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   1380篇
  免费   59篇
  国内免费   33篇
耳鼻咽喉   27篇
儿科学   82篇
妇产科学   25篇
基础医学   115篇
口腔科学   27篇
临床医学   133篇
内科学   378篇
皮肤病学   109篇
神经病学   37篇
特种医学   207篇
外科学   129篇
综合类   29篇
预防医学   82篇
眼科学   6篇
药学   37篇
中国医学   3篇
肿瘤学   46篇
  2020年   7篇
  2019年   9篇
  2018年   7篇
  2017年   13篇
  2016年   17篇
  2015年   22篇
  2014年   27篇
  2013年   67篇
  2012年   15篇
  2011年   17篇
  2010年   49篇
  2009年   58篇
  2008年   22篇
  2007年   33篇
  2006年   27篇
  2005年   34篇
  2004年   17篇
  2003年   15篇
  2002年   26篇
  2001年   22篇
  2000年   15篇
  1999年   22篇
  1998年   85篇
  1997年   74篇
  1996年   76篇
  1995年   50篇
  1994年   62篇
  1993年   52篇
  1992年   15篇
  1991年   18篇
  1990年   22篇
  1989年   45篇
  1988年   45篇
  1987年   38篇
  1986年   33篇
  1985年   27篇
  1984年   26篇
  1983年   16篇
  1982年   23篇
  1981年   20篇
  1980年   13篇
  1979年   17篇
  1978年   14篇
  1977年   16篇
  1976年   16篇
  1975年   13篇
  1973年   14篇
  1972年   10篇
  1971年   8篇
  1957年   7篇
排序方式: 共有1472条查询结果,搜索用时 234 毫秒
81.
Background: Emergency physicians commonly perform Focused Assessment with Sonography for Trauma (FAST) examinations to evaluate for free intraperitoneal fluid. Many ultrasound findings can be misinterpreted as free fluid, resulting in false-positive FAST examinations. Objectives: To describe a previously unreported ultrasound finding that can be misinterpreted as free intraperitoneal fluid. Case Report: A 32-year-old man was stabbed in the left upper abdomen. A FAST examination was performed and a right perinephric fat pad was interpreted as showing free fluid in Morison's pouch. After transfer to a trauma center, a repeat FAST examination revealed no signs of intraperitoneal free fluid. Wound exploration showed no signs of penetration into the peritoneal cavity. Conclusions: When performing a FAST examination, a wedge-shaped hypoechoic area in Morison's pouch that is bounded on both sides by echogenic lines (the “FAST Double-Line Sign”) is likely to represent perinephric fat and may result in a false-positive FAST examination.  相似文献   
82.
83.
To assess the dosimetric effect of using interpolated contours in planning intensity‐modulated radiation therapy (IMRT) for advanced T‐stage nasopharyngeal carcinoma. The present study focused on T3–T4 tumours where the proximity of targets to neurological organs poses a stringent test on the feasibility of such an approach. Contours of targets and organs were delineated on CT images of 2.5‐mm interval and a reference IMRT plan was generated. An investigative (INV) IMRT plan was then generated with the same planning protocol, but based on interpolated contours that replaced deleted contours on alternate slices. The reference and INV plans were compared. Regarding target coverage, all targets in the INV plans met the acceptance criteria except for the PTV in one case. Regarding organs, the mean dose to 1% volume of the brainstem and spinal cord in the INV plans were kept below their dose limits. No significant differences in the mean doses to others organs were found. Satisfactory target coverage and protection of critical organs to a degree similar to full‐scale contouring could be achieved with use of interpolated contours. The saving in manpower time for contouring is expected to significantly improve the throughput of the IMRT planning process.  相似文献   
84.

Background  

In patients with type 2 diabetes, the risk for cardiovascular disease is substantial. To achieve a more favourable risk profile, lifestyle changes on diet, physical activity and smoking status are needed. This will involve changes in behaviour, which is difficult to achieve. Cognitive behavioural therapies focussing on self-management have been shown to be effective. We have developed an intervention combining techniques of Motivational Interviewing (MI) and Problem Solving Treatment (PST). The aim of our study is to investigate if adding a combined behavioural intervention to managed care, is effective in achieving changes in lifestyle and cardiovascular risk profile.  相似文献   
85.
To determine whether a single prophylactic dose of synthetic surfactant would reduce mortality and morbidity rates, we performed a randomized, controlled trial of Exosurf Neonatal at 19 hospitals in the United States. The Exosurf preparation (5 ml/kg) was instilled into the endotracheal tube of premature infants weighing 700 to 1100 gm during mechanical ventilation, as soon as practical after birth. Control infants were treated with air (5 ml/kg). Dose administration was performed in secrecy by clinicians who did not reveal for 2 years what they had instilled. A total of 222 infants received air and 224 received the synthetic surfactant; 36 infants with congenital pneumonia or malformations were excluded from the primary efficacy analysis. By the age of 28 days, there were 44 deaths in the air group and 27 deaths in the surfactant group (p = 0.022). By the age of 1 year after term there were 61 deaths in the air group and 35 deaths in the surfactant group (p = 0.002). Although there was no reduction in the incidence of respiratory distress syndrome, a significant reduction in the number of deaths attributed to respiratory distress syndrome, a significant reduction in the incidence of pulmonary air leaks, and significantly lower requirements for oxygen and mean airway pressure indicated that lung disease was less severe in the Exosurf-treated infants. There were no significant differences in the incidence of complications such as bronchopulmonary dysplasia, intraventricular hemorrhage, patent ductus arteriosus, necrotizing enterocolitis, and infection. The results indicate that a single prophylactic dose of Exosurf, in high-risk premature infants treated soon after birth, reduces the number of deaths from respiratory distress syndrome and the overall mortality rate.  相似文献   
86.
The folic acid antagonist, methotrexate, has many applications in the treatment of neoplastic disease. While methotrexate produces several well-recognized toxic effects, cutaneous reactions are rare. A patient who developed classical erythema multiforme while receiving low-dose methotrexate as treatment of nonmetastatic gestational trophoblastic neoplasia is presented. Erythema multiforme has been associated with a variety of pharmacologic agents. It typically presents as a pruritic papular dermatitis of the extensor surfaces of the extremities and may require multiple skin biopsies to establish the diagnosis. Spontaneous reversal usually occurs with discontinuation of therapy. Patients developing erythema multiforme related to antineoplastic agents should be switched to an alternate regimen.  相似文献   
87.
An enquiry into sudden infant death syndrome (SIDS) in 1987 furnished us with detailed epidemiological data for 281 cases that underwent a thorough post-mortem examination. This analysis uses these data to evaluate the role the autopsy plays in explaining sudden death. The cases were classified into three diagnostic groups: explained causes of death (group 1), unexplained deaths with anomalies (group 2), and no anomaly (group 3). These 281 cases show the three essential features that characterize SIDS: over-representation of males, increased deaths during the second and third months of life, and increased deaths during winter. The autopsy examination revealed that many of these deaths had a medical explanation. Almost half were assigned to group 1. At the time of autopsy, no precise pathology could be diagnosed for 147 deaths; of these, 140 showed histological anomalies. There were only seven sudden deaths for which no abnormal sign was evident at the autopsy. These results are compared with those of similar studies and discussed in connection with three factors: the initial selection of cases, the nature and degree of the investigations, and the possible interpretations of the symptoms uncovered.  相似文献   
88.
Fragile X syndrome is the most common inherited cause of mental retardation. Early diagnosis is important not only for appropriate management of individuals but also to identify carriers who are unaware of their high risk of having an affected child. The disorder is associated with a cytogenetically visible fragile site (FRAXA) at Xq27.3, caused by amplification of a (CGG)n repeat sequence within the gene at this locus designated FMR1. Clinical and molecular studies have been undertaken to screen for fragile X syndrome in 154 children with moderate and severe learning difficulties of previously unknown origin. Southern blot analysis of peripheral blood showed the characteristic abnormally large (CGG)n repeat sequence associated with fragile X syndrome in four of the 154 children. The findings were confirmed by cytogenetic observation of the fragile site and by further molecular studies. The families of the affected children were offered genetic counselling and DNA tests to determine their carrier status. These findings show that there are still unrecognised cases of fragile X syndrome. Given the difficulty of making a clinical diagnosis and the implications for families when the diagnosis is missed, screening in high risk populations may be justified. The issues involved in screening all children in special schools for fragile X syndrome are discussed.  相似文献   
89.
Colostrum protects the newborn from intestinal infection by its content of secretory immunoglobulin A and other immediately acting factors. It may also induce maturation of the child's gastrointestinal immune defences, thus contributing to the protection against diarrhoeal disease later in infancy. To test this hypothesis, a case–control study on breast feeding and diarrhoea was carried out in a periurban community in Guinea–Bissau. The child's age at the start of breast feeding was ascertained soon after birth ( n = 279). Subsequent cases of acute diarrhoea ( n = 66) were identified at 3–monthly examinations, and four concurrent controls were randomly selected among attendants. Three separate estimates of association showed that the cases tended to have started breast feeding later after birth than the diarrhoea–free controls, but no single test was statistically significant. Early breast feeding might have consequences for diarrhoeal morbidity after the neonatal period.  相似文献   
90.
Neonatal high-frequency jet ventilation   总被引:1,自引:0,他引:1  
T Pokora  D Bing  M Mammel  S Boros 《Pediatrics》1983,72(1):27-32
Ten neonates with intractable respiratory failure were treated with high-frequency jet ventilation (HFJV). Nine had progressive pulmonary air leaks with either bronchopleural fistulas or pulmonary interstitial emphysema as the primary cause of their respiratory failure. Following HFJV, x-ray film evidence of pulmonary air leaks decreased in seven of the nine neonates. PaO2/FIO2 increased in eight of the ten patients (P less than .05), and PaCO2 values decreased in nine of the ten patients (P less than .01). Five patients survived. Three of the six patients exposed to HFJV for more than 20 hours developed significant tracheal obstruction. From this experience, it may be concluded that HFJV can successfully ventilate certain neonates with intractable respiratory failure secondary to progressive pulmonary air leaks. In its present form, long-term neonatal HFJV carries a risk of airway obstruction and/or damage.  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