全文获取类型
收费全文 | 5728208篇 |
免费 | 427591篇 |
国内免费 | 17364篇 |
学科分类
医药卫生 | 6173163篇 |
出版年
2021年 | 57599篇 |
2019年 | 59970篇 |
2018年 | 78200篇 |
2017年 | 60082篇 |
2016年 | 67044篇 |
2015年 | 78709篇 |
2014年 | 113581篇 |
2013年 | 179598篇 |
2012年 | 163686篇 |
2011年 | 175674篇 |
2010年 | 137775篇 |
2009年 | 135808篇 |
2008年 | 160925篇 |
2007年 | 173772篇 |
2006年 | 179745篇 |
2005年 | 174078篇 |
2004年 | 173983篇 |
2003年 | 163550篇 |
2002年 | 152834篇 |
2001年 | 229832篇 |
2000年 | 228532篇 |
1999年 | 202884篇 |
1998年 | 80672篇 |
1997年 | 74098篇 |
1996年 | 71843篇 |
1995年 | 67448篇 |
1994年 | 61403篇 |
1993年 | 56704篇 |
1992年 | 152734篇 |
1991年 | 147167篇 |
1990年 | 142080篇 |
1989年 | 137924篇 |
1988年 | 127919篇 |
1987年 | 125784篇 |
1986年 | 119462篇 |
1985年 | 115878篇 |
1984年 | 91931篇 |
1983年 | 80568篇 |
1982年 | 56838篇 |
1981年 | 52243篇 |
1980年 | 48995篇 |
1979年 | 83512篇 |
1978年 | 63322篇 |
1977年 | 55094篇 |
1976年 | 51659篇 |
1975年 | 53143篇 |
1974年 | 61731篇 |
1973年 | 59424篇 |
1972年 | 55971篇 |
1971年 | 51718篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
941.
This study surveyed male and female athletes from 22 midwesterncolleges and universities regarding behaviors and attitudesassociated with anorexia nervosa and bulimia nervosa. The responserate was 66% (N= 695) and the findings indicated that the bodyimage of some athletes may be distorted; one-seventh perceivedthemselves as fat even though they were not. Many athletes seemedpreoccupied with food and weight; almost one-third reportedroutinely thinking about food and weight and more than one-thirdreported dramatic annual weight fluctuations (9 lb or greater)related to bingeing and fasting. Athletes also did not feelin control when they ate and their habits related to food consumptionappeared to be extreme; one-tenth reported a lack of controlwhen they ate, more than one-third binged, one-twentieth ateuntil they were physically ill, and a similar proportion preferrednot to eat in the presence of others. In addition, it was foundthat as many men as women athletes reported these perceptionsbut significant sex differences were noted for specific items.It was suggested that behaviors and attitudes be viewed on acontinuum with normals at one end, eating disordered individuals at the other end,and college athletes in between. Health education that focuseson behaviors and attitudes as symptoms of eating disorders wasrecommended for athletes and those working closely with athletes.Future research was suggested to determine reasons for the undesirablebehaviors and attitudes and to study the onset, development,long-term effects and whether these behaviors and attitudeslead to an eating disorder. 相似文献
942.
943.
M Schooneveldt T Songer P Zimmet K Thoma 《Journal of epidemiology and community health》1988,42(1):89-95
An analysis of mortality data for the years 1982-5 was carried out for the Micronesian population (aged 15 years and over) of the central Pacific Island, Nauru. Among males, the most common causes of death were circulatory system disorders (33.3%), accidents (25.2%), and diabetes mellitus (12.1%). The majority of accidents occurred in the 15-34 year age group and involved motor vehicles. Among females, neoplasms (almost all lung and cervix) (22.4%), circulatory system disorders (20.7%), and diabetes mellitus (17.2%) were the most common causes of death. When accidents are excluded, 59.4% of deaths were in persons with diabetes. Compared with Australia, mortality rates in almost all age groups were at least five times higher for males and females for a comparable period. Nauruan life expectancy (39.5 years for men and 48.5 years for women) is one of the lowest in the world. These data confirm the high mortality associated with diabetes mellitus in Nauruans as evidenced in earlier studies. Modernization of this society through the affluence acquired by the mining of phosphate has led to serious public health problems relating to non-communicable diseases so that the mortality trends now mirror those of developed societies. 相似文献
944.
To study the effect of alcohol on glucose and insulin metabolism,a simultaneous infusion of glucose and insulin was given for150 min to healthy volunteers, once during alcohol and onceduring calorie-free gingerale (control) ingestion. During alcoholintake, the average steady-state (between 100 and 150 min) glucoseof 5.44±0.39 mmol/1. and the average steady-state insulinof 6.3±1.1 ng/ml were significantly higher than those(4.0±0.39 mmol/1. of glucose and 4.4±0.6 ng/mlof insulin) observed during the control state. Despite the highersteady-state insulin concentrations, the glucose metabolismwas significantly less during alcohol ingestion. These findingssuggest alcohol-induced impairment in glucose metabolism iscaused by a decreased tissue sensitivity to insulin. 相似文献
945.
946.
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
947.
Birth weight on 12,644 singleton infants from 6,196 sibships born in Maryland between 1980 and 1984 were used to estimate the effects of nine maternal and infant covariates on the sibship correlation in birth weight. Assuming a homogeneous correlation across all families, the estimated intraclass correlation was 0.4664 (+/- 0.0099). This high sibship correlation makes it possible to predict, with reasonable accuracy, the birth weight of a child given information on previous sibs, as well as covariates on the mother and/or infant pertinent to a given pregnancy. The reduction in variance associated with incorporating information on the nine covariates used here was approximately equal to that obtained by conditioning on a single previous sib. Testing for heterogeneity in correlation among different groups of families showed that a crude measure of parity (first live birth vs. other), time between births, mother's marital status, and maternal age at the birth of the last child significantly influenced the sibship correlation in birth weight. 相似文献
948.
949.
950.
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