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   601篇
  免费   30篇
  国内免费   4篇
  2024年   1篇
  2023年   18篇
  2022年   33篇
  2021年   53篇
  2020年   26篇
  2019年   32篇
  2018年   36篇
  2017年   25篇
  2016年   29篇
  2015年   28篇
  2014年   34篇
  2013年   62篇
  2012年   46篇
  2011年   46篇
  2010年   27篇
  2009年   13篇
  2008年   23篇
  2007年   11篇
  2006年   10篇
  2005年   11篇
  2004年   13篇
  2003年   10篇
  2002年   12篇
  2001年   6篇
  2000年   5篇
  1999年   6篇
  1998年   1篇
  1997年   4篇
  1996年   2篇
  1995年   1篇
  1994年   4篇
  1992年   3篇
  1984年   1篇
  1973年   1篇
  1954年   1篇
  1872年   1篇
排序方式: 共有635条查询结果,搜索用时 281 毫秒
91.
Heavy metal contamination in soil is an important environmental problem and it has negative effect on agriculture. Bacteria play a major role in phytoremediation of heavy metals contaminated soil. In this study, the effect of Bacillus licheniformis NCCP-59, a halophilic bacterium isolated from salt mines near Karak, Pakistan, were determined on a three week old greenhouse grown seedling and germinating seeds of two rice varieties (Basmati-385 (B-385) and KSK-282) in soil contaminated with different concentrations (0, 100, 250, 500, and 1000 ppm) of Nickel. Nickel significantly reduced the germination rate and germination percentage mainly at 500 and 1000 ppm. Significant decrease in ion contents (Na, K, and Ca) was observed while Ni ion concentration in the plant tissues increases as the concentration of Ni applied increases. The photosynthetic pigments (chlorophyll a (chl a), chlorophyll b (chl b), and carotenoids) were also decreased by the application of different concentrations of Ni. Total protein and organic nitrogen were found to be reduced at higher concentrations of Nickel. Inoculation of Bacillus Licheniformis NCCP-59 improved seed germination and biochemical attribute of the plant under Ni stress. It is clear from the results that the Bacillus Licheniformis NCCP-59 strain has the ability to protect the plants from the toxic effects of nickel and can be used for the phytoremediation of Ni contaminated soil.  相似文献   
92.
93.
Tomato (Solanum lycopersicum L.) is the second most important cultivated crop next to potato, worldwide. Tomato serves as an important source of antioxidants in human diet. Alternaria solani and Fusarium oxysporum cause early blight and vascular wilt of tomato, respectively, resulting in severe crop losses. The foremost objective of the present study was to generate transgenic tomato plants with rolB gene and evaluate its effect on plant morphology, nutritional contents, yield and resistance against fungal infection. Tomato cv. Rio Grande was transformed via Agrobacterium tumefaciens harbouring rolB gene of Agrobacterium rhizogenes. rolB. Biochemical analyses showed considerable improvement in nutritional quality of transgenic tomato fruits as indicated by 62% increase in lycopene content, 225% in ascorbic acid content, 58% in total phenolics and 26% in free radical scavenging activity. Furthermore, rolB gene significantly improved the defence response of leaves of transgenic plants against two pathogenic fungal strains A. solani and F. oxysporum. Contrarily, transformed plants exhibited altered morphology and reduced fruit yield. In conclusion, rolB gene from A. rhizogenes can be used to generate transgenic tomato with increased nutritional contents of fruits as well as improved foliar tolerance against fungal pathogens.  相似文献   
94.
95.
Pheasant reintroduction and conservation efforts have been in place in Pakistan since the 1980 s, yet there is still a scarcity of data on pheasant microbiome and zoonosis. Instead of growing vast numbers of bacteria in the laboratory, to investigate the fecal microbiome, pheasants (green and ring neck pheasant) were analyzed using 16S rRNA metagenomics and using IonS5TMXL sequencing from two flocks more than 10 birds. Operational taxonomic unit (OTU) cluster analysis and phylogenetic tree analysis was performed using Mothur software against the SSUrRNA database of SILVA and the MUSCLE (Version 3.8.31) software. Results of the analysis showed that firmicutes were the most abundant phylum among the top ten phyla, in both pheasant species, followed by other phyla such as actinobacteria and proteobacteria in ring necked pheasant and bacteroidetes in green necked pheasant. Bacillus was the most relatively abundant genus in both pheasants followed by Oceanobacillus and Teribacillus for ring necked pheasant and Lactobacillus for green necked pheasant. Because of their well-known beneficial characteristics, these genus warrants special attention. Bird droppings comprise germs from the urinary system, gut, and reproductive sites, making it difficult to research each anatomical site at the same time. We conclude that metagenomic analysis and classification provides baseline information of the pheasant fecal microbiome that plays a role in disease and health.  相似文献   
96.
Post-translational modification of proteins by lysine acetylation plays important regulatory roles in living cells. The budding yeast Saccharomyces cerevisiae is a widely used unicellular eukaryotic model organism in biomedical research. S. cerevisiae contains several evolutionary conserved lysine acetyltransferases and deacetylases. However, only a few dozen acetylation sites in S. cerevisiae are known, presenting a major obstacle for further understanding the regulatory roles of acetylation in this organism. Here we use high resolution mass spectrometry to identify about 4000 lysine acetylation sites in S. cerevisiae. Acetylated proteins are implicated in the regulation of diverse cytoplasmic and nuclear processes including chromatin organization, mitochondrial metabolism, and protein synthesis. Bioinformatic analysis of yeast acetylation sites shows that acetylated lysines are significantly more conserved compared with nonacetylated lysines. A large fraction of the conserved acetylation sites are present on proteins involved in cellular metabolism, protein synthesis, and protein folding. Furthermore, quantification of the Rpd3-regulated acetylation sites identified several previously known, as well as new putative substrates of this deacetylase. Rpd3 deficiency increased acetylation of the SAGA (Spt-Ada-Gcn5-Acetyltransferase) complex subunit Sgf73 on K33. This acetylation site is located within a critical regulatory domain in Sgf73 that interacts with Ubp8 and is involved in the activation of the Ubp8-containing histone H2B deubiquitylase complex. Our data provides the first global survey of acetylation in budding yeast, and suggests a wide-ranging regulatory scope of this modification. The provided dataset may serve as an important resource for the functional analysis of lysine acetylation in eukaryotes.Lysine acetylation is a dynamic and reversible post-translational modification. Acetylation of lysines on their ε-amino group is catalyzed by lysine acetyltransferases (KATs1, also known as histone acetyltrasferases (HATs)), and reversed by lysine deacetylases (KDACs, also known as histone deacetylases (HDACs)) (1). The enzymatic machinery involved in lysine acetylation is evolutionary conserved in all forms of life (24). The role of acetylation has been extensively studied in the regulation of gene expression via modification of histones (5). Acetylation also plays important roles in controlling cellular metabolism (610), protein folding (11), and sister chromatid cohesion (12). Furthermore, acetylation has been implicated in regulating the beneficial effects of calorie restriction (13), a low nutrient diet without starvation, and aging. Based on these findings, it is proposed that the functional roles of acetylation in these processes are evolutionary conserved from yeast to mammals.Advancements in mass spectrometry (MS)-based proteomics have greatly facilitated identification of thousands of post-translational modification (PTM) sites in eukaryotic cells (1418). Proteome-wide mapping of PTM sites can provide important leads for analyzing the functional relevance of individual sites and a systems-wide view of the regulatory scope of post-translational modifications. Also, large-scale PTM datasets are an important resource for the in silico analysis of PTMs, which can broaden the understanding of modification site properties and their evolutionary trajectories.The budding yeast Saccharomyces cerevisiae is a commonly used unicellular eukaryotic model organism. Yeast has been used in many pioneering “-omics” studies, including sequencing of the first eukaryotic genome (19), systems-wide genetic interactions analysis (20, 21), MS-based comprehensive mapping of a eukaryotic proteome (22), and proteome-wide analysis of protein-protein interactions (23, 24). In addition, S. cerevisiae has been extensively used to study the molecular mechanisms of acetylation. Many lysine acetyltransferases and deacetylases were discovered in this organism (2, 25), and their orthologs were subsequently identified in higher eukaryotes. Furthermore, the functional roles of many well-studied acetylation sites on histones are conserved from yeast to mammals. Recent data from human and Drosophila cells show that acetylation is present on many highly conserved metabolic enzymes (2628). However, only a few dozen yeast acetylation sites are annotated in the Uniprot database. Given the presence of a well-conserved and elaborate acetylation machinery in yeast, we reasoned that many more acetylation sites exist in this organism that remained to be identified.Here we used high resolution mass spectrometry-based proteomics to investigate the scope of acetylation in S. cerevisiae. We identified about 4000 unique acetylation sites in this important model organism. Bioinformatic analysis of yeast acetylation sites and comparison with previously identified human and Drosophila acetylation sites indicates that many acetylation sites are evolutionary conserved. Furthermore, quantitative analysis of the Rpd3-regulated acetylation sites identified several nuclear proteins that showed increased acetylation in rpd3 knockout cells. Our results provide a systems-wide view of acetylation in budding yeast, and a rich dataset for functional analysis of acetylation sites in this organism.  相似文献   
97.
Reactive oxidative species (ROS) toxicity remains an undisputed cause and link between Alzheimer’s disease (AD) and Type-2 Diabetes Mellitus (T2DM). Patients with both AD and T2DM have damaged, oxidized DNA, RNA, protein and lipid products that can be used as possible disease progression markers. Although the oxidative stress has been anticipated as a main cause in promoting both AD and T2DM, multiple pathways could be involved in ROS production. The focus of this review is to summarize the mechanisms involved in ROS production and their possible association with AD and T2DM pathogenesis and progression. We have also highlighted the role of current treatments that can be linked with reduced oxidative stress and damage in AD and T2DM.  相似文献   
98.
Background:The assembly and disassembly of the focal adhesions (FA) components occurs throughout life cycle of adhesion, with conservation of balance between removal and recruitment rate during temporal stages. Previous studies have demonstrated that phosphotidyilinositols play a role in regulating FA turnover. However, a little attention has been given to quantify the dynamics changes of Phosphatidylinositol 3,4,5-trisphosphate (PtdIns (3,4,5) P3) within and during fast and slow turnover rates of FA.Methods:In this study, we developed a protein purification MDA-MB-231 breast cancer cell line was used as a model in this study due to high metastatic and motile. These cells were co-transfected with GFP- paxillin/vinculin, as FA marker, and the GFP/mCherry-Btk-PH, as a biosensor to visualize PtdIns (3,4,5) P3. Confocal time-lapse images were used to monitor changes or differences in the local generation of PtdIns (3,4,5) P3 within and during assembly and disassembly of FA. Following transfection, immunostaining was used to examine the spatial co-localization between FA and PtdIns (3,4,5) P3.Results:Our data demonstrated that PtdIns (3,4,5) P3 co-localized with FAs and increase during assembly and decline during disassembly of FA which exhibits slow turnover rates and was in a constant level during assembly and disassembly of FA that displays fast turnover rates.DiscussionOur result suggested that the dynamic changes of PtdIns (3,4,5) P3, it may depend on components undergo turnover, such that early, nascent FA displays fast turnover rates and mature FA exhibits slow turnover rates. Thus, the local enrichment of PtdIns (3,4,5) P3 enhances FA assembly and disassembly activation.Key Words: Cancer cell migration, Focal adhesion turnover, MDA-MB-231 cell line, PtdIns (3,4,5) P3  相似文献   
99.

Background  

Autosomal recessive primary microcephaly is a disorder of neurogenic mitosis that causes reduction in brain size. It is a rare heterogeneous condition with seven causative genes reported to date. Mutations in WD repeat protein 62 are associated with autosomal recessive primary microcephaly with cortical malformations. This study was initiated to screen WDR62 mutations in four consanguineous Pakistani families with autosomal recessive primary microcephaly.  相似文献   
100.
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