全文获取类型
收费全文 | 2656515篇 |
免费 | 194968篇 |
国内免费 | 5164篇 |
专业分类
耳鼻咽喉 | 36595篇 |
儿科学 | 88322篇 |
妇产科学 | 74724篇 |
基础医学 | 380349篇 |
口腔科学 | 76904篇 |
临床医学 | 234445篇 |
内科学 | 517116篇 |
皮肤病学 | 58938篇 |
神经病学 | 206822篇 |
特种医学 | 101741篇 |
外国民族医学 | 597篇 |
外科学 | 406628篇 |
综合类 | 59827篇 |
现状与发展 | 5篇 |
一般理论 | 775篇 |
预防医学 | 197612篇 |
眼科学 | 63061篇 |
药学 | 197722篇 |
8篇 | |
中国医学 | 6122篇 |
肿瘤学 | 148334篇 |
出版年
2018年 | 28264篇 |
2017年 | 21389篇 |
2016年 | 23775篇 |
2015年 | 27141篇 |
2014年 | 37703篇 |
2013年 | 55914篇 |
2012年 | 77194篇 |
2011年 | 81983篇 |
2010年 | 48504篇 |
2009年 | 45519篇 |
2008年 | 77213篇 |
2007年 | 82766篇 |
2006年 | 83646篇 |
2005年 | 80831篇 |
2004年 | 78043篇 |
2003年 | 74749篇 |
2002年 | 72666篇 |
2001年 | 129792篇 |
2000年 | 133160篇 |
1999年 | 111287篇 |
1998年 | 30409篇 |
1997年 | 26804篇 |
1996年 | 26966篇 |
1995年 | 25705篇 |
1994年 | 23986篇 |
1993年 | 22074篇 |
1992年 | 86819篇 |
1991年 | 84422篇 |
1990年 | 81963篇 |
1989年 | 79272篇 |
1988年 | 72950篇 |
1987年 | 71423篇 |
1986年 | 67733篇 |
1985年 | 64511篇 |
1984年 | 47648篇 |
1983年 | 40985篇 |
1982年 | 23659篇 |
1981年 | 21116篇 |
1979年 | 43665篇 |
1978年 | 30309篇 |
1977年 | 26045篇 |
1976年 | 24331篇 |
1975年 | 26248篇 |
1974年 | 31524篇 |
1973年 | 30308篇 |
1972年 | 28538篇 |
1971年 | 26401篇 |
1970年 | 24635篇 |
1969年 | 23418篇 |
1968年 | 21976篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
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
992.
Falls among the elderly: epidemiology and prevention 总被引:1,自引:0,他引:1
G S Sorock 《American journal of preventive medicine》1988,4(5):282-288
Harmful psychological and physical consequences may result when elderly people fall. I summarize the epidemiology of falls among elderly people and focus on three potentially remediable causes of falls: reduced peripheral neurosensation, the use of psychoactive medication, and environmental hazards. From 1960 to 1980, death rates from falls among white persons 75 years of age and older have decreased by more than 50%. Fall rates among community-dwelling elderly people increase with age and are greater for women than men. The death rates from falls, however, are now greater for men than women. Reduced peripheral neurosensation in the lower extremities may be a significant cause of falls among the elderly. Recreational walking or physical therapy may improve these deficits and lead to fewer falls. The use of psychoactive medications, most commonly benzodiazepine sedatives, is possibly associated with an increased risk of falls and hip fractures; greater caution in the use of these medications is warranted. The elimination or redesign of steps and curbs and the provision of hand railings and walking aids may be the most effective environmental approaches to preventing falls. These conclusions need further study in community-dwelling elderly populations. 相似文献
993.
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
994.
Mice killed shortly after receiving c. 2000 spores of a type E strain of Clostridium botulinum per os were incubated at one of five chosen temperatures together with bottles of cooked meat medium seeded with a similar inoculum. After incubation the rotting carcasses were homogenized. Sterile membrane filtrates of the homogenates (10%, w/v) and pure cultures were then titrated for toxicity. Some of the main findings were confirmed with two further type E strains. Toxicity produced at 37 degrees C was poor in both carcasses and cultures (200-20,000 mouse intraperitoneal LD/g or ml). It was good in both systems at 30 and 23 degrees C, usually reaching 20,000-200,000 LD/g or ml, and in carcasses occasionally more; at 30 degrees C maximal toxicity was reached more quickly in carcasses than in cultures. Prolonged incubation (36-118 days) at 30 or 23 degrees C resulted in complete loss of toxicity in virtually all carcasses but not in cultures. At 16 degrees C the development of toxicity in carcasses was strikingly greater than in cultures. At 9 degrees C neither system produced more than slight toxicity after prolonged incubation. Trypsinization increased the toxicity of cultures but not usually of carcasses. Unfiltered carcass homogenate (10%, w/v) with maximal intraperitoneal toxicity was harmless for mice by mouth in doses of 0.25 ml. These findings differed in important respects from those made earlier with a type C strain. 相似文献
995.
996.
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
997.
Correlation between concentrations of humoral antibodies and vitamin D nutritional status: a survey study 总被引:2,自引:0,他引:2
S H Sedrani 《European journal of clinical nutrition》1988,42(3):243-248
The vitamin D nutritional status and the plasma concentrations of IgG, IgA, IgM and total immunoglobulins were determined in 2052 Saudi subjects. It was observed that females had significantly lower 25-hydroxyvitamin D levels than males and children had lower levels than adults. The mean levels of IgG and IgM were significantly higher in females than in males and those in adults higher than in children. There was a highly significant positive correlation between the concentrations of the circulating form of vitamin D, 25-OHD, and IgG levels in the overall population, in children and in adults. When these groups were classified into males and females the correlation was significant only for females. The significance and importance of this correlation between vitamin D nutritional status and IgG is as yet unknown. The possible clinical relevance of this study's findings are discussed. 相似文献
998.
K A Burkman R W Gaines S R Kashani R D Smith 《Archives of physical medicine and rehabilitation》1988,69(2):132-134
Herpes zoster probably occurs more often than generally thought. Since it produces a radicular distribution of pain, it should be included in the differential diagnosis of radiculopathy. A case is presented in which evaluating the radicular low back pain before the characteristic rash appears was misleading. Careful history-taking concerning the exact nature of the pain and sensory changes is needed to differentiate between zoster and radiculopathy, if no rash is evident. 相似文献
999.
1000.