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21.
Kenji Yamamoto Kohji Kusano Noriko K. Takahashi Hiroshi Yoshikura Ichizo Kobayashi 《Molecular & general genetics : MGG》1992,234(1):1-13
Summary Gene conversion - apparently non-reciprocal transfer of sequence information between homologous DNA sequences - has been reported in various organisms. Frequent association of gene conversion with reciprocal exchange (crossing-over) of the flanking sequences in meiosis has formed the basis of the current view that gene conversion reflects events at the site of interaction during homologous recombination. In order to analyze mechanisms of gene conversion and homologous recombination in an Escherichia coli strain with an active RecF pathway (recBC sbcBC), we first established in cells of this strain a plasmid carrying two mutant neo genes, each deleted for a different gene segment, in inverted orientation. We then selected kanamycin-resistant plasmids that had reconstituted an intact neo
+ gene by homologous recombination. We found that all the neo
+ plasmids from these clones belonged to the gene-conversion type in the sense that they carried one neo
+ gene and retained one of the mutant neo genes. This apparent gene conversion was, however, only very rarely accompanied by apparent crossing-over of the flanking sequences. This is in contrast to the case in a rec
+ strain. or in a strain with an active RecE pathway (recBC sbcA). Our further analyses, especially comparisons with apparent gene conversion in the rec
+ strain, led us to propose a mechanism for this biased gene conversion. This successive half crossing-over model proposes that the elementary recombinational process is half crossing;-over in the sense that it generates only one recombinant DNA duplex molecule, and leaves one or two free end(s), out of two parental DNA duplexes. The resulting free end is, the model assumes, recombinogenic and frequently engages in a second round of half crossing-over with the recombinant duplex. The products resulting from such interaction involving two molecules of the plasmid would be classified as belonging to the gene-conversion type without crossing-over. We constructed a dimeric molecule that mimics the intermediate form hypothesized in this model and introduced it into cells. Biased gene conversion products were obtained in this reconstruction experiment. The half crossing-over mechanism can also explain formation of huge linear multimers of bacterial plasmids, the nature of transcribable recombination products in bacterial conjugation, chromosomal gene conversion not accompanied by flanking exchange (like that in yeast mating-type switching), and antigenic variation in microorganisms. 相似文献
22.
Dai Kitamoto Takashi Nakane Noriko Nakao Tadaatsu Nakahara Takeshi Tabuchi 《Applied microbiology and biotechnology》1992,36(6):768-772
Summary
Candida antarctica strain T-34, which was isolated as a biosurfactant producer, was found to produce organic acids and polyols extracellularly but not to produce biosurfactants, when grown on glucose or other carbohydrates as the sole carbon source. It was also observed microscopically that the strain contained oil globules within the cells. The intracellular lipids of the strain mainly consisted of triglycerides and mannosylerythritol lipids (MEL). The MEL content of the cells during the culture exceeded 10% of the dry cell weight, and the pattern of variation of the MEL content was very similar to that of triglycerides. All three stock strains of C. antarctica tested also accumulated a relatively large amount of MEL from glucose. These results suggested that these strains accumulated the MEL intracellularly as one of the storage materials together with triglycerides.Offprint requests to: D. Kitamoto 相似文献
23.
Michael C. Iannuzzi Robert C. Stern Francis S. Collins Catherine Tom Hon Noriko Hidaka Theresa Strong Lisa Becker Mitchell L. Drumm Marga B. White Bernard Gerrard Michael Dean 《American journal of human genetics》1991,48(2):227-231
Cystic fibrosis (CF) is a recessive disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. We have identified in exon 7 two frameshift mutations, one caused by a two-nucleotide insertion and the other caused by a one-nucleotide deletion; these mutations--CF1154insTC and CF1213delT, respectively, are predicted to shift the reading frame of the protein and to introduce UAA(ochre) termination codons at residues 369 and 368. 相似文献
24.
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26.
Noriyuki Muranushi Noriko Takagi Shozo Muranishi Hitoshi Sezaki 《Chemistry and physics of lipids》1981,28(3):269-279
The effect of fatty acids and monoglycerides on barrier properties of liposomal membranes prepared from egg phosphatidylcholine was investigated. The incorporation of these lipids as liposomal membrane components induced the alteration of the permeability to less permeable liposomally entrapped drugs, sulfanilic acid and procainamide ethobromide (PAEB). Monoolein caused greatly increased permeability of both drugs and unsaturated fatty acids markedly enhanced the release rate of PAEB, while saturated fatty acids caused a small increase in the release rate.Electron spin resonance (ESR) investigation with 5-nitroxide stearic acid showed that fatty acids disordered the hydrophobic region of the lipid bilayer and the disordering effect of unsaturated fatty acids was greater than that of saturated ones. It was demonstrated that the incorporated fatty acids and monoglycerides interacted with the polar region of the membranes by ESR study with cholestane label and 1H-NMR study. These results indicated that the increase in the membrane permeability caused by fatty acids and monoglycerides associated with the disorder in the membranes' interior and the interaction of the incorporated lipid with the polar head group of phospholipid. 相似文献
27.
Saccharomycodes ludwigii, supposed to be petite-negative, gave rise to respiration-deficient mutants when acriflavine and ultraviolet irradiation, respectively, were applied to this yeast, strain IFO 1194. The frequency of such mutants was very low as compared with that in Saccharomyces cerevisiae and other petite-positive yeasts. Cytochrome composition was characterized by spectrophotometry at the temperature of liquid nitrogen. The respiratory mutants examined contained cytochrome c unaltered in quality and quantity. Cytochrome b was often present only in small amounts though never absent, while cytochrome a+a3 was either present or absent. The respiratory mutants could form zygotes after conjugation with a wild-type culture of opposite mating type ( vs. a). The hybridization and segregation analysis of spore tetrads showed the inheritance of respiratory mutant character to be either Mendelian or non-Mendelian and similar to that of pet (nuclear) and rho- (cytoplasmic) mutants, respectively, in Saccharomyces cerevisiae. 相似文献
28.
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30.
Shin-ichi Miyoshi Katsumi Sugiyama Hiroshi Furuta Noriko Miyoshi Sumio Shinoda 《FEMS microbiology letters》1986,34(3):301-304
Abstract Vibrio vulnificus protease (VVP) stimulated histamine release from isolated mast cells in a dose- and temperature-dependent manner within a range of 0.2–4.0 μ g/0.5 ml. Histamine release was accompanied by degranulation, and no leakage of lactate dehydrogenase from cells was observed, indicating that the histamine release was not due to cytolysis but to exocytosis. This release, completed within 30 s at 37°C, suggested that the mechanism of action of VVP on mast cells is different from that of other proteases, such as trypsin or α-chymotrypsin, which release histamine from the cells slowly. 相似文献