全文获取类型
收费全文 | 3709篇 |
免费 | 275篇 |
国内免费 | 583篇 |
出版年
2023年 | 53篇 |
2022年 | 111篇 |
2021年 | 104篇 |
2020年 | 132篇 |
2019年 | 126篇 |
2018年 | 105篇 |
2017年 | 133篇 |
2016年 | 143篇 |
2015年 | 115篇 |
2014年 | 152篇 |
2013年 | 337篇 |
2012年 | 141篇 |
2011年 | 235篇 |
2010年 | 159篇 |
2009年 | 282篇 |
2008年 | 228篇 |
2007年 | 199篇 |
2006年 | 180篇 |
2005年 | 175篇 |
2004年 | 162篇 |
2003年 | 158篇 |
2002年 | 146篇 |
2001年 | 128篇 |
2000年 | 101篇 |
1999年 | 89篇 |
1998年 | 79篇 |
1997年 | 58篇 |
1996年 | 52篇 |
1995年 | 77篇 |
1994年 | 77篇 |
1993年 | 50篇 |
1992年 | 58篇 |
1991年 | 59篇 |
1990年 | 19篇 |
1989年 | 14篇 |
1988年 | 9篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 32篇 |
1984年 | 25篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有4567条查询结果,搜索用时 15 毫秒
71.
S. Schaepe A. Kuprijanov C. Sieblist M. Jenzsch R. Simutis A. Lübbert 《Journal of biotechnology》2013
By means of improved feedback control kLa measurements become possible at a precision and reproducibility that now allow a closer look at the influences of power input and aeration rate on the oxygen mass transfer. These measurements are performed online during running fermentations without a notable impact on the biochemical conversion processes. A closer inspection of the mass transfer during cultivations showed that at least the number of impellers influences mass transfer and mixing: On the laboratory scale, two hollow blade impellers clearly showed a larger kLa than the usually employed three impeller versions when operated at the same agitation power and aeration rate. Hollow blade impellers are preferable under most operational conditions because of their perfect gas handling capacity. Mixing time studies showed that these two impeller systems are also preferable with respect to mixing. Furthermore the widths of the baffle bars depict a significant influence on the kLa. All this clearly supports the fact that it is not only the integral power density that finally determines kLa. 相似文献
72.
The cDNA encoding a putative xylose reductase (xyrA) from Aspergillus oryzae was cloned and coexpressed in the yeast Saccharomyces cerevisiae with A. oryzae xylitol dehydrogenase cDNA (xdhA). XyrA exhibited NADPH-dependent xylose reductase activity. The S. cerevisiae strain, overexpressing the xyrA, xdhA, endogenous XKS1, and TAL1 genes, grew on xylose as sole carbon source, and produced ethanol. 相似文献
73.
The Effect of Cocoa and Polydextrose on Bacterial Fermentation in Gastrointestinal Tract Simulations
《Bioscience, biotechnology, and biochemistry》2013,77(8):1834-1843
Effects of cocoa mass and supplemented dietary fiber (polydextrose) on microbial fermentation were studied by combining digestion simulations of stomach and small intestine with multi-staged colon simulations. During the four phases of digestion, concentrations of available soluble proteins and reducing sugars reflected in vivo absorption of nutrients in small intestine. In colon simulation vessels, addition of polydextrose to digested cocoa mass significantly increased concentrations of total short-chain fatty acids and butyric acid, from 103 to 468 mM (P<0.01) and from 12 to 22 mM (P<0.01), respectively. Long-chain fatty acid concentrations (decreasing from 1,222 to 240 mM) were mainly affected by the presence of digested cocoa mass. Cocoa mass with or without polydextrose addition significantly decreased production of cadaverine (P<0.02) and branched-chain fatty acids compared to control during colon simulations. Results indicate beneficial effects on metabolism of colonic microbiota after digestion of cocoa mass, and even more so with polydextrose addition. 相似文献
74.
《Bioscience, biotechnology, and biochemistry》2013,77(5):912-917
It is believed that high concentrations of sodium chloride (NaCl) suppress the biosynthesis of exopolysaccharide (EPS) in lactic acid bacteria (LAB). Nevertheless, overproduction of EPSs due to high salinity stress in solid state fermentation performed on an agar surface was demonstrated in this study using a response surface methodology via a central composite design (CCD). Under optimized conditions with NaCl 4.97% and sucrose 136.5 g/L at 40.79 h of incubation, the EPS yield was 259% (86.36 g/L of EPS), higher than the maximum yield produced with the modified MRS medium containing only 120 g/L of sucrose without NaCl (33.4 g/L of EPS). Biosynthesis of EPS by Lactobacillus confusus TISTR 1498 was independent of biomass production. Our results indicated that high salinity stress can enhance EPS production in solid state fermentation. 相似文献
75.
《Bioscience, biotechnology, and biochemistry》2013,77(12):2800-2802
γ-Glutamylmethylamide synthetase and dried baker’s yeast cells were enclosed together in a dialysis membrane tube to produce theanine repeatedly by coupled fermentation with energy transfer. The membrane-enclosed enzyme preparation (M-EEP) formed approximately 600 mM theanine from glutamic acid and ethylamine at a 100% conversion rate. M-EEP maintained its productivity of theanine during six consecutive reactions in a mixture containing NAD+. 相似文献
76.
Eiki Nagano Takayuki Oritani Kyohei Yamashita 《Bioscience, biotechnology, and biochemistry》2013,77(9):2095-2098
Methyl 6′, 6′-didemethyl abscisate (5) was synthesized and assayed to elucidate the physiological activity of methyl substituents on the cyclohexene ring of abscisic acid (ABA). During this study two new chiral stereoisomeric analogs 6 and 7 were synthesized from l-and d-carvone. The rice seedling assay and germination assay of garden radish showed that 6′-methyl groups of ABA were not important in biological activity and that 5′-isopropenyl analogs 6 and 7 were inactive. 相似文献
77.
《Bioscience, biotechnology, and biochemistry》2013,77(4):642-647
The growth inhibition by nisin-producing lactococci against Bacillus subtilis and its application to soybean miso fermentation were investigated. Lactococcus lactis subsp. lactis IFO12007 (nisin-producing, salt-intolerant) rapidly proliferated to more than 109 cells/g in cooked soybeans without any excessive pH decrease. In spite of the mild decrease in pH, the growth of B. subtilis was completely inhibited; no living cells were detected in a soybean sample inoculated with 106 cells/g and incubated for 24 to 72 h. This Lc. lactis was applied to soybean miso fermentation as a starter culture. It produced high nisin activity (1.28×105 AU/g) in cooked soybean, resulting in the complete growth inhibition of B. subtilis, which had been inoculated at the beginning of the koji fermentation, throughout the process of miso production. Over-acidification, which is undesirable for miso quality, was successfully prevented simply by adding salt which killed the salt-intolerant Lc. lactis. Furthermore, the nisin activity in miso disappeared with aging. 相似文献
78.
Shuwsei Kamimiya Yoshifumi Itoh Kazuo Izaki Hajime Takahashi 《Bioscience, biotechnology, and biochemistry》2013,77(6):975-981
A strain of Erwinia aroideae produced an extracellular pectolytic enzyme under growth conditions with pectin or pectic acid as the inducer. This strain also produced a pectin lyase when nalidixic acid is added to a culture medium. The pectolytic enzyme produced under the growth conditions was purified approximately 40-fold from the culture fluid by carboxy- methyl cellulose and Sephadex G-75 gel column chromatographies. The purified enzyme was almost homogeneous on sodium dodecyl sulfate polyacrylamide gel electrophoresis, having a molecular weight of about 36,000 to 38,000. This enzyme, with optimal activity at pH 9.0 to 9.2, produced reaction products which had a strong absorption at 230 nm indicating a lyase type of the reaction. The enzyme activity was markedly stimulated by calcium ion and completely inhibited by cobalt and mercuric ions and by ethylenediaminetetraacetate. Pectic acid or pectin with lower methoxyl content was a good substrate for this enzyme, while no significant activity was observed when pectin with higher methoxyl content was used as a substrate. It was concluded that the enzyme produced under the normal growth conditions is an endo-pectate lyase and differs from the pectin lyase induced by nalidixic acid. 相似文献
79.
Seongho Jang Eu Ddeum Park Hyung Joo Suh Sang Hun Lee Jin Soo Kim 《Bioscience, biotechnology, and biochemistry》2013,77(10):1716-1722
To investigate the activity of fermented deer antler on exercise endurance capacity, we evaluated endurance capacity in five-week-old male BALB/c mice by administering the fermented deer antler extract (FA) or the non-fermented deer antler extract (NFA) and then subjected the mice to exercise in the form of swimming. The mice administered 500?mg/kg/day of FA showed a significant increase in swimming time compared with mice administered placebo (16.55?min vs. 21.64?min, P?<?0.05). Serum lactate dehydrogenase (LDH), the marker of the liver and muscle damage, was significantly lower in FA groups. However, NFA groups did not show significantly different swimming time or serum LDH from that of the control group. Moreover, the FA-500 group had significantly higher hepatic superoxide dismutase (SOD) activity after forced swimming than the control and NFA groups (P?<?0.05). These findings suggest that fermentation may increase the exercise endurance capacity of the deer antler. 相似文献
80.
Takeshi Sugai Shigefumi Kuwahara Chimaki Hoshino Noritada Matsuo Kenji Mori 《Bioscience, biotechnology, and biochemistry》2013,77(10):2579-2585
Asymmetric hydrolysis of the acetates of racemic secondary alcohols related to synthetic pyrethroids by Bacillus subtilis var. niger (IFO 3108) yielded optically active acetates and alcohols of varying optical purities. 相似文献