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   1383033篇
  免费   114183篇
  国内免费   6628篇
耳鼻咽喉   17086篇
儿科学   44082篇
妇产科学   37484篇
基础医学   190201篇
口腔科学   38241篇
临床医学   124299篇
内科学   287310篇
皮肤病学   32894篇
神经病学   114375篇
特种医学   56624篇
外国民族医学   274篇
外科学   214469篇
综合类   32718篇
现状与发展   2篇
一般理论   459篇
预防医学   111235篇
眼科学   28728篇
药学   97388篇
  33篇
中国医学   2460篇
肿瘤学   73482篇
  2018年   15739篇
  2017年   12154篇
  2016年   14544篇
  2015年   16354篇
  2014年   22355篇
  2013年   32785篇
  2012年   40020篇
  2011年   42410篇
  2010年   26665篇
  2009年   25858篇
  2008年   38905篇
  2007年   41245篇
  2006年   41998篇
  2005年   40331篇
  2004年   38323篇
  2003年   37019篇
  2002年   34859篇
  2001年   66209篇
  2000年   68098篇
  1999年   56783篇
  1998年   16970篇
  1997年   15226篇
  1996年   16149篇
  1995年   16331篇
  1994年   15191篇
  1993年   14248篇
  1992年   47175篇
  1991年   45802篇
  1990年   44033篇
  1989年   41871篇
  1988年   38809篇
  1987年   38115篇
  1986年   35891篇
  1985年   34657篇
  1984年   26387篇
  1983年   22124篇
  1982年   13881篇
  1981年   12462篇
  1980年   11743篇
  1979年   23550篇
  1978年   17079篇
  1977年   14397篇
  1976年   13195篇
  1975年   13734篇
  1974年   16099篇
  1973年   15406篇
  1972年   14183篇
  1971年   13051篇
  1970年   11887篇
  1969年   11109篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
113.
114.
About 10% of patients with Lyme disease continue to experience musculoskeletal pain and cognitive dysfunction after recommended antibiotic treatment. This condition is called post-Lyme disease syndrome (PLDS) or post-treatment Lyme disease syndrome. These two terms are used interchangeably. The pathogenesis of PLDS has been controversial. The hypothesis that patients with PLDS may harbor hidden reservoirs of Borrelia burgdorferi after their initial antibiotic treatment is difficult to accept. The prospective, double-blind studies contradict this point of view. Also, recently published research applying xenodiagnosis to PLDS supports the opinion that PLDS most likely has an autoimmune background. Lengthy courses of antibiotics are not justified in patients with PLDS because of the lack of benefit, and they are fraught with hazards. Most patients with PLDS recover from persistent symptoms with time. However, it can take months before they feel completely well.  相似文献   
115.
116.
117.
Abstract

This study was undertaken to compare the concentrations of pro- and anti-angiogenic growth factors, nitric oxide (NO) stable metabolites in maternal serum and embryonic left ventricular (LV) isovolumic relaxation time (IRT, ms) during the first trimester in two groups of women: with pregnancy conceived by assisted reproductive technologies (ART, n?=?39) and normally conceived (control group, n?=?68) pregnancy. The concentration of vasoconstrictor endothelin 1 was 45.5 times more in ART than in control group. On the contrary, the concentrations of NO stable metabolites in ART were 1.9 times less than in control women. The assessment of angiogenic suppressors in ART women demonstrates the decrease in s-endoglin concentration was 1.6 times and in soluble receptor to vascular endothelial growth factor concentration was 2.0 times in comparison with control group. There was a significant increase in LV IRT in ART embryos in comparison to control ones. These data suggest significant changes in pro- anti-angiogenic factors balance and increase in vascular impedance in ART-conceived embryos.  相似文献   
118.
119.
Postoperative pulmonary complications are associated with an increase in mortality, morbidity and healthcare utilisation. The Agency for Healthcare Research and Quality recommends risk assessment for postoperative respiratory complications in patients undergoing surgery. In this hospital registry study of adult patients undergoing non-cardiac surgery between 2005 and 2017 at two independent healthcare networks, a prediction instrument for early postoperative tracheal re-intubation was developed and externally validated. This was based on the development of the Score for Prediction Of Postoperative Respiratory Complications. For predictor selection, stepwise backward logistic regression and bootstrap resampling were applied. Development and validation cohorts were represented by 90,893 patients at Partners Healthcare and 67,046 patients at Beth Israel Deaconess Medical Center, of whom 699 (0.8%) and 587 (0.9%) patients, respectively, had their tracheas re-intubated. In addition to five pre-operative predictors identified in the Score for Prediction Of Postoperative Respiratory Complications, the final model included seven additional intra-operative predictors: early post-tracheal intubation desaturation; prolonged duration of surgery; high fraction of inspired oxygen; high vasopressor dose; blood transfusion; the absence of volatile anaesthetic use; and the absence of lung-protective ventilation. The area under the receiver operating characteristic curve for the new score was significantly greater than that of the original Score for Prediction Of Postoperative Respiratory Complications (0.84 [95%CI 0.82–0.85] vs. 0.76 [95%CI 0.75–0.78], respectively; p < 0.001). This may allow clinicians to develop and implement strategies to decrease the risk of early postoperative tracheal re-intubation.  相似文献   
120.
ABSTRACT

Adolescents and young adults smoke waterpipe tobacco (WT) and cigarillos, at least in part, based on erroneous beliefs that these products are safer than cigarettes. To address this challenge, we used a systematic, three-phase process to develop a health communication campaign to discourage WT and cigarillo smoking among at-risk (tobacco users and susceptible non-users) 16- to 25-year-olds. In Phase 1, we used a national phone survey (N = 896) to determine salient message beliefs. Participants reported constituents (i.e., harmful chemicals) emitted by the products were worrisome. In Phase 2, we developed and evaluated four message executions, with varying imagery, tone, and unappealing products with the same constituents, using focus groups (N = 38). Participants rated one execution highly, resulting in our development of a campaign where each message: (1) identified a tobacco product and constituent in the smoke; (2) included an image of an unappealing product containing the constituent (e.g., pesticides, gasoline) to grab attention; and (3) used a humorous sarcastic tone. In Phase 3, we tested the campaign messages (17 intervention and six control) with a nationally representative online survey (N = 1,636). Participants rated intervention and control messages highly with few differences between them. Exposure to messages resulted in significant increases in all risk beliefs from pre to post (< 0.05). For WT, intervention messages increased beliefs about addiction more than control messages (p < 0.05). This systematic, iterative approach resulted in messages that show promise for discouraging WT and cigarillo use.  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