全文获取类型
收费全文 | 420篇 |
免费 | 37篇 |
专业分类
457篇 |
出版年
2022年 | 4篇 |
2021年 | 9篇 |
2019年 | 3篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 11篇 |
2014年 | 13篇 |
2013年 | 26篇 |
2012年 | 24篇 |
2011年 | 21篇 |
2010年 | 12篇 |
2009年 | 17篇 |
2008年 | 12篇 |
2007年 | 26篇 |
2006年 | 19篇 |
2005年 | 17篇 |
2004年 | 17篇 |
2003年 | 23篇 |
2002年 | 24篇 |
2001年 | 11篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 9篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1968年 | 2篇 |
1965年 | 2篇 |
1964年 | 2篇 |
1963年 | 3篇 |
1960年 | 2篇 |
排序方式: 共有457条查询结果,搜索用时 0 毫秒
1.
2.
Acquisition of the heat-shock response and thermotolerance during early development of Xenopus laevis 总被引:10,自引:0,他引:10
The ability to synthesize a 68,000- to 70,000-Da protein (hsp) in heat-shocked early Xenopus laevis embryos is dependent on the stage of development. Whereas late blastula and later stage embryos synthesize hsp68-70 after heat shock, cleavage stages are incompetent with respect to hsp synthesis. In vitro translation experiments and RNA blot analyses demonstrate that enhanced synthesis of hsp68-70 is associated with an accumulation of hsp68-70 mRNA. Examination of the effect of heat shock on preexisting actin mRNA reveals that heat shock promotes a reduction in the levels of actin mRNA in cleavage embryos but has no discernible effect on actin mRNA levels in neurula embryos. Finally, the acquisition of the heat-shock response (i.e., synthesis of hsp68-70 and accumulation of hsp70 mRNA) during early Xenopus development is correlated with the acquisition of thermotolerance. 相似文献
3.
Dilip M. Shah Cathy M. Hironaka Roger C. Wiegand Elizabeth I. Harding Gwen G. Krivi David C. Tiemeier 《Plant molecular biology》1986,6(4):203-211
Summary We have used the cDNA clone encoding maize glutathione-S-transferase (GST I) to isolate a genomic DNA clone containing the complete GST I gene. Nucleotide sequence analysis of the cDNA and genomic clones has yielded a complete amino acid sequence for maize GST I and provided the exon-intron map of its gene. The mRNA homologous sequences in the maize GST I gene consist of a 107 bp 5 untranslated region, a 642 bp coding region and 340 bp of the 3 untranslated region. They are divided into three exons by two introns which interrupt the coding region. The 5 untranslated spacer contains an unusual sequence of pentamer AGAGG repeated seven times. The inbred maize line (Missouri 17) contains a single gene for GST I, whereas the hybrid line (3780A) contains two genes. Nucleotide sequence analysis of the primer extended cDNA products reveals that the 5 untranslated regions of the two genes in the hybrid 3780A are identical except for a 6 bp internal deletion (or insertion). The amino acid sequence of maize GST I shares no apparent sequence homology with the published sequences of animal GST's and represents the first published sequence of a plant GST. re]19850813 ac]19851126 相似文献
4.
5.
6.
7.
David O. Lambeth Gwen R. Ericson Mark A. Yorek Paul D. Ray 《Biochimica et Biophysica Acta (BBA)/General Subjects》1982,719(3):501-508
The influences of buffers and iron chelators on the rate of autoxidation of Fe2+ were examined in the pH range 6.0–7.4. The catalysis by Fe2+ and Fe3+ of the autoxidation of dithiothreitol was also investigated. In buffers which are non- or poor chelators of iron, 0.25 mM Fe2+, and 0.3 mM dithiothreitol when present with iron, oxidize within minutes at pH 7.4 and 30°C. The stability of each increases as the pH is decreased and more than 90% of each remains after 1 h at pH 6.0. In the presence of buffers or oxy-ligands which preferentially and strongly chelate Fe3+ over Fe2+, Fe2+ autoxidizes rapidly in the pH range 6.0–7.4 while dithiothreitol is protected. Ligands which preferentially bind strongly to Fe2+ stabilize both Fe2+ and dithiothreitol at pH 7.4. Dithiothreitol readily reduces Fe3+ in non-chelating buffers or in the presence of strong chelators of Fe2+, however, the ferrous ions produced are prone to reoxidation at higher pH values. These results show that Fe2+ and dithiothreitol are very susceptible to autoxidation in the neutral pH range, and that the rates are strongly influenced by the presence of chelators of Fe2+ and Fe3+. The rapid autoxidations of these species need to be taken into account when designing and interpreting experiments involving Fe2+ or both dithiothreitol and iron. 相似文献
8.
9.
10.
Reduced-median-network analysis of complete mitochondrial DNA coding-region sequences for the major African, Asian, and European haplogroups 总被引:38,自引:0,他引:38 下载免费PDF全文
Herrnstadt C Elson JL Fahy E Preston G Turnbull DM Anderson C Ghosh SS Olefsky JM Beal MF Davis RE Howell N 《American journal of human genetics》2002,70(5):1152-1171
The evolution of the human mitochondrial genome is characterized by the emergence of ethnically distinct lineages or haplogroups. Nine European, seven Asian (including Native American), and three African mitochondrial DNA (mtDNA) haplogroups have been identified previously on the basis of the presence or absence of a relatively small number of restriction-enzyme recognition sites or on the basis of nucleotide sequences of the D-loop region. We have used reduced-median-network approaches to analyze 560 complete European, Asian, and African mtDNA coding-region sequences from unrelated individuals to develop a more complete understanding of sequence diversity both within and between haplogroups. A total of 497 haplogroup-associated polymorphisms were identified, 323 (65%) of which were associated with one haplogroup and 174 (35%) of which were associated with two or more haplogroups. Approximately one-half of these polymorphisms are reported for the first time here. Our results confirm and substantially extend the phylogenetic relationships among mitochondrial genomes described elsewhere from the major human ethnic groups. Another important result is that there were numerous instances both of parallel mutations at the same site and of reversion (i.e., homoplasy). It is likely that homoplasy in the coding region will confound evolutionary analysis of small sequence sets. By a linkage-disequilibrium approach, additional evidence for the absence of human mtDNA recombination is presented here. 相似文献