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   1345710篇
  免费   112750篇
  国内免费   6377篇
耳鼻咽喉   16850篇
儿科学   43312篇
妇产科学   36756篇
基础医学   184400篇
口腔科学   36486篇
临床医学   121267篇
内科学   280267篇
皮肤病学   32107篇
神经病学   110978篇
特种医学   55736篇
外国民族医学   274篇
外科学   211513篇
综合类   31552篇
现状与发展   2篇
一般理论   416篇
预防医学   107235篇
眼科学   28255篇
药学   94028篇
  5篇
中国医学   2256篇
肿瘤学   71142篇
  2018年   13620篇
  2017年   10794篇
  2016年   12961篇
  2015年   14462篇
  2014年   20205篇
  2013年   30053篇
  2012年   36592篇
  2011年   39320篇
  2010年   24668篇
  2009年   24135篇
  2008年   36702篇
  2007年   39159篇
  2006年   40279篇
  2005年   38840篇
  2004年   37050篇
  2003年   36126篇
  2002年   34124篇
  2001年   66277篇
  2000年   68196篇
  1999年   56784篇
  1998年   16783篇
  1997年   15069篇
  1996年   16063篇
  1995年   16266篇
  1994年   15125篇
  1993年   14185篇
  1992年   47209篇
  1991年   45843篇
  1990年   44049篇
  1989年   41888篇
  1988年   38800篇
  1987年   38126篇
  1986年   35899篇
  1985年   34676篇
  1984年   26390篇
  1983年   22135篇
  1982年   13857篇
  1981年   12459篇
  1980年   11731篇
  1979年   23568篇
  1978年   17089篇
  1977年   14389篇
  1976年   13193篇
  1975年   13737篇
  1974年   16109篇
  1973年   15417篇
  1972年   14195篇
  1971年   13051篇
  1970年   11895篇
  1969年   11120篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
103.
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   
104.
105.
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   
106.
107.
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   
108.
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   
109.
110.
We prospectively evaluated the effectiveness of contrast-enhanced ultrasonography (CEUS) for differentiation of benign versus malignant portal vein thrombosis (PVT). We studied a total of 43 patients with chronic liver disease, hepatocellular carcinoma-suggestive nodules and confirmed PVT, in whom the nature of the PVT was confirmed by follow-up imaging (US, computed tomography and/or magnetic resonance imaging) performed up to 6 mo after CEUS. PVT was assessed by US, Doppler US and CEUS with respect to vessel wall disruption and/or invasion, color Doppler vascularization, pulsed Doppler vascularization pattern and CEUS enhancement and vascularization pattern, and thrombi were classified as benign or malignant based on these findings. Follow-up studies revealed malignant PVT in 22 of the 43 patients (51%) and benign PVT in 21 patients (49%). CEUS findings were consistent with follow-up studies in 41 of the 43 patients (95%), with κ?=?0.903 (p < 0.0001), sensitivity?=?91% and specificity?=?100%, indicating that CEUS can be confidently used to differentiate benign from malignant portal vein thrombosis in the setting of chronic liver disease.  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