全文获取类型
收费全文 | 1772篇 |
免费 | 147篇 |
国内免费 | 1篇 |
出版年
2021年 | 17篇 |
2020年 | 10篇 |
2019年 | 28篇 |
2018年 | 21篇 |
2017年 | 14篇 |
2016年 | 44篇 |
2015年 | 56篇 |
2014年 | 51篇 |
2013年 | 84篇 |
2012年 | 91篇 |
2011年 | 100篇 |
2010年 | 70篇 |
2009年 | 66篇 |
2008年 | 98篇 |
2007年 | 103篇 |
2006年 | 64篇 |
2005年 | 96篇 |
2004年 | 82篇 |
2003年 | 82篇 |
2002年 | 79篇 |
2001年 | 39篇 |
2000年 | 59篇 |
1999年 | 54篇 |
1998年 | 20篇 |
1997年 | 26篇 |
1996年 | 19篇 |
1995年 | 19篇 |
1994年 | 11篇 |
1993年 | 20篇 |
1992年 | 23篇 |
1991年 | 16篇 |
1990年 | 28篇 |
1989年 | 21篇 |
1988年 | 20篇 |
1987年 | 19篇 |
1986年 | 20篇 |
1985年 | 12篇 |
1984年 | 14篇 |
1983年 | 16篇 |
1982年 | 11篇 |
1980年 | 13篇 |
1979年 | 16篇 |
1978年 | 13篇 |
1974年 | 14篇 |
1973年 | 9篇 |
1971年 | 17篇 |
1970年 | 12篇 |
1969年 | 10篇 |
1968年 | 13篇 |
1967年 | 12篇 |
排序方式: 共有1920条查询结果,搜索用时 31 毫秒
1.
2.
Background
In heterogeneous environments, sex-biased dispersal could lead to environmental adaptive parental effects, with offspring selected to perform in the same way as the parent dispersing least, because this parent is more likely to be locally adapted. We investigate this hypothesis by simulating varying levels of sex-biased dispersal in a patchy environment. The relative advantage of a strategy involving pure maternal (or paternal) inheritance is then compared with a strategy involving classical biparental inheritance in plants and in animals. 相似文献3.
4.
Effect of propionate and pyruvate on citrulline synthesis and ATP content in rat liver mitochondria.
L Cathelineau F P Petit F X Coudé P P Kamoun 《Biochemical and biophysical research communications》1979,90(1):327-332
Propionate inhibits citrullinogenesis when succinate (plus rotenone) or glutamate are the oxidizable substrates used. Propionate decreases the intramitochondrial concentration of carbamylphosphate by decreasing the ATP content. When the energy supply for citrullinogenesis is provided by an influx of exogenous ATP, propionate is no longer an inhibitor. Pyruvate inhibits citrullinogenesis with glutamate but not with succinate (plus rotenone) as oxidizable substrates. Propionate and pyruvate deplete mitochondrial ATP but probably by different mechanisms. 相似文献
5.
An abnormal terminal X-Y interchange accounts for most but not all cases of human XX maleness 总被引:14,自引:0,他引:14
To determine if human XX maleness results from an abnormal chromosomal X-Y interchange, we studied the inheritance of the paternal pseudoautosomal region in nine patients. Those six patients in whom Y-specific DNA was found (Y(+)) inherited the entire pseudoautosomal region from the paternal Y chromosome and lost that of the paternal X chromosome. Moreover, in three Y(+) cases, we observed the deletion of a paternal Xp locus tightly linked to the pseudoautosomal region. These results definitively show that an abnormal and terminal X-Y interchange during paternal meiosis causes Y(+)XX maleness. In contrast, no abnormal X-Y interchange was observed in any of the three Y(-) cases analyzed, suggesting that maleness can occur in the absence of any Y-specific DNA. 相似文献
6.
Growth of B95-8 cells and expression of Epstein-Barr virus lytic phase in serum-free medium. 总被引:2,自引:2,他引:0
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Epstein-Barr virus (EBV)-transformed tamarin (Saguinus oedipus) cells (B95-8) were selected for growth in medium with reduced serum and then transferred to serum-free medium which consisted of RPMI 1640 supplemented with insulin, transferrin, and selenium. Serum-free cells in continuous passage for 1 year had a morphology, growth rate, and culture density which approached those of B95-8 cells grown with serum. The cells expressed virus-induced antigens, including the EBV-associated DNA polymerase. Cells exposed to EBV-inducing agents, n-butyric acid and phorbol 12-myristate-13-acetate, produced transforming virus with titers comparable to those of cultures grown with serum. These findings demonstrate that serum is neither required for the growth of B95-8 cells nor necessary for induction or full expression of the EBV lytic phase in these cells. 相似文献
7.
8.
Ion-Exchange Chromatography Separates Activities Synthesizing and Degrading Fructose 2,6-Bisphosphate from C3 and C4 Leaves but Not from Rat Liver 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Fructose-6-phosphate,2-kinase and fructose-2,6-bisphosphatase were separated on the basis of charge from leaves of C3 (spinach, lettuce, and pea) and C4 (sorghum and amaranthus) plants but not from rat liver—a tissue known to contain a bifunctional enzyme with both activities. [2-32P]Fructose 2,6-bisphosphate binding experiments also suggest that the major forms of these activities reside on different proteins in leaves. 相似文献
9.
Plasmid replication stimulates DNA recombination in Bacillus subtilis 总被引:23,自引:0,他引:23
The effects of plasmid replication on the frequency of homologous recombination have been investigated. For that purpose Bacillus subtilis strains that carry in their chromosome directly repeated DNA sequences, and an integrated copy of plasmid pE194 either proximal or distal to the repeats, were constructed. The repeat consists either of 3.9 X 10(3) base pBR322 sequences or 2.1 X 10(3) base B. subtilis chromosomal sequences. As plasmid pE194 is naturally thermosensitive for replication, the activity of the replicon could be regulated. Recombination between the repeated sequences was infrequent (about 10(-4) per generation) when the integrated plasmid did not replicate. It was 20 to 450 times higher when the plasmid was allowed to replicate, provided that the repeats were in the proximity of the plasmid. These results show that plasmid replication stimulates DNA recombination. 相似文献
10.