全文获取类型
收费全文 | 10552篇 |
免费 | 846篇 |
国内免费 | 3篇 |
出版年
2023年 | 52篇 |
2022年 | 60篇 |
2021年 | 226篇 |
2020年 | 158篇 |
2019年 | 209篇 |
2018年 | 258篇 |
2017年 | 245篇 |
2016年 | 341篇 |
2015年 | 560篇 |
2014年 | 609篇 |
2013年 | 789篇 |
2012年 | 1000篇 |
2011年 | 913篇 |
2010年 | 601篇 |
2009年 | 511篇 |
2008年 | 670篇 |
2007年 | 724篇 |
2006年 | 664篇 |
2005年 | 544篇 |
2004年 | 544篇 |
2003年 | 445篇 |
2002年 | 432篇 |
2001年 | 73篇 |
2000年 | 58篇 |
1999年 | 79篇 |
1998年 | 87篇 |
1997年 | 71篇 |
1996年 | 57篇 |
1995年 | 59篇 |
1994年 | 30篇 |
1993年 | 52篇 |
1992年 | 33篇 |
1991年 | 32篇 |
1990年 | 18篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 7篇 |
1986年 | 11篇 |
1985年 | 18篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 17篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1974年 | 7篇 |
1971年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Ma. Elena Flores C. 《Biotechnology letters》1991,13(2):101-106
Summary Ammonium represses erythromycin synthesis bySaccharopolyspora erythraea and insensitive mutants to this effect were isolated. Six mutants were selected and one of them produces 50% more antibiotic than the wild type in 100 mM NH4Cl as nitrogen source. Glutamine synthetase and alanine dehydrogenase levels in the mutants were determined and no differences with wild type strain were observed. 相似文献
3.
4.
Erica Raspelli Corinne Cassani Elena Chiroli Roberta Fraschini 《The Journal of biological chemistry》2015,290(1):1-12
Cyclin-dependent kinase (Cdk1) activity is required for mitotic entry, and this event is restrained by an inhibitory phosphorylation of the catalytic subunit Cdc28 on a conserved tyrosine (Tyr19). This modification is brought about by the protein kinase Swe1 that inhibits Cdk1 activation thus blocking mitotic entry. Swe1 levels are regulated during the cell cycle, and they decrease during G2/M concomitantly to Cdk1 activation, which drives entry into mitosis. However, after mitotic entry, a pool of Swe1 persists, and we collected evidence that it is involved in controlling mitotic spindle elongation. We also describe that the protein phosphatase Cdc14 is implicated in Swe1 regulation; in fact, we observed that Swe1 dephosphorylation in vivo depends on Cdc14 that, in turn, is able to control its subcellular localization. In addition we show that the lack of Swe1 causes premature mitotic spindle elongation and that high levels of Swe1 block mitotic spindle elongation, indicating that Swe1 inhibits this process. Importantly, these effects are not dependent upon the role of in Cdk1 inhibition. These data fit into a model in which Cdc14 binds and inhibits Swe1 to allow timely mitotic spindle elongation. 相似文献
5.
6.
Patrizia Casaline Delia Mezzanzanica Olga Valota Elena Adobati Antonella Tomassetti Maria I. Colnaghi Silvana Canevari 《Journal of cellular biochemistry》1995,58(1):47-55
The monoclonal antibody MOv19 directed to a folate binding protein shows temperature-dependent potentiation of binding of the noncompeting monoclonal antibody MOv18 to the relevant antigen, but the mechanism involved in this phinomenon had remained unclear. Use of chimeric versions of both monoclonal antibodies and the F(ab′)2 and fan fragments of MOv19 revealed an increment in MOv18 binding in all combinations irrespective of the orgin of the Fc portin of the monoclonal antibody. The potentiating effect of bivalent MOv19 fragments on 125l-MOv18 binding was similar to that of the entire monoclonal antibody and occurred at saturating concentrations of both reagents at which monovalent binding prevails. Similarly, the monovalent fragment also induced a significant increase in MOv18 bunding. Howener, the potentiation sccurred only at very high concentrations of antibody fragment. Homologous inhibition was drastically reduced using MOv19 Fab fragment, suggesting a low binding stability of the monovalent reagent. Immunoblotting analysis and binding in the presence of exogenous purified folate binding protein indicated a cross-linking between soluble and cell surface molecules mediated by the bivalent monoclonal antibodies. The extentof the increase in MOv18 binging at O°C with high amounts of exogenous folate binding protein was lower than that obtained at 370C in the absence of added molecule. Release of 125l-MOv18 from the cell surface was significantly higher in the absence of MOv19 than in its presence. Affinity constant values of 125l-MOv18 binding evaluated in the presence of MOv19 or control monoclonal antibody MINT5 were comparable, whereas the number of binding sites per cell detected by 125l-MOv18 was significantly higher in the presence of MOv19 than MINT5. Together, the data suggest that monoclonal antibody MOv19 induces a conformational change of the molecule it binds that increases the number of antigenic sites anvailable for MOv18 binding and, in turn, the binding stability of the latter, MOv19 bivalency also contributes to the MOv18 binding increment by cross-linking released and cell surface–anchored folate binding protein molecules. © Wiley-Liss, Inc. 相似文献
7.
Xiaolei Zhuang Elena Semenova Dragan Maric Robert Craigie 《The Journal of biological chemistry》2014,289(2):1119-1127
Barrier-to-autointegration factor (BAF or BANF1) is highly conserved in multicellular eukaryotes and was first identified for its role in retroviral DNA integration. Homozygous BAF mutants are lethal and depletion of BAF results in defects in chromatin segregation during mitosis and subsequent nuclear envelope assembly. BAF exists both in phosphorylated and unphosphorylated forms with phosphorylation sites Thr-2, Thr-3, and Ser-4, near the N terminus. Vaccinia-related kinase 1 is the major kinase responsible for phosphorylation of BAF. We have identified the major phosphatase responsible for dephosphorylation of Ser-4 to be protein phosphatase 4 catalytic subunit. By examining the cellular distribution of phosphorylated BAF (pBAF) and total BAF (tBAF) through the cell cycle, we found that pBAF is associated with the core region of telophase chromosomes. Depletion of BAF or perturbing its phosphorylation state results not only in nuclear envelope defects, including mislocalization of LEM domain proteins and extensive invaginations into the nuclear interior, but also impaired cell cycle progression. This phenotype is strikingly similar to that seen in cells from patients with progeroid syndrome resulting from a point mutation in BAF. 相似文献
8.
9.
10.
Mohammad Shamsur Rahman Maria Elena Martino Barbara Cardazzo Pierantonio Facco Paola Bordin Renzo Mioni Enrico Novelli Luca Fasolato 《Applied and environmental microbiology》2014,80(8):2372-2380
Vibrio is a very diverse genus that is responsible for different human and animal diseases. The accurate identification of Vibrio at the species level is important to assess the risks related to public health and diseases caused by aquatic organisms. The ecology of Vibrio spp., together with their genetic background, represents an important key for species discrimination and evolution. Thus, analyses of population structure and ecology association are necessary for reliable characterization of bacteria and to investigate whether bacterial species are going through adaptation processes. In this study, a population of Vibrionaceae was isolated from shellfish of the Venice lagoon and analyzed in depth to study its structure and distribution in the environment. A multilocus sequence analysis (MLSA) was developed on the basis of four housekeeping genes. Both molecular and biochemical approaches were used for species characterization, and the results were compared to assess the consistency of the two methods. In addition, strain ecology and the association between genetic information and environment were investigated through statistical models. The phylogenetic and population analyses achieved good species clustering, while biochemical identification was demonstrated to be imprecise. In addition, this study provided a fine-scale overview of the distribution of Vibrio spp. in the Venice lagoon, and the results highlighted a preferential association of the species toward specific ecological variables. These findings support the use of MLSA for taxonomic studies and demonstrate the need to consider environmental information to obtain broader and more accurate bacterial characterization. 相似文献