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   1630篇
  免费   120篇
  国内免费   9篇
耳鼻咽喉   23篇
儿科学   22篇
妇产科学   10篇
基础医学   217篇
口腔科学   101篇
临床医学   127篇
内科学   401篇
皮肤病学   43篇
神经病学   189篇
特种医学   64篇
外科学   200篇
综合类   8篇
预防医学   117篇
眼科学   77篇
药学   102篇
中国医学   7篇
肿瘤学   51篇
  2024年   2篇
  2023年   27篇
  2022年   48篇
  2021年   115篇
  2020年   64篇
  2019年   90篇
  2018年   119篇
  2017年   64篇
  2016年   69篇
  2015年   72篇
  2014年   109篇
  2013年   126篇
  2012年   161篇
  2011年   151篇
  2010年   96篇
  2009年   50篇
  2008年   80篇
  2007年   67篇
  2006年   56篇
  2005年   39篇
  2004年   36篇
  2003年   36篇
  2002年   21篇
  2001年   9篇
  2000年   11篇
  1999年   8篇
  1998年   2篇
  1996年   1篇
  1995年   3篇
  1992年   3篇
  1991年   1篇
  1988年   2篇
  1987年   4篇
  1986年   8篇
  1985年   5篇
  1984年   1篇
  1979年   1篇
  1976年   1篇
  1966年   1篇
排序方式: 共有1759条查询结果,搜索用时 0 毫秒
61.
The aim of the present study was to determine the percentage of dentists who use radiographic examination on the initial appointment, and establish the relation between the use of periodontal probe and graduation year. Dentists were interviewed in their private offices in three cities in Rio Grande do Sul. They were asked about the routine use of radiographic examination and, if applicable, what technique was applied and what clinical instrument was used at the first appointment. Opened and closed questions were included in the interview and for some of them more than one answer was possible. A significant number of dentists (62.9%) reported some kind of radiographic examination at the initial appointment. Among the radiographic techniques, the periapical was the most cited (74.3%), followed by the panoramic (36.2%) and bite-wing (32.9%) techniques. There was an association between the use of periodontal probe and the use of radiographic examination at the initial appointment. Dentists who used periodontal probe used radiographic examination more frequently (p=0.010). More recently graduated dentists (1991-2005) used radiographic examination more than the others (p=0.022). In conclusion, a large number of dentists reported the use of radiographic examination at the initial appointment. There was an association between the use of this examination technique and the use of the periodontal probe; recently graduated dentists used radiographic examinations more frequently than the others.  相似文献   
62.
An epidemiological Leishmania spp. and entomological Phlebotomine sandflies survey was performed in cat shelters at leishmaniasis endemic area of Brazil. Blood and conjunctival swab (CS) samples were collected from 94 cats in two animal protection shelters. These samples were subjected to serological tests using the indirect immunofluorescence antibody test (IFAT) and indirect enzyme‐linked immunosorbent assay (ELISA) and to molecular test by polymerase chain reaction (PCR). In addition, a Phlebotomine sandflies survey was performed in the same shelters. The analyses revealed a positivity of 31.91% (30/94) through ELISA and 29.79% (28/94) through IFAT. The two serological tests showed a positive association with perfect agreement (k = 0.925). None of the cats were positive by Leishmania spp. DNA. One Lutzomyia (Lutzomyia) longipalpis male was found in one of the cat shelters. The results and the implications of our findings are discussed below.  相似文献   
63.
64.

Introduction

The inflation pressure of the endotracheal tube cuff can cause ischemia of the tracheal mucosa at high pressures; thus, it can cause important tracheal morbidity and tracheal microaspiration of the oropharyngeal secretion, or it can even cause pneumonia associated with mechanical ventilation if the pressure of the cuff is insufficient.

Objective

In order to investigate the effectiveness of the RUSCH® 7.5 mm endotracheal tube cuff, this study was designed to investigate the physical and mechanical aspects of the cuff in contact with the trachea.

Methods

For this end, we developed an in vitro experimental model to assess the flow of dye (methylene blue) by the inflated cuff on the wall of the artificial material. We also designed an in vivo study with 12 Large White pigs under endotracheal intubation. We instilled the same dye in the oral cavity of the animals, and we analyzed the presence or not of leakage in the trachea after the region of the cuff after their deaths (animal sacrifice). All cuffs were inflated at the pressure of 30 cmH2O.

Results

We observed the passage of fluids through the cuff in all in vitro and in vivo experimental models.

Conclusion

We conclude that, as well as several other cuff models in the literature, the RUSCH® 7.5 mm tube cuffs are also not able to completely seal the trachea and thus prevent aspiration of oropharyngeal secretions. Other prevention measures should be taken.  相似文献   
65.
Cannabis use is associated with an earlier age of onset of psychosis (AOP). However, the reasons for this remain debated. Methods: We applied a Cox proportional hazards model to 410 first-episode psychosis patients to investigate the association between gender, patterns of cannabis use, and AOP. Results: Patients with a history of cannabis use presented with their first episode of psychosis at a younger age (mean years = 28.2, SD = 8.0; median years = 27.1) than those who never used cannabis (mean years = 31.4, SD = 9.9; median years = 30.0; hazard ratio [HR] = 1.42; 95% CI: 1.16–1.74; P < .001). This association remained significant after controlling for gender (HR = 1.39; 95% CI: 1.11–1.68; P < .001). Those who had started cannabis at age 15 or younger had an earlier onset of psychosis (mean years = 27.0, SD = 6.2; median years = 26.9) than those who had started after 15 years (mean years = 29.1, SD = 8.5; median years = 27.8; HR = 1.40; 95% CI: 1.06–1.84; P = .050). Importantly, subjects who had been using high-potency cannabis (skunk-type) every day had the earliest onset (mean years = 25.2, SD = 6.3; median years = 24.6) compared to never users among all the groups tested (HR = 1.99; 95% CI: 1.50- 2.65; P < .0001); these daily users of high-potency cannabis had an onset an average of 6 years earlier than that of non-cannabis users. Conclusions: Daily use, especially of high-potency cannabis, drives the earlier onset of psychosis in cannabis users.Key words: psychotic disorders, age of onset, gender, cannabis, survival plots, drug use, high-potency cannabis  相似文献   
66.
Oxaliplatin (OXA) is a platinum compound widely used in the treatment of some solid tumors, especially colorectal cancer. Despite its usefulness, oxaliplatin-associated neurotoxicity represents the main dose-limiting factor of this drug, and until now, there is no suitable treatment. Chemotherapy with oxaliplatin also increases the rate of developing hepatic damages with inflammatory activity, termed chemotherapy-associated steatohepatitis (CASH). In the present study, we aimed to compare the effects of a series of antioxidant compounds on simultaneous development of oxaliplatin-induced hepato- and neurotoxicity in mice. Mice BALB/c were treated with oxaliplatin for 6 weeks, 10 mg/kg, intraperitoneally, resulting in mechanical allodynia and hepatic steatosis. We administered the following antioxidant compounds—rutin (RT) (20 mg/kg), resveratrol (RVS) (100 mg/kg), quercetin (QT) (20 mg/kg), and quercetin nanoemulsion (NQT) (20 mg/kg)—daily by gavage to BALB/c, and N-acetylcysteine (NAC) was used as positive control. Treatments with RSV, RUT, or NQT were able to prevent mechanical allodynia when compared to the OXA group, and this effect was associated with decreased c-Fos immunopositivity in the lumbar spinal cord. Regarding the effects on steatohepatitis, RVS, QT, and NQT almost completely reversed the mean liver weight increase induced by OXA. In accordance with these previous data, histological evaluation indicated attenuation of all features of hepatic steatosis evaluated in RSV, RUT, QT, and NQT groups. These compounds were able to reduce the immunopositivity for the apoptosis marker caspase-3. On the other hand, only QT and NQT treatments were able to reduce neutrophil migration measured by myeloperoxidase (MPO) activity. These results suggest that the compounds tested, RSV, RUT, QT, and NQT, would be useful for the clinical treatment of neuro- and hepatoxicity induced by oxaliplatin.  相似文献   
67.

Background

Endothelial progenitor stem cells (EPCs) are mobilized to the peripheral circulation in response to myocardial ischemia, playing a crucial role in vascular repair. Statins have been shown to stimulate EPCs. However, neither the impact of previous statin therapy on EPC response of acute myocardial infarction (AMI) patients nor the effect of post-AMI high-intensity statin therapy on the evolution of circulating EPC levels has yet been addressed. Therefore, we aimed to compare circulating EPC levels between patients receiving long-term statin therapy before the AMI and statin-naive patients and to assess the impact of high-intensity statin therapy at discharge on the evolution of circulating EPCs post-AMI.

Methods

This is a prospective observational study of 100 AMI patients. Circulating EPCs (CD45dimCD34?+?KDR?+?cells) and their subpopulation coexpressing the homing marker CXCR4 were quantified by the high-performance flow cytometer FACSCanto II in whole blood, in two different moments: within the first 24 h of admission and 3 months post-AMI. Patients were followed up clinically for 2 years.

Results

Patients previously treated with statins had significantly higher levels of EPCs coexpressing CXCR4 (1.9?±?1.4 vs. 1.3?±?1.0 cells/1,000,000 events, p?=?0.031) than statin-naive patients. In addition, the subanalysis of diabetics (N?=?38) also revealed that patients previously on statins had significantly greater numbers of both CD45dimCD34?+?KDR?+?CXCR4+ cells (p?=?0.024) and CD45dimCD34?+?KDR?+?CD133+ cells (p?=?0.022) than statin-naive patients. Regarding the evolution of EPC levels after the AMI, patients not on a high-intensity statin therapy at discharge had a significant reduction of CD45dimCD34?+?KDR?+?and CD45dimCD34?+?KDR?+?CXCR4+ cells from baseline to 3 months follow-up (p?=?0.031 and p?=?0.005, respectively). However, patients discharged on a high-intensity statin therapy maintained circulating levels of all EPC populations, presenting at 3 months of follow-up significantly higher EPC levels than patients not on an intensive statin therapy. Moreover, the high-intensity statin treatment group had significantly better clinical outcomes during the 2-year follow-up period than patients not discharged on a high-intensity statin therapy.

Conclusion

Chronic statin therapy prior to an AMI strongly enhances the response of EPCs to myocardial ischemia, even in diabetic patients. Furthermore, high-intensity statin therapy after an AMI prevents the expected decrease of circulating EPC levels during follow-up. These results reinforce the importance of an early and intensive statin therapy in AMI patients.  相似文献   
68.
69.
70.
This paper presents a new joining method by a forming process for attaching sheets to tube ends. The process consists of two different forming stages carried out sequentially in a single stroke. Firstly, the free tube end is flared by compression with a contoured die, then is squeezed (indented) against the sheet surface to create a mechanical interlocking. The new process is carried out at an ambient temperature and, in contrast to existing joining by forming operations based on tube expansion, it avoids seal welds, tube protrusions above the sheet surfaces, and machining of grooves on the sheet holes to obtain the form-fit joints. The paper starts by analyzing the process deformation mechanics and its main operating variables and finishes by presenting examples that demonstrate its effectiveness for attaching sheets to tube ends made from polyvinylchloride and aluminum. Experimental and numerical simulation work provides support to the presentation.  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