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   2918篇
  免费   226篇
  国内免费   50篇
耳鼻咽喉   9篇
儿科学   154篇
妇产科学   37篇
基础医学   391篇
口腔科学   40篇
临床医学   245篇
内科学   626篇
皮肤病学   40篇
神经病学   295篇
特种医学   379篇
外科学   301篇
综合类   32篇
预防医学   175篇
眼科学   104篇
药学   147篇
中国医学   1篇
肿瘤学   218篇
  2021年   26篇
  2019年   46篇
  2018年   36篇
  2017年   24篇
  2016年   33篇
  2015年   43篇
  2014年   61篇
  2013年   85篇
  2012年   100篇
  2011年   104篇
  2010年   83篇
  2009年   70篇
  2008年   111篇
  2007年   131篇
  2006年   120篇
  2005年   117篇
  2004年   103篇
  2003年   80篇
  2002年   99篇
  2001年   80篇
  2000年   101篇
  1999年   84篇
  1998年   78篇
  1997年   66篇
  1996年   59篇
  1995年   48篇
  1994年   65篇
  1993年   48篇
  1992年   62篇
  1991年   62篇
  1990年   68篇
  1989年   103篇
  1988年   85篇
  1987年   69篇
  1986年   69篇
  1985年   60篇
  1984年   51篇
  1983年   38篇
  1982年   26篇
  1981年   27篇
  1980年   27篇
  1979年   23篇
  1978年   19篇
  1977年   21篇
  1976年   21篇
  1975年   20篇
  1974年   18篇
  1973年   19篇
  1969年   20篇
  1968年   18篇
排序方式: 共有3194条查询结果,搜索用时 15 毫秒
1.
PurposeTwitter is an increasingly popular social media platform within the health care community. The objective of this analysis is to characterize the profile of radiation oncology–related tweets and Twitter users over the past 6 years.Methods and MaterialsUsing the web-based social media analytics platform Symplur Signals, we filtered tweets containing at least 1 of the following hashtags or key words: #radonc, #radiationoncology, "rad onc," or "radiation oncology." We evaluated radiation oncology–related Twitter activity between October 2014 and March 2020 for tweet frequency, tweet content, and individuals or groups posting tweets. We identified the most influential Twitter users contributing to radiation oncology–related tweets.ResultsFrom 2014 to 2020, the quarterly volume of radiation oncology–related tweets increased from 5027 to 29,763. Physicians contributed the largest growth in tweet volume. Academic radiation oncologists comprise 60% of the most influential Twitter accounts responsible for radiation oncology–related content. The number of radiation-oncology resident physicians on Twitter increased from 25 to 328 over the past 6 years, and 20% of radiation-oncology residency programs have a Twitter account. Seventy-one percent of radiation oncology–related tweets generated direct communication via mentions, and 59% of tweets contain links to external sources, including scientific articles.ConclusionsThe number of physicians contributing radiation oncology–related Twitter content has increased significantly in recent years. Academic radiation oncologists are the primary influencers of radiation oncology–related Twitter activity. Twitter is used by radiation oncologists to both professionally network and discuss findings related to the field. There remains the opportunity for radiation oncologists to broaden their audience on Twitter to encompass a more diverse community, including patients.  相似文献   
2.
Abstract: Establishment of mixed bone marrow chimerism in pig-to-primate transplantation, as a means of inducing specific immune tolerance, will require that both immune and nonimmune barriers be overcome. As a preliminary step in evaluating nonimmune barriers in this system, we have developed an in vitro model of engraftment in which long-term culture of porcine bone marrow-derived hematopoietic cells is supported on preformed primate bone marrow stromal layers. In the absence of cytokine supplementation, primate stromal cells were unable to support long-term porcine hematopoiesis in these cultures. Supplementation with porcine Steel Factor was required for long-term maintenance of hematopoietic progenitor cell content and total hematopoietic activity. Addition of porcine IL-3, in combination with porcine Steel Factor, increased long-term progenitor cell content and hematopoietic activity on primate stroma to levels comparable to that obtained in cultures on porcine stroma. The combination of porcine GM-CSF and Steel Factor increased progenitor cell content and hematopoietic activity early in the cultures, but had little effect in long-term cultures. The Steel Factor and IL-3 combination was species-specific in its action in these cultures, as the corresponding human cytokines were unable to effectively support long-term porcine hematopoiesis. Likewise, the combination of porcine cytokines had only minimal effects on long-term bone marrow culture of primate CD34+ cells I on primate stroma.  相似文献   
3.
Thirty-seven children and adolescents on renal replacement therapy (11 on haemodialysis, 14 on continuous ambulatory peritoneal dialysis and 12 after renal transplantation) were studied by echocardiography, echo-Doppler and phonocardiography. Right and left ventricular (R/L V) diastolic functions were measured by transmitral and transtricuspid flow velocities and by LV isovolumic relaxation time (LVIRT). Thirty-seven age- and sex-matched healthy subjects served as controls. R/L V diastolic dysfunction was only observed in the dialysis patients. In these patients LVIRT was prolonged. LV and RV peak inflow velocities were increased both in early (E) and late (A) diastole with a reduction in the E/A ratios. This pattern of diastolic dysfunction is compatible with the combined effects of a hypercirculatory state (volume overload, anaemia, arteriovenous fistula) and an abnormality of cardiac relaxation. The transplant patients showed no major cardiac abnormalities.  相似文献   
4.
We used vitreous surgery to remove idiopathic epiretinal membranes from the macular area in 70 consecutive cases. The abnormal tissue was successfully removed in each case. Vision improved postoperatively in 61 eyes (87%), remained unchanged in six eyes (9%), and worsened in three eyes (4%). However, at the time of final examination vision was improved in only 47 eyes (67%), primarily because of the occurrence or progression of nuclear sclerosis, which occurred in 38 of 60 phakic eyes (63%). Four preoperative factors were associated with final visual acuity of 20/60 or better: (1) initial vision of 20/100 or better, (2) shorter preoperative duration of blurred vision, (3) thin epiretinal membrane, and (4) absence of traction retinal detachment.  相似文献   
5.
PURPOSE: To compare tests for intestinal function with clinical scores after abdominal irradiation. PATIENTS AND METHODS: At the Department of Radiotherapy, Erfurt, Germany, intestinal changes were studied in 91 patients receiving abdominal radiotherapy between 1992 and 1996. Conventional fractionation (1.8-2 Gy per fraction, total doses 30.6-62.5 Gy) was applied. Before and at weekly intervals during radiotherapy, the clinical response was scored according to RTOG/EORTC for the upper and lower gastrointestinal (GI) tract. Resorption tests for vitamin B(12) and D-xylose were performed before the onset and immediately after treatment. RESULTS: The clinical response displayed a well-defined dose-effect relationship with grade 1 effects in 5% and 50% of the patients at about 10 Gy and 50 Gy, respectively. For grade 2 reactions, 5%- and 50%-effective doses were 20-30 Gy and 60-80 Gy. Effects in the upper and lower GI tract were highly correlated. Changes in body weight did not show a correlation with other clinical symptoms. Changes in resorption also displayed a significant dose effect. However, no correlation was found with the clinical symptoms in the individual patient. CONCLUSION: In the present study, the clinical manifestation of intestinal side effects according to RTOG/EORTC criteria was reflected by neither the vitamin B(12) nor by the D-xylose resorption test. Hence, these tests cannot be regarded as useful for objective quantitation of intestinal radiation injury.  相似文献   
6.
7.
8.
SUMMARY A case congenital dislocation of both knees and dislocation of the left hip in an infant whose mother had a chronic amniotic fluid leakage after mid-trimester amniocentesis.  相似文献   
9.
10.
Vitrectomy for impending idiopathic macular holes   总被引:7,自引:0,他引:7  
We performed pars plana vitrectomy in 15 patients with physical changes and visual loss believed to indicate impending macular hole formation. Twelve (80%) of 15 eyes have not progressed to macular holes during a minimum follow-up period of 15 months (average, 26 months). In these 12 patients final vision was within one line of the preoperative vision in four eyes, improved two or more lines in five eyes, and was two lines worse in three eyes. Decreased vision in all three eyes was the result of progressive lenticular nuclear sclerosis. A thin sheet of cortical vitreous fibers was sometimes found intraoperatively on the surface of the retina, despite an apparent complete posterior vitreous detachment.  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