全文获取类型
收费全文 | 547727篇 |
免费 | 46886篇 |
国内免费 | 1134篇 |
出版年
2018年 | 15253篇 |
2017年 | 13921篇 |
2016年 | 12498篇 |
2015年 | 8040篇 |
2014年 | 8993篇 |
2013年 | 12992篇 |
2012年 | 18051篇 |
2011年 | 26417篇 |
2010年 | 20843篇 |
2009年 | 16205篇 |
2008年 | 21816篇 |
2007年 | 23860篇 |
2006年 | 12872篇 |
2005年 | 12495篇 |
2004年 | 12950篇 |
2003年 | 12609篇 |
2002年 | 12160篇 |
2001年 | 18690篇 |
2000年 | 18674篇 |
1999年 | 14985篇 |
1998年 | 5367篇 |
1997年 | 5598篇 |
1996年 | 5284篇 |
1995年 | 5004篇 |
1994年 | 4908篇 |
1993年 | 4900篇 |
1992年 | 12818篇 |
1991年 | 12668篇 |
1990年 | 12626篇 |
1989年 | 12368篇 |
1988年 | 11647篇 |
1987年 | 10917篇 |
1986年 | 10219篇 |
1985年 | 10611篇 |
1984年 | 8776篇 |
1983年 | 7611篇 |
1982年 | 5892篇 |
1981年 | 5314篇 |
1980年 | 4896篇 |
1979年 | 8434篇 |
1978年 | 6561篇 |
1977年 | 6162篇 |
1976年 | 5860篇 |
1975年 | 6407篇 |
1974年 | 6959篇 |
1973年 | 6810篇 |
1972年 | 6623篇 |
1971年 | 6031篇 |
1970年 | 4960篇 |
1969年 | 4982篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
991.
992.
993.
Ya. O. Loginov G. G. Khudaigulov S. P. Chetverikov A. I. Melent’ev O. N. Loginov 《Applied Biochemistry and Microbiology》2011,47(3):311-314
Highly viscous polysaccharide (250–350 kDa) of an alginate nature with a predominance of α-L-guluronic acid (M/G = 0.22) was
obtained from Azotobacter vinelandi. The yield of polysaccharide was 20.5 ± 0.5 g/l when cultured in a medium containing molasses at a viscosity of the cultural
liquid of over 30000 cSt. The biopolymer is stable at pH 4.0–9.0 in a wide temperature range and well soluble in highly mineralized
water; it retains a high viscosity level and can be used in the petroleum industry for enhanced oil recovery. 相似文献
994.
995.
996.
Energy metabolism and lipid peroxidation of human erythrocytes as a function of increased oxidative stress. 总被引:5,自引:0,他引:5
B Tavazzi D Di Pierro A M Amorini G Fazzina M Tuttobene B Giardina G Lazzarino 《European journal of biochemistry》2000,267(3):684-689
To study the influence of oxidative stress on energy metabolism and lipid peroxidation in erythrocytes, cells were incubated with increasing concentrations (0.5-10 mM) of hydrogen peroxide for 1 h at 37 degrees C and the main substances of energy metabolism (ATP, AMP, GTP and IMP) and one index of lipid peroxidation (malondialdehyde) were determined by HPLC on cell extracts. Using the same incubation conditions, the activity of AMP-deaminase was also determined. Under nonhaemolysing conditions (at up to 4 mM H2O2), oxidative stress produced, starting from 1 mM H2O2, progressive ATP depletion and a net decrease in the intracellular sum of adenine nucleotides (ATP + ADP + AMP), which were not paralleled by AMP formation. Concomitantly, the IMP level increased by up to 20-fold with respect to the value determined in control erythrocytes, when cells were challenged with the highest nonhaemolysing H2O2 concentration (4 mM). Efflux of inosine, hypoxanthine, xanthine and uric acid towards the extracellular medium was observed. The metabolic imbalance of erythrocytes following oxidative stress was due to a dramatic and unexpected activation of AMP-deaminase (a twofold increase of activity with respect to controls) that was already evident at the lowest dose of H2O2 used; this enzymatic activity increased with increasing H2O2 in the medium, and reached its maximum at 4 mM H2O2-treated erythrocytes (10-fold higher activity than controls). Generation of malondialdehyde was strictly related to the dose of H2O2, being detectable at the lowest H2O2 concentration and increasing without appreciable haemolysis up to 4 mM H2O2. Besides demonstrating a close relationship between lipid peroxidation and haemolysis, these data suggest that glycolytic enzymes are moderately affected by oxygen radical action and strongly indicate, in the change of AMP-deaminase activity, a highly sensitive enzymatic site responsible for a profound modification of erythrocyte energy metabolism during oxidative stress. 相似文献
997.
998.
999.
1000.