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   29616篇
  免费   2465篇
  国内免费   71篇
耳鼻咽喉   302篇
儿科学   880篇
妇产科学   463篇
基础医学   3939篇
口腔科学   555篇
临床医学   3146篇
内科学   6102篇
皮肤病学   348篇
神经病学   2724篇
特种医学   989篇
外国民族医学   3篇
外科学   3990篇
综合类   560篇
现状与发展   1篇
一般理论   19篇
预防医学   2913篇
眼科学   921篇
药学   2128篇
中国医学   32篇
肿瘤学   2137篇
  2021年   457篇
  2020年   318篇
  2019年   511篇
  2018年   538篇
  2017年   380篇
  2016年   438篇
  2015年   533篇
  2014年   765篇
  2013年   1200篇
  2012年   1757篇
  2011年   1854篇
  2010年   942篇
  2009年   985篇
  2008年   1657篇
  2007年   1826篇
  2006年   1738篇
  2005年   1761篇
  2004年   1690篇
  2003年   1524篇
  2002年   1490篇
  2001年   532篇
  2000年   542篇
  1999年   572篇
  1998年   406篇
  1997年   311篇
  1996年   321篇
  1995年   278篇
  1994年   242篇
  1993年   217篇
  1992年   364篇
  1991年   350篇
  1990年   361篇
  1989年   349篇
  1988年   309篇
  1987年   299篇
  1986年   329篇
  1985年   275篇
  1984年   266篇
  1983年   212篇
  1982年   229篇
  1981年   211篇
  1980年   193篇
  1979年   245篇
  1978年   184篇
  1977年   165篇
  1976年   151篇
  1975年   133篇
  1974年   138篇
  1973年   153篇
  1972年   111篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
7.

Introduction/Hypothesis

Recruitment of participants into phase 1 vaccine clinical trials can be challenging since these vaccines have not been used in humans and there is no perceived benefit to the participant. Occasionally, as was the case with a phase 1 clinical trial of an Ebola vaccine in Halifax, Canada, during the 2014–2016 West African Ebola virus outbreak, recruitment is less difficult. In this study, we explored the motivations of participants in two phase 1 vaccine trials that were concurrently enrolling at the same centre and compared the motivations of participants in a high-profile phase 1 Ebola vaccine trial to those in a less high-profile phase 1 adjuvanted seasonal influenza vaccine study.

Methods

An online survey which included participants’ prior experience with clinical trials, motivations to participate (including financial incentives), and demographic information was developed to examine the motivations of healthy participants in two phase 1 clinical vaccine trials conducted at the Canadian Center for Vaccinology in Halifax, Nova Scotia. Participants were invited via email to complete the online survey. Readability and clarity were assessed through pilot testing.

Results

A total of 49 (55.7%) of 88 participants of the two studies completed the survey (22 [55%] of 40 participants from the Ebola vaccine study and 27 [56.3%] of 48 from the adjuvanted influenza vaccine study). Motivations that were most frequently ranked among participants' top three in both trials were (1) wanting to contribute to the health of others, (2) wanting to participate in something important, (3) wanting to contribute to the advancement of science, and (4) wanting to receive an incentive such as money or a tablet.

Conclusions/Recommendations

Although media attention and financial compensation were more often cited by Ebola vaccine trial participants as a reason to participate, both altruistic and self-interested factors were important motivations for participants in their decision to participate in a phase 1 vaccine clinical trial.  相似文献   
8.
9.
We and others have reported associations between B vitamins principally involved in one-carbon metabolism and increased lung cancer risk; however, results for women have been inconsistent. Here we report on the association of supplemental vitamins B6, folic acid and B12 intake and lung cancer risk using data from the Women's Health Initiative (WHI) study of postmenopausal women. Between 1993 and 1998, 161,808 women were recruited to participate in the WHI at 40 clinical centers in the US. After exclusions, 159,232 women were available for analysis and followed prospectively for an average of 18.3 years. Among them, 3,836 incident lung cancer cases were diagnosed. At baseline, supplemental B vitamins from multivitamins, vitamin mixtures and individual supplements were assessed. Adjusted Cox regression models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for associations between supplemental B vitamin intake and lung cancer risk. Relative to no intake, women who took ≥50 mg/day of vitamin B6 had 16% (HR 0.84, 95% CI: 0.71–0.99) reduced lung cancer risk. Associations did not differ significantly by smoking status or lung cancer histology. Intakes of folic acid and vitamin B12 were not associated with risk. There is a need for replication of our findings from other large, prospective studies with similar high-quality measurement of supplement intakes before any recommendations can be made at present on B6 supplementation for lung cancer prevention in women.  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