首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3936篇
  免费   369篇
  国内免费   2篇
  4307篇
  2022年   40篇
  2021年   89篇
  2020年   46篇
  2019年   59篇
  2018年   73篇
  2017年   47篇
  2016年   102篇
  2015年   188篇
  2014年   200篇
  2013年   248篇
  2012年   241篇
  2011年   265篇
  2010年   157篇
  2009年   125篇
  2008年   193篇
  2007年   200篇
  2006年   186篇
  2005年   188篇
  2004年   166篇
  2003年   138篇
  2002年   139篇
  2001年   63篇
  2000年   55篇
  1999年   55篇
  1998年   48篇
  1997年   32篇
  1996年   32篇
  1995年   29篇
  1994年   26篇
  1993年   32篇
  1992年   51篇
  1991年   39篇
  1990年   29篇
  1989年   37篇
  1988年   36篇
  1987年   23篇
  1985年   27篇
  1984年   28篇
  1983年   28篇
  1982年   33篇
  1981年   25篇
  1980年   34篇
  1979年   24篇
  1978年   26篇
  1977年   21篇
  1976年   20篇
  1975年   18篇
  1974年   23篇
  1973年   21篇
  1971年   26篇
排序方式: 共有4307条查询结果,搜索用时 0 毫秒
871.

Background

The magnitude of socioeconomic health inequalities differs across age groups. It is less clear whether socioeconomic health inequalities differ across age groups by other factors that are known to affect the relation between socioeconomic position and health, like the indicator of socioeconomic position, the health outcome, gender, and as to whether socioeconomic health inequalities are measured in absolute or in relative terms. The aim is to investigate whether absolute and relative socioeconomic health inequalities differ across age groups by indicator of socioeconomic position, health outcome and gender.

Methods

The study sample was derived from the baseline measurement of the LifeLines Cohort Study and consisted of 95,432 participants. Socioeconomic position was measured as educational level and household income. Physical and mental health were measured with the RAND-36. Age concerned eleven 5-years age groups. Absolute inequalities were examined by comparing means. Relative inequalities were examined by comparing Gini-coefficients. Analyses were performed for both health outcomes by both educational level and household income. Analyses were performed for all age groups, and stratified by gender.

Results

Absolute and relative socioeconomic health inequalities differed across age groups by indicator of socioeconomic position, health outcome, and gender. Absolute inequalities were most pronounced for mental health by household income. They were larger in younger than older age groups. Relative inequalities were most pronounced for physical health by educational level. Gini-coefficients were largest in young age groups and smallest in older age groups.

Conclusions

Absolute and relative socioeconomic health inequalities differed cross-sectionally across age groups by indicator of socioeconomic position, health outcome and gender. Researchers should critically consider the implications of choosing a specific age group, in addition to the indicator of socioeconomic position and health outcome, as findings on socioeconomic health inequalities may differ between them.  相似文献   
872.
873.
874.
Gert Andres 《Genetica》1949,24(1):387-534
Ohne ZusammenfassungMit 18 Tabellen und 45 Textabbildungen  相似文献   
875.
Bernstein , Leon . (U. S. Salinity Lab., Riverside, Calif.) Osmotic adjustment of plants to saline media. II. Dynamic phase. Amer. Jour. Bot. 50(4): 360–370. Illus. 1963.—The time-course of osmotic adjustment in bean and pepper plants to increased salinity of the medium was determined by periodic sampling of plants following salt additions to the medium. Bean plants adjusted to increases of 1 atm OP within a day, the adjustment in roots occurring primarily at night following salt addition at 6 pm , whereas leaves and stems made most of their adjustment in the daytime. Pepper plants did not adjust completely to 1.5 atm NaCl additions in 48 hr, but OP increased by about the same amount in both species (0.5—1.0 atm per day). Diurnal fluctuations in OP of leaves and stems of both species and in roots of pepper were matched by parallel fluctuations in K concentrations. Added NaCl caused increased concentrations of K in leaves and stems which were more or less replaced by more slowly absorbed ions, Ca and Mg in bean leaves and Na in bean stems. Other salts produced comparable immediate effects on K level, but K was replaced more rapidly if the cation added was readily accumulated by the bean (Ca). In roots, Na uptake predominated if Na salts were added but K uptake was important on the CaCl2 treatment. The K effects suggest a passive distribution of K between the cell and the medium.  相似文献   
876.
877.
Leon Tetreault 《CMAJ》1964,91(2):61-66
The subjective effects of dextroamphetamine, methylphenidate and placebo were evaluated in 16 medical students during the period just prior to their final oral examinations. The subjects served as their own controls. The order of administration of the three medications for each student was randomized, and a double-blind technique was used throughout. A questionnaire method was employed for the collection of results, which proved to be a useful and effective means. It demonstrated that dextroamphetamine, methylphenidate and placebo were statistically different from one another with regard to their effect on efficiency of studying, fatigue, duration of sleep and appetite. There were also significant differences in the number of side effects caused by the three medications. The stimulants, however, did not increase the number of study hours, nor was their use recommended by the students when preparing for important examinations.  相似文献   
878.
879.
880.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号