全文获取类型
收费全文 | 14938篇 |
免费 | 1249篇 |
国内免费 | 17篇 |
专业分类
耳鼻咽喉 | 118篇 |
儿科学 | 386篇 |
妇产科学 | 304篇 |
基础医学 | 1930篇 |
口腔科学 | 207篇 |
临床医学 | 2304篇 |
内科学 | 2686篇 |
皮肤病学 | 172篇 |
神经病学 | 1279篇 |
特种医学 | 539篇 |
外科学 | 2042篇 |
综合类 | 307篇 |
一般理论 | 22篇 |
预防医学 | 1818篇 |
眼科学 | 205篇 |
药学 | 1119篇 |
1篇 | |
中国医学 | 16篇 |
肿瘤学 | 749篇 |
出版年
2022年 | 113篇 |
2021年 | 230篇 |
2020年 | 155篇 |
2019年 | 248篇 |
2018年 | 284篇 |
2017年 | 205篇 |
2016年 | 249篇 |
2015年 | 251篇 |
2014年 | 358篇 |
2013年 | 539篇 |
2012年 | 763篇 |
2011年 | 833篇 |
2010年 | 490篇 |
2009年 | 423篇 |
2008年 | 725篇 |
2007年 | 727篇 |
2006年 | 702篇 |
2005年 | 791篇 |
2004年 | 771篇 |
2003年 | 660篇 |
2002年 | 622篇 |
2001年 | 425篇 |
2000年 | 407篇 |
1999年 | 441篇 |
1998年 | 197篇 |
1997年 | 152篇 |
1996年 | 150篇 |
1995年 | 150篇 |
1994年 | 126篇 |
1993年 | 107篇 |
1992年 | 314篇 |
1991年 | 285篇 |
1990年 | 246篇 |
1989年 | 259篇 |
1988年 | 244篇 |
1987年 | 208篇 |
1986年 | 197篇 |
1985年 | 192篇 |
1984年 | 144篇 |
1983年 | 166篇 |
1982年 | 100篇 |
1981年 | 112篇 |
1979年 | 129篇 |
1978年 | 81篇 |
1977年 | 104篇 |
1975年 | 76篇 |
1974年 | 108篇 |
1973年 | 97篇 |
1972年 | 94篇 |
1971年 | 93篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Marginal rate-based analyses are widely used for the analysis of recurrent events in clinical trials. In many areas of application, the events are not instantaneous but rather signal the onset of a symptomatic episode representing a recurrent infection, respiratory exacerbation, or bout of acute depression. In rate-based analyses, it is unclear how to best handle the time during which individuals are experiencing symptoms and hence are not at risk. We derive the limiting value of the Nelson-Aalen estimator and estimators of the regression coefficients under a semiparametric rate-based model in terms of an underlying two-state process. We investigate the impact of the distribution of the episode durations, heterogeneity, and dependence on the asymptotic and finite sample properties of standard estimators. We also consider the impact of these features on power in trials designed to test intervention effects on rate functions. An application to a trial of individuals with herpes simplex virus is given for illustration. 相似文献
2.
3.
4.
D B Irving J L Cook H B Menz 《Journal of Science and Medicine in Sport》2006,9(1-2):11-22; discussion 23-4
5.
Will Kaufman Augustine S Chavez Betty Skipper Arthur Kaufman 《International journal for equity in health》2006,5(1):6-5
Background
A public hospital in New Mexico required collection of 50% of estimated costs prior to elective surgeries for self-pay patients. This study assesses the impact of this policy on access to elective surgical procedures. 相似文献6.
Systems of care (SOCs) have been developed throughout the country to meet the needs of children with severe emotional disturbances (SED) and their families. In these SOCs, multiple agencies and disciplines are expected to work together with informal community supports to address families' needs (Stroul & Friedman, 1986a). A review of the literature on the impact of SOCs suggests: (a) communities' service delivery systems change; and (b) children experience modest improvements in symptomatology and functioning. At the same time, little is known about (a) which components of the SOC approach, at what levels, are necessary to impact child and family outcomes; (b) the degree to which SOCs affect other family members, beyond the target child; and (c) the impact of community contexts and supports in SOCs. Future research should improve measurement of key SOC constructs, examine the relation between specific levels of implementation and outcomes for the entire family, and investigate the impact of broader community systems and supports on families within SOCs. © 2004 Wiley Periodicals, Inc. J Comm Psychol 32: 655–674, 2004. 相似文献
7.
Peter Stone MD FRNZCOG FRCOG David Cook FRNZCOG MRCOG John Hutton PhD FRNZCOG FRCOG Gordon Purdie BSc Henry Murray MD FRNZCOG MRCOG Lauren Harcourt MPP BA 《The Australian & New Zealand journal of obstetrics & gynaecology》1995,35(1):32-37
Summary: This is the first report of the largest study of blood pressure measurement in pregnancy in a New Zealand population using standardized definitions and methodology. Over 3,800 women who delivered in an 8-month period in the Wellington region were included in the study. Blood pressure measurement and the presence of oedema and proteinuria were recorded from booking until delivery and in the puerperium. Only 2.7% of women were unable to be contacted after delivery for details on outcomes. The results established normal ranges for blood pressure throughout pregnancy. The data show that Mood pressure greater than 140/90 until 35 weeks' gestation is outside 2 standard deviations at all gestations and justifies using these measurements as the definition of hypertension in pregnancy. The fall in blood pressure in the 2nd trimester was less than 1 mm Ffg per week in both the systolic and diastolic pressures. This fall was smaller than previously recorded in other studies. Gestational hypertension was the commonest blood pressure abnormality occurring in 15.2% of the population. This represented 69% of the pregnant women with a hypertensive disorder. The overall incidence of both gestational hypertension and preeclampsia was 18.5% which is higher than reported in other parts of the world. In this study obesity was significantly associated with hypertensive disorders in pregnancy. An arm circumference of >33 cm, one of the measurements of obesity, was found in 6.8% of the study population. Even after the effect of arm circumference was taken into account, hypertensive disorders were also more common in Pacific Island women. Ankle oedema was significantly associated with the development of both gestational hypertension and preeclampsia but the incidence of oedema was noted in only 11.9% of the subjects. 相似文献
8.
Teenage pregnancy is a well-documented problem in the United States, with approximately 890,000 teenage pregnancies occurring each year. Although teen pregnancy rates have declined since 1991, rates remain higher than the mid-1970s and are fourfold those of European countries. Substantial morbidity and social problems result from these pregnancies, affecting the mother, her children, other family members, and society. Multiple educational approaches have been used, with few demonstrating significant reductions in teen pregnancy. School-based programs have been diverse and multifaceted. Recently, programs with a comprehensive approach have shown potential for success. In this article, characteristics and elements of promising school-based programs are identified and discussed. It is imperative that school nurses play an active role in developing and implementing prevention programs that incorporate rigorous evaluation. As health educators, school nurses are in a prime position to implement and evaluate the effectiveness of teen pregnancy prevention programs. 相似文献
9.
Biological fixation of porous-coated implants 总被引:1,自引:0,他引:1
R J Haddad S D Cook K A Thomas 《The Journal of bone and joint surgery. American volume》1987,69(9):1459-1466
10.