全文获取类型
收费全文 | 2425篇 |
免费 | 119篇 |
国内免费 | 1篇 |
出版年
2022年 | 9篇 |
2021年 | 18篇 |
2020年 | 10篇 |
2019年 | 23篇 |
2018年 | 24篇 |
2017年 | 19篇 |
2016年 | 37篇 |
2015年 | 59篇 |
2014年 | 78篇 |
2013年 | 198篇 |
2012年 | 146篇 |
2011年 | 162篇 |
2010年 | 111篇 |
2009年 | 104篇 |
2008年 | 173篇 |
2007年 | 149篇 |
2006年 | 139篇 |
2005年 | 146篇 |
2004年 | 134篇 |
2003年 | 147篇 |
2002年 | 135篇 |
2001年 | 30篇 |
2000年 | 24篇 |
1999年 | 35篇 |
1998年 | 36篇 |
1997年 | 40篇 |
1996年 | 31篇 |
1995年 | 25篇 |
1994年 | 17篇 |
1993年 | 31篇 |
1992年 | 25篇 |
1991年 | 24篇 |
1990年 | 9篇 |
1989年 | 15篇 |
1988年 | 7篇 |
1987年 | 16篇 |
1986年 | 9篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 21篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1980年 | 13篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1970年 | 6篇 |
排序方式: 共有2545条查询结果,搜索用时 406 毫秒
81.
Tsutomu Ishikawa Tetsuya Tosa Ichiro Chibata 《Bioscience, biotechnology, and biochemistry》2013,77(3):193-198
Since Achromobacter pestifer EA isolated from soils shows markedly high ?-Iysine acylase activity compared with those of the other microorganisms ever tested, cultural conditions for the production of this enzyme were investigated.As a result, it was confirmed that simple medium containing 1% peptone, 5% glucose and some inorganic salts is most suitable for the enzyme production and that much more ?-Iysine acylase is produced by shaken culture or submerged culture in jar fermentor than by stationary culture. α-Amino acylase activity in this organism was also studied. 相似文献
82.
Tsutomu Masuda Kunio Yamane Hideo Hirokawa Teruo Tanaka Kenji Sakaguchi Bunji Maruo 《Bioscience, biotechnology, and biochemistry》2013,77(4):947-948
Five bufadienolides (1-5) isolated from the leaves of Kalanchoe pinnata and K. daigremontiana×tubiflora (Crassulaceae) were examined for their inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation in Raji cells induced by the tumor promoter, 12-O-tetradecanoylphorbol-13-acetate. All bufadienolides showed inhibitory activity, and bryophyllin A (1) exhibited the most marked inhibition (IC50=0.4 μM) among the tested compounds. Bryophyllin C (2), a reduction analogue of 1, and bersaldegenin-3-acetate (3) lacking the orthoacetate moiety were less active. These results strongly suggest that bufadienolides are potential cancer chemopreventive agents. 相似文献
83.
Selection of High Ubiquinone 10-Producing Strain of Tobacco Cultured Cells by Cell Cloning Technique
Takashi Matsumoto Tsutomu Ikeda Naomi Kanno Takuro Kisaki Masao Noguchi 《Bioscience, biotechnology, and biochemistry》2013,77(4):967-969
A novel enzyme, which was named Nα-benzyloxycarbonyl amino acid urethane hydrolase, was purified from a cell-free extract of Streptococcus faecalis R ATCC 8043, using Nα-benzyloxycarbonyl glycine as substrate. The enzyme was purified 1300-fold with an activity yield of 8%. The purified enzyme was homogeneous by disc electrophoresis. The molecular weight of the native enzyme is about 220,000 by gel filtration, and a molecular weight of 32,000 was determined for the reduced and denatured enzyme by gel electrophoresis in sodium dodecyl sulfate. The isoelectric point was 4.48. The enzyme was inhibited by p-chloromercuribenzoate. The presence of divalent cations (i.e., Co2+ or Zn2+) is essential for its activity. 相似文献
84.
Kazuo Iwai Masahiro Kohashi Tsutomu Itadani Tetsuya Suzuki 《Bioscience, biotechnology, and biochemistry》2013,77(5):1141-1147
Guanosine triphosphate cyclohydrolase (EC 3.5.4.16) was previously shown to exist in two forms (GTP cyclohydrolase D-I and D-II) in Serratia indica IFO 3759, and they were homogeneously isolated. The present study deals with the characterization of their reaction products. A fluorescent product formed from guanosine triphosphate by GTP cyclohydrolase D-II was identified as 7,8-dihydroneopterin triphosphate by its absorption spectra, phosphate analysis and gas chromatography-mass spectrometry of the dephosphorylated trimethylsilyl derivative. After oxidation and dephosphorylation, the d-erythro configuration of the side chain was made clear by the elution profile on ECTEOLA-cellulose chromatography, Rf values on thin-layer chromatography and by biological activity to Crithidia fasciculata ATCC 12857. The fluorescent products from GTP cyclohydrolase D-I and D-II were indistinguishable. 相似文献
85.
Tsutomu Nagaya Noriko Okamoto Kousaku Murata Akira Kimura 《Bioscience, biotechnology, and biochemistry》2013,77(9):2393-2394
The effects of the injection of a large amount of N1 -methylnicotinamide (MNA) (500 mg per kg body weight) on the ratio of N1 -methyl-4-pyridone-3-carboxamide (4-py) to N1 -methyl-2-pyridone-5- carboxamide (2-py) excretion, and the activities of 2-py and 4-py forming MNA oxidases were investigated in rats. The injected MN A was excreted very rapidly into the urine; 46 % of the dose was excreted from 0~3hr post-injection, 15% from 3~6hr, 6% from 6~9hr and 1.5% from 9~ 12hr. The ratio of 4-py to 2-py also decreased rapidly; the ratio being about 0.6, 0.4, 0.4 and 0.6 from 0~3hr, 3~6hr, 6~9hr and 9~ 12hr post-injection, respectively. This ratio then recovered rapidly; being about 2, 5.5, 8.5 and 9.7 from 12~24 hr, 24 ~48 hr, 48~72 hr and 72 ~96 hr post-injection, respectively. The normal range of 4-py to 2-py excretion ratio is 8~14. So, this ratio returned to a normal level by day 3 post-injection. The rats were killed 5 hr after the MNA injection. At this time (the lowest ratio was observed around this time), the activities of 2-py and 4-py forming MNA oxidases in the injected group were 59 % and 11 % of the normal levels, respectively. Therefore, it was found that the decreased ratio of 4-py to 2-py excretion with the MNA injection was mainly due to the higher inhibition of the 4-py forming MNA oxidase than of the 2-py forming MNA oxidase by the MNA injection. 相似文献
86.
Tsutomu Yamaguchi Noriyuki Muroya Masakazu Isobe Mamoru Sugiura 《Bioscience, biotechnology, and biochemistry》2013,77(5):999-1005
Out of some 750 strains of microorganisms, a potent bacterium for lipase production was isolated from soil and was identified as Chromobacterium viscosum.The bacterium accumulates lipase in culture fluid when grown aerobically at 26°C for 3 days in a medium composed of soluble starch, soy bean meal, lard and inorganic salts.Chromobacterium lipase had an optimum pH of 7.0 for activity at 37°C, and an optimal temperature of 65°C at pH 7.0. The enzyme retained 80% of the activity when heated for 10 min at 70°C. This lipase was capable of hydrolyzing a variety of natural fats and oils, and it was more active on lard and butter than on olive oil. The activity was stimulated by Ca2+, Mg2+, Mn2+ and inhibited by Cu2+, Hg2+ and Sn2+. It was not diminished but rather stimulated by a high concentration of bile-salts. 相似文献
87.
Twelve bacterial strains which were concerned with dechlorination of 1,2,4-trichlorobenzene (TCB) were isolated from the intestinal contents of rats and it was found that they belonged to Staphylococcus epidermidis (strain A-F), Staphylococcus saprophyticus (strain G), Streptococcus sp. (strains H and I), Bacillus sp. (strain J), Gram negative rod (strain K) and Lactobacillus sp. (strain L).In Staphylococcus epidermidis (Strain A), TCB was mainly converted to o-dichlorobenzene and the latter was preferentially converted to monochlorobenzene (MCB) among dichlorobenzenes (DCBs). These conversions proceeded only under a gas phase of hydrogen. Furthermore, dry and broken cells of intact bacteria also maintained the dechlorinating activities, which were stimulated by the addition of NADPH.Therefore, it was supposed that the conversion of TCB to MCB via DCBs was reductively carried out by enzymes originating from the isolated bacteria. 相似文献
88.
Tsutomu Ikeda Takashi Matsumoto Kunio Kato Masao Noguchi 《Bioscience, biotechnology, and biochemistry》2013,77(11):2297-2298
Callus tissues were induced from stem and root segments of Rauwolfia serpentina. Growth and alkaloid production of the callus tissues were examined under various culture conditions. The growth was strikingly promoted in the presence of 2,4-D (0.5~1 ppm), kinetin (0.2~0.5 ppm) and yeast extract (0.1~0.2%). At favourable conditions, the growth value in 4 weeks’ culture was ca. 40 (F.W.), and ca. 25 (D.W.) for stem callus tissues, and ca. 15 (F.W.), and ca. 8 (D.W.) for root callus tissues. Stem and root callus tissues produced ajmaline and some other unidentified Rauwolfia alkaloids. The ajmaline content in root callus tissues was 10~20mg % and in stem callus tissues was 1~10mg %. The ajmaline production was strikingly reduced when 2,4-D concentration increased, or kinetin was omitted in the culture medium. Phytosterols including stigmasterol, β-sitosterol or cholesterol were also produced. 相似文献
89.
Tsutomu Nakayama Motohisa Kaneko Masahiko Kodama 《Bioscience, biotechnology, and biochemistry》2013,77(12):3219-3220
Thermostable purine nucleoside phosphorylases, PUN PI and PUNPII, have been purified from Bacillus stearothermophilus JTS 859. The characterization of PUNPI was reported previously. [Hori et al.9 Agric. Biol. Chem. 53, 2205 (1989)] PUNPII had a molecular weight of 113,000, consisting of 4 identical subunits (Mw 28,000). The isoelectric point was 5.3. The Michaelis constants for inosine, guanosine, and adenosine were 0.22, 0.34, and 0.075 mm, respectively. The optimal temperature of the reaction was 70°C. The enzyme was stable at 70°C. Although other reported purine nucleoside phosphorylases were SH-enzymes, PUNPII was not a SH-enzyme because the enzyme reaction was not inhibited by PCMB and iodoacetic acid, the optimal pH of the enzyme reaction was from 7.0 to 11.0, and the enzyme did not contain cysteine.PUNPII and PUNPI were different in several points. Not PUNPI but PUNPII could catalyze the phosphorolysis of adenosine. Specific activity of PUNPI and II for inosine were 405 and 50.6 μmol/min/mg protein at 60°C, respectively. PUNPI was stable at 80°C. PUNPII was stable at 70°C, but was denatured at 80°C. 相似文献
90.
Hiroto Nishijima Kouichi Nozaki Masahiro Mizuno Tsutomu Arai 《Bioscience, biotechnology, and biochemistry》2013,77(5):738-746
The xylanase (Xyn10B) that strongly adsorbs on microcrystalline cellulose was isolated from Driselase. The Xyn10B contains a Carbohydrate-binding module family 1 (CBM1) (IrpCBMXyn10B) at N-terminus. The canonical essential aromatic residues required for cellulose binding were conserved in IrpCBMXyn10B; however, its adsorption ability was markedly higher than that typically observed for the CBM1 of an endoglucanase from Trametes hirsuta (ThCBMEG1). An analysis of the CBM-GFP fusion proteins revealed that the binding capacity to cellulose (7.8 μmol/g) and distribution coefficient (2.0 L/μmol) of IrpCBMXyn10B-GFP were twofold higher than those of ThCBMEG1-GFP (3.4 μmol/g and 1.2 L/μmol, respectively), used as a reference structure. Besides the canonical aromatic residues (W24-Y50-Y51) of typical CBM1-containing proteins, IrpCBMXyn10B had an additional aromatic residue (Y52). The mutation of Y52 to Ser (IrpCBMY52S-GFP) reduced these adsorption parameters to 4.4 μmol/g and 1.5 L/μmol, which were similar to those of ThCBMEG1-GFP. These results indicate that Y52 plays a crucial role in strong cellulose binding. 相似文献