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   1386196篇
  免费   104654篇
  国内免费   9765篇
耳鼻咽喉   19172篇
儿科学   43642篇
妇产科学   40039篇
基础医学   199538篇
口腔科学   37309篇
临床医学   122788篇
内科学   267957篇
皮肤病学   27821篇
神经病学   104922篇
特种医学   54063篇
外国民族医学   436篇
外科学   209241篇
综合类   44958篇
现状与发展   25篇
一般理论   305篇
预防医学   99252篇
眼科学   32474篇
药学   109654篇
  112篇
中国医学   8419篇
肿瘤学   78488篇
  2021年   11791篇
  2019年   12015篇
  2018年   15827篇
  2017年   12525篇
  2016年   13425篇
  2015年   16714篇
  2014年   22386篇
  2013年   30288篇
  2012年   42182篇
  2011年   45456篇
  2010年   27014篇
  2009年   24621篇
  2008年   41283篇
  2007年   44207篇
  2006年   44813篇
  2005年   44093篇
  2004年   40698篇
  2003年   39383篇
  2002年   38280篇
  2001年   60837篇
  2000年   62394篇
  1999年   53532篇
  1998年   15557篇
  1997年   14076篇
  1996年   13777篇
  1995年   13700篇
  1994年   12940篇
  1992年   42034篇
  1991年   41326篇
  1990年   40690篇
  1989年   39416篇
  1988年   36709篇
  1987年   35909篇
  1986年   34141篇
  1985年   32518篇
  1984年   24113篇
  1983年   20929篇
  1982年   12415篇
  1979年   22695篇
  1978年   15885篇
  1977年   13720篇
  1976年   12980篇
  1975年   14210篇
  1974年   16710篇
  1973年   16074篇
  1972年   15325篇
  1971年   14244篇
  1970年   13213篇
  1969年   12736篇
  1968年   11977篇
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
61.
This meta-analysis focuses on the accuracy of upgrading to clinically significant prostate cancer (PCa) by multiparametric magnetic resonance imaging-targeted biopsy (MRI-TB) versus systematic biopsy (SB). We searched the Medline, Embase, Cochrane Central Register of Controlled Trials, Web of Science, Scopus, and Literatura Latino Americana em Ciências da Saúde databases through January 2020 for comparative, retrospective/prospective, paired-cohort, and randomized clinical trials with paired comparisons. The population consisted of patients with low-risk PCa in active surveillance with at least 1 index lesion on imaging. We evaluated the quality of evidence by using the Quality Assessment of Diagnostic Accuracy Studies-2 score. Group comparisons considered the differences between the area under the curve summary receiver operating characteristic curve in a 2-tailed method. We also compared the positive predictive value of the best single method (MRI-TB or SB) and the referral study test (combined biopsy, a combination of MRI-TB and SB). The meta-analysis included 6 studies enrolling 741 patients. The pooled sensitivity for the 2 groups was 0.79 (95% confidence interval, 0.74-0.83; I2 = 75%) and 0.67 (95% confidence interval, 0.63-0.74; I2 = 55.4%), respectively. The area under the curve for the MRI-TB and SB groups were 0.99 and 0.92 (P < .001), respectively. The positive predictive value for the MRI-TB and combined biopsy groups were similar. The accumulated evidence suggests better results for MRI-TB compared with SB. Therefore, use of MRI-TB alone may be preferable in patients in active surveillance harboring low-risk PCa.  相似文献   
62.
Herpesvirus entry mediator (HVEM) displays dual signals in T-cell activation according to the ligands and intracytoplasmic effectors it interacts with. High HVEM expression may play an immunosuppressive role in several malignancies. The present study investigated the clinical impact of HVEM on intrahepatic cholangiocarcinoma (ICC), including its prognostic value, and association with clinicopathological features and immune status. The clinical data of 102 consecutive patients with ICC who underwent surgical treatment from January 2012 to December 2017 were collected. The expression of HVEM and different types of tumor-infiltrating lymphocytes (TILs) were investigated in ICC tissue samples by immunohistochemical staining. HVEM expression was detected in the tumor tissues of 92 (90.2%) patients with ICC. Patients with high HVEM expression were more likely to have increased peripheral blood lymphocyte (PBL) concentrations (P=0.031), decreased CEA (P=0.036), low TNM stage (P=0.043) and high frequencies of small-duct histological type (P=0.021) and BAP1 retained expression (P=0.010). Survival analysis showed that high HVEM expression was a favorable independent predictor of overall postoperative survival (P=0.034, hazard ratio=0.486, 95% confidence interval=0.249–0.945). In addition, no significant association of HVEM expression with CD4+ (P=0.512), CD8+ (P=0.750) or CD45RO+ (P=0.078) TILs was identified in the ICC tissues. These results indicate that HVEM may serve as a favorable prognostic marker for ICC. Furthermore, co-stimulatory signals from HVEM may play a dominant role in the progression of ICCs, which can be explained by an increase in the number of PBLs rather than a change in the number of TILs. However, the function of the HVEM network in ICC progression is complex and requires further study.  相似文献   
63.
64.
65.
There have been a number of investigations of the efficacy and safety of etanercept. This study was performed to obtain long-term drug survival data (ie, time to drug discontinuation) for etanercept, and the reasons for its discontinuation. The study population consisted of patients with psoriatic arthritis and psoriasis followed up by our clinic, registered in the Turkish Psoriasis Registry (PSR-TR) and treated with etanercept for at least 4 weeks between January 1, 2005, and January 31, 2020. The efficacy of etanercept was evaluated in terms of the Psoriasis Area and Severity Index (PASI) 75, PASI 90 and PASI 100 response rates at 12, 24, 36, and 48 weeks, and annually thereafter. The behaviors of the patients with respect to the use of etanercept, and the outcomes of those who continued to use it during the COVID-19 pandemic, were also investigated.  相似文献   
66.
67.
IntroductionOrgan-based tube current modulation (OBTCM) is designed for anterior dose reduction in Computed Tomography (CT). The purpose was to assess dose reduction capability in chest CT using three organ dose modulation systems at different kVp settings. Furthermore, noise, diagnostic image quality and tumour detection was assessed.MethodsA Lungman phantom was scanned with and without OBTCM at 80–135/140 kVp using three CT scanners; Canon Aquillion Prime, GE Revolution CT and Siemens Somatom Flash. Thermo-luminescent dosimeters were attached to the phantom surface and all scans were repeated five times. Image noise was measured in three ROIs at the level of the carina. Three observers visually scored the images using a fivestep scale. A Wilcoxon Signed-Rank test was used for statistical analysis of differences.ResultsUsing the GE revolution CT scanner, dose reductions between 1.10 mSv (12%) and 1.56 mSv (24%) (p < 0.01) were found in the anterior segment and no differences posteriorly and laterally. Total dose reductions between 0.64 (8%) and 0.91 mSv (13%) were found across kVp levels (p < 0.00001). Maximum noise increase with OBTCM was 0.8 HU. With the Canon system, anterior dose reductions of 6–10% and total dose reduction of 0.74–0.76 mSv across kVp levels (p < 0.001) were found with a maximum noise increase of 1.1 HU. For the Siemens system, dose increased by 22–51% anteriorly; except at 100 kVp where no dose difference was found. Noise decreased by 1 to 1.5 HU.ConclusionOrgan based tube current modulation is capable of anterior and total dose reduction with minimal loss of image quality in vendors that do not increase posterior dose.Implications for practiceThis research highlights the importance of being familiar with dose reduction technologies.  相似文献   
68.
本研究拟探讨染料木黄酮对前列腺癌细胞LNCaP和CWR22RV1的增殖、迁移和侵袭能力的影响。一、材料与方法1.材料:前列腺癌细胞株LNCaP和CWR22RV1(中国科学院上海生命科学研究院);Genistein(天津科瑞泰科技有限公司);RPMI 1640、胎牛血清(FBS)、胰蛋白酶(美国Gibco公司);E-钙黏蛋白(E-cadherin)、N-钙黏蛋白(N-cadherin)、波形蛋白(Vimentin,Abcam公司);聚氰基丙烯酸正丁酯(BCA)试剂盒、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)上样缓冲液(×5)及蛋白质印迹法(Western blot)试剂盒(上海市碧云天生物公司);2.实验方法:采用噻唑蓝(MTT)实验、划痕实验和Transwell实验检测Genistein对细胞增殖、迁移及侵袭能力的影响。采用Western blot检测E-cadherin、N-cadherin、Vimentin、CD44和Oct-4的表达水平。  相似文献   
69.
70.
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