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   433篇
  免费   34篇
  国内免费   2篇
耳鼻咽喉   1篇
儿科学   13篇
妇产科学   18篇
基础医学   48篇
口腔科学   10篇
临床医学   48篇
内科学   65篇
皮肤病学   8篇
神经病学   31篇
特种医学   8篇
外科学   92篇
综合类   5篇
预防医学   35篇
眼科学   14篇
药学   48篇
中国医学   2篇
肿瘤学   23篇
  2024年   1篇
  2023年   4篇
  2022年   8篇
  2021年   31篇
  2020年   16篇
  2019年   30篇
  2018年   36篇
  2017年   26篇
  2016年   32篇
  2015年   25篇
  2014年   28篇
  2013年   26篇
  2012年   45篇
  2011年   42篇
  2010年   19篇
  2009年   21篇
  2008年   15篇
  2007年   10篇
  2006年   13篇
  2005年   10篇
  2004年   4篇
  2003年   1篇
  2002年   3篇
  2001年   1篇
  1999年   1篇
  1998年   1篇
  1995年   3篇
  1994年   2篇
  1993年   3篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1987年   2篇
  1986年   1篇
  1984年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
  1970年   1篇
排序方式: 共有469条查询结果,搜索用时 48 毫秒
101.
102.
Fungal stromata were recently discovered in association with charcoal and burnt soil aggregates during an archaeological survey in the Châtillon-sur-Seine forest massif. The wood and soil in the samples were dated to the medieval period (between 738 and 1411 AD). Light microscopy and scanning electron microscopy revealed that a few of the stromatal fragments still contained ascospores. Their macromorphological characters were described and secondary metabolite profiles were generated using high performance liquid chromatography with diode array and mass spectrometric detection (HPLC–DAD/MS). The combination of these two data lines then allowed species identification. Most of the fragments were assigned to Hypoxylon fragiforme, the type species of the Hypoxylaceae (Xylariales). Two further species whose stromata grew on the fossil charcoal could be tentatively identified as Jackrogersella cohaerens and (more tentatively) as Hypoxylon vogesiacum. These three species are still commonly encountered in the forests of Central Europe today. Furthermore, the HPLC-HRMS data of H. fragiforme suggested the presence of unknown azaphilone dimers and of further new pigments. These archaeological compounds were compared to fresh stromata of H. fragiforme collected in Germany and subjected to the same analytical protocol. While the major components in both samples were identified as the known mitorubrin type azaphilones and orsellinic acid, the chemical structures of seven novel complex azaphilone pigments, for which we propose the trivial names rutilins C-D and fragirubrins A-E, were elucidated using spectral methods (NMR and CD spectroscopy, high resolution mass spectrometry). It appears that these pigments had indeed persisted for millennia in the fossil stromata.  相似文献   
103.
104.
105.
After years of ongoing endeavors for HBV infection prognosis, diagnosis and treatment, it still remains a major health problem worldwide. About 400 million chronic carriers and an annual death rate as high as one million reflects the seriousness of the problem. Developing novel and more effective diagnostic strategies, using in silico approaches and their subsequent empirical verification, will be helpful in providing for blood supply safety, therapeutics efficacy and disease activity assessment. Exploiting various in silico tools a novel multiepitope detection construct was designed which was consisted of eight linked linear immunodominant HBV epitopes. The designed antigen was expressed in Escherichia coli as the host. The detection capability of the designed antigen was tested using Chemiluminescent immunoassay method. Chemiluminescent immunoassay on the expressed antigen revealed that the product may be a credible candidate for simultaneous detection of three main HBV antibodies. All three test samples in two concentrations indicated lower RLU/s in comparison to the positive control which was the direct consequence of HBV antibody detection by the designed antigen. In the present study, employing bioinformatics tools paved the way for rational design of multiepitope antigen in a more cost effective, intelligent and knowledge-based method. The obtained results could be construed as a primary proof of concept that the in silico predictions could be used as primary steps of the biological studies and their subsequent empirical conduction.  相似文献   
106.
107.
Context: Acute lymphoblastic leukemia patients show differences in methotrexate-induced toxicity after treatment with this anti-cancer drug. Pharmacogenetics is an important determining factor for toxicity diversity. Objective: In this study, the effect of +452 CT and ? 401CT polymorphisms of Gamma-glutamyl hydrolase (GGH) gene on methotrexate serum levels and its associated toxicity in patients with acute lymphoblastic leukemia was assessed. Furthermore, the frequency of the above polymorphisms was investigated for the first time in Iran. Material and methods: The prevalence of these polymorphisms was assessed in 83 Iranian patients with ALL using PCR and RFLP. The relationship between the polymorphism and serum methotrexate levels and its toxicity was estimated by calculating the Odds Ratio. Results: No correlation was found between +452CT polymorphism and serum levels of methotrexate and methotrexate-related toxicity. ?401CT polymorphism was found to be correlated with methotrexate-related toxicity leading to thrombocytopenia (95% CI?=?0.009–0.019, odds ratio?=?0.265) and leukopenia (95% CI?=?0.021–0.042, odds ratio?=?2.182) in consolidation phase of the treatment. Discussion: C allele polymorphism of ?401?C/T allele is a risk factor of leukopenia and thrombocytopenia in patients treated with methotrexate. Moreover, our results suggested that the T allele had a supporting role in prevention of thrombocytopenia. Conclusion: Evaluation of patients for methotrexate-related polymorphism of GGH gene may be useful to determine the appropriate dose of methotrexate and reducing its toxic side effects.  相似文献   
108.
Iran passed a Law in 2010 to merge all existing health insurance funds physically together. This stakeholder analysis aimed at revealing that what benefits the stakeholders might lose or gain as a result of merging health insurance schemes in Iran, which make them to oppose or support it. This was a qualitative study conducted in 2014. Sixty semi‐structured face‐to‐face interviews were conducted. Purposive and snowball samplings with maximum heterogeneity samples were used for selecting interviewees. Government is not willing to undertake more financial commitment. Existing health insurance schemes like Social Security Organization and minor well‐resourced health insurance funds and also worker unions are unwilling to lose their financial and organizational autonomy, to share their benefits with other less privileged groups, or face likely financial challenges in running their health facilities like hospitals. Top managers and workforces are worried to lose their job, salary, or organizational positions. Ministry of Cooperation, Labour, and Social Welfare does not want to lose its control on health insurance schemes. Ministry of Health and Medical Education and Iran Health Insurance Organization are among actors that support the insurance funds merging policy. Successful implementing of consolidation requires taking into account the interests of different stakeholders.  相似文献   
109.
Various types of bias and confounding have been described in the biomedical literature that can affect a study before, during, or after the intervention has been delivered. The peer review process can also introduce bias. A compelling ethical and moral rationale necessitates improving the peer review process. A double-blind peer review system is supported on equipoise and fair-play principles. Triple- and quadruple-blind systems have also been described but are not commonly used. The open peer review system introduces “Skin in the Game” heuristic principles for both authors and reviewers and has a small favorable effect on the quality of published reports. In this exposition, we present, on the basis of a comprehensive literature search of PubMed from its inception until October 20, 2017, various possible mechanisms by which the peer review process can distort research results, and we discuss the evidence supporting different strategies that may mitigate this bias. It is time to improve the quality, transparency, and accountability of the peer review system.  相似文献   
110.
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