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   203篇
  免费   32篇
  国内免费   59篇
基础医学   3篇
临床医学   4篇
内科学   2篇
神经病学   1篇
外科学   2篇
综合类   20篇
预防医学   5篇
药学   33篇
中国医学   224篇
  2024年   3篇
  2023年   9篇
  2022年   5篇
  2021年   7篇
  2020年   13篇
  2019年   22篇
  2018年   5篇
  2017年   22篇
  2016年   21篇
  2015年   18篇
  2014年   31篇
  2013年   41篇
  2012年   33篇
  2011年   32篇
  2010年   17篇
  2009年   9篇
  2003年   2篇
  1997年   1篇
  1995年   2篇
  1993年   1篇
排序方式: 共有294条查询结果,搜索用时 15 毫秒
1.
降香为我国传统中药材,历代本草对其记载较为混杂,至今基原仍存在较大争议。从名称、基原、产地、品质评价、采收加工及炮制方面进行考证可知,降香本名降真香,历代本草中多以降真香为正名记载,自明代《本草纲目》将降香作为降真香的简称,后至清末、民国时期逐渐以降香作为药材正名。从古至今降香基原历经变革,古代(1840年前)国产降香基原考证为黄檀属藤黄檀Dalbergia hancei Benth.、斜叶黄檀D. pinnata (Lour.) Prain、两粤黄檀D. benthamii Prain、滇黔黄檀D. yunnanensis Franch.等能够产生香材的藤本植物,进口降香基原则考证为黄檀属印度黄檀D. sissoo DC.、小花黄檀D. parviflora Roxb.等具有心材的木本植物;由于降真香(山油柑)Acronychia pedunculata (L.) Miq.植物名与药材名相同,1840—1948年部分著作误将山油柑作降香记载;《中华人民共和国药典》1977年版首次收录降香,规定其基原为降香檀D. odorifera T. Chen。据记载,古代国产和进口降香均无明确道地产区;1949年至今,唯一道地产区为海南省。历代本草记载,进口降香以颜色红且香气甜而不辣,或颜色紫而油润者入药为佳;中华人民共和国成立后,以降香檀心材替代进口降香入药,其品质以颜色紫红、质地坚硬油润者为佳。历代本草记载降香炮制方法包括将其刮下碾成细末和烧存性;近现代以加工成细粉或镑片为主。考证结果为今后成方制剂开发及临床应用提供重要参考。  相似文献   
2.
目的 对当归Angelica sinensis 16个赤霉素(gibberellins,GAs)进行含量测定、GAs代谢酶基因筛选并进行生物信息学分析、关键基因克隆及表达验证,以期为调控当归抽薹开花提供理论依据。方法 利用HPLC-MS/MS对不同材料中GAs含量进行测定与分析,基于当归全长转录组筛选直接参与GAs代谢酶基因,利用在线工具进行生物信息学分析,并对关键酶基因GA2ox6和GA20ox1表达水平进行q RT-PCR检测。结果 在所测定的16个GAs中,8个GAs含量在早薹植株中高于非早薹植株,13个GAs含量随植株发育时期延长逐渐增加。当归全长转录组中含有9个直接参与GAs代谢的酶基因,可分为6个亚家族,共含有6个保守基序,亚细胞定位于细胞质。GA2ox6和GA20ox1基因克隆片段由于插入序列与全长转录组测序片段存在长度差异。GA2ox6基因在抽薹植株、随种苗春化作用和植株发育时期延长呈现低表达,而在冷冻规避春化作用种苗中呈现高表达,GA20ox1基因则相反;GA2ox6和GA20ox1基因在叶和茎中相对于根均呈现高表达。结论 当归含有9个直接参与GAs代谢的酶基因,各成...  相似文献   
3.
Plant-derived natural products have been the highly significant sources of novel antitumor agents. The cassane-type diterpenes of genus Caesalpinia have been reported to bear antiproliferative activities toward different types of cancer cells. In this study, we evaluated the antineoplasmic activities of 16 natural origin cassane-type diterpenes isolated from the CHCl3 extract of the seeds of C. minax in pituitary adenomas cells and identified caesalpin G (CAG) showed the strongest cytotoxicity. Moreover, we further investigated the structure–activity relationship and molecular mechanism of these derivatives systematically. The results confirmed the unsaturated lactone-type ring, hydroxyl at C-7, and alkenyl at C-11 or C-14 functionality as critical for anticancer activity in this family of natural products. In addition, the mechanism experiments also demonstrated unfolded protein response and ER stress and Wnt/β-catenin pathway were involved in the CAG-induced apoptosis.  相似文献   
4.
Formulating nanoparticles for delivery to the deep lung is complex and many techniques fail in terms of nanoparticle stability. Spray freeze drying (SFD) is suggested here for the production of inhalable nanocomposite microcarriers (NCM). Different nanostructures were prepared and characterized including polymeric and lipid nanoparticles. Nanoparticle suspensions were co-sprayed with a suitable cryoprotectant into a cooled, stainless steel spray tower, followed by freeze drying to form a dry powder while equivalent compositions were spray dried (SD) as controls. SFD-NCM possess larger specific surface areas (67–77 m2/g) and lower densities (0.02 g/cm3) than their corresponding SD-NCM. With the exception of NCM of lipid based nanocarriers, SFD produced NCM with a mass median aerodynamic diameter (MMAD) of 3.0 ± 0.5 μm and fine particle fraction (FPF  5.2 μm) of 45 ± 1.6% with aerodynamic performances similar to SD-NCM. However, SFD was superior to SD in terms of maintaining the particle size of all the investigated polymeric and lipid nanocarriers following reconstitution (Sf/Si ratio for SFD  1 versus >1.5 for SD). The SFD into cooled air proved to be an efficient technique to prepare NCM for pulmonary delivery while maintaining the stability of the nanoparticles.  相似文献   
5.
《Vaccine》2015,33(33):4069-4080
Porcine reproductive and respiratory syndrome (PRRS) caused by PRRS virus (PRRSV) was reported in the late 1980s. PRRS still is a huge economic concern to the global pig industry with a current annual loss estimated at one billion US dollars in North America alone. It has been 20 years since the first modified live-attenuated PRRSV vaccine (PRRSV-MLV) became commercially available. PRRSV-MLVs provide homologous protection and help in reducing shedding of heterologous viruses, but they do not completely protect pigs against heterologous field strains. There have been many advances in understanding the biology and ecology of PRRSV; however, the complexities of virus-host interaction and PRRSV vaccinology are not yet completely understood leaving a significant gap for improving breadth of immunity against diverse PRRS isolates. This review provides insights on immunization efforts using infectious PRRSV-based vaccines since the 1990s, beginning with live PRRSV immunization, development and commercialization of PRRSV-MLV, and strategies to overcome the deficiencies of PRRSV-MLV through use of replicating viral vectors expressing multiple PRRSV membrane proteins. Finally, powerful reverse genetics systems (infectious cDNA clones) generated from more than 20 PRRSV isolates of both genotypes 1 and 2 viruses have provided a great resource for exploring many innovative strategies to improve the safety and cross-protective efficacy of live PRRSV vaccines. Examples include vaccines with diminished ability to down-regulate the immune system, positive and negative marker vaccines, multivalent vaccines incorporating antigens from other porcine pathogens, vaccines that carry their own cytokine adjuvants, and chimeric vaccine viruses with the potential for broad cross-protection against heterologous strains. To combat this devastating pig disease in the future, evaluation and commercialization of such improved live PRRSV vaccines is a shared goal among PRRSV researchers, pork producers and biologics companies.  相似文献   
6.
7.
江媛  杨青淑  王婧  杨成金  黄林芳  杨燕  段宝忠 《中草药》2021,52(13):4014-4022
目的获取毛重楼Parismairei叶绿体基因组信息特征并对其系统位置进行研究。方法采用Illumination测序技术对毛重楼叶绿体基因组进行测序,对其进行组装、注释和特征分析,并构建最大似然(maximumlikelihood,ML)系统发育树。结果毛重楼叶绿体基因组大小为163 918 bp,总GC含量为37.05%,大单拷贝区(large single-copy,LSC)、小单拷贝区(smallsingle-copyregion,SSC)分别为84173、13054bp,反向互补重复区(invertedrepeats,IR)大小为33296bp,共编码113个基因,包括79个蛋白质编码基因,30个t RNA基因和4个r RNA基因。在系统进化树中,重楼属Paris L.与藜芦科(Melanthiaceae Batsch ex Borkh.)关系较近,与百合科(Liliaceae Juss.)关系较远。结论 LSC区和SSC区序列变异高于IR区;相较于重楼属,毛重楼与蚤休组的亲缘关系最近,应将毛重楼归属为蚤休组;相较于百合科,毛重楼与藜芦科藜芦属亲缘关系更近,应将蚤休组从百合科中独立,归属为藜芦科。  相似文献   
8.
目的:研究制定知母种子的质量分级标准。方法:通过对不同产地20个批次知母种子的净度、千粒质量、含水量、生活力、发芽率等指标测定和外观形态观察,利用Excel 2010、SPSS 20.0软件对以上数据进行相关分析、主成分以及K-均值聚类分析,初步确定知母种子质量分级指标和分级标准,且以各等级知母种子分别在田间对比种植,通过测定1年产苗量,2年药材产量及有效成分含量,验证知母种子质量分级标准的合理性。结果:Ⅰ级知母种子发芽率不低于85%,千粒质量不低于7.5 g,净度不低于95%;Ⅱ级知母种子发芽率不低于70%,千粒质量不低于7.0 g,净度不低于85%;Ⅲ级知母种子发芽率不低于65%,千粒质量不低于6.0 g,净度不低于80%;各级种子含水量均小于10%。结论:发芽率和千粒质量为知母种子质量分级标准的主要指标,净度和含水量为参考指标。不同等级知母种子种植后对知母种苗产量、药材产量及质量会有显著影响。该研究制定的知母种子质量分级标准科学可行、符合生产实际,为知母的种子质量评价和规范化栽培提供参考依据。  相似文献   
9.
目的以根茎生物量、活性物质含量以及抗氧化能力为指标,选择适宜提高当归品质的高海拔种植区域。方法在严格控制种质、水分和土壤养分的条件下,以不同海拔(2 100、2 500和2 900 m)2年生当归根茎为材料,分别对干质量、活性物质含量以及抗氧化能力进行测定与分析。结果高海拔虽不能促进当归根茎生物量,却显著提高了活性物质的积累量和抗氧化能力;以单株积累量计算,2 900 m未抽薹当归根茎中阿魏酸、可溶性糖、酚和黄酮类含量分别为2 100 m植株的2.06、1.13、1.34和1.15倍;体外抗氧化能力也随海拔升高逐渐增加。综合分析表明,在2 100~2 900 m海拔内,未抽薹当归根茎中活性物质的总积累量(干质量和单株)均随海拔升高逐渐增加。结论提升当归种植海拔高度可显著提高根茎活性物质量;活性物质生物合成与积累受到低温和光照的综合调控。该研究结果将为提高当归产量和品质以及大面积种植栽培提供理论基础与依据。  相似文献   
10.
目的为研究DNA条形码技术在中成药鉴定中的应用,以三七片为研究对象,对方法的适用性、专属性与精密度进行考察。方法收集15批次市售三七片样品,考察三七片DNA提取条件,并对"中药材DNA条形码分子鉴定法指导原则"中PCR扩增、序列获得、结果判定等方法适用性进行确认;收集三七、人参、西洋参,制作三七片及其掺伪品,考察方法的专属性和重现性。结果三七片取样量100 mg,56℃水浴8 h所获得DNA的质量浓度平均值为60.7 ng/μL,PCR扩增、序列获得和结果判定均可获成功;三七、人参和西洋参的ITS2序列长度均为230bp,三七与人参、三七与西洋参的序列间均存在7个稳定的SNP位点,自制三七片和掺伪三七片均可成功获得ITS2序列,不同比例三七与人参、三七与西洋参的测序峰图在SNP位点处呈现相应峰高比的SNP套峰具备专属性;重复性、中间精密度和重现性考察符合《中国药典》2015年版(通则9101)相关要求。结论 ITS2序列作为DNA条形码能够稳定、准确鉴定三七片的原料药材,具备良好的专属性和精密度,三七片DNA条形码分子鉴定法将为保障三七片临床用药安全提供新的技术手段,并对《中国药典》其他收载单方制剂的鉴定提供参考。  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