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141.
Glucose oxidase: natural occurrence, function, properties and industrial applications 总被引:1,自引:0,他引:1
Glucose oxidase (GOX) from Aspergillus niger is a well-characterised glycoprotein consisting of two identical 80-kDa subunits with two FAD co-enzymes bound. Both the
DNA sequence and protein structure at 1.9 Ǻ have been determined and reported previously. GOX catalyses the oxidation of d-glucose (C6H12O6) to d-gluconolactone (C6H10O6) and hydrogen peroxide. GOX is produced naturally in some fungi and insects where its catalytic product, hydrogen peroxide,
acts as an anti-bacterial and anti-fungal agent. GOX is Generally Regarded As Safe, and GOX from A. niger is the basis of many industrial applications. GOX-catalysed reaction removes oxygen and generates hydrogen peroxide, a trait
utilised in food preservation. GOX has also been used in baking, dry egg powder production, wine production, gluconic acid
production, etc. Its electrochemical activity makes it an important component in glucose sensors and potentially in fuel cell
applications. This paper will give a brief background on the natural occurrence, functions as well as the properties of glucose
oxidase. A good coverage on the diverse uses of glucose oxidase in the industry is presented with a brief outline on the working
principles in the various settings. Furthermore, food grade GOX preparations are relatively affordable and widely available;
the readers may be encouraged to explore other potential uses of GOX. One example is that GOX-catalysed reaction generates
significant amount of heat (∼200 kJ/mol), and this property has been mostly neglected in the various applications described
so far. 相似文献
142.
Tomas Svensson Erik Alerstam Margrét Einarsdóttír Katarina Svanberg Stefan Andersson‐Engels 《Journal of biophotonics》2008,1(3):200-203
The recent interest in photodynamic therapy of human prostate cancer is accompanied by a need for techniques for in vivo monitoring of optical and physiological characteristics. We propose time‐of‐flight (TOF) spectroscopy in combination with Monte Carlo evaluation as a reliable optical technique for quantitative assessment of absorption, scattering, hemoglobin content and tissue oxygenation in the human prostate. For the first time, we demonstrate Monte Carlo‐based evaluation of in vivo TOF photon migration data. We show that this approach is crucial in order to avoid the large errors associated with the use of time‐resolved diffusion theory of light propagation in prostate‐like tissues. This progress also allows us to present the first in vivo scattering spectroscopy of human prostate tissue. Furthermore, TOF spectroscopy, in contrast to the more common steady‐state approach, is insensitive to bleedings, and has been found highly reliable (100% success rate). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
143.
富士苹果多酚氧化酶特性研究 总被引:19,自引:0,他引:19
本文从富士苹果中提取和部分纯化多酚氧化酶,并对其特性进行研究。以邻苯二酚为作用底物,该酶最适pH为50,在pH50~80范围内有较高的稳定性。最适温度为30℃,在60℃以上迅速失活。该酶对不同的酚类物质表现出不同的底物专一性,由高至低的趋势依次为邻苯二酚、焦性没食子酸、DL-多巴、酪氨酸,其中对酪氨酸的活力为零。浓度为04mmol/L的VC、L-半胱氨酸及浓度为03mmol/L的亚硫酸氢钠,可完全抑制该酶活性。 相似文献
144.
Caci H Adan A Bohle P Natale V Pornpitakpan C Tilley A 《Chronobiology international》2005,22(3):523-540
Morningness scales have been translated into several languages, but a lack of normative data and methodological differences make cross-cultural comparisons difficult. This study examines the psychometric properties and factor structure of the Composite Scale of Morningness (CSM) in samples from five countries: France (n=627), Italy (n=702), Spain (n=391), Thailand (n=503), and Australia (n=654). Strong national differences are identified. A quadratic relationship between age and CSM total score was apparent in the Australian data with a downward trend after age 35 yrs. There was no age effect in any sample in the range from 18 to 29 yrs. Factor analysis identified a three-factor solution in all groups for both men and women. Tucker's congruence coefficients indicate that: (1) this solution is highly congruent between sexes in each culture, and (2) a morning affect factor is highly congruent between cultures. These results indicate there are national differences in factorial structure and that cut-off scores used to categorize participants as morning- and evening-types should be established for different cultural and age groups. 相似文献
145.
146.
Li Cui Jun Gong Xuerong Fan Ping Wang Qiang Wang Yaqin Qiu 《Engineering in Life Science》2013,13(2):149-155
Transglutaminase (TGase) catalyzes the cross‐linking of many proteins and has been widely used to improve the properties of certain protein‐based materials. Keratin is considered as a promising biomaterial candidate following traditional chemical modification. In this study, the effect of TGase on the properties of a wool keratin film was investigated. The TGase‐modified film was applied to drug release and cell proliferation. Treatment with TGase (30 U/g keratin) for 18 h at 40°C increased the tensile strength of the film from 5.18 ± 0.15 MPa to 6.22 ± 0.11 MPa and decreased the elongation at break from 83.47 ± 1.79% to 72.12 ± 3.02%. The stability of the film in PBS and in artificial gastric juice was also improved. A rougher surface and a more compact cross‐section were observed by scanning electron microscopy photographs of the TGase‐treated film. SDS‐PAGE analysis confirmed that higher molecular weight proteins were formed in the TGase‐modified keratin solution and film. The results of the drug release assay using diclofenac indicated that both films with and without TGase treatment led to a high initial release in PBS, which was more constant in artificial gastric juice. The enzyme treatment led to a lower drug release rate from the film. Cell culture experiments suggested that the TGase‐mediated cross‐linked keratin film shows a good biocompatibility and that it can be used for tissue engineering applications. 相似文献
147.
Sergey V. Baryshev Robert A. Erck Jerry F. Moore Alexander V. Zinovev C. Emil Tripa Igor V. Veryovkin 《Journal of visualized experiments : JoVE》2013,(72)
In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. From the measured surface, 3D topographic maps can be subsequently analyzed using a variety of software packages to extract the information that is needed.In this article we describe how white light interferometry, and optical profilometry (OP) in general, combined with generic surface analysis software, can be used for materials science and engineering tasks. In this article, a number of applications of white light interferometry for investigation of surface modifications in mass spectrometry, and wear phenomena in tribology and lubrication are demonstrated. We characterize the products of the interaction of semiconductors and metals with energetic ions (sputtering), and laser irradiation (ablation), as well as
ex situ
measurements of wear of tribological test specimens.Specifically, we will discuss:
- Aspects of traditional ion sputtering-based mass spectrometry such as sputtering rates/yields measurements on Si and Cu and subsequent time-to-depth conversion.
- Results of quantitative characterization of the interaction of femtosecond laser irradiation with a semiconductor surface. These results are important for applications such as ablation mass spectrometry, where the quantities of evaporated material can be studied and controlled via pulse duration and energy per pulse. Thus, by determining the crater geometry one can define depth and lateral resolution versus experimental setup conditions.
- Measurements of surface roughness parameters in two dimensions, and quantitative measurements of the surface wear that occur as a result of friction and wear tests.
148.
Tuula Dahlman Marja Mäntysalo Palle V. Rasmussen L. L. Skovl⊘kke 《Archives of animal nutrition》2013,67(6):443-454
The influence of dietary protein, methionine, and lysine on leather quality in blue fox pelts was studied. The pelt material originated from animals in two consecutive feeding trials (Exp. 1 and Exp. 2) with three protein levels: conventional, slightly lowered, and very low. The two lowest protein diets were fed as such or as supplemented with methionine or with lysine (lysine only in Exp. 2). The following physical leather properties were measured: breaking load (BRL), tensile strength (TEN), relative elongation at break (PEB), straining of skins at pelting, and shrinkage at dressing. A decline in the dietary protein content reduced BRL and, hence, leather firmness, and increased straining and the corresponding shrinking in Exp. 1. The supplemented methionine tended to improve leather strength and elasticity by increasing TEN and PEB in Exp. 1, whereas lysine elicited no response. Methionine supplementation at the slightly lowered protein level increased BRL in both experiments by almost 10% as compared with the respective non-supplemented diet. We conclude that with high protein quality diets, a level of 200g/kg DM (as digestible protein) appears to be adequate for producing pelts with firm, elastic leather, provided that an adequate amount of methionine is included in the diet. 相似文献
149.
Oh DK 《Applied microbiology and biotechnology》2007,76(1):1-8
d-Tagatose has attracted a great deal of attention in recent years due to its health benefits and similar properties to sucrose.
d-Tagatose can be used as a low-calorie sweetener, as an intermediate for synthesis of other optically active compounds, and
as an additive in detergent, cosmetic, and pharmaceutical formulation. Biotransformation of d-tagatose has been produced using several biocatalyst sources. Among the biocatalysts, l-arabinose isomerase has been mostly applied for d-tagatose production because of the industrial feasibility for the use of d-galactose as a substrate. In this article, the characterization of many l-arabinose isomerases and their d-tagatose production is compared. Protein engineering and immobilization of the enzyme for increasing the conversion rate
of d-galactose to d-tagatose are also reviewed. 相似文献
150.
工程菌人溶菌酶的纯化和性质 总被引:14,自引:0,他引:14
将人溶菌酶工程菌株在发酵培养、菌体经超声破碎、变性和复性后所得的粗酶液经ExpressIon S阳离子交换柱层析,得到电泳纯的酶,比活达到48KG*4]000u/mg。此酶的最适pH为6.5;等电点为8.91;对溶壁微球菌的米氏常数Km=0.0311mg/mL;60℃保温30〖KG*4]min,酶活力剩余48.3%。N末端氨基酸序列除了第一个Met,其余4个与预期相符。一些重金属离子对酶的活性影响不尽相同,在0.01 相似文献