全文获取类型
收费全文 | 120篇 |
免费 | 60篇 |
出版年
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2009年 | 3篇 |
2008年 | 1篇 |
2006年 | 2篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 9篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 12篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1972年 | 1篇 |
1971年 | 7篇 |
1970年 | 3篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1967年 | 4篇 |
1966年 | 1篇 |
1964年 | 2篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1934年 | 1篇 |
排序方式: 共有180条查询结果,搜索用时 31 毫秒
1.
Jeff A Johnson Heather RL Lerner Pamela C Rasmussen David P Mindell 《BMC evolutionary biology》2006,6(1):65-12
Background
Populations of the Oriental White-backed Vulture (Gyps bengalensis) have declined by over 95% within the past decade. This decline is largely due to incidental consumption of the non-steroidal anti-inflammatory veterinary pharmaceutical diclofenac, commonly used to treat domestic livestock. The conservation status of other Gyps vultures in southern Asia is also of immediate concern, given the lack of knowledge regarding status of their populations and the continuing existence of taxonomic uncertainties. In this study, we assess phylogenetic relationships for all recognized species and the majority of subspecies within the genus Gyps. The continuing veterinary use of diclofenac is an unknown but potential risk to related species with similar feeding habits to Gyps bengalensis. Therefore, an accurate assessment of the phylogenetic relationships among Gyps vultures should aid in their conservation by clarifying taxonomic uncertainties, and enabling inference of their respective relatedness to susceptible G. bengalensis. 相似文献2.
3.
Molecular Evolution and Nucleotide Sequences of the Maize Plastid Genes for the α Subunit of Cf1 (atpA) and the Proteolipid Subunit of Cf0 (atpH)
下载免费PDF全文
![点击此处可从《Genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The nucleotide sequences of the maize plastid genes for the alpha subunit of CF1 (atpA) and the proteolipid subunit of CF0 (atpH) are presented. The evolution of these genes among higher plants is characterized by a transition mutation bias of about 2:1 and by rates of synonymous and nonsynonymous substitution which are much lower than similar rates for genes from other sources. This is consistent with the notion that the plastid genome is evolving conservatively in primary sequence. Yet, the mode and tempo of sequence evolution of these and other plastid-encoded coupling factor genes are not the same. In particular, higher rates of nonsynonymous substitution in atpE (the gene for the epsilon subunit of CF1) and higher rates of synonymous substitution in atpH in the dicot vs. monocot lineages of higher plants indicate that these sequences are likely subject to different evolutionary constraints in these two lineages. The 5'- and 3'-transcribed flanking regions of atpA and atpH from maize, wheat and tobacco are conserved in size, but contain few putative regulatory elements which are conserved either in their spatial arrangement or sequence complexity. However, these regions likely contain variable numbers of "species-specific" regulatory elements. The present studies thus suggest that the plastid genome is not a passive participant in an evolutionary process governed by a more rapidly changing, readily adaptive, nuclear compartment, but that novel strategies for the coordinate expression of genes in the plastid genome may arise through rapid evolution of the flanking sequences of these genes. 相似文献
4.
Chloroplast DNA replication in vitro: site-specific initiation from preferred templates. 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
An enzyme system prepared from maize chloroplasts catalyzes the synthesis of DNA from maize chloroplast DNA sequences cloned in bacterial plasmids. Cloned maize chloroplast DNA fragments Bam HI 17' (2470 bp) and Eco RI x (1368 bp) have been shown to be preferred templates for in vitro DNA synthesis catalyzed by pea chloroplast DNA polymerase preparations [Gold et al. (1987) Proc. Natl. Acad. Sci. USA 84, 194-198]. Analysis of replicative intermediates indicates that although the template activity of the recombinant plasmid pZmcBam 17' is substantially greater than that of the pZmcEco x, replication in both cases originates from within a 455 bp region which overlaps the two plasmids. The remaining approximately 1500 basepair portion of maize chloroplast BamHI fragment 17' is not more active because it contains additional origins for replication. The overlapping region shows sequence homology with a portion of the Chlamydomonas reinhardtii chloroplast chromosome that contains a replication origin. Replication is shown to proceed bidirectionally within the 455 bp origin region. Recombinant plasmid pZmc 427, which is also active in the in vitro DNA synthesis assay, promoted localized replication initiation within a 1 kbp Bg1II-Eco RI fragment of the chloroplast DNA insert, a region that includes the 3' terminal part of the psbA gene. 相似文献
5.
6.
7.
Maize chloroplast RNA polymerase: the 78-kilodalton polypeptide is encoded by the plastid rpoC1 gene. 总被引:5,自引:0,他引:5
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The 180-, 120- and 38-kDa polypeptides found in highly purified maize plastid RNA polymerase preparations are encoded by the maize plastid genes rpoC2, rpoB, and rpoA, respectively [Hu, J. and Bogorad, L. (1990) Proc. Natl. Acad. Sci. USA. 87, pp. 1531-1535]. These genes have segments that specify amino acid sequences homologous to those of E. coli RNA polymerase subunits. The plastid gene products are designated b", b and a, respectively. We report here that the amino-terminal amino acid sequence of a 78-kDa polypeptide also found in highly purified maize plastid RNA polymerase preparations matches precisely the sequence deduced from the maize plastid rpoC1 gene which has segments homologous to the 5' end of the E. coli rpoC gene. Thus, the 78-kDa polypeptide is likely to be a functional component of maize plastid DNA-dependent RNA polymerase. This polypeptide is designated subunit b'. Three polypeptides unrelated to RNA polymerase have also been identified in this preparation. 相似文献
8.
Protein PSII-G. An additional component of photosystem II identified through its plastid gene in maize 总被引:5,自引:0,他引:5
A A Steinmetz M Castroviejo R T Sayre L Bogorad 《The Journal of biological chemistry》1986,261(6):2485-2488
An unidentified open reading frame, 248 or 255 amino acids in length, on the maize chloroplast DNA fragment Bam5 was sequenced. It encodes a protein which contains a high proportion of hydrophilic amino acids, of which 22% are hydroxylated, interrupted by hydrophobic domains. A synthetic peptide corresponding to a hydrophilic sequence was used to generate antibodies. Western blots of photosystem I and II complexes prepared from maize and spinach thylakoids indicate that the psbG gene product is a membrane-associated protein of the photosystem II complex that migrates as a 24-kDa species on polyacrylamide gel electrophoresis. 相似文献
9.
10.
Regulation by copper of the expression of plastocyanin and cytochrome c552 in Chlamydomonas reinhardi. 总被引:18,自引:1,他引:17
下载免费PDF全文
![点击此处可从《Molecular and cellular biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Plastocyanin and cytochrome c552 are interchangeable electron carriers in the photosynthetic electron transfer chains of some cyanobacteria and green algae (P. M. Wood, Eur. J. Biochem. 87:9-19, 1978; G. Sandmann et al., Arch. Microbiol. 134:23-27, 1983). Chlamydomonas reinhardi cells respond to the availability of copper in the medium and accordingly accumulate either plastocyanin (if copper is available) or cytochrome c552 (if copper is not available). The response occurs in both heterotrophically and phototrophically grown cells. We have studied the molecular level at which this response occurs. No immunoreactive polypeptide is detectable under conditions where the mature protein is not spectroscopically detectable. Both plastocyanin and cytochrome c552 appear to be translated (in vitro) from polyadenylated mRNA as precursors of higher molecular weight. RNA was isolated from cells grown either under conditions favorable for the accumulation of plastocyanin (medium with Cu2+) or for the accumulation of cytochrome c552 (without Cu2+ added to the medium). Translatable mRNA for preapoplastocyanin was detected in both RNA preparations, although mature plastocyanin was detected in C. reinhardi cells only when copper was added to the culture. Translatable mRNA for preapocytochrome, on the other hand, was detected only in cells grown under conditions where cytochrome c552 accumulates (i.e., in the absence of copper). We conclude that copper-mediated regulation of plastocyanin and cytochrome c552 accumulation is effected at different levels, the former at the level of stable protein and the latter at the level of stable mRNA. 相似文献