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   193670篇
  免费   35850篇
  国内免费   1409篇
耳鼻咽喉   3454篇
儿科学   4964篇
妇产科学   3845篇
基础医学   16325篇
口腔科学   7099篇
临床医学   35570篇
内科学   44644篇
皮肤病学   4974篇
神经病学   22316篇
特种医学   7534篇
外国民族医学   6篇
外科学   31501篇
综合类   1343篇
现状与发展   40篇
一般理论   73篇
预防医学   20662篇
眼科学   3754篇
药学   7697篇
中国医学   116篇
肿瘤学   15012篇
  2024年   788篇
  2023年   5451篇
  2022年   2107篇
  2021年   4679篇
  2020年   6463篇
  2019年   3813篇
  2018年   9014篇
  2017年   8854篇
  2016年   9745篇
  2015年   10183篇
  2014年   13288篇
  2013年   15956篇
  2012年   9938篇
  2011年   9734篇
  2010年   10390篇
  2009年   12310篇
  2008年   8987篇
  2007年   8437篇
  2006年   9150篇
  2005年   7683篇
  2004年   6720篇
  2003年   5824篇
  2002年   5723篇
  2001年   3609篇
  2000年   2868篇
  1999年   3269篇
  1998年   3212篇
  1997年   2836篇
  1996年   2699篇
  1995年   2441篇
  1994年   1743篇
  1993年   1512篇
  1992年   1871篇
  1991年   1674篇
  1990年   1496篇
  1989年   1467篇
  1988年   1341篇
  1987年   1173篇
  1986年   1167篇
  1985年   1105篇
  1984年   910篇
  1983年   866篇
  1982年   769篇
  1981年   644篇
  1980年   510篇
  1979年   574篇
  1978年   522篇
  1977年   481篇
  1974年   422篇
  1973年   391篇
排序方式: 共有10000条查询结果,搜索用时 3 毫秒
101.
An inverse relationship between workplace status and morbidity is well established; higher job status has been associated with reduced risks of heart disease, hypertension, and injury. Most research on job status, however, has focused on salaried populations, and it remains unclear whether job status operates similarly among hourly workers. Our objectives were to examine whether hourly status itself influences risk of hypertension after adjustment for socioeconomic confounders, and to explore the role of fine-scale job grade on hypertension incidence within hourly and salaried groups. We examined data for 14,999 aluminum manufacturing employees in 11 plants across the U.S., using logistic regression with adjustment for age, sex, race/ethnicity and other individual characteristics. Propensity score restriction was used to identify comparable groups of hourly and salaried employees, reducing confounding by sociodemographic characteristics. Job grade (coded 1 through 30, within hourly and salaried groups) was examined as a more refined measure of job status. Hourly status was associated with an increased risk of hypertension, after propensity restriction and adjustment for confounders. The observed effect of hourly status was stronger among women, although the propensity-restricted cohort was disproportionately male (96%). Among salaried workers, higher job grade was not consistently associated with decreased risk; among hourly employees, however, there was a significant trend, with higher job grades more protective against hypertension. Increasing the stringency of hypertension case criteria also increased the risk of severe or persistent hypertension for hourly employees.  相似文献   
102.
103.
104.
PURPOSE: The purpose of this study was to measure spectrophotometrically the color stability of pigmented A-2186 silicone maxillofacial elastomer with 10% by volume of titanium white dry earth opacifier before and after exposure to microwave energy over a simulated 1.5-year period of microwave sterilization. Materials AND METHODS: A-2186 silicone elastomer opacified with titanium white dry earth pigment, pigmented with 5 cosmetic dry earth pigment colors [no pigment (control) group (Pc), red (Pr), yellow ochre (Py), burnt sienna (Po), and a mixture of Pr + Py + Po color group (P3)], was used in this study. Each of the 5 experimental groups consisted of 5 specimens. All specimens were placed in a 250 ml glass beaker filled with 150 ml of water (replenished for each microwave exposure). An exposure of 6 minutes was used 18 times (simulating 1.5 years of microwave sterilization with one 6 minute exposure monthly). Reflectance values were measured by spectrophotometer. Three- and two-way analyses of variance with repeated measures were performed for the color difference (DeltaE*) with the factors of group/color/months, and group/months, respectively. Means were compared by Tukey Honest Significant Difference (HSD) multiple range test calculated at the 0.05 level of significance using SPSS. RESULTS: The trained human eye can detect color changes (DeltaE*) greater than 1.0. Most DeltaE* values of the red pigment group at all intervals and the mixed pigment group at 15- and 18- month intervals increased significantly greater than 1.0 (p < 0.001) compared with the control group. Yellow and burnt sienna groups remained the most color stable over time with DeltaE* values below 0.35. CONCLUSIONS: Lack of color stability of red dry earth pigmented A-2186 silicone maxillofacial elastomers was clinically significant after 12-month exposure to microwave energy as compared with yellow, burnt sienna, and opacified A-2186 dry earth pigments.  相似文献   
105.
106.
107.
108.
The cellular infiltrate present in human diseased gingiva was analyzed in biopsies from 12 patients with gingivitis or periodontitis. The samples studied had been obtained in the course of surgery at inflammatory sites remaining after institution of periodontal treatment. Histological and immunological techniques were used to identify macrophages, B-cells, plasma-cells, T-cells and T cell subsets, as well as cells expressing class II HLA membrane antigens. T-cells appeared as the predominant population, but plasma-cells were also visualized in nearly all samples. Both OKT4+ and OKT8+ cells were seen in all cases, the latter being more numerous in periodontitis patients. Interdigitating-like cells were observed, positively labelled for class II antigens, as well as macrophages which were more numerous in periodontitis patients. These results suggest the participation of all components of the immune response in gingival disease, in a way resembling chronic recurrent inflammatory diseases.  相似文献   
109.
110.
Summary During pacemaker implantation in a patient with permanent atrial fibrillation, it remained impossible to advance a passive fixation lead with fins through the right atrium. However, a lead with a retractable screw easily passed the right atrium and was positioned in the right ventricle. Transesophageal echocardiography revealed an extensive net–like perforated Eustachian valve within the right atrium that had caused entrapment of the anchor fins during lead implantation. Remnants of embryonal structures within the right atrium should be considered a rare possible barrier during pacemaker implantation.  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