全文获取类型
收费全文 | 591篇 |
免费 | 65篇 |
出版年
2023年 | 5篇 |
2021年 | 16篇 |
2020年 | 11篇 |
2019年 | 10篇 |
2018年 | 8篇 |
2017年 | 8篇 |
2016年 | 15篇 |
2015年 | 21篇 |
2014年 | 25篇 |
2013年 | 37篇 |
2012年 | 37篇 |
2011年 | 32篇 |
2010年 | 33篇 |
2009年 | 20篇 |
2008年 | 25篇 |
2007年 | 12篇 |
2006年 | 15篇 |
2005年 | 16篇 |
2004年 | 16篇 |
2003年 | 17篇 |
2002年 | 18篇 |
2001年 | 11篇 |
2000年 | 19篇 |
1999年 | 9篇 |
1998年 | 13篇 |
1997年 | 12篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 10篇 |
1990年 | 17篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 11篇 |
1986年 | 11篇 |
1985年 | 18篇 |
1984年 | 4篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1979年 | 7篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1973年 | 4篇 |
1969年 | 5篇 |
1968年 | 3篇 |
1966年 | 3篇 |
1964年 | 3篇 |
1957年 | 4篇 |
排序方式: 共有656条查询结果,搜索用时 31 毫秒
1.
2.
3.
Growth characteristics of a thermotolerant methylotrophic Bacillus sp. (NCIB 12522) in batch culture
Nader Al-Awadhi Thomas Egli Geoffrey Hamer 《Applied microbiology and biotechnology》1988,29(5):485-493
Summary This contribution deals with problems associated with the culture of a thermotolerant methylotrophic Bacillus sp. The results reported clearly demonstrate why conventional enrichment/isolation procedures have, in the past, failed to allow such microbes to assert themselves. The catastrophic effect of carbon substrate (methanol) exhaustion on such cultures is clearly evidenced, but the effects of other nutrient exhaustion or limitations are demonstrated to be markedly less stringent. The failure of such cultures to complete the sporulation process when growing on methanol has important consequences with respect to their survival characteristics. 相似文献
4.
5.
Jan Wensink Hans Hoeve Ingrid Mertens Zur Borg Cornelis J. A. Van Den Hamer 《Biological trace element research》1989,22(1):55-62
Zinc has been shown to effect--in vitro--a number of processes associated with neurotransmission. We have tested whether the rate of impulse conduction--in vivo--as measured from the latencies of auditory brainstem responses (ABR), is influenced by dietary zinc deficiency in the rat. Dietary zinc deficiency for up to 26 wk had no effect on the wave I-IV interval compared to zinc-adequate fed animals. The results are discussed in relation to the observed constancy of brain overall and extracellular fluid zinc concentrations under conditions of dietary zinc deficiency. 相似文献
6.
A R Thrower J Byrd E B Tarbet R K Mehra D H Hamer D R Winge 《The Journal of biological chemistry》1988,263(15):7037-7042
Metallothioneins have been isolated from Saccharomyces cerevisiae CUP1 mutants generated by Wright et al. (Wright, C. F., Hamer, D. H., and McKenney, K. (1986) Nucleic Acids Res. 14, 8489-8499). In the mutant metallothioneins, pairs of cysteinyl residues have been converted to seryl residues. The mutant proteins differ only in the positions of the double substitutions; each mutant molecule contains 10 cysteinyl residues. Each mutant protein lacks the first 8 residues at the amino terminus from the decoded gene sequence of the CUP1 locus. Mutant molecules consist of 53 residues analogous to the wild-type metallothionein and are designated 9/11, 24/26, 36/38, and 49/50 (in reference to the sequence positions of the Cys----Ser conversions). The properties of the mutant metallothioneins are vastly different, and host cells harboring the different plasmid-encoded mutant molecules show marked differences in sensitivity to CuSO4. Growth inhibition was observed at CuSO4 concentrations up to mM in cells containing the 9/11, 24/26, and 36/38 molecules, but not for cells containing protein 49/50. A CuSO4 concentration of 5 mM was required to inhibit the growth of yeast containing either 49/50 or the wild-type metallothionein. In the purified proteins the copper binding stoichiometry of each molecule, except protein 24/26, was nearly 8 mol eq. Protein 24/26 bound 5.5 copper ions/molecule. The Cu(I) chelator bathocuproine disulfonate reacted with over 50% of the copper ions in proteins 9/11, 24/26, and 36/38, but less than 10% of the copper ions in proteins 49/50 and wild-type metallothionein were reactive. The thiolates in 9/11, 24/26, and 36/38 were also more reactive in a disulfide exchange reaction with dithiodipyridine compared with the sulfhydryls in 49/50 and the wild-type molecules. The four mutant copper proteins are luminescent and exhibit a similar quantum yield. The cluster structures contributing to the particular electronic transitions are markedly more sensitive to oxygen in proteins 9/11, 24/26, and 36/38 compared with 49/50 and the wild-type molecules. The air-sensitive proteins exhibit a tertiary fold not recognized by polyclonal antibodies directed to a conformational epitope on yeast Cu-metallothionein. Protein 49/50 cross-reacts with the antibody in a concentration-dependent fashion similar to the wild-type protein. Mutation of 2 cysteinyl residues in the carboxyl portion of metallothionein does not significantly alter properties of the molecule, whereas mutation of several cysteines in the amino-terminal portion of the molecule yields a different conformation. 相似文献
7.
H. Meulenaar C. J. A. van den Hamer T. S. G. A. M. van den Ingh T. M. W. Stolk 《Biological trace element research》1985,7(1):49-54
Was studied in vitro. The109Cd-labeled protein was isolated by gel filtration and incubated with a lysosomal extract from the same source. No degradation was seen when the pH of the incubation medium was 5 or higher, whereas the degradation of Cd-thionein was completed in 2 h at a pH of 4.5. Dissociation of Cd2+ from thionein, which takes place to a fair extent at a pH below 5, appears necessary before the enzymatic breakdown of the thionein moiety can take place. 相似文献
8.
9.
Male Leeds rats were fed a diet containing 0.05% of the non-carcinogen 4-acetylaminofluorene (4-AAF) for 8–10 months. They were then returned to a normal diet and their pancreatic tissues examined by electron microscopy at intervals between 2 and 12 months after the end of 4-AAF treatment. 4-AAF was found to induce a persistent alteration in the morphology of the granular endoplasmic reticulum, involving distortion and dilatation of the cisternae. In some respects this lesion resembles that which is induced by the carcinogenic isomer, 2-acetylaminofluorene (2-AAF). 相似文献
10.