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1.
2.
We have characterized the biosynthesis of two metalloproteinases, procollagenase and prostromelysin, by rabbit brain capillary endothelial cells (RBCE) by means of immunochemical, biosynthetic, and functional assays. Unstimulated RBCE secreted no detectable metalloproteinases. Secretion of both procollagenase and prostromelysin was induced within 6 h by treating the cells with 50 ng/ml 12-O-tetradecanoylphorbol-13-acetate. In treated cells, the two proenzymes accounted for up to 20% of the [35S]methionine-labeled secreted proteins; about 15 micrograms of each protein was secreted in 48 h by 10(6) RBCE. Although RBCE secreted approximately as much procollagenase and prostromelysin as did rabbit fibroblasts, virtually no enzyme activity could be measured in RBCE-conditioned medium, even after activation of the proenzymes by trypsin or an organomercurial agent. 相似文献
3.
The effect of high static pressures on the internal structure of the immunoglobulin light chain (Bence-Jones) dimer from the patient Mcg was assessed with measurements of intrinsic protein fluorescence polarization and intensity. Depolarization of intrinsic fluorescence was observed at relatively low pressures (less than 2 kbar), with a standard volume change of -93 mL/mol. The significant conformational changes indicated by these observations were not attributable to major protein unfolding, since pressures exceeding 2 kbar were required to alter intrinsic fluorescence emission maxima and yields. Fluorescence intensity and polarization measurements were used to investigate pressure effects on the binding of bis(8-anilino-naphthalene-1-sulfonate) (bis-ANS), rhodamine 123, and bis(N-methylacridinium nitrate) (lucigenin). Below 1.5 kbar the Mcg dimer exhibited a small decrease in affinity for bis-ANS (standard volume change approximately 5.9 mL/mol). At 3 kbar the binding activity increased by greater than 250-fold (volume change -144 mL/mol) and remained 10-fold higher than its starting value after decompression. With rhodamine 123 the binding activity showed an initial linear increase but plateaued at pressures greater than 1.5 kbar (standard volume change -23 mL/mol). These pressure effects were completely reversible. Binding activity with lucigenin increased slightly at low pressures (standard volume change -5.5 mL/mol), but the protein was partially denatured at pressures greater than 2 kbar. Taken in concert with the results of parallel binding studies in crystals of the Mcg dimer, these observations support the concept of a large malleable binding region with broad specificity for aromatic compounds.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
4.
T cell tolerance to self antigens in New Zealand hybrid mice with lupus-like disease 总被引:1,自引:0,他引:1
B L Kotzin J W Kappler P C Marrack L R Herron 《Journal of immunology (Baltimore, Md. : 1950)》1989,143(1):89-94
We determined if self-reactive T cells are able to escape thymic tolerance in autoimmune New Zealand mice. T cells utilizing V beta 17a and V beta 11 encoded receptors have been shown to be clonally eliminated in nonautoimmune mice expressing I-E because of their potential self-reactivity. Similarly, V beta 8.1+ and V beta 6+ T cells are tolerized in the thymus of nonautoimmune mice that express Mls-1a. These T cell subsets were quantitated in the lymph nodes and spleens of (NZB x NZW)F1 and (NZB x SWR)F1 mice. In young mice from both autoimmune strains, deletion was similar to that observed in control animals matched for I-Ed and Mls-1a expression. Furthermore, older female autoimmune mice with elevated levels of IgG antinuclear antibodies and severe lupus-like renal disease did not demonstrate evidence of a global tolerance defect. We also found that the levels of residual V beta 17a+ cells in MHC-matched control F1 strains were further reduced by up to 80% in autoimmune (NZB x SWR)F1 mice. The greater in vivo elimination corresponded to an enhanced ability of NZB spleen cells, compared with other H-2d spleen cells, to stimulate V beta 17a+ hybridomas in vitro. The increased stimulation in culture could not be attributed to quantitative differences in I-E Ag expression. The results suggest that autoreactive T cells have been eliminated in these autoimmune mice by normal mechanisms of self-tolerance. Furthermore, the data demonstrate the existence of an NZB minor locus not present in other H-2d strains that influences T cell repertoire and enhances stimulation of T cells potentially reactive to self class II MHC Ag. 相似文献
5.
Clofentezine resistance in T. urticae was first confirmed in Australia in 1987 after Queensland glasshouse roses had been exposed to 40 applications of clofentezine over a 10 month period. Clofentezine resistance in this strain was extremely high (>2.500x) and conferred high level cross-resistance to the chemically unrelated compound hexythiazox. Clofentezine resistance in T. urticae was detected in pome fruit orchards in the Goulburn Valley, Victoria in 1988 and caused field control failure after 5–6 sprays. Resistance was subsequently detected in Adelaide during 1988 and the Bathurst Orange region, NSW in 1989. Clofentezine and hexythiazox resistance appears particularly stable making it difficult to manage.This work contributes in part for the fulfilment of the requirements of the degree of PhD. at the University of Sydney. 相似文献
6.
A rapid, sensitive method for the quantitative measurement of certain major and modified purines in DNA of carcinogen-treated animals is presented. DNA hydrolysates are analyzed by high-pressure liquid chromatography combined with fluorescence detection and electronic integration of peaks. Limits of detection are approximately 7 ng for 7-methylguanine and 150 pg for O6-methylguanine. Between 100 and 250 μg target organ DNA from animals treated with several carcinogens was shown to contain readily detectable amounts of these methylated bases. The method provides results comparable to those obtained with conventional methods using radioactively labeled carcinogens. 相似文献
7.
Poly-beta-hydroxybutyrate (PHB) is a uniquely procaryotic endogenous storage polymer whose metabolism has been shown to reflect environmental perturbations in laboratory monocultures. When hydrolyzed for 45 min in 5% sodium hypochlorite, PHB can be isolated from estuarine detrital microflora in high yield and purified free from non-PHB microbial components. Lyophilization of frozen estuarine samples shortens the exposure time to NaOCl necessary for maximal recovery. Lyophilized samples of hardwood leaves, Vallisneria, and the aerobic upper millimeter of estuarine muds yielded PHB. The efficiency of incorporation of sodium [1-C]acetate into PHB is very high and is stimulated by aeration. PHB was not recovered from the anaerobic portions of sediments unless they were aerated for a short time. Levels of PHB in the detrital microbial community do not correlate with the microbial biomass as measured by the extractible lipid phosphate, suggesting that PHB-like eucaryotic endogenous storage materials may more accurately reflect the metabolic status of the population than its biomass. 相似文献
8.
W Jiskoot M Bloemendal B van Haeringen R van Grondelle E C Beuvery J N Herron D J Crommelin 《European journal of biochemistry》1991,201(1):223-232
The pH dependence of the conformation of a mouse IgG2a, kappa monoclonal antibody (MN12) was investigated by several physical techniques, including fluorescence spectroscopy, near-ultraviolet and far-ultraviolet CD, and electric-field-induced transient birefringence measurements. The intensity of the intrinsic tryptophan fluorescence remained constant in the pH range from 3.5 to 10.0. A conformational alteration in the MN12 molecule was observed in the pH region between pH 3.5 and 2.5, as reflected by a substantial enhancement of the fluorescence quantum yield. This effect was more pronounced at high ionic strengths. The fluorescence emission was unaltered, indicating that the acid-induced conformational state is different from a completely unfolded state. This was confirmed by CD and fluorescence polarisation measurements. Iodide and acrylamide fluorescence quenching studies indicated a gradually increasing accessibility of MN12 tryptophan residues with decreasing pH. At low pH precipitation was observed in the presence of iodide. One rotational relaxation time (0.16-0.18 microseconds) was observed for MN12 by electric-field-induced transient birefringence measurements at low ionic strength. After exposure of MN12 to low pH for 1 h, the relaxation time was increased to 0.23 microseconds; a further increase to 0.30 microseconds was observed after 24 h. The combined results suggest an acid-induced expansion and enhanced flexibility of MN12, which eventually leads to irreversible aggregation. 相似文献
9.
10.
Tang Z Xiao C Zhuang Y Chu J Zhang S Herron PR Hunter IS Guo M 《Enzyme and microbial technology》2011,49(1):17-24
The aromatic polyketide antibiotic, oxytetracycline (OTC), is produced by Streptomyces rimosus as an important secondary metabolite. High level production of antibiotics in Streptomycetes requires precursors and cofactors which are derived from primary metabolism; therefore it is exigent to engineer the primary metabolism. This has been demonstrated by targeting a key enzyme in the oxidative pentose phosphate pathway (PPP) and nicotinamide adenine dinucleotide phosphate (NADPH) generation, glucose-6-phosphate dehydrogenase (G6PDH), which is encoded by zwf1 and zwf2. Disruption of zwf1 or zwf2 resulted in a higher production of OTC. The disrupted strain had an increased carbon flux through glycolysis and a decreased carbon flux through PPP, as measured by the enzyme activities of G6PDH and phosphoglucose isomerase (PGI), and by the levels of ATP, which establishes G6PDH as a key player in determining carbon flux distribution. The increased production of OTC appeared to be largely due to the generation of more malonyl-CoA, one of the OTC precursors, as observed in the disrupted mutants. We have studied the effect of zwf modification on metabolite levels, gene expression, and secondary metabolite production to gain greater insight into flux distribution and the link between the fluxes in the primary and secondary metabolisms. 相似文献