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   472018篇
  免费   34619篇
  国内免费   13425篇
耳鼻咽喉   6457篇
儿科学   10279篇
妇产科学   8821篇
基础医学   41180篇
口腔科学   11690篇
临床医学   47395篇
内科学   57778篇
皮肤病学   6960篇
神经病学   20384篇
特种医学   13532篇
外国民族医学   184篇
外科学   56018篇
综合类   73377篇
现状与发展   43篇
一般理论   33篇
预防医学   39700篇
眼科学   6087篇
药学   37347篇
  461篇
中国医学   35487篇
肿瘤学   46849篇
  2023年   7470篇
  2022年   13706篇
  2021年   18523篇
  2020年   16996篇
  2019年   22313篇
  2018年   19952篇
  2017年   17296篇
  2016年   15362篇
  2015年   15427篇
  2014年   28406篇
  2013年   28893篇
  2012年   25881篇
  2011年   28533篇
  2010年   23375篇
  2009年   21374篇
  2008年   21032篇
  2007年   21844篇
  2006年   19527篇
  2005年   17106篇
  2004年   13826篇
  2003年   12107篇
  2002年   9778篇
  2001年   8781篇
  2000年   7377篇
  1999年   6284篇
  1998年   5290篇
  1997年   4861篇
  1996年   4181篇
  1995年   3858篇
  1994年   3650篇
  1993年   2828篇
  1992年   2757篇
  1991年   2382篇
  1990年   2117篇
  1989年   1861篇
  1988年   1759篇
  1987年   1512篇
  1986年   1364篇
  1985年   4145篇
  1984年   5107篇
  1983年   3567篇
  1982年   4068篇
  1981年   3775篇
  1980年   3372篇
  1979年   3073篇
  1978年   2675篇
  1977年   2008篇
  1976年   2238篇
  1975年   1664篇
  1974年   1453篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The value of adding simeprevir (SMV) vs placebo (PBO) to peginterferon and ribavirin (PR) for treatment of chronic hepatitis C virus infection was examined using patient‐reported outcomes (PROs); further, concordance of PROs with virology endpoints and adverse events (AEs) was explored. Patients (= 768 SMV/PR,= 393 PBO/PR) rated fatigue (FSS), depressive symptoms (CES‐D) and functional impairment (WPAI: Hepatitis C Productivity, Daily Activity and Absenteeism) at baseline and throughout treatment in three randomised, double‐blind trials comparing the addition of SMV or PBO during initial 12 weeks of PR. PR was administered for 48 weeks (PBO group) and 24/48 weeks (SMV group) using a response‐guided therapy (RGT) approach. Mean PRO scores (except Absenteeism) worsened from baseline to Week 4 to the same extent in both groups but reverted after Week 24 for SMV/PR and only after Week 48 for PBO/PR. Accordingly, there was a significantly lower area under the curve (baseline–Week 60, AUC60) and fewer weeks with clinically important worsening of scores in the SMV/PR group at any time point. Incidences of patients with fatigue and anaemia AEs were similar in both groups, but FSS scores showed that clinically important increases in fatigue lasted a mean of 6.9 weeks longer with PBO/PR (P < 0.001). PRO score subgroup analysis indicated better outcomes for patients who met the criteria for RGT or achieved sustained virological response 12 weeks post‐treatment (SVR12); differences in mean PRO scores associated with fibrosis level were only observed with PBO/PR. Greater efficacy of SMV/PR enabled reduced treatment duration and reduced time with PR‐related AEs without adding to AE severity.  相似文献   
82.
PurposeTo determine if cone-beam CT and digital subtraction angiography analysis of pelvic arterial anatomy has predictive value for radiation exposure and technical success of prostatic artery embolization (PAE).Materials and MethodsThis prospective, nonrandomized, single-center study included 104 consecutive patients with lower urinary tract symptoms secondary to benign prostatic hyperplasia. Cone-beam CT was performed in 160/208 (76.9%) hemipelves to determine prostatic artery (PA) origin. Classification of pelvic arterial tortuosity was possible in 73/104 (70.2%) patients. Learning curves of 2 interventionalists who performed 86.5% of PAEs were analyzed.ResultsTortuosity of pelvic arteries was classified as mild in 25 (34.2%) patients median age 64 years, moderate in 40 (54.8%) patients median age 69 years, and severe in 8 (11.0%) patients median age 70 years (mild vs moderate, P = .002; mild vs severe, P = .019); median fluoroscopy times were 24, 36, and 46 minutes (P = .008, P = .023); median contrast volumes were 105, 122.5, and 142 mL (P = .029, P = .064); and bilateral PAE rates were 84.0%, 77.5%, and 62.5% (P = .437), respectively. PA origin from superior vesical artery was most frequent (27.5%) and showed higher dose area product (median 402.4 vs 218 Gy ∙ cm2, P = .033) and fluoroscopy time (median 42.5 vs 27 min, P = .01) compared with PA origin from obturator artery, which was least frequent. Interventionalist experience revealed significant impact on procedure times (median 159 vs 130 min, P = .006).ConclusionsTortuosity of pelvic arteries was more frequent in older patients and predicted worse technical outcomes of PAE. PA origin from obturator artery was associated with lower dose area product and fluoroscopy time, especially compared with PA origin from superior vesical artery. Interventionalist experience showed significant influence on technical outcome.  相似文献   
83.
陈宏宇  武文 《浙江预防医学》2020,31(10):1232-676
【目的】 值此《中国科技期刊研究》创刊30周年之际,思考科研评价体系的改变给中文科技期刊带来的影响,为中文期刊探寻发展路径。【方法】 结合对中文科技期刊困境的研究,提出应对策略。【结果】 近期国家陆续出台的纠偏评价导向的政策文件,为中文科技期刊既带来了发展机遇,也提出了挑战。【结论】 在重构符合中文科技期刊发展特点的评价体系的基础上,中文科技期刊应明确目标定位,面向国家需求,提升知识服务能力,建立品牌特色。  相似文献   
84.
85.
PurposeThe purpose of this study was to determine whether computed tomography (CT)-based machine learning of radiomics features could help distinguish autoimmune pancreatitis (AIP) from pancreatic ductal adenocarcinoma (PDAC).Materials and MethodsEighty-nine patients with AIP (65 men, 24 women; mean age, 59.7 ± 13.9 [SD] years; range: 21–83 years) and 93 patients with PDAC (68 men, 25 women; mean age, 60.1 ± 12.3 [SD] years; range: 36–86 years) were retrospectively included. All patients had dedicated dual-phase pancreatic protocol CT between 2004 and 2018. Thin-slice images (0.75/0.5 mm thickness/increment) were compared with thick-slices images (3 or 5 mm thickness/increment). Pancreatic regions involved by PDAC or AIP (areas of enlargement, altered enhancement, effacement of pancreatic duct) as well as uninvolved parenchyma were segmented as three-dimensional volumes. Four hundred and thirty-one radiomics features were extracted and a random forest was used to distinguish AIP from PDAC. CT data of 60 AIP and 60 PDAC patients were used for training and those of 29 AIP and 33 PDAC independent patients were used for testing.ResultsThe pancreas was diffusely involved in 37 (37/89; 41.6%) patients with AIP and not diffusely in 52 (52/89; 58.4%) patients. Using machine learning, 95.2% (59/62; 95% confidence interval [CI]: 89.8–100%), 83.9% (52:67; 95% CI: 74.7–93.0%) and 77.4% (48/62; 95% CI: 67.0–87.8%) of the 62 test patients were correctly classified as either having PDAC or AIP with thin-slice venous phase, thin-slice arterial phase, and thick-slice venous phase CT, respectively. Three of the 29 patients with AIP (3/29; 10.3%) were incorrectly classified as having PDAC but all 33 patients with PDAC (33/33; 100%) were correctly classified with thin-slice venous phase with 89.7% sensitivity (26/29; 95% CI: 78.6–100%) and 100% specificity (33/33; 95% CI: 93–100%) for the diagnosis of AIP, 95.2% accuracy (59/62; 95% CI: 89.8–100%) and area under the curve of 0.975 (95% CI: 0.936–1.0).ConclusionsRadiomic features help differentiate AIP from PDAC with an overall accuracy of 95.2%.  相似文献   
86.
Objective: To assess the effect of electroacupuncture(EA) on expression of cytoskeletal proteins from Sertoli cells(SCs) and spermatogenesis in rats with oligozoospermia of insufficiency of Shen(Kidney)essence syndrome(OIKES).Methods: Twenty healthy male Sprague-Dawley rats were randomly assigned to four groups using a random number table: control,tripterygium glycosides(TG) treatment,sham and EA groups(n=5 in each group).A rat model of OIKES was established by oral gavage with TG.The EA group was treated with TG and received EA at Shenshu(BL 23) and Zusanli(ST 36) acupoints for 20 min,once daily for 30 days,while the sham group received EA at identical acupoints with skin penetration without stimulation.After 30 days,the ?nal body weight and coef?cients for the testis and epididymis were calculated and sperm parameters were measured.Immunohistochemical analyses were performed to detect expression of vimentin and α-tubulin in SCs and proliferating cell nuclear antigen(PCNA) immunoreactivity in germ cells.Apoptosis in germ cells was quanti?ed by the transferase biotin-dUTP nick end labeling assay.Results: Compared with the control group,the final body weight and testis/epididymis coefficients of rats in the TG-treated group were not significantly different,but the sperm count and motility were lower(P0.05).Expressions of vimentin and α-tubulin were also signi?cantly weaker(P0.01).The PCNA immunoreactivity of germ cells was decreased(P=0.059),whereas the apoptotic index of germ cells was increased signi?cantly(P0.01).In contrast,EA at BL 23 and ST 36 acupoints signi?cantly improved the ?nal body weight as well as the sperm count,concentration and motility(P0.01 or P0.05).EA increased expression of vimentin and α-tubulin in SCs markedly,and signi?cantly enhanced PCNA immunoreactivity with decreased apoptosis in germ cells(P0.01 or P0.05).Conclusions: EA at BL 23 and ST 36 acupoints has protective effects on spermatogenesis in rats with OIKES.This effect seems to be achieved by attenuating TG-induced disruption of cytoskeletal protein in SCs.  相似文献   
87.
88.
文题释义:股骨头坏死中日友好医院分型的有限元分析:根据李子荣等提出的中日友好医院分型,建立股骨头坏死三维模型,分为 M型(内侧型)、C型(中央型)和 L型(外侧型),其中 L型包括L1型(次外侧型)、L2型(极外侧型)和 L3型(全头型)。通过对建立的模型进行有限元分析,为该分型的保髋治疗提供了一定力学依据,显示外侧柱的存留是精准预防塌陷的重要因素,为进一步实现个体化治疗提供力学基础。 腓骨支撑坏死股骨头保髋手术:是对于早中期股骨头坏死需要保留股骨头患者进行的一种手术方式。首先需对股骨头进行髓芯减压,清除一定坏死骨,空腔填塞松质骨(髂骨为主),打压结实后植入腓骨(异体或自体)支撑,给坏死区的提供力学支撑及生物学修复,预防股骨头进一步坏死及塌陷。 背景:研究报道股骨头坏死的保髋疗效与外侧柱存留密切相关,中日友好医院分型是根据三柱结构确立的,对股骨头塌陷的预测准确性高。 目的:建立股骨头坏死中日友好医院分型各分型仿真的三维有限元模型,通过有限元分析各分型腓骨植入的力学变化,探讨外侧柱存留对保髋疗效的意义,为该分型的塌陷精准预测提供基础。 方法:建立正常股骨头、中日友好医院分型(M型、C型、L1型、L2型、L3型)股骨头坏死及其腓骨植入3组11种三维有限元模型,运用ANSYS软件进行有限元分析计算,观察各组模型的最大应力值、最大位移值及股骨头内部载荷传递模式。 结果与结论:①坏死组位移最大,应变最大,且因坏死分型不同而位移不同,位移变化如下:M型相似文献   
89.
90.
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