全文获取类型
收费全文 | 152篇 |
免费 | 8篇 |
国内免费 | 8篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 2篇 |
2015年 | 8篇 |
2014年 | 7篇 |
2013年 | 9篇 |
2011年 | 12篇 |
2010年 | 3篇 |
2009年 | 12篇 |
2008年 | 15篇 |
2007年 | 15篇 |
2006年 | 5篇 |
2005年 | 4篇 |
2004年 | 3篇 |
2003年 | 6篇 |
2002年 | 11篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有168条查询结果,搜索用时 31 毫秒
1.
Coexistence of incompatible plasmids in a bacterial population living under a feast and famine regime 总被引:1,自引:0,他引:1
Nelly Van der Hoeven 《Journal of mathematical biology》1986,24(3):313-325
A model is formulated to examine the possibility of (co)existence of plasmids of the same incompatibility and surface exclusion group in a bacterial population living under a feast-and-famine regime. The condition is given under which a growth rate decreasing plasmid can invade a bacterial population. It appears that in case only one plasmid type is present, the frequency of plasmid bearers will tend to a stable equilibrium if the food supply at each growth site gets exhausted and if both plasmid-free and plasmid-bearing bacteria need an equal quantity of food per cell division. If these two conditions are not satisfied, the frequency of plasmid-bearers might oscillate. Two plasmids will sometimes be able to coexist, but only if they follow different survival strategies; one with a high conjugational transfer rate and a lower fitness of its host, and the other with a low transfer rate and a higher host fitness. Coexistence of three plasmids of the same surface exclusion group is impossible. 相似文献
2.
《Animal : an international journal of animal bioscience》2021,15(12):100410
Timed artificial insemination (TAI) is an efficient reproductive technology in batch farrowing production that aids management in pig farms. However, the effect of TAI on the reproduction performance is still controversial. This study aimed to evaluate the effects of two TAI protocols on the reproductive performance of primiparous sows. A total of 332 weaned sows were randomly allocated into three treatments. Sows assigned to Control (n = 110) were untreated and inseminated on each day in oestrus after weaning. Sows assigned to eG-TAI (n = 112) received equine chorionic gonadotropin (eCG) 24 h after weaning and gonadotropin-releasing hormone (Gonadorelin: GnRH) at oestrus, and were inseminated at 8 and 32 h later if oestrus at 0800, or 16 and 40 h later if oestrus at 1600. Sows assigned to 2e-TAI (n = 110) received eCG and GnRH 24 h and 96 h after weaning, respectively, and were inseminated 16 and 40 h after GnRH administration. Sows showing oestrus at GnRH administration or 64 h after were inseminated immediately, for a total of three inseminations. Ultrasonographic evaluations were performed to determine the follicular diameter and time of ovulation. Most sows in the 2e-TAI and eG-TAI groups ovulated 0–48 h after the GnRH injection. Our results indicated that oestrus rate within seven days after weaning in the experimental groups was higher, and weaning-to-oestrus interval was shorter than in the control group (99.3 h vs 113.5 h, P < 0.05). The breeding and farrowing rates in the experimental groups were significantly higher than in the control group (P < 0.05), while the numbers of total born, live-born and stillborn were not different among the three groups (Control: 12.7, 11.6 and 1.1; 2e-TAI: 12.4, 11.3 and 1.0; eG-TAI: 12.0, 11.4 and 0.4, respectively). These results indicated that TAI could ensure a high farrowing rate in primiparous sows under batch farrowing management. 相似文献
3.
Don A. Baldwin Christopher P. Sarnowski Sabrina A. Reddy Ian A. Blair Margie Clapper Philip Lazarus Mingyao Li Joshua E. Muscat Trevor M. Penning Anil Vachani Alexander S. Whitehead 《Journal of biomolecular techniques》2013,24(4):198-217
A microarray (LungCaGxE), based on Illumina BeadChip technology, was developed for high-resolution genotyping of genes that are candidates for involvement in environmentally driven aspects of lung cancer oncogenesis and/or tumor growth. The iterative array design process illustrates techniques for managing large panels of candidate genes and optimizing marker selection, aided by a new bioinformatics pipeline component, Tagger Batch Assistant. The LungCaGxE platform targets 298 genes and the proximal genetic regions in which they are located, using ∼13,000 DNA single nucleotide polymorphisms (SNPs), which include haplotype linkage markers with a minimum allele frequency of 1% and additional specifically targeted SNPs, for which published reports have indicated functional consequences or associations with lung cancer or other smoking-related diseases. The overall assay conversion rate was 98.9%; 99.0% of markers with a minimum Illumina design score of 0.6 successfully generated allele calls using genomic DNA from a study population of 1873 lung-cancer patients and controls. 相似文献
4.
Long chain polyunsaturated fatty acid production and partitioning to triacylglycerols in four microalgae 总被引:1,自引:0,他引:1
Gas chromatographic profiling of fatty acids was performed during the growth cycle of four marine microalgae in order to establish which, if any, of these could act as a reliable source of genes for the metabolic engineering of long chain polyunsaturated fatty acid (LC-PUFA) synthesis in alternative production systems. A high-throughput column based method for extraction of triacylglycerols (TAGs) was used to establish how much and at what stage in the growth phase LC-PUFAs partition to storage lipid in the different species. Differences in the time course of production and incorporation of docosahexaenoic acid (22:6n-3, DHA) and eicosapentaenoic acid (20:5n-3, EPA) into TAGs were found in the marine microalgae Nannochloropsis oculata (Eustigmatophyceae), Phaeodactylum tricornutum and Thalassiosira pseudonana (Bacillariophyceae), and the Haptophyte Pavlova lutheri. Differences were not only observed between species but also during the different phases of growth within a species. A much higher percentage of the total cellular EPA was partitioned to TAGs in stationary phase cells of N. oculata compared to P. tricornutum. Although P. tricornutum produces DHA it does not partition it to TAGs. Both T. pseudonana and P. lutheri produce EPA and DHA and partition these to TAGs during the stationary phase of growth. These two species are therefore good candidates for further biochemical and molecular analysis, in order to understand and manipulate the processes that are responsible for the incorporation of LC-PUFAs into storage oils. 相似文献
5.
Quantitative detection of probiotic Bifidobacterium strains in bacterial mixtures by using real-time PCR 总被引:2,自引:0,他引:2
Strain-specific rRNA-targeted primers were designed for the quantitative detection of Bifidobacterium infantis Y1, B. breve Y8 and B. longum Y10 used in a pharmaceutical probiotic product (VSL-3). PCR and real-time PCR techniques with the selected primers were employed for the direct enumeration of the bifidobacteria in the probiotic preparation and for studying their kinetic characteristics in batch cultures. These analysis revealed that B. infantis Y1 was the predominant strain in the probiotic product and that its growth rate was the highest. Since B. infantis Y1, B. breve Y8 and B. longum Y10 are co-cultured during the industrial production of VSL-3, the kinetic characteristics of these strains can explain their different concentrations in the probiotic preparation. A validation of the PCR quantification method was performed by identifying a representative number of isolates from the bacterial mixtures with automated ribotyping. The methodology described represents a useful tool for the specific quantitative detection of bacterial strains and species in complex mixtures such as pharmaceutical preparations, dairy starter cultures, faecal samples and biopsies. 相似文献
6.
Rodrigues RC Felipe MG Roberto IC Vitolo M 《Bioprocess and biosystems engineering》2003,26(2):103-107
Batch fermentation of sugarcane bagasse hemicellulosic hydrolyzate by the yeast Candida guilliermondii FTI 20037 was performed using controlled pH values (3.5, 5.5, 7.5). The maximum values of xylitol volumetric productivity (Q
p=0.76 g/l h) and xylose volumetric consumption (Q
s=1.19 g/l h) were attained at pH 5.5. At pH 3.5 and 7.5 the Q
p value decreased by 66 and 72%, respectively. Independently of the pH value, Y
x/s decreased with the increase in Y
p/s suggesting that the xylitol bioconversion improves when the cellular growth is limited. At the highest pH value (7.5), the maximum specific xylitol production value was the lowest (q
pmax=0.085 g/l h.), indicating that the xylose metabolism of the yeast was diverted from xylitol formation to cell growth.List of symbols
P
max
xylitol concentration (g/l)
-
Q
x
volumetric cell production rate (g/l h)
-
Q
s
volumetric xylose uptake rate (g/l h)
-
Q
p
volumetric xylitol production rate (g/l h)
-
q
pmax
specific xylitol production (g/g h)
-
q
smax
specific xylose uptake rate (g/g h)
-
max
specific cell growth rate (h–1)
-
Y
p/s
xylitol yield coefficient, g xylitol per g xylose consumed (g/g)
-
Y
p/x
xylitol yield coefficient, g xylitol per g dry cell mass produced (g/g)
-
Y
x/s
cell yield coefficient, g dry cell mass per g xylose consumed (g/g)
-
cell
percentage of the cell yield from the theoretical value (%)
-
xylitol
percentage of xylitol yield from the theoretical value (%) 相似文献
7.
Jos Moreno M. Angeles Vargas Hctor Olivares Joaquín Rivas Miguel G. Guerrero 《Journal of biotechnology》1998,60(3):2139-182
The halotolerant, filamentous, heterocystous cyanobacterium Anabaena sp. ATCC 33047 released, during the stationary growth phase in batch culture and, at low dilution rate, in continuous culture, large amounts of an exopolysaccharide (EPS) to the culture medium. Different environmental, nutritional and physical parameters affected production and accumulation of the EPS. The presence of either a combined nitrogen source or NaCl at high concentration led to decreased EPS production, without affecting cell growth. In contrast, generation of the EPS was markedly enhanced in response to an increase in either air flow rate, temperature or irradiance. In continuous culture, accumulation of EPS in the medium increased in response to a decrease in the dilution rate, with maximal EPS productivity being reached at a dilution rate of 0.03 h−1. 相似文献
8.
Whole‐cell biotransformation of oleanolic acid by free and immobilized cells of Nocardia iowensis: Characterization of new metabolites
下载免费PDF全文
![点击此处可从《Engineering in Life Science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Benjamin Ludwig Doris Geib Christiane Haas Juliane Steingroewer Thomas Bley Kai Muffler Roland Ulber 《Engineering in Life Science》2015,15(1):108-115
In this study, Nocardia iowensis was used to transform oleanolic acid (OA) into oleanane derivatives. The first derivative, which was found after 24 h of cultivation, was the known and already described OA methyl ester. After 1 week, two other derivatives (oleanonic acid methyl ester and an unknown metabolite) were identified as new products of a biotransformation by N. iowensis. These oleanane metabolites were characterized by HPLC, HPLC‐ESI‐MS, and HPLC‐1H NMR spectroscopy. The biotransformation was performed by suspended and immobilized cells (ICs) of N. iowensis. Cells immobilized in alginate beads were used in order to prepare a continuous process. The substrate uptake of free and ICs was similar, whereas the peak area of OA methyl ester of the ICs was only about 10% of the native cells. However, the final product (oleanonic acid methyl ester) concentrations were similar in both approaches, whereas the unknown metabolite 3 was only detected transiently in the medium of ICs. Based on these results, a new biosynthetic pathway for the biotechnological production of oleanonic acid methyl ester is proposed. 相似文献
9.
Predictions of matrix‐assisted refolding of α‐lactalbumin: Process efficiency versus batch dilution method
下载免费PDF全文
![点击此处可从《Engineering in Life Science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Protein refolding is an important technique to produce active recombinant proteins from inclusion bodies. Because of the complexity of the refolding process, a trial‐and‐error method is usually used for its design, which is ineffective and time consuming. Therefore, an efficient method for the process prediction is indispensable to optimize the operating conditions. In this article, we suggest a design procedure for matrix‐assisted protein refolding. Three different chromatographic techniques were considered exploiting hydrophobic interaction chromatography, ion‐exchange chromatography, and SEC media. The procedure consisted of quantification of refolding kinetics, analysis of the retention behavior of all protein forms involved in refolding, construction of a dynamic model, and the process simulation. Denatured bovine α‐lactalbumin was used as model protein. The refolding rate was measured for different protein concentration using the batch dilution method. A kinetic scheme for the protein refolding was suggested and incorporated into a dynamic model of chromatographic column and used for predicting the refolding performance. The productivity, yield, and buffer consumption were used as performance indicators for the refolding techniques considered. The matrix‐assisted protein refolding process outperformed batch dilution method with respect to all indicators provided that efficient method for the process design was used. 相似文献
10.
It has been shown that, by adding a chaotic sequence to the weight update during the training of neural networks, the chaos injection-based gradient method (CIBGM) is superior to the standard backpropagation algorithm. This paper presents the theoretical convergence analysis of CIBGM for training feedforward neural networks. We consider both the case of batch learning as well as the case of online learning. Under mild conditions, we prove the weak convergence, i.e., the training error tends to a constant and the gradient of the error function tends to zero. Moreover, the strong convergence of CIBGM is also obtained with the help of an extra condition. The theoretical results are substantiated by a simulation example. 相似文献