全文获取类型
收费全文 | 8326篇 |
免费 | 641篇 |
国内免费 | 29篇 |
专业分类
耳鼻咽喉 | 57篇 |
儿科学 | 328篇 |
妇产科学 | 278篇 |
基础医学 | 1048篇 |
口腔科学 | 105篇 |
临床医学 | 1297篇 |
内科学 | 1498篇 |
皮肤病学 | 82篇 |
神经病学 | 916篇 |
特种医学 | 309篇 |
外科学 | 881篇 |
综合类 | 233篇 |
一般理论 | 5篇 |
预防医学 | 888篇 |
眼科学 | 114篇 |
药学 | 488篇 |
中国医学 | 1篇 |
肿瘤学 | 468篇 |
出版年
2021年 | 141篇 |
2020年 | 80篇 |
2019年 | 134篇 |
2018年 | 141篇 |
2017年 | 132篇 |
2016年 | 138篇 |
2015年 | 155篇 |
2014年 | 204篇 |
2013年 | 366篇 |
2012年 | 506篇 |
2011年 | 499篇 |
2010年 | 291篇 |
2009年 | 229篇 |
2008年 | 501篇 |
2007年 | 481篇 |
2006年 | 533篇 |
2005年 | 521篇 |
2004年 | 497篇 |
2003年 | 461篇 |
2002年 | 459篇 |
2001年 | 140篇 |
2000年 | 144篇 |
1999年 | 143篇 |
1998年 | 98篇 |
1997年 | 73篇 |
1996年 | 73篇 |
1995年 | 69篇 |
1994年 | 52篇 |
1993年 | 42篇 |
1992年 | 124篇 |
1991年 | 110篇 |
1990年 | 108篇 |
1989年 | 91篇 |
1988年 | 73篇 |
1987年 | 78篇 |
1986年 | 71篇 |
1985年 | 68篇 |
1984年 | 72篇 |
1983年 | 69篇 |
1982年 | 52篇 |
1980年 | 42篇 |
1979年 | 67篇 |
1978年 | 52篇 |
1976年 | 49篇 |
1975年 | 43篇 |
1974年 | 52篇 |
1973年 | 51篇 |
1972年 | 41篇 |
1971年 | 43篇 |
1970年 | 42篇 |
排序方式: 共有8996条查询结果,搜索用时 15 毫秒
1.
Zhenzhen Zhang Mark Garzotto Tomasz M. Beer Philippe Thuillier Stephen Lieberman Motomi Mori 《Nutrition and cancer》2016,68(8):1309-1319
Animal and human studies suggest fish oil and green tea may have protective effect on prostate cancer. Fatty acid synthase (FAS) has been hypothesized to be linked to chemoprotective effects of both compounds. This study evaluated the independent and joint effects of fish oil (FO) and green tea supplement (epigallocatechin-3-gallate, EGCG) on FAS and Ki-67 levels in prostate tissue. Through a double-blinded, randomized controlled trial with 2 × 2 factorial design, 89 men scheduled for repeat prostate biopsy following an initial negative prostate biopsy were randomized into either FO alone (1.9 g DHA + EPA/day), EGCG alone (600 mg/day), a combination of FO and EGCG, or placebo. We used linear mixed-effects models to test the differences of prostate tissue FAS and Ki-67 by immunohistochemistry between pre- and post-intervention within each group, as well as between treatment groups. Results did not show significant difference among treatment groups in pre-to-post-intervention changes of FAS (P = 0.69) or Ki-67 (P = 0.26). Comparing placebo group with any of the treatment groups, we did not find significant difference in FAS or Ki-67 changes (all P > 0.05). Results indicate FO or EGCG supplementation for a short duration may not be sufficient to produce biologically meaningful changes in FAS or Ki-67 levels in prostate tissue. 相似文献
2.
3.
Conall T. Morgan Brigitte Mueller Varsha Thakur Vitor Guerra Callaghan Jull Luc Mertens Mark Friedberg Fraser Golding Mike Seed Steven E.S. Miner Edgar T. Jaeggi Cedric Manlhiot Lynne E. Nield 《The Canadian journal of cardiology》2019,35(4):453-461
Background
The purpose of the study was to evaluate the association between fetal echocardiographic measurements and the need for intervention (primary coarctation repair, staged coarctation repair, or catheter intervention) in prenatally diagnosed coarctation of the aorta.Methods
A single-centre retrospective cohort study (2005-2015) of 107 fetuses diagnosed with suspected coarctation of the aorta in the setting of an apex-forming left ventricle and antegrade flow across the mitral and aortic valves.Results
Median gestational age at diagnosis was 32 weeks (interquartile range, 23-35 weeks). Fifty-six (52%) did not require any neonatal intervention, 51 patients (48%) underwent a biventricular repair. In univariable analysis, an increase in ascending aorta (AAo) peak Doppler flow velocity (odds ratio [OR], 1.40 [95% confidence interval [CI], 1.05-1.91] per 20 cm/s; P = 0.03) was associated with intervention. No intervention was associated with larger isthmus size (OR, 0.23; P < 0.001), transverse arch diameter (OR, 0.23; P < 0.001), and aortic (OR, 0.72; P = 0.02), mitral (OR, 0.58; P = 0.001), and AAo (OR, 0.53; P < 0.001) z-scores. In multivariable analysis, higher peak AAo Doppler (OR, 2.51 [95% CI, 1.54-4.58] per 20 cm/s; P = 0.001) and younger gestational age at diagnosis (OR, 0.81 [95% CI, 0.70-0.93] per week; P = 0.005) were associated with intervention, whereas a higher AAo z-score (OR, 0.65 [95% CI, 0.43-0.94] per z; P = 0.029) and transverse arch dimension (OR, 0.44 [95% CI, 0.18-0.97]; P = 0.05) decreased the risk of intervention.Conclusions
In prenatally suspected coarctation, the variables associated with intervention comprised smaller AAo and transverse arch size, earlier gestational age at diagnosis, and the additional finding of a higher peak AAo Doppler. 相似文献4.
5.
Christine E. Marx William T. Trost Lawrence J. Shampine Robert D. Stevens Christine M. Hulette David C. Steffens John F. Ervin Marian I. Butterfield Daniel G. Blazer Mark W. Massing Jeffrey A. Lieberman 《Neuropsychopharmacology》2006,60(12):1287-1294
BACKGROUND: Few data are currently available investigating neurosteroids (NS) in Alzheimer's disease (AD). The NS allopregnanolone may be decreased in serum and plasma in patients with AD, but it is unclear if allopregnanolone is also reduced in brain. Because a number of NS exhibit neuroprotective effects and impact cognitive performance in rodent models, these molecules may be relevant to the pathophysiology of neurodegenerative disorders. We therefore investigated prefrontal cortex (PFC) NS levels in AD. METHODS: Neurosteroid levels (allopregnanolone, pregnenolone, dehydroepiandrosterone [DHEA]) were determined in postmortem PFC in 14 male subjects with AD and 15 cognitively intact male control subjects by gas chromatography/mass spectrometry preceded by high-performance liquid chromatography purification. RESULTS: Subjects with AD exhibit significant reductions in allopregnanolone compared with cognitively intact control subjects (median levels = 2.50 ng/g vs. 5.59 ng/g, respectively; p = .02). Allopregnanolone levels are inversely correlated with neuropathological disease stage (Braak), r = -.49, p = .007. Median DHEA levels are elevated in subjects with AD (p = .01). CONCLUSIONS: Subjects with AD demonstrate significant reductions in PFC allopregnanolone levels, a finding that may be relevant to neuropathological disease stage severity. Neurosteroids may have utility as candidate biomarkers in AD. 相似文献
7.
8.
9.
Active and passive immunization with Pseudomonas aeruginosa ribosomal vaccines and antisera in the burned rat model 总被引:1,自引:0,他引:1
Pseudomonas aeruginosa ribosomal vaccines were tested for their ability to protect rats subjected to a 20% total body surface burn against the lethal effects of infection with homologous organisms. When administered prior to burning, the vaccines provided 100% protection. When administered postburning, the vaccine from one strain also provided 100% protection when the time interval between vaccination and infection was 3 days. When this time interval was reduced to 1 or 2 days, approximately 50% protection was obtained with the same vaccine. The vaccine from a second strain tested provided about 50% protection with a 3-day time interval. In addition, passive immunization using antiserum to a ribosomal vaccine was also demonstrated to be effective in protecting burned and infected rats, especially when multiple doses of antiserum were used. In this case, 80% protection was obtained (with no protection observed using multiple doses of normal serum). Finally, a comparison of ribosomal and lipopolysaccharide vaccines and antisera was also performed. 相似文献
10.