全文获取类型
收费全文 | 2450276篇 |
免费 | 222584篇 |
国内免费 | 4992篇 |
专业分类
耳鼻咽喉 | 36097篇 |
儿科学 | 74854篇 |
妇产科学 | 64957篇 |
基础医学 | 336923篇 |
口腔科学 | 71930篇 |
临床医学 | 238015篇 |
内科学 | 487624篇 |
皮肤病学 | 50938篇 |
神经病学 | 210459篇 |
特种医学 | 98693篇 |
外国民族医学 | 886篇 |
外科学 | 374319篇 |
综合类 | 56326篇 |
现状与发展 | 41篇 |
一般理论 | 977篇 |
预防医学 | 201880篇 |
眼科学 | 57247篇 |
药学 | 178383篇 |
4篇 | |
中国医学 | 4379篇 |
肿瘤学 | 132920篇 |
出版年
2018年 | 29812篇 |
2017年 | 24875篇 |
2016年 | 27043篇 |
2015年 | 29865篇 |
2014年 | 42008篇 |
2013年 | 60846篇 |
2012年 | 71729篇 |
2011年 | 75116篇 |
2010年 | 48076篇 |
2009年 | 48260篇 |
2008年 | 71566篇 |
2007年 | 75001篇 |
2006年 | 76897篇 |
2005年 | 73728篇 |
2004年 | 70525篇 |
2003年 | 67967篇 |
2002年 | 67132篇 |
2001年 | 113962篇 |
2000年 | 117456篇 |
1999年 | 99711篇 |
1998年 | 29530篇 |
1997年 | 27010篇 |
1996年 | 26962篇 |
1995年 | 25907篇 |
1994年 | 23979篇 |
1993年 | 22257篇 |
1992年 | 79964篇 |
1991年 | 76868篇 |
1990年 | 73964篇 |
1989年 | 71212篇 |
1988年 | 66232篇 |
1987年 | 65081篇 |
1986年 | 61587篇 |
1985年 | 58623篇 |
1984年 | 44411篇 |
1983年 | 37876篇 |
1982年 | 23050篇 |
1981年 | 20487篇 |
1979年 | 41338篇 |
1978年 | 29076篇 |
1977年 | 24439篇 |
1976年 | 22899篇 |
1975年 | 24015篇 |
1974年 | 29693篇 |
1973年 | 28080篇 |
1972年 | 26290篇 |
1971年 | 24186篇 |
1970年 | 22791篇 |
1969年 | 21104篇 |
1968年 | 19137篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Incidence and trends in incidence of definite hypertension were analyzed based on 30 years follow-up of 5,209 subjects in the Framingham Heart Study cohort. Based on pooling of 15 two-year periods, hypertension incidence per biennium increased with age in men from 3.3 per cent at ages 30-39 to 6.2 per cent at ages 70-79, and in women from 1.5 per cent at ages 30-39 to 8.6 per cent at ages 70-79. No consistent trend in incidence rates was evident for either sex from the 1950s through the 1970s. The proportion of hypertensive subjects receiving antihypertensive medication has increased since 1954-58 and exceeded 80 per cent for both men and women ages 60-89 years in 1979-81. Incidence data presented in this report may serve as a baseline for assessing the impact of future public health efforts in the primary prevention of hypertension. 相似文献
992.
993.
994.
Eight-eight female weanling Sprague-Dawley rats were fed diets containing either 650 or 150 mg magnesium/kg diet and 7.0 or 3.5 mg pyridoxine-HCl/kg diet, in a 2 x 2 factorial arrangement, during growth, gestation, and lactation. The objective of the study was to determine whether concurrent dietary deficiencies of magnesium and pyridoxine were synergistic, additive, or antagonistic with regards to effects on reproductive performance, growth, and development of offspring, and tissue content of magnesium and calcium. Body weight of dams and pups was not different between groups until day 9 of lactation, at which point those animals in either low magnesium group weighed less than the other. Litter size and birth weight were not different. Development, as measured by timing of unfolding of the external ear, opening of both eyes, and clinical emergence of incisors, was delayed in pups from litters in the low magnesium groups. A synergistic effect on delay of onset of ear unfolding by deficiency of both magnesium and pyridoxine was observed. Calcium content of heart and kidney from dams was increased in the low magnesium groups. Renal calcium was not further increased by the level of pyridoxine deficiency in this study. The calcium to magnesium ratio in heart from pups was higher in those from litters in the low magnesium and pyridoxine group than in the others. Results indicate that simultaneous deficiencies of magnesium and pyridoxine may impair function synergistically. Because these two nutrients are often reported to be presented in inadequate amounts in diets of women in their reproductive years, the potential exists for impaired reproductive success. 相似文献
995.
G J Wintemute J F Kraus S P Teret M A Wright 《American journal of preventive medicine》1988,4(6):343-348
Previous epidemiological studies of drowning in the United States have dealt primarily with children. The epidemiology and prevention of drowning in adulthood may be very different. To test this general hypothesis, we analyzed the 293 drownings occurring among Sacramento County residents 20 years of age and above during 1974 to 1985. Drowning rates were highest for men 20-29 years of age (11.5 per 100,000 population) and blacks (7.5 per 100,000 population). Swimmers, boaters, and motor vehicle occupants were most frequently represented. Alcohol use was involved in 48% of cases overall and 77% of those involving motor vehicle occupants. A history of seizure disorder was another contributing factor. Important differences do exist in drowning epidemiology between children and adults. Our results suggest that preventing drowning will be more problematic among adults than among children. The study was also used to test the sensitivity of two commonly used methods of case ascertainment for cases in Sacramento County. A manual review of coroner's records had a sensitivity of 96%. A computerized review of death certificate data from the state's vital statistics data base had a sensitivity of 79%. The sources and implications of these differences are discussed. 相似文献
996.
997.
The Framingham Disability Study: physical disability among community-dwelling survivors of stroke 总被引:6,自引:0,他引:6
A M Jette J L Pinsky L G Branch P A Wolf M Feinleib 《Journal of clinical epidemiology》1988,41(8):719-726
The relationship between stroke and physical disability was examined in a cohort of adult, Framingham, Massachusetts, residents who, between 1948 and 1951, were assembled for a longitudinal examination of cardiovascular disease. Multivariate analyses examined the amount of residual disability attributable to stroke among 2540 community-dwelling survivors, 27 years after their initial examination, after controlling for age, cardiovascular risk factors, other cardiovascular diseases, and eight general health conditions related to physical disability. Among men living in the community, a history of stroke explained 12% of the variance in physical disability. Suffering a stroke, however, was not as strongly related to physical disability among women living in the community, accounting for only 3% of the variance. Results suggest that although older men and women die from the same major causes, they may not be disabled by the same conditions. 相似文献
998.
999.
In the doubly-labelled water (2H2(18)O) method for the measurement of carbon dioxide production rate in man, single exponential disappearance curves for 2H2O and H2(18)O in body water are used; the precision with which the slopes and intercepts of the curves are estimated determines the precision of the estimate of carbon dioxide production rate. In studies with infants, and in computer simulations, the effect of different experimental regimes on the overall precision of the carbon dioxide production estimate was investigated. When the number of data points used was progressively reduced by shortening the total observation period from 7 d (about 3 biological half-lives for the isotopes) to 1 d there was a deleterious effect on precision and in the infants there was an upward bias in the values for carbon dioxide production. When the number of data points was reduced by removing points from the middle of the exponential curves with the maintenance of the 7-d experimental period, precision was also reduced but by less than in the former procedure and there were no consistent trends in the average values for carbon dioxide production. 相似文献
1000.
Mr. Charles V. Clark M.D. David J. Ewing 《Documenta ophthalmologica. Advances in ophthalmology》1988,70(4):309-321
Ocular autonomic function was assessed in 4 patients with progressive autonomic failure (PAF) and age-matched control subjects, by measurement of the pupil cycle time, and determination of autonomic denervation hypersensitivity of the iris. Pupil cycle time was abnormal in all patients with PAF; sustained pupil cycling was absent in 5 of the 8 eyes tested of the PAF patients, compared with only 16 eyes from 70 control subjects. Pupil constriction in response to 2.5% methacholine, indicative of parasympathetic denervation hypersensitivity, was significantly increased in patients with PAF (p < 0.001), whilst pupil dilation in response to 0.5% phenylephrine, indicative of sympathetic denervation hypersensitivity, was also significantly higher in the PAF patients (p < 0.001). The results suggest that ocular autonomic function may provide a sensitive early indicator of generalised autonomic dysfunction. 相似文献