全文获取类型
收费全文 | 152篇 |
免费 | 3篇 |
专业分类
化学 | 101篇 |
力学 | 3篇 |
数学 | 39篇 |
物理学 | 12篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 11篇 |
2012年 | 13篇 |
2011年 | 10篇 |
2010年 | 7篇 |
2009年 | 6篇 |
2008年 | 8篇 |
2007年 | 9篇 |
2006年 | 4篇 |
2005年 | 10篇 |
2004年 | 6篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1987年 | 1篇 |
1982年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有155条查询结果,搜索用时 15 毫秒
121.
Overexpression of glucose-6-phosphate dehydrogenase in genetically modified Saccharomyces cerevisiae
Lojudice Fernando H. Silva Daniel P. Zanchin Nilson I. T. Oliveira Carla C. Pessoa Adalberto 《Applied biochemistry and biotechnology》2001,91(1-9):161-169
Glucose-6-phosphate dehydrogenase (G6PD) (EC 1.1.1.49) is an abun dant enzyme in Saccharomyces cerevisiae. This enzyme is of great interest as an analytical reagent because it is used in a large number of quantitative assays. A
strain of S. cerevisiae was genetically modified to improve G6PD production during aerobic culture. The modifications are based on cloning the G6PD
sequence under the control of promoters that are upregulated by the carbon source used for yeast growth. The results showed
that S. cerevisiae acquired from a commercial source and the same strain produced by aerobic cultivation under controlled conditions provided
very similar G6PD. However, G6PD production by genetically modified S. cerevisiae produced very high enzyme activity and showed to be the most effective procedure to obtain glucose-6-phosphate dehydrogenase.
As a consequence, the cost of producing G6PD can be significantly reduced by using strains that contain levels of G6PD up
to 14-fold higher than the level of G6PD found in commercially available strains. 相似文献
122.
Gregório Pacelli Bessa Leandro F. Pessoa Marco Rigoli 《Israel Journal of Mathematics》2018,226(2):703-736
In this paper we study non-compact self-shrinkers first in general codimension and then in codimension 1. We respectively prove some vanishing theorems giving rise to rigidity of the self-shrinker and then estimates involving the higher order mean curvatures for the oriented case. The paper ends with some results on their index when considered as appropriate \(\bar f\)-minimal hypersurfaces. 相似文献
123.
Bessa G. Pacelli Lima Barnabe P. Pessoa Leandro F. 《Annali di Matematica Pura ed Applicata》2015,194(1):109-130
Annali di Matematica Pura ed Applicata (1923 -) - Jorge–Koutrofiotis (Am J Math 103:711–725, 1980) and Pigola et al. (Memoirs Am Math Soc 174(822), 2005) proved sharp sectional... 相似文献
124.
125.
Santos Ana Caroline F. Luz Rita C. S. Damos Flavio S. Santana Antônio Euzébio Goulart Pessoa Danilo Galdino Navarro Marcelo Goulart Marilia O. F. 《Journal of Solid State Electrochemistry》2020,24(8):1835-1843
Journal of Solid State Electrochemistry - In this work, the boron-doped diamond electrode (BDDE) was used for the electrocatalytic oxidation of N-acetylcysteine (NAC), in the presence of lipoic... 相似文献
126.
Pedro Ado Joo Reboleira Marco Teles Beatriz Santos Ndia Ribeiro Carlos M. Teixeira Mafalda Guedes Joo Costa Pessoa Susana Bernardino 《Molecules (Basel, Switzerland)》2021,26(10)
The chemical modification of porphyran hydrocolloid is attempted, with the objective of enhancing its antioxidant and antimicrobial activities. Sulfated galactan porphyran is obtained from commercial samples of the red algae Porphyra dioica using Soxhlet extraction with water at 100 °C and precipitation with isopropyl alcohol. The extracted porphyran is then treated with modified L-tyrosines in aqueous medium in the presence of NaOH, at ca. 70 °C. The modified tyrosines L1 and L2 are prepared through a Mannich reaction with either thymol or 2,4-di-tert-butylphenol, respectively. While the reaction with 2,4-di-tert-butylphenol yields the expected tyrosine derivative, a mixture of products is obtained with thymol. The resulting polysaccharides are structurally characterized and the respective antioxidant and antimicrobial activities are determined. Porphyran treated with the N-(2-hydroxy-3,5-di-tert-butyl-benzyl)-L-tyrosine derivative, POR-L2, presents a noticeable superior radical scavenging and antioxidant activity compared to native porphyran, POR. Furthermore, it exhibited some antimicrobial activity against S. aureus. The surface morphology of films prepared by casting with native and modified porphyrans is studied by SEM/EDS. Both POR and POR-L2 present potential applicability in the production of films and washable coatings for food packaging with improved protecting characteristics. 相似文献
127.
Maria Conceição M. Torres José Gustavo L. Almeida Raimundo Braz‐Filho Edilberto R. Silveira Otília Deusdênia L. Pessoa 《Magnetic resonance in chemistry : MRC》2012,50(1):74-78
From the leaves of Solanum campaniforme, two new spirosolane alkaloids β‐acetoxyl‐(25S)‐22βN‐spirosol‐4‐en‐3‐one (1) and β‐hydroxyl‐(25S)‐22βN‐spirosol‐4‐en‐3‐one (4) were isolated along with two other known alkaloids of the same class (25S)‐22βN‐spirosol‐1,4‐dien‐3‐one (2) and (25S)‐22βN‐spirosol‐4‐en‐3‐one (3), which are reported for the first time as natural products. The structures of all alkaloids were established after an extensive analysis by 1D and 2D NMR spectroscopy (COSY, HSQC, HMBC and NOESY) as well as HRESIMS. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
128.
Wildson Max B. da Silva Edilberto R. Silveira Otilia Deusdênia L. Pessoa 《Magnetic resonance in chemistry : MRC》2010,48(6):486-489
Two new labdane diterpenes, 6α‐malonyloxy‐ethyl ester manoyl oxide and bis‐6α‐dioxymanoylmalonate, together with the known 6α‐hydroxymanoyl oxide, 6α‐malonyloxymaloyl oxide and betulinic acid were isolated from leaves of Stemodia trifoliata. Their structures were elucidated by spectroscopic studies (IR and HR‐ESI‐MS), including an extensive NMR (COSY, HSQC, HMBC and NOESY) analysis. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
129.
Hasmann Francislene-Andréia Pessoa Adalberto Roberto Inês-Conceição 《Applied biochemistry and biotechnology》2001,91(1-9):719-728
β-Xylosidase recovery by micelles using cetyl trimethyl ammonium bromide (CTAB) cationic surfactant was verified under different
experimental conditions. A 25−1 fractional factorial design with center points was employed to verify the influence of the following factors on enzyme extraction:
pH (x
1), CTAB concentration (x
2), electrical conductivity (x
3), hexanol concentration (x
4), and butanol concentration (x
5). Statistical analysis of the results shows that of the fivevariables studied only hexanol and electrical conductivity did
not have significant effects on the recovery of β-xylosidase. The other factors had significant effects in increasing order:
(x
1)>(x
2)>(x
5). The model predicts a recovery value of about 45%, which is similar to that obtained experimentally (43.5%). 相似文献
130.
Aloisio Pessoa de Araujo 《Journal of multivariate analysis》1978,8(4):598-613
It is shown, with the use of a concentration inequality of LeCam, that associated with an infinitely divisible random variable with values in a separable Banach space there is a Lévy-Khintchine formula. A partial converse of this fact is also proved. Relations between the continuity of the compound Poisson and the Gaussian variables associated with a Lévy measure are studied. A central limit theorem is obtained and examples are given. 相似文献