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Breakdown of crystalline cellulose by synergistic action between cellulase components from Clostridium thermocellum and Trichoderma koningii 总被引:1,自引:0,他引:1
Abstract Certain isolated components of fungal cellulases, which cannot effect the breakdown of highly ordered cellulose individually, interact together synergistically to do so when recombined. Suprisingly, not all fungal cellulase components exhibit this property, and no such synergism has been observed so far between fungal and bacterial cellulases.
The cellulase complex of Clostridium thermocellum cannot effect the extensive breakdown of highly ordered cellulose unless Ca2+ and dithiothreitol (DTT) are present. However, we now report that isolated cellobiohydrolase from Trichoderma koningii can combine with C. thermocellum cellulase to effect the breakdown of cellulose in the absence of Ca2+ and DTT. enhanced activity is observed if Ca2+ and DTT are present.
This finding may have important applications in industry: it certainly has important implications for those interested in the basic mechanism of cellulase action in C. thermocellum . 相似文献
The cellulase complex of Clostridium thermocellum cannot effect the extensive breakdown of highly ordered cellulose unless Ca
This finding may have important applications in industry: it certainly has important implications for those interested in the basic mechanism of cellulase action in C. thermocellum . 相似文献
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A single injection of ergocryptine (0.5 mg/kg liveweight) given to ewes 0.5-20 days prepartum or two injections (0.5 mg/kg liveweight per injection) given c. 30 and 10 days prepartum reduced concentrations of plasma prolactin to negligible (less than 5 ng/ml) values for 4 weeks after parturition, but did not affect concentrations of growth hormone and placental lactogen. Milking of treated ewes had no effect on concentrations of plasma prolactin during the first 4 weeks of lactation, but concentrations of growth hormone were increased during the 10-20 min period after milking. The half-life of prolactin in plasma was estimated as 21 min. In spite of the dramatic effect of ergocryptine on plasma prolactin all treated ewes secreted copious quantities of milk of normal composition. Mean daily yields of ewes treated with ergocryptine were not significantly different (P greater than 0.05) from those of untreated control ewes, but the mean +/- s.e.m. of total milk production over the first 3 weeks of lactation for ergocryptine-treated ewes was significantly lower (P less than 0.05) than that of control ewes (9.5 +/- 1.11 v. 14.1 +/- 1.20 kg milk). The results suggest that prolactin is not an essential component of the lactogenic and galactopoietic complexes of hormones in the ewe. 相似文献
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Variation in heat shock proteins within tropical and desert species of poeciliid fishes 总被引:8,自引:0,他引:8
Norris CE; diIorio PJ; Schultz RJ; Hightower LE 《Molecular biology and evolution》1995,12(6):1048-1062
The 70-kilodalton heat shock protein (hsp70) family of molecular
chaperones, which contains both stress-inducible and normally abundant
constitutive members, is highly conserved across distantly related taxa.
Analysis of this protein family in individuals from an outbred population
of tropical topminnows, Poeciliopsis gracilis, showed that while
constitutive hsp70 family members showed no variation in protein isoforms,
inducibly synthesized hsp70 was polymorphic. Several species of
Poeciliopsis adapted to desert environments exhibited lower levels of
inducible hsp70 polymorphism than the tropical species, but constitutive
forms were identical to those in P. gracilis, as they were in the
confamilial species Gambusia affinis. These differences suggest that
inducible and constitutive members of this family are under different
evolutionary constraints and may indicate differences in their function
within the cell. Also, northern desert species of Poeciliopsis synthesize a
subset of the inducible hsp70 isoforms seen in tropical species. This
distribution supports the theory that ancestral tropical fish migrated
northward and colonized desert streams; the subsequent decrease in
variation of inducible hsp70 may have been due to genetic drift or a
consequence of adaptation to the desert environment. Higher levels of
variability were found when the 30- kilodalton heat shock protein (hsp30)
family was analyzed within different strains of two desert species of
Poeciliopsis and also in wild-caught individuals of Gambusia affinis. In
both cases the distribution of hsp30 isoform diversity was similar to that
seen previously with allozyme polymorphisms.
相似文献
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The inhibitory effects of nikkomycin, polyoxin B, and UDP were tested on particulate chitin synthetase activity (UDP-2-acetamido-2-deoxy-D-glucose: chitin-4-B-acetamidodeoxy-D-glucosyltransferase, E.C.2.4.1.16) fromNeurospora crassa. Two approaches were used: (a) inhibitors were tested for their individual effects on chitin synthetase activity; (b) paired combinations of inhibitors were examined to establish whether the compounds affected inhibition by binding at the same enzyme site. The first method showed that the three compounds are linear competitive inhibitors, i.e. each competes directly with the substrate for binding. Ki app values were: UDP, 0.8 mM; polyoxin B, 32 M; and nikkomycin, 2 M. The second method showed that the inhibitors compete with each other for binding; thus they bind at the same site. The pyrimidine nucleoside moiety of these inhibitors is an essential component for effective inhibition, but the potency of inhibition is critically dependent on the conformation of the side group attached to carbon 5 of the ribose sugar. 相似文献
8.
Comparison of EC broth and medium A-1 for the recovery of Escherichia coli from frozen shucked snow crab. 总被引:1,自引:0,他引:1
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Two variations of the multiple-tube fermentation technique were used to enumerate fecal coliforms in commercially processed, frozen crab meat. These were the EC confirmation test and a more rapid method that requires medium A-1. The method with medium A-1 was more specific than the EC confirmation test for detecting Escherichia coli type 1. E. coli was isolated from 84% of the positive medium A-1 tubes, whereas it was isolated from only 64% of the positive tubes of EC broth. When samples of crab meat were inoculated with known amounts of E. coli, better estimates of the known numbers were obtained by the medium A-1 method. Several species of nonfecal coliforms were isolated from cultures in EC broth. These belonged to the genera Klebsiella, Citrobacter, Enterobacter, and Serratia. Apparently these strains were naturally adapted to growth at an elevated temperature because the majority were able to grow at 44.5 degrees C when retested in EC broth. Fewer species of nonfecal coliforms were isolated from medium A-1. Those that were isolated belonged to the genera Citrobacter and Enterobacter. 相似文献
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Summary In a collection of Nigerian serum samples typed for alleles of factor B of the alternative complement pathway, a very high frequency of BfF was found (0.69). In addition, a new variant was found in two samples. This variant (F1.29) moved faster than BfF1. It was hemolytically active.Supported in part by The Medical Research Council of Canada 相似文献
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Ovariectomized ewes were treated with progesterone and oestradiol to induce oestrus (day of expected oestrus = day 0) and with progesterone on days 1 to 12. The concentrations of endometrial oxytocin receptors and the 13,14-dihydro-15-keto prostaglandin F2 alpha (PGFM) response induced by oxytocin were measured on days 12, 14, 16 and 18 after the cessation of progesterone treatment on day 12, by a receptor binding assay and direct radioimmunoassay, respectively. During the period of treatment, the concentrations of plasma progesterone were high and remained above 2 ng ml-1 until day 13 when they dropped rapidly to less than 0.5 ng ml-1 by day 14. The concentrations of oxytocin receptors in endometrium of control ewes were high (820.7 +/- 91.7 (SEM) fmol mg-1 protein). Treatment with progesterone significantly (P < 0.01) reduced the concentrations of the receptors on days 12 and 14 (144.1 +/- 65.0 and 200.4 +/- 45.4 fmol mg-1 protein, respectively). The receptor concentrations then increased to relatively high values on day 16 (1021.4 +/- 216.6 fmol mg-1 protein) and remained high until day 18 (677.7 +/- 103.4 fmol mg-1 protein).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献