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   190篇
  免费   14篇
  2023年   2篇
  2022年   5篇
  2021年   7篇
  2019年   5篇
  2018年   3篇
  2017年   4篇
  2016年   11篇
  2015年   13篇
  2014年   12篇
  2013年   12篇
  2012年   21篇
  2011年   24篇
  2010年   4篇
  2009年   11篇
  2008年   14篇
  2007年   16篇
  2006年   8篇
  2005年   7篇
  2004年   11篇
  2003年   6篇
  2002年   2篇
  2001年   1篇
  1999年   1篇
  1998年   2篇
  1996年   1篇
  1994年   1篇
排序方式: 共有204条查询结果,搜索用时 546 毫秒
121.
122.
Here we present evidence of phytoliths preserved in carbonised food deposits on prehistoric pottery from the western Baltic dating from 6,100 cal BP to 5750 cal BP. Based on comparisons to over 120 European and Asian species, our observations are consistent with phytolith morphologies observed in modern garlic mustard seed (Alliaria petiolata (M. Bieb) Cavara & Grande). As this seed has a strong flavour, little nutritional value, and the phytoliths are found in pots along with terrestrial and marine animal residues, these findings are the first direct evidence for the spicing of food in European prehistoric cuisine. Our evidence suggests a much greater antiquity to the spicing of foods than is evident from the macrofossil record, and challenges the view that plants were exploited by hunter-gatherers and early agriculturalists solely for energy requirements, rather than taste.  相似文献   
123.
124.
Autosomal recessive cutis laxa (ARCL) syndromes are phenotypically overlapping, but genetically heterogeneous disorders. Mutations in the ATP6V0A2 gene were found to underlie both, autosomal recessive cutis laxa type 2 (ARCL2), Debré type, and wrinkly skin syndrome (WSS). The ATP6V0A2 gene encodes the a2 subunit of the V-type H+-ATPase, playing a role in proton translocation, and possibly also in membrane fusion. Here, we describe a highly variable phenotype in 13 patients with ARCL2, including the oldest affected individual described so far, who showed strikingly progressive dysmorphic features and heterotopic calcifications. In these individuals we identified 17 ATP6V0A2 mutations, 14 of which are novel. Furthermore, we demonstrate a localization of ATP6V0A2 at the Golgi-apparatus and a loss of the mutated ATP6V0A2 protein in patients’ dermal fibroblasts. Investigation of brefeldin A-induced Golgi collapse in dermal fibroblasts as well as in HeLa cells deficient for ATP6V0A2 revealed a delay, which was absent in cells deficient for the ARCL-associated proteins GORAB or PYCR1. Furthermore, fibroblasts from patients with ATP6V0A2 mutations displayed elevated TGF-β signalling and increased TGF-β1 levels in the supernatant. Our current findings expand the genetic and phenotypic spectrum and suggest that, besides the known glycosylation defect, alterations in trafficking and signalling processes are potential key events in the pathogenesis of ATP6V0A2-related ARCL.  相似文献   
125.
Honeybees secrete 2-heptanone (2-H) from their mandibular glands when they bite. Researchers have identified several possible functions: 2-H could act as an alarm pheromone to recruit guards and soldiers, it could act as a chemical marker, or it could have some other function. The actual role of 2-H in honeybee behaviour remains unresolved. In this study, we show that 2-H acts as an anaesthetic in small arthropods, such as wax moth larva (WML) and Varroa mites, which are paralysed after a honeybee bite. We demonstrated that honeybee mandibles can penetrate the cuticle of WML, introducing less than one nanolitre of 2-H into the WML open circulatory system and causing instantaneous anaesthetization that lasts for a few minutes. The first indication that 2-H acts as a local anaesthetic was that its effect on larval response, inhibition and recovery is very similar to that of lidocaine. We compared the inhibitory effects of 2-H and lidocaine on voltage-gated sodium channels. Although both compounds blocked the hNav1.6 and hNav1.2 channels, lidocaine was slightly more effective, 2.82 times, on hNav.6. In contrast, when the two compounds were tested using an ex vivo preparation–the isolated rat sciatic nerve–the function of the two compounds was so similar that we were able to definitively classify 2-H as a local anaesthetic. Using the same method, we showed that 2-H has the fastest inhibitory effect of all alkyl-ketones tested, including the isomers 3- and 4-heptanone. This suggests that natural selection may have favoured 2-H over other, similar compounds because of the associated fitness advantages it confers. Our results reveal a previously unknown role of 2-H in honeybee defensive behaviour and due to its minor neurotoxicity show potential for developing a new local anaesthetic from a natural product, which could be used in human and veterinary medicine.  相似文献   
126.

Background

Detection of urinary cytokines in pauci-immune focal segmental necrotizing glomerulonephritis (FSNGN) may provide valuable information about disease pathogenesis and prognosis.

Methods

Epidermal growth factor (EGF), transforming growth factor (TGF-β1) and vascular endothelial growth factor (VEGF) were measured by ELISA, and Interleukins, monocyte chemotactic protein-1 (MCP-1), macrophage inflammatory protein (MIP1β) by a multiplex cytokine assay, in 38 patients with FSNGN. Their levels were correlated with severity of histological findings and renal function outcome in short and long term.

Results

The percentage of crescents in renal biopsy had positive correlation with TGF-β1 (p = 0.004) and IL-15 urinary excretion (p = 0.01), and negative correlation with EGF (p = 0.01). Increased urinary excretion of IL-6, IL-15, VEGF and MIP-1β was associated with poor renal function outcome, but increased levels of EGF, IL-2 and IL-9 predicted a favourable prognosis. In multiple regression analysis IL-6 and VEGF urinary levels were independent predictors of no-response at the acute phase (p = 0.001 and p < 0.0001, respectively), while, IL-6 was the only factor (p = 0.03) predicted worse outcome at the end of follow-up (39.4 ± 45 months).

Conclusion

Increased urinary excretion of IL-6, IL-15, VEGF, TGF-β1, MCP-1 and MIP-1β and reduced EGF, IL-2, IL-9 may be associated with histological damage and influence response to treatment in pauci-immune FSNGN.  相似文献   
127.
Plyometric training in children, including different types of jumps, has become common practice during the last few years in different sports, although there is limited information about the adaptability of children with respect to different loads and the differences in performance between various jump types. The purpose of this study was to examine the effect of gender and training background on the optimal drop jump height of 9- to 11-year-old children. Sixty prepubertal (untrained and track and field athletes, boys and girls, equally distributed in each group [n = 15]), performed the following in random order: 3 squat jumps, 3 countermovement jumps (CMJs) and 3 drop jumps from heights of 10, 20, 30, 40, and 50 cm. The trial with the best performance in jump height of each test was used for further analysis. The jump type significantly affected the jump height. The jump height during the CMJ was the highest among all other jump types, resulting in advanced performance for both trained and untrained prepubertal boys and girls. However, increasing the dropping height did not change the jumping height or contact time during the drop jump. This possibly indicates an inability of prepubertal children to use their stored elastic energy to increase jumping height during drop jumps, irrespective of their gender or training status. This indicates that children, independent of gender and training status, have no performance gain during drop jumps from heights up to 50 cm, and therefore, it is recommended that only low drop jump heights be included in plyometric training to limit the probability of sustaining injuries.  相似文献   
128.
129.
The fresh needles of 46 pine species, including 37 and 17 taxa of the subgenera Pinus and Strobus, respectively, were subjected to hydrodistillation and the essential oils obtained were analyzed by means of GC–FID and GC–MS. The comprehensive analyses of the needle oils, which allowed for the identification of 161 constituents comprising the majority of the volatiles, showed significant, not only quantitative, but also qualitative differences between the samples. Monoterpenes, sesquiterpenes and diterpenes dominated the pine foliage oils, with the presence of the monoterpene hydrocarbons α- and β-pinene and the sesquiterpene hydrocarbon germacrene D characterizing most of the oils. This is the first report on the chemical composition of the essential oils of 21 pine taxa, including 15 taxa of subgenus Pinus and 6 taxa of subgenus Strobus.  相似文献   
130.
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