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   34869篇
  免费   2735篇
  国内免费   645篇
耳鼻咽喉   659篇
儿科学   576篇
妇产科学   703篇
基础医学   5052篇
口腔科学   515篇
临床医学   3021篇
内科学   7774篇
皮肤病学   1021篇
神经病学   2445篇
特种医学   1715篇
外国民族医学   1篇
外科学   4677篇
综合类   834篇
现状与发展   1篇
一般理论   16篇
预防医学   1537篇
眼科学   1012篇
药学   3023篇
中国医学   476篇
肿瘤学   3191篇
  2023年   247篇
  2022年   200篇
  2021年   1143篇
  2020年   639篇
  2019年   972篇
  2018年   1093篇
  2017年   780篇
  2016年   1027篇
  2015年   1415篇
  2014年   1650篇
  2013年   1860篇
  2012年   2728篇
  2011年   2819篇
  2010年   1696篇
  2009年   1495篇
  2008年   2088篇
  2007年   1985篇
  2006年   1832篇
  2005年   1723篇
  2004年   1406篇
  2003年   1379篇
  2002年   1236篇
  2001年   827篇
  2000年   732篇
  1999年   699篇
  1998年   304篇
  1997年   260篇
  1996年   242篇
  1995年   205篇
  1994年   172篇
  1993年   114篇
  1992年   344篇
  1991年   250篇
  1990年   292篇
  1989年   280篇
  1988年   262篇
  1987年   218篇
  1986年   190篇
  1985年   179篇
  1984年   147篇
  1983年   117篇
  1982年   82篇
  1981年   72篇
  1980年   72篇
  1979年   125篇
  1978年   84篇
  1977年   70篇
  1975年   61篇
  1974年   56篇
  1972年   51篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Barrett's esophagus (BE) is the precursor to esophageal adenocarcinoma (EAC). Progression to cancer typically occurs in a stepwise fashion through worsening dysplasia and ultimately, invasive neoplasia. Established EAC with deep involvement of the esophageal wall and/or metastatic disease is invariably associated with poor long-term survival rates. This guides the rationale of surveillance of Barrett’s in an attempt to treat lesions at an earlier, and potentially curative stage. The last two decades have seen a paradigm shift in management of Barrett’s with rapid expansion in the role of endoscopic eradication therapy (EET) for management of dysplastic and early neoplastic BE, and there have been substantial changes to international consensus guidelines for management of early BE based on evolving evidence. This review aims to assist the physician in the therapeutic decision-making process with patients by comprehensive review and summary of literature surrounding natural history of Barrett’s by histological stage, and the effectiveness of interventions in attenuating the risk posed by its natural history. Key findings were as follows. Non-dysplastic Barrett’s is associated with extremely low risk of progression, and interventions cannot be justified. The annual risk of cancer progression in low grade dysplasia is between 1%-3%; EET can be offered though evidence for its benefit remains confined to highly select settings. High-grade dysplasia progresses to cancer in 5%-10% per year; EET is similarly effective to and less morbid than surgery and should be routinely performed for this indication. Risk of nodal metastases in intramucosal cancer is 2%-4%, which is comparable to operative mortality rate, so EET is usually preferred. Submucosal cancer is associated with nodal metastases in 14%-41% hence surgery remains standard of care, except for select situations.  相似文献   
2.
Background: Considering the poor prognosis of non-small cell lung cancer (NSCLC), the objective of this study was to examine the potential of plasma-derived vesicles as a source of lung cancer-specific proteins. Extracellular vesicle (EV) cargos are specific to the source cells, hence they have the potential of being a source of cancer-specific proteins.  Methods: The proteins differently expressed in cancer were determined and derived from EVs isolated from the plasma of NSCLC patients at the National Lung Hospital. To this end, purification was done using gel filtration chromatography and ultracentrifugation. In addition, nano liquid chromatography mass spectrometry (LC–MS/MS) was used for analyzing. Results: Fifty-seven EV-derived proteins related to NSCLC were highlighted in this research. Some of them have not been addressed before, such as EEF1A1 (elongation factor 1-α1), KPNB1 (Importin subunit beta 1), SRC (proto-oncogene tyrosine-protein kinase) and ACTC1 (actin, alpha cardiac muscle 1). This list was further confirmed through a comparison with ExoCarta and Vesiclepedia. Conclusion: This study is the first work to show the involvement of several novel proteins of small EV (EEF1A1, KPNB1, SRC, and ACTC1) in the progression of NSCLC. The results suggested that they could serve as novel biomarkers for non-small cell lung cancer in the future.  相似文献   
3.
4.
Direct peroral cholangioscopy (POC) using an ultra‐slim upper endoscope is one modality of POC for intraductal endoscopic evaluation and treatment of the bile duct. Choledochoduodenostomy (CDS) is one modality of biliary bypass surgery that provides a new route to the bile duct. We carried out direct POC using an ultra‐slim upper endoscope without the use of accessories in 10 patients (four sump syndromes, three bile duct strictures and three intrahepatic duct stones) previously undergoing surgical CDS. Direct POC was successful in all patients. The use of an intraductal balloon catheter was required in one patient for advancement of the endoscope into the bile duct. Distal bile ducts with sump syndromes were cleared using baskets and water irrigation under direct POC. Cholangiocarcinoma was diagnosed in one patient with hilar bile duct stricture after cholangioscopic evaluation and a targeting forceps biopsy under direct POC. Intrahepatic duct stones were successfully extracted after intraductal fragmentation under direct POC. Oozing bleeding occurred during intraductal lithotripsy but stopped spontaneously. Direct POC using an ultra‐slim upper endoscope without the assistance of accessories can easily be carried out in patients undergoing CDS.  相似文献   
5.
6.
ABSTRACT

Purpose

Work-related eye injuries have been reported with a variety of epidemiologic and clinical characteristics. We aimed to identify epidemiologic characteristics of work-related eye injuries and risk factors associated with severe injury in a large metropolitan city.  相似文献   
7.
8.
Psoriasis is a chronic, inflammatory, immune‐mediated disease. Approximately 30% of patients have disease onset before age 18 years. Psoriasis in children and adolescents may be difficult to control, with subsequent poor quality of life and psychosocial consequences. We describe the case of a 12‐year‐old boy with severe, refractory, chronic plaque psoriasis for 6 years. Various therapeutic regimens including different topical corticosteroids, topical vitamin D analogs, phototherapy, photochemotherapy, systemic therapy with methotrexate, cyclosporin, and combination therapies showed only partial or transient responses with frequent relapses. Because anti‐interleukin‐12/23 agents have been successfully used in adults with psoriasis, ustekinumab was initiated and our patient showed a rapid, excellent, sustained response. No recurrence or flares have been observed after 33 months of follow‐up. This case illustrates that ustekinumab may be an effective and safe therapeutic option in adolescents with psoriasis.  相似文献   
9.
10.
Genetic and epigenetic alterations importantly contribute to the pathogenesis of lung cancer. In the study, we measured the frequency and distribution of molecular abnormalities of EGFR as well as the aberrant promoter methylations of BRCA1, MGMT, MLH1, and RASSF1A in Vietnamese lung adenocarcinomas. We investigated the association between genetic and epigenetic alteration, and between each abnormality with clinicopathologic parameters. Somatic EGFR mutation that was found in 49/139 (35.3%) lung adenocarcinomas showed a significant association with young age, female gender, and non-smokers. EGFR overexpression was identified in 82 tumors (59.0%) and statistical relationships with EGFR or BRCA1 methylation but not EGFR mutation. In addition, EGFR, BRCA1, MGMT, MLH1, and RASSF1A methylations were found in 33 (23.7%), 41 (29.5%), 46 (33.1%), 28 (20.1%), and 41 (29.5%) cases of a total of 139 lung adenocarcinomas, respectively. The RASSF1A methylation was found to be linked to the smoking habit. Methylations in MGMT and RASSF1A were also found to correlate with metastasis status. Furthermore, the distribution of EGFR mutation and that of BRCA1, MGMT or RASSF1A methylation were significantly exclusive in lung adenocarcinomas. The main finding of our study demonstrate that epigenetic abnormalities might play a critical role for the lung tumorigenesis in patients with smoking history and metastasis, and partly affect the predictive value of EGFR mutations through blocking expression due to promoter EGFR hypermethylation. Mutually exclusive distribution of genetic and epigenetic alterations reflects differently biological characteristics in the etiology of lung adenocarcinomas.  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