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   246篇
  免费   8篇
  254篇
  2023年   1篇
  2022年   2篇
  2021年   8篇
  2020年   3篇
  2019年   6篇
  2018年   3篇
  2017年   5篇
  2016年   13篇
  2015年   12篇
  2014年   12篇
  2013年   24篇
  2012年   13篇
  2011年   19篇
  2010年   12篇
  2009年   8篇
  2008年   13篇
  2007年   15篇
  2006年   16篇
  2005年   19篇
  2004年   10篇
  2003年   7篇
  2002年   11篇
  2001年   4篇
  2000年   1篇
  1999年   2篇
  1998年   2篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1993年   5篇
  1992年   3篇
  1982年   1篇
  1981年   1篇
排序方式: 共有254条查询结果,搜索用时 0 毫秒
81.
In two surveys conducted from March 1999 to March 2001 and from January 2004 to December 2006, a total of 3,950 ticks (belonging to ten different species) were collected from seven domestic and wild animals (goat, sheep, cattle, dog, fox, hare, and mouflon) from different localities throughout Cyprus. In order to establish their infection rate with Spotted Fever Rickettsiae (SFG), ticks were pooled and tested by polymerase chain reaction targeting gltA and ompA genes, followed by sequencing analysis. When tick pools tested positive, individual ticks were then tested one by one, and of the 3,950 ticks screened, rickettsial DNA was identified in 315 ticks (infection rate, 8%). Five SFG Rickettsiae were identified: Rickettsia aeschlimannii in Hyalomma marginatum marginatum, Rickettsia massiliae in Rhipicephalus turanicus and Rhipicephalus sanguineus, Rickettsia sibirica mongolotimonae in Hyalomma anatolicum excavatum, and a Rickettsia endosymbiont of Haemaphysalis sulcata (later described as Rickettsia hoogstraalii) in Haemaphysalis punctata. Two additional genes, 17 kDa and ompB, were targeted to characterize a new genotype of “Candidatus Rickettsia barbariae” genotype in R. turanicus, designated here as “Candidatus Rickettsia barbariae” Cretocypriensis. These results confirm the presence of a spectrum of SFG Rickettsiae on the island. Further studies are necessary to gain better knowledge on the epidemiology of SFG Rickettsiae in Cyprus.  相似文献   
82.
When in the vicinity of astrocytes, brain capillary endothelial cells (BCECs) develop the characteristic structural and functional features of the blood-brain barrier (BBB). The latter has low cellular permeability and restricts various compounds from entering the brain. We recently reported that the cytoskeleton-related proteins actin, gelsolin and filamin-A undergo the largest quantitative changes in bovine BCECs after re-induction of BBB functions by co-culture with glial cells. In the present study, we used an in-depth, proteomic approach to quantitatively compare differences in Triton-X-100-solubilized proteins from bovine BCECs with limited or re-induced BBB functions (i.e. cultured in the absence or presence of glial cells, respectively). The 81 protein spots of differing abundance were linked to 55 distinct genes. According to the Protein ANalysis THrough Evolutionary Relationships classification system and an Ingenuity Pathway Analysis, these quantitative changes mainly affected proteins involved in (i) cell structure and motility and (ii) protein metabolism and modification. The fold-changes affecting HSPB1, moesin and ANXA5 protein levels were confirmed by western blot analysis but were not accompanied by changes in the corresponding mRNA expression levels. Our results reveal that the bovine BCECs' phenotype adaptation to variations in their environment involves the reorganization of the actin cytoskeleton.  相似文献   
83.
Passive cigarette smoking increases isoprostane formation   总被引:1,自引:0,他引:1  
Passive smoking has been demonstrated to exert a variety of deleterious effects eventually resulting in vascular damage. Isoprostanes, a reliable marker of in vivo oxidation injury, have been shown to increase in active cigarette smoking. Data for passive smoking are lacking. We were examining the isoprostane 8-epi-PGF2alpha in 12 smokers and non-smokers exposed daily to passive cigarette smoke for 12 days. Plasma samples stored at liquid nitrogen from people having been examined earlier were used. Prevalues of 8-epi-PGF2alpha are higher in cigarette smokers. Exposure to passive smoking causes a significant increase in 8-epi-PGF2alpha in non-smokers, while in smokers there is only a trendwise increase. After repeated passive smoke exposure, 8-epi-PGF2alpha in non-smokers approaches the respective values of smokers. There is a significant correlation of 8-epi-PGF2alpha to the thromboxane (plasma, serum, conversion from exogenous precursor, 11-dehydro-TXB2) parameters (MDA, HHT- conversion) examined in these patients before. The findings document a significant temporary increase in in vivo oxidation injury due to passive smoke favouring development and/or progression of vascular disease.  相似文献   
84.
The timing of migration is generally considered of utmost importance for reproduction and survival, and timing is furthermore considered to be under strong genetic control. The individual timing of migration is presumably a result of a combination of genetic, phenotypic and environmental factors as well as some degree of randomness. However, potential differences in consistency of timing between spring and autumn and between migration strategies are not well studied. Using long‐term Danish ringing data, we study such differences by correlating date of ringing with date of recaptures for a suite of common migrating passerines in Denmark. We found that individuals marked early in one year tended to be recaptured early in the same season in a following year indicating that individuals time their migration in spring or autumn similarly between years. The relationship between spring and autumn migration was overall slightly negative, suggesting that birds arriving early in spring tended to depart late in autumn and vice versa. There were only weak effects of geographical location on timing, suggesting that the patterns found are not primarily caused by different populations being involved. Knowledge of individual consistency in migration timing is needed for understanding changes in migration timing. The consistent patterns of repeatabilities within and between seasons found here highlight the importance of timing of migration in songbirds.  相似文献   
85.
Inhibitors of proteasomes have been shown to affect endocytosis of multiple membrane receptors, in particular at the step of cargo sorting for lysosomal degradation. Here we demonstrate that the inhibition of proteasomes causes specific redistribution of an endosomal adaptor APPL1, which undergoes initial solubilization from APPL endosomes followed by clustering in the perinuclear region. MG132 treatment decreases APPL1 labeling of endosomes while the staining of the canonical early endosomes with EEA1 remains unaffected. Upon prolonged treatment with proteasome inhibitors, endogenous APPL1 localizes to the site of aggresome formation, with perinuclear APPL1 clusters encapsulated within a vimentin cage and co-localizing with aggregates positive for ubiquitin. The clustering of APPL1 is concomitant with increased ubiquitination and decreased solubility of this protein. We determined that the ubiquitin ligase Nedd4 enhances polyubiquitination of APPL1, and the ubiquitin molecules attached to APPL1 are linked through lysine-63. Taken together, these results add APPL1 to only a handful of endogenous cellular proteins known to be recruited to aggresomes induced by proteasomal stress. Moreover, our studies suggest that the proteasome inhibitors that are already in clinical use affect the localization, ubiquitination and solubility of APPL1.  相似文献   
86.
Fras1 is a putative extracellular matrix protein that has been implicated in the structural adhesion of embryonic epidermis to dermis. Moreover, mutations in Fras1/FRAS1 have been associated with the mouse blebbed phenotype and the human rare genetic disorder Fraser syndrome, respectively. Here we report the mapping of Fras1 within the extracellular space and evaluate the effects of Fras1 deficiency on lung development in the mouse. Expression of Fras1 was detected in the mesothelial cells of the visceral pleura and in the conducting airway epithelia. Immunogold histochemistry identified Fras1 as a component of the extracellular matrix localized below the lamina densa of epithelial basement membranes in the embryonic lung. Embryos homozygous for a targeted mutation of Fras1 exhibited fused pulmonary lobes resulting from incomplete separation during development as well as a profound disarrangement of blood capillaries in the terminal air sacs. We demonstrate that loss of Fras1 causes alterations in the molecular composition of basement membranes, concomitant with local disruptions of epithelial-endothelial contacts and extravasation of erythrocytes into the embryonic respiratory lumen. Thus, our findings identify Fras1 as an important structural component of the sub-lamina densa of basement membranes required for lobar septation and the organization of blood capillaries in the peripheral lung.  相似文献   
87.
An oceanic whitetip shark (Carcharhinus longimanus) was observed off the coast of Kona, Hawaii, with scars caused by the tentacles of a large cephalopod. While the exact species could not be confirmed, candidate species include the giant squid (Architeuthis dux) or species from the genera Thysanoteuthis (flying squids) and Megalocranchia (glass squids). Telemetry shows C. longimanus will dive within the mesopelagic zone and may interact with or even forage for large cephalopods.  相似文献   
88.

Background

During adolescence children are usually confronted with an expanding social arena. Apart from families, schools and neighbourhoods, peers, classmates, teachers, and other adult figures gain increasing importance for adolescent socio-emotional adjustment. The aim of the present study was to investigate the extent to which Greek adolescents’ perceived well-being in three main social contexts (family, school and peers) predicted self-reported Subjective Health Complaints.

Methods

Questionnaires were administered to a Greek nation-wide, random, school-based sample of children aged 12–18 years in 2003. Data from 1.087 adolescents were analyzed. A hierarchical regression model with Subjective Health Complaints as the outcome variable was employed in order to i) control for the effects of previously well-established demographic factors (sex, age and subjective economic status) and ii) to identify the unique proportion of variance attributed to each context. Bivariate correlations and multicollinearity were also explored.

Results

As hypothesized, adolescents’ perceived well-being in each of the three social contexts appeared to hold unique proportions of variance in self-reported Subjective Health Complaints, after controlling for the effects of sex, age and subjective economic status. In addition, our final model confirmed that the explained variance in SHC was accumulated from each social context studied. The regression models were statistically significant and explained a total of approximately 24% of the variance in Subjective Health Complaints.

Conclusions

Our study delineated the unique and cumulative contributions of adolescents’ perceived well-being in the family, school and peer setting in the explanation of Subjective Health Complaints. Apart from families, schools, teachers and peers appear to have a salient role in adolescent psychosomatic adjustment. A thorough understanding of the relationship between adolescents’ Subjective Health Complaints and perceived well-being in their social contexts could not only lead to more effective tailored initiatives, but also to promote a multi- and inter-disciplinary culture in adolescent psychosomatic health.
  相似文献   
89.
Understanding the structure of interphase chromosomes is essential to elucidate regulatory mechanisms of gene expression. During recent years, high-throughput DNA sequencing expanded the power of chromosome conformation capture (3C) methods that provide information about reciprocal spatial proximity of chromosomal loci. Since 2012, it is known that entire chromatin in interphase chromosomes is organized into regions with strongly increased frequency of internal contacts. These regions, with the average size of ∼1 Mb, were named topological domains. More recent studies demonstrated presence of unconstrained supercoiling in interphase chromosomes. Using Brownian dynamics simulations, we show here that by including supercoiling into models of topological domains one can reproduce and thus provide possible explanations of several experimentally observed characteristics of interphase chromosomes, such as their complex contact maps.  相似文献   
90.

Background

Few studies have differentiated between weekday and weekend day sleep duration in their association with indicators of weight status in children. Therefore, we examined the association of week and weekend day sleep duration with indicators of body composition in 10–12 year old European school children.

Methods and Findings

Multi-level linear regression analysis was performed to examine the association between parent-reported week and weekend day sleep duration and objectively assessed child BMI and WC, adjusting for socio-demographic variables and energy balanced related behaviours EBRBs (i.e. dietary, physical and sedentary behaviour). Compared to sleeping 10 hrs/night or more, sleeping on average less than 10 hrs/night during weekdays was associated with higher BMI (for example, B = 0.86 and CI = [0.27;1.45] when sleeping ≤7 hrs) and WC (for example, B = 1.99 and CI = [0.32;3.65] when sleeping ≤7 hrs). Sleeping 9 hrs/night during weekend days, but not ≤8 hrs, was associated with higher WC (B = 0.66; CI = [0.04;1.28]) compared to sleeping more than 10 hrs/night. Average (week and weekend) sleep duration less than 10 hrs/night was associated with higher values for BMI (B = 0.98; CI = [0.24;1.73] and WC (B = 2.35; CI = [0.08;4.31]).

Conclusions

Weekday sleep duration seems more strongly associated with body composition in European school children than weekend day sleep duration. Promoting adequate sleep duration may contribute to healthy weight in children.  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