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   11510篇
  免费   733篇
  国内免费   55篇
耳鼻咽喉   305篇
儿科学   288篇
妇产科学   312篇
基础医学   1655篇
口腔科学   439篇
临床医学   950篇
内科学   2652篇
皮肤病学   204篇
神经病学   1293篇
特种医学   256篇
外科学   1055篇
综合类   21篇
一般理论   5篇
预防医学   696篇
眼科学   132篇
药学   713篇
中国医学   41篇
肿瘤学   1281篇
  2024年   12篇
  2023年   109篇
  2022年   275篇
  2021年   433篇
  2020年   276篇
  2019年   326篇
  2018年   358篇
  2017年   301篇
  2016年   362篇
  2015年   389篇
  2014年   520篇
  2013年   627篇
  2012年   959篇
  2011年   1069篇
  2010年   543篇
  2009年   464篇
  2008年   806篇
  2007年   738篇
  2006年   659篇
  2005年   684篇
  2004年   614篇
  2003年   562篇
  2002年   490篇
  2001年   71篇
  2000年   50篇
  1999年   70篇
  1998年   93篇
  1997年   63篇
  1996年   45篇
  1995年   51篇
  1994年   34篇
  1993年   37篇
  1992年   32篇
  1991年   22篇
  1990年   17篇
  1989年   22篇
  1988年   16篇
  1987年   9篇
  1986年   16篇
  1985年   9篇
  1984年   10篇
  1983年   7篇
  1982年   6篇
  1980年   7篇
  1979年   7篇
  1978年   6篇
  1976年   4篇
  1973年   4篇
  1970年   3篇
  1969年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
The production of chemicals from bio-based feedstocks is an emerging field of research in both industrial and academic communities. Here we present the synthesis of propylene glycol through catalytic hydrogenolysis of glycidol, obtained using a side-stream from the bio-based epichlorohydrin production plant, over Pd/C catalyst. In particular, we show the prominent effect of the acidic resin Amberlyst-15 in the selective and quantitative conversion of glycidol that permits to reach a TOF value of 162 h?1. Propylene glycol is obtained with high yields and selectivity (> 99%) in only 1 h under mild reaction conditions. The effect of solvent is also investigated giving interesting results on the reaction selectivity. The catalytic system (Pd/C + Amberlyst-15) shows a good recyclability also after seven reaction cycles reaching high performances in term of conversion and selectivity. This allowed minimizing the amount of waste and enhancing the efficiency of the whole system.  相似文献   
142.
Increased telomerase expression has been implicated in the pathogenesis of lung cancer and, since the primary cause of lung cancer is smoking, an association between telomerase reactivation and tobacco smoke has been proposed. In this work an investigation has been performed to assess the relationship between tobacco smoke exposure and telomerase activity (TA) in peripheral blood mononuclear cells of healthy smokers. The methylation status of the catalytic subunit of telomerase hTERT was concurrently investigated to assess the possible association between epigenetic modifications of hTERT and TA. Besides, the association between smoke and telomere length (TL) has been evaluated. Healthy monozygotic twins with discordant smoking habits were selected as study population to minimize inter‐individual differences because of demographic characteristics and genetic heterogeneity. Statistically significant higher values of TA and TL were observed in smokers compared to nonsmoker co‐twins. The multivariate analysis of data showed, besides smoking habits (P = 0.02), an influence of gender (P = 0.006) and BMI (P = 0.001) on TA and a borderline effect of gender (P = 0.05) on TL. DNA methylation analysis, focused on 100 CpG sites mapping in hTERT, highlighted nine CpG sites differentially methylated in smokers. When co‐twins were contrasted, selecting as variables the intra‐twin difference in TA and hTERT DNA methylation, a statistically significant inverse correlation (P = 0.003) was observed between TA and DNA methylation at the cg05521538 site. In conclusion, these results indicate an association of tobacco smoke with TA and TL and suggest a possible association between smoke‐induced epigenetic effects and TA in healthy smokers. Environ. Mol. Mutagen. 58:551–559, 2017. © 2017 Wiley Periodicals, Inc.  相似文献   
143.
144.
145.
  相似文献   
146.
147.
148.
149.
Dysmetabolic iron overload syndrome is a rare event causing hepatic impairment with serious long‐term side effects. Here, we describe a case of metabolic syndrome‐related hepatic iron overload that showed a rapid, effective, and safe response to erythrocytapheresis. J. Clin. Apheresis 31:443–447, 2016. © 2015 Wiley Periodicals, Inc.  相似文献   
150.
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