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1.
Nina I. Smirnova Galina V. Chekhovskaya Natalia I. Davidova Ludmila F. Livanova Galina A. Yeroshenko 《FEMS microbiology letters》1996,136(2):175-180
Abstract The presence of a temperate phage was demonstrated in a strain of Vibrio cholerae O139 isolated from a patient. Spontaneous variants with translucent colonies had lost this phage. The loss of the phage was associated with increased hydrophobicity, indicating the loss of the capsule. These clones were sensitive to serum bactericidal activity, showed decreased expression of such presumed virulence factors as proteases, motility and mannose-sensitive pili. Furthermore, excision of the phage made the strain dependent on purines for growth. 相似文献
2.
Total and polysome-bound ribosomes and the uptake and incorporation of3H-uridine and14C-leucine were examined in dividing microspores and in pollen grains isolated from anthers of 6 different developmental stages. Direct evidence was obtained that the formation of cytoplasm of the vegetative cell following microspore division is related to a rapid activation of RNA and protein synthesis and of ribosomes in differentiating pollen. Total ribosomes associated with gametophytic programme rose about 10times and the process of differentiation was accompanied by a rapid increase in uptake capacity of pollen grains for both uridine and leucine. Pollen development after cytoplasm synthesis and starch deposition continued by pollen maturation, which was characterized by a decline in RNA synthesis, dissociation of polysomes and by a further rise of transport activity of pollen grain wall for exogenous substrates, indicating probable pollen adaptation for utilization of metabolites from the degenerating tapetal cytoplasm. 相似文献
3.
Brenda S. Speer Ludmila Chistoserdova Mary E. Lidstrom 《FEMS microbiology letters》1994,121(3):349-355
Abstract A fragment of Methylobacter marinus A45 DNA has been cloned and sequenced, and an open reading frame has been identified that could code for a 46-kDa polypeptide. Comparison of the deduced amino acid sequence of the polypeptide against the protein data bank has revealed strong similarity with a number of alcohol dehydrogenases, with highest similarity towards class III alcohol dehydrogenases, which recently have been shown to be identical to glutathione-dependent formaldehyde dehydrogenases. We were unable to measure appreciable levels of NAD(P)-dependent formaldehyde dehydrogenases or alcohol dehydrogenase activities using aldehydes or primary or secondary alcohols in cell-free extracts from batch cultures of M. marinus A45. However, formaldehyde dehydrogenases activity was detected on zymograms. Our data suggest that, although NAD(P)-linked formaldehyde dehydrogenase or alcohol dehydrogenase activities are undetectable in cell-free extracts of most methylotrophs employing the ribulose monophosphate pathway for formaldehyde assimilation and dissimilation, the gene encoding formaldehyde dehydrogenase is present in M. marinus A45 and may be present in more of these organisms as well. 相似文献
4.
5.
J. Matoušek P. Dědič M. J. Beneš P. Kopáček Věra Turková Ludmila Trněná 《Biologia Plantarum》1990,32(6):460-473
A polyspecific antiserum against protein extracted from PSTV-infected tomato leaves was prepared and the IgGs were separated
by affinity chromatography on a beaded cellulose adsorbent with an immobilized “healthy” antigen. The antibody not adsorbed
entered into a preferential reaction with the antigen from PSTV-infected leaves as estimated by an enzyme-linked immunosorbent
assay. The immunochemical reactions did not significantly exceed the control background, if antigens from tomato leaves infected
with potato viruses X, Y and M were analyzed. By immunoblot technique we revealed, however, that several antigens not detected
in healthy leaves appeared in the leaves infected either with PSTV or with viruses X and M. An accumulation of a major antigen
having a molecular mass of about 70 kDa was observed in viroid-infected leaves only, suggesting the specificity for viroid
infection. The antigen was found not to be an alkaline endoproteinase - the pathogenesis-related protein P-69.
Some antigens with molecular masses approximately 38.0, 23.7 and 22 kDa, which occurred in PSTV-infected leaves and in healthy
calluses, were not detectable in PSTV-infected calluses.
No reaction exceeding the control level was observed using enzyme-linked immunosorbent assay for antigens from silver nitrate-treated
tomato leaves, although such leaves showed symptoms similar to that caused by viroids. 相似文献
6.
Nitrate reductase (NR) induction is enhanced by exogenously supplied sucrose in excised pea roots exposed to both exogenous nitrate and exogenous nitrite. NR synthesis is preferentially supported by sugars transported to the cells at the moment, however NR induction can take place for some time without exogenous sugar influx if roots are saturated with sugars during precultivation. Steady high NR levels are dependent on steady sugar and nitrate influxes. NR induction is low in roots precultivated for 20 h without sucrose although sugar content is still high in them. This suggests that compartmentation of sugars in the cells is of major importance during NR induction. Total nitrate content in roots exposed to nitrate is not influenced by sucrose supplied together with nitrate. Some nitrite is oxidized to nitrate in roots exposed to exogenous nitrite ; we assume that this nitrate is responsible for NR induction. Our results indicate that sugars, besides many indirect effects on NR induction, may also directly influence NR synthesis either as coinducers or as derepressors of NR synthesis. Our results further show that NR is not a product-inducible enzyme. 相似文献
7.
Distribution of Tetrahydromethanopterin-Dependent Enzymes in Methylotrophic Bacteria and Phylogeny of Methenyl Tetrahydromethanopterin Cyclohydrolases 下载免费PDF全文
Julia A. Vorholt Ludmila Chistoserdova Sergei M. Stolyar Rudolf K. Thauer Mary E. Lidstrom 《Journal of bacteriology》1999,181(18):5750-5757
The methylotrophic proteobacterium Methylobacterium extorquens AM1 possesses tetrahydromethanopterin (H(4)MPT)-dependent enzymes, which are otherwise specific to methanogenic and sulfate-reducing archaea and which have been suggested to be involved in formaldehyde oxidation to CO(2) in M. extorquens AM1. The distribution of H(4)MPT-dependent enzyme activities in cell extracts of methylotrophic bacteria from 13 different genera are reported. H(4)MPT-dependent activities were detected in all of the methylotrophic and methanotrophic proteobacteria tested that assimilate formaldehyde by the serine or ribulose monophosphate pathway. H(4)MPT-dependent activities were also found in autotrophic Xanthobacter strains. However, no H(4)MPT-dependent enzyme activities could be detected in other autotrophic alpha-proteobacteria or in gram-positive methylotrophic bacteria. Genes encoding methenyl H(4)MPT cyclohydrolase (mch genes) were cloned and sequenced from several proteobacteria. Bacterial and archaeal Mch sequences have roughly 35% amino acid identity and form distinct groups in phylogenetic analysis. 相似文献
8.
Heterospecific lox sites are mutated lox sites that in the presence of Cre recombinase recombine with themselves but not or much less with wildtype loxP. We here show that in Escherichia coli both lox511 and lox2272 sites become highly promiscuous with respect to loxP when in the presence of Cre one of the recombination partners is present in a larger stretch of an inverted repeat of non-lox DNA. In such a palindromic DNA configuration, also the occurrence of other DNA repeat-mediated recombination events is somewhat increased in the presence of Cre. The results indicate that in recombinase mediated cassette exchange or other double lox applications based on the exclusivity of heterospecific lox sites, or in research combining Cre-lox approaches with hairpin RNA for gene silencing, the presence of duplicated DNA around lox sites has to be taken into account. It is proposed that the presence of palindromic non-lox DNA interferes with the homology search of the Cre enzyme prior to the actual recombination event. 相似文献
9.
Stop codon recognition in ciliates: Euplotes release factor does not respond to reassigned UGA codon 总被引:5,自引:0,他引:5
In eukaryotes, the polypeptide release factor 1 (eRF1) is involved in translation termination at all three stop codons. However, the mechanism for decoding stop codons remains unknown. A direct interaction of eRF1 with the stop codons has been postulated. Recent studies focus on eRF1 from ciliates in which some stop codons are reassigned to sense codons. Using an in vitro assay based on mammalian ribosomes, we show that eRF1 from the ciliate Euplotes aediculatus responds to UAA and UAG as stop codons and lacks the capacity to decipher the UGA codon, which encodes cysteine in this organism. This result strongly suggests that in ciliates with variant genetic codes eRF1 does not recognize the reassigned codons. Recent hypotheses describing stop codon discrimination by eRF1 are not fully consistent with the set of eRF1 sequences available so far and require direct experimental testing. 相似文献
10.
Ludmila Sošková 《Folia microbiologica》1960,5(6):406-413
Путем пассажей лизогенного штамма Escherichia coli K 12 на средах, содержавших повышающиеся кондентрадии дианистого калия, удалось вырастить варианты, резистентные к 0,4 мол. Кондент KCN. Полученные резистентые штаммы сохраняют свою резистентность и при пассажах на средах без дианистого калия. С приобретением устойчивости к дианистому калиию у этих штаммов изменились и другие свойства в сравнении с исходным штаммом. Некоторые изменения оказались обратимыми, другие, — как биохимические изменения, изменения чувствительности к ?агам и в продукции ?ага, — сохранялись стабильно и после 50 пассажей на средах без цианистого калия. С помощью ?ага, выделенного из штамма К 12, устойчивого к 0,4 мол. концентрации цианистого калия, удалась трансдукция не только устойчивости к цианистому калию, но одновременно и чувствительности к ?агам группы coli Т и утраты способности сбраживать дульцит. Однако связь между этими особенностями не была стопроцентной, так как перенесенная устойчивость к дианистому калию оказалась несколько более низкой, чем исходная (0,3 мол. Вместо 0,4 мол.), а бактерии после трансдукдии продуцировали не только ?аг α, как бактериидоноры, но и преимущественно первоначальный ?аг. 相似文献