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   2389858篇
  免费   198897篇
  国内免费   4282篇
耳鼻咽喉   34484篇
儿科学   73176篇
妇产科学   63310篇
基础医学   337304篇
口腔科学   68607篇
临床医学   216940篇
内科学   472854篇
皮肤病学   48329篇
神经病学   202202篇
特种医学   96271篇
外国民族医学   886篇
外科学   362409篇
综合类   56304篇
现状与发展   1篇
一般理论   989篇
预防医学   192932篇
眼科学   55678篇
药学   178744篇
  4篇
中国医学   4468篇
肿瘤学   127145篇
  2018年   25001篇
  2017年   19269篇
  2016年   21039篇
  2015年   23860篇
  2014年   34152篇
  2013年   51684篇
  2012年   70304篇
  2011年   73967篇
  2010年   43289篇
  2009年   41423篇
  2008年   70086篇
  2007年   74443篇
  2006年   75227篇
  2005年   73212篇
  2004年   70359篇
  2003年   67925篇
  2002年   67113篇
  2001年   112611篇
  2000年   116722篇
  1999年   98478篇
  1998年   27909篇
  1997年   25554篇
  1996年   25479篇
  1995年   24634篇
  1994年   23176篇
  1993年   21567篇
  1992年   79447篇
  1991年   76441篇
  1990年   73622篇
  1989年   70886篇
  1988年   65873篇
  1987年   64836篇
  1986年   61354篇
  1985年   58428篇
  1984年   44242篇
  1983年   37685篇
  1982年   22900篇
  1981年   20348篇
  1979年   41309篇
  1978年   29000篇
  1977年   24359篇
  1976年   22840篇
  1975年   23981篇
  1974年   29665篇
  1973年   28059篇
  1972年   26237篇
  1971年   24171篇
  1970年   22767篇
  1969年   21102篇
  1968年   19152篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
Red cell exchange (RCE) is a common procedure in adults with sickle cell disease (SCD). Implantable dual lumen Vortex (DLV) ports can be used for RCE in patients with poor peripheral venous access. We performed a retrospective cohort study of RCE procedures performed in adults with SCD. The main objective of the study was to compare the inlet speed, duration of procedures and rate of complications performed through DLV ports to those performed through temporary central venous and peripheral catheters. Twenty‐nine adults with SCD underwent a total of 318 RCE procedures. Twenty adults had DLV ports placed and 218 procedures were performed using DLV ports. Mean length of follow‐up after DLV port placement was 397 ± 263 days. Six DLV ports were removed due to infection and 1 for malfunction after a mean of 171 ± 120 days. Compared to temporary central venous and peripheral catheters, DLV port procedures had a greater rate of procedural complications, a longer duration, and a lower inlet speed (all P < 0.01). When accounting for the maximum allowable inlet speed to avoid citrate toxicity, 40% of DLV port procedures were greater than 10% below maximum speed, compared to 7 and 14% of procedures performed through temporary central venous and peripheral catheters (P < 0.0001). In conclusion, DLV ports can be used for RCE in adults with SCD, albeit with more procedural complications and longer duration. The smaller internal diameter and longer catheter of DLV ports compared to temporary central venous catheters likely accounts for the differences noted. J. Clin. Apheresis 30:353–358, 2015. © 2015 Wiley Periodicals, Inc.  相似文献   
74.
The catechol-O-methyltransferase (COMT) enzyme is a major determinant of prefrontal dopamine levels. The Val158Met polymorphism affects COMT enzymatic activity and has been associated with variation in executive function and affective processing. This study investigated the effect of COMT genotype on the flexible modulation of the balance between processing self-generated and processing stimulus-oriented information, in the presence or absence of affective distractors. Analyses included 124 healthy adult participants, who were also assessed on standard working memory (WM) tasks. Relative to Val carriers, Met homozygotes made fewer errors when selecting and manipulating self-generated thoughts. This effect was partly accounted for by an association between COMT genotype and visuospatial WM performance. We also observed a complex interaction between the influence of affective distractors, COMT genotype and sex on task accuracy: male, but not female, participants showed a sensitivity to the affective distractors that was dependent on COMT genotype. This was not accounted for by WM performance. This study provides novel evidence of the role of dopaminergic genetic variation on the ability to select and manipulate self-generated thoughts. The results also suggest sexually dimorphic effects of COMT genotype on the influence of affective distractors on executive function.  相似文献   
75.
76.
77.
78.
The value of adding simeprevir (SMV) vs placebo (PBO) to peginterferon and ribavirin (PR) for treatment of chronic hepatitis C virus infection was examined using patient‐reported outcomes (PROs); further, concordance of PROs with virology endpoints and adverse events (AEs) was explored. Patients (= 768 SMV/PR,= 393 PBO/PR) rated fatigue (FSS), depressive symptoms (CES‐D) and functional impairment (WPAI: Hepatitis C Productivity, Daily Activity and Absenteeism) at baseline and throughout treatment in three randomised, double‐blind trials comparing the addition of SMV or PBO during initial 12 weeks of PR. PR was administered for 48 weeks (PBO group) and 24/48 weeks (SMV group) using a response‐guided therapy (RGT) approach. Mean PRO scores (except Absenteeism) worsened from baseline to Week 4 to the same extent in both groups but reverted after Week 24 for SMV/PR and only after Week 48 for PBO/PR. Accordingly, there was a significantly lower area under the curve (baseline–Week 60, AUC60) and fewer weeks with clinically important worsening of scores in the SMV/PR group at any time point. Incidences of patients with fatigue and anaemia AEs were similar in both groups, but FSS scores showed that clinically important increases in fatigue lasted a mean of 6.9 weeks longer with PBO/PR (P < 0.001). PRO score subgroup analysis indicated better outcomes for patients who met the criteria for RGT or achieved sustained virological response 12 weeks post‐treatment (SVR12); differences in mean PRO scores associated with fibrosis level were only observed with PBO/PR. Greater efficacy of SMV/PR enabled reduced treatment duration and reduced time with PR‐related AEs without adding to AE severity.  相似文献   
79.
80.
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