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31.
S X Zhang T Kobayashi T Okada E García del Saz H Seguchi 《Histology and histopathology》1991,6(3):309-315
The cerium-based method was used to demonstrate cytochemically the ultrastructural localization of alkaline phosphatase (ALPase), 5'-nucleotidase (5'-Nase) and magnesium-dependent adenosine triphosphatase (Mg-ATPase) on the transitional epithelium of the rat urinary bladder. The reaction product for ALPase was found on the plasma membrane of all epithelial cells, except the luminal surface of superficial cells. The activity of 5'-Nase appeared on the plasma membrane of all bladder transitional epithelial cells, including the free surface of superficial cells. The Mg-ATPase reaction product was seen on the plasma membrane of superficial, intermediate and basal cells, but never on the luminal surface of superficial cells and it was only occasionally seen on the basal surface. The possible functions of these phosphatases have been discussed, and it was emphasized that the 5'-Nase activity present on the luminal surface of superficial cells may play a special role in the membrane movement of these cells in the transitional epithelium. 相似文献
32.
The peptide antibiotic microcin B17 induces double-strand cleavage of DNA mediated by E. coli DNA gyrase. 总被引:15,自引:0,他引:15
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Microcin B17 (MccB17) is a bactericidal peptide antibiotic which inhibits DNA replication. Two Escherichia coli MccB17 resistant mutants were isolated and the mutations were shown to map to 83 min of the genetic map. Cloning of the mutations and Tn5 insertional analysis demonstrated that they were located inside gyrB. The approximate location of the mutations within gyrB was determined by constructing hybrid genes, as a previous step to sequencing. Both mutations were shown to consist of a single AT----GC transition at position 2251 of the gene, which produces a Trp751----Arg substitution in the amino acid sequence of the GyrB polypeptide. The inhibitory effect of MccB17 on replicative cell-free extracts was assayed. In this in vitro system, interaction of MccB17 with a component of the extracts induced double-strand cleavage of plasmid DNA. In vivo treatment with MccB17 also induced a well-defined cleavage pattern on chromosomal DNA. These effects were not observed with a MccB17-resistant, gyrB mutant. Altogether, our results indicate that MccB17 blocks DNA gyrase by trapping an enzyme-DNA cleavable complex. Thus, the mode of action of this peptide antibiotic resembles that of quinolones and a variety of antitumour drugs currently used in cancer chemotherapy. MccB17 is the first peptide shown to inhibit a type II DNA topoisomerase. 相似文献
33.
Manuela C. Koch Kenneth Ricker Michael Otto Tiemo Grimm Klaus Bender Barbara Zoll Peter S. Harper Frank Lehmann-Horn Reinhardt Rüdel Eric P. Hoffman 《Human genetics》1991,88(1):71-74
Summary Paramyotonia congenita (PC), an autosomal dominant non-progressive muscle disorder, is characterised by cold-induced stiffness followed by muscle weakness. The weakness is caused by a dysfunction of the sodium channel in muscle fibre. Parts of the gene coding for the -subunit of the sodium channel of the adult human skeletal muscle (SCN4A) have been localised on chromosome 17. To investigate the role of this gene in the etiology of PC, a linkage analysis in 17 well-defined families was carried out. The results (z=20.61, =0.001) show that the mutant gene responsible for the disorder is indeed tightly linked to the SCN4A gene. The mutation causing hyperkalemic periodic paralysis (HyperPP) with myotonia has previously been mapped to this gene locus by the same candidate gene approach. Thus, our data suggest that PC and HyperPP are caused by allelic mutations at a single locus on chromosome 17.Dedicated to Professor P. E. Becker on the occasion of his 83rd birthday. 相似文献
34.
G Pontoni C Manna A Salluzzo L del Piano P Galletti M De Rosa V Zappia 《Biochimica et biophysica acta》1985,836(2):222-232
In order to elucidate the reaction mechanism and the substrate-binding sites, CDPcholine:1,2-diacylglycerol cholinephosphotransferase (EC 2.7.8.2), prepared from rat liver microsomal fraction, has been subjected to kinetic analysis and substrate specificity studies. Kinetic evidence supports the hypothesis of a Bi-Bi sequential mechanism, involving a direct nucleophilic attack of diacylglycerol on CDPcholine during the reaction. To investigate the substrate requirements for recognition and catalysis, several CDPcholine analogs, modified in the nitrogen base or in the sugar or in the pyrophosphate bridge, have been synthesized, characterized and assayed as substrates and/or inhibitors of the reaction. The amino group on the pyrimidine ring, the 2'-alcoholic function of the ribose moiety as well as the pyrophosphate bridge have been identified as critical sites for enzyme-substrates interactions. 相似文献
35.
W Bandlow U Schwarz G R?del G Strobel C Wachter 《Biological chemistry Hoppe-Seyler》1985,366(6):545-553
We have isolated a cAMP-binding protein from highly purified yeast mitochondria by affinity chromatography. It is a lipophilic protein of molecular mass 45 000 Da, which is tightly membrane-bound and localized on the outer surface of the inner membrane. It can be solubilized in active form under mild conditions. The cAMP receptor resembles mitochondrial RNA polymerase prepared as described by Levens et al. [(1981) J. Biol. Chem. 256, 1474] in a surprisingly large number of properties including molecular mass. Comparison of the two proteins revealed that the polypeptide previously considered as RNA polymerase is, in fact, a mitochondrial cAMP receptor protein. 相似文献
36.
Influenza virus-specific RNA has been synthesized in vitro, using cytoplasmic or microsomal fractions of influenza virus-infected MDCK cells. The RNA polymerase activity was stimulated 5-30 times by priming with ApG. About 20-30% of the product was polyadenylated. Most of the in vitro product was of positive polarity, as shown by hybridization to strand specific probes and by T1 fingerprinting of the poly(A)+ and poly(A)- RNA segments encoding haemagglutinin and nucleoprotein. The size of poly(A)- RNA segments, determined on sequencing gels, was indistinguishable from that of virion RNA, whereas poly(A)+ RNA segments contain poly(A) tails approximately 50 nucleotides long. The size of in vitro synthesized RNA segments was also determined by gel electrophoresis of S1-treated double-stranded RNAs, obtained by hybridization of poly(A)+ or poly(A)- RNA fractions with excess of unlabelled virion RNA. The results of these experiments indicate that poly(A)- RNA contains full-length complementary RNA. This conclusion is further substantiated by the presence of additional oligonucleotides in the T1 fingerprints of in vitro synthesized poly(A)- haemagglutinin or nucleoprotein RNA, selected by hybridization to cloned DNA probes corresponding to the 3' termini of the genes. 相似文献
37.
Suppressor mutations identify box9 as a central nucleotide sequence in the highly ordered structure of intron RNA in yeast mitochondria. 总被引:3,自引:0,他引:3
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Data presented here lend support to the notion that RNA splicing in yeast mitochondria depends on the formation of hybrid structures involving the well-conserved intron sequences box9 and box2. Starting with the cis-dominant splicing-defective box2 mutant G2590, a G----A transition, we isolated a revertant having a mitochondrial second site suppressor mutation, which restores splicing competence in the presence of the original mutation. Sequence analysis reveals that the suppressor mutation is a C----T transition in box9(5' part). This second mutation compensates for the first one in box2 and restores a box2/box9(5') hybrid. Combined with previous data demonstrating an interaction of the adjacent sequence box9(3' part) with the upstream box9c sequence in intron 4, the central role of box9 in the formation of the intron 4, the central role of box9 in the formation of the intron 4 RNA high order structure becomes evident. 相似文献
38.
Screening of plasmids in non-pathogenic corynebacteria 总被引:1,自引:0,他引:1
H. Sandoval G. del Real L.M. Mateos A. Aguilar J.F. Martín 《FEMS microbiology letters》1985,27(1):93-98
Abstract A screening of plasmids in 25 nonpathogenic coryneform bacteria was carried out. 11 Strains showed at least one plasmid, ranging in size from 4.2 to 55 kb. These plasmids did not encode bacteriocin production or resistance to a number of antibiotics or to ions such as arsenite, mercury(II) and cobalt(II). A detailed study of plasmid pBL100 from Brevibacterium linens is presented. pBL100 has a size of 7.75 kb, and contains single sites for the endonucleases: Hin dIII; Pst I, Bgl II, Eco RI and Bam HI. B. linens is easily and efficiently transformed with vectors derived from pBL1 isolated from Brevibacterium lactofermentum . 相似文献
39.
Freeze etching studies in a symbiotic and a freeliving strain of Chroococcidiopsis revealed a specific layer in the outer cell wall not described so far from Cyanophyta. The layer showed a complex organisation: The main unit are ribbons, 2–3 nm thick, striated at right angle to the longitudinal axis. They are interwoven to a patchwork-like leaflet. The ribbons are virtually composed of globular particles associated in parallel rows. The cytoplasmic membrane and the cell walls of the symbiotic and the free-living strain were compared.Abbreviations cm
cytoplasmic membrane
- CW 1,2,3
cell wall layer 1,2,3
- EF
exoplasmic fracture face
- PF
protoplasmic fracture face 相似文献
40.
Dr. Lucas del Castillo Agudo 《Current microbiology》1985,12(1):41-44
We developed a method of hybrid selection between homothallic wild-type and heterothallic strains. The hybrids obtained were used to study the heredity of ethanol tolerance and production. Both characters segregated independently, but no ethanol-sensitive strains were able to produce high levels of ethanol. At least four genes are implicated in ethanol tolerance. 相似文献