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   704999篇
  免费   49887篇
  国内免费   1296篇
耳鼻咽喉   9168篇
儿科学   23275篇
妇产科学   17608篇
基础医学   110407篇
口腔科学   19954篇
临床医学   63760篇
内科学   134326篇
皮肤病学   16162篇
神经病学   49436篇
特种医学   25760篇
外国民族医学   76篇
外科学   104517篇
综合类   14818篇
现状与发展   2篇
一般理论   160篇
预防医学   51431篇
眼科学   16320篇
药学   53970篇
  3篇
中国医学   2359篇
肿瘤学   42670篇
  2021年   5443篇
  2018年   7877篇
  2017年   6108篇
  2016年   6822篇
  2015年   7557篇
  2014年   10267篇
  2013年   15382篇
  2012年   20506篇
  2011年   21487篇
  2010年   12730篇
  2009年   11935篇
  2008年   19994篇
  2007年   21514篇
  2006年   21899篇
  2005年   20436篇
  2004年   19994篇
  2003年   18948篇
  2002年   18468篇
  2001年   36328篇
  2000年   36896篇
  1999年   30381篇
  1998年   7876篇
  1997年   6664篇
  1996年   6971篇
  1995年   6627篇
  1994年   6097篇
  1993年   5592篇
  1992年   22973篇
  1991年   22934篇
  1990年   22317篇
  1989年   22079篇
  1988年   20038篇
  1987年   19421篇
  1986年   18471篇
  1985年   17305篇
  1984年   12698篇
  1983年   10743篇
  1982年   5922篇
  1979年   11518篇
  1978年   8128篇
  1977年   6832篇
  1976年   6594篇
  1975年   7268篇
  1974年   8498篇
  1973年   8143篇
  1972年   7658篇
  1971年   7128篇
  1970年   6877篇
  1969年   6306篇
  1968年   5780篇
排序方式: 共有10000条查询结果,搜索用时 19 毫秒
71.
72.
73.
74.
75.
76.
77.
78.
Maternal and Child Health Journal - Background Prenatal substance use screening is recommended. The 4 P’s Plus screener includes questions on perceived problematic substance use in parents...  相似文献   
79.

Introduction The focus in clinical pharmacy practice is and has for the last 30–35 years been on changing the role of pharmacy staff into service orientation and patient counselling. One way of doing this is by involving staff in change process and as a researcher to take part in the change process by establishing partnerships with staff. On the background of the authors’ widespread action research (AR)-based experiences, recommendations and comments for how to conduct an AR-study is described, and one of their AR-based studies illustrate the methodology and the research methods used. Methodology AR is defined as an approach to research which is based on a problem-solving relationship between researchers and clients, which aims at both solving a problem and at collaboratively generating new knowledge. Research questions relevant in AR-studies are: what was the working process in this change oriented study? What learning and/or changes took place? What challenges/pitfalls had to be overcome? What were the influence/consequences for the involved parts? When to use If you want to implement new services and want to involve staff and others in the process, an AR methodology is very suitable. The basic advantages of doing AR-based studies are grounded in their participatory and democratic basis and their starting point in problems experienced in practice. Limitations Some of the limitations in AR-studies are that neither of the participants in a project steering group are the only ones to decide. Furthermore, the collective process makes the decision-making procedures relatively complex.

  相似文献   
80.
Synthetic amorphous silica (SAS) in its nanosized form is now used in food applications although the potential risks for human health have not been evaluated. In this study, genotoxicity and oxidative DNA damage of two pyrogenic (NM‐202 and 203) and two precipitated (NM‐200 and ‐201) nanosized SAS were investigated in vivo in rats following oral exposure. Male Sprague Dawley rats were exposed to 5, 10, or 20 mg/kg b.w./day for three days by gavage. DNA strand breaks and oxidative DNA damage were investigated in seven tissues (blood, bone marrow from femur, liver, spleen, kidney, duodenum, and colon) with the alkaline and the (Fpg)‐modified comet assays, respectively. Concomitantly, chromosomal damage was investigated in bone marrow and in colon with the micronucleus assay. Additionally, malondialdehyde (MDA), a lipid peroxidation marker, was measured in plasma. When required, a histopathological examination was also conducted. The results showed neither obvious DNA strand breaks nor oxidative damage with the comet assay, irrespective of the dose and the organ investigated. Similarly, no increases in chromosome damage in bone marrow or lipid peroxidation in plasma were detected. However, although the response was not dose‐dependent, a weak increase in the percentage of micronucleated cells was observed in the colon of rats treated with the two pyrogenic SAS at the lowest dose (5 mg/kg b.w./day). Additional data are required to confirm this result, considering in particular, the role of agglomeration/aggregation of SAS NMs in their uptake by intestinal cells. Environ. Mol. Mutagen. 56:218–227, 2015. © 2014 Wiley Periodicals, Inc.  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