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   3273篇
  免费   155篇
  国内免费   189篇
耳鼻咽喉   12篇
儿科学   50篇
妇产科学   29篇
基础医学   307篇
口腔科学   83篇
临床医学   273篇
内科学   849篇
皮肤病学   19篇
神经病学   51篇
特种医学   408篇
外国民族医学   1篇
外科学   234篇
综合类   358篇
现状与发展   1篇
预防医学   201篇
眼科学   7篇
药学   310篇
  2篇
中国医学   335篇
肿瘤学   87篇
  2023年   16篇
  2022年   51篇
  2021年   48篇
  2020年   66篇
  2019年   68篇
  2018年   86篇
  2017年   73篇
  2016年   139篇
  2015年   183篇
  2014年   286篇
  2013年   275篇
  2012年   351篇
  2011年   360篇
  2010年   242篇
  2009年   186篇
  2008年   148篇
  2007年   173篇
  2006年   119篇
  2005年   103篇
  2004年   117篇
  2003年   113篇
  2002年   90篇
  2001年   64篇
  2000年   47篇
  1999年   30篇
  1998年   39篇
  1997年   29篇
  1996年   20篇
  1995年   16篇
  1994年   17篇
  1993年   15篇
  1992年   8篇
  1991年   11篇
  1990年   8篇
  1989年   6篇
  1988年   7篇
  1987年   3篇
  1986年   1篇
  1985年   1篇
  1982年   1篇
  1980年   1篇
排序方式: 共有3617条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
In normal tissue repair, macrophages exhibit a pro-inflammatory phenotype (M1) at early stages and a pro-healing phenotype (M2) at later stages. We have previously shown that M1 macrophages initiate angiogenesis while M2 macrophages promote vessel maturation. Therefore, we reasoned that scaffolds that promote sequential M1 and M2 polarization of infiltrating macrophages should result in enhanced angiogenesis and healing. To this end, we first analyzed the in vitro kinetics of macrophage phenotype switch using flow cytometry, gene expression, and cytokine secretion analysis. Then, we designed scaffolds for bone regeneration based on modifications of decellularized bone for a short release of interferon-gamma (IFNg) to promote the M1 phenotype, followed by a more sustained release of interleukin-4 (IL4) to promote the M2 phenotype. To achieve this sequential release profile, IFNg was physically adsorbed onto the scaffolds, while IL4 was attached via biotin-streptavidin binding. Interestingly, despite the strong interactions between biotin and streptavidin, release studies showed that biotinylated IL4 was released over 6 days. These scaffolds promoted sequential M1 and M2 polarization of primary human macrophages as measured by gene expression of ten M1 and M2 markers and secretion of four cytokines, although the overlapping phases of IFNg and IL4 release tempered polarization to some extent. Murine subcutaneous implantation model showed increased vascularization in scaffolds releasing IFNg compared to controls. This study demonstrates that scaffolds for tissue engineering can be designed to harness the angiogenic behavior of host macrophages towards scaffold vascularization.  相似文献   
5.
BackgroundAutism spectrum disorder is a condition that affects all races, ethnic and socioeconomic groups. With a high incidence ratio of one in every 68, it has become one of the most discussed psychiatric disorders. For this reason, the need for investigating novel treatments has been emerging. Qigong, a traditional Chinese mind-body technique, has already proven to be able to reduce symptoms of several physical and psychological illnesses.ObjectiveThe purpose of this systematic review is to examine and categorize the current scientific evidence regarding the efficacy of Qigong on children suffering from autism spectrum disorders.Search strategyA systematic literature search of the electronic scientific databases PubMed, Clinical Trials.gov, BioMed Central, PubMed Central and Google Scholar was performed to identify studies of Qigong in the treatment of children with autism spectrum disorder.Inclusion criteriaThis review included randomized controlled trials, replication studies, retrospective studies and observational follow-up studies of Qigong on children with autism spectrum disorder. Case reports and case series were excluded.Data extraction and analysisTwo researchers independently evaluated the methodological quality of all included studies. Any discrepancies were solved by discussion until consensus was achieved.ResultsOur literature search identified 157 publications, and 10 additional publications from hand search of references. After duplicate removal, 103 records remained. After the title/abstract screening, 19 publications were obtained for detailed evaluation. After detailed evaluation, 10 studies were included. Seven studies were conducted with small children with 2–6 years old employing Qigong massage, and three studies were conducted with older children aged 7–17 years old applying both Qigong massage (one study) and Neigong (two studies).ConclusionStudies demonstrated that Qigong has interesting and promising applicability and effect on children with autism spectrum disorder and should be tested further. Despite the need for more rigorous controlled studies, Qigong seems to be able to decrease severity of individual sensory, behavioural, and language components of autism, and improve self-control, sociability, sensory and cognitive awareness as well as healthy-physical behaviour. Besides positive effect on children and adolescents, benefits seem to extend to parents and caregivers as well. However, quality of methodology seems to be insufficient to state that Qigong is an alternative to common behavioural therapies. We suggest that, until more investigation is performed, Qigong may only be used as a complement, or when behavioural therapies are not accessible.  相似文献   
6.
目的 研究乙型肝炎病毒(HBV)自身增强子I(enhancerI,ENHI)对HBV DNA疫苗免疫应答的影响。方法 采用PCR法以HBVadr亚型全基因DNA序列为模板分别扩增表面抗原(HBsAg)和HBsA-ENHI基因片段,重组到载体VR1012中,构建两种HBV DNA疫苗,转染CADS-7细胞及HepG2细胞并免疫BALB/c小鼠。采用蛋白印迹、ELISA、ELISPOT等方法检测其在COS-7和HepG2细胞内的表达及小鼠的体液及细胞免疫应答效果。结果 转染的HepG2和COS-7细胞均表达HBsAg;连接ENHI的HBV DNA疫苗转染HepG2细胞后HBsAg表达量明显升高,两种疫苗转染COS-7细胞表达HBsAg无明显差异;免疫小鼠后第2周产生HBsAb及HBsAg特异性细胞毒T淋巴细胞(CTL),两种疫苗免疫产生的HBsAb及HBsAg特异性CTL无明显差异。结论ENHI可使HBV DNA疫苗转染HepG2细胞表达HBsAg明显增加,对转染COS-7细胞表达HBsAg及接种BALB/C小鼠引起的免疫应答无明显影响。  相似文献   
7.
目的研究丙型肝炎病毒(HCV)核心蛋白6号结合蛋白基因(Hcbp6)序列表达的调控机制。方法根据软件对启动子的预测,选取翻译起始密码子ATG上游3256bp及下游180bp的DNA序列,分成5段活性区域,分别以聚合酶链反应技术(PCR),肝母细胞瘤细胞系HePG2基因组DNA为模板,扩增该启动子DNA片段,将其克隆至PCAT3中,构建PCAT3-Hcbp6-P报告基因表达载体,将该质粒分别转染HePG2,NIH3T3细胞,用酶联免疫吸附法检测报告基因编码产物氯霉素乙酰转移酶(CAT)的表达活性。结果发现质粒pCAT3-Hcbp6-1066p和pCAT3-Hcbp6-240p能够指导CAT的表达,其平均吸光度值(4)是PCAT3-basic对照质粒的3.1倍和6.4倍。结论本研究克隆的启动子DNA序列具有转录活性,这一结果为研究HcbP6的调节机制,进一步阐明HCV核心蛋白的作用机制奠定了基础。  相似文献   
8.
增强子Ⅰ对乙型肝炎病毒DNA疫苗免疫应答的影响   总被引:1,自引:0,他引:1  
目的研究乙型肝炎病毒(HBV)自身增强子Ⅰ(enhancerⅠ,ENHⅠ)对HBVDNA疫苗免疫应答的影响。方法采用PCR法以HBVadr亚型全基因DNA序列为模板分别扩增表面抗原(HBsAg)和HBsAg-ENHⅠ基因片段,重组到载体VR1012中,构建两种HBVDNA疫苗,转染COS-7细胞及HepG2细胞并免疫BALB/c小鼠。采用蛋白印迹、ELISA、ELISPOT等方法检测其在COS-7和HepG2细胞内的表达及小鼠的体液及细胞免疫应答效果。结果转染的HepG2和COS-7细胞均表达HBsAg;连接ENHⅠ的HBVDNA疫苗转染HepG2细胞后HBsAg表达量明显升高,两种疫苗转染COS-7细胞表达HBsAg无明显差异;免疫小鼠后第2周产生HBsAb及HBsAg特异性细胞毒T淋巴细胞(CTL),两种疫苗免疫产生的HBsAb及HBsAg特异性CTL无明显差异。结论ENHⅠ可使HBVDNA疫苗转染HepG2细胞表达HBsAg明显增加,对转染COS-7细胞表达HBsAg及接种BALB/c小鼠引起的免疫应答无明显影响。  相似文献   
9.
There is little agreement about the methodology of clinical trials of antipsychotic drugs in patients with negative symptoms. A literature review revealed wide variation in experimental design, rating scales and study duration. This reflects differing views as to the definition and response to treatment of negative symptoms. Some degree of standardization would improve comparability of studies and aid the development of new compounds. Patients included in such studies should have displayed negative symptoms for at least 6 months. Depressive symptoms, positive schizophrenic symptoms and extrapyramidal signs may all influence or be confused with negative symptoms and may respond to treatment; they should be at a low level at baseline and should be measured during the study period. Studies should last at least 8 weeks. Several scales are available for measuring negative symptoms and are reviewed; a global impression score should be used additionally.  相似文献   
10.
介绍了一种简单有效的维纳滤波器设计过程,并采用该过程对数字化X射线影像进行滤波,试验表明:维纳滤波器能在去除图像噪声的同时较好地保留图像细节,具有实际应用价值。  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