全文获取类型
收费全文 | 251563篇 |
免费 | 24124篇 |
国内免费 | 10033篇 |
专业分类
耳鼻咽喉 | 1361篇 |
儿科学 | 5718篇 |
妇产科学 | 3402篇 |
基础医学 | 46939篇 |
口腔科学 | 4367篇 |
临床医学 | 16906篇 |
内科学 | 46995篇 |
皮肤病学 | 4187篇 |
神经病学 | 17770篇 |
特种医学 | 4694篇 |
外国民族医学 | 61篇 |
外科学 | 17587篇 |
综合类 | 33304篇 |
现状与发展 | 47篇 |
预防医学 | 13696篇 |
眼科学 | 2627篇 |
药学 | 32528篇 |
38篇 | |
中国医学 | 9780篇 |
肿瘤学 | 23713篇 |
出版年
2023年 | 3452篇 |
2022年 | 4750篇 |
2021年 | 8952篇 |
2020年 | 8472篇 |
2019年 | 9751篇 |
2018年 | 9241篇 |
2017年 | 9146篇 |
2016年 | 9287篇 |
2015年 | 10944篇 |
2014年 | 15775篇 |
2013年 | 17404篇 |
2012年 | 16275篇 |
2011年 | 18813篇 |
2010年 | 15873篇 |
2009年 | 15027篇 |
2008年 | 14371篇 |
2007年 | 13195篇 |
2006年 | 11926篇 |
2005年 | 10179篇 |
2004年 | 8763篇 |
2003年 | 7491篇 |
2002年 | 5884篇 |
2001年 | 5063篇 |
2000年 | 4084篇 |
1999年 | 3505篇 |
1998年 | 2753篇 |
1997年 | 2548篇 |
1996年 | 2081篇 |
1995年 | 2180篇 |
1994年 | 1902篇 |
1993年 | 1585篇 |
1992年 | 1379篇 |
1991年 | 1206篇 |
1990年 | 1010篇 |
1989年 | 868篇 |
1988年 | 743篇 |
1987年 | 610篇 |
1986年 | 591篇 |
1985年 | 1192篇 |
1984年 | 1250篇 |
1983年 | 917篇 |
1982年 | 1001篇 |
1981年 | 797篇 |
1980年 | 681篇 |
1979年 | 605篇 |
1978年 | 474篇 |
1977年 | 381篇 |
1976年 | 378篇 |
1975年 | 287篇 |
1974年 | 235篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
991.
Theodore M. Brasky Roberta M. Ray Sandi L. Navarro Jeannette M. Schenk Alison M. Newton Marian L. Neuhouser 《International journal of cancer. Journal international du cancer》2020,147(5):1374-1384
We and others have reported associations between B vitamins principally involved in one-carbon metabolism and increased lung cancer risk; however, results for women have been inconsistent. Here we report on the association of supplemental vitamins B6, folic acid and B12 intake and lung cancer risk using data from the Women's Health Initiative (WHI) study of postmenopausal women. Between 1993 and 1998, 161,808 women were recruited to participate in the WHI at 40 clinical centers in the US. After exclusions, 159,232 women were available for analysis and followed prospectively for an average of 18.3 years. Among them, 3,836 incident lung cancer cases were diagnosed. At baseline, supplemental B vitamins from multivitamins, vitamin mixtures and individual supplements were assessed. Adjusted Cox regression models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for associations between supplemental B vitamin intake and lung cancer risk. Relative to no intake, women who took ≥50 mg/day of vitamin B6 had 16% (HR 0.84, 95% CI: 0.71–0.99) reduced lung cancer risk. Associations did not differ significantly by smoking status or lung cancer histology. Intakes of folic acid and vitamin B12 were not associated with risk. There is a need for replication of our findings from other large, prospective studies with similar high-quality measurement of supplement intakes before any recommendations can be made at present on B6 supplementation for lung cancer prevention in women. 相似文献
992.
目的探讨中药方剂四君子汤对脾胃虚弱症型消化性溃疡患者肠道菌群变化、环氧化酶(COX-1、COX-2)及前列腺素E2表达水平的影响。方法从2017年1月-2018年12月收治的消化性溃疡患者中按年龄组、性别、溃疡类型1∶1匹配后,随机分配于试验组与对照组(试验组与对照组各240名患者)。其中,对照组患者给予思密达治疗,试验组使用思密达协同四君子汤,分别治疗8周。比较治疗前后2组患者的治疗效果、肠道微生态变化、环氧化酶及前列腺素E2水平表达情况。结果治疗后,试验组的阳性与阴性杆菌数减少,阳性球菌数增多,且阳性球菌与阴性球菌数量均高于对照组。而对照组的阳性、阴性杆菌与阴性球菌均显著减少(P<0.05);2组的COX-1、COX-2、PGE2表达水平均增高(P<0.05),且中药组显著高于对照组(P<0.05)。结论在思密达基础上加用四君子汤治疗脾胃虚弱症型消化性溃疡可有效调节其胃肠道菌群平衡、增强对胃黏膜的覆盖保护作用。 相似文献
993.
目的:观察银杏叶注射液对麻醉引起的认知功能障碍的影响。方法:将75只大鼠随机分为正常对照组、模型组、银杏叶组、抑制剂组、激动剂组,每组15只。银杏叶组、抑制剂组、激动剂组从麻醉前3 d腹腔注射银杏叶注射液(2 mL/kg),1次/d,连续给药3 d;抑制剂组在麻醉前腹腔注射EX527(5 mg/kg);激动剂组在麻醉前腹腔注射SRT1720(200 mg/kg)。水迷宫观察认知功能程度,观察大鼠脑组织神经元形态学变化,透射电镜观察脑组织组织超微结构,检测Iba-1、IL-6、IL-8、TNF-α、SOD、MDA、SIRT1、NF-κB、IκB-α、Bcl-2、Bax、Caspase-3指标变化。结果:与模型组、抑制剂组比较,银杏叶组和激动剂组大鼠逃避潜伏期缩短、穿越平台次数增多、脑组织神经细胞形态改善,突触数量增多,SIRT1、IκB-α、Bcl-2、SOD表达升高,IκB-α、Bax、Caspase-3、IL-6、IL-8、TNF-α、MDA表达降低(P<0.05);与银杏叶组比较,激动剂组的上述情况均较优(P<0.05);与模型组比较,抑制剂组的上述情况均较优(P<0.05)。结论:银杏叶注射液改善麻醉引起的认知障碍,其机制之一可能通过SIRT1/NF-κB通路介导。 相似文献
994.
目的:检测NFATc1在乳腺癌患者癌及癌旁组织的表达,并探讨其表达对乳腺癌细胞增殖和凋亡的影响及机制。方法:收集于我院就诊的39例乳腺癌患者癌及癌旁组织,采用RT-PCR技术、免疫印迹及免疫组化染色技术检测NFATc1在乳腺癌组织及癌旁组织中的表达状况。利用小干扰RNA(siRNA)构建NFATc1稳定敲除的MCF7及MDA-MB-231细胞系。利用CCK-8试剂盒及克隆形成实验检测NFATc1敲除对乳腺癌细胞增殖的影响,同时利用Ki67染色检测对照组和NFATc1敲除组乳腺癌细胞中Ki67阳性细胞的比例。此外,采用流式细胞学技术检测NFATc1基因敲除对乳腺癌细胞凋亡的影响,最后利用免疫印迹技术分析各组细胞RhoA/ROCK信号通路的表达状况。结果:NFATc1在乳腺癌患者癌组织中的mRNA及蛋白表达显著增高(P<0.05)。流式细胞学结果表明NFATc1 siRNA干预能够显著促进两组乳腺癌细胞系的凋亡(P<0.05)。此外,Ki67染色、CCK-8实验及克隆形成实验结果表明NFATc1敲除后两种乳腺癌细胞系的增殖能力明显下降(P<0.05)。免疫印迹结果揭示,NFATc1敲除能够明显抑制癌细胞中RhoA/ROCK信号通路的激活(P<0.05)。结论:NFATc1可能通过调控RhoA/ROCK信号通路进而促进乳腺癌细胞增殖,有望成为治疗乳腺癌的新靶点。 相似文献
995.
目的:探讨血清YKL-40对肝细胞癌的诊断价值。方法:选取157例原发性肝细胞癌患者,51例肝良性疾病患者以及72例健康人纳入试验。ELISA法检测血清YKL-40浓度;应用ROC曲线分析,计算其敏感性、特异性和cutoff值,并与其他血清标志物比较曲线下面积,探讨其诊断价值。结果:血清YKL-40诊断肝细胞癌的cutoff值为69.35 ng/ml,肝癌组YKL-40浓度显著高于肝良性疾病组和健康人群组(P<0.001)。YKL-40在区分肝癌与健康人群、肝癌与肝良性疾病的敏感性和特异性分别为86.0%和93.1%,91.1%和43.1%。AST在早期肝癌和AFP阴性肝癌的AUC分别为0.846和0.862;YKL-40,AFP和AST联合用于区分肝癌与肝良性疾病的AUC为0.909。结论:血清YKL-40是一个潜在的独立的诊断肝细胞癌的标志物,YKL-40联合AFP与AST对于早期肝癌和AFP阴性肝癌有较好的诊断价值。 相似文献
996.
Tumor angiogenesis and lymphangiogenesis are important processes in tumor progression and metastasis. The inhibitory effects of 3‐O‐acetyloleanolic acid (3AOA), a pentacyclic triterpenoid compound isolated from Vigna sinensis K., on tumor‐induced angiogenesis and lymphangiogenesis in vitro and in vivo were studied. Angiopoietin‐1 is an important angiogenic and lymphangiogenic factor secreted from colon carcinoma CT‐26 cells under hypoxia conditions. 3AOA inhibited proliferation, migration, and tube formation of angiopoietin‐1‐treated human umbilical vein endothelial cells (HUVEC) and human lymphatic microvascular endothelial cells (HLMEC). 3AOA reduced angiogenesis and lymphangiogenesis in angiopoietin‐1‐stimulated Matrigel plugs. Also, 3AOA inhibited tumor growth and tumor‐induced angiogenesis and lymphangiogenesis in an angiopoietin‐1‐induced CT‐26 allograft colon carcinoma animal model. 3AOA inhibited activation of the angiopoietin‐1 receptor Tie‐2 and activation of the downstream signaling factors FAK, AKT, and ERK1/2 that are involved in the angiopoietin‐1/Tie‐2‐signaling pathway. Thus, 3AOA has an inhibitory effect on angiogenesis and lymphangiogenesis induced by angiopoietin‐1 both in vitro and in vivo, and the inhibitory effect of 3AOA is probably due to suppression of angiopoietin‐1/Tie‐2 signaling in HUVEC and HLMEC. 相似文献
997.
998.
《Clinical Lymphoma, Myeloma & Leukemia》2020,20(10):690-696
BackgroundHyperfractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone alternating with cytarabine and methotrexate (hyper-CVAD) is a commonly used regimen in adults with acute lymphoblastic leukemia (ALL)/lymphoblastic lymphoma (LBL). Adult patients fit for pediatric-inspired protocols have an excellent outcome with chemotherapy alone. However, it is unclear whether patients receiving hyper-CVAD should undergo allogeneic hematopoietic cell transplantation (HCT) as postremission therapy. Our aim was to examine the role of HCT at first complete remission (CR1) in adult ALL/LBL after hyper-CVAD.Patients and MethodsAdult patients with newly diagnosed ALL/LBL receiving frontline hyper-CVAD from 2008 to 2018 were identified and records retrospectively extracted.ResultsA total of 85 patients were identified and included for further analysis. The median (range) age was 23 (14-68) years, and 56 (66%) were male. A total of 24 (28%) had adverse cytogenetics, and 48 (56%) had at least one risk factor. All patients received hyper-CVAD as induction; induction failure was seen in 10 (12%). A total of 38 patients continued the hyper-CVAD course, while the remaining 47 received HCT in CR1. Three-year event-free survival (EFS) and overall survival for the entire cohort were 51.4% and 61.6%, respectively. Median follow-up of alive patients was 39.9 (3.8-123.8) months. At multivariable analysis for EFS, induction failure was associated with worse outcome (hazard ratio [HR], 4.8; 95% confidence interval [CI] 1.7-13.7; P = .003), whereas HCT in CR1 improved outcome (HR, 0.42; 95% CI 0.18-0.97; P = .044). Furthermore, HCT in CR1 was the only prognostic factor for overall survival (HR, 0.3; 95% CI 0.11-0.85; P = .023).ConclusionHCT at CR1 resulted in a favorable EFS and overall survival in ALL/LBL patients after hyper-CVAD frontline therapy. Given that hyper-CVAD is a widely used protocol for adult patients, further examination of this observation is warranted. 相似文献
999.
Danghui XuJianxin YaoYiwen ZhangNan XiaoPeng PengZhanfeng LiZhiyao PanZhifeng Yao 《Asian Pacific journal of cancer prevention》2020,21(4):911-917
Objective: The study was undertaken to investigate the effects of polyethyleneimine (PEI)-mediated adenovirus 5 early region 1A (E1A) on radiosensitivity of human hepatic carcinoma cell in vitro and to disclosure the underlying mechanism. Materials and Methods: Human hepatic carcinoma SMMC-7721 cell line was transfected with E1A gene using PEI vector. Untransfected cells (SMMC-7721 group), cells transfected with blank-vector (SMMC-7721-vect group), and cells transfected with E1A gene (SMMC-7721-E1A group) were treated with 6 MV X-ray irradiation at doses of 0, 1, 2, 4, 8 and Gy, respectively. Radiosensitivity was determined by MTT assay and quantified by calculating the cell survival rate. Cell-cycle distribution and apotosis rate were monitored by flow cytometry. Results: The survival rate of SMMC-7721-E1A was significantly lower than that of SMMC-7721 cell. Apoptosis rate of SMMC-7721-E1A group was significantly higher than that of SMMC-7721group (P<0.01).The ratio of S stage in cell cycle of SMMC-7721-E1A was significantly lower than that in SMMC-7721 cell. The ratio of G2/M stage in cell cycle of SMMC-7721-E1A was significantly higher than that in SMMC-7721 cell (P<0.01). Conclusion: PEI could transfect E1A gene into hepatic carcinoma cells PEI-mediated E1A could effectively enhance radiosensitivity of hepatic carcinoma cells which may be related to its effects on apoptosis promoting leading to S phase suppression and G2/M phase arrest. 相似文献
1000.
Yang Yu Qiaoyu Chen Xunlei Zhang Jian Yang Kaibo Lin Congfei Ji Aibing Xu Lei Yang Lin Miao 《Cancer science》2020,111(7):2297-2309
Long noncoding RNAs (lncRNAs) have recently been verified to have significant regulatory functions in many types of human cancers. The lncRNA ANRIL is transcribed from the INK4b‐ARF‐INK4a gene cluster in the opposite direction. Whether ANRIL can act as an oncogenic molecule in cholangiocarcinoma (CCA) remains unknown. Our data show that ANRIL knockdown greatly inhibited CCA cell proliferation and migration in vitro and in vivo. According to the results of RNA sequencing analysis, ANRIL knockdown dramatically altered target genes associated with the cell cycle, cell proliferation, and apoptosis. By binding to a component of the epigenetic modification complex enhancer of zeste homolog 2 (EZH2), ANRIL could maintain lysine residue 27 of histone 3 (H3K27me3) levels in the promoter of ERBB receptor feedback inhibitor 1 (ERRFI1), which is a tumor suppressor gene in CCA. In this way, ERRFI1 expression was suppressed in CCA cells. These data verified the key role of the epigenetic regulation of ANRIL in CCA oncogenesis and indicate its potential as a target for CCA intervention. 相似文献