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   396篇
  免费   33篇
  国内免费   25篇
  2023年   5篇
  2022年   7篇
  2021年   14篇
  2020年   15篇
  2019年   9篇
  2018年   15篇
  2017年   14篇
  2016年   16篇
  2015年   19篇
  2014年   37篇
  2013年   38篇
  2012年   15篇
  2011年   18篇
  2010年   17篇
  2009年   19篇
  2008年   14篇
  2007年   17篇
  2006年   16篇
  2005年   18篇
  2004年   14篇
  2003年   10篇
  2002年   8篇
  2001年   3篇
  2000年   3篇
  1999年   9篇
  1998年   4篇
  1997年   5篇
  1996年   5篇
  1995年   7篇
  1994年   5篇
  1993年   5篇
  1992年   5篇
  1991年   2篇
  1990年   3篇
  1989年   5篇
  1988年   5篇
  1987年   2篇
  1986年   2篇
  1985年   4篇
  1984年   3篇
  1983年   2篇
  1982年   5篇
  1981年   1篇
  1979年   2篇
  1978年   3篇
  1977年   4篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1972年   1篇
排序方式: 共有454条查询结果,搜索用时 265 毫秒
11.
12.
Several plaque assay techniques employing TN-368 or IPLB-SF 21AE cells were evaluated for their usefulness in detecting and distinguishing MP (many polyhedra) and FP (few polyhedra) plaque variants of Galleria mellonella nuclear polyhedrosis virus. Both plaque morphologies were produced using either cell line. Of the overlays tested, the buffered 0.6% methylcellulose overlay yielded the most plaques and was best suited for titration. It was also the easiest overlay to prepare and use. The largest plaques were obtained using either cell line with the 1.0 or 0.75% agarose overlays. Plaque variants were most easily distinguished under 1.0 or 0.75% agarose overlays with IPLB-SF 21 cells. The 0.9% MC overlay was the only overlay which did not allow detection of FP plaques. However, FP plaques were detected using a buffered modification of this overlay. It is concluded that the FP variant of G. mellonella NPV is not a host-dependent phenomenon, and that its detection can be influenced by overlay formulation.  相似文献   
13.
Monensin blocks endocytosis of vesicular stomatitis virus   总被引:8,自引:0,他引:8  
Monensin inhibits the infection of mouse cells by Vesicular Stomatitis Virus (VSV). At low drug concentrations (0.5 μM), endocytosis of VSV is inhibited whereas viral binding is unaffected. Monensin may be useful for analyzing the internalization of other viruses as well as soluble ligands.  相似文献   
14.
Antibiotics are essential in many life‐threatening diseases. On the other hand, improper use of antibiotics can be disastrous. Cell morphological changes were observed in the ciprofloxacin‐treated cells starting at 48 hours. Changes in cell morphology were continuously observed up to 14 days, which showed gradual morphological changes from monocyte to plaque‐like cells at day 12, and foam cell, which is an intermediate stage in atherosclerosis was observed at day 8, which was confirmed with Oil Red O staining. Flow cytometry data revealed that oxidized LDL (oxyLDL)‐induced cells showed 60.16% of CD64 (proinflammatory macrophage markers) and no expression of CD23 (anti‐inflammatory macrophage markers), whereas ciprofloxacin‐treated cells expressed 67.97% of CD64 and 13.78% of CD23. Chemokine antibody array analysis revealed that ciprofloxacin exposed cells showed a proinflammatory role (ENA78, Eotaxin1, Eotaxin2, IP‐10, MIG, MIP‐3β, SDF‐1β, TECK, CXCL16, and Fractalkine). Liquid chromatography with tandem mass spectrometry (LC‐MS/MS) revealed that myristic acid was incorporated into a protein with 68 kDa molecular mass in exposing oxyLDL‐induced monocytes with ciprofloxacin, which could be a reason for the observed foam cells and in vitro plaque formation. As myristic acid primes atherosclerosis, it is better to limit the intake of antibiotics like ciprofloxacin for common illness, specifically the high‐risk patients, which may contribute to atherosclerosis.  相似文献   
15.
中尼廊道地区作为南亚通道建设的关键环节,具有生态环境脆弱且对生态资源依赖性强的基本特征,中尼廊道建设占用生态空间,将增加生态系统对农牧业生产活动的承载压力;因此,开展中尼廊道生态承载力研究对青藏高原生态保护和南亚通道建设具有重要的实践价值和指导意义。本文基于生态供给与消耗平衡关系,通过计算农牧业生产对生态系统净初级生产力的消耗,评估中尼廊道地区的生态承载力,结果表明:(1)中尼廊道地区生态承载力处于富富有余状态,2015年有7个县域生态承载力处于临界超载或平衡有余状态;整体上生态系统尚有较大的生态空间来支撑中尼廊道建设,但建设可能給局部县域带来超载风险。(2)中尼廊道地区生态系统供给量处于稳定波动状态,畜牧业生态消耗在生态消耗中占主导地位(占比超80%);得益于2005年起实施的草畜平衡政策,中尼廊道地区及其24个县域生态消耗量呈下降趋势,农牧业生产活动对生态系统造成的压力降低,生态承载状态向优发展;但地处粮食主产区、口岸区、城市化辐射区的7个县域,在本地及周边地区日益增长的对农牧业产品的生活需求驱动下生态消耗量处于增加态势。(3)若以实现生物多样性公约所倡导的50%生态资源得到保护为生态保护目标,目前中尼廊道农牧业生产模式产生的生态消耗将超出其可利用供给,区域可持续发展需要关注如何通过中尼廊道建设带动当地产业结构调整以缓解农牧业生产对生态系统的压力。  相似文献   
16.
Clinical decision is often difficult with chlorhexidine mouthwash. The use of antioxidant mouthwashes for the treatment of periodontal disease is in practise. Therefore, it is of interest to collect gleaned information on Antioxidant mouthwashes as periodontal therapy from known literature. Improvement in treatment using antioxidant mouthwashes is reported in several studies. The mouthwash with antioxidants has similar anti-gingivitis, antiplaque and antimicrobial effects as that of chlorhexidine mouthwash.  相似文献   
17.
18.
Cold‐water coral (CWC) reefs are recognized as ecologically and biologically significant areas that generate habitats and diversity. The interaction between hydrodynamics and CWCs has been well studied at the Mingulay Reef Complex, a relatively shallow area of reefs found on the continental shelf off Scotland, UK. Within ‘Mingulay Area 01’ a rapid tidal downwelling of surface waters, brought about as an internal wave, is known to supply warmer, phytoplankton‐rich waters to corals growing on the northern flank of an east‐west trending seabed ridge. This study shows that this tidal downwelling also causes short‐term perturbations in the inorganic carbon (CT) and nutrient dynamics through the water column and immediately above the reef. Over a 14 h period, corresponding to one semi‐diurnal tidal cycle, seawater pH overlying the reef varied by ca. 0.1 pH unit, while pCO2 shifted by >60 μatm, a shift equivalent to a ca. 25 year jump into the future, with respect to atmospheric pCO2. During the summer stratified period, these downwelling events result in the reef being washed over with surface water that has higher pH, is warmer, nutrient depleted, but rich in phytoplankton‐derived particles compared to the deeper waters in which the corals sit. Empirical observations, together with outputs from the European Regional Shelf Sea Ecosystem Model, demonstrate that the variability that the CWC reefs experience changes through the seasons and into the future. Hence, as ocean acidification and warming increase into the future, the downwelling event specific to this site could provide short‐term amelioration of corrosive conditions at certain times of the year; however, it could additionally result in enhanced detrimental impacts of warming on CWCs. Natural variability in the CT and nutrient conditions, as well as local hydrodynamic regimes, must be accounted for in any future predictions concerning the responses of marine ecosystems to climate change.  相似文献   
19.
Periodontitis is a major cause of tooth loss in adults that initially results from dental plaque. Subgingival plaque pathogenesis is affected by both community composition and plaque structures, although limited data are available concerning the latter. To bridge this knowledge gap, subgingival plaques were obtained using filter paper (the fourth layer) and curette (the first-third layers) sequentially and the phylogenetic differences between the first–third layers and the fourth layer were characterized by sequencing the V3–V4 regions of 16S rRNA. A total of 11 phyla, 148 genera, and 308 species were obtained by bioinformatic analysis, and no significant differences between the operational taxonomic unit numbers were observed for these groups. In both groups, the most abundant species were Porphyromonas gingivalis and Fusobacterium nucleatum. Actinomyces naeslundii, Streptococcus intermedius, and Prevotella intermedia possessed relatively high proportions in the first–third layers; while in the fourth layer, both traditional pathogens (Treponema denticola and Campylobacter rectus) and novel pathobionts (Eubacterium saphenum, Filifactor alocis, Treponema sp. HOT238) were prominent. Network analysis showed that either of them exhibited a scale-free property and was constructed by two negatively correlated components (the pathogen component and the nonpathogen component), while the synergy in the nonpathogen component was lower in the first–third layers than that in the fourth layer. After merging these two parts into a whole plaque group, the negative/positive correlation ratio increased. With potential connections, the first–third layers and the fourth layer showed characteristic key nodes in bacterial networks.  相似文献   
20.
Abstract

Biofilm fluoride reservoirs may be a source of fluoride to the fluid phase during a sugar challenge reducing tooth mineral loss. However, the evidence for that is conflicting and has not been studied in biofilms containing different fluoride levels. In order to test fluoride release from biofilms with distinct fluoride concentrations, biofilms were grown in situ exposed to a combination of placebo, calcium and fluoride rinses forming biofilms with no (fluoride-free rinses), low (fluoride-only rinses) or high (calcium followed by fluoride rinses) fluoride concentrations, and collected before and 5?min after a sucrose challenge. Rinsing with fluoride increased fluoride concentration in the biofilm (p?<?0.05), mainly when a calcium pre-rinse was used before the fluoride (p?<?0.05). However, after a sugar challenge, no significant increase in the biofilm fluid fluoride concentration was observed, even in the fluoride-rich biofilms (p?>?0.05). Fluoride-rich biofilms do not release fluoride to the fluid phase during a sugar challenge.  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