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   1277257篇
  免费   99930篇
  国内免费   1987篇
耳鼻咽喉   18442篇
儿科学   44372篇
妇产科学   35032篇
基础医学   182271篇
口腔科学   33611篇
临床医学   111236篇
内科学   258126篇
皮肤病学   28018篇
神经病学   100513篇
特种医学   51439篇
外国民族医学   660篇
外科学   196549篇
综合类   27054篇
现状与发展   1篇
一般理论   377篇
预防医学   95704篇
眼科学   27964篇
药学   94786篇
  2篇
中国医学   2423篇
肿瘤学   70594篇
  2018年   13145篇
  2017年   9978篇
  2016年   10912篇
  2015年   12393篇
  2014年   17194篇
  2013年   26243篇
  2012年   36070篇
  2011年   38127篇
  2010年   22850篇
  2009年   21849篇
  2008年   36708篇
  2007年   39310篇
  2006年   39571篇
  2005年   38497篇
  2004年   37649篇
  2003年   36496篇
  2002年   35842篇
  2001年   64034篇
  2000年   66545篇
  1999年   56440篇
  1998年   15152篇
  1997年   13771篇
  1996年   14212篇
  1995年   13477篇
  1994年   12779篇
  1993年   11814篇
  1992年   44587篇
  1991年   43494篇
  1990年   42235篇
  1989年   40126篇
  1988年   36911篇
  1987年   36250篇
  1986年   33633篇
  1985年   32297篇
  1984年   24149篇
  1983年   20273篇
  1982年   11730篇
  1981年   10701篇
  1980年   9523篇
  1979年   21351篇
  1978年   14824篇
  1977年   12542篇
  1976年   11698篇
  1975年   12626篇
  1974年   14669篇
  1973年   14125篇
  1972年   12952篇
  1971年   11740篇
  1970年   11061篇
  1969年   10030篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Aim:   In the last three decades, the segment of population aged 60 years and older has more than doubled in Brazil. People aged 80 years and older are expected to be the fastest-growing segment in the near future. This aim of this study was to analyze the legal structures currently in place in Brazil and to provide a framework for care policies and practices towards older-adults.
Methods:   This article focuses on past and present major socioeconomic burdens on this segment of the Brazilian population as well as on public achievements to overcome inequities.
Results:   Both the public health and the social security systems have been directed to provide preferential assistance to the aged. Nonetheless, the elderly remain the most impoverished segment of Brazil and carry the burden of an overall lack of specialized services. Moreover, socioeconomic inequalities and population diversity in Brazil affects elderly care, adding complexity to this unique scenario.
Conclusion:   Brazil has adopted legal hallmarks that substantially shifted public practices towards the elderly segment from a philanthropic status to a legitimate right for care and assistance. The demographic transition that took place provides an opportunity for innovative solutions in public policies for older adults in a developing economic environment.  相似文献   
992.
993.
994.
995.
996.
We provide further evidence for the two-factor structure of the 9-item Academic Expectations Stress Inventory (AESI) using confirmatory factor analysis on a sample of 289 Canadian adolescents and 310 Singaporean adolescents. Examination of measurement invariance tests the assumption that the model underlying a set of scores is directly comparable across groups. This study also examined the cross-cultural validity of the AESI using multigroup confirmatory factor analysis across both the Canadian and Singaporean adolescent samples. The results suggested cross-cultural invariance of form, factor loadings, and factor variances and covariances of the AESI across both samples. Evidence of AESI's convergent and discriminant validity was also reported. Findings from t-tests revealed that Singaporean adolescents reported a significantly higher level of academic stress arising from self expectations, other expectations, and overall academic stress, compared to Canadian adolescents. Also, a larger cross-cultural effect was associated with academic stress arising from other expectations compared with academic stress arising from self expectations.  相似文献   
997.
998.
Background: In elderly patients, opioids may cause prominent postoperative sedation and respiratory depression. We evaluated the influence of age on the effects of opioids and plasma concentrations of fentanyl and oxycodone in cardiac surgery patients.
Methods: Thirty (≥75 years, gender M9/F21) and 20 (≤60 years, gender M20/F0) patients scheduled to undergo cardiac surgery. A standard anesthesia with fentanyl as an opioid was used. Fentanyl plasma concentrations were measured at the end of surgery and 2 h later. After tracheal extubation, when the pain intensity was at least moderate, blood samples for fentanyl and oxycodone plasma concentration measurements were taken. Thereafter, oxycodone hydrochloride 0.05 mg/kg i.v. was administered. After 15 and 45 min, pain intensity, sedation and oxycodone plasma concentration were determined. This test protocol was repeated twice.
Results: The elderly had a higher plasma concentration of fentanyl at the end of surgery than younger patients (5.7±2.2 vs. 3.8±1.2 ng/ml, P =0.001). The plasma concentrations of oxycodone were comparable between the groups. The interval between the second and the third oxycodone dose was longer in the elderly patients ( P =0.036). Pain intensity on the verbal rating scale was lower at the 45-min assessment point after all three oxycodone test doses ( P =0.008) and sedation scores were significantly higher after the third dose in the elderly patients ( P =0.035).
Conclusions: In elderly patients, the plasma concentration of fentanyl was higher but plasma levels of oxycodone were at a similar level compared with middle-aged patients. However, the elderly patients had less pain and were more sedated after doses of oxycodone.  相似文献   
999.
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