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   199篇
  免费   7篇
  206篇
  2024年   3篇
  2023年   5篇
  2022年   8篇
  2021年   18篇
  2020年   11篇
  2019年   8篇
  2018年   13篇
  2017年   8篇
  2016年   15篇
  2015年   14篇
  2014年   15篇
  2013年   15篇
  2012年   20篇
  2011年   8篇
  2010年   4篇
  2009年   5篇
  2008年   6篇
  2007年   6篇
  2006年   1篇
  2005年   5篇
  2004年   2篇
  2003年   1篇
  2002年   4篇
  1999年   2篇
  1997年   3篇
  1994年   2篇
  1993年   1篇
  1991年   1篇
  1990年   1篇
  1981年   1篇
排序方式: 共有206条查询结果,搜索用时 15 毫秒
81.
Cyclic nucleotide gated ion channels (CNGCs) in plants have very important role in signaling and development. The study reports role of CNGC19 and CNGC20 in salt stress in A. thaliana. In-silico, genome wide analysis showed that CNGC19 and CNGC20 are related to salt stress with maximum expression after 6 h in A. thaliana. The position of inserted T-DNA was determined (in-vivo) through TAIL-PCR for activation tagged mutants of CNGC19 and CNGC20 under salt stress. The expression of AtCNGC19 and AtCNGC20 after cloning under 35S promoter of expression vectors pBCH1 and pEarleyGate100 was determined in A. thaliana by real-time PCR analysis. Genome wide analysis showed that AtCNGC11 had lowest and AtCNGC20 highest molecular weight as well as number of amino acid residues. In-vivo expression of AtCNGC19 and AtCNGC20 was enhanced through T-DNA insertion and 35S promoter in over-expressed plants under high salt concentration. AtCNGC19 was activated twice in control and about five times under 150 mM NaCl stress level, and expression value was also higher than AtCNGC20. Phenotypically, over-expressed plants and calli were healthier while knock-out plants and calli showed retarded growth under salinity stress. The study provides new insight for the role of AtCNGC19 and AtCNGC20 under salt stress regulation in A. thaliana and will be helpful for improvement of crop plants for salt stress to combat food shortage and security.  相似文献   
82.
This study has been undertaken to explore the therapeutic effects of deguelin and specific siRNAs in HeLa cells. The data provided clearly show the silencing of ERK 1/2 with siRNAs and inhibition of ERK1/2 with deguelin treatment in HeLa cells. Additionally, we are providing information that deguelin binds directly to anti-apoptotic Bcl-2, Bcl-xl and Mcl-1 in the hydrophobic grooves, thereby releasing BAD and BAX from dimerization with these proteins. This results in increased apoptotic activity through the intrinsic pathway involved in rupture of mitochondrial membrane and release of cytochrome C. Evidence for inhibition of ERK1/2 by deguelin and escape of BAD phosphorylation at serine 112 through ERK/RSK pathway has been further fortified by obtaining similar results by silencing ERK 1/2 each with specific siRNAs. Increase in BAD after treatment with deguelin or siRNAs has been interpreted to mean that deguelin acts through several alternative pathways and therefore can be used as effective therapeutic agent.  相似文献   
83.
Calcium-independent phospholipase A(2) group VIA (iPLA(2)β) releases docosahexaenoic acid (DHA) from phospholipids in vitro. Mutations in the iPLA(2)β gene, PLA2G6, are associated with dystonia-parkinsonism and infantile neuroaxonal dystrophy. To understand the role of iPLA(2)β in brain, we applied our in vivo kinetic method using radiolabeled DHA in 4 to 5-month-old wild type (iPLA(2)β(+/+)) and knockout (iPLA(2)β(-/-)) mice, and measured brain DHA kinetics, lipid concentrations, and expression of PLA(2), cyclooxygenase (COX), and lipoxygenase (LOX) enzymes. Compared to iPLA(2)β(+/+) mice, iPLA(2)β(-/-) mice showed decreased rates of incorporation of unesterified DHA from plasma into brain phospholipids, reduced concentrations of several fatty acids (including DHA) esterified in ethanolamine- and serine-glycerophospholipids, and increased lysophospholipid fatty acid concentrations. DHA turnover in brain phospholipids did not differ between genotypes. In iPLA(2)β(-/-) mice, brain levels of iPLA(2)β mRNA, protein, and activity were decreased, as was the iPLA(2)γ (Group VIB PLA(2)) mRNA level, while levels of secretory sPLA(2)-V mRNA, protein, and activity and cytosolic cPLA(2)-IVA mRNA were increased. Levels of COX-1 protein were decreased in brain, while COX-2 protein and mRNA were increased. Levels of 5-, 12-, and 15-LOX proteins did not differ significantly between genotypes. Thus, a genetic iPLA(2)β deficiency in mice is associated with reduced DHA metabolism, profound changes in lipid-metabolizing enzyme expression (demonstrating lack of redundancy) and of phospholipid fatty acid content of brain (particularly of DHA), which may be relevant to neurologic abnormalities in humans with PLA2G6 mutations.  相似文献   
84.
Polyunsaturated fatty acids (PUFA), especially docosahexaenoic and arachidonic acids, as well as cholesterol are important for neural development and maintaining brain function. However, in contrast to cholesterol, the brain is unable to synthesize the required amounts of these PUFA de novo and requires a constant supply from plasma. Suggested pools of uptake include plasma unesterified PUFA or the uptake of PUFA-containing lipoproteins via lipoprotein receptors into endothelial cells of the blood brain barrier. Our study tested whether the very low density lipoprotein receptor (VLDLr) is necessary for maintaining brain PUFA and cholesterol concentrations. Moreover, since VLDLr knockout (VLDLr?/?) mice have been reported to have behavioural deficits, this study asked the question whether altered brain PUFA and cholesterol concentrations might be related to these deficits. VLDLr?/? and wild-type mice had ad libitum access to chow. At 7 weeks of age the mice were sacrificed, and the cortex, cerebellum, hippocampus, and the remainder of the brain were isolated for total fatty acid and cholesterol analyses. There were no differences in total lipid PUFA or cholesterol concentrations in any of the four brain regions between VLDLr?/? and wild-type mice. These findings demonstrate that the VLDLr is not necessary for maintaining brain PUFA concentrations and suggest that other mechanisms to transport PUFA into the brain must exist.  相似文献   
85.
The reemergence of infectious diseases and the continuous development of multidrug resistance among a variety of disease-causing bacteria in clinical setting pose a serious threat to public health worldwide. Extended-spectrum β-lactamases (ESBLs) that mediate resistance to third-generation cephalosporin are now observed all over the world in all species of Enterobacteriaceae, especially Escherichia coli and Klebsiella pneumoniae. In this work, ZnO nanoparticles (NPs) were synthesized by the sol–gel method and characterized by powder X-ray diffraction, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The image of synthesized ZnO NPs appeared spherical in SEM with a diameter of ≈19 nm and as hexagonal crystal in AFM. Clinical isolates were assessed for ESBL production and shown to be sensitive to ZnO NPs by different methods such as minimal inhibitory concentration (MIC) and minimal bactericidal concentration, time-dependent growth inhibition assay, well diffusion agar methods and estimation of colony forming units (CFU) of bacteria. The lowest MIC value for E. coli and K. pneumoniae was found to be 500 μg/ml. The results showed that ZnO NPs at 1,000 μg/ml completely inhibit the bacterial growth. The antibacterial effect of ZnO nanoparticles was gradual, but time- and concentration-dependent. The maximum inhibition zone at100 μg/ml for E. coli and K. pneumoniae was 22 and 20 mm, respectively. With the increasing ZnO NP loading, there is significant reduction in the numbers of CFU. At the concentration of 1,000 μg/ml, the decline in per cent survival of E. coli and K. pneumoniae was found to be 99.3% and 98.6%, respectively.  相似文献   
86.
Cluster bean (Cyamopsis tetragonoloba L.) yield has plateaued due to reduction in rainfall and rise in temperature. Therefore, its production cycle could not get appropriate water and temperature. It becomes important to standardize the sowing time and plant spacing of cluster beans in changing climate scenarios to get higher productivity. Therefore, a field study was conducted in 2019 at the Research area of MNS-University of Agriculture, Multan, Pakistan to evaluate the effect of four sowing times (15th May, 1st June, 15th June, and 1st July) and three plant spacings (10, 12 and 15 cm) on crop growth, yield, and physiological functions of cluster bean genotype BR-2017 under split plot arrangement under randomized complete block design (RCBD) with three replications. The sowing times (15th May, 1st June, 15th June, and 1st July) were placed in the main plot, while plant spacing (10, 12 and 15 cm) was maintained in subplots. The significant effect of sowing time and plant spacing was observed on pod plant−1, pod length, grain yield, and 1000-grain weight. Results showed that 1st June sowing performed better over 15th May, 15th June, and 1st July, while plant spacing 15 cm about in all sowing times showed higher results on growth and yield parameters of cluster bean over plant spacing 10, 12, and 15 cm. The 1st June sowing time at 15 cm plant spacing showed 8.0, 22.7, and 28.5% higher grains pod-1 than 15th May, 15th June, and 1st July sowing, respectively. Maximum grain yield was observed on 1st June in all three spacings (10, 12, and 15 cm). The chord diagram indicates that the crop has received optimum environmental conditions when sown 1st June over other sowing times. In conclusion, 1st June sowing with 15 cm plant spacing could be a good option to achieve maximum productivity of cluster bean under changing climate scenario.  相似文献   
87.
88.
Spatial priorities for the conservation of three key Mediterranean habitats, i.e. seagrass Posidonia oceanica meadows, coralligenous formations, and marine caves, were determined through a systematic planning approach. Available information on the distribution of these habitats across the entire Mediterranean Sea was compiled to produce basin-scale distribution maps. Conservation targets for each habitat type were set according to European Union guidelines. Surrogates were used to estimate the spatial variation of opportunity cost for commercial, non-commercial fishing, and aquaculture. Marxan conservation planning software was used to evaluate the comparative utility of two planning scenarios: (a) a whole-basin scenario, referring to selection of priority areas across the whole Mediterranean Sea, and (b) an ecoregional scenario, in which priority areas were selected within eight predefined ecoregions. Although both scenarios required approximately the same total area to be protected in order to achieve conservation targets, the opportunity cost differed between them. The whole-basin scenario yielded a lower opportunity cost, but the Alboran Sea ecoregion was not represented and priority areas were predominantly located in the Ionian, Aegean, and Adriatic Seas. In comparison, the ecoregional scenario resulted in a higher representation of ecoregions and a more even distribution of priority areas, albeit with a higher opportunity cost. We suggest that planning at the ecoregional level ensures better representativeness of the selected conservation features and adequate protection of species, functional, and genetic diversity across the basin. While there are several initiatives that identify priority areas in the Mediterranean Sea, our approach is novel as it combines three issues: (a) it is based on the distribution of habitats and not species, which was rarely the case in previous efforts, (b) it considers spatial variability of cost throughout this socioeconomically heterogeneous basin, and (c) it adopts ecoregions as the most appropriate level for large-scale planning.  相似文献   
89.
While the novel Middle East respiratory syndrome coronavirus (MERS-CoV) is closely related to Tylonycteris bat CoV HKU4 (Ty-BatCoV HKU4) and Pipistrellus bat CoV HKU5 (Pi-BatCoV HKU5) in bats from Hong Kong, and other potential lineage C betacoronaviruses in bats from Africa, Europe, and America, its animal origin remains obscure. To better understand the role of bats in its origin, we examined the molecular epidemiology and evolution of lineage C betacoronaviruses among bats. Ty-BatCoV HKU4 and Pi-BatCoV HKU5 were detected in 29% and 25% of alimentary samples from lesser bamboo bat (Tylonycteris pachypus) and Japanese pipistrelle (Pipistrellus abramus), respectively. Sequencing of their RNA polymerase (RdRp), spike (S), and nucleocapsid (N) genes revealed that MERS-CoV is more closely related to Pi-BatCoV HKU5 in RdRp (92.1% to 92.3% amino acid [aa] identity) but is more closely related to Ty-BatCoV HKU4 in S (66.8% to 67.4% aa identity) and N (71.9% to 72.3% aa identity). Although both viruses were under purifying selection, the S of Pi-BatCoV HKU5 displayed marked sequence polymorphisms and more positively selected sites than that of Ty-BatCoV HKU4, suggesting that Pi-BatCoV HKU5 may generate variants to occupy new ecological niches along with its host in diverse habitats. Molecular clock analysis showed that they diverged from a common ancestor with MERS-CoV at least several centuries ago. Although MERS-CoV may have diverged from potential lineage C betacoronaviruses in European bats more recently, these bat viruses were unlikely to be the direct ancestor of MERS-CoV. Intensive surveillance for lineage C betaCoVs in Pipistrellus and related bats with diverse habitats and other animals in the Middle East may fill the evolutionary gap.  相似文献   
90.
ABSTRACT: BACKGROUND: Glioblastoma Multiforme (GBM) is one of the most aggressive primary brain tumors and is associated with a dismal prognosis. The median survival after the primary diagnosis remains poor, even after multimodal treatment approaches. However, a few patients have been reported to have long term survival greater than three years. A number of studies have attempted to define factors capable of predicting long term outcomes in specific patient groups. This article reports the outcomes of a very large group of patients diagnosed with GBM, and analyzes specific prognostic factors known to influence survival in these patients. METHODS: We used the Surveillance, Epidemiology, and End Results (SEER) database of the US National Cancer Institute (NCI) to investigate various patient-related and treatment- related factors that could influence the long term survival in patients diagnosed with glioblastoma. A total of 34,664 patients aged 20 years or older with a diagnosis of GBM during the years 1973 to 2008 were studied. Overall survival outcomes were examined with Kaplan-Meier survival analysis and Cox hazard models. RESULTS: Asian/Pacific Islanders had a better survival compared to the white population (P = <0.001). Patients diagnosed with GBM during the years 2000 to 2008 had a superior survival rate when compared with earlier decades (P = <0 .001). Statistically significant improvements in overall survival were also found for patients who received surgical resections, and adjuvant radiation treatment versus no radiation (P-values <0.001). Young age was also found to be highly predictive of improved overall survival rates when separated into age groups as well as when studied as a continuous variable. CONCLUSIONS: Clinical pretreatment and treatment factors, including young age at diagnosis, Asian/Pacific Islander ethnicity, recent year of diagnosis, surgical resection and the use of adjuvant radiation therapy favorably influence survival in patients diagnosed with glioblastoma. Trial Registration All data were obtained from the United States Surveillance Epidemiology and End Results (SEER) database.  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