全文获取类型
收费全文 | 218842篇 |
免费 | 19953篇 |
国内免费 | 6483篇 |
专业分类
耳鼻咽喉 | 1578篇 |
儿科学 | 4628篇 |
妇产科学 | 2003篇 |
基础医学 | 39214篇 |
口腔科学 | 3683篇 |
临床医学 | 19796篇 |
内科学 | 30786篇 |
皮肤病学 | 3352篇 |
神经病学 | 9113篇 |
特种医学 | 6563篇 |
外国民族医学 | 85篇 |
外科学 | 17229篇 |
综合类 | 31142篇 |
现状与发展 | 26篇 |
一般理论 | 25篇 |
预防医学 | 13108篇 |
眼科学 | 4827篇 |
药学 | 19587篇 |
32篇 | |
中国医学 | 9221篇 |
肿瘤学 | 29280篇 |
出版年
2024年 | 456篇 |
2023年 | 2911篇 |
2022年 | 5752篇 |
2021年 | 7932篇 |
2020年 | 7159篇 |
2019年 | 7512篇 |
2018年 | 7439篇 |
2017年 | 7272篇 |
2016年 | 7370篇 |
2015年 | 7763篇 |
2014年 | 11772篇 |
2013年 | 13281篇 |
2012年 | 10905篇 |
2011年 | 12404篇 |
2010年 | 10548篇 |
2009年 | 10327篇 |
2008年 | 10455篇 |
2007年 | 11471篇 |
2006年 | 10529篇 |
2005年 | 10091篇 |
2004年 | 8887篇 |
2003年 | 7919篇 |
2002年 | 6061篇 |
2001年 | 5916篇 |
2000年 | 4851篇 |
1999年 | 4447篇 |
1998年 | 3486篇 |
1997年 | 3113篇 |
1996年 | 3127篇 |
1995年 | 2997篇 |
1994年 | 2702篇 |
1993年 | 2378篇 |
1992年 | 1955篇 |
1991年 | 1680篇 |
1990年 | 1440篇 |
1989年 | 1304篇 |
1988年 | 1196篇 |
1987年 | 901篇 |
1986年 | 698篇 |
1985年 | 972篇 |
1984年 | 985篇 |
1983年 | 623篇 |
1982年 | 775篇 |
1981年 | 640篇 |
1980年 | 549篇 |
1979年 | 486篇 |
1978年 | 378篇 |
1977年 | 302篇 |
1976年 | 348篇 |
1975年 | 217篇 |
排序方式: 共有10000条查询结果,搜索用时 15 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.
3.
4.
5.
Noninvasive imaging of cardiac fibrosis is important for early diagnosis and intervention in chronic heart diseases. Here, we investigated whether noninvasive, contrast agent-free MRI T2-mapping can quantify myocardial fibrosis in preclinical models of aging and pressure overload. Myocardial fibrosis and remodeling were analyzed in two animal models: (i) aging (15-month-old male CF-1 mice vs. young 6- to 8-week-old mice), and (ii) pressure overload (PO; by transverse aortic constriction in 4- to 5-month-old male C57BL/6 mice vs. sham-operated for 14 days). In vivo T2-mapping was performed by acquiring data during the isovolumic and early diastolic phases, with a modified respiratory and ECG-triggered multiecho TurboRARE sequence on a 7-T MRI. Cine MRI provided cardiac morphology and function. A quantitative segmentation method was developed to analyze the in vivo T2-maps of hearts at midventricle, apex, and basal regions. The cardiac fibrosis area was analyzed ex vivo by picro sirius red (PSR) staining. Both aged and pressure-overloaded hearts developed significant myocardial contractile dysfunction, cardiac hypertrophy, and interstitial fibrosis. The aged mice had two phenotypes, fibrotic and mild-fibrotic. Notably, the aged fibrotic subgroup and the PO mice showed a marked decrease in T2 relaxation times (25.3 ± 0.6 in aged vs. 29.9 ± 0.7 ms in young mice, p = 0.002; and 24.3 ± 1.7 in PO vs. 28.7 ± 0.7 ms in shams, p = 0.05). However, no significant difference in T2 was detected between the aged mild-fibrotic subgroup and the young mice. Accordingly, an inverse correlation between myocardial fibrosis percentage (FP) and T2 relaxation time was derived (R2 = 0.98): T2 (ms) = 30.45 – 1.05 × FP. Thus, these results demonstrate a statistical agreement between T2-map–quantified fibrosis and PSR staining in two different clinically relevant animal models. In conclusion, T2-mapping MRI is a promising noninvasive contrast agent-free quantitative technique to characterize myocardial fibrosis. 相似文献
6.
7.
8.
目的 运用CT区分脾脏血管性病变与淋巴瘤。方法 回顾性分析20例经手术、穿刺病理学检查证实的脾脏病变的发病年龄、性别、脾脏指数、病变大小、数目、有无液化、钙化、强化幅度、强化方式等特征,并进行统计学分析。结果 20例脾脏病变中,11例血管性病变(6例海绵状血管瘤,3例窦岸细胞血管瘤,2例硬化性血管瘤样结节性转化),9例淋巴瘤;两组间发病年龄、病变大小、数目、有无液化、钙化等差异无统计学意义;两组间脾脏指数、动脉期强化幅度差异具有统计学意义(P<0.05)。5例海绵状血管瘤呈不均匀性强化,1例呈渐进性填充式强化,2例窦岸细胞血管瘤呈“雀斑征”,1例硬化性血管瘤样结节性转化呈“辐轮征”;9例淋巴瘤实质部分均呈均匀、轻中度强化。结论 脾脏血管性病变与淋巴瘤CT表现不同,CT有助于明确诊断。 相似文献
9.
10.
《Vaccine》2022,40(32):4296-4300
Advanced computational methodologies suggested SARS-CoV-2, nonstructural proteins ORF1AB, ORF3a, as the source of immunodominant peptides for T cell presentation. T cell immunity is long-lasting and compatible with COVID-19 pathology. Based on the supporting clinical data, nonstructural SARS-CoV-2 protein vaccines could provide global immunity against COVID-19. 相似文献