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   44篇
  免费   4篇
  48篇
  2016年   6篇
  2015年   3篇
  2013年   5篇
  2012年   1篇
  2011年   1篇
  2010年   4篇
  2009年   1篇
  2008年   5篇
  2007年   4篇
  2006年   4篇
  2005年   2篇
  2004年   2篇
  2003年   1篇
  2002年   1篇
  1997年   1篇
  1996年   1篇
  1991年   2篇
  1988年   1篇
  1986年   1篇
  1985年   1篇
  1983年   1篇
排序方式: 共有48条查询结果,搜索用时 0 毫秒
1.
2.
Abstract. Woodland colonization on wetlands is considered to have a detrimental effect on their ecological value, even though detailed analysis of this process is lacking. This paper provides an evaluation of the ecological changes resulting from succession of poor fen (base‐poor mire) to willow wet woodland on Goss Moor NNR in Cornwall, UK. Different ages of willow carr were associated with eight understorey communities. During willow colonization, in the ground flora, there was a progressive decrease in poor fen species and an associated increase in woodland species, which appeared to be related to an increase in canopy cover and therefore shade. The most diverse community was found to be the most recent willow and was dominated by poor fen species. The oldest willow was the second most diverse and was associated with a reduction in poor fen species and an increase in woodland species. Architectural features were used successfully to assess the general condition and structure of willow. Tree height and DBH were identified as useful parameters to accurately assess willow age in the field. The implications of active intervention to remove willow in order to conserve the full range of communities within the hydrosere are discussed.  相似文献   
3.

Background  

Parkinson's disease (PD) is the second most common neurodegenerative disorder. As there is no definitive diagnostic test, its diagnosis is based on clinical criteria. Recently transcranial duplex scanning (TCD) of the substantia nigra in the brainstem has been proposed as an instrument to diagnose PD. We and others have found that TCD scanning of substantia nigra duplex is a relatively accurate diagnostic instrument in patients with parkinsonian symptoms. However, all studies on TCD so far have involved well-defined, later-stage PD patients, which will obviously lead to an overestimate of the diagnostic accuracy of TCD.  相似文献   
4.
5.

Introduction

Pre-exposure prophylaxis (PrEP) is an effective tool to reduce HIV transmission. The primary objective of this study was to assess awareness of PrEP by individuals living with HIV (HIV+) and acceptance of its use for their HIV negative (HIV-) partners.

Methods

A cross sectional survey was conducted among individuals living with HIV who received care at an urban HIV clinic between January 2013 and June 2013. The survey examined knowledge, attitudes, and acceptability of PrEP, and perception of transmission risk of HIV. Chi-Square test and Fisher''s Exact test were used to compare proportions.

Results

Among 206 subjects living with HIV, 15.3% (32) had heard of PrEP. Men who have sex with men (MSM) were more likely to be aware of PrEP than all others (p = 0.003). Once educated about PrEP those who believed PrEP would reduce their partner’s risk for HIV were more likely to recommend PrEP to their partner (p<0.001). 92% of all respondents said they would be “extremely likely/likely” to discuss PrEP use with their provider. Of 159 subjects whose main partner was HIV-, MSM (p = 0.007), male participants (p = 0.044), and those who were consistently taking meds (p = 0.049) were more likely to be aware of PrEP. Those who perceived they were at risk of transmitting HIV (p<0.001) and those who were consistently taking meds (0.049) were more likely to agree that PrEP could reduce the risk of HIV to their partners.

Conclusion

This study illustrates a low awareness of PrEP but once educated the willingness of a cohort of individuals living with HIV to recommend PrEP to their partners. Our findings demonstrate the importance of providers informing their patients living with HIV about PrEP, as these persons are an underutilized link to support the uptake of PrEP by their HIV- partners.  相似文献   
6.
Berkowski, B & Klug, C. 2011: Lucky rugose corals on crinoid stems: unusual examples of subepidermal epizoans from the Devonian of Morocco. Lethaia, Vol. 45, pp. 24–33. In the fossil record, evidence for true epizoans, i.e. living animals inhabiting other living host‐animals, is rather rare. A host reaction is usually needed to proof the syn vivo‐settling of the epizoan. Herein, we provide a first report of such an epizoan biocoenosis from various strata of the Early Devonian of Hamar Laghdad, the world‐renowned Moroccan mud‐mound locality. In this case, solitary rugose corals settled as larvae on crinoid stems, perhaps at a spot where the epidermis was missing for some reason (injury, disease). Both the crinoid and the coral began to grow around each other. By doing so, the affected crinoid columnals formed a swelling, where ultimately only an opening slightly larger than the coral orifice remained. We discuss both macroecological and small‐scale synecological aspects of this biocoenosis. The coral profited from its elevated home because it reached into more rapid currents providing the polyp with more food than at the densely populated seafloor, which was probably covered by a coral‐meadow around the mounds and hydrothermal vents. □Corals, crinoids, Early Devonian, epizoans, Morocco, Rugosa.  相似文献   
7.
Techniques in neuroimaging such as functional magnetic resonance imaging (fMRI) have helped to provide insights into the role of supraspinal mechanisms in pain perception. This review focuses on studies that have applied fMRI in an attempt to gain a better understanding of the mechanisms involved in the processing of pain associated with fibromyalgia. This article provides an overview of the nociceptive system as it functions normally, reviews functional brain imaging methods, and integrates the existing literature utilizing fMRI to study central pain mechanisms in fibromyalgia.  相似文献   
8.
A rich assemblage of exceptionally preserved marine and terrestrial fossils occurs in fine‐grained limestones in the upper part of the Late Tithonian (Middle Volgian) shallowing upward carbonate sequence in Central Poland. The richest horizon, a deposit known locally as the Corbulomima horizon, is named after the shallow burrowing suspension feeding bivalve Corbulomima obscura, moulds of which occur in densities of up to 500 per square metre on some bedding planes. The fauna in this bed also includes organic and phosphatic remains of a wide range of other creatures including the exuviae of limulids and decapods, disarticulated fish skeletons and rare isolated pterosaur bones and teeth. There are also perfectly preserved dragonfly wings and beetle exoskeletons. The average stable carbon and oxygen isotope values for ostracod shells and fine‐grained sediment from this horizon suggest precipitation of the calcium carbonate from warm seawater of normal marine salinity. The carbonate sediments overlying the fossiliferous horizon have been interpreted as nearshore to shoreface facies. These pass abruptly into coarse reworked intraclastic sediments interpreted as possible tsunami or storm surge over‐wash deposits. The clasts in this deposit have more positive oxygen isotope values than those in the underlying limestone, which may indicate that they were lithified in a slightly more evaporative, perhaps intertidal, setting. The succession terminates with silicified fine‐grained limestones likely to have formed in extremely shallow lagoonal environments. In contrast with the Solnhofen limestones of Lower Tithonian age in south‐central Germany the Corbulomima horizon is interpreted as a transitional deposit formed in a shallow marine setting by rapid burial with elements of both Konservat‐ and Konzentrat‐Lagerstätte preservation. □Konzentrat and Konservat‐Lagerstätte, Taphonomy, Palaeoenvironment, Paleogeography, Late Jurassic, Poland.  相似文献   
9.
10.

Background  

Parkinson's disease (PD) is the second most common neurodegenerative disorder. One of the most widely used techniques to diagnose PD is a Single Photon Emission Computer Tomography (SPECT) scan to visualise the integrity of the dopaminergic pathways in the brain. Despite this there remains some discussion on the value of SPECT in the differential diagnosis of PD. We did a meta-analysis of all the existing literature on the diagnostic accuracy of both pre- and post-synaptic SPECT imaging in the differential diagnosis of PD.  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