全文获取类型
收费全文 | 3229篇 |
免费 | 170篇 |
国内免费 | 3篇 |
专业分类
3402篇 |
出版年
2022年 | 23篇 |
2021年 | 19篇 |
2020年 | 19篇 |
2019年 | 24篇 |
2018年 | 26篇 |
2017年 | 25篇 |
2016年 | 43篇 |
2015年 | 71篇 |
2014年 | 81篇 |
2013年 | 218篇 |
2012年 | 152篇 |
2011年 | 172篇 |
2010年 | 78篇 |
2009年 | 88篇 |
2008年 | 140篇 |
2007年 | 147篇 |
2006年 | 173篇 |
2005年 | 144篇 |
2004年 | 139篇 |
2003年 | 176篇 |
2002年 | 159篇 |
2001年 | 98篇 |
2000年 | 104篇 |
1999年 | 85篇 |
1998年 | 60篇 |
1997年 | 53篇 |
1996年 | 41篇 |
1995年 | 48篇 |
1994年 | 36篇 |
1993年 | 32篇 |
1992年 | 54篇 |
1991年 | 62篇 |
1990年 | 48篇 |
1989年 | 49篇 |
1988年 | 41篇 |
1987年 | 35篇 |
1986年 | 36篇 |
1985年 | 36篇 |
1984年 | 29篇 |
1983年 | 29篇 |
1982年 | 23篇 |
1981年 | 32篇 |
1980年 | 28篇 |
1979年 | 24篇 |
1978年 | 25篇 |
1977年 | 16篇 |
1976年 | 24篇 |
1975年 | 20篇 |
1974年 | 18篇 |
1968年 | 16篇 |
排序方式: 共有3402条查询结果,搜索用时 15 毫秒
161.
Hideo Katagiri Kazutami Imai Katsumi Ito 《Bioscience, biotechnology, and biochemistry》2013,77(6):575-594
Resting cells of l. fermentum convert glyceraldehyde to equimolar lactic acid and neither the evolution of carbon dioxide nor the uptake of oxygen was observed. Glyceraldehyde-3-phosphate and 3-phosphoglycerate were identified as intermediates which were equally labeled with inorganic P32 in reaction systems, and the presence of triokinase was suggested. 相似文献
162.
Katsumi Shibata 《Bioscience, biotechnology, and biochemistry》2013,77(7):1739-1744
This experiment was performed to investigate the possibility that N′ -methylnicotinamide (N′-methyl-3-pyridinecarboxamide) and nicotinamide N-oxide have niacin activity or not in animals. When 20 mg N′-methylnicotinamide per mouse was administered, urinary excretion of nicotinamide, N1-methylnicotinamide (MNA), N1-methyl-2-pyridone-5-carboxamide (2-Py), and N1-methyl-4-pyridone-3-carboxamide (4-Py) increased 24-, 3-, 3-, and 3-fold, respectively, compared with the control values. The increased ratios of MNA, 2-Py, and 4-Py were almost the same as those when 20 mg nicotinamide was administered. Therefore, the relative activity of N′-methylnicotinamide to nicotinamide as niacin was considered to be about 1. When 20 mg nicotinamide N-oxide per mouse was administered, urinary excretion of nicotinamide, MNA, 2-Py, and 4-Py increased 6.4-, 1.8-, 1.6-, and 1.7-fold, respectively, compared with the control values. The increased ratios of MNA, 2-Py, and 4-Py were about 1/2 of those when 20 mg nicotinamide was administered, so the relative activity of nicotinamide N-oxide to nicotinamide as niacin is considered to be about 1/2. In conclusion, it was found the possibility that the reactions N′-methylnicotinamide → nicotinamide and nicotinamide N-oxide → nicotinamide occur, at least in mice, and that therefore N′-methylnicotinamide and nicotinamide N-oxide have niacin activity. 相似文献
163.
Kouichi Miyata Katsumi Tomoda Masao Isono 《Bioscience, biotechnology, and biochemistry》2013,77(10):1457-1462
The substrate specificity of Serratia protease was determined using various synthetic substrates. The enzyme did not participate in the hydrolysis of di- and tri-peptides except benzoylglycylleucinamide which was split at a limited rate into hippuric acid and leucinamide. The enzyme action on larger peptides was also studied. The enzyme cleaved the gly-leu bond in eledoisin related peptide and the gly-phe bond in bradykinin. The enzyme split oxidized insulin B-chain at twelve different peptide bonds. 相似文献
164.
165.
Kouichi Miyata Katsumi Tomoda Masao Isono 《Bioscience, biotechnology, and biochemistry》2013,77(4):460-467
Protease from a strain of Serratia contained one gram atom of zinc ion per mole and the zinc ion was essential for the activity. Also zinc-free apoenzyme was isolated as a crystalline form from the native-enzyme. Several metalloenzymes were prepared by the addition of corresponding metal ions to the apoenzyme. Studies on activities toward the hydrolysis of casein showed that relative activities of native- (zinc), cobalt- and manganese-enzyme were 1.0, 1.2 and 0.8, respectively. Toward the hydrolysis of hippurylleucinamide, however, specific activity of cobalt-enzyme was about 10 times that of the native- (zinc-) enzyme. Spectroscopic studies did not reveal any significant differences in conformations among native-enzyme, apoenzyme and the other metalloenzymes. 相似文献
166.
167.
168.
169.
A wood-destroying fungus, Trametes sanguinea, produced a potent acid protease in a submerged culture. Maximum proteolytic activity of the culture was attained after 140-hours cultivation in a medium containing dextrin and corn steep liquor. The acid protease was obtained in crystalline form from the mycelium-free culture filtrate by the following successive treatments: acetone precipitation, ionexchange column chromatography, ammonium sulfate fractionation, dialysis, and crystallization by acetone. Throughout the over-all process, the acid protease was purified approximately 30-fold with about 8% recovery of the original activity. 相似文献
170.
Takeshi Hashizume Kaoru Kawakita Shunji Senda Tamizi Sugiyama 《Bioscience, biotechnology, and biochemistry》2013,77(12):3481-3484
Endogenous cytokinins in alfalfa were isolated, and identified by mass spectrometry, trans- Ribosylzeatin (RZ) and ribosyldihydrozeatin (DHRZ) were identified from the root, and the combined content (benzyladenine equivalent) was estimated to be approximately 0.5/μg/100 g of fresh weight, eis- and trans-KL were identified from the stems and leaves. The relative content of the m-isomer was approximately five times greater than that of the trans-isomer. 相似文献