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   2075334篇
  免费   143058篇
  国内免费   4150篇
耳鼻咽喉   26903篇
儿科学   67729篇
妇产科学   55655篇
基础医学   305876篇
口腔科学   58211篇
临床医学   186833篇
内科学   400859篇
皮肤病学   47275篇
神经病学   155922篇
特种医学   78255篇
外国民族医学   293篇
外科学   313422篇
综合类   44520篇
现状与发展   5篇
一般理论   620篇
预防医学   153356篇
眼科学   49212篇
药学   152366篇
  8篇
中国医学   5134篇
肿瘤学   120088篇
  2019年   16115篇
  2018年   23728篇
  2017年   17917篇
  2016年   19848篇
  2015年   22483篇
  2014年   31052篇
  2013年   45206篇
  2012年   63479篇
  2011年   67292篇
  2010年   39636篇
  2009年   36913篇
  2008年   62438篇
  2007年   66978篇
  2006年   67013篇
  2005年   64007篇
  2004年   61878篇
  2003年   59046篇
  2002年   56906篇
  2001年   106215篇
  2000年   108381篇
  1999年   89415篇
  1998年   23370篇
  1997年   20401篇
  1996年   20426篇
  1995年   19614篇
  1994年   17900篇
  1993年   16631篇
  1992年   67264篇
  1991年   66154篇
  1990年   64142篇
  1989年   61695篇
  1988年   56367篇
  1987年   55128篇
  1986年   51793篇
  1985年   49240篇
  1984年   36217篇
  1983年   30771篇
  1982年   17037篇
  1979年   32358篇
  1978年   22494篇
  1977年   18841篇
  1976年   18061篇
  1975年   19695篇
  1974年   23411篇
  1973年   22560篇
  1972年   20878篇
  1971年   19479篇
  1970年   18161篇
  1969年   16930篇
  1968年   15889篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
91.
The finer branches of the biliary tree (FBBT) contain a regenerative compartment. We hypothesized that preservation of the FBBT together with its microvasculature will lead to recovery of biliary damage and prolonged preservation of bile ductules during the development of chronic liver allograft rejection. The interlobular bile ducts, portal bile ductules and extraportal biliary cells with and without microvessels were studied in sequential biopsies in five patients who fulfilled the Banff criteria of early chronic rejection (CR) (imminence group). Biopsies of CR patients (n = 12) served as controls. Biopsies were double immunostained with CD34 (microvessels) and cytokeratin 7 (biliary structures). Proliferation and proangiogenic activity were assessed with Ki67 and VEGF-A immunostaining. Severe damage of bile ducts in the imminence group did not progress to significant bile duct loss. This was associated with a high proliferative activity in all biliary structures and preservation of the microvascular compartment. VEGF-A expression was increased in all but the reperfusion biopsies. In conclusion, both regenerative activity of the FBBT and an intact microvascular compartment are associated with less damage of the biliary tree and could therefore be prerequisites for biliary regeneration.  相似文献   
92.
The reliable change index (RCI) expresses change relative to its associated error, and is useful in the identification of post-operative cognitive dysfunction (POCD). This paper examines four common RCIs that each account for error in different ways. Three rules incorporate a constant correction for practice effects and are contrasted with the standard RCI that had no correction for practice. These rules are applied to 160 patients undergoing coronary artery bypass graft (CABG) surgery who completed neuropsychological assessments preoperatively and 1 week post-operatively using error and reliability data from a comparable healthy non-surgical control group. The rules all identify POCD in a similar proportion of patients, but the use of the within subject standard deviation, expressing the effects of random error, as an error estimate is a theoretically appropriate denominator when a constant error correction, removing the effects of systematic error, is deducted from the numerator in a RCI.  相似文献   
93.
94.
BACKGROUND: We prospectively evaluated the usefulness of IgA tissue transglutaminase antibodies (IgA tTG) in the initial diagnosis of celiac disease (CD) and compared its diagnostic potential with that of IgA anti-endomysial antibodies (IgA EMA) and anti-IgA and IgG gliadin antibodies (AGA and AGG, respectively). METHODS: Sera of 23 untreated children fulfilling the revised ESPGHAN criteria for diagnosis of CD (Group I; mean age 10.8 y); 19 disease controls (Group II; mean age 8.5 y) presenting with chronic diarrhea, short stature or both; and 22 healthy children (Group III; mean age 8.8 y) were studied. These were tested in a blinded manner for AGA, AGG, IgA tTG (guinea pig as antigen) and IgA EMA. RESULTS: In Group I, IgA EMA was positive in 19, IgA tTG in 17, AGA in 14 and AGG in 17 patients. In Group II, these tests were positive in 1, 0, 2 and 14 patients, respectively and in Group III, in 0, 0, 0 and 1 child, respectively. Analyzing data from Group I and II, IgA EMA, IgA tTG, AGA and AGG had sensitivity rates of 83%, 74%, 61% and 74%, respectively; the specificity rates were 95%, 100%, 89% and 26%; positive predictive values were 95%, 100%, 88% and 55% and negative predictive values were 82%, 74%, 65% and 45%, respectively. CONCLUSION: IgA tTG is useful for the diagnosis of CD, with sensitivity and specificity rates comparable to those of EMA and this test is well suited for use in tropical countries like India.  相似文献   
95.
OBJECTIVE: This study was conducted to compare an otolaryngologist's experience with a cohort of epilepsy patients implanted with a vagal nerve stimulator (VNS) to previously published data. METHODS: Demographics, preoperative seizure frequency, medications, and complications were retrospectively collected from patients implanted by the senior author. Postoperative medications and seizure frequency were obtained from referring neurologists. RESULTS: Seventeen patients were implanted over a 24-month period. Average age was 28.3 years. Patients presented with petit mal (n = 3), tonic-clonic (n = 6), complex partial (n = 5), and grand mal (n = 8) seizures. Mean follow-up postimplantation was 13.5 months. Most patients had at least a 50% reduction of seizure frequency, with 3 patients being seizure free. There were no postoperative infections. One patient had left vocal cord immobility. The most common side effect was voice disturbance during device activation. CONCLUSION: Otolaryngologists are well equipped to perform VNS implantation and to diagnose and treat possible laryngeal side effects. EBM rating: C-4.  相似文献   
96.
97.
98.
99.
OBJECTIVES: Pseudotumour cerebri has been previously recognized as a neurological side effect of combined oral contraceptives but has not been diagnosed with a delay of 3 years after initiation of combined oral contraceptives. CASE REPORT: A 19-year-old obese woman developed visual impairment and headache, 4 months after starting combined oral contraceptives. Three years later symptoms deteriorated and she presented with prominent tendon-jerks and congested optical-discs. Normal CSF drained with high pressure from the spinal tap. Pseudotumour cerebri was diagnosed. Headache and visual impairment resolved within 3 weeks after discontinuation of combined oral contraceptives. CONCLUSIONS: Combined oral contraceptives-induced pseudotumour cerebri may remain undetected for years. Young, obese women with visual impairment and headache under combined oral contraceptives should undergo immediate neurological and ophthalmological investigation.  相似文献   
100.
A 41-year-old Chinese lady had a Gr?fenberg ring in utero for 15 years. During that period of time, she had one normal vaginal delivery a year after insertion, followed by an ectopic pregnancy 12 years later. We discuss the possible mechanism of action of the Gr?fenberg ring and sequelae of its prolonged presence in the uterus.  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