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   149篇
  免费   9篇
  国内免费   2篇
  2021年   5篇
  2020年   1篇
  2019年   2篇
  2018年   3篇
  2017年   6篇
  2016年   1篇
  2015年   4篇
  2014年   7篇
  2013年   9篇
  2012年   8篇
  2011年   5篇
  2010年   13篇
  2009年   14篇
  2008年   9篇
  2007年   5篇
  2006年   6篇
  2005年   7篇
  2004年   1篇
  2003年   4篇
  2002年   2篇
  2001年   2篇
  2000年   1篇
  1999年   1篇
  1998年   6篇
  1997年   5篇
  1996年   4篇
  1995年   1篇
  1994年   2篇
  1993年   4篇
  1992年   2篇
  1991年   4篇
  1990年   1篇
  1989年   2篇
  1988年   6篇
  1987年   2篇
  1985年   1篇
  1982年   1篇
  1975年   1篇
  1969年   2篇
排序方式: 共有160条查询结果,搜索用时 265 毫秒
21.
In sub-Saharan Africa the highest overlap between malaria and HIV infections occurs in female adolescents. Yet control activities for these infections are directed to different target groups, using disparate channels. This reflects the lack of priority given to adolescents and the absence of an accepted framework for delivering health and health-related interventions to this high-risk group. In this paper it is argued that female adolescents require a continuum of care for malaria and HIV – prior to conception, during and after pregnancy and that this should be provided through adolescent services. The evidence for this conclusion is presented. A number of African countries are commencing to formulate and implement adolescent-friendly policies and services and disease control programs for malaria and HIV will need to locate their interventions within such programs to ensure widespread coverage of this important target group. Failure to prioritize adolescent health in this way will seriously limit the success of disease control programs for malaria and HIV prevention.  相似文献   
22.
The microbiota is required for optimal host development and ongoing immune homeostasis. Lactobacilli are common inhabitants of the mammalian large intestine and immunoregulatory effects have been described for certain, but not all, strains. The mechanisms underpinning these protective effects are beginning to be elucidated. One such protective organism is Lactobacillus rhamnosus JB-1 (Lb. rhamnosus JB-1). Lb. murinus has no such anti-inflammatory protective effects and was used as a comparator organism. Human monocyte-derived dendritic cells (MDDCs) were co-incubated with bacteria and analysed over time for bacterial adhesion and intracellular processing, costimulatory molecule expression, cytokine secretion and induction of lymphocyte polarization. Neutralising antibodies were utilized to identify the responsible MDDC receptors. Lb. rhamnosus JB-1 adhered to MDDCs, but internalization and intracellular processing was significantly delayed, compared to Lb. murinus which was rapidly internalized and processed. Lb. murinus induced CD80 and CD86 expression, accompanied by high levels of cytokine secretion, while Lb. rhamnosus JB-1 was a poor inducer of costimulatory molecule expression and cytokine secretion. Lb. rhamnosus JB-1 primed MDDCs induced Foxp3 expression in autologous lymphocytes, while Lb. murinus primed MDDCs induced Foxp3, T-bet and Ror-γt expression. DC-SIGN was required for Lb. rhamnosus JB-1 adhesion and influenced IL-12 secretion, while TLR-2 influenced IL-10 and IL-12 secretion. Here we demonstrate that the delayed kinetics of bacterial processing by MDDCs correlates with MDDC activation and stimulation of lymphocytes. Thus, inhibition or delay of intracellular processing may be a novel strategy by which certain commensals may avoid the induction of proinflammatory responses.  相似文献   
23.
The nitrogen (N) cycle is essentially 'leaky'. The losses of small amounts of nitrate to waters and of ammonia and nitrous oxide to the atmosphere are a part of the global biogeo-chemical N cycle. However, intensive agricultural production, industry and vehicle use have more than doubled the amount of 'reactive' N in the environment, resulting in eutrophication, ecosystem change and health concerns. Research has identified agricultural practices that cause large losses of N and, in some cases, developed solutions. This paper discusses the problems of maintaining productivity while reducing N losses, compares conventional with low input (integrated) and organic farming systems, and discusses wider options. It also looks at the need to integrate studies on N with other environmental impacts, set in the context of the whole farm system, to provide truly sustainable agricultural systems.  相似文献   
24.
Epidemiological study on strongyloidiasis in humans is currently lacking in Malaysia. Thus, a cross-sectional study was carried out to determine the prevalence of Strongyloides stercoralis infection among the inhabitants of longhouse indigenous communities in Sarawak. A single stool and blood sample were collected from each participant and subjected to microscopy, serological and molecular techniques. Five species of intestinal parasites were identified by stool microscopy. None of the stool samples were positive for S. stercoralis. However, 11% of 236 serum samples were seropositive for strongyloidiasis. Further confirmation using molecular technique on stool samples of the seropositive individuals successfully amplified 5 samples, suggesting current active infections. The prevalence was significantly higher in adult males and tended to increase with age. S. stercoralis should no longer be neglected in any intestinal parasitic survey. Combination of more than 1 diagnostic technique is necessary to increase the likelihood of estimating the ‘true’ prevalence of S. stercoralis.  相似文献   
25.
Propolis is a multi-functional bee product rich in polyphenols. In this study, the inhibitory effect of Anatolian propolis against SARS-coronavirus-2 (SARS-CoV-2) was investigated in vitro and in silico. Raw and commercial propolis samples were used, and both samples were found to be rich in caffeic acid, p-coumaric acid, ferulic acid, t-cinnamic acid, hesperetin, chrysin, pinocembrin, and caffeic acid phenethyl ester (CAPE) at HPLC-UV analysis. Ethanolic propolis extracts (EPE) were used in the ELISA screening test against the spike S1 protein (SARS-CoV-2): ACE-2 interaction for in vitro study. The binding energy values of these polyphenols to the SARS-CoV-2 spike and ACE-2 protein were calculated separately with a molecular docking study using the AutoDock 4.2.6 program. In addition, the pharmacokinetics and drug-likeness properties of these eight polyphenols were calculated according to the SwissADME tool. The binding energy value of pinocembrin was highest in both receptors, followed by chrysin, CAPE, and hesperetin. Based on the in silico modeling and ADME (absorption, distribution, metabolism, and excretion) behaviors of the eight polyphenols, the compounds exhibited the potential ability to act effectively as novel drugs. The findings of both studies showed that propolis has a high inhibitory potential against the Covid-19 virus. However, further studies are now needed.  相似文献   
26.
ABSTRACT. A new marine cyrtophorian ciliate Trichopodiella faurei n. sp., which belongs to the order Dysteriida, family Hartmannulidae, was investigated at the morphological and molecular levels. A combination of morphological features of the organism including the oval body shape, 2–3 contractile vacuoles, 22–28 nematodesmal rods in the cytopharyngeal basket, and 31–39 somatic kineties, distinguishes it from all other known congeners. In reconstructed small subunit (SSU) rRNA phylogenies, T. faurei groups with Isochona, a representative genus of the subclass Chonotrichia. The similarity of the infraciliature between hartmannulids and several chonotrichian examples also suggests that these taxa should be closely related. A new S943 intron belonging to group IC1 was identified in the SSU rRNA gene of this species. This intron is phylogenetically related to the S891 introns previously found in the suctorians Acineta sp. and Tokophrya lemnarum, and their internal guide sequences share four nucleotides, indicating that these introns were vertically inherited from a common phyllopharyngean ancestor and that reverse splicing might have been involved in the transposition.  相似文献   
27.
ABSTRACT. The urosylid genus Pseudoamphisiella was established by Song (1996) with hitherto only two known congeners. In the present work, the morphology and infraciliature of a new member, Pseudoamphisiella quadrinucleata n. sp., a form with conspicuous alveolar layer and four macronuclear nodules isolated from the coastal waters both near Hong Kong and near Guangzhou, South China were investigated using living observation and protargol silver impregnation methods. Pseudoamphisiella quadrinucleata differs from other two known forms mainly by the number of macronuclear nodules: constantly four vs. two in Pseudoamphisiella alveolata and 24–57 in Pseudoamphisiella lacazei. To support this, the sequence of the small subunit rDNA of P. quadrinucleata n. sp. showed 14 and 74 nucleotides in comparison with that of the two known congeners, respectively, which hence firmly supports the validity of the new species.  相似文献   
28.
29.
Reactive oxygen species (ROS) have traditionally been viewed as a toxic group of molecules; however, recent publications have shown that these molecules, including H2O2, can also strongly promote cell survival. Even though the retina has a large capacity to produce ROS, little is known about its non-mitochondrial sources of these molecules, in particular the expression and function of NADPH oxidase (Nox) proteins which are involved in the direct generation of superoxide and indirectly H2O2. This study demonstrated that 661W cells, a retina-derived cell line, and mouse retinal explants express Nox2, Nox4 and certain of their well-established regulators. The roles of Nox2 and Nox4 in producing pro-survival H2O2 were determined using 661W cells and some of the controlling factors were identified. To ascertain if this phenomenon could have physiological relevance, the novel technique of time-lapse imaging of dichlorofluorescein fluorescence (generated upon H2O2 production) in retinal explants was established and it showed that explants also produce a burst of H2O2. The increase in H2O2 production was partly blocked by an inhibitor of Nox proteins. Overall, this study demonstrates a pro-survival role of Nox2 and Nox4 in retina-derived cells, elucidates some of the regulatory mechanisms and reveals that a similar phenomenon exists in retinal tissue as a whole.  相似文献   
30.
The energy produced from the investment in biofuel crops needs to account for the environmental impacts on soil, water, climate change and ecosystem services. A regionalized approach is needed to evaluate the environmental costs of large-scale biofuel production. We present a regional pan-European simulation of rapeseed ( Brassica napus ) cultivation. Rapeseed is the European Union's dominant biofuel crop with a share of about 80% of the feedstock. To improve the assessment of the environmental impact of this biodiesel production, we performed a pan-European simulation of rapeseed cultivation at a 10 × 10 km scale with Environmental Policy Integrated Climate (EPIC). The model runs with a daily time step and model input consists of spatialized meteorological measurements, and topographic, soil, land use, and farm management practices data and information. Default EPIC model parameters were calibrated based on literature. Modelled rapeseed yields were satisfactory compared with yields at regional level reported for 151 regions obtained for the period from 1995 to 2003 for 27 European Union member countries, along with consistent modelled and reported yield responses to precipitation, radiation and vapour pressure deficit at regional level. The model is currently set up so that plant nutrient stress is not occurring. Total fertilizer consumption at country level was compared with IFA/FAO data. This approach allows us to evaluate environmental pressures and efficiencies arising from and associated with rapeseed cultivation to further complete the environmental balance of biofuel production and consumption.  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