全文获取类型
收费全文 | 412篇 |
免费 | 26篇 |
专业分类
438篇 |
出版年
2023年 | 1篇 |
2022年 | 9篇 |
2021年 | 10篇 |
2020年 | 9篇 |
2019年 | 2篇 |
2018年 | 15篇 |
2017年 | 11篇 |
2016年 | 21篇 |
2015年 | 10篇 |
2014年 | 29篇 |
2013年 | 46篇 |
2012年 | 25篇 |
2011年 | 48篇 |
2010年 | 21篇 |
2009年 | 21篇 |
2008年 | 27篇 |
2007年 | 38篇 |
2006年 | 22篇 |
2005年 | 19篇 |
2004年 | 16篇 |
2003年 | 14篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有438条查询结果,搜索用时 0 毫秒
131.
Hyzinski-García MC Vincent MY Haskew-Layton RE Dohare P Keller RW Mongin AA 《Journal of neurochemistry》2011,118(1):140-152
In our previous work, we found that perfusion of the rat cerebral cortex with hypo-osmotic medium triggers massive release of the excitatory amino acid L-glutamate but decreases extracellular levels of L-glutamine (R. E. Haskew-Layton et al., PLoS ONE, 3: e3543). The release of glutamate was linked to activation of volume-regulated anion channels, whereas mechanism(s) responsible for alterations in extracellular glutamine remained unclear. When mannitol was added to the hypo-osmotic medium to reverse reductions in osmolarity, changes in microdialysate levels of glutamine were prevented, indicating an involvement of cellular swelling. As the main source of brain glutamine is astrocytic synthesis and export, we explored the impact of hypo-osmotic medium on glutamine synthesis and transport in rat primary astrocyte cultures. In astrocytes, a 40% reduction in medium osmolarity moderately stimulated the release of L-[(3) H]glutamine by ~twofold and produced no changes in L-[(3) H]glutamine uptake. In comparison, hypo-osmotic medium stimulated the release of glutamate (traced with D-[(3) H]aspartate) by more than 20-fold. In whole-cell enzymatic assays, we discovered that hypo-osmotic medium caused a 20% inhibition of astrocytic conversion of L-[(3) H]glutamate into L-[(3) H]glutamine by glutamine synthetase. Using an HPLC assay, we further found a 35% reduction in intracellular levels of endogenous glutamine. Overall, our findings suggest that cellular swelling (i) inhibits astrocytic glutamine synthetase activity, and (ii) reduces substrate availability for this enzyme because of the activation of volume-regulated anion channels. These combined effects likely lead to reductions in astrocytic glutamine export in vivo and may partially explain occurrence of hyperexcitability and seizures in human hyponatremia. 相似文献
132.
Cypermethrin and crude extracts of Solanum xanthocarpum were both observed for their larvicidal activity against Culex quinquefasciatus. Petroleum ether extract with lethal concentration (LC)50 and LC90 of 41.28 and 111.16 p.p.m. after 24 h and LC50 38.48 and LC90 80.83 p.p.m. after 48 h, respectively, was found to be the most effective, followed by carbon tetrachloride and methanol extracts. LC50 and LC90 for cypermethrin were 0.0027 and 0.0097 p.p.m. after 24 h and 0.0013 and 0.0092 p.p.m. after 48 h of exposure, respectively. Combined formulations were evaluated for synergistic activity and a 1:1 ratio of cypermethrin and petroleum ether extract was observed to be more effective than 1:2 and 1:4 ratios. Combinations of S. xanthocarpum extracts and cypermethrin demonstrated higher larvicidal activity, indicating synergistic activity. These results demonstrate the need for further studies on the effectiveness and toxicity to humans and animals, particularly aquatic forms. 相似文献
133.
134.
135.
Malik-Kale P Raphael BH Parker CT Joens LA Klena JD Quiñones B Keech AM Konkel ME 《Applied and environmental microbiology》2007,73(10):3123-3136
136.
Li W Tonelli J Kishore P Owen R Goodman E Scherer PE Hawkins M 《American journal of physiology. Endocrinology and metabolism》2007,292(5):E1301-E1307
Circulating adiponectin levels are increased by the thiazolidinedione (TZD) class of PPARgamma agonists in concert with their insulin-sensitizing effects. Two receptors for adiponectin (AdipoR1 and AdipoR2) are widely expressed in many tissues, but their physiological significance to human insulin resistance remains to be fully elucidated. We examined the expression patterns of AdipoR1 and AdipoR2 in fat and skeletal muscle of human subjects, their relationship to insulin action, and whether they are regulated by TZDs. Expression patterns of both AdipoRs were similar in subcutaneous and omental fat depots, with higher expression in adipocytes than in stromal cells and macrophages. To determine the effects of TZDs on AdipoR expression, subcutaneous fat and quadriceps muscle were biopsied in 14 insulin-resistant subjects with type 2 diabetes mellitus after 45 mg pioglitazone or placebo for 21 days. This duration of pioglitazone improved insulin's suppression of glucose production by 41% and enhanced stimulation of glucose uptake by 27% in concert with increased gene expression and plasma levels of adiponectin. Pioglitazone did not affect AdipoR expression in muscle, whole fat, or cellular adipose fractions, and receptor expression did not correlate with baseline or TZD-enhanced insulin action. In summary, both adiponectin receptors are expressed in cellular fractions of human fat, particularly adipocytes. TZD administration for sufficient duration to improve insulin action and increase adiponectin levels did not affect expression of AdipoR1 or AdipoR2. Although TZDs probably exert many of their effects via adiponectin, changes in these receptors do not appear to be necessary for their insulin-sensitizing effects. 相似文献
137.
The effect of elevated carbon dioxide concentration on the changes in the biomass, photosynthesis and nutrient composition
was investigated in two leafy vegetables. Spinach (Spinacia oleracea L.) and fenugreek (Trigonella foenum-graecum L.) plants were grown in open top chambers under either ambient (ACO2, 350 ± 50 μmol mol−1) or elevated (ECO2, 600 ± 50 μmol mol−1) CO2 concentration and analyzed 40, 60 and 80 days after exposure. The plants grown in ECO2 had higher net photosynthetic rate and lower stomatal conductance when compared with the plants grown in ACO2. ECO2 also changed the nutrient composition: a lower N, Mg and Fe contents and higher C and Ca contents were observed in the leaves
of plants exposed to ECO2 than in those grown at ACO2. 相似文献
138.
Characterization of Genetically Matched Isolates of Campylobacter jejuni Reveals that Mutations in Genes Involved in Flagellar Biosynthesis Alter the Organism's Virulence Potential 下载免费PDF全文
139.
Type 1 diabetic (T1D) patients are hyperglycemic and also show elevated blood levels of ketone bodies, particularly acetoacetate (AA) and β-hydroxybutyrate (BHB). T1D patients have a greater risk of developing endothelial dysfunction and cardiovascular disease (CVD). Supplementation with cysteine-rich milk proteins has been shown to be beneficial in improving various biomarkers of endothelial dysfunction and CVD. This study examines whether l-cysteine (LC) per se prevents monocyte adhesion to endothelial cells, a critical step in endothelial dysfunction. Human umbilical vein endothelial cells and THP-1 monocytes were pretreated with and without LC (500 μM) for 2 h and then exposed to ketones (AA or BHB, 0–4 mM) and/or high glucose (HG) (25 mM) for 24 h. This study shows that LC reduces HG and ketone-induced ROS production, ICAM-1 expression, and the adhesion of monocytes to endothelial cells. This study provides a biochemical mechanism by which milk protein supplementation can be beneficial in preventing the excess endothelial dysfunction and CVD seen in diabetic patients. 相似文献
140.