首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   167篇
  免费   7篇
  174篇
  2023年   1篇
  2022年   1篇
  2021年   4篇
  2020年   1篇
  2019年   1篇
  2018年   2篇
  2017年   6篇
  2016年   6篇
  2015年   7篇
  2014年   13篇
  2013年   8篇
  2012年   13篇
  2011年   13篇
  2010年   12篇
  2009年   7篇
  2008年   11篇
  2007年   13篇
  2006年   12篇
  2005年   7篇
  2004年   7篇
  2003年   1篇
  2002年   9篇
  2001年   4篇
  2000年   6篇
  1999年   1篇
  1998年   1篇
  1997年   4篇
  1992年   2篇
  1991年   1篇
排序方式: 共有174条查询结果,搜索用时 15 毫秒
1.
Abstract

The antioxidant effects of ellagic acid (EA) and hesperidin (HES) against skeletal muscle ischemia/reperfusion injury (I/R) were performed. Hindlimb ischemia has been induced by tourniquet occlusion for 2?h on left hindlimb. At the end of ischemia, the tourniquate has been removed and initiated reperfusion for 2?h. EA (100?mg/kg) has been applied orally before ischemia/reperfusion in the EA?+?I/R group. HES (100?mg/kg) has been given orally in the HES?+?I/R group. The left gastrocnemius muscle has been harvested and stored immediately at??80?°C until assessed for the levels of MDA and antioxidant enzymes activities. MDA level has statistically increased in I/R group (p?<?0.05) compared to other groups. The muscle tissue antioxidant enzymes activities were lower than the other groups in the I/R group (p?<?0.05). EA and HES treatments significantly reversed the damage level in I/R, also activity of tissue SOD increased in the EA?+?I/R and HES?+?I/R groups.  相似文献   
2.
High-level secretory expression of wheat (Triticum aestivum) germin/oxalate oxidase was achieved in Pichia pastoris fermentation cultures as an alpha-mating factor signal peptide fusion, based on the native wheat cDNA coding sequence. The oxalate oxidase activity of the recombinant enzyme is substantially increased (7-fold) by treatment with sodium periodate, followed by ascorbate reduction. Using these methods, approximately 1 g (4x10(4) U) of purified, activated enzyme was obtained following eight days of induction of a high density Pichia fermentation culture, demonstrating suitability for large-scale production of oxalate oxidase for biotechnological applications. Characterization of the recombinant protein shows that it is glycosylated, with N-linked glycan attached at Asn47. For potential biomedical applications, a nonglycosylated (S49A) variant was also prepared which retains essentially full enzyme activity, but exhibits altered protein-protein interactions.  相似文献   
3.
A recombinant dog gastric lipase with therapeutic potential for the treatment of exocrine pancreatic insufficiency was expressed in transgenic tobacco plants. We targeted the protein using two different signal sequences for either vacuolar retention or secretion. In both cases, an active glycosylated recombinant protein was obtained. The recombinant enzymes and the native enzyme displayed similar properties including acid resistance and acidic optimum pH. The proteolytic maturation and the specific activity of the recombinant proteins, however, were found to be dependent on subcellular compartmentalization. Expression levels of recombinant dog gastric lipase were about 5% and 7% of acid extractable plant proteins for vacuolar retention and secretion respectively. This expression system already has allowed the production of tens of grams of purified lipase through open-field culture of transgenic tobacco plants.  相似文献   
4.
Mara? powder is a kind of smokeless tobacco used in the south-eastern region of Turkey. The present study was carried out to assess possible DNA damage in exfoliated oral cells of Mara? powder users by analysing the frequencies of micronuclei (MN), which is a simple and reliable biomarker for genotoxic damage and to screen for the detection of site-specific differences in the frequencies of MN. The mean (±SD) MN frequency in the inner lip mucosa site was 1.27(±0.55) % for Mara? powder users and 0.88(±0.47) % for non-smoking control subjects (p < 0.05) and 0.82(±0.40) % for the buccal site of Mara? powder users (p < 0.01). There was no significant site-specific difference between the inner lip site and the buccal mucosa site 0.73(±0.43) % in the MN frequency of non-smoking control subjects (p > 0.05). There was no significant effect of daily consumption of Mara? powder, and duration of usage on MN frequencies. The present study suggests that the oral use of smokeless tobacco represents a genotoxic hazard and also that use of MN from a single site may be misleading as a marker of genotoxic exposure. Habitual use of Mara? powder should be taken into account and could be considered unsafe.  相似文献   
5.
The neurodegenerative disorder amyotrophic lateral sclerosis may render patients unable to speak or write, so that objective assessment of cognitive impairment, which is commonly of a dysexecutive nature, is challenging. There is therefore a need to develop other methods of assessment that utilize other relatively unaffected motor systems. In this proof-of-principle study a novel eye-tracking version of the trail-making test was compared with performance on the standard written version in a group of healthy volunteers. There was good correlation for speed between both versions of Part B (R2=0.73), suggesting that this is a viable method to objectively assess cognitive impairment in disorders where patients are unable to speak or write.  相似文献   
6.
The ability to selectively measure serine enantiomer concentrations in rat brain microdialysate is essential during drug discovery to study the interaction of d-serine with the N-methyl-d-aspartate (NMDA) subtype of the glutamate receptor. NMDA receptor-stimulating agents, such as d-serine, have been shown to reduce the negative symptoms and cognitive dysfunction in individuals with schizophrenia when added to conventional or atypical antipsychotic drug regimens. In the work presented here, an LC/MS/MS assay was developed and validated to simultaneously measure d-serine and l-serine concentrations in rat brain microdialysate. Reverse phase chromatographic resolution of the enantiomers was obtained through derivatization with 1-fluoro-2,4-dinitrophenyl-5-l-alanine amide (Marfey's reagent). The assay was validated to determine concentrations over the range of 10-7500 ng/mL using electrospray ionization and multiple reaction monitoring (MRM). Both intra- and inter-day precision and accuracy were less than 16.5% (RE) and 7% (CV) for both analytes, respectively, and assay throughput was increased significantly relative to existing methodologies.  相似文献   
7.
8.
Implementing a recall paradigm without hypnosis, we use functional MRI (fMRI) to explore and compare nociceptive and centrally-driven pain experiences. We posit that a trace of a recent nociceptive event can be used to create sensory-re-experiencing of pain that can be qualified in terms of intensity and vividness. Fifteen healthy volunteers received three levels of thermal stimuli (warm, low pain and high pain) and subsequently were asked to recall and then rate this experience. Neuroimaging results reveal that recalling a previous sensory experience activates an extensive network of classical pain processing structures except the contralateral posterior insular cortex. Nociceptive-specific activation of this structure and the rated intensity difference between physical and recalled pain events allow us to investigate the link between the quality of the original nociceptive stimulus and the mental trace, as well as the differences between the accompanying neural responses. Additionally, by incorporating the behavioural ratings, we explored which brain regions were separately responsible for generating either an accurate or vivid recall of the physical experience. Together, these observations further our understanding of centrally-mediated pain experiences and pain memory as well as the potential relevance of these factors in the maintenance of chronic pain.  相似文献   
9.
The synthesis and SAR studies of spiroquinazolinones as novel PDE7 inhibitors are discussed. The best compounds from the series displayed nanomolar inhibitory affinity and were selective versus other PDE isoenzymes.  相似文献   
10.
A liquid chromatographic-tandem mass spectrometric (LC-MS-MS) assay was developed and validated to quantitatively determine olanzapine (OLZ) concentrations in human blood. Liquid-liquid extraction, using n-butanol:cyclohexane (3:47, v/v), was used to isolate OLZ and its internal standard, LY170158, from the biological matrix. Chromatographic resolution of OLZ from endogenous interferences and known metabolites was accomplished with a MetaChem Monochrom HPLC column (4.6 x 150 mm, d(p) 5 microm). Detection occurred using a Perkin-Elmer Sciex API III Plus triple quadrupole mass spectrometer using positive ion APCI and multiple reaction monitoring (MRM). The linear dynamic range was from 5 to 500 ng ml(-1) based on a 0.25-ml aliquot of human blood. The inter-day precision (%RSD) and accuracy (%RE) ranged from 3.65 to 10.64 and from -2.14 to 3.07, respectively. Modifications to an existing assay for the determination of OLZ in human plasma were necessary. A different structural analog was used as the internal standard due to instability observed for the original analog when using human blood as the matrix. A second modification was the addition of the anti-oxidant sodium ascorbate to inhibit degradation of OLZ in human blood, as has been noted by other investigators. Upon fortification of human blood with sodium ascorbate (final concentration, 0.33 mM), OLZ was found to be stable for at least 1 week at -70 degrees C as well as through two freeze-thaw cycles. This assay, which will be used to investigate the distribution of OLZ in human blood, grants insight into the proper sample handling conditions needed to perform valid determinations of OLZ in human blood.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号