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   67404篇
  免费   7020篇
  国内免费   4599篇
耳鼻咽喉   531篇
儿科学   622篇
妇产科学   607篇
基础医学   7748篇
口腔科学   1261篇
临床医学   8899篇
内科学   10384篇
皮肤病学   639篇
神经病学   3810篇
特种医学   2399篇
外国民族医学   52篇
外科学   6852篇
综合类   11870篇
现状与发展   22篇
一般理论   5篇
预防医学   4597篇
眼科学   1999篇
药学   7154篇
  72篇
中国医学   3683篇
肿瘤学   5817篇
  2025年   25篇
  2024年   1032篇
  2023年   1569篇
  2022年   2971篇
  2021年   3675篇
  2020年   2927篇
  2019年   2522篇
  2018年   2354篇
  2017年   2245篇
  2016年   2073篇
  2015年   3143篇
  2014年   3868篇
  2013年   3266篇
  2012年   5029篇
  2011年   5387篇
  2010年   3223篇
  2009年   2499篇
  2008年   3428篇
  2007年   3297篇
  2006年   3238篇
  2005年   3165篇
  2004年   2074篇
  2003年   2031篇
  2002年   1712篇
  2001年   1438篇
  2000年   1473篇
  1999年   1679篇
  1998年   1029篇
  1997年   1009篇
  1996年   724篇
  1995年   675篇
  1994年   660篇
  1993年   402篇
  1992年   574篇
  1991年   435篇
  1990年   400篇
  1989年   332篇
  1988年   326篇
  1987年   260篇
  1986年   221篇
  1985年   181篇
  1984年   99篇
  1983年   60篇
  1982年   45篇
  1981年   41篇
  1980年   19篇
  1979年   42篇
  1978年   15篇
  1977年   14篇
  1936年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Amelogenesis imperfecta (AI) is a heterogeneous group of inherited defects in dental enamel formation. The malformed enamel can be unusually thin, soft, rough and stained. The strict definition of AI includes only those cases where enamel defects occur in the absence of other symptoms. Currently, there are seven candidate genes for AI: amelogenin, enamelin, ameloblastin, tuftelin, distal-less homeobox 3, enamelysin, and kallikrein 4. To identify sequence variations in AI candidate genes in patients with isolated enamel defects, and to deduce the likely effect of each sequence variation on protein expression and structure, families with isolated enamel defects were recruited. The coding exons and nearby intron sequences were amplified for each of the AI candidate genes by using genomic DNA from the proband as template. The amplification products for the proband were sequenced. Then, other family members were tested to determine their genotype with respect to each sequence variation. All subjects received an oral examination, and intraoral photographs and dental radiographs were obtained. Out of 24 families with isolated enamel defects, only six disease-causing mutations were identified in the AI candidate genes. This finding suggests that many additional genes potentially contribute to the etiology of AI.  相似文献   
22.
The aim of this investigation was to study the remodelling of cartilage in the mandibular condyle following disc displacement (DD) of the temporomandibular joint (TMJ). Forty adult Japanese white rabbits were used in this study. The right joints of 28 of the 40 rabbits had their discs surgically displaced. Four of the 28 were killed at 4 days or 1, 2, 4, 6, 8 and 12 weeks after surgery. The messenger RNA (mRNA) expression levels of aggrecan and type II collagen in cartilages were measured using in situ hybridization techniques. Results showed that aggrecan mRNA expression reduced in the first week after DD. The expression began to recover after 4 weeks and reached a normal level after 6 weeks. Type II collagen mRNA expression reduced from 4 weeks and the expression recovered after 8 weeks. This suggests that the chondrocyte reacting to the displacement of the TMJ disc, alters its matrix gene expression patterns and it is may be the cause of the shape changes of TMJ after DD.  相似文献   
23.
24.

Objective

To investigate the expression of antigen processing-1 (Tap-1) and Tapasin in oral squamous cell carcinoma (OSCC), and observe the immune response against OSCC by use of IFN-γ-antigen induced dendritic cells (DCs) in vitro and in vivo.

Design

Expression of Tap-1 and Tapasin in different cell lines was analysed. CAL27 cells were treated with IFN-γ. Antigen from the treated cells was presented by DCs. Pulsed DC was then co-cultivated with CD8+ T lymphocyte to induce antigen specific cytotoxic lymphocytes (CTLs). The immune response elicited by CTLs against OSCC was observed.

Results

A significant lower expression of Tap-1 and Tapasin was observed in OSCC cell lines. IFN-γ exerted time-dependent effect for increasing the expression of these genes. Antigen from the treated CAL27 cells was presented by DCs. CTLs were induced and generated a strong immune response in vitro and in vivo.

Conclusions

Tap-1 and Tapasin were downregulated in OSCC. IFN-γ increased the expression of these genes. Use of IFN-γ-antigen induced DCs could induce stronger immune response in vitro and in vivo.  相似文献   
25.
26.
27.

Introduction

This study examined the identity of the microbiome of deep dentinal caries and its correlation with the inflammation status of caries-induced pulpitis.

Methods

Seventy-five cases were diagnosed based on the American Association of Endodontics's diagnostic criteria and divided into 4 groups: normal pulp with deep caries (NP; n = 13), reversible pulpitis with only cold-evoked pain (CRP; n = 17), reversible pulpitis with both cold/heat-evoked pain (CHRP; n = 24), and symptomatic irreversible pulpitis (SIP; n = 21). Samples were sequenced by 16S rDNA. Alpha and beta diversity were determined. Linear discriminant analysis effect size (LEfSe) analysis was used to detect intergroup differences, and receiver operating characteristic (ROC) curves were generated to assess the role of the caries microbiome in caries-induced pulpitis.

Results

The 16S rDNA sequencing yielded 9100 operational taxonomic units. Lactobacillus had the highest relative abundance at the genus level among the 4 groups. There were significant differences in the distribution of the microbiome among the groups. In an alpha diversity analysis, species richness differed between the CRP group and the other groups. In a beta diversity analysis, the distribution of microorganisms in the SIP group was significantly different from those in the other 3 groups. LEfSe analysis indicated substantial differences in the microbiome among the groups, and the areas under the ROC curves (AUC) were all high (AUC: 0.734–0.952).

Conclusions

Characterization of the caries microbiome has the potential to become an auxiliary method for the diagnosis of pulpitis. This finding may prompt new research on diagnostic strategies for caries-induced pulpitis.  相似文献   
28.
A study was performed on 91 second-grade students from the Los Angeles Unified School District to test the effects of xylitol chewing gum on Streptococcus mutans in the saliva. Saliva was collected from students and tested for the first time using the new University of California, Los Angeles, monoclonal antibody testing method. Students found to have moderate or high levels of salivary S. mutans were administered four tablets/day of xylitol gum for three weeks. The levels of S. mutans in the saliva of children in the high caries index subgroup decreased by 61.7 percent. Xylitol can be dispensed in a public school setting by school nurses and can be a very safe, efficient and inexpensive preventative measure for children at high risk for dental caries.  相似文献   
29.
A new internal distraction device, comprising a square-bodied bow, a transport plate, a traction mechanism, and two stabilisers, was developed to allow transportation of bone around an arc. Eight adult goats were studied. A curved mandibulectomy 3cm long was made on the mandibular angle. The distractor was implanted to restore the defect. The bone was distracted at a rate of 1mm per day after a 5-day latent period. Distraction lasted 25 to 32 days. Curvilinear distraction was successful in six of the eight goats. After consolidation periods of four or eight weeks, smooth curved bone masses were restored in the distracted areas. Radiographically, there was considerable bone density in the distraction area and opaque columns streamed in the direction of distraction. Histological examination showed membranous bony regeneration in the restored bone. These results suggest that restoration of curved bone defects using the new internal transport distraction device was feasible in goats.  相似文献   
30.
牙种植数字化全景X线片失真率的临床评价   总被引:4,自引:0,他引:4  
目的:了解数字化全景片失真率的大小以及在临床效果评价中的指导意义。方法:对术前使用统一直径钢珠的放射模板56个修复病例162个种植体拍摄数字化全景X线片,应用Cliniview5.1分析软件对各部位钢珠进行测量3次,取均值。了解拍摄后影像中钢珠的变化情况。结果:采用数字化全景X线片技术可观察到上下颌骨不同区域钢珠失真率与标准钢珠直径差异很小,失真率范围为0.2% ̄2%,不同区域钢珠测量值之间有明显差异(P〈0.05〉):下颌前牙区与下颌双尖牙区、下颌前牙区与下颌磨牙区、下颌双尖牙区与上颌磨牙区、上颌磨牙区与下颌磨牙区钢珠测量值之间存在显著性差异。结论:数字化全景X线片对拟种植部位骨量进行评估可得出准确的数据。尽管不同区域钢珠测量值之间存在差异,但并不影响其测量值应用于临床的准确性。  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