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   16516篇
  免费   1212篇
  国内免费   70篇
耳鼻咽喉   271篇
儿科学   611篇
妇产科学   464篇
基础医学   1957篇
口腔科学   271篇
临床医学   1684篇
内科学   3671篇
皮肤病学   494篇
神经病学   1350篇
特种医学   704篇
外科学   2585篇
综合类   191篇
一般理论   20篇
预防医学   1095篇
眼科学   351篇
药学   1040篇
中国医学   32篇
肿瘤学   1007篇
  2023年   123篇
  2022年   232篇
  2021年   595篇
  2020年   348篇
  2019年   463篇
  2018年   530篇
  2017年   387篇
  2016年   429篇
  2015年   422篇
  2014年   561篇
  2013年   757篇
  2012年   1086篇
  2011年   1144篇
  2010年   615篇
  2009年   565篇
  2008年   860篇
  2007年   960篇
  2006年   872篇
  2005年   817篇
  2004年   772篇
  2003年   643篇
  2002年   576篇
  2001年   252篇
  2000年   231篇
  1999年   232篇
  1998年   137篇
  1997年   95篇
  1996年   88篇
  1995年   78篇
  1994年   78篇
  1993年   89篇
  1992年   149篇
  1991年   153篇
  1990年   127篇
  1989年   142篇
  1988年   133篇
  1987年   146篇
  1986年   153篇
  1985年   162篇
  1984年   139篇
  1983年   121篇
  1982年   93篇
  1981年   116篇
  1980年   85篇
  1979年   98篇
  1978年   82篇
  1977年   68篇
  1975年   50篇
  1974年   56篇
  1972年   50篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
An outbreak of Salmonella dublin infection occurred in England and Wales in October to December 1989. Forty-two people were affected, mainly adults, and most lived in south-east England. Microbiological and epidemiological investigations implicated an imported Irish soft unpasteurized cows' milk cheese as the vehicle of infection. A case-control study showed a statistically significant association between infection and consumption of the suspect cheese (p = 0.001). Salmonella dublin was subsequently isolated from cheeses obtained from the manufacturer's premises. Initial control measures included the withdrawal of the cheese from retail sale and a Food Hazard Warning to Environmental Health Departments, as well as a press release, from the Department of Health. Subsequently, a decision was taken by the manufacturer to pasteurize milk used in the production of cheese for the UK market and importation of the cheese resumed in June 1990.  相似文献   
33.
Our group has previously reported significant changes in the incorporation of precursors into glycerophospholipids, particularly phosphatidylserine, in polymorphonuclear cells obtained from the peripheral blood of cluster headache patients, when compared with controls. The potential of these results led to further work using both the previous methodology and a modified isolation technique to obtain polymorphonuclear cells in as pure a state as possible. Neither the new results obtained using the original technique, nor the results with high purity polymorphonuclear cells from controls and cluster headache patients, confirm the marked changes in precursor uptake into glycerophospholipids originally reported.  相似文献   
34.
35.
36.
Background: During labor, ephedrine is widely used to prevent or to treat maternal arterial hypotension and restore uterine perfusion pressure to avoid intrapartum fetal asphyxia. However, the effects of ephedrine on uterine blood flow have not been studied during uterine contractions. The purpose of the study was to assess the effects of ephedrine on uterine artery velocities and resistance index using the Doppler technique during the active phase of labor.

Methods: Ten normotensive, healthy parturients with uncomplicated pregnancies at term received intravenous ephedrine during labor to increase mean arterial pressure up to a maximum of 20% above their baseline pressure. Peak systolic and end-diastolic Doppler flow velocities and resistance indices were measured in the uterine artery before and immediately after administration of bolus intravenous ephedrine and after ephedrine washout. Umbilical and fetal middle cerebral arterial resistance indices and fetal heart rate were also calculated.

Results: After ephedrine administration, mean arterial pressure increased by 17 +/- 4%. End-diastolic flow velocity in the uterine artery at peak amplitude of uterine contraction was restored to 74% of the value observed in the absence of contraction. The systolic velocity was totally restored, and the uterine resistance index was significantly decreased, compared with the values in the absence of contraction. Between uterine contractions, ephedrine induced similar but less marked effects. Fetal hemodynamic parameters were not altered by ephedrine administration.  相似文献   

37.
CT of fatty thoracic masses.   总被引:2,自引:0,他引:2  
  相似文献   
38.
39.

Background:   

Cases of extrahepatic biliary tree trauma are not as common as other intraabdominal injuries and may pose a diagnostic and therapeutic challenge.  相似文献   
40.
BACKGROUND CONTEXT: Diastematomyelia is uncommon and rarely presents in adulthood. This report draws attention to the fact that patients who underwent spinal fusion for deformity before the widespread use of computed tomography (CT) and magnetic resonance imaging (MRI) may have unrecognized spinal cord abnormalities. This should be considered if revision surgery is contemplated. PURPOSE: This case report focuses on the late presentation of lower-extremity weakness in a 44-year-old woman with a split cord malformation (diplomyelia), diastematomyelia and tethered cord syndrome. STUDY DESIGN/SETTING: METHODS: The patient underwent instrumented posterior spinal fusion with a Harrington rod as a child for progressive thoracolumbar scoliosis. As an adult, she developed paraparesis after a traumatic event.The patient underwent decompressive laminectomy, subtotal resection of the old fusion mass and resection of the osseous septum. Postoperatively, an anterior spinal fluid leak in the lower thoracic region required repeated fascial grafting, resection of a pseudomeningocele and reverse left latissimus dorsi flap transfer. The leak was controlled, and the patient had near complete resolution of her paraparesis 1 year after her surgery. RESULTS: The case described herein is unusual in that patients with diplomyelia and diastematomyelia rarely are symptomatic in adulthood. However, trauma may precipitate the onset of neurologic symptoms. This patient underwent spinal surgeries to address deformity, pain and progressive lower-extremity weakness. Preoperative CT and MRI studies showed a split cord malformation and diastematomyelia at L1-L2 with spinal stenosis and tethering of both hemicords. CONCLUSIONS: Progressive weakness without any previous neurologic deficit or neurocutaneous stigmas of an underlying spinal cord abnormality may develop in the adult with unrecognized diastemotomyelia. This case demonstrates that a thorough preoperative workup of patients with complex spinal deformities is imperative.  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