全文获取类型
收费全文 | 330篇 |
免费 | 29篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 10篇 |
2020年 | 11篇 |
2019年 | 19篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 12篇 |
2015年 | 15篇 |
2014年 | 28篇 |
2013年 | 23篇 |
2012年 | 32篇 |
2011年 | 27篇 |
2010年 | 14篇 |
2009年 | 15篇 |
2008年 | 23篇 |
2007年 | 20篇 |
2006年 | 16篇 |
2005年 | 15篇 |
2004年 | 15篇 |
2003年 | 10篇 |
2002年 | 9篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1995年 | 2篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
排序方式: 共有359条查询结果,搜索用时 15 毫秒
1.
Dennis A. Bazylinski Anthony J. Garratt-Reed Afshin Abedi Richard B. Frankel 《Archives of microbiology》1993,160(1):35-42
Greigite (Fe3S4) and pyrite (FeS2) particles in the magnetosomes of a many-celled, magnetotactic prokaryote (MMP), common in brackish-to-marine, sulfidic, aquatic habitats, contained relatively high concentrations of copper which ranged from about 0.1 to 10 atomic per cent relative to iron. In contrast, the greigite particles in the magnetosomes of a curved magnetotactic bacterium collected from the same sampling site did not contain significant levels of copper. The ability of the MMP to biomineralize copper within its magnetosomes appeared to be limited to that organism and dependent upon the site from which it was collected. Although the chemical mechanism and physiological function of copper accumulation in the magnetosomes of the MMP is unclear, the presence of copper is the first evidence that another transition metal ion could be incorporated in the mineral phase of the magnetosomes of a magnetotactic bacterium.Abbreviation MMP
many-celled magnetotactic prokaryote 相似文献
2.
3.
Razieh Jafari Hajati Najmeh Ahmadian Chashmi 《Preparative biochemistry & biotechnology》2013,43(10):1010-1019
AbstractBetulin (B) and betulinic acid (BA) are two triterpenoids with a wide range of biological and medicinal activities in different organs of Betula pendula. This research aimed to increase the accumulation of B and BA in the hairy root culture of B. pendula by seven biotic and abiotic elicitors. Hairy root was induced in the stem’s inner bark of B. pendula using the C58C1 strain in the WPM (Woody Plant Medium). The effects of different concentrations of elicitors and different time of root harvest in hairy root culture of B. pendula showed that highest level of growth index (GI), B, and BA was acquired in treated hairy roots with chitosan (CTS), chlorocholine chloride (CCC) and chitosan nano-fiber (CTS NF). Highest GI of B. pendula hairy roots was 13 that was obtained in the roots treated with CTS 150?mg l?1 on the 8th day. The highest content of BA was 1.3?mg g?1 DW after treatment with 1?mg l?1CCC on the 4th and 6th days and 200?mg l?1CTS NF on the 10th day. The highest B content (0.94?mg g?1DW) was obtained in the treated hairy root by 2?mg l?1 CCC after 4 and 6?days. 相似文献
4.
Afshin Salimeh Mustafa Mohammadi Bahman Rashidi 《Journal of physiology and biochemistry》2013,69(2):255-265
This study was aimed to evaluate the preventive effect of diosgenin and exercise on tissue antioxidant status in isoproterenol-induced myocardial infarction (MI) in male Wistar rats. Levels of lipid peroxides, reduced glutathione (GSH), and the activities of glutathione-dependent antioxidant enzymes (glutathione peroxidise and glutathione reductase) and antiperoxidative enzymes (catalase and superoxide dismutase) in the plasma and the heart tissue of experimental groups of rats were determined. Pretreatment with diosgenin and exercise exerted an antioxidant effect against isoproterenol-induced myocardial infarction by blocking the induction of lipid peroxidation. A tendency to prevent the isoproterenol-induced alterations in the level of GSH, in the activities of glutathione-dependent antioxidant enzymes and antiperoxidative enzymes was also observed. Histopathological findings of the myocardial tissue showed a protective role for combination of diosgenin and exercise in isoproterenol (ISO)-treated rats. Thus, the present study reveals that preconditioning with diosgenin and exercise exerts cardioprotective effect against ISO-induced MI due to its free radical scavenging and antioxidant effects, which maintains the tissue defense system against myocardial damage. 相似文献
5.
Karen Cawley Susan E. Logue Adrienne M. Gorman Qingping Zeng John Patterson Sanjeev Gupta Afshin Samali 《PloS one》2013,8(8)
Global downregulation of microRNAs (miRNAs) is a common feature of human tumors and has been shown to enhance cancer progression. Several components of the miRNA biogenesis machinery (XPO5, DICER and TRBP) have been shown to act as haploinsufficient tumor suppressors. How the deregulation of miRNA biogenesis promotes tumor development is not clearly understood. Here we show that loss of miRNA biogenesis increased resistance to endoplasmic reticulum (ER) stress-induced cell death. We observed that HCT116 cells with a DICER hypomorphic mutation (Exn5/Exn5) or where DICER or DROSHA were knocked down were resistant to ER stress-induced cell death. Extensive analysis revealed little difference in the unfolded protein response (UPR) of WT compared to Exn5/Exn5 HCT116 cells upon ER stress treatment. However, analysis of the intrinsic apoptotic pathway showed that resistance occurred upstream of the mitochondria. In particular, BAX activation and dissipation of mitochondrial membrane potential was attenuated, and there was altered expression of BCL-2 family proteins. These observations demonstrate a key role for miRNAs as critical modulators of the ER stress response. In our model, downregulation of miRNA biogenesis delays ER stress-induced apoptosis. This suggests that disrupted miRNA biogenesis may contribute to cancer progression by inhibiting ER stress-induced cell death. 相似文献
6.
7.
Setareh Tavassoli Krzysztof Hinc Adam Iwanicki Michal Obuchowski Gholamreza Ahmadian 《Archives of microbiology》2013,195(3):197-202
The production of highly efficient, recyclable and cost-effective enzymes is one of the most important goals in industrial biotechnology. Bacterial spores are highly resistant to harsh environmental conditions, easy to produce and are suitable for manipulation of genetic materials. These features make them a very efficient tool for biotechnology. Here, we show the use bacterial spores for presentation of functional enzyme. Spore coat display was used to produce a biocatalyst, which expresses β-galactiosidase (LacA). This enzyme is commonly used to produce lactose-free milk for lactose intolerant individuals. The lacA gene from Bacillus subtilis strain 168 was expressed on the surface of B. subtilis RH101(ΔcotC) spores using CotC as protein carrier. Presence of LacA protein is verified by western blotting. Results of β-galactiosidase assay show that the expressed enzyme retained its activity in condition of freezing and drying, as well as after recovery from the reaction’s mixture. 相似文献
8.
9.
Afshin Iram Tauqeer Alam Javed M. Khan Taqi A. Khan Rizwan H. Khan Aabgeena Naeem 《PloS one》2013,8(8)
Conformational alterations of bovine hemoglobin (Hb) upon sequential addition of glyoxal over a range of 0–90% v/v were investigated. At 20% v/v glyoxal, molten globule (MG) state of Hb was observed by altered tryptophan fluorescence, high ANS binding, existence of intact heme, native-like secondary structure as depicted by far-UV circular dichroism (CD) and ATR-FTIR spectra as well as loss in tertiary structure as confirmed by near-UV CD spectra. In addition, size exclusion chromatography analysis depicted that MG state at 20% v/v glyoxal corresponded to expanded pre-dissociated dimers. Aggregates of Hb were detected at 70% v/v glyoxal. These aggregates of Hb had altered tryptophan environment, low ANS binding, exposed heme, increased β-sheet secondary structure, loss in tertiary structure, enhanced thioflavin T (ThT) fluorescence and red shifted Congo Red (CR) absorbance. On incubating Hb with 30% v/v glyoxal for 0–20 days, advanced glycation end products (AGEs) were detected on day 20. These AGEs were characterised by enhanced tryptophan fluorescence at 450 nm, exposure of heme, increase in intermolecular β-sheets, enhanced ThT fluorescence and red shift in CR absorbance. Comet assay revealed aggregates and AGEs to be genotoxic in nature. Scanning electron microscopy confirmed the amorphous structure of aggregates and branched fibrils of AGEs. The transformation of α-helix to β-sheet usually alters the normal protein to amyloidogenic resulting in a variety of protein conformational disorders such as diabetes, prion and Huntington''s. 相似文献
10.
Narges Riahi Amirhosein Kefayat Ahmad Ghasemi Mohammadhosein Asgarshamsi Mojtaba Panjehpoor Afshin Fassihi 《化学与生物多样性》2019,16(2)
Eight derivatives of tetrahydropyrimidine scaffold were designed and prepared as hybrid compounds possessing the structural features of both monastrol as an anticancer drug and nifedipine as a fascin blocking agent. All of the compounds were evaluated for their cytotoxic potency and the ability to inhibit 4T1 breast cancer cells migration. Then, they were investigated in silico for their ability to inhibit the fascin protein using molecular docking simulation. The most potent compound was 4d and the weakest one was 4a according to the in vitro cytotoxicity assay. The corresponding IC50 values were 193.70 and 248.75 μm , respectively. The least cytotoxic compound ( 4a ) was one of the strongest ones in binding to the fascin binding site according to the molecular docking results. 4a and 4e inhibited the 4T1 cells migration better than other compounds. They were more potent than nifedipine in inhibiting the migration process. In silico studies proved 4h to be the most potent fascin inhibitor in terms of ΔGbind although it was not inhibiting migration. The controversy between the in vitro and in silico results may cancel the theory of the involvement of the fascin inhibition in the migration inhibition. However, the considerable antimigratory effects of some of the synthesized compounds encourage performing further in vivo experiments to introduce novel tumor metastasis inhibitors. 相似文献