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   2339495篇
  免费   182848篇
  国内免费   7302篇
耳鼻咽喉   30237篇
儿科学   76298篇
妇产科学   64592篇
基础医学   333935篇
口腔科学   64983篇
临床医学   215793篇
内科学   466683篇
皮肤病学   53701篇
神经病学   190966篇
特种医学   91275篇
外国民族医学   522篇
外科学   348777篇
综合类   52600篇
现状与发展   5篇
一般理论   930篇
预防医学   192301篇
眼科学   51474篇
药学   167748篇
  8篇
中国医学   3909篇
肿瘤学   122908篇
  2018年   24010篇
  2016年   21665篇
  2015年   24478篇
  2014年   34089篇
  2013年   51780篇
  2012年   66272篇
  2011年   71142篇
  2010年   43011篇
  2009年   41714篇
  2008年   67005篇
  2007年   71612篇
  2006年   72155篇
  2005年   70243篇
  2004年   67206篇
  2003年   64993篇
  2002年   62454篇
  2001年   106406篇
  2000年   109032篇
  1999年   91701篇
  1998年   27252篇
  1997年   24561篇
  1996年   25563篇
  1995年   25152篇
  1994年   23393篇
  1993年   21992篇
  1992年   75226篇
  1991年   73585篇
  1990年   71190篇
  1989年   68253篇
  1988年   63317篇
  1987年   62291篇
  1986年   58918篇
  1985年   56571篇
  1984年   43061篇
  1983年   36992篇
  1982年   22745篇
  1981年   20570篇
  1980年   19374篇
  1979年   40061篇
  1978年   29269篇
  1977年   24652篇
  1976年   22667篇
  1975年   24151篇
  1974年   28900篇
  1973年   28053篇
  1972年   26154篇
  1971年   24301篇
  1970年   22570篇
  1969年   21249篇
  1968年   19856篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
The activity of LCAT (the controlling enzyme for cholesterol esterification in plasma) is known to be reduced in alcoholic cirrhosis, while little is known about early stage (liver steatosis) alcoholics. In this study, LCAT activity was assayed by Stokke and Norum's method, before and after a 15-day sobriety period, in liver steatosis and in cirrhosis alcoholics. Before alcohol withdrawal, LCAT activity was depressed in both groups. After the sobriety period, LCAT activity was significantly raised in liver steatosis patients, but was still lower than in controls; in cirrhosis patients, it was increased, but not significantly. According to our results, LCAT activity impairment in alcoholic liver disease is sustained by both the hypothesized mechanisms, alcohol-related metabolic disorders and lowered LCAT-enzyme production, but to different degrees, depending on the stage of the disease. In liver steatosis, metabolic disorders play a major role, as a liver-impairment-induced decrease in LCAT production seems rather unlikely, and increased LCAT activity is more likely to be sustained by metabolic normalisation than by any recovery of the damaged liver. However, the lack of improvement in about 20% of patients, and the fairly wide scattering of individual data, suggest a minor LCAT production impairment in liver steatosis too. In cirrhosis, the major role seems to be played by a permanent decrease in LCAT production, as no significant rise in LCAT activity was observed after alcohol withdrawal. However the restored LCAT activity observed in some patients could be related to improvement in the metabolic disorder, thus confirming the effectiveness of this mechnism in cirrhosis too.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
992.
Fine Needle Aspiration Cytology (F.N.A.C.) has been used as a diagnostic tool by the ENT departments in Tayside since the end of 1985. This paper discusses the results of our initial experience with this and outlines some of the diagnostic pitfalls. This is a useful and accurate procedure with many advantages over diagnostic biopsy.  相似文献   
993.
Although we are on steep learning curve as far as the exact relationship between nutrition and disease prevention is concerned, evidence is accumulating on the role of body mass index and mortality, protein deficiency and decreased ability to fight infection, effect of fiber intake on cholesterol and glucose metabolism, hyperlipidemia and atherosclerosis, and inadequate calcium intake in osteoporosis. Screening for nutritional disorders includes identifying those with risk factors of being female, black, poor, or institutionalized. Evidence of weight change, dietary idiosyncracies, nutrient deficiency, and laboratory tests can be helpful. Treatment should be tailored to the individual and be specific for suspected deficiencies. Attention to calories, protein, and calcium are paramount.  相似文献   
994.
995.
CT evaluation of Crohn's disease: effect on patient management   总被引:8,自引:0,他引:8  
CT scans from 80 consecutive patients with clinically symptomatic Crohn's disease were reviewed retrospectively to determine the effect of CT diagnosis on patient management. The initial clinical impression and any subsequent change in patient management because of the CT findings were noted. In 22 (28%) of the 80 patients, significant previously unsuspected findings led to a change in medical or surgical management. These included 12 patients with fistulae, four with abscess, two with avascular necrosis of the femoral head, two with sacral osteomyelitis, and single cases of pelvic inflammatory disease and femoral vein thrombosis.  相似文献   
996.
997.
Summary Bone loss and fracture type were determined in 358 tibial condylar fractures. Degree of osteoporosis at the knee was defined by analogy to Singh's grades of osteoporosis at the hip and to Jhamaria's classification of osteoporosis at the calcaneum: grade V — normal; grade IV — slight reduction of trabecular bone; grade III — osteoporosis, predominantly of trabecular bone; grade II — osteoporosis of trabecular and cortical bone. Five fracture types were distinguished, with the component of trabecular bone compression increasing from a to e: a — pure split fractures; b — split fractures with displacement of a piece of the articular surface; c — split compression fractures; d — local compression fractures; e — compression of a whole condyle. There was a highly significant rank correlation between the two sets of ordered categories. Fractures in osteoporotics tended to involve the lateral condyle; this is explained by the fact that crush fractures occurred more frequently at the lateral condyle. The influence of bone loss on fracture type was demonstrated to be independent of age. A clear understanding of these associations concerning three variables at a time was reached by the use of log-linear-model analysis for cross-classified qualitative data.
Zusammenfassung Bei 358 Frakturen der proximalen Tibia wurden der röntgenologisch erkennbare Knochenschwund und die Frakturform festgestellt. Entsprechend dem Singh-Index zur Bestimmung der Osteoporose am proximalen Femur und der Klassifikation der Trabekelstruktur am Fersenbein nach Jhamaria wurden folgende Osteoporosegrade am Knie definiert: Grad V — normal, Grad IV — Spongiosastruktur leicht vermindert, Grad III — Osteoporose betrifft vorwiegend die Spongiosa, Grad II —Osteoporose von Spongiosa und Kompakta. Fünf Frakturformen wurden unterschieden, wobei das Ausmaß der Spongiosakompression von a bis e ansteigt: a — reine Spaltfrakturen, b — Spaltfrakturen mit Abscherung eines Gelenkflächenteiles, c —Spaltkompressionsfrakturen, d — Frakturen mit lokaler Kompression, e — Frakturen mit Kompression eines ganzen Kondyls. Zwischen diesen beiden Merkmalen, deren Ausprägungen Rangklassen bilden, war eine hochsignifikante Rangkorrelation nachzuweisen. Brüche osteoporotischer Knochen betrafen vermehrt den lateralen Gelenksknorren, was dadurch statistisch zu erklären war, daß dieser sich für Kompressionsfrakturen als anfälliger erwies. Die Beziehung zwischen Osteoporose und Frakturform war nicht abhängig vom Lebensalter. Solche Zusammenhange zwischen je drei Variablen konnten übersichtlich dargestellt wurden, indem die Häufigkeitstabellen durch Log-lineare Modelle interpretiert wurden.
  相似文献   
998.
A cross-sectional study of tobacco-smoking habits in a random sample of 976 coloured subjects aged 15-64 years revealed that smoking was common, 57% of men and 41% of women being current smokers and 10.4% of men and 9.6% of women having stopped smoking. Heavy smoking prevailed, indicating by mean daily consumption of 14.2 and 13.1 cigarettes among male and female smokers respectively; only 33.5% of male and 39.6% of female smokers used less than 10 cigarettes per day. Coloured smokers smoked more heavily during the weekend. Both men and women smoked mostly filter cigarettes. Forty-four per cent of male and 49.5% of female smokers stated that they had attempted to stop smoking, mainly for health reasons. More than one-third of the participants had a positive attitude to combating smoking, particularly those with an educational level higher than Standard 7. Former smokers and heavy smokers had a significantly higher prevalence of ischaemic heart disease than the other participants. Smoking was associated with a low body mass index, low high-density lipoprotein cholesterol levels, low socio-economic standing, high alcohol consumption and type A coronary-prone behaviour in men. In 1982 the economically active coloured population of the Cape Peninsula spent an estimated R36.2 million on cigarettes.  相似文献   
999.
Lung cancer is the leading cause of cancer deaths in both men and women in the United States. Treatment depends on the type and stage of lung cancer. For stage I and II cancer, surgery is usually the treatment of choice. Radiation therapy is used in patients who are considered poor risks for surgical resection. Intraoperative brachytherapy is an effective alternative to external irradiation in this group of patients. From 1958 to 1984, 55 patients with non-small-cell lung cancer were explored at Memorial Sloan Kettering Cancer Center and found to have surgical stage I or II tumors, which were considered to be unresectable mainly because of severe obstructive pulmonary disease precluding adequate resection. All these patients were treated with intraoperative brachytherapy at the time of the thoracotomy. Forty-four percent of these patients received in addition external irradiation, mainly to the mediastinum. The overall 5-year survival calculated by the Kaplan-Meier Method was 32%, and the local disease-free survival was 63%. Cox regression multivariant analysis demonstrated that there is a distinct subgroup with a better prognosis based on tumor site and patient's age--ie, patients who were younger than 58 years of age and had right-side lesions.  相似文献   
1000.
Specific pathogen-free rats were exposed to the cigarette smoke (CS) of 25 cigarettes daily for 14 days and concurrently given N-acetylcysteine (Nac) as 1% of their drinking water (average daily dose 973 mg/kg). The thickness of the epithelium was measured at four airway levels and the numbers of mucus-containing secretory cells, stained for neutral or acidic glycoprotein (NGP or AGP respectively), were counted in surface epithelium at eight airway levels. Cigarette smoke increased the thickness of the epithelium at three of the airway levels studied by between 37 and 72%. The number of secretory cells was increased at all airway levels distal to the upper trachea by between 102 and 421%. Secretory cells containing NGP were reduced in number but this was more than offset by a large increase in the number of secretory cells containing AGP at all airway levels. N-acetylcysteine inhibited CS-induced epithelial thickening. Nac also inhibited the CS-induced increase in the number of secretory cells with AGP, but had little effect on the CS-induced reduction in the number of cells with NGP. Thus, prophylactic oral N-acetylcysteine led to an overall inhibition of CS-induced mucous cell hyperplasia and epithelial hypertrophy. The results suggest a novel anti-inflammatory action for a drug with known mucolytic effects.  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