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   15848篇
  免费   743篇
  国内免费   79篇
耳鼻咽喉   222篇
儿科学   278篇
妇产科学   155篇
基础医学   1989篇
口腔科学   429篇
临床医学   867篇
内科学   4104篇
皮肤病学   486篇
神经病学   1055篇
特种医学   707篇
外科学   2892篇
综合类   49篇
一般理论   3篇
预防医学   404篇
眼科学   158篇
药学   930篇
中国医学   21篇
肿瘤学   1921篇
  2021年   246篇
  2020年   160篇
  2019年   219篇
  2018年   238篇
  2017年   187篇
  2016年   214篇
  2015年   235篇
  2014年   311篇
  2013年   401篇
  2012年   694篇
  2011年   741篇
  2010年   425篇
  2009年   397篇
  2008年   696篇
  2007年   780篇
  2006年   742篇
  2005年   801篇
  2004年   738篇
  2003年   770篇
  2002年   711篇
  2001年   595篇
  2000年   571篇
  1999年   513篇
  1998年   200篇
  1997年   202篇
  1996年   180篇
  1995年   142篇
  1994年   132篇
  1993年   128篇
  1992年   385篇
  1991年   349篇
  1990年   326篇
  1989年   342篇
  1988年   300篇
  1987年   319篇
  1986年   278篇
  1985年   299篇
  1984年   183篇
  1983年   162篇
  1982年   79篇
  1981年   75篇
  1980年   63篇
  1979年   144篇
  1978年   80篇
  1977年   64篇
  1976年   67篇
  1975年   70篇
  1974年   81篇
  1973年   90篇
  1972年   74篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Anterior spinal artery syndrome is rare in children, especially in neonates. We present a girl with hydrops fetalis and hypothyroidism who developed flaccid paresis of both arms in the neonatal period (around day 25). MRI of the spine performed on day 52 revealed atrophic changes at C5-Th1 without Gd-DTPA-induced enhancement. Nerve conduction studies were also helpful in the diagnosis;in the upper limbs, motor potential was not elicited, while sensory nerve conduction velocity was normal. These clinical and laboratory findings suggested an atypical case of anterior spinal artery syndrome.  相似文献   
993.
994.
Hemochromatosis is a genetically heterogeneous condition. Mutations in the recently described hemojuvelin gene were found in patients with juvenile hemochromatosis, who usually manifest clinical signs of iron overload, including cardiomyopathy and hypogonadism, in their teens and early 20s. In this report, we describe three Japanese patients who showed typical clinical and hepatic histological damage compatible with hemochromatosis at around 50 years of age. Genetic analyses showed that all three patients carried mutations in the hemojuvelin gene. The first patient was homozygous for a novel mutation (745G > C [D249H]), and the second and third patients from the same family were homozygous for another novel mutation (934C > T [Q312X]). No mutations in their HFE, hepcidin, transferrin receptor 2, or ferroportin genes were found. One patient had chronic infection with Helicobacter pylori. The age at initial presentation of hemojuvelin-hemochromatosis occurs over a wider range than previously described.  相似文献   
995.
996.
OBJECTIVE: Aldosterone is produced in the ventricle of patients with hypertension. The present study was designed to examine whether adrenocorticotropic hormone (ACTH) and cortisol are also produced from the heart in patients with essential hypertension. METHODS: The study population consisted of 57 patients with essential hypertension and 28 control subjects. Plasma levels of ACTH, aldosterone, and cortisol were measured in the aortic root, the anterior interventricular vein and the coronary sinus during cardiac catheterization. RESULTS: The plasma levels of ACTH were significantly higher at the anterior interventricular vein and coronary sinus than at the aortic root (12.7 +/- 1.0 versus 10.7 +/- 0.9 pmol/l, P < 0.001; and 12.3 +/- 1.0 versus 10.7 +/- 0.9 pmol/l, P < 0.001, respectively) in the hypertension group, whereas there were no significant differences in the levels among these sites in the control group. The plasma levels of aldosterone were significantly higher at the anterior interventricular vein and the coronary sinus than at the aortic root (261.7 +/- 16.4 versus 239.1 +/- 15.1 pmol/l, P < 0.001; and 258.8 +/- 17.0 versus 239.1 +/- 15.1 pmol/l, P < 0.01, respectively) in the hypertension group, whereas there were no significant differences in the levels among these sites in the control group. CONCLUSIONS: ACTH as well as aldosterone is produced, but cortisol is not produced, from the ventricle of patients with essential hypertension.  相似文献   
997.
Synovial sarcomas are a less common cervical tumor in young patients. We report a 23-year-old man with synovial sarcoma in the submandibular region. T2-weighted MR images demonstrated a mixed-intensity tumor attached to the submandibular gland. T1-weighted MR images revealed a focal area with mildly increased signal intensity, indicating intratumoral hemorrhage. MR images were also useful for visualization of tumor extension. Synovial sarcoma should be considered in the differential diagnosis of well-defined inhomogeneous tumors adjacent to the submandibular gland in young adults.  相似文献   
998.
PURPOSE: To evaluate the usefulness of MR imaging for the detection of severe facial nerve damage in patients with facial nerve palsy. MATERIALS AND METHODS: We retrospectively reviewed 26 consecutive patients with facial nerve palsy (13 non-responders and 13 responders). T1-weighted, T2-weighted, and postcontrast T1-weighted images were obtained in all patients. FLAIR images were also obtained in 3 non-responders. RESULTS: The geniculate ganglion, labyrinthine segment, and tympanic segment or mastoid segment showed high signal intensity on T2-weighted images in 9 of 13 non-responders, whereas high signal intensity of the nerve was only seen in 1 of 13 responders. FLAIR imaging revealed high signal intensity lesions of the distal intrameatal segment in 2 non-responders. Contrast enhancement of the facial nerve showed a similar pattern in non-responders and responders. High signal intensity lesions on T2-weighted or FLAIR images showed enhancement on postcontrast T1-weighted images. CONCLUSION: These results suggest that a high signal intensity area on T2-weighted images is a marker of severe facial nerve damage. FLAIR imaging is useful for identification of T2-prolongation in the distal intrameatal segment.  相似文献   
999.
BACKGROUND AND PURPOSE: Cerebral hyperperfusion syndrome is a rare but serious complication of carotid endarterectomy (CEA). The aim of the present study was to determine whether intraoperative blood flow velocity (BFV) monitoring in the middle cerebral artery (MCA) by using transcranial Doppler ultrasonography (TCD) could be used as a reliable technique to detect cerebral hyperperfusion following CEA by comparing findings with those of brain single photon emission CT (SPECT). METHODS: Intraoperative BFV monitoring was attempted in 67 patients undergoing CEA for treatment of ipsilateral internal carotid artery (ICA) stenosis (> or =70%). Cerebral blood flow (CBF) was also assessed using SPECT, which was performed before and immediately after CEA. RESULTS: Intraoperative BFV monitoring was achieved in 60 patients. Of the 60 patients, post-CEA hyperperfusion (CBF increase > or =100%, compared with preoperative values) was observed in six patients. The sensitivity, specificity, and positive predictive value of the BFV increases immediately after declamping of the ICA for detecting post-CEA hyperperfusion was 100%, 94% and 67%, respectively, with a cut-off point 2.0-fold that of preclamping BFV. The sensitivity and specificity of the BFV increases at the end of the procedure for detecting post-CEA hyperperfusion were 100% for both parameters, with cut-off points of 2.0- to 2.2-fold BFV of preclamping value. Hyperperfusion syndrome developed in two patients with post-CEA hyperperfusion, but intracerebral hemorrhage did not occur. In one of these two patients, BFV monitoring was not possible because of failure to obtain an adequate bone window. CONCLUSION: Intraoperative MCA BFV monitoring by using TCD is a less reliable method to detect cerebral hyperperfusion following CEA than postoperative MCA BFV monitoring, provided adequate monitoring can be achieved.  相似文献   
1000.
We describe a case of carbon monoxide poisoning that led to pallidoreticular damage and delayed leukoencephalopathy. Serial diffusion-weighted MR imaging was performed. A restricted water diffusion pattern was demonstrated in the globus pallidus and substantia nigra in the early stage. Diffusion-weighted imaging is useful for early identification of the effects of acute carbon monoxide poisoning.  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