全文获取类型
收费全文 | 2464篇 |
免费 | 96篇 |
国内免费 | 2篇 |
专业分类
2562篇 |
出版年
2022年 | 9篇 |
2021年 | 14篇 |
2020年 | 7篇 |
2018年 | 22篇 |
2017年 | 12篇 |
2016年 | 37篇 |
2015年 | 49篇 |
2014年 | 55篇 |
2013年 | 192篇 |
2012年 | 125篇 |
2011年 | 109篇 |
2010年 | 68篇 |
2009年 | 67篇 |
2008年 | 122篇 |
2007年 | 134篇 |
2006年 | 159篇 |
2005年 | 144篇 |
2004年 | 152篇 |
2003年 | 167篇 |
2002年 | 150篇 |
2001年 | 44篇 |
2000年 | 34篇 |
1999年 | 30篇 |
1998年 | 36篇 |
1997年 | 35篇 |
1996年 | 18篇 |
1995年 | 27篇 |
1994年 | 31篇 |
1993年 | 32篇 |
1992年 | 33篇 |
1991年 | 32篇 |
1990年 | 43篇 |
1989年 | 26篇 |
1988年 | 21篇 |
1987年 | 18篇 |
1986年 | 24篇 |
1985年 | 15篇 |
1984年 | 25篇 |
1983年 | 27篇 |
1982年 | 32篇 |
1981年 | 26篇 |
1980年 | 24篇 |
1979年 | 18篇 |
1978年 | 18篇 |
1977年 | 21篇 |
1976年 | 9篇 |
1975年 | 10篇 |
1974年 | 8篇 |
1973年 | 10篇 |
1969年 | 8篇 |
排序方式: 共有2562条查询结果,搜索用时 0 毫秒
91.
92.
Yoshiaki Kitamura Yuki Masegi Shunsuke Ogawa Remi Nakashima Yukihiro Akao Yoshihito Ueno Yukio Kitade 《Bioorganic & medicinal chemistry》2013,21(15):4494-4501
We have developed chemically modified siRNAs and miRNAs bearing urea/thiourea-bridged aromatic compounds at their 3′-end for RNAi therapy. Chemically modified RNAs possessing urea/thiourea-bridged aromatic compounds instead of naturally occurring dinucleotides at the 3′-overhang region were easily prepared in good yields and were more resistant to nucleolytic hydrolysis than unmodified RNA. siRNAs containing urea or thiourea derivatives showed the desired knockdown effect. Furthermore, modified miR-143 duplexes carrying the urea/thiourea compounds in the 3′-end of each strand were able to inhibit the growth of human bladder cancer T24 cells. 相似文献
93.
Michio Himeno Yukio Kimura Keizo Hayashiya 《Bioscience, biotechnology, and biochemistry》2013,77(8):1457-1462
Embryos of the silkworm, Bombyx mori L., were dispersed by trypsin and the dissociated cells were cultured for infection with nuclear polyhedrosis virus (NPV) of the silkworm. The monolayer and suspension cultures were infected with NPV. RNA and DNA syntheses in the normal and NPV-infected cells were measured by incorporation of 32P into RNA and DNA fractions. RNA and DNA syntheses in the cells after infection significantly increased over those in control cells (mock infection). The effects of actinomycin D, chloramphenicol and mitomycin C on RNA and DNA syntheses in infected cells were examined. The syntheses were inhibited by the antibiotics. It was suggested that the cellular DNA synthesis was inhibited by the viral infection, because the mitomycin C-resistant DNA synthesis was found in the normal cells but not in the infected cells treated with mitomycin C. The rate of DNA synthesis induced by NPV was immediately dropped to that of control cells by addition of chloramphenicol, while the RNA synthesis induced by NPV was not affected for 6 hr after the addition of chloramphenicol. If the antibiotic did not affect the size of precursor pools, this event suggested that the RNA polymerase concerned with viral RNA synthesis was more stable than the DNA polymerase participating in the viral DNA synthesis. The viral DNA as templates for RNA and DNA syntheses was decomposed by mitomycin C. 相似文献
94.
Takashi Hamano Yukimasa Mitsuhashi Kisaku Tanaka Yukio Matsuki Yoshikiyo Oji Saburo Okamoto 《Bioscience, biotechnology, and biochemistry》2013,77(11):2427-2433
A rapid and specific method is described for the determination of nitrate in meat and fishery products.Nitrate separated from foods by extraction with 1/50Ν sodium hydroxide and ultrafiltration was readily reduced to nitrite by the use of respiratory nitrate reductase (NR) from Escherichia coli K-12. The nitrite so obtained can be determined by the specific diazotation-coupling reaction method.The use of an enzymatic reaction resulted in quantitative reduction of nitrate, and the method was relatively free of interferences. Recoveries of 10 and 100 ppm of nitrate from 5 samples of meat and fishery products ranged from 92.8 to 97.8% for 10 ppm and 97.8 to 99.4% for 100 ppm with a detection limit of 0.5 ppm. 相似文献
95.
Hisanao Takeuchi Megumi Maeda Yukio Yamaguchi Keiichiro Muramatsu 《Bioscience, biotechnology, and biochemistry》2013,77(4):931-935
Three chitinases (EC 3.2.1.14) were purified from yam, Dioscorea opposita THUMB, by fractionation with ammonium sulfate, chromatographies on DEAE-Cellulose and DEAE-Sephadex A-50, chromatofocusing and gel filtration on Bio-Gel P-60. The purified enzymes (E-l, E-2 and E-3) showed single bands on sodium dodecylsulfate polyacrylamide gel electrophoresis, and the molecular weights were estimated to be 33,500. The pIs were 4.05 (E-l), 4.0 (E-2) and 3.8 (E-3). All enzymes were glycoproteins and the neutral sugar contents were 3.6% (E-l), 3.6 (E-2) and 0.9% (E-3). The N-terminal amino acids of E-l and E-3 were the same and determined to be histidine. All enzymes hydrolyzed glycolchitin, but not p-nitrophenyl-2-acetamido-2-deoxy-β-d-glucopyranoside or Micrococcus lysodeikticus cell walls. E-l and E-3 were stable in the pH range of 5 ~ 11, and below 60°C. These enzymes showed two optimum pHs around 3.5 and 8.0 or 8.5 with glycolchitin as substrate. 相似文献
96.
Yukio Satomura Susumu Oi Akira Sawada 《Bioscience, biotechnology, and biochemistry》2013,77(3):194-200
Intracellular lipase of the fungus Sclerotina Libertiana Fcl. could be formed powerfully by washed mycelium during shaking in a plain buffer solution, just as well as in the case of shaking culture. Experiments showed revealed it to be favourable to set the mycelium in the experiment harvested at the end of its stationary phase of growth, and that the addition of various respiratory carbon sources had inhibiting effects, while several surface active agents and some enzyme preparations accelerating effects on the lipase formation. Also, the quality and the quantity of consumed cell-materials in the shaking experiment were investigated in relation to lipase formation. 相似文献
97.
An α-glucosidase and a glucoamylase have been isolated from fruit bodies of Lentinus edodes (Berk.) Sing., by a procedure including fractionation with ammonium sulfate, DEAE-cellulose column chromatography, and preparative gel electrofocusing. Both of them were homogeneous on gel electrofocusing and ultracentrifugation. The molecular weight of α-glucosidase and glucoamylase was 51,000 and 55,000, respectively. The α-glucosidase hydrolyzed maltose, maltotriose, phenyl α-maltoside, amylose, and soluble starch, but did not act on sucrose. The glucoamylase hydrolyzed maltose, maltotriose, phenyl α-maltoside, soluble starch, amylose, amylopectin, and glycogen, glucose being the sole product formed in the digests of these substrates. Both enzymes hydrolyzed phenyl a-maltoside into glucose and phenyl α-glucoside. The glucoamylase hydrolyzed soluble starch, amylose, amylopectin, and glycogen, converting them almost completely into glucose. It was found that β-glucose was liberated from amylose by the action of glucoamylase, while α-glucose was produced by the α-glucosidase.Maltotriose was the main α-glucosyltransfer product formed from maltose by the α-glucosidase. 相似文献
98.
During the investigations on riboflavin glycoside formation by Aspergillus, Mucor, Penicillium and Rhizopus, a remarkable production of 5′-d-riboflavin-α-d-glucopyranoside was observed in several strains belonging to the genus Mucor when grown on a, medium containing maltose and riboflavin. Several conditions on 5′-d-riboflavin-α-d-glucopyranoside formation were also investigated with washed mycellium of M. javanicus. Maltosyl compounds such as maltose, dextrin, amylose and soluble starch were the effective glucosyl donor, whereas glucose, fructose, sucrose, lactose and dextran were inactive. 相似文献
99.
Existence of an acetyltransferase, which catalizes acetylation of deacetylcephalosporin C to cephalosporin C, was demonstrated for the first time in cell-free extracts of Cephalosporium acremonium. The pH optimum of the enzyme appeared to be 7.0 to 7.5 and the enzyme required essentially Mg2+ as a cofactor for its reaction. The activity of this enzyme was not observed in the cell-free extracts of deacetylcephalosporin C-producing mutants Nos. 20, 29, 36 and 40, but was recovered in a revertant obtained from the mutant No. 40. These results indicate that deacetylcephalosporin C accumulation by these mutants was due to the lack of the acetyltransferase and made it reasonable that the terminal reaction of cephalosporin C biosynthesis in Cephalosporium acremonium proceeded by the catalytic action of acetyltransferase. 相似文献
100.
Three forms of α-glucosidase have been isolated from 5-day-old green gram (Phaseolus vidissimus Ten.) seedlings, by a procedure including fractionation with ammonium sulfate and polyethylene glycol 6000, DEAE-cellulose column chromatography, SP-Sephadex column chromatography, preparative gel electrofocusing and preparative disc gel electrophoresis. The α-glucosidases isolated were designated as α-glucosidase I, α-glucosidase II–1 and α-glucosidase II–2. They were homogeneous on polyacrylamide disc gel electrophoresis. Their molecular weights were 145,000, 105,000 and 65,000, respectively. The three enzymes hydrolyzed maltose, maltotriose, phenyl α-maltoside, amylose and soluble starch liberating glucose, but did not act on sucrose. Their enzymes hydrolyzed phenyl α-maltoside into glucose and phenyl α-glucoside. They hydrolyzed amylose liberating α-glucose. Maltotriose was the main α-glucosyltransfer product formed from maltose by the three α-glucosidases. 相似文献