全文获取类型
收费全文 | 5626篇 |
免费 | 322篇 |
国内免费 | 541篇 |
出版年
2023年 | 45篇 |
2022年 | 66篇 |
2021年 | 109篇 |
2020年 | 129篇 |
2019年 | 124篇 |
2018年 | 99篇 |
2017年 | 109篇 |
2016年 | 130篇 |
2015年 | 115篇 |
2014年 | 182篇 |
2013年 | 379篇 |
2012年 | 219篇 |
2011年 | 243篇 |
2010年 | 214篇 |
2009年 | 295篇 |
2008年 | 356篇 |
2007年 | 323篇 |
2006年 | 291篇 |
2005年 | 263篇 |
2004年 | 249篇 |
2003年 | 233篇 |
2002年 | 163篇 |
2001年 | 153篇 |
2000年 | 134篇 |
1999年 | 156篇 |
1998年 | 151篇 |
1997年 | 124篇 |
1996年 | 113篇 |
1995年 | 140篇 |
1994年 | 149篇 |
1993年 | 138篇 |
1992年 | 128篇 |
1991年 | 107篇 |
1990年 | 82篇 |
1989年 | 84篇 |
1988年 | 99篇 |
1987年 | 100篇 |
1986年 | 65篇 |
1985年 | 37篇 |
1984年 | 53篇 |
1983年 | 28篇 |
1982年 | 31篇 |
1981年 | 18篇 |
1980年 | 16篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 5篇 |
1976年 | 10篇 |
1975年 | 3篇 |
1972年 | 3篇 |
排序方式: 共有6489条查询结果,搜索用时 78 毫秒
1.
2.
Jonathan H. Clarke Judith I. Laurie Harry J. Gilbert Geoffrey P. Hazlewood 《FEMS microbiology letters》1991,83(3):305-309
Cellulomonas fimi genomic DNA encoding xylanase activity has been cloned and expressed in Escherichia coli. As judged by DNA hybridization and restriction analysis, twelve xylanase-positive clones carried a minimum of four different xylanase (xyn) genes. The encoded enzymes were devoid of cellulase activity but three of the four bound to Avicel. 相似文献
3.
Abstract The gene-protein database was used to obtain the two-dimensional polyacrylamide gel coordinates of proteins phosphorylated in extracts of Escherichia coli including those phosphorylated by eukaryotic-like kinase activities. These suggest that the phosphoproteins correspond to, or co-migrate with, the product of an open reading frame at 1.3 min (Orf80), Enzyme 1 of the phosphoenolpyruvate-dependent phosphotransferase system (Ptsl), the tRNA synthetase for histidine (HisS), and proteins involved in the response to carbon starvation and quinone treatment. 相似文献
4.
A.N. Reshetilov A.B. Medvinsky T.P. Eliseeva V.Yu. Shakhbazian M.A. Tsyganov A.M. Boronin G.R. Ivanitsky 《FEMS microbiology letters》1992,94(1-2):59-62
A method of pH distribution measurements in agar nutrient media containing expanding bacterial populations is described. It is based on measuring pH microsamples taken at different points of the media. The sample volume was 10 microliters. A pH sensitive field effect transistor was used as a measuring electrode. Acidification was found to occur in glucose media, while alkalization occurred in the media containing peptone. 相似文献
5.
Craig A. Bloch Sheng-He Huang Christopher K. Rode Kwang Sik Kim 《FEMS microbiology letters》1996,144(2-3):171-176
Abstract The most virulent newborn meningitis-associated Escherichia coli are of the serotype O18: K1: H7. We previously isolated a large number of E. coli O18:K1:H7 mutants resulting from transposon Tn phoA mutagenesis that fail to invade brain microvascular endothelial cells. We have now determined the locations of 45 independent insertions. Twelve were localized to the 98 min region, containing a 120 kb segment that is characteristic of E. coli O18:K1:H7. Another, the previously described insertion ibe -10::Tn phoA , was localized to the 87 min region, containing a 20 kb segment found in this E. coli . These noninvasion mutations may define new O18:K1:H7 pathogenicity islands carrying genes for penetration of the blood-brain barrier of newborn mammals. 相似文献
6.
7.
Abhishek Chatterjee Celia Caballero-Franco Dannika Bakker Stephanie Totten Armando Jardim 《The Journal of biological chemistry》2015,290(42):25579-25594
Enterohemorrhagic Escherichia coli is a causative agent of gastrointestinal and diarrheal diseases. Pathogenesis associated with enterohemorrhagic E. coli involves direct delivery of virulence factors from the bacteria into epithelial cell cytosol via a syringe-like organelle known as the type III secretion system. The type III secretion system protein EspD is a critical factor required for formation of a translocation pore on the host cell membrane. Here, we show that recombinant EspD spontaneously integrates into large unilamellar vesicle (LUV) lipid bilayers; however, pore formation required incorporation of anionic phospholipids such as phosphatidylserine and an acidic pH. Leakage assays performed with fluorescent dextrans confirmed that EspD formed a structure with an inner diameter of ∼2.5 nm. Protease mapping indicated that the two transmembrane helical hairpin of EspD penetrated the lipid layer positioning the N- and C-terminal domains on the extralumenal surface of LUVs. Finally, a combination of glutaraldehyde cross-linking and rate zonal centrifugation suggested that EspD in LUV membranes forms an ∼280–320-kDa oligomeric structure consisting of ∼6–7 subunits. 相似文献
8.
A.S. Purewal 《FEMS microbiology letters》1991,82(2):229-232
The nucleotide sequence of the gene specifying the ethidium efflux system of Escherichia coli has been determined. The translated open reading frame has identified a membrane-bound polypeptide of 110 amino acids (11,960 Da) which shares 42% identity with a staphylococcal protein specifying resistance to ethidium. 相似文献
9.
Chiaki Sato Atushi Katumata Ikuo Takashima Nobuo Hashimoto 《FEMS microbiology letters》1991,80(2-3):201-206
Abstract: Genes from Chlamydia psittaci P-1041 were cloned into the Bam HI site of pUC19 and were transformed to host Escherichia coli JM109. Two recombinant plasmids that expressed protein antigens of Chlamydia were isolated. The sizes of the DNA fragments were 1350 and 1710 bp, and encoded for polypeptides of M r 25 and 42 kilodaltons (kDa), respectively. The 25-kDa protein had cross-reactivity with antisera to ten C. psittaci strains and two C. trachomatis strains, whereas the 42-kDa protein reacted only with homologous antiserum to the C. psittaci P-1041 strain. Furthermore, in Southern hybridization analysis these two fragments as probes hybridized with DNA of ten C. psittaci strains and four C. trachomatis strains. These results indicated that the two fragments shared a DNA sequence common to the chlamydial genus. 相似文献
10.
Christine Jacobs Alain Dubus Didier Monnaie Staffan Normark Jean-Marie Frère 《FEMS microbiology letters》1992,92(1):95-100
The involvement of the serine residue 318 in the specificity of a class C beta-lactamase was investigated. Multiple site-directed mutants at this position were generated using a polymerase chain reaction technique. These mutants were then probed for their activity towards various beta-lactam compounds. One mutant, S318G was further purified and its physico-chemical and catalytic properties determined. It was shown that the observed minimal inhibitory concentration values of this mutant could be correlated to its kinetic properties using a 'diffusion-hydrolysis' model. However, the data showed that residue 318 has little influence on the specificity of class C beta-lactamases. 相似文献