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   79篇
  免费   6篇
  2023年   3篇
  2022年   1篇
  2021年   2篇
  2020年   3篇
  2019年   4篇
  2018年   1篇
  2016年   2篇
  2015年   4篇
  2014年   3篇
  2013年   6篇
  2012年   4篇
  2011年   2篇
  2010年   2篇
  2009年   6篇
  2008年   4篇
  2007年   8篇
  2006年   3篇
  2005年   4篇
  2004年   6篇
  2003年   1篇
  2001年   1篇
  2000年   4篇
  1999年   1篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1992年   2篇
  1991年   3篇
  1990年   1篇
  1984年   1篇
排序方式: 共有85条查询结果,搜索用时 15 毫秒
31.
Abstract

In this study, roots, stems and leaves of the worldwide distributed macrophyte Phragmites australis (common reed) were tested as potential removal and biomonitors of trace elements contamination in sediment. In particular, the concentrations (100, 200, and 500?mg/kg) of the following elements were analyzed: Zn, Cu, Pb, and Fe. Results showed that the amount of concentrations in plant tissues is significantly (p?≤?0.01) dependent on the kind of organ and element. Trace element concentrations decreased according to the pattern of Fea (Rootsa > Stemsb > Leavesb) > Znb (Roota > Leavesb > Stemsc) > Cuc (Rootsa > Leavesb > Stemsc) > Pbc (Rootsa > Stemsb > Leavesc), as well as the roots acted as the main centers of bioaccumulation for all elements studied, and stems as the transit organs for translocation from roots to leaves. The major mechanisms employed by the plant were probably phytostabilization on the basis of the calculated Biological Concentration Factor (BCF – metal concentration ratio of plant root to soil); and Translocation Factor (TF – metal concentration ratio of plants roots to above ground part). Finally, due to the low scavenger effect of the radical DPPH, we excluded the hypothesis of the use of antioxidant mechanism in the tolerance of metals.  相似文献   
32.
The coronary artery disease (CAD) is a chronic inflammatory disease involving genetic as well as environmental factors. Recent evidence suggests that the oral microbiome has a significant role in triggering atherosclerosis. The present study assessed the oral microbiome composition variation between coronary patients and healthy subjects in order to identify a potential pathogenic signature associated with CAD. We performed metagenomic profiling of salivary microbiomes by 16S ribosomal RNA (rRNA) next-generation sequencing. Oral microbiota profiling was performed for 30 individuals including 20 patients with CAD and ten healthy individuals without carotid plaques or previous stroke or myocardial infarction.We found that oral microbial communities in patients and healthy controls are represented by similar global core oral microbiome. The predominant taxa belonged to Firmicutes (genus Streptococcus, Veillonella, Granulicatella, Selenomonas), Proteobacteria (genus Neisseria, Haemophilus), Actinobacteria (genus Rothia), Bacteroidetes (genus Prevotella, Porphyromonas), and Fusobacteria (genus Fusobacterium, Leptotrichia). More than 60% relative abundance of each sample for both CAD patients and controls is represented by three major genera including Streptococcus (24.97 and 26.33%), Veillonella (21.43 and 19.91%), and Neisseria (14.23 and 15.33%).Using penalized regression analysis, the bacterial genus Eikenella was involved as the major discriminant genus for both status and Syntax score of CAD. We also reported a significant negative correlation between Syntax score and Eikenella abundance in coronary patients’ group (Spearman rho = −0.68, P=0.00094).In conclusion, the abundance of Eikenella in oral coronary patient samples compared with controls could be a prominent pathological indicator for the development of CAD.  相似文献   
33.
Clove bud is a medicinal plant used traditionally in Asia for the treatment of various disease. Previously, Clove oil is a potential source of an antimicrobial compounds especially vis-a-vis bacterial pathogens. However, the compound responsible for this activity remains to be investigated. Essential oil (EO) clove, acetylated essential oil clove, eugenol, and acetyleugenol were evaluate as an antibacterial potential agent against Staphyloccocus aureus (SE), Escherichia coli (EC) and Pseudomonas aeruginosa (PA). Essential oil containing eugenol was extracted from buds of Eugenia caryophyllata commonly named clove (Syzygium aromaticum (L.) (Family Myrtaceae) by a simple hydrodistillation. The analysis of the essential oils (EOs) using gas chromatography-mass spectrometry (GC-MS) shows eugenol as the major constituent with 70.14 % of the total. The Eugenol was isolated from the EO using chemical treatment. Afterwards, the EO and eugenol were converted to acetylated EO and acetyleugenol, respectively using acetic anhydride. The antibacterial result revealed that all compounds showed a strong activity against the three strains. The Staphyloccocus aureus and Pseudomonas aeruginosa were extremely sensitive against eugenol with an inhibition diameters of 25 mm. The MIC values of eugenol versus S. aureus and P. aeruginosa were 0.58 and 2.32 mg/mL, respectively, while the MIB values were 2.32 mg/mL and 9.28 mg/mL.  相似文献   
34.
This present review gives an overview on Linkage disequilibrium (LD), its measures and its different utilizations in human genetics studies. In the first part, we provide a detailed and a simplified presentation focusing on the definition of LD, its measures and the major software for its evaluation. Thereafter, we describe and discuss the biological and evolutionary mechanisms which create, remodel, maintain or destroy LD in human population. Consensus has now emerged on the pattern of LD in the genome which has a block-like organization with block of high disequilibrium interrupted by recombination hotspots. However, no standard method exists for the determination of such blocks and, more importantly, for the identification of TagSNP. This would yield inconsistencies between different studies of the same genes, compromising the practical use of TagSNP in association studies. The ACE gene is used to illustrate this. Will it be possible to identify consensus TagSNP that could be used consistently in all populations for testing association of candidate genes in common diseases? What is the part of myth and reality in what is called "individualized medicine"? We conclude that further LD studies are needed to get clear insights into this matter.  相似文献   
35.
Alpha scorpion toxins bind to receptor site 3 on voltage-dependent sodium channels and inhibit their inactivation. The alpha-scorpion toxin BotIII is the most toxic protein of Buthus occitanus tunetanus. Its sequence differs only by three amino acid residues from that of AahII, the most active alpha-toxin. Due to their high affinity and selectivity for mammalian sodium channels, BotIII and AahII represent powerful tools for studying the molecular determinants of specificity for voltage-dependent sodium channels. Sequence analysis of BotIII gene has revealed two exons separated by a 381-bp intron and a signal peptide of 19 amino acids. We succeeded in expressing BotIII in significantly higher amounts than AahII the only expressed strict alpha anti-mammalian scorpion toxin reported in the literature. We have also modified specific amino acid residues of BotIII. The recombinant and the natural toxins differ by the amidation of the C-terminal residue. Toxicity and binding experiments indicated: (a) the affinity of rBotIII-OH and rAahII-OH (rBotIII-OH with the 3 mutations R10V, V51L, N64H) for the voltage-dependent sodium channels is reduced compared to the natural toxins. This data revealed the important role of the C-terminal amidation for the biological activity of BotIII and AahII; (b) the single mutation N64H is responsible for the difference of toxicity and affinity between rBotIII-OH and rAahII-OH; (c) the addition of the sequence GR to rBotIII-OH leads to the loss of biological activity. This study is in agreement with the important role attributed to the C-terminal sequence of alpha-toxins in their interaction with sodium channels receptors.  相似文献   
36.
Juniperus drupacea is an eastern Mediterranean mountain tree with a disjunct geographical range. We hypothesized that this disjunct occurrence (the Peloponnese in Europe and the Taurus and Lebanon Mountains in Asia) should be reflected in the patterns of genetic and morphological diversity and differentiation. Nuclear microsatellite markers (nSSR) and biometric variables of the cones and seeds were examined on material sampled from four populations in Europe and eight in Asia. The Asian populations were characterized by a higher level of genetic diversity than the European populations. The genetic differentiation among populations was moderate but significant (FST = 0.101, < 0.001). According to the clustering performed with BAPS, six genetically and geographically groups of populations were found: I and II from the Peloponnese; III from the Taurus Mountains; IV and V from the Anti‐Taurus Mountains; and VI from the Lebanon Mountains. The level of genetic differentiation among these six groups (4.30%, P = 0.012) probably reflects long‐lasting genetic isolation during the Pleistocene, as limited genetic admixture was found. In accordance with genetic analysis, the biometric investigations indicated a high level of morphological divergence between the European and Asian populations of the species, with further differentiation between the populations from the Taurus and Lebanon Mountains.  相似文献   
37.
The first large‐scale fine characterization of Tunisian H lineages clarifies that the post‐Last glacial maximum expansion originating in Iberia not only led to the resettlement of Europe but also of North Africa. We found that 46% of 81 Tunisian H lineages subscreened for 1,580 bp in mtDNA coding region were affiliated with H1 and H3 subhaplogroups, which are known to have originated in Iberia. Although no signs of local expansion were detected, which would allow a clear dating of their introduction, the younger and less diverse Tunisian H1 and H3 lineages indicate Iberia as the radiating centre. Major contributions from historical migrations to this Iberian genetic imprint in Tunisia were ruled out by the mtDNA gene pool similarity between Berber/Arab/cosmopolitan samples and some “Andalusian” communities, settled by the descendents of the “Moors” who once lived in Iberia for 10 centuries (between 8th and 17th centuries), before being expelled to Tunisia. Am J Phys Anthropol, 2009. © 2008 Wiley‐Liss, Inc.  相似文献   
38.
39.
Effect of initial interference fit on pull-out strength in cementless fixation between bovine tibia and smooth stainless steel post was investigated in this study.Compressive behavior of bovine spongious bone was studied using mechanical testing in order to evaluate the elastic-plastic properties in different regions of the proximal tibia.Friction tests were carried out in the aim to evaluate the friction behavior of the contact between bovine spongious bone and stainless steel.A cylindrical stainless steel post inserted in a pre-drilled bovine tibia with an initial interference fit was taken as an in vitro model to assess the contribution of post fixation to the initial stability of the Total Knee Arthroplasty (TKA) tibial component.Pull-out experiments were carried out for different initial interference fits.Finite Element Models (FEM) using local elastic-plastic properties of the bovine bone were developed for the analysis of the experimental ultimate pull-out force results.At the post/bone interface,Coulomb friction was considered in the FEM calculations with pressure-dependent friction coefficient.It was found that the FEM results of the ultimate force are in good agreement with the experimental results.The analysis of the FEM interfacial stresses indicates that the micro-slip initiation depends on the local bone properties.  相似文献   
40.
This article documents the addition of 299 microsatellite marker loci and nine pairs of single-nucleotide polymorphism (SNP) EPIC primers to the Molecular Ecology Resources (MER) Database. Loci were developed for the following species: Alosa pseudoharengus, Alosa aestivalis, Aphis spiraecola, Argopecten purpuratus, Coreoleuciscus splendidus, Garra gotyla, Hippodamia convergens, Linnaea borealis, Menippe mercenaria, Menippe adina, Parus major, Pinus densiflora, Portunus trituberculatus, Procontarinia mangiferae, Rhynchophorus ferrugineus, Schizothorax richardsonii, Scophthalmus rhombus, Tetraponera aethiops, Thaumetopoea pityocampa, Tuta absoluta and Ugni molinae. These loci were cross-tested on the following species: Barilius bendelisis, Chiromantes haematocheir, Eriocheir sinensis, Eucalyptus camaldulensis, Eucalyptus cladocalix, Eucalyptus globulus, Garra litaninsis vishwanath, Garra para lissorhynchus, Guindilla trinervis, Hemigrapsus sanguineus, Luma chequen. Guayaba, Myrceugenia colchagüensis, Myrceugenia correifolia, Myrceugenia exsucca, Parasesarma plicatum, Parus major, Portunus pelagicus, Psidium guayaba, Schizothorax richardsonii, Scophthalmus maximus, Tetraponera latifrons, Thaumetopoea bonjeani, Thaumetopoea ispartensis, Thaumetopoea libanotica, Thaumetopoea pinivora, Thaumetopoea pityocampa ena clade, Thaumetopoea solitaria, Thaumetopoea wilkinsoni and Tor putitora. This article also documents the addition of nine EPIC primer pairs for Euphaea decorata, Euphaea formosa, Euphaea ornata and Euphaea yayeyamana.  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