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   1487950篇
  免费   119117篇
  国内免费   3584篇
耳鼻咽喉   19324篇
儿科学   48577篇
妇产科学   42085篇
基础医学   210867篇
口腔科学   38605篇
临床医学   134607篇
内科学   300634篇
皮肤病学   34213篇
神经病学   124384篇
特种医学   56708篇
外国民族医学   471篇
外科学   223104篇
综合类   33651篇
现状与发展   3篇
一般理论   582篇
预防医学   116216篇
眼科学   33313篇
药学   103653篇
  2篇
中国医学   3450篇
肿瘤学   86202篇
  2021年   12996篇
  2019年   13674篇
  2018年   18889篇
  2017年   14391篇
  2016年   16027篇
  2015年   18043篇
  2014年   25530篇
  2013年   37338篇
  2012年   51525篇
  2011年   54336篇
  2010年   31732篇
  2009年   30169篇
  2008年   49554篇
  2007年   52346篇
  2006年   52515篇
  2005年   50877篇
  2004年   48285篇
  2003年   45862篇
  2002年   44006篇
  2001年   73641篇
  2000年   74954篇
  1999年   62146篇
  1998年   17751篇
  1997年   16009篇
  1996年   16046篇
  1995年   15216篇
  1994年   13795篇
  1993年   12970篇
  1992年   46135篇
  1991年   43731篇
  1990年   41744篇
  1989年   39759篇
  1988年   36383篇
  1987年   35534篇
  1986年   33041篇
  1985年   31464篇
  1984年   24023篇
  1983年   20208篇
  1982年   12431篇
  1981年   11012篇
  1979年   20834篇
  1978年   14710篇
  1977年   12199篇
  1976年   11441篇
  1975年   11692篇
  1974年   14067篇
  1973年   13595篇
  1972年   12685篇
  1971年   11519篇
  1970年   10948篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
A 72-year-old man presented with a short duration of symptoms relating to a right fronto-parietal glioblastoma and a family history of children with brain tumours. Analysis of the patient's family tree revealed that out of seven children, he had a living son with anaplastic astrocytoma, a daughter who had died with a glioblastoma, and a son who had died with a histologically undiagnosed intrinsic brain tumour. One niece was also thought to have died from a brain tumour. All of the other affected family members had onset in their third or fourth decades. Tissue was only available from two of the affected individuals, precluding familial genetic analysis at this stage. There is no clinical evidence to support a diagnosis of a multiple cancer or neurocutaneous syndrome in this family. In view of what is known about the genetics of familial glioma, it is interesting to note the clinical evidence of both 'primary' glioblastoma and anaplastic astrocytoma in the same kindred.  相似文献   
92.
93.
94.
Liposarcomas are extremely rare in the mediastinum. They may achieve considerable size before causing any symptoms. Mediastinal liposarcomas may invade surrounding structures like the pericardium or the superior vena cava. Complete surgical excision is the optimal treatment in resectable cases. Excision of adjacent structures like the pericardium may be needed if the tumor infiltrates them. We report on a case of a giant liposarcoma of the mediastinum involving both hemithoraces and extending into the neck, which was successfully managed by complete surgical excision.  相似文献   
95.
96.
At the time of hire, 4059 of 6522 healthcare workers required a 2-step tuberculin skin test; 114 workers (2.8%) demonstrated a boosted reaction after the second step. Boosted reactions were significantly associated with male sex and older age. A verbal history of previous tuberculin skin test results was not a reliable indicator of baseline tuberculin skin test status at the time of hire.  相似文献   
97.
BACKGROUND: An augmented reality tool for computer assisted surgery named X-Scope allows visual tracking of real anatomical structures in superposition with volume rendered CT or MRI scans and thus can be used for navigated translocation of bony segments. METHODS: In a feasibility study X-Scope was used in orthognathic surgery to control the translocation of the maxilla after Le Fort I osteotomy within a bimaxillary procedure. The situation achieved was compared with the pre-operative situation by means of cephalometric analysis on lateral and frontal cephalograms. RESULTS: The technique was successfully utilized in 5 patients. Maxillary positioning using X-Scope was accomplished accurately within a range of 1mm. The tool was used in all cases in addition to the usual intra-operative splints. A stand-alone application without conventional control does not yet seem reasonable. CONCLUSION: Augmented reality tools like X-Scope may be helpful for controlling maxillary translocation in orthognathic surgery. The application to other interventions in cranio-maxillofacial surgery such as Le Fort III osteotomy, fronto-orbital advancement, and cranial vault reshaping or repair may also be considered.  相似文献   
98.
The authors discuss techniques for Monte Carlo (MC) cohort simulations that reduce the number of simulation replications required to achieve a given degree of precision for various output measures. Known as variance reduction techniques, they are often used in industrial engineering and operations research models, but they are seldom used in medical models. However, most MC cohort simulations are well suited to the implementation of these techniques. The authors discuss the cost of implementation versus the benefit of reduced replications.  相似文献   
99.
Consecutive patients (n = 215) who were referred to optometric (55%) or multidisciplinary (45%) low-vision services and above 50 years of age were recruited from four hospitals in the Netherlands. They completed two vision-related quality of life questionnaires, the Vision Quality of Life Core Measure (VCM1) and the Low Vision Quality of Life Questionnaire (LVQOL), before their first visit with low-vision services and 1 year later. At follow-up, patients referred to multidisciplinary low-vision services had lower scores on the mobility subscale of the LVQOL than patients referred to optometric low-vision services [5.3 points; 95% confidence interval (CI): 0.2-10.5]. Paired sample t-tests for the two groups of patients taken together show improvement for the VCM1 (3.1 points; 95% CI: 0.6-5.6) and deterioration for the basic aspects of vision (3.5 points; 95% CI: 1.1-5.9) and the mobility (6.6 points; 95% CI: 3.7-9.5) subscales of the LVQOL. In conclusion, people referred to optometric services showed less deterioration in mobility than those referred to multidisciplinary services. No differences were observed for any of the other subscales of the LVQOL and the VCM1. Future research in this field should include randomized controlled designs comparing low-vision services with no treatment or placebo.  相似文献   
100.
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   
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