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   19403篇
  免费   871篇
  国内免费   48篇
耳鼻咽喉   153篇
儿科学   490篇
妇产科学   399篇
基础医学   2556篇
口腔科学   644篇
临床医学   1383篇
内科学   5013篇
皮肤病学   478篇
神经病学   1643篇
特种医学   430篇
外科学   2600篇
综合类   123篇
一般理论   8篇
预防医学   1346篇
眼科学   651篇
药学   940篇
  1篇
中国医学   71篇
肿瘤学   1393篇
  2024年   68篇
  2023年   169篇
  2022年   288篇
  2021年   674篇
  2020年   386篇
  2019年   543篇
  2018年   650篇
  2017年   408篇
  2016年   421篇
  2015年   558篇
  2014年   676篇
  2013年   900篇
  2012年   1455篇
  2011年   1546篇
  2010年   833篇
  2009年   788篇
  2008年   1348篇
  2007年   1383篇
  2006年   1332篇
  2005年   1181篇
  2004年   1006篇
  2003年   985篇
  2002年   904篇
  2001年   144篇
  2000年   110篇
  1999年   147篇
  1998年   143篇
  1997年   116篇
  1996年   112篇
  1995年   102篇
  1994年   102篇
  1993年   81篇
  1992年   47篇
  1991年   56篇
  1990年   40篇
  1989年   38篇
  1988年   34篇
  1987年   38篇
  1986年   30篇
  1985年   32篇
  1984年   43篇
  1983年   35篇
  1982年   36篇
  1981年   51篇
  1980年   23篇
  1979年   25篇
  1978年   32篇
  1977年   26篇
  1976年   29篇
  1973年   20篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.

Background

Whether prolonged operative time is an independent risk factor for subsequent surgical site infection (SSI) and periprosthetic joint infection (PJI) following total joint arthroplasty (TJA) remains a clinically significant and underexplored issue. The aim of this study is to investigate the association between operative time and the risk of subsequent SSI and PJI in patients undergoing primary TJA.

Methods

We retrospectively reviewed 17,342 primary unilateral total knee arthroplasty and total hip arthroplasty performed at a single institution between 2005 and 2016, with a minimum follow-up of 1 year. A multivariate logistic regression model was conducted to identify the association between operative time and the development of SSI within 90 days and PJI within 1 year.

Results

Overall, the incidence of 90-day SSI and 1-year PJI was 1.2% and 0.8%, respectively. Patients with an operative time of >90 minutes had a significantly higher incidence of SSI and PJI (2.1% and 1.4%, respectively) compared to cases lasting between 60 and 90 minutes (1.1% and 0.7%), and those lasting ≤60 minutes (0.9% and 0.7%, P < .01). In the multivariate model, the risk for infection increased by an odds ratio of 1.346 (95% confidential interval 1.114-1.627) for 90-day SSI and 1.253 (95% confidential interval 1.060-1.481) for 1-year PJI for each 20-minute increase in operative time.

Conclusion

In patients undergoing primary TJA, each 20-minute increase in operative time was associated with nearly a 25% increased risk of subsequent PJI. We advocate that surgeons pay close attention to this underappreciated risk factor while maintaining safe operative practices, which minimize unnecessary steps and wasted time in the operating room.  相似文献   
3.
4.
Point-of-Care Ultrasound is a method of performing a rapid clinical ultrasound, with the aim of responding to a clinical question immediately. This is not an ultrasound performed systematically as the radiologists do, nor does it pretend to replace it. It is useful in some kind of screening (abdominal aortic aneurysm) and is of special interest in ultrasound-guided procedures (joint infiltration by injection).It allows to adapt the derivations, minimising the uncertainty, ruling out certain pathologies due to its high diagnostic precision. It can also lead to overdiagnosis, if the examinations carried out are not limited to the organs on which our clinical suspicion is based.Ultrasound is one tool more in the diagnostic process, but its use must be limited to certain clinical situations. Its use in early detection of prevalent diseases in Primary Care should be properly evaluated. On the other hand with more evidence of a high diagnostic accuracy in a large list of pathological conditions.  相似文献   
5.
6.
7.
Purpose: This study evaluated the microtensile bond strengths of three dentin adhesives applied on clinically moist dentin or on dentin that was dried with air for 5 seconds. The null hypothesis to test was that the level of residual moisture does not influence bond strengths when restorations are placed in vivo.
Materials and Methods: Twenty-four premolars scheduled to be extracted for orthodontic reasons from patients between the ages of 15 and 23 years were restored with one of the following adhesive systems followed by a mini hybrid composite resin: Excite (Ivoclar/Vivadent), an ethanol-based dentin adhesive; Prime & Bond NT (Dentsply/Caulk), an acetone-based dentin adhesive; and Single Bond (3M ESPE), an ethanol and water-based dentin adhesive. After extraction, the specimens were sectioned with a slow-speed diamond saw in two perpendicular directions to obtain sticks with a cross-section of 0.7 ± 0.2 mm2. The specimens were attached to a Geraldeli device and fractured using a universal testing machine at a crosshead speed of 1 mm per minute.
Results: For each dentin adhesive, there were no statistical differences between means for dry dentin versus moist dentin. Single Bond and Prime & Bond NT ranked in the same statistical subset regardless of the moisture condition of the substrate. Both Excite, dry, and Excite, moist, resulted in statistically lower bond strengths than Single Bond, moist, but similar to those of Single Bond, dry, Prime & Bond NT, moist, and Prime & Bond NT, dry.
CLINICAL SIGNIFICANCE
In this study, the level of residual moisture did not influence microtensile bond strengths. Clinically, the degree of moisture left on the dentin surface upon rinsing off the etching gel may not be as relevant as previously reported in laboratory studies.  相似文献   
8.
OBJECTIVE: The purpose of this study was to investigate the effects of low power red laser associated with acidulated phosphate fluoride on the development of induced-dental caries in rats. DESIGN: Dental caries were induced in molars of 40 rats divided into five groups: control group (CG), the teeth were not submitted to any treatment; laser group (LG), teeth were irradiated with a low power red laser (LPRL), power of 30 mW and dose of 5 J/cm(2); fluoride group (FG), teeth were treated with topical acidulated phosphate fluoride (APF) 1.23% applied for 4 min; laser+fluoride group (LFG), teeth were irradiated with LPRL followed by APF; fluoride+laser group (FLG), teeth were treated with APF followed by LPRL. The animals were killed after 48 days, and the first and second molars were extracted to analyze the caries lesion area, microhardness, and calcium and phosphorus ratio. RESULTS: There were no statistical differences among FG, LFG, and FLG regarding to caries area and microhardness, although the caries area were smaller in LFG. Ca/P ratio did not show significant differences among all groups. CONCLUSIONS: Although LPRL before APF application appeared to diminish the caries progression, LPRL did not present any additional benefit compared with acidulated phosphate fluoride on the prevention of induced-dental caries in rats.  相似文献   
9.
Serious difficulties in reporting results were encountered when using ICDAS II and PUFA separately in an epidemiological survey in a child population in Brazil. That necessitated the development of a comprehensive but pragmatic caries assessment index. This publication describes the rationale, development and content of a novel caries assessment index. Strengths and weaknesses of ICDAS II, PUFA and other indices were analysed. The novel caries index developed for use in epidemiological surveys is termed 'Caries Assessment Spectrum and Treatment' (CAST). 'Spectrum' indicates what is considered the main strength of the new index - its usefulness in describing the complete range of stages of carious lesion progression: from no carious lesion, through caries protection (sealant) and caries cure (restoration) to lesions in enamel and dentine, and the advanced stages of carious lesion progression in pulpal and tooth-surrounding tissue. CAST combines elements of the ICDAS II and PUFA indices, and the M- and F-components of the DMF index. A DMF score can easily be calculated from the CAST score, thereby enabling retention of the use of existing DMF scores. The CAST index for use in epidemiological surveys is very promising. It should be validated and its reliability and usefulness be tested in different age groups in different countries and cultures.  相似文献   
10.
The aims of this study were to demonstrate the synthesis of an experimental glass ionomer cement (GIC) by the non-hydrolytic sol-gel method and to evaluate its biocompatibility in comparison to a conventional glass ionomer cement (Vidrion R). Four polyethylene tubes containing the tested cements were implanted in the dorsal region of 15 rats, as follows: GI - experimental GIC and GII - conventional GIC. The external tube walls was considered the control group (CG). The rats were sacrificed 7, 21 and 42 days after implant placement for histopathological analysis. A four-point (I-IV) scoring system was used to graduate the inflammatory reaction. Regarding the experimental GIC sintherization, thermogravimetric and x-ray diffraction analysis demonstrated vitreous material formation at 110oC by the sol-gel method. For biocompatibility test, results showed a moderate chronic inflammatory reaction for GI (III), severe for GII (IV) and mild for CG (II) at 7 days. After 21 days, GI presented a mild reaction (II); GII, moderate (III) and CG, mild (II). At 42 days, GI showed a mild/absent inflammatory reaction (II to I), similar to GII (II to I). CG presented absence of chronic inflammatory reaction (I). It was concluded that the experimental GIC presented mild/absent tissue reaction after 42 days, being biocompatible when tested in the connective tissue of rats.  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