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   380299篇
  免费   29792篇
  国内免费   12792篇
耳鼻咽喉   3125篇
儿科学   8697篇
妇产科学   6892篇
基础医学   48122篇
口腔科学   7412篇
临床医学   30265篇
内科学   55080篇
皮肤病学   6019篇
神经病学   27082篇
特种医学   11370篇
外国民族医学   53篇
外科学   33661篇
综合类   53871篇
现状与发展   54篇
一般理论   8篇
预防医学   28602篇
眼科学   7899篇
药学   47283篇
  105篇
中国医学   20586篇
肿瘤学   26697篇
  2024年   621篇
  2023年   4563篇
  2022年   8077篇
  2021年   14102篇
  2020年   11926篇
  2019年   12278篇
  2018年   12282篇
  2017年   12971篇
  2016年   13127篇
  2015年   13095篇
  2014年   18567篇
  2013年   24650篇
  2012年   20335篇
  2011年   23654篇
  2010年   17764篇
  2009年   17311篇
  2008年   18906篇
  2007年   19742篇
  2006年   18097篇
  2005年   16381篇
  2004年   14114篇
  2003年   12708篇
  2002年   11114篇
  2001年   10335篇
  2000年   9142篇
  1999年   7450篇
  1998年   6267篇
  1997年   5948篇
  1996年   5134篇
  1995年   4224篇
  1994年   3767篇
  1993年   3142篇
  1992年   2848篇
  1991年   2603篇
  1990年   2274篇
  1989年   1853篇
  1988年   1654篇
  1987年   1466篇
  1986年   1347篇
  1985年   2438篇
  1984年   2346篇
  1983年   1782篇
  1982年   1977篇
  1981年   1719篇
  1980年   1445篇
  1979年   1201篇
  1978年   851篇
  1977年   705篇
  1976年   729篇
  1975年   553篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
71.
72.
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   
73.
This article was designed to provide a pediatric cardiac computed tomography angiography (CCTA) expert panel consensus based on opinions of experts of the Société Française d’Imagerie Cardiaque et Vasculaire diagnostique et interventionnelle (SFICV) and of the Filiale de Cardiologie Pédiatrique Congénitale (FCPC). This expert panel consensus includes recommendations for indications, patient preparation, CTA radiation dose reduction techniques, and post-processing techniques. The consensus was based on data from available literature (original papers, reviews and guidelines) and on opinions of a group of specialists with extensive experience in the use of CT imaging in congenital heart disease. In order to reach high potential and avoid pitfalls, CCTA in children with congenital heart disease requires training and experience. Moreover, pediatric cardiac CCTA protocols should be standardized to acquire optimal images in this population with the lowest radiation dose possible to prevent unnecessary radiation exposure. We also provided a suggested structured report and a list of acquisition protocols and technical parameters in relation to specific vendors.  相似文献   
74.
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   
75.
76.
目的 探讨腹腔镜下子宫双侧动脉阻断术联合清宫术治疗剖宫产瘢痕妊娠疗效及对内分泌的影响.方法 选择2011年1月至2015年12月剖宫产瘢痕妊娠患者57例,其中A组32例患者给予超声引导下清宫术治疗,B组25例患者给予腹腔镜下子宫双侧动脉阻断术联合清宫术治疗,比较两组患者出血量、住院时间、月经复潮时间、术后人绒毛膜促性腺激素(hCG)降至正常时间,并发症情况及术前(T0)、术后第1d(T1)、第3d(T2)神经内分泌激素水平.结果 ①B组患者出血量低于A组,住院时间、月经复潮时间短于A组,比较差异有统计学意义(t出血量=31.85,k院时间=9.36,t月经复t潮时间=16.37,均P<0.05);②B组患者并发症发生率为8.00%,低于A组的15.63%,比较差异有统计学意义(x2=9.35,P<0.05);③B组T1、T2血清COR、β-EP、GLU水平低于A组(CORF交互=17.67,β-EPF交互=132.36,6LUF交互=155.38,均P<0.05).结论 腹腔镜下子宫双侧动脉阻断术联合清宫术治疗剖宫产瘢痕妊娠微创优势明显,安全性高,对内分泌影响较轻.  相似文献   
77.
78.
BackgroundIn the field of transplantation, inducing immune tolerance in recipients is of great importance. Blocking co-stimulatory molecule using anti-CD28 antibody could induce tolerance in a rat kidney transplantation model. Myeloid-derived suppressor cells (MDSCs) reveals strong immune suppressive abilities in kidney transplantation. Here we analyzed key genes of MDSCs leading to transplant tolerance in this model.MethodsMicroarray data of rat gene expression profiles under accession number GSE28545 in the Gene Expression Omnibus (GEO) database were analyzed. Running the LIMMA package in R language, the differentially expressed genes (DEGs) were found. Enrichment analysis of the DEGs was conducted in the Database for Annotation, Visualization and Integrated Discovery (DAVID) database to explore gene ontology (GO) annotation and their Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Their protein-protein interactions (PPIs) were provided by STRING database and was visualized in Cytoscape. Hub genes were carried out by CytoHubba.ResultsThree hundred and thirty-eight DEGs were exported, including 27 upregulated and 311 downregulated genes. The functions and KEGG pathways of the DEGs were assessed and the PPI network was constructed based on the string interactions of the DEGs. The network was visualized in Cytoscape; the entire PPI network consisted of 192 nodes and 469 edges. Zap70, Cdc42, Stat1, Stat4, Ccl5 and Cxcr3 were among the hub genes.ConclusionsThese key genes, corresponding proteins and their functions may provide valuable background for both basic and clinical research and could be the direction of future studies in immune tolerance, especially those examining immunocyte-induced tolerance.  相似文献   
79.
80.
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