全文获取类型
收费全文 | 33508篇 |
免费 | 2406篇 |
国内免费 | 122篇 |
专业分类
耳鼻咽喉 | 325篇 |
儿科学 | 1151篇 |
妇产科学 | 789篇 |
基础医学 | 4797篇 |
口腔科学 | 533篇 |
临床医学 | 3234篇 |
内科学 | 6663篇 |
皮肤病学 | 661篇 |
神经病学 | 3416篇 |
特种医学 | 946篇 |
外科学 | 4078篇 |
综合类 | 687篇 |
现状与发展 | 1篇 |
一般理论 | 43篇 |
预防医学 | 2711篇 |
眼科学 | 836篇 |
药学 | 2266篇 |
中国医学 | 65篇 |
肿瘤学 | 2834篇 |
出版年
2023年 | 240篇 |
2022年 | 495篇 |
2021年 | 892篇 |
2020年 | 532篇 |
2019年 | 781篇 |
2018年 | 900篇 |
2017年 | 646篇 |
2016年 | 738篇 |
2015年 | 877篇 |
2014年 | 1125篇 |
2013年 | 1610篇 |
2012年 | 2379篇 |
2011年 | 2229篇 |
2010年 | 1353篇 |
2009年 | 1211篇 |
2008年 | 2003篇 |
2007年 | 2019篇 |
2006年 | 1871篇 |
2005年 | 1870篇 |
2004年 | 1849篇 |
2003年 | 1719篇 |
2002年 | 1478篇 |
2001年 | 413篇 |
2000年 | 409篇 |
1999年 | 420篇 |
1998年 | 326篇 |
1997年 | 256篇 |
1996年 | 251篇 |
1995年 | 231篇 |
1994年 | 172篇 |
1993年 | 209篇 |
1992年 | 286篇 |
1991年 | 254篇 |
1990年 | 251篇 |
1989年 | 251篇 |
1988年 | 233篇 |
1987年 | 211篇 |
1986年 | 214篇 |
1985年 | 242篇 |
1984年 | 195篇 |
1983年 | 153篇 |
1982年 | 165篇 |
1981年 | 161篇 |
1980年 | 143篇 |
1979年 | 125篇 |
1977年 | 105篇 |
1976年 | 122篇 |
1975年 | 104篇 |
1974年 | 131篇 |
1973年 | 100篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
BackgroundLittle is known about the extent of ordering low-value services by.PurposeTo compare the rates of low-value back images ordered by primary care physicians (PCMDs) and primary care nurse practitioners (PCNPs).MethodWe used 2012 and 2013 Medicare Part B claims for all beneficiaries in 18 hospital referral ?regions (HRRs) and a measure of low-value back imaging from Choosing Wisely. Models included random clinician effect and fixed effects for beneficiary age, disability, Elixhauser comorbidities, clinician sex, the emergency department setting, back pain visit volume, organization, and region (HRR).FindingsPCNPs (N = 231) and PCMDs (N = 4,779) order low-value back images at similar rates (NP: all images: 26.5%; MRI/CT: 8.4%; MD: all images: 24.5%; MRI/CT: 7.7%), with no detectable significant difference when controlling for covariates.DiscussionPCNPs and PCMDs order low-value back images at an effectively similar rate. 相似文献
3.
4.
5.
6.
7.
8.
Dana Franzen-Klein Mark Jankowski Charlotte L. Roy Hoa Nguyen-Phuc Da Chen Lorin Neuman-Lee 《Journal of toxicology and environmental health. Part A》2020,83(2):45-65
ABSTRACTDomestic chickens (Gallus gallus domesticus) were exposed to imidacloprid by gavage once daily for 7 consecutive days at 0, 0.03, 0.34, 3.42, 10.25, and 15.5 mg/kg/day (n = 20 per group; 5 6-week-old males, 5 6-week-old females, 5 9-week-old males, and 5 9-week-old females). The severity and duration of neurobehavioral abnormalities were recorded. Components of the innate and adaptive immune system were assessed with 7 standard functional assays. Temporary neurobehavioral abnormalities were observed in a dose-dependent manner, including muscle tremors, ataxia, and depressed mentation. Based upon mean clinical severity scores, the no observed adverse effect level (NOAEL) was 3.42 mg/kg/day, and the lowest observed adverse effect level (LOAEL) was 10.25 mg/kg/day. The effective dose value for the presence of any neurobehavioral abnormalities in 50% of the test group (ED50) was 4.62 ± 0.98 mg/kg/day. The ED50 for an adjusted score that included both severity and duration of neurobehavioral abnormalities was 11.24 ± 9.33 mg/kg/day. These ED50 values are equivalent to a 1 kg bird ingesting 29 or 70 imidacloprid treated soybean seeds respectively. Immunotoxicity was not documented, possible causes include the assays were insensitive, relevant immune functions were not examined, or imidacloprid is not immunotoxic at this dosing schedule in this species. Neurobehavioral abnormalities were a more sensitive indicator of the sublethal effects of imidacloprid than immunotoxicity. 相似文献
9.
10.