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   2747219篇
  免费   197171篇
  国内免费   7873篇
耳鼻咽喉   36354篇
儿科学   89800篇
妇产科学   75142篇
基础医学   386910篇
口腔科学   73772篇
临床医学   248482篇
内科学   550294篇
皮肤病学   66732篇
神经病学   228497篇
特种医学   104508篇
外国民族医学   810篇
外科学   407189篇
综合类   51097篇
现状与发展   5篇
一般理论   1013篇
预防医学   211575篇
眼科学   59922篇
药学   199526篇
  8篇
中国医学   5824篇
肿瘤学   154803篇
  2021年   22593篇
  2019年   23563篇
  2018年   34864篇
  2017年   26238篇
  2016年   29834篇
  2015年   33563篇
  2014年   44678篇
  2013年   67116篇
  2012年   92379篇
  2011年   96769篇
  2010年   56959篇
  2009年   53534篇
  2008年   89427篇
  2007年   95029篇
  2006年   95711篇
  2005年   91863篇
  2004年   88095篇
  2003年   84671篇
  2002年   81443篇
  2001年   131045篇
  2000年   134058篇
  1999年   112955篇
  1998年   31753篇
  1997年   28370篇
  1996年   28629篇
  1995年   27766篇
  1994年   25412篇
  1993年   23735篇
  1992年   86787篇
  1991年   83032篇
  1990年   80177篇
  1989年   77353篇
  1988年   70749篇
  1987年   69152篇
  1986年   64608篇
  1985年   61545篇
  1984年   45772篇
  1983年   38654篇
  1982年   22897篇
  1981年   20315篇
  1979年   39703篇
  1978年   27975篇
  1977年   23773篇
  1976年   21899篇
  1975年   23327篇
  1974年   27441篇
  1973年   26036篇
  1972年   24373篇
  1971年   22544篇
  1970年   20783篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
BACKGROUND & AIMS: Many patients with chronic hepatitis C virus (HCV) have persistently normal serum alanine transaminase (ALT) levels. We compared characteristics of chronic hepatitis C patients with patients with normal and elevated ALT levels using data from 3 randomized phase III trials of peginterferon alfa-2a (40 kDa). METHODS: The characteristics of 480 patients with normal ALT values (on >or=3 occasions without any increases in ALT level over a 6- to 18-month period) and 1993 patients with elevated ALT levels were compared. Sixty-eight of the 480 patients with normal ALT levels were randomized to no treatment and monitored for 72 weeks. RESULTS: More patients with normal ALT levels than patients with elevated ALT levels were women (59% vs 32%; P<.01). The serum HCV RNA titer was significantly lower in patients with normal ALT levels (P<.01 vs in patients with elevated ALT levels). Patients with normal ALT levels had significantly lower inflammation and fibrosis scores on liver biopsy examination than patients with elevated ALT levels, but almost two-thirds had portal fibrosis and 10% had bridging fibrosis. No correlation between baseline ALT activity, HCV RNA level, and liver histology was observed in patients with normal ALT levels. During the 72-week follow-up period, ALT activity elevated above the upper limit of normal in 53% of the untreated patients with normal levels of ALT. None became HCV RNA undetectable. CONCLUSIONS: Chronic hepatitis C patients with normal ALT levels should be evaluated in a similar manner as patients with elevated ALT levels because they are at risk for developing significant liver disease. The decision to treat with peginterferon alfa and ribavirin should be based on multiple factors, rather than on ALT levels alone.  相似文献   
993.
OBJECTIVE: Visual symptoms are common in patients with preeclampsia, and are caused by various underlying pathological changes in the retina. Blurred vision may be one of these symptoms. We describe three cases in which the underlying retinal pathology of blurred vision was clarified using optical coherence tomography (OCT), a novel, non-invasive ophthalmic imaging technique that provides micrometer-scale resolution images of the human retina. METHODS: Three patients with preeclampsia complained of blurred vision postpartum. In all cases, ophthalmoscopy was performed at the bedside, followed by the assessment of best corrected visual acuity, slit-lamp biomicroscopy, fluorescein angiography (FLA), and OCT. In all cases, the presence of central visual defects was examined by an Amsler-grid. RESULTS: In one case, the symptoms were bilateral. In all affected eyes, the patients complained of a relative central scotoma. Ophthalmoscopy showed edema in the affected maculae, while OCT examination clarified a serous neurosensory detachment of the macula. In one case, a neurosensory detachment was also detected in the papillomacular region of a fellow eye with no symptoms. In two cases, FLA was performed, but only in one case could we detect late leakage and subretinal exudates. The serous detachments observed showed total resolution in all cases within 5 to 10 weeks, with restoration of visual acuity. CONCLUSION: In patients with preeclampsia, OCT may provide a useful method for the precise assessment of retinal changes, distinguishing retinal edema from serous neurosensory detachments. This finding may help to clarify the pathophysiological circulatory changes seen in preeclampsia.  相似文献   
994.
INTRODUCTION: Transesophageal echocardiography (TEE) has become increasingly useful in the study of patients with suspected pulmonary thromboembolism. OBJECTIVE: The aim of this study was to prospectively evaluate the usefulness of TEE in the study of the distal part of the left pulmonary artery (LPA) as well as the influence of this procedure on total echocardiographic exam duration. METHODOLOGY: A prospective study in two groups of consecutive patients referred for TEE with a one- year interval between evaluation of Group A: 33 patients, 17 male, mean age 54 +/- 24 years, and Group B: 42 patients, 20 male, mean age 48 +/- 27 years (p = NS). The procedure was considered long when it took more than 3 min to evaluate the distal part of the LPA. RESULTS: In group A we were able to visualize the distal part of the LPA in 24 patients (73%) without significant prolongation of total exam duration in 16 patients (48% of group A). In one of the patients with suspected pulmonary thromboembolism thrombi were only observed in the distal part of the LPA. In group B we were able to visualize the distal part of the LPA in 36 patients (86%) without significant prolongation of total exam duration in 26 patients (61% of group B). CONCLUSIONS: 1. Visualization of the distal part of the LPA was possible in more patients, and with TEE time prolongation in less patients, in group B. These differences can be accounted for by the training of the operator in this technique. 2. The importance of visualization of this part of the LPA in guiding treatment in the subset of patients with pulmonary thromboembolism confirms the usefulness of this specific procedure.  相似文献   
995.
996.
997.
998.
999.
1000.
Eighty-nine first-degree relatives of 22 patients with an established diagnosis of hypertrophic cardiomyopathy underwent electrocardiographic and echocardiographic screening. Scalar electrocardiogram was abnormal in 30/89 (33.7%) relatives. Of these thirty, eleven had definite evidence of hypertrophic cardiomyopathy at echo; one had borderline hypertrophy and was considered neither affected nor unaffected; four had questionable signs of hypertrophy. The remaining 14 relatives had normal echo-cardiograms. Fifty-nine relatives (66.3%) had normal electrocardiograms; at echo 3 were considered to have borderline hypertrophy, 16 had questionable signs of hypertrophy and 40 were normal. In relatives of patients with hypertrophic cardiomyopathy an abnormal electrocardiogram may reflect different morphologic conditions: a real hypertrophic cardiomyopathy or a myocardial hypertrophy of uncertain significance. Furthermore, in these categories of subjects, an abnormal electrocardiogram with normal echo must be considered with caution.  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