Gilbert Richard Pinchin Francisco A.M. Reis Magda S. Waineraich Dorothea H.T. Zocher 《Phytochemistry》1980,19(11):2486-2487
The isolation of (20R)-20-hydroxy-24-methylenedammar-3-one from Vellozia stipitata is described. 相似文献
768.
Simon Messner Matthias Altmeyer Hongtao Zhao Andrea Pozivil Bernd Roschitzki Peter Gehrig Dorothea Rutishauser Danzhi Huang Amedeo Caflisch Michael O. Hottiger 《Nucleic acids research》2010,38(19):6350-6362
The chromatin-associated enzyme PARP1 has previously been suggested to ADP-ribosylate histones, but the specific ADP-ribose acceptor sites have remained enigmatic. Here, we show that PARP1 covalently ADP-ribosylates the amino-terminal histone tails of all core histones. Using biochemical tools and novel electron transfer dissociation mass spectrometric protocols, we identify for the first time K13 of H2A, K30 of H2B, K27 and K37 of H3, as well as K16 of H4 as ADP-ribose acceptor sites. Multiple explicit water molecular dynamics simulations of the H4 tail peptide into the catalytic cleft of PARP1 indicate that two stable intermolecular salt bridges hold the peptide in an orientation that allows K16 ADP-ribosylation. Consistent with a functional cross-talk between ADP-ribosylation and other histone tail modifications, acetylation of H4K16 inhibits ADP-ribosylation by PARP1. Taken together, our computational and experimental results provide strong evidence that PARP1 modifies important regulatory lysines of the core histone tails. 相似文献
769.
The rfbkpO1 gene cluster of Klebsiella pneumoniae O1 directs synthesis of the D-galactan I component of the lipopolysaccharide O-antigen. The first two genes in the rfbkpO1cluster encode RrfbkpO1and RfbBKpO1, with predicted sizes of 29.5 or 30.0 kDa and 27.4 kDa, respectively. RfbBKpO1 contains a consensus ATP-binding domain and shares homology with several proteins which function as ATP-binding components of cell surface polysaccharide transporters. RfbAKpO1 is predicted to be an integral membrane protein with five putative membrane-spanning domains and its transmembrane topology was confirmed by TnphoA mutagenesis. The hydropathy plot of RfbAKpO1 resembles KpsM, the transcytoplasmic membrane component of the capsular polysaccharide transporter from Escherichia coli K-1 and K-5. These relationships suggest that RfbAKpO1 and RfbBKpO1 belong to a family of two-component ABC (ATP-binding cassette) transporters. E. coli K-12 containing a plasmid carrying an rfbKpO1 gene cluster deleted in rfbAKpO1 and rfbBKpO1 expresses rough lipopolysaccharide molecules on its surface and accumulates cytoplasmic O-antigen. When RfbAKpO1 and RfbBKpO1 are supplied in trans by a compatible plasmid, O-polysaccharide transport is restored and smooth D-galactan l-substituted lipopolysaccharide is produced. RfbAKpO1 and RfbBKpO1 are, therefore, proposed to constitute a system required for transport of D-galactan I across the cytoplasmic membrane, where RfbAKpO1 represents the membrane-spanning translocator and RfbBKpO1 couples the energy of ATP hydrolysis to the transport process. 相似文献