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31.
Dr. Gerard J. McGarrity Lindsay Gamon Theodor Steiner Joseph Tully Hitoshi Kotani 《Current microbiology》1985,12(2):107-112
Uridine phosphorylase activity has been used to detect mycoplasmas in cell cultures by measuring formation of14C-uracil from14C-uridine. In this report we show that all species ofMycoplasma, Acholeplasma, andUreaplasma tested exhibited uridine phorphorylase activity. Among the genusSpiroplasma, serogroups I-1, I-3, I-5, I-7, I-8, IV, XIII, and XIV lacked uridine phosphorylase activity.Present address: Ciba-Geigy, Basel, Switzerland. 相似文献
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Summary We have cloned the hisH tyrA wild-type genes of Bacillus subtilis with the aid of the chimeric plasmid pBJ194, which replicates both in B. subtilis and Escherichia coli. Primary cloning was done in E. coli. The original E. coli clone, carrying the recombinant plasmid (pGR1) which complements hisH tyrA mutants of B. subtilis, was selected directly from a mixture of plated E. coli clones by replicaplating these clones onto minimal agar plates without tyrosine spread just before with competent B. subtilis cells. After overnight incubation clusters of small colonies had developed exclusively in the E. coli [pGR1] colony prints.The Tyr+ minicolonies were shown to be B. subtilis carrying pGR1 because (i) their appearance depended linearly on the number of B. subtilis cells plated, (ii) they produced extracellular protease and amylase and (iii) plasmids could be reisolated from the minicolonies and used to transform B. subtilis recE4 tyrA1 both to Cmr and Tyr+.Plasmid pGR1 transfer through replica plating was compared with plasmid transfer in liquid. Both systems depended on transformable B. subtilis strains and were sensitive to DNAseI. However, whereas integration of the tyrA
+ gene into the chromosome and concomittant loss of plasmids occurred frequently during regular plasmid transformation of Rec+
B. subtilis, this was a rare event during plasmid transfer through replica plating. 相似文献
34.
Repair of UV damage in plasmid DNA by human fibroblasts 总被引:1,自引:0,他引:1
Hans Mooibroek Bauke de Jong Gerard Venema 《Molecular & general genetics : MGG》1984,195(1-2):175-179
Summary Plasmid DNA from Bacillus subtilis was introduced into monolayers of human fibroblasts by means of a modification of the calcium phosphate coprecipitation technique, comprising centrifugation of the coprecipitate onto the cells and treatment with polyethyleneglycol. The amount of DNA resistant to removal from the monolayers ranged from 10% to 15% of the input DNA. By determination of the biological activity of the plasmid DNA, re-extracted after various periods following entry into the fibroblasts and subsequently used as donor for B. subtilis protoplasts, it was shown that the activity of the plasmid DNA was gradually lost. When ultraviolet light-inactivated plasmid DNA was used as donor, reactivation of the plasmid was observed, which was completed within 2 h. The dose-dependent incorporation of [14C]-thymidine suggests that DNA repair processes were involved in reactivation of the plasmid DNA. 相似文献
35.
Dr. Paul A. Lespinat Yves M. Berlier Guy D. Fauque Rene Toci Gerard Denariaz Jean LeGall 《Journal of industrial microbiology & biotechnology》1987,1(6):383-388
Summary Hydrogenase and nitrogenase activities of sulfate-reducing bacteria allow their adaptation to different nutritional habits even under adverse conditions. These exceptional capabilities of adaptation are important factors in the understanding of their predominant role in problems related to anaerobic metal corrosion. Although the D2–H+ exchange reaction indicated thatDesulfovibrio desulfuricans strain Berre-Sol andDesulfovibrio gigas hydrogenases were reversible, the predominant activity in vivo was hydrogen uptake. Hydrogen production was restricted to some particular conditions such as sulfate or nitrogen starvation. Under diazotrophic conditions, a transient hydrogen evolution was followed by uptake when dinitrogen was effectively fixed. In contrast, hydrogen evolution proceeded when acetylene was substituted as the nitrogenase substrate. Hydrogen can thus serve as an electron donor in sulfate reduction and nitrogen metabolism. 相似文献
36.
Ecological factors determining establishment of cellulolytic bacteria and protozoa in the rumens of meroxenic lambs 总被引:2,自引:0,他引:2
Ecological factors that control the establishment of cellulolytic bacteria and ciliate protozoa in the lamb rumen were studied in meroxenic animals. Axenic lambs received dilutions of rumen liquor from either conventional lambs and sheep (pool A) or meroxenic lambs (pool B). The total number of bacteria established in the rumen was between 10(9) and 5 x 10(10) g-1. In lambs inoculated with dilutions (10(-6), 10(-7), 10(-8)) of pool A, cellulolytic bacteria did not become established. However, subsequent inoculation with Bacteroides succinogenes, resulted in colonization in lambs that had received 10(-6) and 10(-7) dilutions of pool A. However, B. succinogenes became established in only one of three lambs that received the 10(-8) dilution. Similar results were obtained for the protozoan Entodinium sp. With pool B, lambs were inoculated earlier and cellulolytic bacteria were established directly from the 10(-6) and 10(-7) inocula. Polyplastron multivesiculatum establishment occurred readily when inoculated into the lambs which had received the 10(-6) dilution of pool B. Results obtained in this study suggest that establishment of cellulolytic bacteria and protozoa requires an abundant and complex flora and is favoured by early animal inoculation. 相似文献
37.
Richard F. Selden Andre Steinmetz Lee McIntosh Lawrence Bogorad Gerard Burkard Mfika Mubumbila Marcel Kuntz Edwin J. Crouse Jacques H. Weil 《Plant molecular biology》1983,2(3):141-153
A minimum of 37 genes corresponding to tRNAs for 17 different amino acids have been localized on the restriction endonuclease cleavage site map of theZea mays chloroplast DNA molecule. Of these, 14 genes corresponding to tRNAs for 11 amino acids are located in the larger of the two single-copy regions which separate the two inverted copies of the repeat region. One tRNA gene is in the smaller single-copy region. Each copy of the large repeated sequence contains, in addition to the ribosomal RNA genes, 11 tRNA genes corresponding to tRNAs for 8 amino acids. The genes for tRNA2 Ile and tRNAAla map in the ribosomal spacer sequence separating the 16S and 23S ribosomal RNA genes. The three isoaccepting species for the tRNAsLeu and the three for tRNAsSer, as well as the two isoaccepting species for tRNAAsn, tRNAGly, tRNAsIle, tRNAsMet, tRNAsThr, are shown to be encoded at different loci. Two independent methods have been used for the localization of tRNA genes on the physical map of the maize chloroplast DNA molecule: (a) cloned chloroplast DNA fragments were hybridized with radioactively-labelled total 4S RNAs, the hybridized RNAs were then eluted, and identified by two-dimensional polyacrylamide gel electrophoresis, and (b) individual tRNAs were32P-labelledin vitro and hybridized to DNA fragments generated by digestion of maize chloroplast DNA with various restriction endonucleases. 相似文献
38.
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ELECTRON MICROSCOPIC OBSERVATIONS OF RAT AND MOUSE CEREBELLUM IN TISSUE CULTURE 总被引:12,自引:8,他引:4 下载免费PDF全文
Closely ordered stages of myelin formation in cultures of newborn rat and mouse cerebellum, selected by direct light microscopy, were studied with the electron microscope. Electron micrographs of these cultures reveal the presence of neurons, axons, neuroglia, microglia, and ependymal cells. The appearance of the neuron is identical to that previously described in vivo. The neuroglial cell has long, branching processes, and its cytoplasm is characterized by packets of long, narrow fibrils. During myelin formation, a glial cell process surrounds the axon. This process may form an internal mesaxon and may spiral for several turns around the axon. Other glial cell processes may interdigitate with or overlay the innermost process to contribute to the multilamellated structure. The glial processes flatten and the cytoplasmic surfaces of the cell membrane come into contact to form the lamellae of the myelin sheath. These adhesions may be temporarily incomplete as evidenced by sequestered islands of glial cytoplasm among the myelin lamellae. Ultimately, a compact, apparently spiral, myelin sheath is formed. These findings are discussed in relation to in vivo central myelin formation. 相似文献