全文获取类型
收费全文 | 13636篇 |
免费 | 889篇 |
国内免费 | 2篇 |
专业分类
14527篇 |
出版年
2022年 | 81篇 |
2021年 | 141篇 |
2019年 | 93篇 |
2018年 | 129篇 |
2017年 | 108篇 |
2016年 | 205篇 |
2015年 | 322篇 |
2014年 | 350篇 |
2013年 | 788篇 |
2012年 | 653篇 |
2011年 | 606篇 |
2010年 | 334篇 |
2009年 | 380篇 |
2008年 | 587篇 |
2007年 | 583篇 |
2006年 | 593篇 |
2005年 | 598篇 |
2004年 | 626篇 |
2003年 | 600篇 |
2002年 | 559篇 |
2001年 | 543篇 |
2000年 | 529篇 |
1999年 | 437篇 |
1998年 | 174篇 |
1997年 | 157篇 |
1996年 | 142篇 |
1995年 | 109篇 |
1994年 | 125篇 |
1993年 | 129篇 |
1992年 | 330篇 |
1991年 | 305篇 |
1990年 | 310篇 |
1989年 | 283篇 |
1988年 | 238篇 |
1987年 | 240篇 |
1986年 | 211篇 |
1985年 | 181篇 |
1984年 | 139篇 |
1983年 | 133篇 |
1982年 | 117篇 |
1981年 | 109篇 |
1980年 | 90篇 |
1979年 | 117篇 |
1978年 | 91篇 |
1977年 | 81篇 |
1976年 | 81篇 |
1975年 | 71篇 |
1974年 | 86篇 |
1973年 | 93篇 |
1969年 | 67篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
A biosensor consisting of immobilized nitrite oxidizing bacteria and an oxygen electrode has been developed for the amperometric determination of NO(2) (nitrogen dioxide) gas. The response time for the determination of NO(2) was within 3 min. A linear relationship was observed between the current decrease and the NO(2) concentration below 255 ppm. The minimum concentration for the determination of NO(2) was 0.51 ppm. The current decrease was reproducible within +/-4% of the relative error. The selectivity of the microbial sensor for NO(2) was satisfactory. The current output of the sensor was almost constant for more than 24 days and 400 assays. 相似文献
102.
The overall reaction kinetics of Corynebacterium sarcosine oxidase were investigated and the reaction was shown to follow a ping-pong, bi-bi mechanism with two substrates, sarcosine and molecular oxygen. Sarcosine analogs, such as acetate, propionate and methoxyacetate, were competitive inhibitors of the reaction. Acetate caused characteristic alterations in optical and circular dichroic spectra, indicating that the microenvironment of the substrate-binding region of the enzyme increased in hydrophobicity on binding with the substrate analog. The dissociation constants of the analogs calculated from the spectral changes were in agreement with the kinetic inhibition constants. Inorganic metallic ions were also inhibitory. Of interest was the finding that the inhibition by Hg2+ was proportional to the square of its concentration, which suggests that at least two sulfhydryl groups are related to the catalytic activity of the enzyme. 相似文献
103.
Benzyladenine (BA) stimulated division but not expansion ofmesophyll cells and repressed chlorophyll accumulation in attachedyoung bean leaves. Even in the presence of fluorodeoxyuridine(FUdR) or mitomycin C which causes complete suppression of BA-inducedincrease in DNA content, BA increased RNA and protein contentsand fresh weight, but decreased chlorophyll accumulation. Moreover,BA n the presence of FUdR induced marked cell expansion. Inthe presence of a-amanitin (AM), BA did not produce any changein DNA content, fresh weight or cell size. All of the BA effectswere observed even in the presence of fluorouracil (FU) plusthymidine (TdR). AM and cycloheximide added 012 h effectively inhibitedBA-stimulated cell division but showed no effect if added at18 h. FU plus TdR added 018 h had almostno effect onthe cell number at 24 h. These results indicate that BA stimulates the mRNA synthesisnecessary for induction of cell division, and that the synthesisof cytoplasmic rRNA is not always necessary for BA-stimulatedcell division, and moreover, that BA stimulates expansion growthof cells in which DNA synthesis is suppressed. (Received August 16, 1982; Accepted March 31, 1983) 相似文献
104.
Rice root glutamate synthase activity was assayed with various reducing systems. Ferredoxin-dependent glutamate synthase (EC 1.4.7.1) and pyridine nucleotide-dependent glutamate synthase (NADH, EC 1.4.1.14; or NADPH, EC 1.4.1.13) exhibited a strict specificity for the electron donor. The ferredoxin-dependent glutamate synthase from rice roots could accept electrons from photoreduced ferredoxin in an illuminated reconstituted spinach chloroplast system. Thioredoxin, a potent electron carrier, was not able to provide either ferredoxin-dependent or pyridine nucleotide-dependent glutamate synthase with electrons as no glutamate formation was detected in the presence of reduced thioredoxin f or m. 相似文献
105.
The reversibility of the adenylate cyclase reaction 总被引:1,自引:0,他引:1
K Takai Y Kurashina C Suzuki H Okamoto A Ueki 《The Journal of biological chemistry》1971,246(18):5843-5845
106.
107.
Studies on ATP citrate lyase of rat liver. IV. The role of CoA 总被引:1,自引:0,他引:1
108.
109.
110.
Formation of Recombinants Between Nontransmissible Drug-Resistance Determinants and Transfer Factors 总被引:5,自引:2,他引:3 下载免费PDF全文
Susumu Mitsuhashi Mitsuo Kameda Kenji Harada Mitsue Suzuki 《Journal of bacteriology》1969,97(3):1520-1521
Noninfectious drug-resistance determinants acquired conjugal transmissibility by the formation of recombinants with transfer factors, suggesting the origin of R factors. 相似文献