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   3878篇
  免费   373篇
  国内免费   289篇
耳鼻咽喉   33篇
儿科学   42篇
妇产科学   65篇
基础医学   824篇
口腔科学   52篇
临床医学   209篇
内科学   843篇
皮肤病学   38篇
神经病学   259篇
特种医学   54篇
外科学   331篇
综合类   698篇
预防医学   153篇
眼科学   26篇
药学   321篇
  1篇
中国医学   87篇
肿瘤学   504篇
  2024年   3篇
  2023年   33篇
  2022年   97篇
  2021年   184篇
  2020年   158篇
  2019年   116篇
  2018年   100篇
  2017年   128篇
  2016年   190篇
  2015年   211篇
  2014年   340篇
  2013年   321篇
  2012年   296篇
  2011年   273篇
  2010年   220篇
  2009年   190篇
  2008年   171篇
  2007年   219篇
  2006年   189篇
  2005年   175篇
  2004年   160篇
  2003年   160篇
  2002年   113篇
  2001年   94篇
  2000年   95篇
  1999年   88篇
  1998年   46篇
  1997年   36篇
  1996年   37篇
  1995年   31篇
  1994年   18篇
  1993年   5篇
  1992年   9篇
  1991年   2篇
  1990年   9篇
  1989年   4篇
  1988年   5篇
  1987年   2篇
  1986年   1篇
  1985年   4篇
  1984年   4篇
  1981年   1篇
  1977年   1篇
  1974年   1篇
排序方式: 共有4540条查询结果,搜索用时 15 毫秒
181.
目的 实施母婴分离产妇母乳采集的循证实践并探索其对泌乳的影响。方法 应用循证护理的方法获取最佳证据,以基于证据的持续质量改进模式为理论框架,于2018年5月—12月,按照证据获取、现状审查、证据引入和效果评价4个阶段将循证实践应用于母婴分离产妇,比较循证实践应用前后产妇母乳采集的依从性和泌乳量等指标的变化。结果 循证实践应用了12条证据。循证实践后,产妇母乳采集的依从性提高,送母乳至新生儿科的产妇人数比例提高,产妇开始送母乳时间提前,产后1周内产妇泌乳总量增加。结论 通过循证护理对母婴分离产妇进行管理,可有效规范产妇母乳采集行为,促进成功泌乳及提高泌乳量,可为母婴分离状态下母乳喂养的管理提供参考。  相似文献   
182.
Although the roles of IL-17 family members during inflammation have been extensively studied in mammals, their knowledge in lower vertebrates is limited. In particular, the biological activities of fish IL-17 and their functional roles are largely unknown. In this study, we cloned grass carp IL-17D (gcIL-17D) and found that its putative protein possessed the conserved features of IL-17 family members. Tissue distribution analysis showed that gcIL-17D was preferentially expressed in the mucosal tissues, including skin, gill and intestine. Subsequently, the involvement of gcIL-17D in inflammatory response was demonstrated by examining the expression profiles of gcIL-17D in head kidney and head kidney leukocytes following in vivo bacterial infection and in vitro LPS treatment, respectively. Furthermore, recombinant gcIL-17D (rgcIL-17D) was prepared in grass carp kidney cells and was able to promote the gene expression of some pro-inflammatory cytokines (IL-1β, TNF-α and CXCL-8) in grass carp primary head kidney cells, revealing gcIL-17D can function as a pro-inflammatory cytokine. Moreover, rgcIL-17D appeared to activate NF-κB signaling by modulating the phosphorylation of IκBα and up-regulated CXCL-8 mRNA expression possibly through NF-κB pathway. Our data shed new light on the functional role of teleost IL-17D in inflammatory response.  相似文献   
183.
184.

Objective

The aim of this study was to investigate the expression patterns of CEACAM5 in non-neoplastic and neoplastic gastric lesions, as well as its application in the differential diagnosis and its relationship with tumor progression.

Methods

CEACAM5 expression was detected by immunohistochemical staining in the serial sections of the gastric neoplastic and non-neoplastic lesions. The impacts of CEACAM5 expression patterns on tumor progression were evaluated by statistics, the clinical and pathological data included sex, age, tumor extension, lymph node involvement and tumor staging.

Results

There was no CEACAM5 expression in normal gastric epithelial cells. In hyperplastic polyps, CEACAM5 was expressed with apical membranous staining in the hyperplastic and prolonged gastric pit adjacent to the surface. Intestinal metaplasia (IM) expressed CEACAM5 mainly with membranous pattern, and some cases showed membranous staining mixed with cytoplasmic staining. GIN expressed CEACAM5 mainly with membranous staining, but the mixed staining of cytoplasmic and membranous patterns increased, and especially in the high grade GIN, cytoplasmic staining of CEACAM5 began to occur. Compared with IM and GIN, CEACAM5 expression patterns of hyperplastic polyp showed a significant difference (P = 0.000). IM, low grade GIN and the whole GIN showed no significant difference in CEACAM5 expression patterns (P = 0.355), but IM and high grade GIN showed a significant difference (P = 0.027). There was a significant difference between low and high grade GIN (P = 0.002). GIN and well-differentiated carcinomas showed no significant difference (P = 0.070), but low grade GIN and well differentiated carcinomas showed a significant difference (P = 0.006). In gastric adenocarcinomas, CEACAM5 expression patterns showed a significant difference in tumor grading (P = 0.010) and Laurén classification (P = 0.001). In histological grading, well differentiated carcinomas showed more membranous staining than moderately and poorly differentiated, and more cytoplasmic CEACAM5 staining was detected in moderately and poorly differentiated carcinomas. Similar to that, in Laurén classification, intestinal carcinomas showed more membranous staining, and diffuse carcinomas showed more cytoplasmic staining. Moreover, CEACAM5 expression patterns showed a significant difference in tumor extension (P = 0.012), lymph node involvement (P = 0.015) and tumor staging (P = 0.002), suggesting that CEACAM5 should be involved in tumor progression. In advanced carcinomas, CEACAM5 was expressed with more cytoplasmic staining regardless of the histological classification.

Conclusion

CEACAM5 had different expression patterns in gastric non-neoplastic and neoplastic lesions. The CEACAM5 expression patterns were associated with tumor progression. Membranous staining of CEACAM5 might be a marker of premalignancy in gastric lesions, and cytoplasmic CEACAM5 might enhance tumor invasion and migration and be an evaluated marker for progressive and advanced gastric cancer. Also, it might be useful for the differential diagnosis of gastric premalignant lesions.  相似文献   
185.
Lung cancer is a leading cause of cancer deaths worldwide. Development of lung cancer is associated with exposure to carcinogens such as tobacco smoke and some environmental factors. The incidence of lung cancer increases with age, particularly after age 60. It was estimated that less than 2% of all lung cancer cases occurred in patients younger than 45; therefore, this type of tumor can be considered as an aging-related disease. MicroRNAs (miRNAs) are small non-coding RNA molecules capable of regulating expression of over 50% of protein-coding genes. miRNAs were shown to play an extremely important role in cell functioning, affecting all biological processes, as well as development of various diseases. Expression profiles of miRNAs are known to be altered in cancer, including lung cancer, and also exhibit changes during aging. These RNA molecules are stable in tissue sections and blood and reflect tumor origin, histotype, and stage, which make them candidate diagnostic and prognostic biomarkers. miRNA mimetics or inhibitors can be delivered into a cell, with possible therapeutic implications. Here, we review the results obtained during the last several years that demonstrate the aging-related regulation of miRNAs expression, in association with their role in lung cancer initiation, progression, and resistance to anticancer therapy, as well as the possibility to use miRNAs as predictive biomarkers for treatment response.  相似文献   
186.

Objective

The present study was designed to investigate (1) whether the non-human primate would be an appropriate animal model for the study of spontaneous periodontitis and its association with metabolic syndrome (MetS), and (2) whether microRNAs (miRNAs) play roles in the co-development of metabolic disorders and periodontitis.

Design

Rhesus monkeys (aged 12–29 years) with or without MetS were analyzed for the prevalence of periodontitis. The potential mechanisms underlying the association between MetS and periodontitis were explored using miRNA profiling of the gingival tissues from the MetS monkey groups with or without periodontitis as well as the age-matched controls.

Results

Among the 57 rhesus monkeys examined, 18 were diagnosed with periodontitis according to the inclusion criteria, with an overall prevalence of 31.6%. Moreover, the prevalence of periodontitis was 8.3% in the control group, 18.2% in the at-risk group, and 44.1% in the MetS group. The C-reactive protein level was doubled in the MetS periodontitis group, compared to the non-periodontitis sub-groups. Most importantly, only 3 miRNAs were confirmed to be differentially expressed between the MetS periodontitis and non-periodontitis subgroups while other miRNAs showed similar expression profiles.

Conclusions

The results indicate that the monkey with MetS is an ideal model for studies of spontaneous periodontitis and its association with MetS. miRNA profiling using this unique model showed that miRNAs play roles in the co-development of MetS and periodontitis.  相似文献   
187.
目的 对克氏综合征(Klinefelter syndrome)患者进行基因表达谱分析,探讨其基因差异表达与临床表型之间的关系.方法 采用第二代高通量测序方法对7例克氏综合征患者和7例对照男性外周血全基因组mRNA进行深度测序,运用定量RT-PCR方法对30例克氏综合征患者及30例对照男性进行验证.结果 测序结果根据FDR≤0.001和| log2 Ratio≥1 |的标准,两组比较存在差异表达基因216个,差异具有统计学意义.其中X染色体基因9个,占4%,与X染色体失活相关的XIST差异表达最明显;常染色体基因207个,占96%,其中NR4A3、ZKSCAN4、HBEGF、EREG、AREG、NR4A2、CCR5差异表达明显.NR4A3主要.与2型糖尿病有关,HBEGF主要参与促性腺激素分泌过程.Y染色体不存在显著差异表达基因.结论 克氏综合征患者不仅多余X染色体基因差异表达,还有大量常染色体基因差异表达,这可能是克氏综合征临床表型多样化的原因.  相似文献   
188.
This study is to investigate the expression of miR-21 in nasopharyngeal carcinoma (NPC) cells, and the effect of miR-21 in the biological behavior and expression of B-cell lymphoma 2 (BCL2) in NPC cells. Paired NPC and adjacent non-tumor tissues were obtained from 53 patients who underwent primary surgical resection of NPC tissues. Luciferase reporter assay was performed to test whether BCL2 is a direct target of miR-21. Methylthiazolyl blue tetrazolium assay and colony assay were used to evaluate the effect of miR-21 on NPC cell proliferation. Transwell and wound-healing assays were carried out to test the effect of low expression of miR-21 on cancer cell migration and invasion. QRT-PCR and Western blotting were used to measure the levels of mRNA and protein expression, respectively. Tumor tissues showed a positive correlation between the levels of miR-21 and BCL2 protein expression. Cells transfected with miR-21 inhibitor healed slower compared the control (P < 0.05). In addition, cell migration was notably inhibited by the down-regulation of miR-21 in vitro (P < 0.05). The reduction in miR-21 expression showed a remarkable effect on the biological behavior of NPC cell clone formation (P < 0.05). Low expression of miR-21 by transfection with miRNA expression plasmid led to a decrease in BCL2 expression, which was accompanied by reduced migration and proliferation of the cancer cells. Our results demonstrated that miR-21 inhibitor down-regulated BCL2 expression level, suggesting that BCL2 might be a target gene for the initiation and development of NPC cells.  相似文献   
189.
190.
抗磷脂抗体是一类能与磷脂或磷脂结合蛋白结合的自身免疫性抗体,与血栓形成、不良孕产史密切相关。抗磷脂抗体中高滴度阳性的患者易有子痫前期等不良妊娠结局。子痫前期发生于妊娠期,可导致全身多脏器的损伤,严重危及母儿生命和健康。子痫前期的发病机制目前还不是很清楚,研究提示抗磷脂抗体可能通过诱导氧化应激,促进血管内炎症等作用参与子痫前期的发病;对于抗磷脂抗体阳性的患者,早期发现和早期干预对获得良好的妊娠结局至关重要。  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