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51.
A lymphoid-specific protein binding to the octamer motif of immunoglobulin genes 总被引:216,自引:0,他引:216
52.
Mutation rates differ among regions of the mammalian genome 总被引:91,自引:0,他引:91
In the traditional view of molecular evolution, the rate of point mutation is uniform over the genome of an organism and variation in the rate of nucleotide substitution among DNA regions reflects differential selective constraints. Here we provide evidence for significant variation in mutation rate among regions in the mammalian genome. We show first that substitutions at silent (degenerate) sites in protein-coding genes in mammals seem to be effectively neutral (or nearly so) as they do not occur significantly less frequently than substitutions in pseudogenes. We then show that the rate of silent substitution varies among genes and is correlated with the base composition of genes and their flanking DNA. This implies that the variation in both silent substitution rate and base composition can be attributed to systematic differences in the rate and pattern of mutation over regions of the genome. We propose that the differences arise because mutation patterns vary with the timing of replication of different chromosomal regions in the germline. This hypothesis can account for both the origin of isochores in mammalian genomes and the observation that silent nucleotide substitutions in different mammalian genes do not have the same molecular clock. 相似文献
53.
Expansion of a novel CAG trinucleotide repeat in the 5' region of PPP2R2B is associated with SCA12 总被引:9,自引:0,他引:9
54.
Sharp AJ Hansen S Selzer RR Cheng Z Regan R Hurst JA Stewart H Price SM Blair E Hennekam RC Fitzpatrick CA Segraves R Richmond TA Guiver C Albertson DG Pinkel D Eis PS Schwartz S Knight SJ Eichler EE 《Nature genetics》2006,38(9):1038-1042
Genomic disorders are characterized by the presence of flanking segmental duplications that predispose these regions to recurrent rearrangement. Based on the duplication architecture of the genome, we investigated 130 regions that we hypothesized as candidates for previously undescribed genomic disorders. We tested 290 individuals with mental retardation by BAC array comparative genomic hybridization and identified 16 pathogenic rearrangements, including de novo microdeletions of 17q21.31 found in four individuals. Using oligonucleotide arrays, we refined the breakpoints of this microdeletion, defining a 478-kb critical region containing six genes that were deleted in all four individuals. We mapped the breakpoints of this deletion and of four other pathogenic rearrangements in 1q21.1, 15q13, 15q24 and 17q12 to flanking segmental duplications, suggesting that these are also sites of recurrent rearrangement. In common with the 17q21.31 deletion, these breakpoint regions are sites of copy number polymorphism in controls, indicating that these may be inherently unstable genomic regions. 相似文献
55.
Sebaihia M Wren BW Mullany P Fairweather NF Minton N Stabler R Thomson NR Roberts AP Cerdeño-Tárraga AM Wang H Holden MT Wright A Churcher C Quail MA Baker S Bason N Brooks K Chillingworth T Cronin A Davis P Dowd L Fraser A Feltwell T Hance Z Holroyd S Jagels K Moule S Mungall K Price C Rabbinowitsch E Sharp S Simmonds M Stevens K Unwin L Whithead S Dupuy B Dougan G Barrell B Parkhill J 《Nature genetics》2006,38(7):779-786
We determined the complete genome sequence of Clostridium difficile strain 630, a virulent and multidrug-resistant strain. Our analysis indicates that a large proportion (11%) of the genome consists of mobile genetic elements, mainly in the form of conjugative transposons. These mobile elements are putatively responsible for the acquisition by C. difficile of an extensive array of genes involved in antimicrobial resistance, virulence, host interaction and the production of surface structures. The metabolic capabilities encoded in the genome show multiple adaptations for survival and growth within the gut environment. The extreme genome variability was confirmed by whole-genome microarray analysis; it may reflect the organism's niche in the gut and should provide information on the evolution of virulence in this organism. 相似文献
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58.
Characterization of the branch site in lariat RNAs produced by splicing of mRNA precursors 总被引:52,自引:0,他引:52
The branch site of lariat RNAs produced during the splicing of the first two late leader exons of adenovirus-2 has a structure of (formula; see text) There is a distinct complementarity between sequences preceding the adenosine at the branch site and the 5' terminus of the intervening sequence. 相似文献
59.
Synphilin-1 associates with alpha-synuclein and promotes the formation of cytosolic inclusions. 总被引:25,自引:0,他引:25
S Engelender Z Kaminsky X Guo A H Sharp R K Amaravi J J Kleiderlein R L Margolis J C Troncoso A A Lanahan P F Worley V L Dawson T M Dawson C A Ross 《Nature genetics》1999,22(1):110-114
Parkinson disease (PD) is a neurodegenerative disease characterized by tremor, bradykinesia, rigidity and postural instability. Post-mortem examination shows loss of neurons and Lewy bodies, which are cytoplasmic eosinophilic inclusions, in the substantia nigra and other brain regions. A few families have PD caused by mutations (A53T or A30P) in the gene SNCA (encoding alpha-synuclein). Alpha-synuclein is present in Lewy bodies of patients with sporadic PD, suggesting that alpha-synuclein may be involved in the pathogenesis of PD. It is unknown how alpha-synuclein contributes to the cellular and biochemical mechanisms of PD, and its normal functions and biochemical properties are poorly understood. To determine the protein-interaction partners of alpha-synuclein, we performed a yeast two-hybrid screen. We identified a novel interacting protein, which we term synphilin-1 (encoded by the gene SNCAIP). We found that alpha-synuclein interacts in vivo with synphilin-1 in neurons. Co-transfection of both proteins (but not control proteins) in HEK 293 cells yields cytoplasmic eosinophilic inclusions. 相似文献
60.
Fabrication of photonic crystals for the visible spectrum by holographic lithography 总被引:3,自引:0,他引:3
The term 'photonics' describes a technology whereby data transmission and processing occurs largely or entirely by means of photons. Photonic crystals are microstructured materials in which the dielectric constant is periodically modulated on a length scale comparable to the desired wavelength of operation. Multiple interference between waves scattered from each unit cell of the structure may open a 'photonic bandgap'--a range of frequencies, analogous to the electronic bandgap of a semiconductor, within which no propagating electromagnetic modes exist. Numerous device principles that exploit this property have been identified. Considerable progress has now been made in constructing two-dimensional structures using conventional lithography, but the fabrication of three-dimensional photonic crystal structures for the visible spectrum remains a considerable challenge. Here we describe a technique--three-dimensional holographic lithography--that is well suited to the production of three-dimensional structures with sub-micrometre periodicity. With this technique we have made microperiodic polymeric structures, and we have used these as templates to create complementary structures with higher refractive-index contrast. 相似文献