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   6941篇
  免费   765篇
  国内免费   349篇
耳鼻咽喉   40篇
儿科学   64篇
妇产科学   172篇
基础医学   1039篇
口腔科学   162篇
临床医学   518篇
内科学   930篇
皮肤病学   106篇
神经病学   251篇
特种医学   156篇
外国民族医学   9篇
外科学   649篇
综合类   923篇
现状与发展   1篇
预防医学   69篇
眼科学   232篇
药学   746篇
中国医学   323篇
肿瘤学   1665篇
  2024年   17篇
  2023年   94篇
  2022年   121篇
  2021年   192篇
  2020年   184篇
  2019年   162篇
  2018年   192篇
  2017年   212篇
  2016年   240篇
  2015年   361篇
  2014年   343篇
  2013年   748篇
  2012年   369篇
  2011年   452篇
  2010年   410篇
  2009年   386篇
  2008年   399篇
  2007年   406篇
  2006年   414篇
  2005年   380篇
  2004年   362篇
  2003年   336篇
  2002年   296篇
  2001年   226篇
  2000年   180篇
  1999年   160篇
  1998年   89篇
  1997年   79篇
  1996年   52篇
  1995年   45篇
  1994年   27篇
  1993年   22篇
  1992年   14篇
  1991年   10篇
  1990年   17篇
  1989年   10篇
  1988年   12篇
  1987年   4篇
  1986年   6篇
  1985年   7篇
  1984年   2篇
  1983年   3篇
  1982年   1篇
  1981年   1篇
  1980年   3篇
  1979年   4篇
  1977年   3篇
  1976年   1篇
  1975年   1篇
排序方式: 共有8055条查询结果,搜索用时 15 毫秒
1.
目的 研究miR-200、miR-155及血管新生因子与原因不明复发性流产(unexplained recurrent spontaneousabortion,URSA)的相关性分析。 方法 选择2015年3月—2018年1月在青岛市妇女儿童医院妇产科就诊的URSA患者作为URSA组、要求终止妊娠的正常早孕患者作为对照组,检测绒毛组织中微小RNA(microRNA, miR)miR-200、miR-155、血管内皮生长因子(vascular endothelial growth factor,VEGF)、可溶性FMS样酪氨酸激酶1(soluble FMS like tyrosine kinase-1,sFlt-1)的表达量及血清中VEGF、sFlt-1的含量,对miR-200、miR-155靶向结合VEGF、sFlt-1进行生物信息学分析。 结果 URSA组的绒毛组织中miR-200(1.78±0.32 vs. 0.91±0.15)、sFlt-1(1.87±0.35 vs. 1.06±0.21)的相对表达量及血清中sFlt-1的含量[(12.39±2.31)ng/ml vs. (6.51±0.95)ng/ml]均高于对照组,差异有统计学意义(均P<0.05)。绒毛组织中miR-155相对表达量(0.60±0.10 vs. 0.93±0.16)、VEGF mRNA相对表达量(0.59±0.09 vs. 1.02±0.16)及蛋白表达量(0.62±0.07 vs. 1.04±0.18)、血清中VEGF的含量[(601.25±94.39)ng/ml vs. (935.12±132.47)ng/ml]低于对照组,差异有统计学意义(均P<0.05);URSA组患者绒毛组织中miR-200的表达量与血清中VEGF的含量、绒毛组织中VEGF的表达量均呈负相关,绒毛组织中miR-155的表达量与血清中sFlt-1的含量和绒毛组织中sFlt-1的表达量均呈负相关;miR-200、miR-155分别靶向结合VEGF、sFlt-1基因的3’UTR。 结论 miR-200表达增多、miR-155表达减少与URSA发生有关,miR-200靶向VEGF、miR-155靶向sFlt-1是介导该过程的可能机制。  相似文献   
2.
ObjectiveMultiple treatment options for acetabular fractures in geriatric patients exist. However, no large-scale studies have reported the outcomes of acute total hip arthroplasty (THA) in this patient population. We systematically evaluated all available evidence to characterize clinical outcomes, complications, and revisions of acute THA for acetabular fractures in geriatric patients.MethodsMeta-analysis of 21 studies of 430 acetabular fractures with mean follow-up of 44 months (range, 17−97 months). Two independent researchers searched and evaluated the databases of Ovid, Embase, and United States National Library of Medicine using a Boolean search string up to December 2019. Population demographics and complications, including presence of heterotopic ossification (HO), dislocation, infection, revision rate, neurological deficits, and venous thromboembolic event (VTE), were recorded and analyzed.ResultsWeighted mean Harris Hip Score was 83.3 points, and 20% of the patients had reported complications. The most common complication was HO, with a rate of 19.5%. Brooker grade III and IV HO rates were lower at 6.8%. Hip dislocation occurred at a rate of 6.1%, 4.1% of patients developed VTE, deep infection occurred in 3.8%, and neurological complications occurred in 1.9%. Although the revision rate was described in most studies, we were unable to perform a survival analysis because the time to each revision was described in only a few studies. The revision rate was 4.3%.ConclusionsAcute THA is a viable option for treatment of acetabular fracture and can result in acceptable clinical outcomes and survivorship rates in older patients but with an associated complication rate of approximately 20%. Considering the limited treatment options, THA might be a viable alternative for appropriately selected patients.  相似文献   
3.
4.
A case of angiolipoma occurring in the buccal mucosa of a 69-year-old male is described. The patient had noticed a painless mass in his buccal mucosa for 2 years. The surgically removed tumor, measuring 9 mm in diameter, was mainly located in the submucosal layer with focal expansion into the muscle layer. Histologically, the tumor was well-demarcated and composed of proliferations of mature fat cells and fibrous connective tissue containing many small blood vessels, which were evenly distributed. There was diffuse infiltration of a large number of mast cells, which were immunopositive for vascular endothelial growth factor (VEGF) especially around blood vessels, suggesting that VEGF produced by mast cells in angiolipomas plays an important role in the vascular proliferation in this particular tumor.  相似文献   
5.
瘤性体液中肿瘤血管生长因子的提取和检测   总被引:1,自引:0,他引:1  
《肿瘤防治杂志》2005,12(17):1289-1291
  相似文献   
6.
食管鳞癌中肿瘤微血管密度的临床意义   总被引:1,自引:0,他引:1  
范虹  曾亮  王群 《复旦学报(医学版)》2004,31(2):162-164,168,F005
目的 研究分析食管癌组织中肿瘤微血管密度 (MVD)的临床意义。方法 采用免疫组化的方法检测4 5例食管鳞癌根治性切除术后的肿瘤组织中的肿瘤微血管密度 ,应用SPSS统计软件分析肿瘤MVD与食管鳞癌临床病理参数及预后的关系。结果 本组病例中 ,肿瘤MVD平均值为 15 .5 8,中位值为 15。MVD水平与食管癌的肿瘤局部浸润程度、区域淋巴结转移及TNM分期有关 (P <0 .0 5 )。多血管型 (MVD >15 )病例的术后生存率低于少血管型 (MVD≤ 15 )病例 (P =0 .0 2 78)。Cox比例风险模型证实MVD水平是食管癌根治性切除病人预后的独立预测指标。结论 食管鳞癌的血管新生与癌肿进展程度有关 ,高MVD的食管鳞癌患者术后生存率明显低于低MVD的患者 ,其MVD水平可独立用于预测食管癌根治性切除病人的预后  相似文献   
7.
BACKGROUND: Although it is clear that dissemination via the blood system involves angiogenesis, it is uncertain whether tumors also induce lymphangiogenesis or simply invade existing peritumoral vessels. The purpose of this study was to elucidate changes in tumor blood and lymph vessels in cases involving the invasion of squamous cell carcinoma in the oral cavity, and its significance. Blood and lymph vessels densities in tongue carcinomas induced in hamsters were investigated. METHODS: Tongue cancer was induced by abrading the right margin of the tongue of each hamster with an endodontic barbed broach and subsequently applying 1.0% 9,10-dimenthl-1,2-benzanthracene (DMBA) dissolved in acetone, three times a week, at the same site. Fresh frozen sections were prepared and blood vessels stained blue by perfusion with Coomassie Brilliant Blue and lymph vessels stained brown for 5'-nucleotidase. The effects on the blood vessels and lymph vessels were observed. RESULTS: The results showed that blood and lymph vessel densities were greater in the advanced carcinoma tissues than in normal tissue. These were compared in terms of the mode of cancer invasion. As tumor invasion progressed, the blood vessel density decreased but lymph vessel density tended to be higher in high-degree tumor invasion than in low-degree tumor invasion. The expression of vascular endothelial growth factor-C was seen more frequently as tumor invasion progressed. CONCLUSIONS: The present findings indicated that angiogenesis and lymphangiogenesis are affected by cancerous invasion.  相似文献   
8.
Summary.  Vascular development requires correct interactions among endothelial cells, pericytes and surrounding cells. These interactions involve many cell adhesion interactions, including cell–matrix interactions both with basement membranes and with surrounding extracellular matrices. Investigations of the contributions of these various interactions in vascular development and angiogenesis have been rather uneven and incomplete over the past 10–15 years. There has been considerable concentration on a few receptors, matrix proteins and proteolytic fragments with the goal of finding means to control angiogenesis. Many other potential contributors have received much less attention. Even for those molecules that have been subject to intensive investigation, our knowledge is incomplete. This review will survey the spectrum of extracellular matrix (ECM) proteins and cell–matrix adhesion receptors (particularly integrins) that are likely to contribute to angiogenesis and discuss what is known and not known about the roles of each of them.  相似文献   
9.
人膀胱癌T24细胞及其SCID小鼠移植瘤组织中KDR的表达   总被引:1,自引:1,他引:0  
目的 检测KDR在人膀胱癌T24细胞及其SCID小鼠移植瘤组织中的表达。方法 常规培养T24细胞,建立荷人膀胱癌移植瘤SCID小鼠动物模型,使用抗KDR单克隆抗体,通过免疫荧光、免疫组化检测KDR在T24细胞及瘤体组织上的表达;结果 KDR在T24细胞及瘤体组织中均呈阳性表达。结论 本研究结果为进一步研究抗KDR单抗在荷T24细胞移植瘤动物体内分布及对瘤体生长的抑制效应奠定了实验基础。  相似文献   
10.
目的探讨人类胚胎脑动脉分叉部中层平滑肌细胞(smoothmusclecell,SMC)的构筑发育过程及特点。方法收集12~28周人类胚胎共17例,胎龄各相差1周,男女不限。对不同胎龄胚胎Willis环周围的脑动脉分叉部行三维组织切片,观察中层SMC的构筑发育过程及其有无先天缺陷。结果胎儿Willis环周各脑动脉中层SMC在1.1~9.0层之间;70.6%的胎儿在脑动脉个别分叉部发现中层SMC缺陷;所取标本的30.3%发现中层SMC缺陷。结论胎儿脑动脉中层SMC随胎龄增长而增多,但28周内不超过9.0层;本研究发现胎儿脑动脉分叉部存在先天性SMC缺陷,这将有助于对脑动脉瘤病因假说的理解和验证。  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