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   3265篇
  免费   226篇
  国内免费   45篇
耳鼻咽喉   39篇
儿科学   86篇
妇产科学   92篇
基础医学   416篇
口腔科学   134篇
临床医学   277篇
内科学   564篇
皮肤病学   55篇
神经病学   234篇
特种医学   89篇
外科学   443篇
综合类   176篇
预防医学   323篇
眼科学   69篇
药学   297篇
  1篇
中国医学   62篇
肿瘤学   179篇
  2023年   28篇
  2022年   55篇
  2021年   87篇
  2020年   62篇
  2019年   90篇
  2018年   90篇
  2017年   98篇
  2016年   114篇
  2015年   93篇
  2014年   135篇
  2013年   154篇
  2012年   243篇
  2011年   262篇
  2010年   125篇
  2009年   117篇
  2008年   185篇
  2007年   183篇
  2006年   203篇
  2005年   198篇
  2004年   149篇
  2003年   125篇
  2002年   118篇
  2001年   83篇
  2000年   77篇
  1999年   52篇
  1998年   18篇
  1997年   20篇
  1996年   21篇
  1995年   16篇
  1994年   12篇
  1993年   13篇
  1992年   14篇
  1991年   20篇
  1990年   23篇
  1989年   28篇
  1988年   22篇
  1987年   10篇
  1986年   19篇
  1985年   26篇
  1984年   13篇
  1980年   7篇
  1979年   13篇
  1977年   7篇
  1976年   7篇
  1975年   9篇
  1974年   9篇
  1971年   9篇
  1969年   12篇
  1967年   7篇
  1966年   6篇
排序方式: 共有3536条查询结果,搜索用时 0 毫秒
71.
Background: Craniometric variation in humans reflects different genetic and environmental influences. Long-term climatic adaptation is less likely to show an impact on size and shape variation in a small local area than at the global level.

Aim: The aim of this work was to assess the contribution of the particular environmental factors to body height and craniofacial variability in a small geographic area of Croatia.

Subjects and methods: A total of 632 subjects, aged 18–21, participated in the survey. Body height, head length, head breadth, head height, head circumference, cephalic index, morphological face height, face breadth, and facial index were analysed regarding geographic, climatic and dietary conditions in different regions of the country, and correlated with the specific climatic variables (cumulative multiyear sunshine duration, cumulative multiyear average precipitation, multiyear average air temperatures) and calcium concentrations in drinking water. Significant differences between groups classified according to geographic, climatic or dietary affiliation, and the impact of the environmental predictors on the variation in the investigated traits were assessed using multiple forward stepwise regression analyses.

Results: Higher body height measures in both sexes were significantly correlated with Mediterranean diet type. Mediterranean diet type also contributed to higher head length and head circumference measures in females. Cephalic index values correlated to geographic regions in both sexes, showing an increase from southern to eastern Croatia. In the same direction, head length significantly decreased in males and head breadth increased in females. Mediterranean climate was associated with higher and narrower faces in females. The analysis of the particular climatic variables did not reveal a significant influence on body height in either sex. Concurrently, climatic features influenced all craniofacial traits in females and only head length and facial index in males. Mediterranean climate, characterized by higher average sunshine duration, higher average precipitation and higher average air temperatures, was associated with longer, higher and narrower skulls, higher head circumference, lower cephalic index, and higher and narrower faces (lower facial index). Calcium concentrations in drinking water did not correlate significantly with any dependent variable.

Conclusion: A significant effect of environmental factors on body height and craniofacial variability was found in Croatian young adult population. This effect was more pronounced in females, revealing sex-specific craniofacial differentiation. However, the impact of environment was low and may explain only 1.0–7.32% variation of the investigated traits.  相似文献   
72.
73.
74.
Background: A novel member of the interleukin (IL)‐12 family, IL‐35 is an important inhibitory cytokine released by regulatory T cells. The aim of this study is to evaluate gingival crevicular fluid (GCF), saliva, and plasma levels of IL‐35 in periodontal disease and health. Methods: Samples of GCF, whole saliva, and plasma were obtained from systemically healthy, non‐smoking individuals with gingivitis (n = 20) or chronic periodontitis (CP) (n = 20) and periodontally healthy individuals (n = 20). Full‐mouth clinical periodontal measurements, including probing depth (PD), bleeding on probing, gingival index, and plaque index (PI), were also recorded. Enzyme‐linked immunosorbent assay was used to determine IL‐35 levels in the samples. Data were tested statistically by analysis of variance and Pearson rank correlation test. Results: All clinical parameters were significantly higher in the CP group than the healthy and gingivitis groups (P <0.001). The GCF total amount of IL‐35 was significantly higher in the CP group than the other groups (P = 0.04), whereas the GCF concentration of IL‐35 was significantly higher in the healthy group than the other groups (P = 0.002). There were significant differences among the study groups in terms of salivary IL‐35 level (P <0.001), with the highest level observed in the healthy group and the lowest in the CP group. There was no statistical difference between groups in plasma levels of IL‐35 (P >0.05). There was a positive correlation between GCF total amount of IL‐35 and PD (r = 0.338, P = 0.03) and PI (r = 0.374, P = 0.005) parameters. Conclusions: IL‐35 could have an important role in suppressing periodontal inflammation and maintaining periodontal health. Additional studies are required to evaluate its role in periodontal diseases.  相似文献   
75.
76.
BACKGROUND/AIMS: Combined hepatocellular-cholangiocarcinoma (HCC-CC) show dual hepatocellular and biliary epithelial differentiation. To better understand the relations between cholangiocarcinoma (CC), HCC-CC and hepatocellular carcinoma (HCC), we screened for genetic alterations. METHODS: A series of nine CC, 15 HCC-CC and three separated HCC and CC lesions ('collision tumors') were screened for loss of heterozygosity (LOH) using 400 microsatellite markers and for p53 and beta-catenin mutations. A comparison with a previously characterized series of 137 HCC was performed. RESULTS: In six cases of CC and HCC-CC, we identified TP53 gene mutations. A CTNNB1/beta-catenin was identified in two patients presenting collision tumors, but no mutations were found in CC or in HCC-CC. A high level of chromosome instability in both CC and HCC-CC was found. Recurrent specific LOH were identified at 3p and 14q in more than 50% of the CC and the HCC-CC cases, whereas these chromosomal regions were deleted in less than 10% of the HCC cases (P<10(-5)). Minimal common regions of deletion (MCRD) were defined at 3p24-p14 and 14q24-q32, respectively. CONCLUSIONS: These results suggest that combined HCC-CC are genetically closer to CC than HCC and common carcinogenesis pathways may be altered in HCC-CC and CC.  相似文献   
77.

PURPOSE

The aim of this study was to evaluate whether the push-out bond strength varies between oval and circular fiber posts, and to examine the effect on the resin cement thicknesses around the posts.

MATERIALS AND METHODS

Eighteen mandibular premolar roots were separated into two groups for oval and circular fiber posts systems. Post spaces were prepared and fiber posts were luted to the post spaces. Roots were cut horizontally to produce 1-mm-thick specimens. Resin cement thicknesses were determined with a metallographic optical microscope and push-out tests were done.

RESULTS

No significant differences were observed in terms of push-out bond strength between the oval and circular fiber posts (P>.05) The resin cement thicknesses of the oval posts were greater than those of the circular posts group in the coronal, middle and apical specimens (P<.05).

CONCLUSION

In the light of these results, it can be stated that resin cement thickness does not affect the push-out bond strength.  相似文献   
78.
79.
80.
The phonation process of vertebrates is influenced by the material characteristics of the participating structures, ranging from molecular to macroscopic dimensions. Good animal models for phonation research are still lacking. Due to easy availability and relatively simple structure, the syrinx of birds might serve as a good animal model for this purpose. Our aim was therefore to determine structural features of the syrinx and obtain insights into its mucus layer characteristics. Epithelium and glands were analyzed using histological, histochemical, and immunohistochemical methods and conclusions were drawn on the use of the syrinx as a model for phonation research by comparing the epithelium and its mucus characteristics to human laryngeal secretions. Ten adult partridges were analyzed. The tympanum of the syrinx developed from the last two tracheal cartilages, whereas the caudal part of the syrinx was formed from eight pieces of bronchial cartilages. The tracheal and bronchial epithelia and the pessulus of the syrinx were lined by pseudo‐stratified columnar epithelium in which goblet cells and intraepithelial glands were localized. Collagen fibers were distributed in the lamina propria of all parts of the syringeal mucosa. Elastic fibers in the membranes of the syrinx showed evident distribution. All glandular epithelial cells and goblet cells were positive for neutral, acidic and carboxylated mucins were dominant in particular. Epithelium and glands revealed positive reactivity with antibodies to the mucins MUC1, MUC2, and MUC5AC. Of these, MUC2 and MUC5AC were dominant. The syrinx of partridge can serve as a good ex vivo model for phonation research. Anat Rec, 298:602–617, 2015. © 2014 Wiley Periodicals, Inc.  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