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   16004篇
  免费   1179篇
  国内免费   92篇
耳鼻咽喉   266篇
儿科学   655篇
妇产科学   450篇
基础医学   1954篇
口腔科学   253篇
临床医学   1676篇
内科学   3600篇
皮肤病学   496篇
神经病学   1285篇
特种医学   619篇
外科学   2550篇
综合类   191篇
一般理论   20篇
预防医学   1000篇
眼科学   340篇
药学   982篇
中国医学   32篇
肿瘤学   906篇
  2023年   113篇
  2022年   182篇
  2021年   587篇
  2020年   343篇
  2019年   460篇
  2018年   525篇
  2017年   382篇
  2016年   428篇
  2015年   419篇
  2014年   562篇
  2013年   757篇
  2012年   1066篇
  2011年   1097篇
  2010年   609篇
  2009年   565篇
  2008年   842篇
  2007年   945篇
  2006年   844篇
  2005年   794篇
  2004年   738篇
  2003年   629篇
  2002年   549篇
  2001年   229篇
  2000年   207篇
  1999年   220篇
  1998年   176篇
  1997年   130篇
  1996年   113篇
  1995年   84篇
  1994年   96篇
  1993年   91篇
  1992年   134篇
  1991年   138篇
  1990年   120篇
  1989年   130篇
  1988年   133篇
  1987年   117篇
  1986年   124篇
  1985年   120篇
  1984年   112篇
  1983年   92篇
  1982年   97篇
  1981年   111篇
  1980年   76篇
  1979年   86篇
  1978年   77篇
  1977年   70篇
  1976年   49篇
  1975年   47篇
  1974年   51篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
31.
32.
33.
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   

34.
35.
36.
37.

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   
38.
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   
39.
40.
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