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   862751篇
  免费   70498篇
  国内免费   1840篇
耳鼻咽喉   12801篇
儿科学   24630篇
妇产科学   25106篇
基础医学   124274篇
口腔科学   25497篇
临床医学   75361篇
内科学   164680篇
皮肤病学   16980篇
神经病学   70151篇
特种医学   35209篇
外国民族医学   171篇
外科学   136248篇
综合类   24606篇
现状与发展   2篇
一般理论   263篇
预防医学   66959篇
眼科学   20519篇
药学   64725篇
中国医学   1593篇
肿瘤学   45314篇
  2018年   7343篇
  2015年   7753篇
  2014年   11128篇
  2013年   16803篇
  2012年   22755篇
  2011年   23861篇
  2010年   13889篇
  2009年   13079篇
  2008年   22599篇
  2007年   24658篇
  2006年   24521篇
  2005年   24164篇
  2004年   23713篇
  2003年   22857篇
  2002年   21941篇
  2001年   35838篇
  2000年   36480篇
  1999年   30919篇
  1998年   9220篇
  1997年   8548篇
  1996年   8482篇
  1995年   8010篇
  1994年   7727篇
  1992年   26669篇
  1991年   26107篇
  1990年   25622篇
  1989年   24684篇
  1988年   23225篇
  1987年   22891篇
  1986年   21747篇
  1985年   21100篇
  1984年   16388篇
  1983年   14001篇
  1982年   8855篇
  1981年   8203篇
  1980年   7677篇
  1979年   16744篇
  1978年   12117篇
  1977年   10183篇
  1976年   9330篇
  1975年   10148篇
  1974年   12646篇
  1973年   12139篇
  1972年   11539篇
  1971年   10687篇
  1970年   10219篇
  1969年   9910篇
  1968年   8901篇
  1967年   8232篇
  1966年   7654篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Two postal questionnaire surveys were carried out among the adult population of Southampton aimed at clarifying the diagnostic criteria for asthma (study 1) and at testing the validity of symptoms so identified as diagnostic of bronchial hyper-reactivity (study 2). The questionnaires asked about respiratory symptoms and included three questions thought likely to disclose increased bronchial reactivity. Laboratory measurements on subsamples of respondents included spirometry and bronchial challenge with increasing doses of histamine till a concentration was reached provoking a fall of more than 20% (PC greater than 20) in forced expiratory volume in one second. In the first study no normal subject (that is, one who did not report shortness of breath or wheezing on the questionnaire) had a PC greater than 20 below 0.5 g/l. Of 51 subjects who reported shortness of breath or wheezing, or both, nine had a cluster of abnormalities consisting of one or more symptoms of bronchial irritability, nocturnal dyspnoea, and prolonged morning tightness together with PC greater than 20 values of 0.5 g/l or less. These symptoms in conjunction with a low PC greater than 20 were termed the bronchial irritability syndrome. In the second study bronchial challenge confirmed the close association of these symptoms with bronchial hyper-reactivity, all other subjects being less reactive to histamine. Only 27% of subjects with symptoms of the bronchial irritability syndrome had been diagnosed as asthmatic by their general practitioners. The bronchial irritability syndrome is a definable entity for epidemiological study and patient care.  相似文献   
992.
993.
994.
The surgical risk of colectomy in patients with cirrhosis   总被引:5,自引:1,他引:4  
The records of 54 patients with documented cirrhosis who underwent colectomy between January 1970 and January 1984 were studied to assess the operative risk and to determine the preoperative predictive risk factors. In-hospital mortality was 24 percent (13 patients), and postoperative complications occurred in 48 percent (26 patients). The risk of surgical intervention was significantly increased if encephalopathy, ascites, anemia, or hypoalbuminemia was present before operation. A simple operative risk index involving the presence of encephalopathy and ascites and the levels of hemoglobin and albumin is proposed to help distinguish a low-risk subgroup in whom postoperative mortality was 12.8 percent from a high-risk subgroup in whom postoperative mortality was 53.3 percent.  相似文献   
995.
Background: Bupivacaine retards myocardial acidosis during ischemia. The authors measured function of rat isolated hearts after prolonged storage to determine whether bupivacaine improves cardiac protection compared with standard cardioplegia alone.

Methods: After measuring cardiac function on a Langendorff apparatus, hearts were perfused with cardioplegia alone (controls), cardioplegia containing 500 [mu]m bupivacaine, or cardioplegia containing 2 mm lidocaine; were stored at 4[degrees]C for 12 h; and were then reperfused. Heart rate and left ventricular developed pressures were measured for 60 min. Maximum positive rate of change in ventricular pressure, oxygen consumption, and lactate dehydrogenase release were also measured.

Results: All bupivacaine-treated, four of five lidocaine-treated, and no control hearts beat throughout the 60-min recovery period. Mean values of heart rate, left ventricular developed pressure, maximum positive rate of change in ventricular pressure, rate-pressure product, and efficiency in bupivacaine-treated hearts exceeded those of the control group (P < 0.001 at 60 min for all). Mean values of the lidocaine group were intermediate. Oxygen consumption of the control group exceeded the other groups early in recovery, but not at later times. Lactate dehydrogenase release from the bupivacaine group was less than that from the control group (P < 0.001) but did not differ from baseline.  相似文献   

996.
997.
998.
999.
The following declaration was agreed by all participants at the conclusion of the 5th World Workshop on Oral Health and Disease in AIDS. It is reproduced here to draw attention to the world's oral health scientists, and others, of the burden that oral disease causes to those who are HIV positive, and to the important role of the dental and allied oral health professions in caring for these individuals and in the research which will underpin improved understanding and care.  相似文献   
1000.
Auditory P300 and eye tracking dysfunction in schizophrenic pedigrees   总被引:4,自引:0,他引:4  
Several psychophysiological abnormalities associated with schizophrenia have been proposed as genetic trait markers of vulnerability to the disorder. Smooth pursuit eye tracking dysfunction and abnormal long latency event-related potentials are the most promising candidates. Both are independent of the effects of psychotropic medication or mental state at the time of testing, and twin studies demonstrate that each has a high level of heritability. Having recorded smooth pursuit eye tracking and event-related potentials in 20 high-density schizophrenic families, we find abnormalities in one or both measures in most of the families studied. The abnormalities, when present, occur in the family members with schizophrenia and other forms of functional psychosis, and they have a bimodal distribution with approximately half the nonschizophrenic relatives also showing eye tracking dysfunction and/or abnormal event-related potentials. Some of these relatives had psychiatric symptoms; others were normal. Our results suggest that psychophysiological examination can help to clarify the boundaries of schizophrenia spectrum disorder. By helping to decide the phenotypic status of nonschizophrenic family members, this should increase the power of DNA linkage studies.  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