全文获取类型
收费全文 | 229篇 |
免费 | 7篇 |
国内免费 | 8篇 |
专业分类
化学 | 229篇 |
综合类 | 8篇 |
物理学 | 7篇 |
出版年
2022年 | 1篇 |
2021年 | 14篇 |
2020年 | 15篇 |
2019年 | 14篇 |
2018年 | 14篇 |
2016年 | 13篇 |
2015年 | 14篇 |
2014年 | 3篇 |
2013年 | 8篇 |
2012年 | 11篇 |
2011年 | 10篇 |
2010年 | 5篇 |
2009年 | 7篇 |
2008年 | 12篇 |
2007年 | 15篇 |
2006年 | 12篇 |
2005年 | 11篇 |
2004年 | 8篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有244条查询结果,搜索用时 62 毫秒
241.
Polygalacturonases are part of the group of enzymes involved in pectin degradation. The aim of this work was to investigate
some of the factors affecting polygalacturonase production by an Aspergillus giganteus strain and to characterize this pectinolytic activity. Several carbon sources, both pure substances and natural substrates,
were tested in standing cultures, and the best results were obtained with orange bagasse and purified citrus pectin. On citrus
pectin as sole carbon source, the highest extracellular activity (9.5 U/ml and 40.6 U/mg protein) was obtained in 4.5-day-old
cultures shaken at 120 rpm, pH 3.5 and 30°C, while on orange bagasse, the highest extracellular activity (48.5 U/ml and 78.3 U/mg
protein) was obtained in 3.5-day-old cultures shaken at 120 rpm, pH 6.0 and 30°C. Optimal polygalacturonase activity was observed
in assays conducted at pH 5.5–6.5 and 55–60°C. The activity showed good thermal stability, with half-lives of 90 and 30 min
when incubated at 55 and 60°C, respectively. High stability was observed from pH 4.5 to 8.5; more than 90% of the activity
remained after 24 h in this pH range. 相似文献
242.
分别应用含有120μmol·L-1 La3+,50μmol·L-1 Cd2+,100μmol·L-1 Cd2+,50μmol·L-1 Cd2++120μmol·L-1 La3+,100μmol·L-1Cd2++120μmol·L-1 La3+的培养基培养黑曲霉,3 d后测定黑曲霉菌球的生物量及其胞内超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)、过氧化物酶(POD)和谷胱甘肽-S-转移酶(GST)活性及脂质过氧化产物(MDA)的变化。结果表明,50和100μmol.L-1Cd2+降低了黑曲霉生物量和五种抗氧化酶活性,并诱导了MDA产物的升高。与Cd2+单一处理比较,50μmol·L-1 Cd2++120μmol·L-1 La3+和100μmol·L-1 Cd2++120μmol·L-1 La3+处理组均不同程度上诱导了五种抗氧化酶活性的升高,并降低了MDA的积累水平。其中,120μmol·L-1 La3+对50μmol·L-1 Cd2+氧化胁迫的缓解效应明显高于100μmol·L-1 Cd2+。因此,La对黑曲霉中低剂量Cd胁迫的缓解效应比较显著,而对高剂量Cd的拮抗效应不明显。 相似文献
243.
HUANGHui-li LINWen-luan LINJian-ming 《高等学校化学研究》2004,20(2):156-158
Chitin from cell walls of Aspergillus Niger mycelium was prepared. A new method for the preparation of high deacetylation degree chitosan was studied in a dilute sodium hydroxide solution at a high pressure. The experimental results indicate that the deacetylation degree of the chitosan can reach 80% under the condition of a 5.00 mol/L sodium hydroxide solution at 0. 1 MPa of pressure for 1 h. This method shows the advantages of the applications in the industry production and environment protection. 相似文献
244.
Irene Gonzalez-Jimenez Jose Lucio Alejandra Roldan Laura Alcazar-Fuoli Emilia Mellado 《Molecules (Basel, Switzerland)》2021,26(19)
Invasive aspergillosis, mainly caused by Aspergillus fumigatus, can lead to severe clinical outcomes in immunocompromised individuals. Antifungal treatment, based on the use of azoles, is crucial to increase survival rates. However, the recent emergence of azole-resistant A. fumigatus isolates is affecting the efficacy of the clinical therapy and lowering the success rate of azole strategies against aspergillosis. Azole resistance mechanisms described to date are mainly associated with mutations in the azole target gene cyp51A that entail structural changes in Cyp51A or overexpression of the gene. However, strains lacking cyp51A modifications but resistant to clinical azoles have recently been detected. Some genes have been proposed as new players in azole resistance. In this study, the gene hmg1, recently related to azole resistance, and its paralogue hmg2 were studied in a collection of fifteen azole-resistant strains without cyp51A modifications. Both genes encode HMG-CoA reductases and are involved in the ergosterol biosynthesis. Several mutations located in the sterol sensing domain (SSD) of Hmg1 (D242Y, G307D/S, P309L, K319Q, Y368H, F390L and I412T) and Hmg2 (I235S, V303A, I312S, I360F and V397C) were detected. The role of these mutations in conferring azole resistance is discussed in this work. 相似文献