收费全文 | 932586篇 |
免费 | 67911篇 |
国内免费 | 1369篇 |
耳鼻咽喉 | 13016篇 |
儿科学 | 24461篇 |
妇产科学 | 23409篇 |
基础医学 | 133140篇 |
口腔科学 | 28367篇 |
临床医学 | 80756篇 |
内科学 | 183118篇 |
皮肤病学 | 19282篇 |
神经病学 | 72189篇 |
特种医学 | 37378篇 |
外国民族医学 | 81篇 |
外科学 | 152490篇 |
综合类 | 18039篇 |
现状与发展 | 1篇 |
一般理论 | 235篇 |
预防医学 | 61679篇 |
眼科学 | 21323篇 |
药学 | 72807篇 |
3篇 | |
中国医学 | 2125篇 |
肿瘤学 | 57967篇 |
2018年 | 9052篇 |
2017年 | 7111篇 |
2016年 | 7861篇 |
2015年 | 8975篇 |
2014年 | 12150篇 |
2013年 | 17678篇 |
2012年 | 24412篇 |
2011年 | 25316篇 |
2010年 | 14966篇 |
2009年 | 14444篇 |
2008年 | 24877篇 |
2007年 | 26000篇 |
2006年 | 26806篇 |
2005年 | 25729篇 |
2004年 | 24836篇 |
2003年 | 23801篇 |
2002年 | 23370篇 |
2001年 | 54912篇 |
2000年 | 56685篇 |
1999年 | 46933篇 |
1998年 | 10340篇 |
1997年 | 9055篇 |
1996年 | 9176篇 |
1995年 | 8919篇 |
1994年 | 8281篇 |
1993年 | 7602篇 |
1992年 | 35554篇 |
1991年 | 34030篇 |
1990年 | 32823篇 |
1989年 | 31982篇 |
1988年 | 29071篇 |
1987年 | 28344篇 |
1986年 | 26357篇 |
1985年 | 25225篇 |
1984年 | 17878篇 |
1983年 | 15171篇 |
1982年 | 7800篇 |
1981年 | 6763篇 |
1979年 | 15836篇 |
1978年 | 10625篇 |
1977年 | 9068篇 |
1976年 | 7901篇 |
1975年 | 8655篇 |
1974年 | 10516篇 |
1973年 | 9902篇 |
1972年 | 9406篇 |
1971年 | 8881篇 |
1970年 | 8465篇 |
1969年 | 7957篇 |
1968年 | 7222篇 |
Background
Although it is known that women do not participate in trials as frequently as men, there are limited recent data examining how women recruitment has changed over time.Methods
We conducted MEDLINE search using a validated strategy for randomized trials published in New England Journal of Medicine, Lancet, and Journal of the American Medical Association between 1986 and 2015, and included trials evaluating pharmacologic or nonpharmacologic therapies. We abstracted data on demographics, intervention type, clinical indication, and trial design characteristics, and examined their relationships with women enrollment.Results
In total, 598 trials met inclusion criteria. Women enrollment increased significantly over time (21% between 1986 and 1990 to 33% between 2011 and 2015; Pfor trend < 0.001) and did not differ by journal or funding source. Women enrollment varied with clinical indication, comprising 37% for non–coronary artery disease vascular trials, 30% for coronary artery disease trials, 28% for heart failure trials, and 28% for arrhythmia trials (P < 0.001), which were all significantly lower than the expected proportion in disease populations (P < 0.001). Women enrollment varied with trial type (31%, 29%, and 26% for pharmacologic, device, and procedural trials, respectively; P = 0.001). These findings were corroborated using multivariable analysis. We found significant positive correlations between women enrolled, and mean age and total number of participants. Fewer women were enrolled in trials reporting statistically significant results than those who did not (P = 0.001).Conclusions
Although enrollment of women has increased over time, it remains lower than the relative proportion in the disease population. Future studies should elucidate the reasons for persistent under-representation of women in clinical trials. 相似文献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Materials and methods: Medline, Embase, and Web of Science were searched. According to international guidelines, low bone mineral density was defined as Z-score?≤??2.0. In addition, we focused on Z-score?≤??1.0 because this may indicate a tendency towards low bone mineral density.
Results: We included 16 studies, comprising 465 patients aged 1–65?years. Moderate and conflicting evidence for low bone mineral density (Z-score?≤??2.0) was found for several body parts (total proximal femur, total body, distal femur, lumbar spine) in children with Gross Motor Function Classification Scales II and III. We found no evidence for low bone mineral density in children with Gross Motor Function Classification Scale I or adults, although there was a tendency towards low bone mineral density (Z-score?≤??1.0) for several body parts.
Conclusions: Although more high-quality research is needed, results indicate that deficits in bone mineral density are not restricted to non-ambulatory people with cerebral palsy.
- Implications for Rehabilitation
Although more high-quality research is needed, including adults and fracture risk assessment, the current study indicates that deficits in bone mineral density are not restricted to non-ambulatory people with CP.
Health care professionals should be aware that optimal nutrition, supplements on indication, and an active lifestyle, preferably with weight-bearing activities, are important in ambulatory people with CP, also from a bone quality point-of-view.
If indicated, medication and fall prevention training should be prescribed.