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401.
402.
The growth of anthracycline producer Streptomices peucetius subsp. caesius ATCC 27952-2 was inhibited by presence of glucose on complete media, containing alternative carbon sources. Amount of clones not producing antibiotic increased to 80.2 per cent along with elevation of glucose concentration in corn meal medium from 0.1 to 1.0 per cent. Mutants of S. peucetius subsp. caesius ATCC 27952-2 able to grow on complete media with 2 per cent of glucose (glr-mutants) were obtained. Glr-mutants had decreased antibiotic production in comparison with 27952-2 strain. 17 per cent of studied glr-mutants synthesized 1.6-3.1-fold quantities of anthracyclines in comparison with parental strain. Glr-mutants synthesized more biomass, although more slowly utilized glucose than strain 27952-2. 相似文献
403.
404.
The evoked dynamics of the omega potential and its relation to some parameters of mental working capacity in operators working at steam power plants were studied under production conditions. The dependence of the omegagram type on the background level of the omega potential was determined. 12 types of omegagrams constituting two A and B clusters with negative correlation were distinguished. The highest level of mental working capacity was observed in operators with the background values of the omega potential not exceeding 45 mV and with the omegagram type belonging to the B cluster. 相似文献
405.
406.
Since the end of the 1950s hydrogencarbonate (‘bicarbonate’) is discussed as a possible cofactor of photosynthetic water-splitting, and in a recent X-ray crystallography model of photosystem II (PSII) it was displayed as a ligand of the Mn4OxCa cluster. Employing membrane-inlet mass spectrometry (MIMS) and isotope labelling we confirm the release of less than one (≈ 0.3) HCO3− per PSII upon addition of formate. The same amount of HCO3− release is observed upon formate addition to Mn-depleted PSII samples. This suggests that formate does not replace HCO3− from the donor side, but only from the non-heme iron at the acceptor side of PSII. The absence of a firmly bound HCO3− is corroborated by showing that a reductive destruction of the Mn4OxCa cluster inside the MIMS cell by NH2OH addition does not lead to any CO2/HCO3− release. We note that even after an essentially complete HCO3−/CO2 removal from the sample medium by extensive degassing in the MIMS cell the PSII samples retain ≥ 75% of their initial flash-induced O2-evolving capacity. We therefore conclude that HCO3− has only ‘indirect’ effects on water-splitting in PSII, possibly by being part of a proton relay network and/or by participating in assembly and stabilization of the water-oxidizing complex. 相似文献
407.
The photomechanical effect was found in a polymer composition on the basis of polymethylmethacrylate with embedded molecules of the luminophor incapable to undergo photochemical isomerization (anthracenoylacetonate of boron difluoride and dibenzoylmethanatoeuropiate triethylammonium), unlike other compounds having the above effect. The possibility of the development of a simple upward–downward movement drive on the basis of the above compounds was demonstrated. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
408.
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I N Nastasiak V A Fedorenko N V Kirichenko V N Danilenko 《Antibiotiki i khimioterapii͡a》1990,35(12):11-13
Erythromycin-producing strains of S. erythraeus were characterized with respect to formation of spontaneous and induced rifampicin-resistant mutants. It was shown that the frequency of spontaneous rifampicin-resistant mutants formed by various strains amounted to 0.9.10(-8) = 9.1.10(-7). In some events the exposure to nitrosoguanidine increased the frequency of such mutants by 2 orders of magnitude. The rifampicin-resistant mutants differed in antibiotic resistance. It was found that a significant part of the rifampicin-resistant mutants became sensitive to heating (19.1 per cent) and lost the ability to form aeromycelium (21.8 per cent). 相似文献
410.
The feature of streptomycin resistance in S. erythraeus, a culture producing erythromycin, is genetically unstable. Mutants sensitive to 0.03 mg/ml of streptomycin are formed in the initial streptomycin resistant strains at a rate of 0.04 per cent. It was shown possible to perform step-by-step selection for increasing streptomycin resistance (from 0.2 to 15 mg/ml) in the mutants producing and not producing erythromycin. The increase in the streptomycin resistance did not lead to a higher resistance to other aminoglycosides. Restriction analysis of the total DNA with the use of various endonucleases demonstrated that the increase in the resistance was not associated with amplification of DNA nucleotide sequences. 相似文献