全文获取类型
收费全文 | 393篇 |
免费 | 47篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 10篇 |
2017年 | 11篇 |
2016年 | 20篇 |
2015年 | 21篇 |
2014年 | 15篇 |
2013年 | 27篇 |
2012年 | 34篇 |
2011年 | 33篇 |
2010年 | 23篇 |
2009年 | 15篇 |
2008年 | 20篇 |
2007年 | 22篇 |
2006年 | 17篇 |
2005年 | 31篇 |
2004年 | 19篇 |
2003年 | 29篇 |
2002年 | 14篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有440条查询结果,搜索用时 234 毫秒
91.
Azosprillum inoculated withRhizobium improved the nodulation of chickpea-Cicer arietinum. This interaction was further enhanced by organic matter present in the growth medium. 相似文献
92.
93.
Belleudi F Leone L Nobili V Raffa S Francescangeli F Maggio M Morrone S Marchese C Torrisi MR 《Traffic (Copenhagen, Denmark)》2007,8(12):1854-1872
The keratinocyte growth factor receptor (KGFR)/fibroblast growth factor receptor 2b is activated by high-affinity-specific interaction with two different ligands, keratinocyte growth factor (KGF)/fibroblast growth factor (FGF)7 and FGF10/KGF2, which are characterized by an opposite requirement of heparan sulfate proteoglycans and heparin for binding to the receptor. We investigated here the possible different endocytic trafficking of KGFR, induced by the two ligands. Immunofluorescence and immunoelectron microscopy analysis showed that KGFR internalization triggered by either KGF or FGF10 occurs through clathrin-coated pits. Immunofluorescence confocal microscopy using endocytic markers as well as tumor susceptibility gene 101 (TSG101) silencing demonstrated that KGF drives KGFR to the degradative pathway, while FGF10 targets the receptor to the recycling endosomes. Biochemical analysis showed that KGFR is ubiquitinated and degraded after KGF treatment but not after FGF10 treatment, and that the alternative fate of KGFR might depend on the different ability of the receptor to phosphorylate the fibroblast growth factor receptor substrate 2 (FRS2) substrate and to recruit the ubiquitin ligase c-Cbl. The recycling endocytic pathway followed by KGFR upon FGF10 stimulation correlates with the higher mitogenic activity exerted by this ligand on epithelial cells compared with KGF, suggesting that the two ligands may play different functional roles through the regulation of the receptor endocytic transport. 相似文献
94.
Francesca Sisto Maria Maddalena Scaltrito Giuseppe Russello Arianna Bonomi Francesco Dubini 《Current microbiology》2009,58(6):559-563
Antibiotic susceptibility testing of Helicobacter pylori isolates was performed by broth microdilution method with MegaCellTM RPMI-1640 Medium (SIGMA). Fifty five clinical isolates of H. pylori were tested against metronidazole, tinidazole, amoxicillin, and clarithromycin. The results were compared to those obtained
by standard agar dilution method. The microdilution method performed with new medium, showed excellent correlation with agar
dilution results, with 100% agreement for metronidazole, 96.3% for amoxicillin, 90.7% for clarithromycin, and 92.8% for tinidazole.
MICs determined by proposed method were highly reproducible: replicate results were variable within one-two-fold dilution
by using different inocula and different batches of medium. 相似文献
95.
Maddalena Rossi Pietro Buzzini Lisa Cordisco Alberto Amaretti Maurizio Sala Stefano Raimondi Chiara Ponzoni Ugo Maria Pagnoni & Diego Matteuzzi 《FEMS microbiology ecology》2009,69(3):363-372
Obligate psychrophilic, facultative psychrophilic, and mesophilic yeasts were cultured in a carbon-rich medium at different temperatures to investigate whether growth parameters, lipid accumulation, and fatty acid (FA) composition were adaptive and/or acclimatory responses. Acclimation of facultative psychrophiles and mesophiles to a lower temperature decreased their specific growth rate, but did not affect their biomass yield (YX/S ). Obligate and facultative psychrophiles exhibited the highest YX/S . Acclimation to lower temperature decreased the lipid yield (YL/X ) in mesophilic yeasts, but did not affect YL/X in facultative psychrophilic ones. Similar YL/X were found in both groups of psychrophiles, suggesting that lipid accumulation is not a distinctive characteristic of adaptation to permanently cold environments. The unsaturation of FAs was one major adaptive feature of the yeasts colonizing permanently cold ecosystems. Remarkable amounts of α-linolenic acid were found in obligate psychrophiles at the expense of linoleic acid, whereas it was scarce or absent in all the other strains. Increased unsaturation of FAs was also a general acclimatory response of facultative psychrophiles to a lower temperature. These results improve the knowledge of the responses enabling psychrophilic yeasts to cope with the cold and may be of support for potential biotechnological exploitation of these strains. 相似文献
96.
97.
Serdar Korur Roland M. Huber Balasubramanian Sivasankaran Michael Petrich Pier Morin Jr Brian A. Hemmings Adrian Merlo Maria Maddalena Lino 《PloS one》2009,4(10)
Cancers are driven by a population of cells with the stem cell properties of self-renewal and unlimited growth. As a subpopulation within the tumor mass, these cells are believed to constitute a tumor cell reservoir. Pathways controlling the renewal of normal stem cells are deregulated in cancer. The polycomb group gene Bmi1, which is required for neural stem cell self-renewal and also controls anti-oxidant defense in neurons, is upregulated in several cancers, including medulloblastoma. We have found that Bmi1 is consistently and highly expressed in GBM. Downregulation of Bmi1 by shRNAs induced a differentiation phenotype and reduced expression of the stem cell markers Sox2 and Nestin. Interestingly, expression of glycogen synthase kinase 3 beta (GSK3β), which was found to be consistently expressed in primary GBM, also declined. This suggests a functional link between Bmi1 and GSK3β. Interference with GSK3β activity by siRNA, the specific inhibitor SB216763, or lithium chloride (LiCl) induced tumor cell differentiation. In addition, tumor cell apoptosis was enhanced, the formation of neurospheres was impaired, and clonogenicity reduced in a dose-dependent manner. GBM cell lines consist mainly of CD133-negative (CD133-) cells. Interestingly, ex vivo cells from primary tumor biopsies allowed the identification of a CD133- subpopulation of cells that express stem cell markers and are depleted by inactivation of GSK3β. Drugs that inhibit GSK3, including the psychiatric drug LiCl, may deplete the GBM stem cell reservoir independently of CD133 status. 相似文献
98.
99.
Stefano Raimondi Daniela Uccelletti Alberto Amaretti Alan Leonardi Claudio Palleschi Maddalena Rossi 《Applied microbiology and biotechnology》2010,86(3):871-878
The Kluyveromyces lactis Cu/Zn SOD gene (SOD1) was fused with the toxin K1 signal sequence to obtain extracellular production of superoxide dismutase. Kluyveromyces marxianus L3 and K. lactis MW98-8C strains were transformed and compared as hosts for the secretion. The effects of the media composition were evaluated:
In K. lactis, the highest volumetric activity was obtained in YKK synthetic medium in the presence of Cu2+/Zn2+ cofactors (9.6 kU l−1). In K. marxianus, active SOD was produced only in YPD medium supplemented with Cu2+ and Zn2+ (8.8 kU l−1). In order to improve the production of secreted active SOD in K. lactis, the SOD1 copper carrier (CCS1) was overexpressed and targeted to the secretory apparatus. A positive effect was observed
only when K. lactis was grown in a medium without Cu2+/Zn2+ supplement. The best performing culture conditions for K. lactis and K. marxianus recombinant strains were successfully applied to two laboratory-scale fed-batch processes, and volumetric SOD activities
increased up to 19.4 and 24.1 kU l−1, respectively. 相似文献
100.
Maddalena Bayer‐Giraldi Christiane Uhlig Uwe John Thomas Mock Klaus Valentin 《Environmental microbiology》2010,12(4):1041-1052
Fragilariopsis is a dominating psychrophilic diatom genus in polar sea ice. The two species Fragilariopsis cylindrus and Fragilariopsis curta are able to grow and divide below freezing temperature of sea water and above average sea water salinity. Here we show that antifreeze proteins (AFPs), involved in cold adaptation in several psychrophilic organisms, are widespread in the two polar species. The presence of AFP genes (afps) as a multigene family indicated the importance of this group of genes for the genus Fragilariopsis, possibly contributing to its success in sea ice. Protein phylogeny showed the potential mobility of afps, which appear to have crossed kingdom and domain borders, occurring in Bacteria, diatoms, crustaceans and fungi. Our results revealed a broad distribution of AFPs not only in polar organisms but also in taxa apparently not related to cold environments, suggesting that these proteins may be multifunctional. The relevance of AFPs to Fragilariopsis was also shown by gene expression analysis. Under stress conditions typical for sea ice, with subzero temperatures and high salinities, F. cylindrus and F. curta strongly expressed selected afps. An E/G point mutation in the Fragilariopsis AFPs may play a role in gene expression activity and protein function. 相似文献