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   119369篇
  免费   11788篇
  国内免费   7602篇
耳鼻咽喉   979篇
儿科学   1864篇
妇产科学   1388篇
基础医学   12276篇
口腔科学   2292篇
临床医学   14949篇
内科学   15841篇
皮肤病学   1180篇
神经病学   5330篇
特种医学   4415篇
外国民族医学   32篇
外科学   11491篇
综合类   23587篇
现状与发展   21篇
一般理论   12篇
预防医学   9861篇
眼科学   2617篇
药学   13048篇
  158篇
中国医学   8757篇
肿瘤学   8661篇
  2025年   30篇
  2024年   1735篇
  2023年   2303篇
  2022年   4506篇
  2021年   5595篇
  2020年   4583篇
  2019年   3375篇
  2018年   3549篇
  2017年   3596篇
  2016年   3207篇
  2015年   5101篇
  2014年   6180篇
  2013年   6408篇
  2012年   9612篇
  2011年   10117篇
  2010年   7574篇
  2009年   6248篇
  2008年   7556篇
  2007年   7132篇
  2006年   6614篇
  2005年   5851篇
  2004年   4235篇
  2003年   3698篇
  2002年   3128篇
  2001年   2606篇
  2000年   2504篇
  1999年   2202篇
  1998年   1311篇
  1997年   1279篇
  1996年   1014篇
  1995年   987篇
  1994年   804篇
  1993年   498篇
  1992年   571篇
  1991年   518篇
  1990年   441篇
  1989年   392篇
  1988年   305篇
  1987年   314篇
  1986年   244篇
  1985年   197篇
  1984年   129篇
  1983年   91篇
  1982年   66篇
  1981年   47篇
  1980年   34篇
  1979年   44篇
  1978年   18篇
  1973年   17篇
  1966年   19篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
<正>笔者在局解教学过程中发现一具标本存在右侧腹壁下动脉缺如的情况。为积累资料及为临床提供参考,现报道如下:该标本系老年男性,体质良好。左侧腹壁诸层结构正常,腹壁下动脉完好。右侧腹壁层次尚可,右侧腹直肌下部肌质较薄,内侧越过白线与左侧腹直肌融合,但右侧腹壁下动静脉缺如(图1A),也未见异位腹壁下动脉分支。此外可见右侧腹  相似文献   
22.
In the last several years, multiple‐shape memory liquid crystalline networks (LCNs) have received more and more attention due to the basic theoretical research on them and their wide potential applications. In this article, a novel main‐chain/side‐chain liquid crystalline monomer and its corresponding polymer networks based on the thiol‐ene click reaction are reported. Properties of the synthesized liquid crystalline monomer are well studied with nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectra, differential scanning calorimetry (DSC), and polarized optical microscopy (POM). The as‐prepared free‐standing LCN films are investigated well by FTIR, DSC, POM, and X‐ray diffraction (XRD), which show them having good liquid crystalline properties. Tensile test and dynamical mechanical analysis (DMA) results indicate the LCN films have excellent thermal mechanical properties. By adjusting the crosslinking densities, LCN films exhibit two thermal transition temperatures (Tg and TNI) that can be utilized to trigger the triple‐shape memory behaviors. The cyclic thermal mechanical analysis conducted by DMA reveals that LCN films exhibit good triple‐shape memory properties with high‐shape fixity ratio (Rf (S1→S2) is 99.2% and Rf (S2→S3) is 99.3%) and shape recovery ratio (Rr (S3→S2) is 92.4% and Rr (S2→S1) is 98.5%).  相似文献   
23.
24.
目的:研究银杏二萜内酯葡胺注射液在人尿液中的主要代谢产物及其代谢途径。方法:3名受试者静脉滴注银杏二萜内酯葡胺注射液后收集0~6 h的尿样,分别按酸化和不酸化样品处理后,以液相色谱-串联质谱法(LC-MS/MS)对样品进行分析。采用ACE C_(18)-AR色谱柱(4.6 mm×150 mm,3μm),酸性HPLC条件流动相Ⅰ为乙腈-0.4%甲酸铵水溶液(p H3.2)梯度洗脱,中性HPLC条件流动相Ⅱ为乙腈-水梯度洗脱,流速0.7 m L·min~(-1)。通过比较空白尿样和给药后尿样的总离子流和提取离子流色谱图以及各个色谱峰的保留时间、准分子离子和二级碎片离子,分析银杏内酯A(GA),银杏内酯B(GB)和银杏内酯K(GK)在人体内可能的代谢产物。结果:除原型药外,共鉴定了12个代谢产物,其中GA相关的代谢产物有6个,包括5个Ⅰ相和1个Ⅱ相代谢产物;GB相关的有4个,包括1个Ⅰ相和3个Ⅱ相代谢产物;GK相关的有2个,包括1个Ⅰ相和1个Ⅱ相代谢产物。结论:GA在人体内主要的代谢途径为羟基化和内酯环水解,并可进一步共价结合成硫酸酯;GB主要的代谢途径为羟基化和内酯环水解,并可进一步共价结合成硫酸酯、葡萄糖醛酸苷或谷胱甘肽结合物;GK在人体内主要的代谢途径为甲基化葡萄糖醛酸结合反应。  相似文献   
25.
Variations in the dental anatomy are found in all teeth. Knowledge of these variations, particularly concerning the location and treatment of all canals, is very important for the success of the endodontic therapy. The purpose of this study is to present a clinical case of a maxillary second molar with three palatal canals, two mesio-buccal and one disto-buccal canal. This report serves to remind clinicians that such anatomical variations should be taken into account during endodontic treatment of the maxillary molars.  相似文献   
26.
Background: To our knowledge, prospective studies (matched for sex, smoking, and diabetes) that investigated the influence of compliance in the progression of periodontitis and tooth loss in periodontal maintenance therapy (PMT) programs were not previously reported. Methods: A total of 58 regular complier (RC) and 58 erratic complier (EC) individuals were recruited from a prospective cohort with 238 patients under PMT and matched by sex, diabetes, and smoking habits. A full‐mouth periodontal examination that included bleeding on probing (BOP), probing depths (PDs), clinical attachment levels, and number of teeth were determined at all PMT visits during a 3‐year interval. The influence of variables of interest was tested through multivariate logistic regression. Results: The progression of periodontitis and tooth loss was significantly lower among RC compared to EC patients. A higher progression of periodontitis was observed among EC patients who smoked. The final logistic model for the progression of periodontitis in the RC group included smoking (odds ratio [OR]: 4.2) and >30% of sites with BOP (OR: 2.8), and the final logistic model for the progression of periodontitis in the EC group included smoking (OR: 7.3), >30% of sites with BOP (OR: 3.2), PDs of 4 to 6 mm in 10% of sites (OR: 3.5), diabetes (OR: 1.9), and number of lost teeth (OR: 3.1). Conclusions: RC patients presented a lower progression of periodontitis and tooth loss compared to EC patients. This result highlighted the influence of the pattern of compliance in maintaining a good periodontal status. Moreover, important risk variables such as smoking and diabetes influenced the periodontal status and should be considered when determining the risk profile and interval time for PMT visits.  相似文献   
27.
This study evaluated the effect of the adhesive application mode and fiber post translucency on the push-out bond strength to dentin. Bovine roots were endodontically treated, and 10 roots were used for each adhesive application mode: PB (Prime&Bond 2.1), PB + SC (Self-cure activator), PB + SBM (Scotchbond Multi-purpose adhesive system), BB (Brush&Bond), BB + CAT (chemical catalyst), and BB + SBM. The translucent Light-Post and Aestheti-Post were cemented. The roots/cemented posts were transversally sectioned to originate three thirds (cervical, middle, and apical). The push-out test was performed, and the failure mode of fractured specimens was analyzed. There was no difference between the fiber posts. For PB and BB, the use of hydrophobic adhesive resin SBM increased post bond strength. The use of SC and CAT catalyst did not affect the push-out bond strength values. The apical third presented the lowest bond strengths.  相似文献   
28.
29.
目的:观察小鼠釉质发育过程中成釉器中间层细胞的增殖、凋亡和其组织非特异性碱性磷酸酶(tissue nonspecific alkaline phosphatase,TNSALP)的表达,探讨中间层在釉质形成过程中的可能作用.方法:取出生后1、3、5、7、9、11、15d的BALB/c小鼠56只,解剖分离含下颌第一磨牙区的下颌骨,脱钙,制片,HE染色进行牙釉质发育情况的组织学观察,分别采用原位末端标记法(TUNEL法)、SP免疫组织化学技术、PV二步法观察中间层细胞的凋亡及检测Bcl-2、增殖细胞核抗原(proliferating cell nuclear antigen,PCNA),并对TNSALP进行组织学定位.通过Image-pro plus 6.0图像分析软件.对图像进行半定量分析.采用SPSS13.0软件包进行t检验、单因素方差分析及SNK-q检验.结果:出生后1d.中间层细胞增殖细胞核抗原由比成釉细胞表达高的强阳性表达逐渐降低;至7d时,其表达为阴性,而且中间层细胞随釉质的发育逐渐凋亡.中间层细胞先于成釉细胞表达TNSALP,出生后5d时即呈现强阳性染色,而后其表达又逐步减弱;成釉细胞7d时开始出现阳性,且呈逐渐增强趋势.结论:中间层细胞的增殖和凋亡及其TNSALP的表达与成釉细胞具有相关性,提示中间层细胞有可能参与成釉细胞的分化及釉质形成.  相似文献   
30.
作者曾对238例口腔鳞癌术后应用中药“参阳”方的疗效进行前瞻性的研究,本文继续对已生存4~8年的56例病员门诊随访结果进行分析.结果是生存情况:7年生存期原治疗组高于原对照组12.5%,原治疗组30例均健在,而原对照组中的26例,2例带瘤生存,1例死亡;T细胞亚群测定中,复发死亡者的CD8值均升高,CD4/CD8比值均下降;中医辨证中,正常者及肾气虚者的例数以治疗组为多,而阴虚与气阴两虚者,治疗组低于对照组;由上提示:经“参阳”方治疗者有较好的远期疗效.  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