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   2860篇
  免费   149篇
  国内免费   81篇
耳鼻咽喉   18篇
儿科学   191篇
妇产科学   44篇
基础医学   335篇
口腔科学   151篇
临床医学   303篇
内科学   664篇
皮肤病学   120篇
神经病学   111篇
特种医学   405篇
外科学   154篇
综合类   46篇
预防医学   213篇
眼科学   44篇
药学   159篇
  2篇
中国医学   4篇
肿瘤学   126篇
  2023年   11篇
  2022年   28篇
  2021年   39篇
  2020年   37篇
  2019年   43篇
  2018年   62篇
  2017年   37篇
  2016年   56篇
  2015年   83篇
  2014年   89篇
  2013年   109篇
  2012年   120篇
  2011年   140篇
  2010年   138篇
  2009年   108篇
  2008年   106篇
  2007年   137篇
  2006年   94篇
  2005年   90篇
  2004年   50篇
  2003年   35篇
  2002年   42篇
  2001年   48篇
  2000年   33篇
  1999年   38篇
  1998年   133篇
  1997年   156篇
  1996年   133篇
  1995年   108篇
  1994年   116篇
  1993年   98篇
  1992年   30篇
  1991年   38篇
  1990年   43篇
  1989年   57篇
  1988年   49篇
  1987年   43篇
  1986年   50篇
  1985年   45篇
  1984年   27篇
  1983年   18篇
  1982年   25篇
  1981年   31篇
  1980年   27篇
  1979年   5篇
  1978年   9篇
  1977年   19篇
  1976年   25篇
  1975年   14篇
  1966年   3篇
排序方式: 共有3090条查询结果,搜索用时 15 毫秒
101.
102.

Purpose

It has been suggested that subjective measures of oral health are influenced by both individual and contextual characteristics. This study assessed the relationship between neighborhood and individual social networks and child oral health-related quality of life (COHRQoL).

Methods

This study followed a cross-sectional design using a multistage sample of 478 children aged 1–5 years old. Caregivers completed the Brazilian version of the Early Childhood Oral Health Impact Scale (ECOHIS) and answered questions related to socioeconomic status and social network. The dental examination provided information on the prevalence of dental caries, dental trauma, and occlusion. Contextual social determinants included the presence of cultural community centers and of workers’ association in the neighborhood. Data analysis considered the total ECOHIS scores as the outcome and neighborhood/individual social networks as the independent variables. A multilevel Poisson regression model was used to investigate the association among individual and contextual characteristics and COHRQoL.

Results

Total ECOHIS scores ranged from 0 to 41 (possible range 0–52). The mean ECOHIS score was low (mean = 1.8, SD = 3.9), and the functional domain presented the highest mean impact on COHRQoL (mean = 0.5, SD = 1.4). Following adjusted analysis, low household income, visiting a neighbor less than once a month, the presence of anterior open bite, dental trauma, and dental caries were identified as individual determinants of negative impact on a child’s quality of life. These variables remained associated with the outcome even after adding the contextual-level variables in the model. At the contextual level, the presence of community cultural centers was associated with overall mean ECOHIS score; higher impacts on COHRQoL were observed in those living in neighborhoods without cultural community centers.

Conclusion

There is a significant association between individual and contextual social determinants and COHRQoL; unfavorable social conditions and poor socioeconomic status have a negative impact on caregiver reports of children’s oral health-related quality of life.  相似文献   
103.
104.
105.
Placebo controls play a critical role in the evaluation of any pharmacotherapy. This review surveys the placebo arm in 12 randomized controlled trials (RCTs) investigating burning mouth syndrome (BMS) and documents a positive placebo response in 6 of them. On average, treatment with placebos produced a response that was 72% as large as the response to active drugs. The lack of homogeneity in the use of placebos adds to the difficulty in comparing results and aggregating data. Future RCTs investigating BMS would benefit from larger sample sizes, adequate follow‐up periods, and use of a standard placebo.  相似文献   
106.

Objectives

The aims of this study were to compare 2-year cumulative survival rates of amalgam and atraumatic restorative treatment (ART) restorations in primary molars and to investigate the determinants of the survival rate of restorations.

Materials and methods

A controlled clinical trial using a parallel group design was carried out on 258 children aged 6–7 years old, allocated to two treatment groups: conventional restorative treatment using amalgam and ART using high-viscosity glass ionomer. A total of 364 amalgam restorations and 386 ART restorations were placed by three pedodontists in 126 and 158 children, respectively, and were evaluated after 0.5, 1, and 2 years. Restorations were placed in vital primary molars with neither pain nor signs of pulp involvement. The survival analysis was conducted using the proportional hazard rate regression model with frailty correction.

Results

The 2-year cumulative survival rates for all amalgam (77.3 %) and ART (73.5 %) restorations were not statistically significantly different, but there was an effect of “type of surface” (single/multiple) and “cavity filling time” on the survival rates. Both amalgam and ART single-surface restorations had higher survival rates than multiple-surface restorations of the same material. Secondary caries was responsible for 36 and 38 % of failures in amalgam and ART restorations, respectively. Mean time for restoring all type of cavities with amalgam and ART restorations was 13.6 and 13.7 min, respectively.

Conclusions

Amalgam and ART restorations presented similar survival rates over a 2-year period for all, single-surface, and multiple-surface restorations.

Clinical relevance

In the cause of finding alternatives to amalgam, ART restorations using high-viscosity glass ionomer might be a suitable option for managing cavitated dentine carious lesions in vital primary molars.  相似文献   
107.
Silk fibroin (SF) hydrogels can be obtained via self‐assembly, but this process takes several days or weeks, being unfeasible to produce cell carrier hydrogels. In this work, a phospholipid, namely, 1,2‐dimyristoyl‐sn‐glycero‐3‐phospho‐(1′‐rac‐glycerol) sodium salt (DMPG), was used to induce and accelerate the gelation process of SF solutions. Due to the amphipathic nature and negative charge of DMPG, electrostatic and hydrophobic interactions between the phospholipids and SF chains will occur, inducing the structural transition of SF chains to the beta sheet and consequently a rapid gel formation is observed (less than 50 min). Moreover, the gelation time can be controlled by varying the lipid concentration. To assess the potential of the hydrogels as cell carriers, several mammalian cell lines, including L929, NIH/3T3, SaOS‐2, and CaSki, were encapsulated into the hydrogel. The silk‐based hydrogels supported the normal growth of fibroblasts, corroborating their cytocompatibility. Interestingly, an inhibition in the growth of cancer‐derived cell lines was observed. Therefore, DMPG‐induced SF hydrogels can be successfully used as a 3D platform for in situ cell encapsulation, opening promising opportunities in biomedical applications, such as in cell therapies and tissue regeneration.  相似文献   
108.
109.
Glycogen phosphorylase (GP) is a key enzyme in the glycogenolysis pathway. GP inhibitors are currently under investigation as a new liver-targeted approach to managing type 2 diabetes mellitus (DM). The aim of the present study was to evaluate the inhibitory activity of a panel of 52 structurally related chromone derivatives; namely, flavonoids, 2-styrylchromones, 2-styrylchromone-related derivatives [2-(4-arylbuta-1,3-dien-1-yl)chromones], and 4- and 5-styrylpyrazoles against GP, using in silico and in vitro microanalysis screening systems. Several of the tested compounds showed a potent inhibitory effect. The structure–activity relationship study indicated that for 2-styrylchromones and 2-styrylchromone-related derivatives, the hydroxylations at the A and B rings, and in the flavonoid family, as well as the hydroxylation of the A ring, were determinants for the inhibitory activity. To support the in vitro experimental findings, molecular docking studies were performed, revealing clear hydrogen bonding patterns that favored the inhibitory effects of flavonoids, 2-styrylchromones, and 2-styrylchromone-related derivatives. Interestingly, the potency of the most active compounds increased almost four-fold when the concentration of glucose increased, presenting an IC50 < 10 µM. This effect may reduce the risk of hypoglycemia, a commonly reported side effect of antidiabetic agents. This work contributes with important considerations and provides a better understanding of potential scaffolds for the study of novel GP inhibitors.  相似文献   
110.
目的:目前有关骨髓间充质干细胞向内皮细胞诱导分化的研究较少。本实验分离和培养人骨髓间充质干细胞,用带有VEGF165的质粒转染人骨髓间充质干细胞,探讨血管内皮生长因子对其体外诱导分化的作用。 方法:实验于2005—04/2006—04在吉林大学人兽共患病教育部重点实验室完成。取成人的已排除血液系统肿瘤疾病的新鲜骨髓(自愿提供),采用Percoll梯度分离培养骨髓间充质干细胞,于倒置显微镜下观察细胞形态变化和生长情况。原代细胞培养至增殖接近融合状态时,单克隆培养法分离传代培养,扩增骨髓间充质干细胞。采用流式细胞术检测细胞免疫学表型。在原核细胞大肠杆菌DH5α中复制扩增和提取,纯化、克隆pcDNA3.0-VEGF165质粒。用脂质体转染法转染骨髓间充质干细胞:应用流式细胞术检测诱导后骨髓间充质干细胞免疫学表型变化j并采用免疫荧光染色鉴定转染情况,并设质粒空载和未转染的骨髓间充质干细胞为对照。 结果:人骨髓间充质干细胞原代培养1周后,造血细胞消失,贴壁细胞体积增大,呈现梭形外观,有粗大的细胞突起伸出。2周后细胞融合成单层,梭形突起变长,排列有明显的方向性,细胞排列成旋涡状、网状、辐射状。流式细胞术显示,人骨髓间充质干细胞免疫学表型CD44、CD29阳性,CD34、CD31、CD45阴性。VEGF165诱导骨髓间充质千细胞后CD44表达明显降低,CD31明显升高。免疫荧光染色显示,用FITC标记后的VEGF抗体使细胞显现绿色荧光,用cy3标记的CD31抗体使细胞显现了红色荧光。 结论:转染后的骨髓间充质干细胞细胞表型发生明显转变,CD31表达率明显增高,呈现典型的内皮细胞的表型特征,这说明骨髓间充质干细胞具有向内皮细胞分化的潜能。  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