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   6712篇
  免费   273篇
  国内免费   84篇
耳鼻咽喉   79篇
儿科学   119篇
妇产科学   317篇
基础医学   658篇
口腔科学   221篇
临床医学   519篇
内科学   1788篇
皮肤病学   86篇
神经病学   377篇
特种医学   327篇
外科学   1266篇
综合类   25篇
一般理论   1篇
预防医学   223篇
眼科学   339篇
药学   250篇
中国医学   4篇
肿瘤学   470篇
  2024年   6篇
  2023年   69篇
  2022年   132篇
  2021年   201篇
  2020年   118篇
  2019年   177篇
  2018年   232篇
  2017年   119篇
  2016年   174篇
  2015年   180篇
  2014年   268篇
  2013年   382篇
  2012年   519篇
  2011年   607篇
  2010年   372篇
  2009年   367篇
  2008年   503篇
  2007年   579篇
  2006年   521篇
  2005年   451篇
  2004年   354篇
  2003年   271篇
  2002年   210篇
  2001年   50篇
  2000年   20篇
  1999年   21篇
  1998年   38篇
  1997年   20篇
  1996年   22篇
  1995年   17篇
  1994年   9篇
  1993年   5篇
  1992年   10篇
  1991年   1篇
  1990年   2篇
  1989年   8篇
  1988年   3篇
  1987年   3篇
  1986年   1篇
  1984年   8篇
  1983年   7篇
  1982年   4篇
  1981年   2篇
  1980年   2篇
  1978年   1篇
  1977年   1篇
  1969年   1篇
  1967年   1篇
排序方式: 共有7069条查询结果,搜索用时 15 毫秒
91.
It is known that visual direction representation is more accurate for cardinal directions compared to oblique, a phenomenon named the “oblique effect”. It has been hypothesized that there are two sources of oblique effect, a low level one confined to vision and a high level one extending to different modalities and corresponding to higher cognitive processes. In this study directional error (DE) was measured when normal individuals tried to align the direction of an arrow presented in the center of a computer monitor to the direction of a peripheral target located in one of 32 directions equally spaced on an imaginary circle of 60 mm radius. Task difficulty was manipulated by varying arrow length (15, 30, 45 and 60 mm). By measuring mean DE and its variance we identified two independent sources of the oblique effect. A low level oblique effect was manifested in higher accuracy or equivalently lower variance of DE in the alignment for cardinal orientations compared to oblique. A second oblique effect was manifested measuring mean DE resulting in space expansion in the vicinity of cardinal directions and space contraction in the vicinity of oblique directions. Only this latter source of oblique effect was modulated by arrow length as predicted from a theoretical model postulating that this oblique effect is produced by a cognitive process of 2-D space categorization.  相似文献   
92.
93.
The following consensus report is based on four background reviews. The frequency of maintenance visits is based on patient risk indicators, homecare compliance and prosthetic design. Generally, a 6‐month visit interval or shorter is preferred. At these visits, peri‐implant probing, assessment of bleeding on probing and, if warranted, a radiographic examination is performed. Diagnosis of peri‐implant mucositis requires: (i) bleeding or suppuration on gentle probing with or without increased probing depth compared with previous examinations; and (ii) no bone loss beyond crestal bone level changes resulting from initial bone remodelling. Diagnosis of peri‐implantitis requires: (i) bleeding and/or suppuration on gentle probing; (ii) an increased probing depth compared with previous examinations; and (iii) bone loss beyond crestal bone level changes resulting from initial bone remodelling. If diagnosis of disease is established, the inflammation should be resolved. Non‐surgical therapy is always the first choice. Access and motivation for optimal oral hygiene are key. The patient should have a course of mechanical therapy and, if a smoker, be encouraged not to smoke. Non‐surgical mechanical therapy and oral hygiene reinforcement are useful in treating peri‐implant mucositis. Power‐driven subgingival air‐polishing devices, Er: YAG lasers, metal curettes or ultrasonic curettes with or without plastic sleeves can be used to treat peri‐implantitis. Such treatment usually provides clinical improvements such as reduced bleeding tendency, and in some cases a pocket‐depth reduction of ≤ 1 mm. In advanced cases, however, complete resolution of the disease is unlikely.  相似文献   
94.
This meta‐analysis aims to compare serum uric acid levels among preeclamptic and healthy pregnant women across the various trimesters and provide a summary of the effect size of this biomarker in predicting adverse pregnancy outcomes. MEDLINE, Scopus, CENTRAL, Clinicaltrials.gov, and Google Scholar databases were systematically searched from inception. Observational studies were held eligible if they reported serum uric acid among preeclamptic and healthy pregnant women. Meta‐analysis was conducted regarding uric acid concentration, diagnostic accuracy, and association with perinatal outcomes. The credibility of evidence was appraised using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework. The analysis included 196 studies, comprising 39 540 women. Preeclampsia was associated with significantly elevated uric acid levels during the 1st (mean difference [MD]: 0.21 mg/dL, 95% confidence intervals [CI]: 0.06‐0.35) trimester, 2nd (MD: 1.41 mg/dL, 95% CI: 0.78‐2.05) trimester, and 3rd (MD: 2.26 mg/dL, 95% CI: 2.12‐2.40) trimester. Higher uric acid was estimated for severe preeclampsia, eclampsia, and hemolysis, elevated liver enzymes, low platelet syndrome. The sensitivity for adverse perinatal outcome prediction ranged from 67.3% to 82.7% and the specificity from 47.7% to 70.7%. In conclusion, it is suggested that serum uric acid levels are increased in preeclampsia and can be used to predict disease severity and pregnancy complications. Future prospective studies should verify these outcomes, assess the optimal cutoffs, and incorporate uric acid to combined predicting models.  相似文献   
95.
96.
97.
98.
99.
Melanin pigment and melanocytes may be found in odontogenic cysts and tumors, particularly calcifying cystic odontogenic tumor (CCOT). In the present study we investigated the immunohistochemical expression of the Melan-A/Mart-1 and HMB-45 antigens in 13 Caucasians patients with CCOT. Melan-A/Mart-1- and HMB-45-positive melanocytes were not seen in any of the cases. Our findings are in agreement with the assumption that pigmentation in odontogenic lesions may be a racial phenomenon.  相似文献   
100.
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