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   145篇
  免费   5篇
  150篇
  2024年   1篇
  2023年   3篇
  2022年   7篇
  2021年   4篇
  2020年   5篇
  2018年   5篇
  2017年   3篇
  2016年   5篇
  2015年   16篇
  2014年   12篇
  2013年   16篇
  2012年   6篇
  2011年   4篇
  2010年   12篇
  2009年   7篇
  2008年   3篇
  2007年   3篇
  2006年   5篇
  2005年   9篇
  2004年   4篇
  2003年   4篇
  2001年   1篇
  1999年   1篇
  1997年   2篇
  1994年   2篇
  1990年   1篇
  1988年   3篇
  1987年   2篇
  1986年   1篇
  1975年   1篇
  1974年   1篇
  1971年   1篇
排序方式: 共有150条查询结果,搜索用时 0 毫秒
101.
In addition to apigenin, apigenin 7-O-glucoside, kaempferol 3-O-glucoside, kaempferol 3,7-di-O-rhamnoside, quercetin, and quercetin 3-O-glucoside, the methanolic extract of Fagonia taeckholmiana afforded a new compound identified as kaempferol 3-O-beta-l-arabinopyranosyl-(1-->4)-alpha-l-rhamnopyranoside-7-O-alpha-l-rhamnopyranoside. Identification of the isolated compounds was based on chemical and spectroscopic analyses including UV, FABMS, (1)H, (13)C and 2D NMR, and DEPT. The cytotoxic activities of the compounds against several cancer cell lines were determined.  相似文献   
102.
103.
BackgroundAtrial fibrillation (AF) is an important risk factor for ischaemic stroke, and AF incidence is expected to increase. Guidelines recommend using oral anticoagulants (OACs) to prevent the development of stroke. However, studies have reported the frequent underuse of OACs in AF patients. The objective of this study is to describe nonvalvular atrial fibrillation (NVAF) incidence in England and assess the clinical and socioeconomic factors associated with the underprescribing of OACs.Methods and findingsWe conducted a population-based retrospective cohort study using the UK Clinical Practice Research Datalink (CPRD) database to identify patients with NVAF aged ≥18 years and registered in English general practices between 2009 and 2019. Annual incidence rate of NVAF by age, deprivation quintile, and region was estimated. OAC prescribing status was explored for patients at risk for stroke and classified into the following: OAC, aspirin only, or no treatment. We used a multivariable multinomial logistic regression model to estimate relative risk ratios (RRRs) and 95% confidence intervals (CIs) of the factors associated with OAC or aspirin-only prescribing compared to no treatment in patients with NVAF who are recommended to take OAC. The multivariable regression was adjusted for age, sex, comorbidities, socioeconomic status, baseline treatment, frailty, bleeding risk factors, and takes into account clustering by general practice. Between 2009 and 2019, 12,517,191 patients met the criteria for being at risk of developing NVAF. After a median follow-up of 4.6 years, 192,265 patients had an incident NVAF contributing a total of 647,876 person-years (PYR) of follow-up. The overall age-adjusted incidence of NVAF per 10,000 PYR increased from 20.8 (95% CI: 20.4; 21.1) in 2009 to 25.5 (25.1; 25.9) in 2019. Higher incidence rates were observed for older ages and males. Among NVAF patients eligible for anticoagulation, OAC prescribing rose from 59.8% (95% CI: 59.0; 60.6) in 2009 to 83.2% (95% CI: 83.0; 83.4) in 2019. Several conditions were associated with lower risk of OAC prescribing: dementia [RRR 0.52 (0.47; 0.59)], liver disease 0.58 (0.50; 0.67), malignancy 0.74 (0.72; 0.77), and history of falls 0.82 (0.78; 0.85). Compared to white ethnicity, patients from black and other ethnic minorities were less likely to receive OAC; 0.78 (0.65; 0.94) and 0.76 (0.64; 0.91), respectively. Patients living in the most deprived areas were less likely to receive OAC 0.85 (0.79; 0.91) than patients living in the least deprived areas. Practices located in the East of England were associated with higher risk of prescribing aspirin only over no treatment than practices in London (RRR 1.22; 95% CI 1.02 to 1.45). The main limitation of this study is that these findings depends on accurate recording of conditions by health professionals and the inevitable residual confounding due to lack of data on certain factors that could be associated with under-prescribing of OACs.ConclusionsThe incidence of NVAF increased between 2009 and 2015, before plateauing. Underprescribing of OACs in NVAF is associated with a range of comorbidities, ethnicity, and socioeconomic factors, demonstrating the need for initiatives to reduce inequalities in the care for AF patients.

Alyaa Ajabnoor and co-workers study incidence of non-valvular atrial fibrillation in England and apparent inequalities in care.  相似文献   
104.
Introduction: Praziquantel (PZQ) is the only commercially available drug for schistosomiasis. The current shortage of alternative effective drugs and the lack of successful preventive measures enhance its value. The increase in the prevalence of PZQ resistance under sustained drug pressure is, therefore, an upcoming issue.Objective: To overcome the tolerance to PZQ using nanotechnology after laboratory induction of a Schistosoma mansoni isolate with reduced sensitivity to the drug during the intramolluscan phase.Materials and methods: Shedding snails were treated with PZQ doses of 200 mg/kg twice/ week followed by an interval of one week and then repeated twice in the same manner. The success of inducing reduced sensitivity was confirmed in vitro via the reduction of cercarial response to PZQ regarding their swimming activity and death percentage at different examination times.Results: Oral treatment with a single PZQ dose of 500 mg/kg in mice infected with cercariae with reduced sensitivity to PZQ revealed a non-significant reduction (35.1%) of total worm burden compared to non-treated control mice. Orally inoculated PZQ- encapsulated niosomes against S. mansoni with reduced sensitivity to PZQ successfully regained the pathogen’s sensitivity to PZQ as evidenced by measuring different parameters in comparison to the non-treated infected animals with parasites with reduced sensitivity to PZQ. The mean total worm load was 1.33 ± 0.52 with a statistically significant reduction of 94.09% and complete eradication of male worms. We obtained a remarkable increase in the percentage reduction of tissue egg counts in the liver and intestine (97.68% and 98.56%, respectively) associated with a massive increase in dead eggs and the complete absence of immature stages.Conclusion: PZQ-encapsulated niosomes restored the drug sensitivity against laboratory- induced S. mansoni adult worms with reduced sensitivity to PZQ.  相似文献   
105.
Six flavonoid glycosides: quercetin 3-glucoside, quercetin-3-rutinoside; 3-glucoside, 3-rutinoside, 3-7-diglucoside and 3-rhamnogalactoside of isorhamnetin were extracted and identified from the leaves and branches of Egyptian material ofBalanites aegyptiaca. Only isorhamnetin: 3-rutinoside and 3-rhamnogalactoside were recorded from the fruits of the same plant.—Phytochemical aspects ofBalanites aegyptiaca and some genera ofZygophylaceae s. l. viz.Nitraria, Fagonia, Zygophyllum, Seetzenia andTribulus support its affinities with that family.  相似文献   
106.
Background and Aims Date palms (Phoenix dactylifera, Arecaceae) are of great economic and ecological value to the oasis agriculture of arid and semi-arid areas. However, despite the availability of a large date palm germplasm spreading from the Atlantic shores to Southern Asia, improvement of the species is being hampered by a lack of information on global genetic diversity and population structure. In order to contribute to the varietal improvement of date palms and to provide new insights on the influence of geographic origins and human activity on the genetic structure of the date palm, this study analysed the diversity of the species.Methods Genetic diversity levels and population genetic structure were investigated through the genotyping of a collection of 295 date palm accessions ranging from Mauritania to Pakistan using a set of 18 simple sequence repeat (SSR) markers and a plastid minisatellite.Key Results Using a Bayesian clustering approach, the date palm genotypes can be structured into two different gene pools: the first, termed the Eastern pool, consists of accessions from Asia and Djibouti, whilst the second, termed the Western pool, consists of accessions from Africa. These results confirm the existence of two ancient gene pools that have contributed to the current date palm diversity. The presence of admixed genotypes is also noted, which points at gene flows between eastern and western origins, mostly from east to west, following a human-mediated diffusion of the species.Conclusions This study assesses the distribution and level of genetic diversity of accessible date palm resources, provides new insights on the geographic origins and genetic history of the cultivated component of this species, and confirms the existence of at least two domestication origins. Furthermore, the strong genetic structure clearly established here is a prerequisite for any breeding programme exploiting the effective polymorphism related to each gene pool.  相似文献   
107.
A novel, simple and sensitive spectrofluorimetric approach for determination of terbutaline sulphate (TER) and its prodrug bambuterol (BAM) in their pure and pharmaceutical dosage forms was developed. The suggested approach depends on enhancing the native fluorescence of either TER or BAM at 315 and 297.2 nm after excitation at 277 and 259 nm, respectively, using sodium dodecyl sulphate (SDS) as a micellar medium. In the presence of 0.7% w/v SDS, ~1.38-fold and 1.18-fold enhancement is achieved in the relative fluorescence intensity (RFI) of TER and BAM, respectively. The fluorescence–concentration curves were rectilinear over the concentration range 0.8–16 μg ml−1, with detection limits (LOD) of 0.252 and 0.26 (μg ml−1), quantitation limits (LOQ) of 0.76 and 0.79 (μg ml−1), determination coefficients (r2) of 0.9981, and slopes of 45.92 and 10.44 for TER and BAM, respectively. The suggested approach was validated in accordance with International Council for Harmonisation criteria and was effectively applied in the analysis of the studied drugs in their commercial tablets. The high sensitivity of the proposed approach allows its application in evaluating the content uniformity testing of the studied drugs in their tablets through using the official United States Pharmacopeia criteria. Statistical analogies of the findings with that of the reported methods showed really good harmony and indicated no major differences in precision and accuracy.  相似文献   
108.
109.
The plasmid profile of two thermophilic bacterial strains isolated from recreation thermal springs in Jordan has been investigated. These strains are Streptococcus thermophilus and Bacillus sp1, which have been isolated from Zerka – Maeen and Himma hot springs respectively. Supercoiled and circular plasmid forms were detected, explaining the effect of DNA conformation on the mobility of the plasmid in the agarose gel electrophoresis. Two plasmids have been isolated and characterized by restriction endonucleases to facilitate their use as cloning vectors in thermophilic strains. The sizes of the plasmids were approximately 3 kb (from Streptococcus thermophilus) and 7 kb (from Bacillus spl). These plasmids were then digested with three different restriction enzymes (EcoRI, Bam HI, and HindIII), one of which was found to possess a single site for both plasmids, this enzyme is EcoRI.  相似文献   
110.
Laboratory detection of Brucella is based largely on bacterial isolation and phenotypic characterization. These methods are lengthy and labor-intensive and have been associated with a heightened risk of laboratory-acquired infection. Antibody based indirect detection methods also suffer from limitations in proper diagnosis of the organism. To overcome these problems, nucleic acid amplification has been explored for rapid detection and confirmation of the presence of Brucella spp. PCR-based diagnostics is useful for screening large populations of livestock to identify infected individuals and confirms the presence of the pathogen. Random Amplification of Polymorphic DNA (RAPD) was performed and identified a 1.3 kb PCR fragment specifically amplifiable from DNA isolated from Brucella. A BLAST search revealed no significant homology with the reported sequences from species other than the members of Brucella. The isolated fragment seems to be a part of d-alanine–d-alanine ligase gene in Brucella sp. Translational BLAST revealed certain degree of homology of this sequence with orthologs of this gene reported from other microbial species at the deduced amino acid level. The sequence information was used to develop PCR based assays to detect Brucella sp. from various samples. The minimum detection limit of Brucella from blood and milk samples spiked with Brucella DNA was found to be 1 ng/ml and 10 ng/ml, respectively. In conclusion, we demonstrated that the PCR based detection protocol was successfully used for the detection of Brucella from various organs and spiked samples of diseased sheep. Diagnosis of Brucellosis by PCR based method reported in this study is relatively rapid, specific and simple.  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