全文获取类型
收费全文 | 166篇 |
免费 | 21篇 |
专业分类
187篇 |
出版年
2016年 | 2篇 |
2014年 | 1篇 |
2013年 | 4篇 |
2012年 | 4篇 |
2011年 | 8篇 |
2010年 | 5篇 |
2009年 | 8篇 |
2008年 | 8篇 |
2007年 | 6篇 |
2006年 | 7篇 |
2005年 | 7篇 |
2004年 | 10篇 |
2003年 | 7篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 2篇 |
1972年 | 4篇 |
1970年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有187条查询结果,搜索用时 0 毫秒
181.
The Agrobacterium tumor-inducing (Ti) plasmid pTiT37 encodes nopaline synthase (NOS) gene (nos) with eukaryotic promoter elements that is expressed in transformed plant cells but not in the bacterial host. We have fused the nos gene to the Escherichia coli trp promoter, and observed synthesis of NOS in E. coli. The nopaline produced by this enzyme is excreted into the culture medium. NOS is enzymatically active at 30 degrees C but not 37 degrees C, as based on nopaline production. NOS protein is produced at both temperatures, based on production in minicells. 相似文献
182.
183.
A Gafni 《Biochemical and biophysical research communications》1979,86(2):285-292
The fluorescence decay mechanism of 1, N6-ethenoadenosine diphosphoribose bound to rabbit muscle glyceraldehyde 3-phosphate dehydrogenase markedly differs from that of the intact coenzyme analog (εNAD+) bound to the same enzyme. In the latter case the fluorescence is partially quenched by interactions between the ethenoadenine ring and amino acid residues in its binding site. Binding of the nicotinamide moiety of the coenzyme thus affects the relative orientation of the adenine ring within its binding site leading to the quenching interactions. The interactions of the adenine group with its binding site induce conformational changes in the enzyme which affect the binding of additional coenzyme molecules. The nicotinamide base thus determines, indirectly, the negative cooperativity found in NAD+ binding. 相似文献
184.
Abraham Novogrodsky Amiram Ravid Tova Glaser Albert L. Rubin Kurt H. Stenzel 《Experimental cell research》1982,139(2)
Transferrin can partially replace serum requirement for the mitogenic activity of both PHA and the oxidizing mitogen, neuraminidase and galactose oxidase, whereas several other proteins are inactive. Catalase enhances the potentiating effect of transferrin, indicating that transferrin stimulates hydrogen peroxide production by the cell preparations. Iron is required for transferrin to replace serum, since prior addition of desferrioxamine to medium or cell cultures eliminates the potentiating effect of transferrin on lymphocyte mitogenesis. In addition to the possibility that iron is required for nutritional purposes, transferrin-mediated activation of oxidative metabolism may have a stimulatory effect on lymphocyte activation. 相似文献
185.
186.
187.
1. The present study reexamines a previous notion on opioid stimulation of cyclic GMP (cGMP) formation and the retraction of the original findings.2. The effect of opioid agonists on cGMP accumulation in two cell lines of neuronal origin was measured. The proportion of cGMP stimulation in NG108-15 neuroblastoma × glioma hybrid cells resembled the proportion of [Ca2+]in elevation by opioids in this culture. The failure of opioids to stimulate cGMP formation in SK-N-SH human neuroblastoma coincided with the lack of cGMP stimulation by other Ca2+ mobilizing agents in these cells. The nitric oxide donor nitroprusside elevated cGMP in both cell lines.3. The implication of the opioid-Ca2+-NO-cGMP cellular pathway for opioid activity in vivo is discussed. 相似文献