全文获取类型
收费全文 | 235155篇 |
免费 | 14369篇 |
国内免费 | 122篇 |
出版年
2018年 | 7734篇 |
2017年 | 7606篇 |
2016年 | 6163篇 |
2015年 | 2418篇 |
2014年 | 3007篇 |
2013年 | 4252篇 |
2012年 | 7034篇 |
2011年 | 12107篇 |
2010年 | 9246篇 |
2009年 | 8788篇 |
2008年 | 10415篇 |
2007年 | 12190篇 |
2006年 | 4919篇 |
2005年 | 5476篇 |
2004年 | 5328篇 |
2003年 | 5522篇 |
2002年 | 5433篇 |
2001年 | 8513篇 |
2000年 | 8771篇 |
1999年 | 6316篇 |
1998年 | 1994篇 |
1997年 | 2054篇 |
1996年 | 1822篇 |
1993年 | 1702篇 |
1992年 | 5209篇 |
1991年 | 5387篇 |
1990年 | 5144篇 |
1989年 | 5132篇 |
1988年 | 4733篇 |
1987年 | 4496篇 |
1986年 | 4077篇 |
1985年 | 4236篇 |
1984年 | 3422篇 |
1983年 | 2930篇 |
1982年 | 1946篇 |
1981年 | 1728篇 |
1980年 | 1718篇 |
1979年 | 3214篇 |
1978年 | 2551篇 |
1977年 | 2279篇 |
1976年 | 2084篇 |
1975年 | 2560篇 |
1974年 | 2884篇 |
1973年 | 2803篇 |
1972年 | 3238篇 |
1971年 | 2916篇 |
1970年 | 2122篇 |
1969年 | 2022篇 |
1968年 | 1906篇 |
1967年 | 1743篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
891.
I H?nes 《Zeitschrift für allgemeine Mikrobiologie》1983,23(3):163-171
Comparative studies on the activities of isocitrate lyase (ICL) and malate synthase (MS) were carried out with Saccharomycopsis lipolytica incubating the yeast on media with different carbon sources. When cells were incubated in minimal medium with glucose, the activities of both enzymes were very low. In contrast, in minimal medium with acetate enhanced enzyme activities could be demonstrated. It is probably that the synthesis of ICL is repressed in presence of glucose. Furthermore the activity of ICL was inhibited by tricarboxylic acid cycle intermediates like succinic acid and oxalacetic acid. It was concluded that the syntheses of enzymes are derepressed. When cells of Sm. lipolytica were incubated in minimal medium with acetate, a high enzyme activity is evident. Synthesis of ICL on acetate was inhibited by cycloheximide and actinomycin D. The results were discussed comparing them with data obtained from other organisms. 相似文献
892.
893.
894.
895.
Earlier we have revealed in Djungarian hamster DM-15 cells three chromosomal segments (2p22, 5p1, 7q23-25) that are specific for transposition of amplified mdr1 genes from the site of location of resident gene copy (it was mapped to 4q21-23). In situ hybridization revealed in wild type cells no mdr1 homologous sequences in all these three segments. In this work we studied distribution of chromosomal breakages induced in DM-15 cells by aphidicolin, 5-fluorodeoxyuridine or N-phosphonacetyl-L-aspartate. The data obtained indicate that two of above mentioned segments. 2p22 and 7q23-25, contain no fragile sites. So, specificity of these segments for the transposition of amplified mdr1 genes is not due to their particular instability or to the presence in them of sequences homologous to amplifiable selectable gene. 相似文献
896.
897.
898.
The postnatal induction of serine dehydratase in rat liver 总被引:4,自引:0,他引:4
899.
The incidence of postoperative deep vein thrombosis diagnosed by radioisotope scanning in 100 Sudanese patients aged 40 or over was 12%. This compares with an incidence of nearly 30% in 542 patients reported from British hospitals using the same diagnostic technique. The reason for the difference is obscure and needs further investigation. 相似文献
900.