全文获取类型
收费全文 | 2747篇 |
免费 | 425篇 |
国内免费 | 4篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 103篇 |
妇产科学 | 38篇 |
基础医学 | 117篇 |
口腔科学 | 67篇 |
临床医学 | 115篇 |
内科学 | 335篇 |
皮肤病学 | 14篇 |
神经病学 | 32篇 |
特种医学 | 144篇 |
外科学 | 122篇 |
综合类 | 15篇 |
预防医学 | 1875篇 |
眼科学 | 9篇 |
药学 | 19篇 |
肿瘤学 | 168篇 |
出版年
2023年 | 31篇 |
2022年 | 49篇 |
2021年 | 25篇 |
2020年 | 88篇 |
2019年 | 25篇 |
2018年 | 95篇 |
2017年 | 98篇 |
2016年 | 100篇 |
2015年 | 92篇 |
2014年 | 89篇 |
2013年 | 162篇 |
2012年 | 39篇 |
2011年 | 32篇 |
2010年 | 112篇 |
2009年 | 129篇 |
2008年 | 66篇 |
2007年 | 65篇 |
2006年 | 83篇 |
2005年 | 57篇 |
2004年 | 57篇 |
2003年 | 36篇 |
2002年 | 95篇 |
2001年 | 96篇 |
2000年 | 60篇 |
1999年 | 136篇 |
1998年 | 158篇 |
1997年 | 196篇 |
1996年 | 210篇 |
1995年 | 131篇 |
1994年 | 56篇 |
1993年 | 122篇 |
1992年 | 21篇 |
1991年 | 13篇 |
1990年 | 17篇 |
1989年 | 32篇 |
1988年 | 35篇 |
1987年 | 28篇 |
1986年 | 30篇 |
1985年 | 21篇 |
1984年 | 14篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 17篇 |
1980年 | 13篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 12篇 |
1976年 | 18篇 |
1975年 | 11篇 |
1974年 | 5篇 |
排序方式: 共有3176条查询结果,搜索用时 15 毫秒
111.
Alan Balsam PhD RD Nicole Grant MS Beatrice L. Rogers PhD 《Journal of community health》1996,21(1):37-49
The nutritional status of persons with HIV and AIDS [PWAs] is constantly challenged throughout the progression of the illness. Home-delivered meals programs for PWAs are rapidly developing across the country to address this problem among the growing population of people with HIV infection and AIDS. This study examined client socio-demographic characteristics (sex, age, ethnicity), types of services offered by these programs, organizational and financial criteria, and characteristics of survey respondents.Data for this study was obtained from 15 of the 17 known home-delivered meals programs for PWAs in the United States through an original, cross-sectional survey instrument conducted by telephone interview between March 1994 and May 1994.Results from this study show an increase in the number of minority populations who participate in these programs (36% African-American and 12% Hispanic vs. 51% Caucasian), as well as women (17.2%) and children (7%). Geographic location was an important determinant for program eligibility. The number of meals served weekly varied greatly (from 510 to 12,600 per week). Other significant services included nutrition counselling, newsletters, and holiday-basket programs. Enhancing service-delivery systems was one of the more prevalent high-priority concerns cited, especially with regard to food quality and safety.These results show that these programs are catering increasingly to minority populations, women and children, and that they are expanding their services to meet the growing needs of their client populations. These findings suggest that there is a greater need for meals and other home-based services for persons living with HIV and AIDS.This research was supported by the Massachusetts Department of Public Health.He formerly was Director of Elder Health at the Massachusetts Department of Public Health, Boston, MA; he is a founder and serves on the Board of Directors of Community Servings 相似文献
112.
Serum reactivity to murine mammary tumor virus (MuMTV) was inversely related to mammary tumor risk in 8-to 22-week-old BALB/cfC3H breeding females. Mice at low tumor risk exhibited high-titered serum reactivity to MuMTV (50% end point, greater than or equal to 1:40 by radioimmunoassay) approximately 3-6 months earlier than did the mice at high tumor risk. Maternal MuMTV antibody levels were correlated with the serum anti-MuMTV reactivity of their neonatal offspring (2 wk of age). Serologic antiviral reactivity in infected mice did not change during periods of pregnancy and lactation. All infected animals had detectable serum MuMTV reactivity by 33 weeks of age. The virus-neutralizing capabilities of some of these sera were tested, Sera from some of the young, low-tumor-risk animals that had MuMTV-precipitating antibodies also had virus-neutralizing activity. Conversely, none of the sera from the high-tumor-risk animals had detectable MuMTV-neutralizing antibodies. 相似文献
113.
FJ O'Callaghan AC Clarke H Joffe B Keeton R Martin A Salmon RD Thomas JP Osborne 《Archives of disease in childhood》1998,78(2):159-162
This report highlights the association between tuberous sclerosis and Wolff-Parkinson-White syndrome. Ten patients with concurrent diagnoses of Wolff-Parkinson-White syndrome and tuberous sclerosis were identified. Wolff-Parkinson-White syndrome presented early in life, nine cases being diagnosed in the first year. Eight of the 10 cases were male. In eight cases, the syndrome was associated with supraventricular tachycardias, and in nine with cardiac rhabdomyomata. One child died from cardiac failure secondary to obstruction of the left ventricular outflow tract by a rhabdomyoma. Five of nine survivors showed resolution of Wolff-Parkinson-White syndrome on follow up. The accessory pathway was localised in nine patients from surface electrocardiograms: six children had left sided pathways and three had right sided pathways. 相似文献
114.
Comprehensive mutational scanning of the p53 coding region by two- dimensional gene scanning 总被引:2,自引:0,他引:2
A comprehensive mutational scanning test for the p53 coding region based on
multiplex PCR and two-dimensional DNA electrophoresis was designed and
evaluated. In a 2-step multiplex PCR, the p53 coding region (exons 2-11)
was amplified as a single 8646-bp fragment by long- distance PCR in step
one. This fragment served as a template for the subsequent co-amplification
of the individual exons in two multiplex groups in step two. The multiplex
products were then separated, first on the basis of size in non-denaturant
polyacrylamide gels and then on the basis of sequence by denaturing
gradient gel electrophoresis (DGGE). Primers for optimal PCR, melting
behavior and 2-D gel distribution were designed using a recently developed
computer program. The resulting two-dimensional gene scanning (TDGS) test
was evaluated by screening, in a blinded fashion, 29 coded DNA samples from
Li- Fraumeni syndrome patients with previously identified germline
mutations. All mutations were correctly detected. This assay provides an
accurate, cost-effective and non-radioactive method for simultaneous
mutational scanning of all p53 coding exons.
相似文献
115.
116.
117.
118.
119.
120.
Allisha Weeden PhD RD Carol Ann Holcomb PhD Thomas J. Herald PhD Richard C. Baybutt PhD 《Journal of nutrition in gerontology and geriatrics》2013,32(2):241-254
Older adults frequently report use of vitamin and mineral (VM) supplements, although the impact of supplements on dietary adequacy remains largely unknown. The purpose of the current study was to evaluate micronutrient intakes of older adults with emphasis on identifying nutrients most improved by VM supplements, nutrients most likely to remain inadequate, and nutrients most likely consumed in excess. Community-based volunteers were recruited from senior centers and completed a questionnaire querying demographic data, current health status, and VM supplement use. Participants (n = 263) were then contacted by telephone to complete two 24-hour diet recalls and confirm VM supplement use. Dietary adequacy was determined by comparing the ratio of mean dietary intake to the Dietary Reference Intakes (DRI). Dietary consumption was lowest for vitamins D and E, calcium, and magnesium. VM supplementation most improved intakes of vitamins E, D, B6, folic acid, and calcium. Participants were most likely to exceed the Tolerable Upper Limit with supplementation of niacin, folic acid, and vitamin A. 相似文献