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   67953篇
  免费   4390篇
  国内免费   279篇
耳鼻咽喉   940篇
儿科学   1675篇
妇产科学   1350篇
基础医学   8405篇
口腔科学   1428篇
临床医学   7222篇
内科学   13870篇
皮肤病学   1158篇
神经病学   6776篇
特种医学   2178篇
外科学   10886篇
综合类   866篇
一般理论   81篇
预防医学   5194篇
眼科学   1422篇
药学   4095篇
  3篇
中国医学   63篇
肿瘤学   5010篇
  2023年   309篇
  2022年   529篇
  2021年   1254篇
  2020年   754篇
  2019年   1264篇
  2018年   1530篇
  2017年   1151篇
  2016年   1334篇
  2015年   1462篇
  2014年   2109篇
  2013年   2968篇
  2012年   4667篇
  2011年   5149篇
  2010年   2756篇
  2009年   2573篇
  2008年   4513篇
  2007年   4648篇
  2006年   4597篇
  2005年   4625篇
  2004年   4384篇
  2003年   4139篇
  2002年   3866篇
  2001年   697篇
  2000年   652篇
  1999年   759篇
  1998年   815篇
  1997年   665篇
  1996年   609篇
  1995年   614篇
  1994年   519篇
  1993年   438篇
  1992年   481篇
  1991年   391篇
  1990年   404篇
  1989年   345篇
  1988年   380篇
  1987年   319篇
  1986年   304篇
  1985年   299篇
  1984年   332篇
  1983年   316篇
  1982年   383篇
  1981年   345篇
  1980年   289篇
  1979年   213篇
  1978年   217篇
  1977年   176篇
  1976年   136篇
  1974年   135篇
  1973年   111篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
Chronic mesenteric ischemia classically presents as “intestinal angina” with generalized postprandial abdominal pain lasting up to 3 hours. Over time, these episodes can become much more intense and ultimately lead to sitophobia with significant weight loss. Symptoms are not specific and often mistakenly attributed to other gastrointestinal etiologies such as peptic ulcer disease. Gastric ulcerations as a direct result of mesenteric ischemia have been reported but are relatively rare because of the rich collateral blood supply to the stomach. Therefore, a diagnosis of ischemic gastropathy is seldom entertained in patients presenting with abdominal pain and gastriculcers.  相似文献   
993.
994.
995.
996.
997.
Aims   To establish the prevalence of recanting of life-time inhalant use, identify correlates of recanting to gain insight to its causes and develop a method for distinguishing recanters who truly are versus are not life-time users of inhalants.
Design and setting   Longitudinal survey data from students in 62 South Dakota middle schools who were participating in a field trial to evaluate a school-based drug prevention program.
Measurements   At grades 7–8, participants reported on their life-time inhalant use, other drug use and drug-related beliefs, attitudes and behaviors.
Findings   Forty-nine per cent of students who reported life-time inhalant use at grade 7 recanted their reports a year later. Comparison of students who recanted inhalant use with those who did or did not report inhalant use consistently on drug-related beliefs, attitudes and behaviors at grades 7 and 8 suggested that, whereas some inhalant use recanting reflects denial of past behavior, some reflects erroneous initial reporting. Based on a latent mixture model fitted to the multivariate distribution of grade 7 and grade 8 responses of recanters and consistent reporters, we calculated the probability that each recanter was, in fact, a life-time inhalant user. An estimated 67% of the recanters in our sample appear to be life-time inhalant users who admitted use in grade 7 and then denied that use at grade 8; 33% appear to be students who reported use incorrectly at grade 7 and then corrected that error at grade 8.
Conclusions   Inhalant use recanting is a significant problem that, if not handled carefully, is likely to have a considerable impact on our understanding of the etiology of inhalant use and efforts to prevent it.  相似文献   
998.
Title.  Nurse education: factors associated with attrition.
Aim.  This paper is a report of a study to identify the factors having an impact on student completion rates in a preregistration programme.
Background.  Nursing student attrition is an international issue causing concern in many parts of the developed world including Australia, the United States and Europe. In the United Kingdom, nursing student attrition has become a major issue, despite having one of the lowest general university dropout rates in the developed world.
Method.  A retrospective cohort study was conducted in 2007 using routinely-collected demographic and completion data on four cohorts of nursing students (1259 in total) studying at a large English university.
Findings.  Students who were older on entry were more likely to complete the programme than younger students, and those who had only the minimum educational qualifications on entry were less likely to complete than those with higher-level qualifications. There was some evidence of increased risk of resigning from the course in students taking the child branch, and increased risk of discontinuation (involuntary removal) from the course in both male and black/minority ethnic students. There was also some evidence that the healthcare organization responsible for a student's placement could influence completion rates.
Conclusion.  To improve attrition rates on preregistration nursing programmes, higher education institutions should actively target recruitment at mature candidates; increase the level of qualification required to gain entry; examine course structures for flexibility and provide multi-level student support.  相似文献   
999.
1000.
Recruitment of immune cells to infection sites is a critical component of the host response to pathogens. This process is facilitated partly through interactions of chemokines with cognate receptors. Here, we examine the importance of fractalkine (CX3CL1) receptor, CX3CR1, which regulates function and trafficking of macrophages and dendritic cells, in the host''s ability to control respiratory infections with Mycobacterium tuberculosis or Francisella tularensis. Following low-dose aerosol challenge with M. tuberculosis, CX3CR1−/− mice were no more susceptible to infection than wild-type C57BL/6 mice as measured by organ burden and survival time. Similarly, following inhalation of F. tularensis, CX3CR1−/− mice displayed similar organ burdens to wild-type mice. CX3CR1−/− mice had increased recruitment of monocytes and neutrophils in the lung; however, this did not result in increased abundance of infected monocytes or neutrophils. We conclude that CX3CR1-deficiency affects immune-cell recruitment; however, loss of CX3CR1 alone does not render the host more susceptible to M. tuberculosis or F. tularensis.  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