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   350923篇
  免费   28309篇
  国内免费   14642篇
耳鼻咽喉   3610篇
儿科学   7546篇
妇产科学   5144篇
基础医学   41790篇
口腔科学   5183篇
临床医学   34529篇
内科学   52398篇
皮肤病学   3302篇
神经病学   12759篇
特种医学   12673篇
外国民族医学   84篇
外科学   54644篇
综合类   51945篇
现状与发展   35篇
一般理论   27篇
预防医学   16459篇
眼科学   6167篇
药学   32011篇
  57篇
中国医学   10733篇
肿瘤学   42778篇
  2024年   530篇
  2023年   4190篇
  2022年   7599篇
  2021年   11483篇
  2020年   10599篇
  2019年   10234篇
  2018年   10036篇
  2017年   10361篇
  2016年   11318篇
  2015年   11588篇
  2014年   19776篇
  2013年   21847篇
  2012年   19047篇
  2011年   21791篇
  2010年   18873篇
  2009年   18938篇
  2008年   19135篇
  2007年   20318篇
  2006年   19073篇
  2005年   17761篇
  2004年   14850篇
  2003年   13121篇
  2002年   10461篇
  2001年   9875篇
  2000年   8230篇
  1999年   6981篇
  1998年   5376篇
  1997年   4836篇
  1996年   4388篇
  1995年   4103篇
  1994年   3757篇
  1993年   2901篇
  1992年   2658篇
  1991年   2240篇
  1990年   1912篇
  1989年   1727篇
  1988年   1649篇
  1987年   1252篇
  1986年   987篇
  1985年   1189篇
  1984年   1125篇
  1983年   708篇
  1982年   869篇
  1981年   767篇
  1980年   648篇
  1979年   533篇
  1978年   453篇
  1977年   365篇
  1976年   380篇
  1975年   248篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.

Objective

The aim of the study was to estimate the effect of the state-based reinsurance programs through the section 1332 State Innovation Waivers on health insurance marketplace premiums and insurer participation.

Data Source

2015 to 2022 Robert Wood Johnson Foundation Health Insurance Exchange Compare Datasets.

Study Design

An event study difference-in-differences (DD) model separately for each year of implementation and a synthetic control method (SCM) are used to estimate year-by-year effects following program implementation.

Data Collection/Extraction Methods

Not applicable.

Principal Findings

Reinsurance programs were associated with a decline in premiums in the first year of implementation by 10%–13%, 5%–19%, and 11%–17% for bronze, silver, and gold plans (p < 0.05). There is a trend of sustained declines especially for states that implemented their programs in 2019 and 2020. The SCM analyses suggest some effect heterogeneity across states but also premium declines across most states. There is no evidence that reinsurance programs affected insurer participation.

Conclusion

State-based reinsurance programs have the potential to improve the affordability of health insurance coverage. However, reinsurance programs do not appear to have had an effect on insurer participation, highlighting the need for policy makers to consider complementary strategies to encourage insurer participation.  相似文献   
2.
目的 鉴定当地民间应用普遍的野生药用真菌,并探讨其治疗肿瘤的作用机制。方法 采用形态学和分子生物学方法对一株采自定陶仿山野生药用真菌进行鉴定,确定为硬皮马勃。通过文献检索收集硬皮马勃化学成分,利用PubChem软件和TCMSP、GCS数据库得到化学成分结构信息及其药用动力学参数和相关靶点分析,通过SysDT和WES系统鉴定潜在化学成分靶点,利用CTD数据库获得靶点功能,将潜在化合物和肿瘤相关靶点导入Cytoscape3.8.0软件构建分子-靶标网络。应用DAVID数据库对肿瘤相关靶点进行GO和KEGG富集分析,揭示有关活性成分靶点所涉及的生物学过程和通路,将肿瘤相关靶点和通路导入Cytoscape3.8.0软件构建靶点-通路网络。结果 从文献中获得硬皮马勃的化学成分59个,通过ADME计算系统筛选出5个潜在活性的化合物即活性成分,预测到38个靶点,其中与肿瘤相关靶点16个。这些活性成分主要通过Toll-like receptor、PI3K-AKT、MAPK和NF-kappa B等通路参与免疫应答,抑制肿瘤细胞生长、增殖,促进其凋亡。结论 表明硬皮马勃治疗肿瘤具有多靶点、多途径协同作用的特点,并通过多层次效应达到治疗肿瘤的效果。本研究为更好理解硬皮马勃作用肿瘤的机制和肿瘤药物开发提供理论依据。  相似文献   
3.
4.
目的 观察结肠癌HCT116细胞健脾消癌方的条件培养液对HUVEC细胞管腔形成的影响,从PI3K/Akt生物轴调控角度探讨其作用机制。方法 培养HCT116细胞,细胞设3组:对照组,健脾消癌方组(加入15%健脾消癌方含药血清)及人参皂苷Rg3组;制备HCT116细胞健脾消癌方条件培养液(分组及制备方法见实验方法),用条件培养液干预HUVEC(脐静脉内皮细胞,Human Umbilical Vein Endothelial Cells),Matrigel基质胶法检测HCT116细胞健脾消癌方条件培养液对HUVEC小管形成的影响。随后采用蛋白免疫印迹法(Western blot)检测各组HCT116细胞磷脂酰肌醇3-激酶(PI3K)、蛋白激酶B(Akt)、p-Akt、VEGF(血管内皮生长因子,Vascular endothelial growth factor)蛋白表达。最后在结肠癌HCT116荷瘤小鼠中验证健脾消癌方对肿瘤生长速度的影响,并经瘤组织VEGF蛋白表达、CD31免疫组化染色检测肿瘤内血管生成情况。结果 模型组HUVEC细胞管腔形成较空白血清组显著增加(P<0.05);健脾消癌方组及人参皂苷Rg3组较模型组HUVEC细胞管腔形成显著减少(P<0.01)。p-Akt和VEGF蛋白表达水平模型组高于空白血清组(P<0.05),健脾消癌方组及人参皂苷Rg3组显著低于模型组(P<0.01);PI3K、Akt蛋白表达量组间差异无统计学意义。与对照组比较,模型组荷瘤小鼠肿瘤体积显著性增大,瘤组织内VEGF表达、CD31阳性面积显著性增加,差异有统计学意义(P<0.05);与模型组比较,健脾消癌方组及人参皂苷Rg3组荷瘤小鼠肿瘤体积显著减小,瘤组织内VEGF表达、CD31阳性面积降低,差异有统计学意义(P<0.05)。结论 健脾消癌方可抑制肿瘤的血管生成和生长,其作用机制可能与PI3K/Akt生物轴调控VEGF表达有关。  相似文献   
5.
6.
《Cancer cell》2022,40(3):318-334.e9
  1. Download : Download high-res image (268KB)
  2. Download : Download full-size image
  相似文献   
7.
ObjectivesThe aim of this meta-analysis was to conduct a contemporary systematic review of high quality non-randomised controlled trials to determine the effect of pre-liver transplantation (LT) transarterial chemoembolisation (TACE) on long-term survival and complications of hepatocellular carcinoma (HCC) patients.BackgroundTACE is used as a neoadjuvant therapy to mitigate waitlist drop-out for patients with HCC awaiting LT. Previous studies have conflicting conclusions on the effect of TACE on long-term survival and complications of HCC patients undergoing LT.MethodsCINAHL, Cochrane Controlled Register of Trials, Embase, PubMed, and Web of Science were systematically searched. Baseline characteristics included number of patients outside Milan criteria, tumour diameter, MELD score, and time on the waiting list. Primary outcomes included 3- and 5-year overall and disease-free survival. Secondary outcomes included tumour recurrence, 30-day postoperative mortality, and hepatic artery and biliary complications.ResultsTwenty-one high-quality NRCTs representing 8242 patients were included. Tumour diameter was significantly larger in TACE patients (3.49 cm vs 3.15 cm, P = 0.02) and time on the waiting list was significantly longer in TACE patients (4.87 months vs 3.46 months, P = 0.05), while MELD score was significantly higher in non-TACE patients (10.81 vs 12.35, P = 0.005). All primary and secondary outcomes displayed non-significant differences.ConclusionPatients treated with TACE had similar survival and postoperative outcomes to non-TACE patients, however, they had worse prognostic features compared to non-TACE patients. These findings strongly support the current US and European clinical practice guidelines that neoadjuvant TACE can be used for patients with longer expected waiting list times (specifically >6 months). Randomised controlled trials would be needed to increase the quality of evidence.  相似文献   
8.
9.
BackgroundLiver resection is commonly performed for hepatic tumors, however preoperative risk stratification remains challenging. We evaluated the performance of contemporary prediction models for short-term mortality after liver resection in patients with and without cirrhosis.MethodsThis retrospective cohort study examined National Surgical Quality Improvement Program data. We included patients who underwent liver resections from 2014 to 2019. VOCAL-Penn, MELD, MELD-Na, ALBI, and Mayo risk scores were evaluated in terms of model discrimination and calibration for 30-day post-operative mortality.ResultsA total 15,198 patients underwent liver resection, of whom 249 (1.6%) experienced 30-day post-operative mortality. The VOCAL-Penn score had the highest discrimination (area under the ROC curve [AUC] 0.74) compared to all other models. The VOCAL-Penn score similarly outperformed other models in patients with (AUC 0.70) and without (AUC 0.74) cirrhosis.ConclusionThe VOCAL-Penn score demonstrated superior predictive performance for 30-day post-operative mortality after liver resection as compared to existing clinical standards.  相似文献   
10.
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