全文获取类型
收费全文 | 299篇 |
免费 | 5篇 |
国内免费 | 39篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 5篇 |
2015年 | 13篇 |
2014年 | 8篇 |
2013年 | 8篇 |
2012年 | 10篇 |
2011年 | 11篇 |
2010年 | 12篇 |
2009年 | 23篇 |
2008年 | 25篇 |
2007年 | 22篇 |
2006年 | 12篇 |
2005年 | 16篇 |
2004年 | 17篇 |
2003年 | 10篇 |
2002年 | 14篇 |
2001年 | 14篇 |
2000年 | 7篇 |
1999年 | 15篇 |
1998年 | 9篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 11篇 |
1993年 | 6篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有343条查询结果,搜索用时 46 毫秒
291.
F. Buchholz R. A. H. Vetter 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(1):28-37
N-acetyl--d-glucosaminidase, a chitin-degrading enzyme, is highly active in the integument and digestive tract of euphausiids. The enzyme was used as a model to compare temperature-dependent enzymatic parameters of Antarctic krill, Euphausia superba, with those of a euphausiid species (Meganyctiphanes norvegica) found in both the Scandinavian Kattegat and the Mediterranean. Other species examined were an Antarctic isopod, Serolis polita, and a tropical crab, Ocypode ryderi. Enzyme isoforms of NAGase were isolated chromatographically. Temperature optimum (between 30 and 53 °C) and activation-energy (47–59 kJ·mol-1) of isoenzymes were generally unrelated to genotypic cold adaptation. Although pH profiles were temperature-dependent, there was no apparent temperature-related control of activities by pH in the experienced physiological range. In contrast, apparent Michaelis constants showed minima at ambient water temperatures (total range: 0.1–0.6 mol·l-1). Potentially, enzyme variants play a role in acclimatisation regulated by Michaelis constants. Apparently, the rate-limiting effects of polar temperatures are partly compensated in the Antarctic crustaceans by construction of enzymes with substrate affinities similar to those of species from warmer climates. The significance of apparent Michaelis constants in evaluating mechanisms of metabolic cold compensation is discussed. Necessary additional experimental approaches are highlighted.Abbreviations CPB
citrate-phosphate buffer
- FPLC
fast protein liquid chromatography
-
K
m
app
apparent Michaelis constant
- LC
liquid chromatography
- MW
molecular weight
- NAGase
N-acetyl--d-glucosaminidase 相似文献
292.
四甲基氯化铵在PCR扩增小麦基因中的关键作用 总被引:9,自引:1,他引:8
利用高简并性引物,用PCR法从小麦DNA或cDNA中合成小麦几丁质酶基因、葡
聚糖酶基因和苯丙氨酸解氨酶基因片段。在PCR反应中添加四甲基氯化铵(TMACl)是合成这些特异基因片段的关键。合成的PCR片段都经末端补齐和磷酸化后用于克隆。核酸序列分析证实,这些PCR产物分别与用于设计PCR引物的基因具有高度的同源性。
Abstract:In the presence of tetramethy1 ammonium chloride(TMAC1),a chitinase gene sequence,a phenylalanine ammonia-lyase gene sequence and a glucanase cDNA sequence of wheat were amplified with highly degenerate primers by PCR.The inclusion of TMAC1 in the PCR reactions was essential for successful amplification of the desired sequences from genomic DNA or cDNA in wheat.The ends of the PCR fragments were made flush and phosphorylated prior to cloning.Sequence analyses of the above PCR fragments confirmed their identities,showing high sequence similarities to the genes used for the design of PCR primers. 相似文献
293.
294.
What are the roles of chitinases in the growing fungus? 总被引:15,自引:0,他引:15
295.
Introduction and constitutive expression of a rice chitinase gene in bread wheat using biolistic bombardment and the bar gene as a selectable marker 总被引:13,自引:0,他引:13
W. P. Chen X. Gu G. H. Liang S. Muthukrishnan P. D. Chen D. J. Liu B. S. Gill 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(8):1296-1306
Our long-term goal is to control wheat diseases through the enhancement of host plant resistance. The constitutive expression
of plant defense genes to control fungal diseases can be engineered by genetic transformation. Our experimental strategy was
to biolistically transform wheat with a vector DNA containing a rice chitinase gene under the control of the CaMV 35 S promoter
and the bar gene under control of the ubiquitin promoter as a selectable marker. Immature embryos of wheat cv ‘Bobwhite’ were bombarded
with plasmid pAHG11 containing the rice chitinase gene chi11 and the bar gene. The embryos were subcultured on MS2 medium containing the herbicide bialaphos. Calli were then transferred to a regeneration
medium, also containing bialaphos. Seventeen herbicide-resistant putative transformants (T0) were selected after spraying with 0.2% Liberty, of which 16 showed bar gene expression as determined by the phosphinothricin acetyltransferase (PAT) assay. Of the 17 plants, 12 showed the expected
35-kDa rice chitinase as revealed by Western blot analysis. The majority of transgenic plants were morphologically normal
and self-fertile. The integration, inheritance and expression of the chi11 and bar genes were confirmed by Southern hybridization, PAT and Western blot analysis of T0 and T1 transgenic plants. Mendelian segregation of herbicide resistance was observed in some T1 progenies. Interestingly, a majority of the T1 progeny had very little or no chitinase expression even though the chitinase transgene was intact. Because PAT gene expression
under control of the ubiquitin promoter was unaffected, we conclude that the CaMV 35 S promoter is selectively inactivated
in T1 transgenic wheat plants.
Received: 12 May 1998 / Accepted: 15 May 1998 相似文献
296.
中国棉铃虫核型多角体病毒几丁质酶基因的定位与克隆 总被引:10,自引:2,他引:8
以α32PdATP标记含CfMNPV几丁质酶基因的重组质粒为探针,在68℃条件下对棉铃虫单粒包埋核型多角体病毒(HaSNPV)进行Southern杂交,将HaSNPV的几丁质酶基因分别定位在BamHIE、BglⅡE、EcoRIG、HindⅢF、XbaIH、BamHI+HindIIM和BamHI+XbaIH,并以pTZ19R为载体获得了XbaIH片段克隆。 相似文献
297.
The most comprehensive studies on a plant lysozyme (EC 3.2.1.17) are those on the enzyme from papaya (Carica papaya) latex, published in 1967 and 1969. However, the N-terminal amino acid sequence of five amino acid sequence of this enzyme,
determined by manual Edman degradation, did not allow assignment to any of the much later-classified families of glycosyl
hydrolases. N-Terminal sequence analysis of 22 residues of papaya lysozyme now shows unambiguously that the enzyme belongs
to the family 19 chitinases. It has properties similar to those of basic class I chitinases with lysozyme activity, such as
cleavage specificity at the C-1 of N-acetylmuramic acid with inversion of configuration, but as it lacks an N-terminal hevein domain, it should be classified
as a class II chitinase.
Received: 3 February 1999 / Accepted 25 July 1999 相似文献
298.
R. Radjacommare A. Kandan R. Nandakumar R. Samiyappan 《Journal of Phytopathology》2004,152(6):365-370
Twenty‐two strains of Pseudomonas fluorescens isolated from the rhizosphere soil of nine plant species were screened in vitro for their inhibitory effect on the mycelial growth of the rice sheath blight fungus, Rhizoctonia solani. Of the 22 strains, two promising strains (Pf1 and FP7) were assessed for their effect on seedling vigour and their ability to promote growth in vitro of four cultivars of rice. Both bacterial strains induced systemic resistance in rice cv. IR 50, which is susceptible to sheath blight. After inoculation of the sheaths with the pathogen, Pseudomonas‐treated plants showed an increase in chitinase activity significantly higher than that of untreated control plants. A twofold increase in chitinase activity occurred 2 days after inoculation of plants with the pathogen. Western blot analysis of chitinase indicated the expression of 28 and 38 kDa proteins in rice sheaths against R. solani. Increased induction of the pathogenesis‐related chitinase isoform in Pseudomonas‐treated rice in response to R. solani infection indicates that the induced chitinase has a definite role in suppressing disease development. 相似文献
299.
Cloning and sequencing of a gene encoding the 69-kDa extracellular chitinase of Janthinobacterium lividum 总被引:2,自引:0,他引:2
Andrew P. Gleave Robert K. Taylor Bret A.M. Morris David R. Greenwood 《FEMS microbiology letters》1995,131(3):279-288
Abstract Janthinobacterium lividum secretes a major 56-kDa chitinase and a minor 69-kDa chitinase. A chitinase gene was defined on a 3-kb fragment of clone pRKT10, by virtue of fluorescent colonies in the presence of 4-methylumbelliferyl-β-d-N,N',N"-chitotrioside. Nucleotide sequencing revealed an 1998-bp open reading frame with the potential to encode a 69 716-Da protein with amino acid sequences similar to those in other chitinases, suggesting it encodes the minor chitinase (Chi69). Chitinase activity of Escherichia coli (pRKTIO) lysates was detected mainly in the periplasmic fraction and immunoblotting detected a 70-kDa protein in this fraction. Chi69 has an N-terminal secretory leader peptide preceding two probable chitin-binding domains and a catalytic domain. These functional domains are separated by linker regions of proline-threonine repeats. Amino acid sequencing of cyanogen bromide cleavage-derived peptides from the major 56-kDa chitinase suggested that Chi69 may be a precursor of Chi56. In addition, an N-terminally truncated version of Chi69 retained chitinase activity as expected if in vivo processing of Chi69 generates Chi56. 相似文献
300.
气单胞菌Aeromonassp.2016菌株能产生多种几丁质酶,其中的胞外酶C可能聚集于细胞外周胞质。为了避免破碎菌体而产生过多的杂蛋白,探索了用渗压震扰法(osmoticshock)来释放这部分酶。主要步骤是:先将菌体悬浮在20%蔗糖-0.03mol/LTris-HCI(pH8.0)高渗透压的溶液中,再快速转移到纯水低渗透压溶液中,产生瞬间渗压震荡,释放细胞外周胞质中的酶。结果表明,通过渗压震扰法释放出的酶纯度最高,比活力达到142.79U/g,比培养液上清液的54.46U/g和菌体破碎样品的14.66U/g分别高1.6倍和8.7倍,可用于纯化目的蛋白。 相似文献