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   3531157篇
  免费   251547篇
  国内免费   11156篇
耳鼻咽喉   47288篇
儿科学   116842篇
妇产科学   98211篇
基础医学   499147篇
口腔科学   98244篇
临床医学   329299篇
内科学   685250篇
皮肤病学   80956篇
神经病学   290133篇
特种医学   135846篇
外国民族医学   1130篇
外科学   517857篇
综合类   72772篇
现状与发展   6篇
一般理论   1345篇
预防医学   282489篇
眼科学   79462篇
药学   258293篇
  14篇
中国医学   7594篇
肿瘤学   191682篇
  2019年   27835篇
  2018年   41803篇
  2017年   32836篇
  2016年   36442篇
  2015年   42056篇
  2014年   55992篇
  2013年   83030篇
  2012年   114736篇
  2011年   117347篇
  2010年   69946篇
  2009年   67406篇
  2008年   107309篇
  2007年   113968篇
  2006年   115774篇
  2005年   117486篇
  2004年   114480篇
  2003年   107075篇
  2002年   99908篇
  2001年   160856篇
  2000年   164061篇
  1999年   140196篇
  1998年   40523篇
  1997年   35896篇
  1996年   35908篇
  1995年   34693篇
  1994年   31998篇
  1993年   30060篇
  1992年   111215篇
  1991年   107978篇
  1990年   104882篇
  1989年   101003篇
  1988年   92833篇
  1987年   91137篇
  1986年   85984篇
  1985年   81970篇
  1984年   61125篇
  1983年   52197篇
  1982年   30711篇
  1981年   27288篇
  1979年   55062篇
  1978年   38914篇
  1977年   32542篇
  1976年   30649篇
  1975年   32786篇
  1974年   39263篇
  1973年   37487篇
  1972年   35174篇
  1971年   32855篇
  1970年   30453篇
  1969年   28847篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
991.
992.
Rare kidney allograft recipients enjoy unaltered graft function years after interruption of their immunosuppressive treatment. To assess the extent to which this state of 'operational tolerance' (TOL) is specific to the graft and not the result of a global immunodeficiency, we analyzed the response of such patients following influenza vaccination. Hemagglutination inhibition titers and frequency of IFNgamma-secreting T cells were measured before 1 and 3 months after vaccination. The proportion of healthy volunteers (HV) responding to vaccine was significantly higher than that of immunosuppressed (IS) patients. Three 'TOL' patients presented a humoral response similar to that of HV, whereas the two others had a poor response, like the IS recipients. Although the small number of patients does not allow for definitive conclusions to be made, these data suggest that the status of tolerance may be heterogeneous, with some patients with a global immunodeficiency and others with an adapted response to vaccination.  相似文献   
993.
We have previously reported the time trends, design and interventions in randomised controlled trials (RCTs) in cystic fibrosis (CF) from 1961 through 1997 [Cheng K, Smyth RL, Motley J, O'Hea U, Ashby D, Randomised controlled trials in cystic fibrosis (1966-1997) categorized by time, design, and intervention. Pediatr Pulmonol 2000, 29:1-7.]. We maintain an ongoing register of all RCTs and controlled clinical trials (CCTs) in CF and have noted that in the five years since 1997 there has been a 48% increase in published trials. We aimed to assess whether this increase has been associated with an improvement in design quality. All RCTs and CCTs from 1961-2002 were assessed. Two epochs were then compared, 1961-1997 and 1998-2002. For each trial we recorded the design, participant numbers and the intervention studied. 261 trials in 1998-2002 were compared with 544 trials in 1961-1997. Comparing the two epochs a similar proportion of trials were parallel, double-blind and placebo controlled; also the median number of participants was similar. In the later epoch 25% of trials were multicentre, compared with 11% previously. Whilst this recent increase in clinical trials in CF is welcome, this has not been associated with improvements in quality. The trend for an increasing proportion of trials to be multicentre is encouraging. There are however, still deficiencies in the design of clinical trials in CF.  相似文献   
994.
Growth hormone (GH) is fundamental for the maintenance of bone mass and metabolism both during childhood and in adulthood. This effect is due to a complex interaction between circulating GH and IGF-I produced peripherally. In vitro data and experimental animal models have clarified many of the regulatory mechanisms underlying the characteristic skeletal changes occurring in acromegaly. This review focuses on the effects of GH excess on bone metabolism and mass in acromegalic patients and, in particular, on the influence of factors such as hypogonadism, gender, age and therapy on bone metabolism and arthropathy.  相似文献   
995.
The severity of illness in transplant patients and the complexity of transplant operations results in significant postoperative morbidity and mortality. Remarkable efforts have been made by transplant physicians to study and improve organ allocation, graft and patient survival, immunosuppression and the long-term management of post-transplant complications. Less effort has been spent studying the actual transplant operation and systems of acute transplant care. The National Surgical Quality Improvement Program (NSQIP) has provided a standardized approach to quality improvement and has demonstrated significant potential for a reduction in postoperative morbidity and mortality in other surgical disciplines. Medical centers are under increasing pressure to measure surgical quality and the nexus of transplant surgical quality improvement should not lie in the hands of CMS or JACHO, but rather it should be created and developed within the transplant community. The time has come for a national transplant surgical quality improvement program based on the NSQIP infrastructure. Such a proactive approach toward quality improvement from the transplant community is an excellent investment for patients, providers and health care payers.  相似文献   
996.
997.
目的:评价东部身体-智力-精神(EBMS)群体干预对进行体外受精(IVF)的中国妇女焦虑缓解的作用。设计:随机对照研究。机构:三级辅助生殖机构。受试者:227例接受第1个IVF周期治疗的妇女。干预:干预组(n=69)接受4次EBMS群体咨询,而对照组(n=115)无任何干预。主要观察指标:状态-特质焦虑问卷。结果:与对照组相比,干预组在干预后状态焦虑平均分显著下降。每组移植同样数目的卵子,但干预组没有明显更高妊娠率的倾向。  相似文献   
998.
Abstract: Data from the National Education Longitudinal Study were combined with census data at the zip code level to examine the impact of neighborhood racial and ethnic diversity and consolidated inequality, in addition to individual, family, and school factors, on the likelihood of dropping out of high school. Results indicate that while the effects for diversity and consolidated inequality did not support the stated hypotheses, main effects for family risk and prior academic achievement were significant and in the stated direction. Also, when controlling for individual, family, school, and neighborhood characteristics, African Americans were less likely than White students to drop out of school. Implications for contextual effects research and educational outcomes are discussed.  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