全文获取类型
收费全文 | 112篇 |
免费 | 9篇 |
国内免费 | 2篇 |
专业分类
123篇 |
出版年
2023年 | 1篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 6篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 8篇 |
2012年 | 5篇 |
2011年 | 6篇 |
2010年 | 12篇 |
2009年 | 10篇 |
2008年 | 7篇 |
2007年 | 1篇 |
2006年 | 5篇 |
2005年 | 5篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 2篇 |
1999年 | 1篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 4篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1975年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有123条查询结果,搜索用时 15 毫秒
51.
Loknath Gidijala Roel AL Bovenberg Paul Klaassen Ida J van der Klei Marten Veenhuis Jan AKW Kiel 《BMC biotechnology》2008,8(1):29
Background
β-Lactams like penicillin and cephalosporin are among the oldest known antibiotics used against bacterial infections. Industrially, penicillin is produced by the filamentous fungus Penicillium chrysogenum. Our goal is to introduce the entire penicillin biosynthesis pathway into the methylotrophic yeast Hansenula polymorpha. Yeast species have the advantage of being versatile, easy to handle and cultivate, and possess superior fermentation properties relative to filamentous fungi. One of the fundamental challenges is to produce functionally active enzyme in H. polymorpha. 相似文献52.
To understand the evolution of duplicate genes, we compared rates of
nucleotide substitution between 17 pairs of nonallelic duplicated genes in
the tetraploid frog Xenopus laevis with rates between the orthologous loci
of human and rodent. For all duplicated X. laevis genes, the number of
synonymous substitutions per site (dS) was greater than the number of
nonsynonymous substitutions per site (dN), indicating that these genes are
subject to purifying selection. There was also a significant positive
correlation (r = 0.915) between dN for the X. laevis genes and dN for the
mammalian genes, suggesting that, at the amino acid level, the X. laevis
genes and the mammalian genes are under similar constraints. Results of
relative-rate tests showed nearly equal rates of nonsynonymous substitution
in each copy of the X. laevis genes; apparently there are similar
constraints on both copies. No correlation was found between dS for the X.
laevis genes and dS for the mammalian genes. There was a significant
positive correlation both between members of pairs of duplicated X. laevis
genes (r = 0.951) and between human and rodent orthologues (r = 0.854) with
respect to third- position G+C content but no such relationship between the
X. laevis genes and either of their mammalian orthologues. The results
indicate that both copies of a duplicate gene can be subject to purifying
selection and thus support the hypothesis of selection against all
genotypes containing a null allele at either of two duplicate loci.
相似文献
53.
54.
Rapid evolution of immunoglobulin superfamily C2 domains expressed in immune system cells 总被引:6,自引:3,他引:3
To test the hypothesis that proteins expressed in cells of the vertebrate
immune system evolve unusually rapidly, 107 orthologous immunoglobulin C2
domains were compared between human and murine rodent. The analysis showed
that the rate of nonsynonymous (amino-acid- altering) nucleotide
substitution in these domains was correlated with factors associated with
protein structure and with breadth of tissue expression, as well as with
the rate of synonymous substitution. However, when such factors were
controlled for statistically, there remained a strong positive association
between expression in the immune system and nonsynonymous rate, with the
highest rates being seen in genes expressed in the immune system only.
Certain immune system genes are known to be subject to positive selection
favoring diversity at the amino acid level; most of these genes encode
receptors that interact directly with foreign antigens. The observed
acceleration of the rate of nonsynonymous evolution in C2 domains of immune
system proteins may be explained by either (1) reduced constraint at the
amino acid level on molecules interacting with immune system receptors that
are themselves evolving rapidly due to positive diversifying selection or
(2) positive selection favoring amino acid changes correlated with changes
in the immune system receptors.
相似文献
55.
56.
OMAR HAMARSHEH WOLFGANG PRESBER ZIAD ABDEEN SAMER SAWALHA AHMAD AL‐LAHEM GABRIELE SCHOENIAN 《Molecular ecology resources》2006,6(3):826-828
Phlebotomus papatasi is a proven vector of Leishmania major which is one of the causative agents of cutaneous leishmaniasis in the Old World. Although it has a wide geographical range, its population structure is not yet well understood. In an effort to better understand the population dynamics of this vector, we developed a panel of di‐ and trinucleotide microsatellite markers, using a magnetic bead hybridization enrichment protocol. These microsatellite loci showed three to seven alleles with an expected heterozygosity range between 0.702 and 0.876. The level of polymorphisms found in this study suggests that these microsatellite loci can be used for population analysis of P. papatasi. 相似文献
57.
LIQIONG LI WEIBO SONG KHALED A. S. AL‐RASHEID ALAN WARREN ZICONG LI YUAN XU CHEN SHAO 《Zoological Journal of the Linnean Society》2010,158(2):231-243
The morphology and morphogenesis of a new marine hypotrichous ciliate Pseudoamphisiella elongata sp. nov. isolated from mussel‐farming waters near Qingdao, China, are described based on living and protargol‐impregnated specimens. Morphologically, the new species can be distinguished from its known congeners by its elongate body shape, narrow oral field, having fewer dorsal kineties and caudal cirri, more marginal cirri, and differentiated pretransverse cirri. The identification as a new species is firmly supported by the sequences of the small subunit ribosomal rRNA (SSU rRNA) gene, compared with other known Pseudoamphisiella species, and the phylogenetic analysis. The morphogenetic characteristics can be summarized as follows: (1) the parental adoral zone of membranelles and undulating membranes are entirely rebuilt by the oral primordium, which develops de novo in the outermost region of the cortex; (2) the oral primordium in the opisthe and the frontoventral–transverse (FVT) anlagen in both dividers are formed independently on the cell surface; (3) an ‘extra’ marginal anlage originates to the right of the right marginal anlage, and develops into two or three ‘extra’ marginal cirri; (4) the FVT anlagen develop in the primary mode, and the last FVT streak contributes two migratory cirri (frontoterminal cirri), which are probably resorbed; (5) the right marginal anlagen in both dividers occur close together, independent of the old structure. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158 , 231–243. 相似文献
58.
Global expression analysis of nucleotide binding site-leucine rich repeat-encoding and related genes in Arabidopsis 总被引:1,自引:0,他引:1
Xiaoping Tan Blake C Meyers Alexander Kozik Marilyn AL West Michele Morgante Dina A St Clair Andrew F Bent Richard W Michelmore 《BMC plant biology》2007,7(1):56
Background
Nucleotide binding site-leucine rich repeat (NBS-LRR)-encoding genes comprise the largest class of plant disease resistance genes. The 149 NBS-LRR-encoding genes and the 58 related genes that do not encode LRRs represent approximately 0.8% of all ORFs so far annotated in Arabidopsis ecotype Col-0. Despite their prevalence in the genome and functional importance, there was little information regarding expression of these genes. 相似文献59.
Julie A Pattemore James K Hane Angela H Williams Bree AL Wilson Ben J Stodart Gavin J Ash 《BMC genomics》2014,15(1)
Background
Metarhizium anisopliae is an important fungal biocontrol agent of insect pests of agricultural crops. Genomics can aid the successful commercialization of biopesticides by identification of key genes differentiating closely related species, selection of virulent microbial isolates which are amenable to industrial scale production and formulation and through the reduction of phenotypic variability. The genome of Metarhizium isolate ARSEF23 was recently published as a model for M. anisopliae, however phylogenetic analysis has since re-classified this isolate as M. robertsii. We present a new annotated genome sequence of M. anisopliae (isolate Ma69) and whole genome comparison to M. robertsii (ARSEF23) and M. acridum (CQMa 102).Results
Whole genome analysis of M. anisopliae indicates significant macrosynteny with M. robertsii but with some large genomic inversions. In comparison to M. acridum, the genome of M. anisopliae shares lower sequence homology. While alignments overall are co-linear, the genome of M. acridum is not contiguous enough to conclusively observe macrosynteny. Mating type gene analysis revealed both MAT1-1 and MAT1-2 genes present in M. anisopliae suggesting putative homothallism, despite having no known teleomorph, in contrast with the putatively heterothallic M. acridum isolate CQMa 102 (MAT1-2) and M. robertsii isolate ARSEF23 (altered MAT1-1). Repetitive DNA and RIP analysis revealed M. acridum to have twice the repetitive content of the other two species and M. anisopliae to be five times more RIP affected than M. robertsii. We also present an initial bioinformatic survey of candidate pathogenicity genes in M. anisopliae.Conclusions
The annotated genome of M. anisopliae is an important resource for the identification of virulence genes specific to M. anisopliae and development of species- and strain- specific assays. New insight into the possibility of homothallism and RIP affectedness has important implications for the development of M. anisopliae as a biopesticide as it may indicate the potential for greater inherent diversity in this species than the other species. This could present opportunities to select isolates with unique combinations of pathogenicity factors, or it may point to instability in the species, a negative attribute in a biopesticide.Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-15-660) contains supplementary material, which is available to authorized users. 相似文献60.
Katrijn Van Deun Age K Smilde Mariët J van der Werf Henk AL Kiers Iven Van Mechelen 《BMC bioinformatics》2009,10(1):246-15