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111.
Prion protein gene sequence of Canada's first non-imported case of bovine spongiform encephalopathy (BSE). 总被引:2,自引:0,他引:2
Michael B Coulthart Rhonda Mogk Jason M Rancourt Deborah L Godal Stefanie Czub 《Génome》2003,46(6):1005-1009
In May 2003, Canada became the 22nd country outside of the United Kingdom to report a case of bovine spongiform encephalopathy (BSE) in an animal not known to be imported from a country with cattle previously affected by this fatal, transmissible prion disease. Despite extensive testing of thousands of other animals that may have been exposed to contaminated feed at the same time as the affected animal, no evidence has been found for other infections. This finding leaves room for conjectures that the single confirmed case arose spontaneously, perhaps (by analogy with human Creutzfeldt-Jakob disease) as a result of a somatic protein misfolding event or a novel germline mutation. Here we present DNA sequence data from the affected animal's prion protein coding sequence that argue definitively against the latter hypothesis. 相似文献
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Embryonic stem cell gene targeting using bacteriophage lambda vectors generated by phage-plasmid recombination. 下载免费PDF全文
Targeted mutagenesis is an extremely useful experimental approach in molecular medicine, allowing the generation of specialized animals that are mutant for any gene of interest. Currently the rate determining step in any gene targeting experiment is construction of the targeting vector (TV). In order to streamline gene targeting methods and avoid problems encountered with plasmid TVs, we describe the direct application of lambda phage in targeted mutagenesis. The recombination-proficient phage vector lambda2TK permits generation of TVs by conventional restriction-ligation or recombination-mediated methods. The resulting lambdaTV DNA can then be cleaved with restriction endonucleases to release the bacteriophage arms and can subsequently be electroporated directly into ES cells to yield gene targets. We demonstrate that in vivo phage-plasmid recombination can be used to introduce neo and lacZ - neo mutations into precise positions within a lambda2TK subclone via double crossover recombination. We describe two methods for eliminating single crossover recombinants, spi selection and size restriction, both of which result in phage TVs bearing double crossover insertions. Thus TVs can be easily and quickly generated in bacteriophage without plasmid subcloning and with little genomic sequence or restriction site information. 相似文献
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On the origins of esterases 总被引:8,自引:0,他引:8
Comparisons among the primary sequences of five cloned eukaryotic esterases
reveal two distinct lineages, neither bearing any significant overall
sequence similarity to the functionally related serine protease multigene
family. We have not eliminated the possibility that the esterases may have
residual conformational similarities to the serine proteases. However, our
profile analysis and analyses of the predicted conformations of the
esterases reveal little similarity to the serine proteases. Four of the
esterase proteins share 27%-53% overall sequence similarity and evidence of
a catalytic mechanism involving the same Arg- Asp-Ser or His-Asp-Ser charge
relay. We propose that these four esterases, three of them cholinesterases,
form part of a multigene family essentially separate from the serine
proteases.
相似文献
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Bacillus thuringiensis subsp israelensis (Bti) and subsp kurstaki (Btk); (2) vegetative cells derived from these BT products; and (3) Gram-positive and Gram-negative bacteria used as controls.
The XTT-kinetic assay improved sensitivity and early reading of MIC breakpoints. The conventional colony count method for
determining minimal bactericidal concentration (MBC) was used to validate a multi-sample dot-blot assay in which organisms
in individual MIC assays are trapped free of residual antibiotic and their viability is estimated by in situ conversion of MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] to insoluble formazan. Tolerance (MBC/MIC)
for most antibiotics was low (≤4). Resistance to β-lactams was attributed to β-lactamase activity in both BT products and
cultures derived from them. MIC and MBC breakpoints in spore-based assays were also approximated by changes in genome copy,
using δ-endotoxin and β-lactamase genes as probes. The DNA assays are effective for monitoring and authenticating organisms
in microbe-containing biotechnology products.
Received 29 September 1998/ Accepted in revised form 12 February 1999 相似文献