全文获取类型
收费全文 | 335篇 |
免费 | 18篇 |
出版年
2021年 | 1篇 |
2019年 | 1篇 |
2018年 | 5篇 |
2017年 | 2篇 |
2016年 | 8篇 |
2015年 | 14篇 |
2014年 | 16篇 |
2013年 | 24篇 |
2012年 | 16篇 |
2011年 | 14篇 |
2010年 | 26篇 |
2009年 | 24篇 |
2008年 | 15篇 |
2007年 | 13篇 |
2006年 | 11篇 |
2005年 | 15篇 |
2004年 | 12篇 |
2003年 | 4篇 |
2002年 | 6篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1998年 | 9篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 9篇 |
1991年 | 3篇 |
1989年 | 2篇 |
1988年 | 8篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 16篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有353条查询结果,搜索用时 687 毫秒
1.
2.
3.
4.
The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from
nucleotide sequence variation across a 765-bp region in the cytochrome
oxidase I and II genes of the mitochondrial genome. Most parsimonious
relationships of 25 haplotypes from 16 Greya species and two outgroup
genera (Tetragma and Prodoxus) showed substantial congruence with the
species relationships indicated by morphological variation. Differences
between mitochondrial and morphological trees were found primarily in the
positions of two species, G. variabilis and G. pectinifera, and in the
branching order of the three major species groups in the genus. Conflicts
between the data sets were examined by comparing levels of homoplasy in
characters supporting alternative hypotheses. The phylogeny of Greya
species suggests that host-plant association at the family level and larval
feeding mode are conservative characters. Transition/transversion ratios
estimated by reconstruction of nucleotide substitutions on the phylogeny
had a range of 2.0-9.3, when different subsets of the phylogeny were used.
The decline of this ratio with the increase in maximum sequence divergence
among taxa indicates that transitions are masked by transversions along
deeper internodes or long branches of the phylogeny. Among transitions,
substitutions of A-->G and T-->C outnumbered their reciprocal
substitutions by 2-6 times, presumably because of the approximately 4:1
(77%) A+T-bias in nucleotide base composition. Of all transversions,
73%-80% were A<-->T substitutions, 85% of which occurred at third
positions of codons; these estimates did not decrease with an increase in
maximum sequence divergence of taxa included in the analysis. The high
frequency of A<-->T substitutions is either a reflection or an
explanation of the 92% A+T bias at third codon positions.
相似文献
5.
6.
C. Born M. Biselli C. Wandrey J. Thömmes M. -R. Kula 《Bioprocess and biosystems engineering》1996,15(1):21-29
Continuous culture may be an efficient way of producing proteins which are susceptible to secondary processing in the course of a fermentation process. Short residence times in these systems support the production of correctly assembled proteins by avoiding substrate limitations and product inhibitions and also minimize the contact of sensitive bioproducts with degrading enzymes. Thus products of increased stability and integrity are obtained from continuous processes. The downstream process following continuous culture has to be adapted to the specific conditions of continuous fermentations, e.g. large liquid volumes and diluted process solutions. In this paper an approach is shown how a fluidized bed adsorption as first recovery operation may be coupled directly to a continuous production. Immobilized hybridoma cells are cultivated in porous glass microcarriers in a continuous fluidized bed process, the cell containing harvest is purified by fluidized bed adsorption using an agarose based cation exchange matrix. By this coupled mode of operation the large biomass containing harvest volume resulting from the continuous cultivation may be applied directly to a fluidized chromatographic matrix without prior clarification, leading to a particle free and initially purified product solution of reduced volume. In an experimental setup a bench-scale fluidized bed bioreactor of 25 ml carrier volume was coupled to a fluidized bed adsorption column operated with 300 ml of adsorbent. This configuration yielded up to 20 mg of monoclonal antibody per day in a cell free solution at fourfold concentration and fivefold purification. The process was run for more than three weeks with consistent product output.The help of H. Schmitz, A. Bader, J. Gätgens and M. Halfar during the experiments is gratefully acknowledged. This work was partially funded by the ministry of science and research of the Federal Republic of Germany within the project Stoffumwandlung mit Biokatalysatoren. 相似文献
7.
van der Pol JJ Machnik M Biselli M Portela-Klein T de Gooijer CD Tramper J Wandrey C 《Cytotechnology》1997,24(1):19-30
The monoclonal-antibody production of an immobilized hybridoma cell line cultivated in a fluidized-bed reactor was monitored
on-line for nearly 900 h. The monoclonal antibody concentration was determined by an immuno affinity-chromatography method
(ABICAP). Antibodies directed against the product, e.g. IgG, were immobilized on a micro-porous gel and packed in small columns.
After all IgG present in the sample was bound to the immobilized antibodies, unbound proteins were removed by rinsing the
column. Elution of the bound antibodies followed and the antibodies were determined by fluorescence. The analytical procedure
was automated with a robotic device to enable on-line measurements. The correlation between the on-line determined data and
antibody concentrations measured by HPLC was linear.
A sampling system was constructed, which was based on a pneumatically actuated in-line membrane valve integrated into the
circulation loop of the reactor. Separation of the cells from the sample stream was achieved by a depth filter made of glass-fibre,
situated outside the reactor. Rapid obstruction of the filter by cells or cell debris and contamination of the sample system
was avoided by intermittent rinsing of the sample system with a chemical solution. The intermittent rinsing of the filter,
which had a surface of 4.8 cm2, resulted in an operational capacity of up to 40 samples (1.0 l total sample volume). Both the sampling system and the analytical
device functioned without failure during this long-term culture.
The culture temperature was varied between 34 and 40 °C. Raising the temperature from 34 up to 37 °C resulted in a simultaneous
increase of growth and specific antibody production rate. Specific metabolic rates of glucose, lactate, glutamine and ammonium
stayed constant in this temperature range. A further enhancement of temperature up to 40 °C had a negative effect on the growth
rate, whereas the specific monoclonal antibody production rate showed a small increase. The other specific metabolic rates
also increased in the temperature range between 38 to 40 °C.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
9.
10.