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   2839篇
  免费   192篇
  国内免费   28篇
耳鼻咽喉   118篇
儿科学   95篇
妇产科学   125篇
基础医学   278篇
口腔科学   118篇
临床医学   257篇
内科学   689篇
皮肤病学   61篇
神经病学   116篇
特种医学   137篇
外科学   715篇
综合类   42篇
一般理论   2篇
预防医学   61篇
眼科学   68篇
药学   86篇
中国医学   6篇
肿瘤学   85篇
  2023年   12篇
  2022年   15篇
  2021年   83篇
  2020年   32篇
  2019年   51篇
  2018年   68篇
  2017年   46篇
  2016年   84篇
  2015年   109篇
  2014年   140篇
  2013年   157篇
  2012年   204篇
  2011年   186篇
  2010年   115篇
  2009年   112篇
  2008年   205篇
  2007年   213篇
  2006年   190篇
  2005年   168篇
  2004年   163篇
  2003年   125篇
  2002年   105篇
  2001年   38篇
  2000年   60篇
  1999年   38篇
  1998年   8篇
  1997年   16篇
  1996年   18篇
  1995年   16篇
  1994年   12篇
  1992年   23篇
  1991年   21篇
  1990年   13篇
  1989年   11篇
  1988年   11篇
  1987年   14篇
  1986年   12篇
  1985年   14篇
  1984年   13篇
  1983年   15篇
  1981年   11篇
  1980年   6篇
  1979年   13篇
  1977年   6篇
  1975年   9篇
  1973年   12篇
  1970年   7篇
  1969年   10篇
  1968年   6篇
  1966年   5篇
排序方式: 共有3059条查询结果,搜索用时 15 毫秒
981.
This study was conducted to investigate possible histopathological effects and biochemical reflections of intra‐articular dexketoprofen trometamol. A total of 24 New Zealand rabbits were included in the study. Blood sampling was carried out from all animals on the first day, then they were randomly allocated either to the control group (Group C, n = 9) or the dexketoprofen trometamol group (Group D, n = 15). Group C underwent each two intra‐articular injections of saline, 0.25 mL into right and 0.50 mL into left knee. Group D was injected 0.25 mL (6.25 mg) dexketoprofen trometamol into the right knee and 0.50 mL (12.5 mg) into the left. The groups were divided randomly into three. Tissue and blood samples were collected from Groups C1 and D1 on the first day, C2 and D2 on the second day and C3 and D3 on the 10th day of the study. Interleukin‐1 (IL‐1β), interleukin‐6 (IL‐6), tumour necrosis factor‐alpha (TNF‐α) and C‐reactive protein (CRP) levels were studied. The histopathological examination of C and D groups did not present any deterioration. IL‐6 basal levels were significantly higher in Group D2 compared with C2 and C3 compared with D3. Basal TNF‐α levels were higher compared with day 1 in Group C1, and IL‐6 and CRP levels were higher in Group D3. Also, none of the increases in these values are supported by histopathological evaluation results. Consequently, we suppose that dexketoprofen trometamol does not cause histopathological deterioration in articular cartilage of rabbits, and the increases in biochemical parameters exclusively are not clinically significant.  相似文献   
982.
983.
984.
Juvenile papillomatosis is a rare disease affecting young women. Here we present magnetic resonance imaging features of two cases with histopathologically proven juvenile papillomatosis of the breast and review some of the relevant literature. Case 1 exhibited bilateral, well-bordered breast masses, with complex cystic and solid components. The kinetic evaluation showed continuous and plateau patterns. Case 2 featured a giant mass with a few cystic and many solid nodular components and filled the entire right breast. The kinetic evaluation showed a continuous curve.  相似文献   
985.
986.
Needle tip visualization during ultrasound-guided regional anesthesia (UGRA) is necessary for safety and efficacy. However, disruption of the image of the needle tip driven toward the target is a general problem, especially for beginners. The purpose of this study was to compare performance parameters between using the Sonoplex and Stimuplex D-Plus echogenic needles in a simulated ultrasound-guided interventional task by inexperienced anaesthesia residents. After a standardized training session, 28 anesthesiology residents performed simulated nerve blocks in a beef phantom with each needle. All ultrasound images were digitally stored for analysis. The absolute time the needle tip was in view, total procedure time, and angle of needle insertion were subsequently measured objectively by two single investigators. The procedures that used the Sonoplex echogenic needle had significantly better tip visibility and shorter total procedure time at insertion angles between 42° and 64° relative to the phantom surface. We have demonstrated that inexperienced users who used the Sonoplex echogenic needle were able to complete the procedure more quickly. Needles with improved visibility would be a very useful addition to UGRA for inexperienced users.  相似文献   
987.
988.
989.
990.
Tuning genetic control through promoter engineering   总被引:5,自引:0,他引:5  
Gene function is typically evaluated by sampling the continuum of gene expression at only a few discrete points corresponding to gene knockout or overexpression. We argue that this characterization is incomplete and present a library of engineered promoters of varying strengths obtained through mutagenesis of a constitutive promoter. A multifaceted characterization of the library, especially at the single-cell level to ensure homogeneity, permitted quantitative assessment correlating the effect of gene expression levels to improved growth and product formation phenotypes in Escherichia coli. Integration of these promoters into the chromosome can allow for a quantitative accurate assessment of genetic control. To this end, we used the characterized library of promoters to assess the impact of phosphoenolpyruvate carboxylase levels on growth yield and deoxy-xylulose-P synthase levels on lycopene production. The multifaceted characterization of promoter strength enabled identification of optimal expression levels for ppc and dxs, which maximized the desired phenotype. Additionally, in a strain preengineered to produce lycopene, the response to deoxy-xylulose-P synthase levels was linear at all levels tested, indicative of a rate-limiting step, unlike the parental strain, which exhibited an optimum expression level, illustrating that optimal gene expression levels are variable and dependent on the genetic background of the strain. This promoter library concept is illustrated as being generalizable to eukaryotic organisms (Saccharomyces cerevisiae) and thus constitutes an integral platform for functional genomics, synthetic biology, and metabolic engineering endeavors.  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