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   2613524篇
  免费   191795篇
  国内免费   7643篇
耳鼻咽喉   34728篇
儿科学   86007篇
妇产科学   72163篇
基础医学   368012篇
口腔科学   70099篇
临床医学   237608篇
内科学   521214篇
皮肤病学   62776篇
神经病学   216638篇
特种医学   101092篇
外国民族医学   736篇
外科学   391697篇
综合类   51028篇
现状与发展   6篇
一般理论   999篇
预防医学   198320篇
眼科学   57048篇
药学   190214篇
  8篇
中国医学   5378篇
肿瘤学   147191篇
  2021年   20810篇
  2019年   21380篇
  2018年   30232篇
  2017年   23236篇
  2016年   26965篇
  2015年   30382篇
  2014年   41643篇
  2013年   62052篇
  2012年   82876篇
  2011年   87187篇
  2010年   52555篇
  2009年   50558篇
  2008年   81325篇
  2007年   86205篇
  2006年   87824篇
  2005年   84062篇
  2004年   80786篇
  2003年   78030篇
  2002年   75174篇
  2001年   128719篇
  2000年   131540篇
  1999年   110781篇
  1998年   31627篇
  1997年   28235篇
  1996年   28469篇
  1995年   27628篇
  1994年   25284篇
  1993年   23622篇
  1992年   85332篇
  1991年   81706篇
  1990年   78912篇
  1989年   76179篇
  1988年   69580篇
  1987年   68094篇
  1986年   63630篇
  1985年   60590篇
  1984年   45039篇
  1983年   38035篇
  1982年   22570篇
  1981年   20106篇
  1979年   39014篇
  1978年   27494篇
  1977年   23300篇
  1976年   21542篇
  1975年   22853篇
  1974年   26813篇
  1973年   25367篇
  1972年   23755篇
  1971年   21954篇
  1970年   20179篇
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
941.
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   
942.
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   
943.
944.
945.
We have noted that colons of patients prepared for colonoscopy with Golytely, a nonabsorbable electrolyte lavage solution, frequently contain foam which may obscure small mucosal lesions. Therefore, a randomized, blinded controlled trial was performed to determine the prevalence of Golytely-induced foam and the effect of supplemental simethicone in decreasing the prevalence of foam. Foam was present in 32% of colons prepared with Golytely alone but in none of the colons prepared with Golytely supplemented with simethicone. In addition, only 5% of colons prepared with supplemental simethicone had residual stool noted at the time of colonoscopy, a significant improvement over the 39% prevalence of residual stool in colons prepared with Golytely alone. Addition of simethicone to Golytely lavage decreases the prevalence of colonic foam and residual stool.  相似文献   
946.
947.
948.
949.
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   
950.
In order to study the biological activity of endogenous digitalis-like substance (DLS) and Na-K-ATPase inhibitor (ATPI), human urine was partially purified and administered to rats, and its effects on the urinary volume, urinary Na excretion and blood pressure (BP) were determined. In addition, the effect on myocardial Na-K-ATPase activity was also measured. After the extraction of 40L of urine with a reversed phase cartridge column (S-fraction), 20 ml of chloroform was added and extraction was repeated. The chloroform layer was applied to an open silica gel column, and at a fraction with ethylacetate: methanol (60: 40, T-1 fraction), DLS and ATPI were eluted at the highest concentration. The water layer was treated with charcoal (D-1 fraction). The acute administration of K-1, T-1 fraction to rats in vivo caused significant rises in urinary volume, urinary Na excretion and BP. In chronic administration of K-1 fraction, urinary Na excretion was significantly elevated and myocardial Na-K-ATPase activity was also significantly suppressed. These results suggest that DLS and ATPI cause increase in the urinary volume and urinary Na excretion and also possess a hypertensive action; and moreover, these substance may affect the heart like cardiotonic steroids and regulate BP by increasing cardiac contractility.  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