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   235篇
  免费   29篇
  2022年   2篇
  2021年   4篇
  2020年   5篇
  2019年   6篇
  2018年   6篇
  2017年   4篇
  2016年   13篇
  2015年   9篇
  2014年   11篇
  2013年   14篇
  2012年   12篇
  2011年   15篇
  2010年   9篇
  2009年   10篇
  2008年   7篇
  2007年   5篇
  2006年   9篇
  2005年   7篇
  2004年   9篇
  2003年   9篇
  2002年   7篇
  2001年   3篇
  2000年   4篇
  1998年   2篇
  1996年   2篇
  1995年   2篇
  1990年   3篇
  1989年   4篇
  1988年   2篇
  1987年   8篇
  1985年   3篇
  1984年   5篇
  1983年   5篇
  1982年   5篇
  1981年   6篇
  1980年   2篇
  1979年   6篇
  1978年   4篇
  1977年   5篇
  1976年   2篇
  1974年   2篇
  1973年   1篇
  1969年   1篇
  1962年   1篇
  1961年   4篇
  1959年   1篇
  1957年   1篇
  1956年   1篇
  1950年   1篇
  1931年   1篇
排序方式: 共有264条查询结果,搜索用时 15 毫秒
241.
ABSTRACT: BACKGROUND: After diagnosis of a dementing illness patients and their spouses have many concerns related to the disease and their future. This often leads to poor psychological well-being and reduced health related quality of life (HRQoL) of the family. Support for self-management skills has been proven to be an effective method to improve prognosis of asthma, heart failure and osteoarthritis. However, self-management interventions have not been studied in dementia. Therefore, our aim was to examine in an objective-oriented group intervention the efficacy of self-management support program (SMP) on the HRQoL of dementia patients and their spousal caregivers as well as on the sense of competence and psychological well-being of care-givers. METHODS: During the years 2011-12, 160 dementia patients and their spouses will be recruited from memory clinics and randomized into two arms: 80 patients for group-based SMP sessions including topics selected by the participants, 80 patients will serve as controls in for usual community care. Sessions may include topics on dementia, community services, active lifestyle and prevention for cognitive decline, spousal relationship, future planning and emotional well-being. The patients and spouses will have their separate group sessions (10 participants/group) once a week for 8 weeks. Main outcome measures will be patients' HRQoL (15D) and spousal caregivers' HRQoL (RAND-36), and sense of competence (SCQ). Secondary measures will be caregivers' psychological well-being (GHQ-12) and coping resources, patients' depression, cognition and signs of frailty. Data concerning admissions to institutional care and the use and costs of health and social services will be collected during a two year follow-up. DISCUSSION: This is a "proof -of-concept" study to explore the efficacy of group support for self-management skills among dementia families. It will also provide data on cost-effectiveness of the intervention.  相似文献   
242.
Inter-specific differences in animal defence mechanisms against toxic substances are currently poorly understood. The ethoxyresorufin-O-deethylase (EROD) enzyme plays an important role in defence against toxic chemicals in a wide variety of animals, and it is an important biomarker for environmental contamination. We compared basal hepatic EROD activity levels among ten passerine species to see if there is inter-specific variation in enzyme activity, especially in relation to their diet and migration status. Migratory insectivores showed higher EROD activity compared to granivores. We hypothesize that the variable invertebrate diet of migratory insectivores contains a wider range of natural toxins than the narrower diet of granivores. This may have affected the evolution of mixed function oxidases (MFO) system and enzyme activities. We further tested whether metabolic rates or relative liver size were associated with the variation in detoxification capacity. We found no association between EROD activity and relative (per mass unit) basal metabolic rate (BMR). Instead, EROD activity and relative liver mass (% of body mass) correlated positively, suggesting that a proportionally large liver also functions efficiently. Our results suggest that granivores and non-migratory birds may be more vulnerable to environmental contaminants than insectivores and migratory birds. The diet and migration status, however, are phylogenetically strongly connected to each other, and their roles cannot be fully separated in our analysis with only ten passerine species.  相似文献   
243.
Oxidative stress has been suggested as a mediator in life‐history trade‐off. By spending more resources on for example reproduction an organism might sacrifice its antioxidant defence. So far, most conclusions on trade‐offs between life‐history traits and oxidative stress have been drawn from laboratory studies using a few model species and there is a need for studies conducted in natural settings. We investigated associations between markers for antioxidant status (antioxidant enzyme activities and antioxidant levels), body condition, age and reproduction in three species of wild‐living passerines. The impact from an anthropogenic stressor (metal pollution) was also assessed. The three bird species showed interspecific variation in their SOD and CAT activities, indicating different pathways to eliminate radicals. The age of females affected both antioxidant status and the breeding performance, indicating the importance of age as a factor in life‐history studies. Old birds had lower levels of antioxidants/antioxidant enzyme activities and they produced larger broods/more successful broods, though the latter might be confounded by surviving females having increased fitness. Metal exposure had a negative impact on breeding, and improved breeding outcome was also associated with increased antioxidant defence, but metal exposure was not directly related to the oxidative status of birds, emphasizing that additional stressors might independently affect the same traits. Our results highlight that caution has to be taken when generalizing and extrapolating results to even closely related species. The results support the idea that there is a cost of reproduction, in terms of increased resources spent on antioxidant defence, though this should be confirmed with experimental studies.  相似文献   
244.
DNA-based pyrosequencing analysis of the V1- V3 16S rRNA gene region was used to identify bacteria community and shift during early stages of wood colonization in boreal forest soils. The dataset comprised 142,447 sequences and was affiliated to 11 bacteria phyla, 25 classes and 233 genera. The dominant groups across all samples were Proteobacteria, followed by Bacteroidetes, Acidobacteria, Actinobacteria, Amatimonadetes, Planctomycetes and TM7 group. The community structure of the primary wood-inhabiting bacteria differed between types of forest soils and the composition of bacteria remained stable over prolonged incubation time. The results suggest that variations in soil bacterial community composition have an influence on the wood-inhabiting bacterial structure.  相似文献   
245.
Hot spots of CH4 emissions are a typical feature of pristine peatlands at the microsite and landscape scale. To determine whether rewetting and lake construction in a cutaway peatland would result in the re‐creation of hot spots, we first measured CH4 fluxes over a 2‐year period with static chambers and estimated annual emissions. Second, to assess whether rewetting and lake creation would produce hot spots at the landscape level, we hypothesized a number of alternative land use scenarios for the peatland following the cessation of peat extraction. Using the results from this study and other studies from literature, we calculated the global warming potential (GWP) of each scenario and the respective contribution of CH4. The results showed that hot spots of CH4 fluxes were observed as a consequence of microsite‐specific differences in water table (WT) position and plant productivity. CH4 fluxes were closely related to peat temperature at 10 cm depth and WT position. Annual emissions ranged from 4.3 to 38.8 g CH4 m?2 yr?1 in 2002 and 3.2 to 28.8 g CH4 m?2 yr?1 in 2003. The scenario results suggest that lake creation is likely to result in the re‐creation of a hot spot at the landscape level. However, the transition from cutaway to wetland ecosystem may lead to a reduction in the GWP of the peatland.  相似文献   
246.
247.
About two-thirds of patients with Leber hereditary optic neuroretinopathy (LHON) harbor mutations in mitochondrial DNA at positions 11778 (ND4) or 3460 (ND1). Thus, the clinical diagnosis of LHON can often be confirmed with mutation analysis. Detection of pathogenic mutations and quantification of heteroplasmy has mainly relied on PCR and restriction site analysis and densitometric scanning. We applied the recently developed solid-phase minisequencing method, based on primerguided nucleotide incorporation, to the simultaneous detection and quantitation of the ND4/11778 and ND1/3460 mutations. The method was highly sensitive, heteroplasmy as low as 1.5% being easily detected. Rapid, reproducible, and accurate results prove solid-phase minisequencing to be the method of choice for quantitative analysis of LHON mutations.  相似文献   
248.
249.
Summary The concept and role of endomitosis is reevaluated in the light of observations on three organisms. Endomitosis which morphologically agrees with Geitler's (1939) classical definition is compared in tapetal cells of the liliaceous plant Eremurus, in the septal cells of the testicular follicles of the grasshopper Melanoplus, and in human cells from normal and molar trophoblasts and cervical cancer. These observations, together with those of Kidnadze and Istomina (1980), show that functionally at least two fundamentally different types of endomitosis exist, although morphologically the stages resemble each other in the three organisms. In the first type, exemplified by Eremurus, each endomitosis leads to a chromosome constitution which represents one level higher ploidy, a course that has been assumed to be characteristic of endomitosis in general. The second type, observed in its most characteristic form in the grasshopper, seems to be stationary: no DNA synthesis occurs, but an intensive RNA synthesis takes place. Presumably such cells have reached a final state in their development and are specialized in manufacturing one or more gene products. Endomitosis in normal placenta comes near this type, although DNA synthesis takes place in occasional cells. However, similar endomitotic nuclei in the hydatiform moles are in the process of DNA synthesis. When endomitosis is analyzed in different organisms and tissues, the observation that this process is not one entity should be kept in mind.  相似文献   
250.
Ochreous sludge deposited in the course of aeration of ground water contained an assortment of bacterial forms and structures which were investigated by light microscopy, scanning electron microscopy, and transmission electron microscopy. Bacterial structures were often covered by iron deposition which could be removed by acidification of the samples. Sulfuric acid treatment was consistently better than hydrochloric acid to dissolve iron without a considerable damage to the bacterial cells. Partial dissolution of amorphous ferric iron was achieved by acidifying the samples with oxalic acid or citric acid prior to the preparation for electron microscopy.  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