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   162篇
  免费   75篇
  国内免费   3篇
儿科学   1篇
妇产科学   1篇
基础医学   39篇
临床医学   7篇
内科学   9篇
神经病学   2篇
特种医学   4篇
外科学   4篇
综合类   8篇
现状与发展   1篇
预防医学   19篇
药学   136篇
中国医学   7篇
肿瘤学   2篇
  2023年   3篇
  2022年   11篇
  2021年   15篇
  2020年   18篇
  2019年   16篇
  2018年   15篇
  2017年   2篇
  2016年   4篇
  2015年   12篇
  2014年   19篇
  2013年   13篇
  2012年   19篇
  2011年   12篇
  2010年   11篇
  2009年   7篇
  2008年   3篇
  2007年   15篇
  2006年   10篇
  2004年   4篇
  2003年   1篇
  2002年   4篇
  2001年   7篇
  2000年   3篇
  1999年   1篇
  1998年   1篇
  1997年   3篇
  1996年   3篇
  1995年   1篇
  1993年   3篇
  1992年   1篇
  1987年   1篇
  1984年   1篇
  1981年   1篇
排序方式: 共有240条查询结果,搜索用时 15 毫秒
1.
《Vaccine》2022,40(48):6947-6955
BackgroundHuman papillomavirus (HPV) infections were the main cause of anogenital cancers and warts. HPV 6/11/16/18 vaccines provide protection against the high-risk types of HPV responsible for 70% of cervical cancers and 90% of genital warts. This randomized, blinded, non-inferiority phase III trial was to determine whether immunogenicity and tolerability would be non-inferior among women after receiving two novel 4- and 9-valent HPV vaccines (4vHPV, HPV 6/11/16/18; 9vHPV, HPV 6/11/16/18/31/33/45/52/58) compared with those receiving Gardasil 4 (4-valent).Methods1680 females between 20 and 45 years were randomized in a 2:1:1 ratio to 20–26, 27–35, or 36–45 y groups. Subjects then equally assigned to receive 4vHPV, 9vHPV or Gardasil 4 (control) vaccine at months 0, 2, and 6. End points included non-inferiority of HPV-6/11/16/18 antibodies for 4vHPV versus control, and 9vHPV versus control and safety. The immunogenicity non-inferiority was pre-defined as the lower bound of 95% confidence interval (CI) of seroconversion rate (SCR) difference > ?10% and the lower bound of 95% CI of geometric mean antibody titer (GMT) ratio > 0.5.ResultsAmong the three vaccine groups, more than 99% of the participants seroconverted to all 4 HPV types. The pre-specified statistical non-inferiority criterion for the immunogenicity hypothesis was met: all the lower bounds of 95% CIs on SCR differences exceeded ?10% for each vaccine HPV type and the corresponding lower bounds of 95% CIs for GMT ratios > 0.5. Across vaccination groups, the most common vaccination reaction were injection-site adverse events (AEs), including pain, swelling, and redness. General and serious AEs were similar in the three groups. There were no deaths.ConclusionsThis study demonstrated that the novel 4- and 9-valent HPV vaccination was highly immunogenic and generally well tolerated, both of which were non-inferior to Gardasil 4 in immunogenicity and safety.  相似文献   
2.
《Vaccine》2014,32(52):7091-7097
Influenza vaccine production using cell culture technology has become popular nowadays. However, to meet the ever increasing demand of influenza vaccine, it is prerequisite to improve the yield of influenza virus in cells. To achieve this, in the present study, the nutritional requirements of MDCK cells in the virus production process were analyzed and a nutrient-feeding strategy was developed accordingly. Based on the consumption rates and corresponding concentration optimization, glucose and fast metabolized amino acids were supplemented into the maintaining medium at the time of infection. Compared with the non-supplemented culture, the average cell specific death rate during 0–48 h post-infection was 0.013 h−1, which was 40.91% lower in the nutrient-supplemented culture. Total virus titer, HA antigen protein concentration and cell-specific virus yield were (1.88 ± 0.23) × 103 HA units/50 μL, 11.70 ± 0.22 μg/mL and (10.06 ± 1.16) × 103 virions/cell, respectively, which were 84.04 ± 22.50%, 31.46 ± 2.87% and 86.64 ± 25.81% higher than those in the control, respectively. These data showed that the appropriate supplementation of nutrients during virus production process could reduce cell death, and improve cell-specific virus yield and total influenza virus output. This study laid foundation for the development of cell culture technology for influenza vaccine production.  相似文献   
3.
Dan Zheng  Yinglei Yi  Ze Chen 《Viruses》2012,4(12):3589-3605
Several global outbreaks of highly pathogenic avian influenza (HPAI) H5N1 virus have increased the urgency of developing effective and safe vaccines against H5N1. Compared with H5N1 inactivated vaccines used widely, H5N1 live-attenuated influenza vaccines (LAIVs) have advantages in vaccine efficacy, dose-saving formula, long-lasting effect, ease of administration and some cross-protective immunity. Furthermore, H5N1 LAIVs induce both humoral and cellular immune responses, especially including improved IgA production at the mucosa. The current trend of H5N1 LAIVs development is toward cold-adapted, temperature-sensitive or replication-defective vaccines, and moreover, H5N1 LAIVs plus mucosal adjuvants are promising candidates. This review provides an update on the advantages and development of H5N1 live-attenuated influenza vaccines.  相似文献   
4.
The safety of steviol glycoside sweeteners has been extensively reviewed in the literature. National and international food safety agencies and approximately 20 expert panels have concluded that steviol glycosides, including the widely used sweeteners stevioside and rebaudioside A, are not genotoxic. However, concern has been expressed in recent publications that steviol glycosides may be mutagenic based on select studies representing a small fraction of the overall database, and it has been suggested that further in vivo genotoxicity studies are required to complete their safety profiles. To address the utility of conducting additional in vivo genotoxicity studies, this review evaluates the specific genotoxicity studies that are the sources of concern, and evaluates the adequacy of the database including more recent genotoxicity data not mentioned in those publications. The current database of in vitro and in vivo studies for steviol glycosides is robust and does not indicate that either stevioside or rebaudioside A are genotoxic. This, combined with a lack of evidence for neoplasm development in rat bioassays, establish the safety of all steviol glycosides with respect to their genotoxic/carcinogenic potential.  相似文献   
5.
IFN-α/β是机体对抗外来病原体的第一道防线,其产生和后续激活的细胞信号转导可诱导具有抑制病毒感染和复制作用的IFN刺激基因的表达。然而,大多数病毒可通过表达一种或多种蛋白抵抗宿主细胞的抗病毒反应。流感病毒非结构蛋白1(nonstructural protein 1,NS1)作为多功能毒力因子,在流感病毒感染过程中起重要作用。此文概述了NS1的结构与功能及抑制IFN-α/β产生和抗病毒效应作用的机制,为研究流感病毒致病机理提供参考。  相似文献   
6.
目的 观察乙型脑炎(乙脑)减毒活疫苗的接种反应和免疫原性.方法 分别选择52名(8月龄~50岁)和607名(8月龄~12岁)健康志愿者进行Ⅰ和Ⅲ期临床试验.试验组每人接种1次由上海生物制品研究所有限责任公司研制的乙脑减毒活疫苗(0.5 ml),对照组接种同样剂量的已上市乙脑减毒活疫苗.两组接种后的不良反应率和中和抗体阳转率用x2检验进行比较,中和抗体几何平均滴度用t检验进行比较.结果 试验组接种后有5.91%的人体温升高,对照组为7.96%,两组的体温反应发生率差异无统计学意义(x^2 =0.917,P=0.338).试验组Ⅰ期试验局部反应率为1.92%,Ⅲ期试验为0.25%,对照组Ⅲ期试验局部反应率为0.50%,两组的局部反应率差异无统计学意义(确切概率法,P=0.553).Ⅲ期免疫原性试验中,试验组的血清中和抗体阳转率为89.00%,抗体几何平均滴度为29.69;而对照组分别为74.59%和19.25,差异均有统计学意义(x^2=11.708,P=0.001;t=4.281,P=0.001).结论 本研究的试验性乙脑减毒活疫苗接种反应轻微,并具有良好的免疫原性.  相似文献   
7.
目的  对皮内注射用卡介苗(卡介苗)关键质量指标进行关联性分析,为生产工艺控制提供一定的依据。方法  用统计软件(Minitab 17和SPSSAU)对211批卡介苗的菌种代次、半成品沉降率、半成品活菌数、成品活菌数、成品效力和成品渗透压摩尔浓度等关键质量指标进行统计分析,探寻各指标间相互影响的规律。结果  第6、9和12代卡介菌生产的卡介苗成品活菌数均值分别为5.07×106、5.49×106和6.02×106 菌落形成单位(colony-forming unit,CFU)/mg,Pearson相关系数为0.200(P<0.05),成品活菌数随卡介苗生产用菌种代次的升高而略有增加。半成品沉降率处于0.00%~7.99%、8.00%~12.00%和12.00%~20.00%的卡介苗成品活菌数均值分别为5.57×106、5.52×106和5.06×106 CFU/mg,Pearson相关系数为-0.182(P<0.05),成品活菌数随半成品沉降率提高而略有降低。半成品活菌数处于1.00×107~1.99×107、2.00×107~2.99×107和3.00×107~4.00×107 CFU/mg的卡介苗成品活菌数均值分别为4.61×106、5.69×106和6.53×106 CFU/mg,Pearson相关系数为0.537(P<0.05),成品活菌数随半成品活菌数增加而显著增加。成品活菌数处于1.00×106~3.99×106、4.00×106~5.99×106和6.00×106~8.00×106 CFU/mg的卡介苗成品效力均值分别为17.61、16.51和16.55 mm,Pearson相关系数为-0.187(P<0.05),成品效力随成品活菌数增加而先略有降低再趋于平稳。成品活菌数处于1.00×106~3.99×106、4.00×106~5.99×106和6.00×106~8.00×106  CFU/mg的卡介苗成品渗透压摩尔浓度均值分别为363.61、363.21和368.68 mOsmol/kg,Pearson相关系数为0.210(P<0.05),成品渗透压摩尔浓度随着成品活菌数增加而略有升高。结论  在企业标准范围内,成品活菌数受半成品活菌数的影响较大,受菌种代次、半成品沉降率的影响较小。成品活菌数对成品效力和成品渗透压摩尔浓度的影响较小。  相似文献   
8.
目的 用响应面法对马来酰亚胺活化相对分子质量40 000的聚乙二醇(polyethylene glycol,PEG)(MAL-PEG40K)修饰胰高血糖素样肽1类似物(glucagon-like peptide-1 analog,GLP-1a)的反应条件进行优化。方法 对GLP-1a浓度、GLP-1a/MAL-PEG40K摩尔比、反应液pH值、反应温度、反应时长进行单因素试验。以前3个条件为自变量, PEG修饰率为响应值,根据中心组合试验设计原理,研究各自变量及其交互作用对PEG修饰率的影响。通过高效液相色谱法分析PEG修饰率,依据回归分析确定各反应条件的最优值。 结果 GLP-1a与MAL-PEG40K的最佳反应条件为:GLP-1a浓度2.5 mg/ml,GLP-1a/MAL-PEG40K摩尔比1∶1.25,反应液pH 8,反应温度4 ℃,反应时长60 min。该优化条件下,GLP-1a的PEG修饰率可达91.0%。结论 响应面法获得了GLP-1a与MAL-PEG40K的最佳反应条件。  相似文献   
9.
器官移植受者术后易于感染许多疫苗可预防疾病,存在预后不良的风险,甚至可因严重感染而威胁生命。接种麻疹、腮腺炎、风疹(麻腮风)系列疫苗能有效降低器官移植受者术后的麻疹、腮腺炎和风疹发病率。此文综述了器官移植受者接种麻腮风系列疫苗的有效性和安全性,以期为器官移植受者制定个性化麻腮风系列疫苗免疫接种程序提供参考。  相似文献   
10.
Optically pure epoxides are essential chiral precursors for the production of (S)-propranolol, (S)-alprenolol, and other β-adrenergic receptor blocking drugs. Although the enzymatic production of these bulky epoxides has proven difficult, here we report a method to effectively improve the activity of BmEH, an epoxide hydrolase from Bacillus megaterium ECU1001 toward α-naphthyl glycidyl ether, the precursor of (S)-propranolol, by eliminating the steric hindrance near the potential product-release site. Using X-ray crystallography, mass spectrum, and molecular dynamics calculations, we have identified an active tunnel for substrate access and product release of this enzyme. The crystal structures revealed that there is an independent product-release site in BmEH that was not included in other reported epoxide hydrolase structures. By alanine scanning, two mutants, F128A and M145A, targeted to expand the potential product-release site displayed 42 and 25 times higher activities toward α-naphthyl glycidyl ether than the wild-type enzyme, respectively. These results show great promise for structure-based rational design in improving the catalytic efficiency of industrial enzymes for bulky substrates.Optically pure epoxides and the corresponding vicinal diols are valuable chiral building blocks for the production of pharmaceutically active compounds and other fine chemicals (1). Existing approaches for preparing enantiopure epoxides and diols include the asymmetric epoxidation or dihydroxylation of olefin substrates and the resolution of racemic epoxides. These reactions can be accomplished with either chemical catalysts such as chiral salen cobalt complexes and porphyrin manganese adducts or biocatalysts such as monooxygenases and epoxide hydrolases (EHs) (24). In the past two decades, EHs have received much attention because they are cofactor-independent enzymes that are “easy to use” for catalyzing the hydrolysis of racemic epoxides to yield highly enantiopure epoxides and vicinal diols (1, 5, 6). However, application of EHs in laboratory and industry was often hindered by their narrow substrate scope, low enantioselectivity, and regioselectivity, or product inhibition (7, 8).Many protein-engineering efforts have been made to overcome these drawbacks (9, 10). For example, directed evolution by error-prone PCR or DNA shuffling has been used to enhance the activity and enantioselectivity of EHs (1113). Structure-guided mutagenesis also generated a few EH variants with improved catalytic performance (1416). The strategy of iterative Combinatorial Active Site-Saturation Test (CAST) combines the rational approach and directed evolution to yield high-quality and small focused mutant libraries for screening EHs with better enantioselectivity (7, 17). By mutating residues at the substrate-binding site, the substrates of EHs have been expanded to include cyclic meso-epoxides, phenyl glycidyl ether (PGE) derivatives, and other styrene oxide-like analogs (18, 19). However, the catalytic efficiency of EH is still not satisfactory for bulky epoxide substrates including precursors of (S)-propranolol, (S)-alprenolol, and other β-adrenergic receptor blocking drugs (20, 21).In this work, we select BmEH, an EH cloned from Bacillus megaterium ECU1001, to expand its substrate scope for bulky pharmaco substrate α-naphthyl glycidyl ether (NGE). This enzyme is a potential industrial biocatalyst because it has unusual (R)-enantioselectivity and resolves ortho-substituted PGEs and para-nitrostyrene oxide with excellent enantiomeric ratios (E > 200) (22). We first identified the active tunnel of BmEH by solving its crystal structure complexed with a substrate analog phenoxyacetamide (POA) and analyzing the routes of substrate entry and product release by mass spectrum analysis. Alanine scanning experiments targeted to the potential product-release site of BmEH resulted in two variants, F128A and M145A, with efficient bioresolution abilities on NGE. Further kinetic measurements and structural analysis showed that M145A has much higher activity for the transition state intermediate formation, whereas both mutants exhibited expanded product-release site. The M145A BmEH variant has been successfully applied for the preparation of (S)-propranolol on a gram scale. The engineering of the potential product-release site described herein should have great promise for structure-based rational design of better industrial enzymes.  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