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   18398篇
  免费   976篇
  国内免费   278篇
耳鼻咽喉   139篇
儿科学   1120篇
妇产科学   468篇
基础医学   1980篇
口腔科学   320篇
临床医学   1781篇
内科学   2880篇
皮肤病学   369篇
神经病学   1276篇
特种医学   636篇
外科学   1857篇
综合类   1462篇
一般理论   1篇
预防医学   3131篇
眼科学   112篇
药学   1107篇
  4篇
中国医学   408篇
肿瘤学   601篇
  2023年   383篇
  2022年   683篇
  2021年   962篇
  2020年   865篇
  2019年   894篇
  2018年   846篇
  2017年   602篇
  2016年   518篇
  2015年   555篇
  2014年   1224篇
  2013年   1218篇
  2012年   859篇
  2011年   1080篇
  2010年   879篇
  2009年   933篇
  2008年   900篇
  2007年   853篇
  2006年   691篇
  2005年   596篇
  2004年   431篇
  2003年   371篇
  2002年   270篇
  2001年   234篇
  2000年   214篇
  1999年   178篇
  1998年   153篇
  1997年   134篇
  1996年   121篇
  1995年   94篇
  1994年   105篇
  1993年   84篇
  1992年   78篇
  1991年   68篇
  1990年   68篇
  1989年   51篇
  1988年   50篇
  1987年   59篇
  1985年   98篇
  1984年   76篇
  1983年   61篇
  1982年   61篇
  1981年   75篇
  1980年   104篇
  1979年   92篇
  1978年   103篇
  1977年   74篇
  1976年   157篇
  1975年   129篇
  1974年   100篇
  1973年   108篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
61.
咽旁间隙原发性肿块流行病学分析   总被引:1,自引:0,他引:1  
目的:对咽旁间隙原发性肿块进行流行病学分析。方法:对咽旁间隙原发性239例肿块进行统计分析。结果:原发良性肿瘤患病比为61.09%,其中上皮源性肿瘤患病比最高,占19.25%;神经源性肿瘤第二位,占17.57%。原发性恶性肿瘤的患病比为35.15%,其中上皮源性恶性肿瘤的患病比最高,占21.76%;恶性淋巴瘤第2位,占7.95%。炎症的患病比为3.77%,其中淋巴结反应性增生最高。结论:咽旁间隙原发性肿块良性肿瘤的患病比最高,恶性肿瘤次之,炎症居第3位,比例约为17:9:1。  相似文献   
62.
不同营养支持方式对肠外瘘患者人体组成改善作用之比较   总被引:1,自引:1,他引:0  
目的观察不同营养支持方式对肠外瘘患者人体组成的改善作用。方法30例肠外瘘患者分成两组各15例,分别给予全肠外营养支持(TPN)或全肠内营养支持(TEN),观察10d前后患者人体组成及血清胰岛素样生长因子-1(IGF-1)的变化。结果10d后所有患者的体重指数(BMI)与体细胞群(BCM)显著改善,而TEN组患者10d前后BCM增加幅度更明显,分别为(27.5±0.8)kg和(29.0±0.6)kg,Day10与Day0相比,P<0.01。两组患者总体水(TBW)与细胞内水(ICW)均增加,尤其ICW,Day10与Day0相比,TEN组P<0.01;TPN组P<0.05。血清IGF-1在两组患者治疗后均有显著上升,TEN组增加幅度更明显,Day0为(175.0±32.9)ng/ml,Day10为(255.5±34.1)ng/ml,与Day0比较,P<0.01;与TPN组比较,P<0.05。IGF-1的变化与BCM的改善显著正相关(r2=0.16,P<0.05)。结论营养支持治疗能显著改善肠外瘘患者的体细胞群,纠正细胞内、外水的异常分布,而EN作用更明显。  相似文献   
63.
Physical inactivity, excess adiposity and premature mortality   总被引:5,自引:0,他引:5  
The purpose of this report is to review the evidence that physical inactivity and excess adiposity are related to an increased risk of all‐cause mortality, and to better identify the independent contributions of each to all‐cause mortality rates. A variance‐based method of meta‐analysis was used to summarize the relationships from available studies. The summary relative risk of all‐cause mortality for physical activity from the 55 analyses (31 studies) that included an index of adiposity as a covariate was 0.80 [95% confidence interval (CI) 0.78–0.82], whereas it was 0.82 [95% CI 0.80–0.84] for the 44 analyses (26 studies) that did not include an index of adiposity. Thus, physically active individuals have a lower risk of mortality by comparison to physically inactive peers, independent of level of adiposity. The summary relative risk of all‐cause mortality for an elevated body mass index (BMI) from the 25 analyses (13 studies) that included physical activity as a covariate was 1.23 [95% CI 1.18–1.29], and it was 1.24 [95% CI 1.21–1.28] for the 81 analyses (36 studies) that did not include physical activity as a covariate. Studies that used a measure of adiposity other than the BMI show similar relationships with mortality, and stratified analyses indicate that both physical inactivity and adiposity are important determinants of mortality risk.  相似文献   
64.
目的:评价持续靶控输注异丙酚复合硬膜外阻滞有用于上腹部手术的可行性。方法:30例胃癌手术患者,ASAⅠ~Ⅱ级。随机分成靶控输注异丙酚全麻(T)组15例,靶控异丙酚复合硬膜外阻滞(T+E)组15例。结果:(T+E)组术后躁动、芬太尼、丙泊酚的用量低于(T)组(P<0.05)。异丙酚单位标准化剂量亦较低。两组苏醒时间相似。诱导后两组血压均显著下降(P<0.05),T+E组在诱导后DBP的下降幅度较T组更为显著(P<0.05),T组在探查、术毕、拨管后的SBP、DBP、MAP比(T+E)组显著增高(P<0.05)。两组诱导后至术毕BIS、SEF显著下降,两组间的比较无统计学意义(P>0.05)。结论:靶控输注异丙酚复合硬膜外阻滞用于上腹部手术是可行的,具有异丙酚、芬太尼的用量少、苏醒快、术后躁动少,麻醉深度易于调控,血液动力学较稳定,是一种良好的麻醉方式。  相似文献   
65.
 Oral self-administration and operant tasks have been used successfully to confirm ethanol′s positive reinforcing effects in rats. However, in flavor conditioning tasks, ethanol is typically found to have aversive effects. The present studies explored this apparent paradox by examining the change in value of a flavor paired with orally self-administered ethanol in two different limited-access procedures. Rats were food-deprived and trained to drink (experiment 1) or to barpress for (experiment 2) 10% (v/v) ethanol during daily 30-min sessions using prandial initiation techniques. All rats were then exposed to a differential flavor conditioning procedure in which banana or almond extract was added to the drinking solution. One flavor (counterbalanced) was always mixed with ethanol (CS+), whereas the other flavor was mixed with water (CS–). By the end of conditioning, rats in both experiments drank more flavored ethanol than flavored water, confirming ethanol’s efficacy as a reinforcer. Moreover, barpress rates for CS+ exceeded those for CS– in the operant task. Ethanol doses self-administered in final sessions averaged about 1 g/kg. The effect of the flavor-ethanol contingency was assessed in preference tests that offered a choice between the two flavor solutions without ethanol. In both experiments, subjects developed a preference for the flavor that had been paired with ethanol. Thus, the outcome of flavor conditioning was consistent with that of the oral self-administration tasks in providing evidence of ethanol’s rewarding effects. These experiments confirm and extend previous studies showing that flavor aversion is not the inevitable result of flavor-ethanol association in rats. It seems likely that ethanol’s nutrient and pharmacological effects both contributed to the development of conditioned flavor preference. Received: 15 February 1997 / Final version: 11 June 1997  相似文献   
66.
Nodular regenerative hyperplasia (NRH), a rare condition that is commonly associated with noncirrhotic portal hypertension, is not well described in the MR literature. Three patients at two institutions were identified who had both abdominal MR imaging and pathologic evidence of NRH. All examinations were performed at 1.5 T and included axial T1- and T2-weighted spin-echo (SE) images. The MR studies were reviewed by two radiologists in consensus. Two patients had multiple liver lesions that had high signal components on T1-weighted images and were predominantly isointense with liver on the T2-weighted images. One patient had no focal lesions identified. NRH, when visualized on MR images, appears as multifocal masses with shortened Tl and T2 similar to liver. NRH should be considered in the differential diagnosis of hepatocellular tumors, especially in patients with a predisposing condition.  相似文献   
67.
68.
The chronic exposure of rats to a schedule of operant water reinforcement coupled with chronically restricted access to water sensitized the animals to intermittentd-amphetamine injections (0.31–2.5 mg/kg with intervals of 12–23 days between any two injections) in such a way that this drug came to produce catastrophic losses of body weight (32.4% of control levels). In the sessions whend-amphetamine was administered, the rats were also given a total of 12 brief electric shocks. Loss of body weight was unaccompanied by parallel changes in operant behavior performance, or in food or water intake. Remarkably, in other studies with the same interventions (sham schedule sessions, water deprivation, and foot shocks), with the exception that reinforcers were never delivered,d-amphetamine did not produce catastrophic falls in body weight. This super-reactivity tod-amphetamine toxicity may be mediated by a possible stressor action of the schedule of reinforcement. Its mechanism might be analogous to the known sensitization produced by classical experimental stressor stimuli to the repeated administration ofd-amphetamine.  相似文献   
69.
西文介绍了综合效益评价中指标的逐步筛选及其假设检验方法,用该法选出的指标具有独立性强、代表性好的优点。同是分析处理了全国34家县级医院的投入指标,从中筛选出5个指标参与评价。  相似文献   
70.
Body composition measured with isotopic dilution was compared with anthropometric measurements. The study was carried out in 47 subjects from both sexes, 65 to 92 years old. Total body water (TBW), anthropometric measurements, and dynamometry were assessed. TBW was significatively higher in men than women and decreased with age. Dynamometry and fatfree mass were well correlated (r=0.73 in males and r=0.58 in females) and significantly different between sexes. A negative correlation was found for dynamometry with age, being significant for women. Linear regression equations to predict TBW from anthropometric measurements in males and females were obtained: Males: TBW(I)=19.349+0.617 weight(kg) — 0.931 mid-arm circumference(cm)+0.122 dynamometry (kg) Females: TBW(l)=−5.531+0.343 weight(kg)-0.213 triceps skinfold (mm)+ 0.148 dynamometry(kg) + 3.424 wrist diameter (cm). This simple model is proposed for use in epidemiological and field studies where other more sophisticated methods can not be applied.  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