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   92853篇
  免费   6884篇
  国内免费   243篇
耳鼻咽喉   717篇
儿科学   2905篇
妇产科学   1647篇
基础医学   12612篇
口腔科学   1939篇
临床医学   9881篇
内科学   19463篇
皮肤病学   1143篇
神经病学   8865篇
特种医学   2966篇
外国民族医学   1篇
外科学   13025篇
综合类   1252篇
一般理论   84篇
预防医学   8748篇
眼科学   2164篇
药学   6370篇
  1篇
中国医学   105篇
肿瘤学   6092篇
  2023年   453篇
  2022年   654篇
  2021年   1715篇
  2020年   1029篇
  2019年   1734篇
  2018年   2028篇
  2017年   1480篇
  2016年   1655篇
  2015年   1913篇
  2014年   2900篇
  2013年   4050篇
  2012年   6379篇
  2011年   6529篇
  2010年   3634篇
  2009年   3237篇
  2008年   5943篇
  2007年   6491篇
  2006年   6304篇
  2005年   6021篇
  2004年   5796篇
  2003年   5323篇
  2002年   5208篇
  2001年   1052篇
  2000年   906篇
  1999年   1071篇
  1998年   1150篇
  1997年   970篇
  1996年   852篇
  1995年   829篇
  1994年   698篇
  1993年   669篇
  1992年   708篇
  1991年   603篇
  1990年   579篇
  1989年   581篇
  1988年   534篇
  1987年   493篇
  1986年   535篇
  1985年   515篇
  1984年   558篇
  1983年   557篇
  1982年   564篇
  1981年   561篇
  1980年   495篇
  1979年   411篇
  1978年   423篇
  1977年   315篇
  1976年   280篇
  1975年   242篇
  1974年   253篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
Information on external validity of work site health promotion research is essential to translate research findings to practice. The authors provide a literature review of work site health behavior interventions. Using the RE-AIM framework, they summarize characteristics and results of these studies to document reporting of intervention reach, adoption, implementation, and maintenance. The authors reviewed a total of 24 publications from 11 leading health behavior journals. They found that participation rates among eligible employees were reported in 87.5% of studies; only 25% of studies reported on intervention adoption. Data on characteristics of participants versus nonparticipants were reported in fewer than 10% of studies. Implementation data were reported in 12.5% of the studies. Only 8% of studies reported any type of maintenance data. Stronger emphasis is needed on representativeness of employees, work site settings studied, and longer term results. Examples of how this can be done are provided.  相似文献   
104.
105.
Based upon the percentage of cases of IgA nephropathy (IgAN) in biopsy series, a lower prevalence has been assumed for African-Americans compared with Americans of European descent. This may be due to a racial difference in the basic underlying pathology of IgAN or to racial differences in patterns of referral and biopsy selection practices. Over the past decade (1985 – 1994), we have found similar incidences of IgAN in Caucasian and African-American children from Shelby County, Tennessee. The incidence was 3.0 cases per million per year for Caucasian and 5.7 cases per million per year for African-American children. IgAN may be more common in African-American children than previously appreciated. Population-based incidence studies will be necessary to determine whether or not our experience has become a more widespread phenomenon. Received August 21, 1996; received in revised form and accepted December 18, 1996  相似文献   
106.
A limited flip angle gradient-echo 3D volume acquisition imaging protocol for mapping partial pressure of oxygen (pO2) in perfluorocarbon compounds (PFCs) at low field (0.14 T) is presented. The pO2 measurement method is based on the paramagnetic effect of dissolved molecular oxygen (O2) which reduces the PFC 19F T1? Specific objectives related to imaging of PFCs through use of the protocol include improved image signal-to-noise characteristics and elimination of 19F chemical shift artifacts. A parametric Wiener deconvolution filtering algorithm is used for suppression of 19F chemical shift artifacts. Application of the protocol is illustrated in a series of calculated pO2 maps of a gas equilibrated, multi-chamber phantom containing perfluorotributylamine (FC-43). The utility of the protocol is demonstrated in vivo through images of a commercially available perfluorocarbon based blood substitute emulsion containing FC-43 sequestered in the liver and spleen of a rat.  相似文献   
107.
BACKGROUND: Spiral or helical arterial blood flow patterns have been widely observed in both animals and humans. The absence of spiral flow has been associated with carotid arterial disease. The aim of this study was to detect the presence of aortic spiral flow using magnetic resonance imaging (MRI) and to evaluate the relationship of the presence of spiral aortic flow with renal arterial disease and renal function in the follow-up of patients with suspected renal atheromatous disease. METHODS: Prospective study of 100 patients with suspected renal arterial disease and 44 patient controls. Using a 1.5 T MRI unit (Siemens Symphony), phase contrast flow quantification and three-dimensional contrast enhanced MR angiography of the abdominal aorta were performed. Renal arterial stenoses (RAS) were classified minimal, moderate or severe. Renal function was followed at 3 months before and 6 months after MRI. RESULTS: Non-spiral flow was more prevalent in patients with more severe RAS. Renal impairment progressed significantly in severe RAS without spiral flow (P = 0.0065), but did not progress significantly in severe RAS with spiral flow (P = 0.12). In minimal or moderate RAS with or without spiral flow there was no significant progression (P = 0.16, 0.13, 0.47, 0.092, respectively). CONCLUSIONS: Aortic spiral blood flow can be assessed with MRI. Lack of aortic spiral blood flow in patients with severe RAS is associated with significant short-term renal function deterioration. Determination of blood flow patterns may be a useful indicator of renal impairment progression in patients with suspected renal artery stenosis.  相似文献   
108.
Factors that are known to influence plasmid transfer in bacterial populations were studied for the conjugative plasmid pWG613, which determined gentamicin resistance in Staphylococcus aureus. The transfer frequency was largely unaffected over a wide range of temperature (18-42 degrees C); pH also had little effect on the transfer frequency in the range 5.0-8.5. High cell density and log phase cultures were required for optimal plasmid transfer, as were donor:recipient ratios of 0.003-3.3.  相似文献   
109.
This paper documents the type, frequency and duration of complications associated with regional anaesthesia of the maxillary nerve via the greater palatine canal in a series of 101 patients treated in the Oral Surgery Department, United Dental Hospital of Sydney.  相似文献   
110.
Public concern surrounding antibiotic contamination in food and food products has made it imperative to develop analytical methods for their detection. Polyclonal antibodies were used in the development of a surface plasmon resonance (SPR)-based inhibition immunoassay for cephalexin. A conjugate consisting of cephalexin-bovine serum albumin (BSA) was immobilized on the dextran gel surface of the sensor chip. Binding/regeneration studies of antibody to immobilized cephalexin were studied and dissociation of the antibody from the immobilized cephalexin was easily achieved with 10 mmol l-1 NaOH. Forty surface regeneration cycles were carried out and found to be reproducible with only a 7.4% decrease in binding over this number of regenerations. Model inhibition immunoassays for cephalexin were developed in PBS and spiked milk samples with detection ranges of 4.88 to 2,500 ng ml-1 and 244 to 3,906 pg ml-1, respectively.  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