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   4071876篇
  免费   301680篇
  国内免费   10213篇
耳鼻咽喉   57472篇
儿科学   130346篇
妇产科学   111125篇
基础医学   568460篇
口腔科学   116940篇
临床医学   375161篇
内科学   789274篇
皮肤病学   91239篇
神经病学   337997篇
特种医学   158541篇
外国民族医学   1438篇
外科学   610010篇
综合类   91174篇
现状与发展   6篇
一般理论   1720篇
预防医学   325251篇
眼科学   94693篇
药学   301251篇
  11篇
中国医学   7983篇
肿瘤学   213677篇
  2018年   43661篇
  2017年   33588篇
  2016年   38158篇
  2015年   43064篇
  2014年   60631篇
  2013年   92053篇
  2012年   122327篇
  2011年   129806篇
  2010年   77838篇
  2009年   74422篇
  2008年   121821篇
  2007年   129406篇
  2006年   131155篇
  2005年   126801篇
  2004年   122199篇
  2003年   117809篇
  2002年   114653篇
  2001年   187045篇
  2000年   192534篇
  1999年   163293篇
  1998年   48481篇
  1997年   43265篇
  1996年   42903篇
  1995年   41613篇
  1994年   38636篇
  1993年   36149篇
  1992年   129754篇
  1991年   125525篇
  1990年   121333篇
  1989年   117245篇
  1988年   108365篇
  1987年   106747篇
  1986年   100817篇
  1985年   96579篇
  1984年   72640篇
  1983年   62030篇
  1982年   37355篇
  1981年   33615篇
  1979年   66747篇
  1978年   47233篇
  1977年   40022篇
  1976年   37492篇
  1975年   39595篇
  1974年   47988篇
  1973年   45810篇
  1972年   43106篇
  1971年   39923篇
  1970年   37306篇
  1969年   35274篇
  1968年   32452篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
161.
This prospective clinic-based study evaluated the pretreatment periodontal status of the orthodontic patients seen at the University College Hospital, Ibadan, Nigeria, and assessed the relationship between dental aesthetic index (DAI) scores and periodontal status according to community periodontal index of treatment needs (CPITN) scores. One hundred forty five patients-70 (48.3%) males and 75 (51.7%) females from 6 to 45 years (mean 15.8 +/- 7.5)-were seen. World Health Organization (WHO) guidelines were followed in the examination and reporting of the periodontal status, and DAI scores were assessed based on WHO guidelines. The chi-square test was used to determine the association between the DAI and the CPITN scores. Most patients were in the 6-15 (55.9%) or 16-25 (35.9%) age groups. Based on the WHO preferred cumulative calculations of treatment need (TN), 35.2% of the patients had TN 0, 64.9% had TN 1, 24.9% had TN 2, and only 0.7% had TN 3. The relationship between DAI scores and periodontal treatment needs was not statistically significant (P >.05). Although many patients were yet to attain the WHO goal of no more than 1 sextant affected by bleeding or calculus at the age of 15, over one third had satisfactory periodontal health.  相似文献   
162.
163.
164.
Four clinical trials of porcine islet transplantation have been reported, and there are verbal reports that clinical trials on much larger scales are continuing in centers in China and Russia. The four reported trials are briefly reviewed and, in the light of the present status of experimental islet xenotransplantation, consideration is given to whether such trials are currently justified. The Ethics Committee of the International Xenotransplantation Association has (1) emphasized the need for encouraging studies in non-human primates before clinical trials should be undertaken, (2) mandatory monitoring for the transfer of porcine microorganisms, and (3) careful regulation and oversight by recognized bodies. Other aspects of the topic, such as the need for informed consent, are briefly discussed. We conclude that, at the present time, more data documenting convincing efficacy, focused on clinically applicable immunosuppressive regimens, are needed to justify the initiation of closely monitored clinical trials. A clinical trial may then be justified even though the potential risk to the patients, and possibly for society, will not be zero.  相似文献   
165.
Summary: The mosaic (Atp7a mo-ms ) is an X-linked, lethal mutation in mice. In mosaic mutant males, many clinical features characteristic of defective copper metabolism have been observed and they die at the age of 15 days, exhibiting strongsimilarities to the brindled and macular mutants. About 4% of the mutant males live to sexual maturity and some of them are fertile. In this paper, alterationsin the structure of the kidney from adult mutants are described. Owing to an inherited defect of efflux, copper is accumulated in the kidney of the mutants up to a toxic level and this leads to severe damage of the renal cortex. Pathological changes in the kidney mostly affected the structure of the renal corpuscle and renaltubules.  相似文献   
166.
167.
OBJECTIVE: To determine whether under-reporting of rheumatic fever occurs at hospital, municipal, provincial and national levels of the South African health system. BACKGROUND: Information on the incidence of rheumatic fever (RF) and the prevalence of rheumatic heart disease (RHD) is required for the prevention of valvular heart disease in developing countries. In South Africa, RF was made a notifiable condition in 1989. It has recently been suggested that the reporting of RF cases may be incomplete, possibly because of underreporting by health care professionals and deficient administration of the disease notification system in South Africa. METHOD AND RESULTS: We assessed whether underreporting of RF cases occurs by comparing the numbers of RF cases reported per year at hospital, municipal, provincial and national levels from 1990 to 2004. There was a fall in the number of RF cases reported per year at national and provincial level over the 15 years of observation. A detailed analysis of the number of RF cases reported at hospital, municipal and provincial level for a 5-year period showed that more cases were diagnosed in one hospital (serving a smaller population) than were captured at municipal and provincial level (serving a larger population), suggesting underreporting by health care professionals. There were discrepancies in the number of cases reported at municipal, provincial and national level, suggesting poor administration of the notification system. CONCLUSION: There appears to be underreporting of RF cases by health care professionals, and poor administration of the RF notification system. Health care professionals need to be educated about the statutory requirement to notify all RF cases in South Africa. An effective national disease notification system is required.  相似文献   
168.
169.
Research coordinators in intensive care are a growing specialty about which little is known. This cross-sectional study surveyed the Australia and New Zealand Intensive Care Research Coordinators' Group (n = 49) regarding demographics, education, employment history, job structure, and role content. Most research coordinators were highly qualified and experienced nurses who undertake pharmaceutical trials, multicenter projects, departmental medical and nursing research, audits and data registries, and their own projects.  相似文献   
170.
OBJECTIVE: Respiratory muscle endurance of able-bodied persons, assessed by normocapnic hyperpnoea at 70% of their maximal voluntary ventilation, usually ranges from 10 to 20 minutes. The aim of this study was to determine the level of ventilation that patients with paraplegia and tetraplegia can sustain for 10-20 minutes to later be used as the guideline for respiratory muscle endurance training. DESIGN: Pilot study; cross-over setting. SUBJECTS: Two groups, 8 patients with paraplegia and 6 with tetraplegia. METHODS: Respiratory muscle endurance tests were performed at 3 different intensities of normocapnic hyperpnoea, i.e. 20%, 40% and 60% maximal voluntary ventilation. Subjects performed partial re-breathing from a bag to assure normocapnia. Respiratory endurance was separately analysed for patients with paraplegia and tetraplegia. RESULTS: Mean respiratory endurance times were 46.0, 18.9 and 4.2 minutes at 20%, 40% and 60% maximal voluntary ventilation in patients with tetraplegia and 51.8, 38.8 and 12.2 minutes in patients with paraplegia. The duration differed significantly at 60% maximal voluntary ventilation between the groups. CONCLUSION: Minute ventilation to perform respiratory muscle endurance training can be set at around 40% of maximal voluntary ventilation for patients with tetraplegia and around 60% of maximal voluntary ventilation for patients with paraplegia, as these levels can be sustained for 10-20 minutes.  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