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排序方式: 共有1577条查询结果,搜索用时 31 毫秒
1.
微生物纤维素酶的应用研究   总被引:56,自引:0,他引:56  
我国纤维素酶的应用研究近年来取得了很大进展。阐述了纤维素分解菌的选育 ,酶学性质以及在发酵、纺织和洗涤剂工业中的应用。  相似文献
2.
Molecular and biotechnological aspects of xylanases   总被引:53,自引:0,他引:53  
Hemicellulolytic microorganisms play a significant role in nature by recycling hemicellulose, one of the main components of plant polysaccharides. Xylanases (EC 3.2.1.8) catalyze the hydrolysis of xylan, the major constituent of hemicellulose. The use of these enzymes could greatly improve the overall economics of processing lignocellulosic materials for the generation of liquid fuels and chemicals. Recently cellulase-free xylanases have received great attention in the development of environmentally friendly technologies in the paper and pulp industry. In microorganisms that produce xylanases low molecular mass fragments of xylan and their positional isomers play a key role in regulating its biosynthesis. Xylanase and cellulase production appear to be regulated separately, although the pleiotropy of mutations, which causes the elimination of both genes, suggests some linkage in the synthesis of the two enzymes. Xylanases are found in a cornucopia of organisms and the genes encoding them have been cloned in homologous and heterologous hosts with the objectives of overproducing the enzyme and altering its properties to suit commercial applications. Sequence analyses of xylanases have revealed distinct catalytic and cellulose binding domains, with a separate non-catalytic domain that has been reported to confer enhanced thermostability in some xylanases. Analyses of three-dimensional structures and the properties of mutants have revealed the involvement of specific tyrosine and tryptophan residues in the substrate binding site and of glutamate and aspartate residues in the catalytic mechanism. Many lines of evidence suggest that xylanases operate via a double displacement mechanism in which the anomeric configuration is retained, although some of the enzymes catalyze single displacement reactions with inversion of configuration. Based on a dendrogram obtained from amino acid sequence similarities the evolutionary relationship between xylanases is assessed. In addition the properties of xylanases from extremophilic organisms have been evaluated in terms of biotechnological applications.  相似文献
3.
Cellulose degrading enzymes and their potential industrial applications   总被引:38,自引:0,他引:38  
Bioconversion of cellulose to soluble sugars and glucose is catalyzed by a group of enzymes called cellulases. Microorganisms including fungi, bacteria and actinomycetes produce mainly three types of cellulase components—endo-1,4-β-D-glucanase, exo-1,4-β-D-glucanase and β-glucosidase—either separately or in the form of a complex. Over the last several decades, cellulases have become better understood at a fundamental level; nevertheless, much remains to be learnt. The tremendous commercial potential of cellulases in a variety of applications remains the driving force for research in this area. This review summarizes the present state of knowledge on microbial cellulases and their applications.  相似文献
4.
木聚糖酶的分子生物学及其应用   总被引:34,自引:0,他引:34  
木聚糖是一种多聚五碳糖,是植物细胞中的主要半纤维素成分,木聚糖酶是可将木聚糖降解成低聚木糖和木糖的复合酶系,综述了木聚糖酶分子生物学上的研究进展及其在饲料,造纸,食品,能源工业上的应用。  相似文献
5.
利用多菌种混合发酵转化玉米秸秆的研究   总被引:32,自引:0,他引:32  
该文系统地研究了高产纤维素酶生产菌(TrichodermaresiTB9701)与饲料酵母混合共发酵玉米秸秆粉对合成菌体蛋白质和利用纤维素的关系,优选出一条最佳的共发酵工艺途径和条件。研究表明在以氨法处理的玉米秸秆为底物的TB-9701与饲料酵母菌的混合菌共发酵正交实验中,于pH5.0,30℃的条件下200r/min的恒温、恒速摇瓶培养8d,经测定发酵液终产物中粗蛋白(SCP)的含量达到了23.70%,总秸秆纤维的转化率达到70%以上。  相似文献
6.
Xylanases, xylanase families and extremophilic xylanases   总被引:32,自引:0,他引:32  
Xylanases are hydrolytic enzymes which randomly cleave the beta 1,4 backbone of the complex plant cell wall polysaccharide xylan. Diverse forms of these enzymes exist, displaying varying folds, mechanisms of action, substrate specificities, hydrolytic activities (yields, rates and products) and physicochemical characteristics. Research has mainly focused on only two of the xylanase containing glycoside hydrolase families, namely families 10 and 11, yet enzymes with xylanase activity belonging to families 5, 7, 8 and 43 have also been identified and studied, albeit to a lesser extent. Driven by industrial demands for enzymes that can operate under process conditions, a number of extremophilic xylanases have been isolated, in particular those from thermophiles, alkaliphiles and acidiphiles, while little attention has been paid to cold-adapted xylanases. Here, the diverse physicochemical and functional characteristics, as well as the folds and mechanisms of action of all six xylanase containing families will be discussed. The adaptation strategies of the extremophilic xylanases isolated to date and the potential industrial applications of these enzymes will also be presented.  相似文献
7.
一株纤维素分解菌的分离与筛选   总被引:32,自引:0,他引:32  
以新华滤纸为唯一碳源,从垃圾堆肥中筛选能够分解纤维素的菌株共39株,采用刚果红鉴别培养基进行识别,获取透明圈较大的菌株10株,在此基础上,进行液体培养,测定酶活,得到1株酶活较高的曲霉B-6(Aspergillus sp)。将B-6与绿色木霉(Trichoderma sp)AS3.3711进行了参比试验,比对筛选工作进行评定,经过固体,液体发酵对比试验,发现B-6与AS3.371有相近的产酶性能,B-6在固,液发酵中酶活分别达到39.2IU,14.9IU,而S3.3711则分别为16.6IU与15.7IU,且B-6较AS3.3711有更强的液化CMC的能力,B-6在24h内即能使3%CMC完全液化,而S3.3711则需96h。  相似文献
8.
纤维素酶分子结构和功能研究进展   总被引:31,自引:0,他引:31       下载免费PDF全文
概述了近10年来利用结构生物学和蛋白质工程技术在纤维素酶分子结构和功能方面研究的进展,包括:酶分子结构域的拆分、催化域和纤维素结合结构域的结构和功能的研究,纤维素酶的分子折叠.并展望了该领域的研究前景.  相似文献
9.
木聚糖酶活力测定条件研究   总被引:29,自引:2,他引:27  
用DNS法测木聚糖酶活力,分析测定条件对测定结果的影响。结果表明,在不同的条件下测定酶活力会得到不同的木聚糖酶活力测定值。其中,酶液用量、酶解反应的时间对测定结果的影响较大,酶液稀释度、DNS显色时间、DNS的用量,对测定结果也有一定的髟响。测定木聚糖酶活力的适宜条件为:酶液量/1%木聚糖液量1/9(V/V);酶解反应时间:10min;DNS用量2—2.5ml;DNS显色时间2—5min。  相似文献
10.
壳聚糖固定化纤维素酶的研究   总被引:29,自引:1,他引:28       下载免费PDF全文
以蟹壳为原料提取壳聚糖,用戊二醛作交联剂,将纤维素酶固定于壳聚糖上.同时探讨了一定量干壳聚糖载体与交联剂浓度、给酶量等关系的最适固定化酶条件,并对固定化酶的热稳定性、操作稳定性、米氏常数、最适温度、离子强度的影响及使用半衰期等理化性质进行了探讨.  相似文献
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