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   3556篇
  免费   368篇
  国内免费   7篇
耳鼻咽喉   67篇
儿科学   66篇
妇产科学   60篇
基础医学   511篇
口腔科学   65篇
临床医学   322篇
内科学   908篇
皮肤病学   31篇
神经病学   255篇
特种医学   94篇
外科学   630篇
综合类   66篇
一般理论   2篇
预防医学   353篇
眼科学   121篇
药学   188篇
肿瘤学   192篇
  2021年   46篇
  2020年   40篇
  2019年   33篇
  2018年   60篇
  2017年   51篇
  2016年   38篇
  2015年   68篇
  2014年   74篇
  2013年   128篇
  2012年   172篇
  2011年   189篇
  2010年   114篇
  2009年   101篇
  2008年   158篇
  2007年   168篇
  2006年   184篇
  2005年   177篇
  2004年   147篇
  2003年   127篇
  2002年   139篇
  2001年   68篇
  2000年   62篇
  1999年   47篇
  1998年   47篇
  1997年   37篇
  1996年   39篇
  1995年   36篇
  1994年   33篇
  1993年   30篇
  1992年   42篇
  1991年   55篇
  1990年   45篇
  1989年   54篇
  1988年   55篇
  1987年   48篇
  1986年   32篇
  1985年   48篇
  1984年   55篇
  1983年   36篇
  1982年   44篇
  1981年   43篇
  1980年   38篇
  1979年   45篇
  1978年   47篇
  1977年   50篇
  1976年   39篇
  1975年   34篇
  1974年   42篇
  1973年   36篇
  1969年   28篇
排序方式: 共有3931条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Extensive search of the literature reveals the extreme rarity of true diverticulum of the gallbladder. Its frequency varies from 0.0008% of all resected gallbladders at the Mayo Clinic to 0.06% of a series of congenital anomalies of the gallbladder collected from the world literature. We are presenting a case of a true diverticulum of the gallbladder with sonographic demonstration and focal malignant alterations, neither one of which has been reported previously. The difference between true and false diverticula of the gallbladder is discussed.  相似文献   
6.
Poverty influences health status, life expectancy, health behaviours, and use of health services. This study examined factors influencing the use of health-related services by people living in poverty. In the first phase, 199 impoverished users of health-related services in 2 large Canadian cities were interviewed by their peers. In the second phase, group interviews with people living in poverty (n = 52) were conducted. Data were analyzed using thematic content analysis. Diverse health-related services were used to meet basic and health needs, to maintain human contact, and to cope with life's challenges. Use of services depended on proximity, affordability, convenience, information, and providers' attitudes and behaviours. Use was impeded by inequities based on income status. To promote the health of people living in poverty, nurses and other health professionals can enhance the accessibility and quality of services, improve their interactions with people living in poverty, provide information about available programs, offer coordinated community-based services, collaborate with other sectors, and advocate for more equitable services and policies.  相似文献   
7.
A new endoscopic method of measuring the cross-sectional area of a subglottic stenosis is presented. The method was tested against existing techniques using a model. By standardizing the distance from the objective of the endoscope to the stenotic area we were able to measure the cross-sectional area using a graduated grid held against the video screen. This technique was then compared with the standard one of estimating the diameter of a stenosis from the external diameter of the bronchoscope which can be passed through the stenosis. The methods were found to be equally accurate in measuring the lumen diameter. However, when measuring the minimum cross-sectional area, three of five observers were significantly better (P less than 0.01) using the photometric method rather than the standard method (Wilcoxon's rank sum test for paired data). The photometric technique of measuring the cross-sectional area of the subglottis is easily performed, non-traumatic, and allows a visual record to be kept.  相似文献   
8.
Background. Hypoxia and warm ischemia produce severe injury to cardiac grafts harvested from non-heart-beating donors. To potentially improve recovery of such grafts, we studied the effects of intravenous phenylephrine preconditioning.

Methods. Thirty-seven blood-perfused rabbit hearts were studied. Three groups of non-heart-beating donors underwent intravenous treatment with phenylephrine at 12.5 (n = 8), 25 (n = 7), or 50 μg/kg (n = 7) before initiation of apnea. Non-heart-beating controls (n = 8) received saline vehicle. Hypoxic cardiac arrest occurred after 6 to 12 minutes of apnea, followed by 20 minutes of warm in vivo ischemia. A 45-minute period of ex vivo reperfusion ensued. Nonischemic controls (n = 7) were perfused without antecedent hypoxia or ischemia.

Results. Phenylephrine 25 μg/kg significantly delayed the onset of hypoxic cardiac arrest compared with saline controls (9.6 ± 0.5 versus 7.7 ± 0.4 minutes; p = 0.00001), yet improved recovery of left ventricular developed pressure compared with saline controls (57.1 ± 5.3 versus 41.0 ± 3.4 mm Hg; p = 0.04). Phenylephrine 25 μg/kg also yielded a trend toward less myocardial edema than saline vehicle (p = 0.09).

Conclusions. Functional recovery of nonbeating cardiac grafts is improved by preconditioning. We provide evidence that the myocardium can be preconditioned with phenylephrine against hypoxic cardiac arrest.  相似文献   

9.
We report analyses of data on body fat from a cohort of 34 separated monozygotic twin pairs (MZA) and a matched sample of 38 pairs of monozygotic twins reared together (MZT) originally studied by James Shields. The correlation for MZA pairs was. 61 and the correlation for MZT pairs was. 75. These correlations did not differ significantly, nor did correlations differ between MZA pairs subclassified as having been raised in relatively more or less similar environments. Our results suggest important roles for both genes and environment in the accumulation of body fat and support other adoption studies in suggesting that adult environments rather than rearing environments are the most important nongenetic determinants of levels of body fat in adults.Supported by National Institute of Mental Health Grant MH43409 to R.A.P. and a Grant in Aid from the Dight Institute of Human Genetics to I.I.G.  相似文献   
10.
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