全文获取类型
收费全文 | 5024篇 |
免费 | 564篇 |
出版年
2022年 | 41篇 |
2021年 | 73篇 |
2020年 | 46篇 |
2019年 | 49篇 |
2018年 | 62篇 |
2017年 | 69篇 |
2016年 | 112篇 |
2015年 | 172篇 |
2014年 | 176篇 |
2013年 | 269篇 |
2012年 | 280篇 |
2011年 | 321篇 |
2010年 | 200篇 |
2009年 | 170篇 |
2008年 | 241篇 |
2007年 | 230篇 |
2006年 | 210篇 |
2005年 | 197篇 |
2004年 | 195篇 |
2003年 | 184篇 |
2002年 | 200篇 |
2001年 | 115篇 |
2000年 | 103篇 |
1999年 | 116篇 |
1998年 | 60篇 |
1997年 | 49篇 |
1996年 | 67篇 |
1995年 | 54篇 |
1994年 | 58篇 |
1993年 | 61篇 |
1992年 | 65篇 |
1991年 | 55篇 |
1990年 | 70篇 |
1989年 | 87篇 |
1988年 | 56篇 |
1987年 | 41篇 |
1986年 | 46篇 |
1985年 | 49篇 |
1984年 | 50篇 |
1983年 | 41篇 |
1982年 | 50篇 |
1981年 | 40篇 |
1980年 | 37篇 |
1979年 | 49篇 |
1977年 | 35篇 |
1976年 | 50篇 |
1975年 | 33篇 |
1974年 | 52篇 |
1973年 | 42篇 |
1971年 | 33篇 |
排序方式: 共有5588条查询结果,搜索用时 78 毫秒
11.
12.
Background
Micro-biological research relies on the use of model organisms that act as representatives of their species or subspecies, these are frequently well-characterized laboratory strains. However, it has often become apparent that the model strain initially chosen does not represent important features of the species. For micro-organisms, the diversity of their genomes is such that even the best possible choice of initial strain for sequencing may not assure that the genome obtained adequately represents the species. To acquire information about a species' genome as efficiently as possible, we require a method to choose strains for analysis on the basis of how well they represent the species. 相似文献13.
Medical examiners in Nova Scotia recently attended their first-ever seminar concerning the skills, challenges and techniques their jobs require. It was welcomed by the physicians, most of whom are family physicians with little training in the investigation of sudden death. 相似文献
14.
15.
16.
The cyanobacterium Anabaena cylindrica B629 was suspended in small glass beds and incubated in a gas-tight glass vessel outdoors under a gas atmosphere comprising carbon monoxide (0.2%), acetylene (5%), oxygen (6.5%), and nitrogen. The solution phase initially contained sodium bicarbonate (10mM) at pH 7. Under these conditions the organism continuously produced hydrogen gas for over three weeks. The temperature of the culture was maintained below 30°C and minimum night temperatures were recorded. The vessel was covered by a shadecloth, which reduced the natural illumination by approximately 70%. The system is an alternative to those requiring the strict absence of oxygen and little nitrogen, and requires virtually no attention during the incubation period. 相似文献
17.
A new family of 2-hydroxyacid dehydrogenases 总被引:5,自引:0,他引:5
G A Grant 《Biochemical and biophysical research communications》1989,165(3):1371-1374
The NADH-dependent hydroxypyruvate reductase from cucumber and the pdxB gene product of E. coli display significant homology to E. coli D-3-phosphoglycerate dehydrogenase. In contrast, these proteins do not display much similarity with other oxidoreductases or with other 2-hydroxyacid dehydrogenases in particular. On the basis of their relatedness and the structure of their substrates, these three enzymes constitute a new family of 2-hydroxyacid dehydrogenases distinct from malate and lactate dehydrogenase. 相似文献
18.
Grant Jewell Rich 《American anthropologist》2001,103(1):266-267
Varieties of Anomalous Experience: Examining the Scientific Evidence. Etzel Cardeña. Steven Jay Lynn. and Stanley Krippner. eds. Washington, DC: American Psychological Association, 2000. 476 pp. 相似文献
19.
20.