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   84篇
  免费   7篇
  91篇
  2022年   2篇
  2020年   1篇
  2019年   1篇
  2017年   3篇
  2016年   1篇
  2015年   3篇
  2014年   1篇
  2013年   3篇
  2012年   6篇
  2011年   3篇
  2010年   7篇
  2009年   7篇
  2008年   3篇
  2007年   4篇
  2006年   8篇
  2005年   4篇
  2004年   5篇
  2003年   1篇
  2002年   1篇
  2001年   4篇
  2000年   3篇
  1999年   4篇
  1998年   1篇
  1997年   1篇
  1996年   5篇
  1990年   1篇
  1988年   1篇
  1986年   1篇
  1983年   1篇
  1979年   1篇
  1978年   2篇
  1972年   1篇
  1966年   1篇
排序方式: 共有91条查询结果,搜索用时 15 毫秒
71.
Zea systematics: ribosomal ITS evidence   总被引:10,自引:0,他引:10  
Ribosomal internal transcribed spacer (ITS) sequences were used to evaluate the phylogenetics of Zea and Tripsacum. Maximum likelihood and polymorphism parsimony were used for phylogenetic reconstructions. Zea ITS nucleotide diversity was high compared to other plant species, but approximately equivalent to other maize loci. Coalescence of ITS alleles was rapid relative to other nuclear loci; however, there was still much diversity within populations. Zea and Tripsacum form a clade clearly differentiated from all other Poaceae. Four Zea ITS pseudogenes were identified by phylogenetic position and nucleotide composition. The phylogenetic position of Z. mays ssp. huehuetenangensis was clearly established as basal to the other Z. mays. The ITS phylogeny disfavored a Z. luxurians and Z. diploperennis clade, which conflicted with some previous studies. The introgression of Z. mays alleles into Z. perennis and Z. diploperennis was also established. The ITS data indicated a near contemporary divergence of domesticated maize and its two closest wild relatives.   相似文献   
72.
73.
74.
75.
The inoculation of the roots of resistant (BSTN) and susceptible (JHL) cultivars of date palm seedlings byFusarium oxysporum f. sp.albedinis (Foa) induces an increase in activity of phenylalanine ammonia-lyase (E.C. 4. 3. 1. 5., PAL). The post-infectional response in the PAL activity in the resistant cultivar roots was faster and higher than that in the susceptible cultivar. However, the elicitation of the seedlings by the hyphal wall preparation (HWP) ofFoa induces an identical PAL response in the resistant and the susceptible cultivars. The elicitor activity of HWP was dose-dependent, the optimal concentration which induces a maximum PAL activity was 10 mg of mycelium per mL. The elicitor present in the HWP was thermostable since its elicitor activity was maintained after heat treatment (121 °C for 45 min). The treatment of the HWP with protease (Pronase E) does not have an effect on the HWP elicitor activity. However, the treatment of the HWP with sodium periodate inhibits its elicitor activity. This data suggests that the HWP elicitor is a carbohydrate compound. In addition, the HWP elicitor is non-specific since it induces identical responses of the PAL activity in two cultivars showing different behaviors to the pathogen. The absence of specificity of HWP elicitors and the differential response of the PAL activity to the infection byFoa and to the elicitation by the HWP are discussed. An explanation of the general interactions between plant and parasite is proposed.  相似文献   
76.
Rhipicephalus sanguineus Latreille (1806) (Ixodida: Ixodidae) is considered to be the most widely distributed tick and to have a vast range of habitats and hosts, including livestock, pets and wildlife. In addition to morphological differences, recent investigations using approaches based on molecular genetic markers have revealed the existence of different R. sanguineus lineages in different geographic regions. In this study, 475 ticks collected from dogs in the western Iberian peninsula were studied both morphologically and genetically, using 12S and 16S rDNA and COI gene markers in order to clarify the controversy over the systematic status of R. sanguineus sensu lato in Western Europe, and to compare the present data with those sourced from studies conducted in other regions of the world. Despite the high morphometric variability, particularly on spiracles in both genders and in female genitalia, data obtained with different genetic molecular markers show very low variability, suggesting the existence of a unique species. In addition, the phylogenetic analysis showed genetic uniformity, supporting the existence of a well‐defined clade consisting of R. sanguineus s.l. specimens from Western Europe that are distinct from R. sanguineus s.l. from Africa. Furthermore, these data corroborate the existence of a polymorphic species in Western Europe, which requires to be consensually redescribed in view of its medical and veterinary importance in pathogen transmission.  相似文献   
77.
78.
79.
ABSTRACT: BACKGROUND: Given the current lack of disease-modifying therapies, it is important to explore new models of longitudinal care for older adults with dementia that focus on improving quality of life and delaying functional decline. In a previous clinical trial, we demonstrated that collaborative care for Alzheimer's disease reduces patients' neuropsychiatric symptoms as well as caregiver stress. However, these improvements in quality of life were not associated with delays in subjects' functional decline. Trial design Parallel randomized controlled clinical trial with 1:1 allocation. Participants A total of 180 community-dwelling patients aged [greater than or equal to]45 years who are diagnosed with possible or probable Alzheimer's disease; subjects must also have a caregiver willing to participate in the study and be willing to accept home visits. Subjects and their caregivers are enrolled from the primary care and geriatric medicine practices of an urban public health system serving Indianapolis, Indiana, USA. Interventions All patients receive best practices primary care including collaborative care by a dementia care manager over two years; this best practices primary care program represents the local adaptation and implementation of our prior collaborative care intervention in the urban public health system. Intervention patients also receive in-home occupational therapy delivered in twenty-four sessions over two years in addition to best practices primary care. The focus of the occupational therapy intervention is delaying functional decline and helping both subjects and caregivers adapt to functional impairments. The in-home sessions are tailored to the specific needs and goals of each patient-caregiver dyad; these needs are expected to change over the course of the study.Objective To determine whether best practices primary care plus home-based occupational therapy delays functional decline among patients with Alzheimer's disease compared to subjects treated in the control group. Outcomes The primary outcome is the Alzheimer's Disease Cooperative Studies Group Activities of Daily Living Scale; secondary outcome measures are two performance-based measures including the Short Physical Performance Battery and Short Portable Sarcopenia Measure. Outcome assessments for both the caregiver-reported scale and subjects' physical performance scales are completed in the subject's home. Randomization Eligible patient-care giver dyads will be stratified by clinic type and block randomized with a computer developed randomization scheme using a 1:1 allocation ratio. Blinding Single blinded. Research assistants completing the outcome assessments were blinded to the subjects' treatment group. Trial status Ongoing ClinicalTrial.Gov identifier NCT01314950; date of completed registration 10 March 2011; date first patient randomized 9 March 2011.  相似文献   
80.
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