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   2022213篇
  免费   154406篇
  国内免费   24496篇
耳鼻咽喉   24851篇
儿科学   59991篇
妇产科学   52078篇
基础医学   284117篇
口腔科学   55438篇
临床医学   193952篇
内科学   382744篇
皮肤病学   42522篇
神经病学   150671篇
特种医学   75732篇
外国民族医学   442篇
外科学   291975篇
综合类   85113篇
现状与发展   77篇
一般理论   588篇
预防医学   145344篇
眼科学   50123篇
药学   157513篇
  305篇
中国医学   20365篇
肿瘤学   127174篇
  2021年   27132篇
  2020年   18780篇
  2019年   23171篇
  2018年   30239篇
  2017年   24134篇
  2016年   25057篇
  2015年   31633篇
  2014年   41846篇
  2013年   51572篇
  2012年   73013篇
  2011年   78601篇
  2010年   46891篇
  2009年   41733篇
  2008年   66462篇
  2007年   69980篇
  2006年   70747篇
  2005年   68115篇
  2004年   60701篇
  2003年   57334篇
  2002年   54239篇
  2001年   100770篇
  2000年   103478篇
  1999年   87047篇
  1998年   25406篇
  1997年   22766篇
  1996年   21583篇
  1995年   20729篇
  1994年   18621篇
  1993年   16484篇
  1992年   61823篇
  1991年   59439篇
  1990年   56785篇
  1989年   54339篇
  1988年   49448篇
  1987年   47960篇
  1986年   44921篇
  1985年   42569篇
  1984年   31059篇
  1983年   26346篇
  1982年   14691篇
  1979年   27048篇
  1978年   18487篇
  1977年   15656篇
  1976年   14603篇
  1975年   15508篇
  1974年   18737篇
  1973年   18051篇
  1972年   16765篇
  1971年   15485篇
  1970年   14346篇
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
991.
The relationship between energy expenditure and body composition, in terms of fat and fat-free masses, has previously been described by a variety of predictive regression equations with parameters devoid of physiological content. We present here results obtained by calculating the specific energy expenditure, ie, the energy expenditure per unit of mass, of fat and fat-free tissue on the basis of measurements of the total energy expenditure (EE), the masses of fat (FM), and fat-free (FFM) tissue using the following simple model: EE = k1.FM + k2.FFM where k1 and k2 are the specific energy expenditures of fat and fat-free tissue, respectively. The results of observations on 104 women at rest yielded values for k1 and k2 of 0.31 and 1.35 watts/kg of fat and fat-free mass, respectively, with standard errors of estimate of 0.074 and 0.052 watts/kg, respectively. Analysis of several series of measurements, from other sources and on smaller samples of subjects, yielded similar values at rest but with larger standard errors of estimate. Data from subjects performing varying amounts of work in 24-h measurements showed, as expected, larger values for both tissues. The results explain to a very large extent the well-established relation between resting metabolic rate and body weight, ie, a linear relation with a non-zero intercept. The results also offer a clear-cut explanation for the well known difference in energy expenditure between men and women with the same body weight.  相似文献   
992.
Proteins in normal human urine were clearly fractionated into 26 bands with molecular weights from 14,000 to 230,000 by means of one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) coupled with silver staining. The main band contained uromucoid, and the second main band had albumin. However, when urine samples from healthy persons were electrophoresed in the absence of SDS using polyacrylamide gel or agarose gel, or a cellulose acetate membrane, albumin but not uromucoid, frequently formed the main protein band. It is suggested that this is due to the complexing of uromucoid subunits to form a large molecule which cannot penetrate into the gel. In order to correctly fractionate all the proteins contained in normal human urine, it was concluded that it was best to treat a urine sample with SDS with pre-condensation, fractionate it by SDS-PAGE and stain fractionated proteins by a highly sensitive method such as silver staining.  相似文献   
993.
The story of Joe     
  相似文献   
994.
Introduction   QT interval prolongation may cause the potentially lethal tachyarrhythmia torsades de pointes ( 1 ). The cause of the QT interval prolongation may be a congenital mutation in genes encoding cardiac potassium and sodium channels ( 2 ) or be acquired following drug administration ( 3 ) or metabolic disorders ( 4 ). Among a few other drugs volatile anaesthetics prolong the QT interval. During the last few years sevoflurane has become the most used volatile anaesthetic for the induction of anaesthesia in infants.
Methods   This investigation, on infants aged from 1 to 6 months, was approved by the institutional ethic committee. Thirty-six otherwise healthy infants due to elective surgery were included in our study The patients were randomly assigned to one of two treatment groups. Group S ( n  = 24) was anaesthetised with sevoflurane, Group H was anaesthetised with halothane. ECG recordings were taken before the anaesthesia onset, 15 min after the first contact with the volatile anaesthetic and 60 min after the ending of the volatile gas exposition. QTc interval was calculated using the Bazett's formula ( 5 ).
Results   QTc interval was significantly ( P < 0.0002) (Table 1) lengthened 15 min after anaesthesia induction with sevoflurane as well as 60 min ( P < 0.01) after the ending of the gas exposition without any difference in age and gender. The QTc interval in patients anaesthetised with halothane did not show any significant change.  

  Table 1  相似文献   

995.
目的:明确胚胎NA能神经元移植对点燃癫痫发作严重程度的影响。方法:以Wistar大鼠为研究对象,按移植物的性质分为NA移植组、移植对照组和还对照组。首先定期电刺激杏仁核制备电点燃癫痫模型,再用立体定向技术向各组动物的海马移植相应的移植物,移植后观察癫痫的电生理和行为学指标(杏仁核后放电阈值、持续时间、癫痫行为级别、癫痫持续时间)变化情况,TH免疫组织化学染色了解移植物存活情况。结果:经统计学处理,移植前后各指标无显著性差异(P>0.05)。结论:胚胎NA能神经元移植对点燃癫痫的发作严重程度无抑制作用。  相似文献   
996.
This study examined the immunoregulatory role of recombinant interleukin 4 (IL-4), also known as B-cell stimulating factor 1, on the generation of cytotoxic effector cells from normal and leukaemic human blood mononuclear cells. When tested on cells from normal individuals, the addition of IL-4 to mixed lymphocyte cultures led to a dose-dependent proliferation of T-helper cells (CD3, 4 positive) with a concomitant decrease in phenotypic and functional cytotoxic T cells and natural killer (NK) cells. IL-4 also inhibited the interleukin-2 (IL-2)-induced generation of lymphokine-activated killer (LAK) activity when added at the beginning of mixed lymphocyte culture. When tested on mature leukaemic NK cells, IL-4 also inhibited the ability of IL-2 to induce LAK function using a short-term culture system. These results show that IL-4 acts on both normal and leukaemic cells and suggests that it acts at more than one level during the development of LAK function.  相似文献   
997.
目的 :探讨计算机专业人员的心理健康状况。方法 :以SCL 90为工具 ,对 71名计算机专业人员进行评估。结果 :计算机专业人员SCL 90总分和各因子显著低于全国常模 ;男性员工在躯体化、强迫、人际关系、焦虑、敌对、饮食和睡眠因子上得分显著高于女性员工 ;女性在恐怖因子得分显著高于男性。结论 :计算机专业人员心理症状较少 ,症状严重程度较低 ,男性员工自我感觉与自我评价方面低于女性员工。  相似文献   
998.
OBJECTIVE: evaluation and comparison of the endovascular treatment of isolated aortic and aortoiliac atherosclerotic lesions (stenoses and occlusions). METHODS: a percutaneous endovascular procedure was performed in 52 patients (38 men and 14 women) with a mean age of 52 years (range, 25-85 years). The baseline angiogram showed 35 aortic lesions (31 stenoses, 4 occlusions) and 17 aortoiliac lesions (14 stenoses, 3 occlusions). Percutaneous techniques used in this series included variable combinations of transluminal angioplasty and stenting. All stents placements were performed over-the-wire using the transfemoral route (most often bilateral approach). Clinical examination and Duplex-scan were performed at discharge, 1 month, 6 months, 12 months, and then yearly. RESULTS: technical success was 100% for aortic and aortoiliac lesions. Angiographic success rates were comparable for aortic (91%) and aortoiliac (94%) lesions. No death occurred during or early after the endovascular intervention. Duplex-scan confirmed 100% patency rate at discharge. There was no significant difference between the aortic (94%) and aortoiliac (96%) groups regarding immediate clinical improvement. Mean follow-up was 34+/-31 months (range, 0-130 months). The cumulative primary patency rate at 36 months was 85% in the aortic group and 86% in the aortoiliac group. Clinical success, defined as a symptom-free status at the end of follow-up, was also similar in both groups. CONCLUSION: endovascular treatment of isolated aortic lesions of the infra-renal aorta has favorable outcomes comparable to those of aortoiliac lesions.  相似文献   
999.
BACKGROUND: Biliary tract lesions pose a dreaded complication of laparoscopic cholecystectomy. In a retrospective study we analyzed the clinical presentation, diagnostic and therapeutic management and outcome of 28 patients presenting with iatrogenic bile duct injuries. PATIENTS AND METHODS: Between 1994 and 2001 we treated 28 patients with bile duct lesions following laparoscopic cholecystectomy at our center. Operation notes and charts of all patients were reviewed systematically. A follow-up examination of each patient was performed after a median of 12 months (range 1-90). RESULTS: Twenty-two patients presented with major circumferential bile duct defect lesions. Less severe injuries (n=6) were two minor bile leaks, one bile duct stricture and three tangential lesions. Twenty-six patients were referred to our institution within 16 days (range 0-226 days). Six patients were treated by nonsurgical procedures: endoscopic stenting in four and percutaneous intervention in two. In one of the remaining patients a cystic duct leak was closed via laparotomy, and in 21 a hepaticojejunostomy was performed. Reconstruction of a hepaticojenunostomy was performed in two of these patients. Patients were dismissed from the hospital after a median of 13 days (range 4-156). Four patients presenting with generalized biliary peritonitis required prolonged intensive care. One or more episodes of cholangitis were seen in five patients during follow-up examinations. CONCLUSIONS: Major iatrogenic bile duct injuries are associated with high morbidity and prolonged hospitalization. Interdisciplinary cooperation and early referral to an experienced center is crucial in the management of patients suffering from this affliction. Cholangitis is a marked problem in the follow-up.  相似文献   
1000.
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