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排序方式: 共有170条查询结果,搜索用时 15 毫秒
1.
Juliana S Bernardes Alberto MR Dávila Vítor S Costa Gerson Zaverucha 《BMC bioinformatics》2007,8(1):435
Background
Remote homology detection is a challenging problem in Bioinformatics. Arguably, profile Hidden Markov Models (pHMMs) are one of the most successful approaches in addressing this important problem. pHMM packages present a relatively small computational cost, and perform particularly well at recognizing remote homologies. This raises the question of whether structural alignments could impact the performance of pHMMs trained from proteins in the Twilight Zone, as structural alignments are often more accurate than sequence alignments at identifying motifs and functional residues. Next, we assess the impact of using structural alignments in pHMM performance. 相似文献2.
3.
Marcio Voloch Michael R. Ladisch Victor W. Rodwell George T. Tsao 《Biotechnology and bioengineering》1981,23(6):1289-1296
Fermentation of xylose by Klebsiella pneumoniae (ATCC 8724) producers meso and nonmeso 2,3-butaneodiol. The enzyme Kinetic of 2,3-butanediol stereoisomer formation from acetone is currently under study in our laboratory. Modeling of these kinetics requires resolution of meso and racemic 2,3-butanediol and positive identification of these resolved components. We report their resolution by aqueous liquid chromatography on both an analytical and a preparative scale. The resolved stereoisomer were identified by a combination of gas chromatography, gas chromatography/mass spectroscopy, 13C-NMR spectroscopy, optical activity, and, melting points of the m-dinitrobenzoyl eaters of meso and racemic 2,3-butanediol. An aqueous liquid chromatographic technique for resolving and qualifying major components of a butanediol fermentation mixture in 40 min is presented. 相似文献
4.
Recombinant human insulin. 总被引:1,自引:0,他引:1
Insulin is a well-characterized peptide that can be produced by recombinant DNA technology for human therapeutic use. A brief overview of insulin production from both traditional mammalian pancreatic extraction and recombinant bacterial and yeast systems is presented, and detection techniques, including electrophoresis, are reviewed. Analytical systems for insulin separation are principally based on reversed-phase chromatography, which resolves the deamidation product(s) (desamido insulin) of insulin, proinsulin, and insulin. Process-scale separation is a multistep process and includes ion exchange, reversed-phase, and size exclusion chromatography. Advantages and/or disadvantages of various separation approaches, as described by the numerous literature references on insulin purification, are presented. 相似文献
5.
Emilie M. M. Santos Wiro J. Niessen Albert J. Yoo Olvert A. Berkhemer Ludo F. Beenen Charles B. Majoie Henk. A. Marquering MR CLEAN investigators 《PloS one》2016,11(1)
Background and Purpose
In acute ischemic stroke (AIS) management, CT-based thrombus density has been associated with treatment success. However, currently used thrombus measurements are prone to inter-observer variability and oversimplify the heterogeneous thrombus composition. Our aim was first to introduce an automated method to assess the entire thrombus density and then to compare the measured entire thrombus density with respect to current standard manual measurements.Materials and Method
In 135 AIS patients, the density distribution of the entire thrombus was determined. Density distributions were described using medians, interquartile ranges (IQR), kurtosis, and skewedness. Differences between the median of entire thrombus measurements and commonly applied manual measurements using 3 regions of interest were determined using linear regression.Results
Density distributions varied considerably with medians ranging from 20.0 to 62.8 HU and IQRs ranging from 9.3 to 55.8 HU. The average median of the thrombus density distributions (43.5 ± 10.2 HU) was lower than the manual assessment (49.6 ± 8.0 HU) (p<0.05). The difference between manual measurements and median density of entire thrombus decreased with increasing density (r = 0.64; p<0.05), revealing relatively higher manual measurements for low density thrombi such that manual density measurement tend overestimates the real thrombus density.Conclusions
Automatic measurements of the full thrombus expose a wide variety of thrombi density distribution, which is not grasped with currently used manual measurement. Furthermore, discrimination of low and high density thrombi is improved with the automated method. 相似文献6.
7.
Danilo ML Prado Fabiana B Benatti Ana L de Sá-Pinto Ana P Hayashi Bruno Gualano Rosa MR Pereira Adriana ME Sallum Eloisa Bonfá Clovis A Silva Hamilton Roschel 《Arthritis research & therapy》2013,15(2):R46
Introduction
Exercise training has emerged as a promising therapeutic strategy to counteract physical dysfunction in adult systemic lupus erythematosus. However, no longitudinal studies have evaluated the effects of an exercise training program in childhood-onset systemic lupus erythematosus (C-SLE) patients. The objective was to evaluate the safety and the efficacy of a supervised aerobic training program in improving the cardiorespiratory capacity in C-SLE patients.Methods
Nineteen physically inactive C-SLE patients were randomly assigned into two groups: trained (TR, n = 10, supervised moderate-intensity aerobic exercise program) and non-trained (NT, n = 9). Gender-, body mass index (BMI)- and age-matched healthy children were recruited as controls (C, n = 10) for baseline (PRE) measurements only. C-SLE patients were assessed at PRE and after 12 weeks of training (POST). Main measurements included exercise tolerance and cardiorespiratory measurements in response to a maximal exercise (that is, peak VO2, chronotropic reserve (CR), and the heart rate recovery (ΔHRR) (that is, the difference between HR at peak exercise and at both the first (ΔHRR1) and second (ΔHRR2) minutes of recovery after exercise).Results
The C-SLE NT patients did not present changes in any of the cardiorespiratory parameters at POST (P > 0.05). In contrast, the exercise training program was effective in promoting significant increases in time-to-exhaustion (P = 0.01; ES = 1.07), peak speed (P = 0.01; ES = 1.08), peak VO2 (P = 0.04; ES = 0.86), CR (P = 0.06; ES = 0.83), and in ΔHRR1 and ΔHRR2 (P = 0.003; ES = 1.29 and P = 0.0008; ES = 1.36, respectively) in the C-SLE TR when compared with the NT group. Moreover, cardiorespiratory parameters were comparable between C-SLE TR patients and C subjects after the exercise training intervention, as evidenced by the ANOVA analysis (P > 0.05, TR vs. C). SLEDAI-2K scores remained stable throughout the study.Conclusion
A 3-month aerobic exercise training was safe and capable of ameliorating the cardiorespiratory capacity and the autonomic function in C-SLE patients.Trial registration
NCT01515163. 相似文献8.
Xuan Li Eduardo Ximenes Mary Anne Roshni Amalaradjou Hunter B. Vibbert Kirk Foster Jim Jones Xingya Liu Arun K. Bhunia Michael R. Ladisch 《Applied and environmental microbiology》2013,79(22):7048-7054
This paper reports an approach to enable rapid concentration and recovery of bacterial cells from aqueous chicken homogenates as a preanalytical step of detection. This approach includes biochemical pretreatment and prefiltration of food samples and development of an automated cell concentration instrument based on cross-flow microfiltration. A polysulfone hollow-fiber membrane module having a nominal pore size of 0.2 μm constitutes the core of the cell concentration instrument. The aqueous chicken homogenate samples were circulated within the cross-flow system achieving 500- to 1,000-fold concentration of inoculated Salmonella enterica serovar Enteritidis and naturally occurring microbiota with 70% recovery of viable cells as determined by plate counting and quantitative PCR (qPCR) within 35 to 45 min. These steps enabled 10 CFU/ml microorganisms in chicken homogenates or 102 CFU/g chicken to be quantified. Cleaning and sterilizing the instrument and membrane module by stepwise hydraulic and chemical cleaning (sodium hydroxide and ethanol) enabled reuse of the membrane 15 times before replacement. This approach begins to address the critical need for the food industry for detecting food pathogens within 6 h or less. 相似文献
9.
Soybeans (Glycine max) contain an alpha-galactosidase that makes up a small fraction of the total protein of the seed. The properties of this enzyme are of interest because of its potential to convert the galactooligosaccharides, stachyose and raffinose, in soybean meal to sugars digestible in the human gastro intestinal tract and thereby increase potential uses of this vegetable protein source in human and animal foods. Study of this enzyme required the isolation of milligram quantities of electrophoretically pure protein from ground soybeans and therefore, scaleup of laboratory procedures by a factor of 300 times. Large scale acid precipitation, ammonium sulfate precipitation, and centrifugal recovery of the precipitated protein allowed alpha-galactosidase to be isolated from 45.5 kg soybean meal containing 17.1 kg protein, to obtain an enzyme extract with a specific activity of 90 to 100. A novel combination of strong anion exchange and cation exchange chromatography followed by Concanavalin-A affinity chromatography with a methyl alpha-D mannoside gradient gave alpha-galactosidase with an average specific activity of 56,000. Ion exchange chromatography preceding Concanavalin-A affinity chromatography allowed elimination of a relatively costly melibiose affinity chromatography step (which followed the Concanavalin-A column In the laboratory procedure) thereby making scaleup practical. 相似文献
10.
alpha-Galactosidase from soybean (Glycine max) was purified by a five-step procedure. The enzyme's natural substrates, raffinose and stachyose, have K(m)'s of 3. 0 mM and 4. 79 mM, respectively. The products, galactose and sucrose, were measured after separation by liquid chromatography. Galactose is a competitive product inhibitor of stachyose and raffinose hydrolysis with a K(i) of 0. 12 mM. We determined these parameters by an integral kinetic approach. Stachyose hydrolysis gives a nearly constant level of raffinose shortly after hydrolysis begins. Thus, cleavage of the first alpha-(1,6)-bond in the tetrasaccharide is the rate-limiting step. Since the stachyose hydrolysis yields raffinose, soybean alpha-galactosidase simultaneously hydrolyzes two substrates. We present a novel approach for analyzing simultaneous substrate hydrolysis with competitive product inhibition by a modified integral rate expression. The experimentally found kinetic parameters are confirmed by solving the simultaneous equations which describe the hydrolysis. This technique may be applicable to other hydrolytic enzymes with multiple substrates. 相似文献