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   980篇
  免费   21篇
  国内免费   4篇
耳鼻咽喉   5篇
儿科学   12篇
妇产科学   37篇
基础医学   89篇
口腔科学   7篇
临床医学   42篇
内科学   152篇
皮肤病学   12篇
神经病学   73篇
特种医学   10篇
外科学   130篇
综合类   11篇
预防医学   285篇
眼科学   9篇
药学   41篇
中国医学   2篇
肿瘤学   88篇
  2023年   34篇
  2022年   40篇
  2021年   41篇
  2020年   51篇
  2019年   48篇
  2018年   44篇
  2017年   40篇
  2016年   21篇
  2015年   18篇
  2014年   66篇
  2013年   59篇
  2012年   39篇
  2011年   63篇
  2010年   50篇
  2009年   71篇
  2008年   75篇
  2007年   48篇
  2006年   44篇
  2005年   26篇
  2004年   16篇
  2003年   15篇
  2002年   17篇
  2001年   9篇
  2000年   4篇
  1999年   12篇
  1998年   6篇
  1997年   7篇
  1996年   6篇
  1995年   3篇
  1994年   1篇
  1993年   5篇
  1992年   2篇
  1991年   1篇
  1990年   3篇
  1989年   1篇
  1988年   2篇
  1986年   1篇
  1984年   1篇
  1983年   6篇
  1978年   1篇
  1977年   1篇
  1976年   1篇
  1975年   2篇
  1974年   1篇
  1973年   2篇
  1971年   1篇
排序方式: 共有1005条查询结果,搜索用时 31 毫秒
71.
Summary Objectives: To analyse disability trends over the 1980s–1990s in gender and race groups of early retirement ages in USA.Methods: Disability trends for white and black males and females aged 65–69 and 70+ are analysed using the 1982–1999 NLTCS. Disability is analysed at three levels (instrumental activities of daily living (IADL), activities of daily living (ADL), and institutionalisation).Results: 1) A larger increase in proportions of non-disabled blacks aged 65–69 compared with whites and males compared with females. 2) Differences in disability trends among gender and race groups. 3) A faster absolute decline in non-institutionalised disabled aged 65–69. 4) A larger absolute decline and a smaller relative decline in proportions of disabled aged 70+ compared with 65–69. 5) A significant decrease in the proportion of ADL disabled blacks and an increase of ADL disabled white females in the age group 70+.Conclusions: Americans aged 65–69 years manifest a significant improvement in health over the 1980s–1990s but the dynamics differs in gender and race groups. Possible reasons for these differences are discussed.  相似文献   
72.
To understand the differences among reference curves for bone mineral density (BMD) for Chinese, Japanese, and American Caucasian women, we measured the BMD at the anteroposterior (AP) lumbar spine (L1–L4), lateral lumbar spine (L2–L4), hip (including the femoral neck, trochanter, intertrochanter, Wards triangle, and total hip), and ultradistal forearm by the dual-energy X-ray absorptiometry (DXA) in a total of 2728 healthy Chinese women, aged 5–96 years. Documented BMD data for Japanese women and device manufacturers BMD new reference databases (including the NHANES III dataset) for American Caucasian women were also used in this study. The cubic regression model was found to fit best in analyzing the age-associated variations of BMD at various sites in Chinese women, i.e., the equations had the largest coefficient of determination (R 2). At the AP/Lat spine, trochanter, intertrochanter, and Wards triangle, BMD reference curves for Chinese women were lower than those for Japanese or Caucasian women, while at the femoral neck, total hip, and ultradistal forearm, the reference curves for Chinese women were higher than those for Japanese women, with overlaps and crossing of the curves for some age spans in comparing the Chinese and Caucasian women. There were significant differences in the peak BMD (PBMD) at various sites among the Chinese, Japanese, and Caucasian women (P = 0.000). The PBMDs for Chinese women at the lumbar spine and various sites of the hip were 5.7% ± 2.1% (mean ± SD, range, 2.7–7.9%) lower than those for Japanese women and 5.1% ± 2.7% (range, 0.5–7.2%) lower than those for Caucasian women; however, the PBMDs for Chinese women were 26.2% higher than those for Japanese women and 10% higher than those for Caucasian women at the ultradistal forearm. After the PBMD, average T-scores of Chinese women for losses at the AP lumbar spine with increasing age were nearly identical to those for Japanese women, but both were greater than those for Caucasian women. The average T-scores for BMD loss at various sites in Chinese women were higher than those for both Japanese and Caucasian women except at the femoral neck, where the T-scores of Chinese women were exceeded by those of both Japanese and Caucasian women. Estimated from the T-score curve of BMD loss, the age of osteoporosis occurrence at the femoral neck in Chinese women was about 10 years later than that in Japanese or Caucasian women; at the AP spine, Chinese women were similar to Japanese women; at the other sites, the age for occurrence of osteoporosis in Chinese women was about 5–15 years earlier than that in either Japanese or Caucasian women. There are differences in prevalence or odds ratio (OR) of osteoporosis at the same skeletal region for Chinese, Japanese, and Caucasian women aged 50 years or at different skeletal regions in women of the same race. The prevalences of osteoporosis at various regions of the hip in Chinese women are 10.1–19.8% and ORs are 22.0–32.3, of which prevalence at the femoral neck is the lowest (10.1%); the prevalences of osteoporosis in Japanese women are 11.6–16.8% and ORs are 21.1–26.3, of which prevalence at the femoral neck is the lowest (11.6%); and the prevalences of osteoporosis in Caucasian women are 13.0–20.0% and ORs are 19.4–48.9, of which prevalence at the femoral neck is the highest (20%). In conclusion, racial differences in BMD reference curves, prevalences, and risks of osteoporosis at various skeletal sites exist among native Chinese, Japanese, and American Caucasian women.  相似文献   
73.
Weight management and concern, body weight beliefs, and perceptions of friend's and family's weight concerns were examined in this study by race, grade, and gender. A stratified random sample was used to select schools within nine districts in South Carolina and an anonymous self-report paper-pencil questionnaire was completed by the students. The final sample included 3151 African American (42.3%) and White (57.7%) children (51.7% female) in the third (n=599), fifth (n=686), eighth (n=1168), and eleventh (n=698) grades. White girls were more likely to report being overweight (P=.0042), having higher personal weight concerns (P<.0001), and perceiving higher friend (P<.0001) and family weight concerns (P<.0001) than the African American girls. Using multiple regression, 29.8% of the variance in the children's personal weight concern scores was explained by perceptions of family's weight concerns (R(2)=.1659), gender (R(2)=.0762), perceptions of friend's weight concerns (R(2)=.0392), grade (R(2)=.0094), a Race x Gender interaction (R(2)=.0042), and race (R(2)=.003). Most of the children, particularly the white girls, have personal weight concerns and dieting practices which place them at risk for possible health problems. These results support the need for nutrition interventions and education in early childhood. Programs to prevent obesity and eating disorders should be tailored for differences by gender, grade, and race.  相似文献   
74.
Blood pressure, heart rate, and changes in facial and finger blood flow were monitored in 24 male Chinese and 24 male Caucasians while they described anger-provoking incidents and read out neutral material, either loudly and rapidly or softly and slowly. Describing the incidents loudly and rapidly heightened anger ratings and enhanced digital vasoconstriction but not blood pressure or heart rate; however, anger enhanced blood pressure during soft, slow speech. Facial blood flow increased during anger expression, irrespective of speech style, but decreased when neutral material was read out. The findings suggest that an increase in facial blood flow reduces peripheral vascular resistance during anger expression, and that baroreflexes attenuate increases in heart rate and blood pressure. Racial background did not influence subjective reports or physiological responses, possibly because the procedure did not draw strongly enough on cultural taboos.  相似文献   
75.
Objective: To investigate the contribution of body mass index (BMI) to mortality over 11 years of follow-up in a prevalent sample of dialysis patients aged 60+. Design: Multivariate Cox proportional hazards regression analysis. Setting: Multicenter stratified random sample of black and white older chronic dialysis patients in a southeastern state. Subjects: 316 patients on hemodialysis (HD) and peritoneal dialysis (PD). Main outcome measure: Continued survival from baseline interview in 1988 to June1999. Results: Adjusting for age, primary diagnosis of diabetes, cardiovascular comorbidity, HD/PD therapy, and patient-reported functional impairment, the interaction of baseline BMI with race and gender was associated with older patients' risk of mortality. Black females, black males, and white males with higher BMI had a reduced risk of mortality, while no protective effect of higher BMI was found for white females. Patients with cardiovascular comorbidity and greater functional impairment at baseline had increased mortality risk. BMI was not significantly correlated with serum albumin or functional impairment. Conclusion: BMI, a simple anthropometric measure that provides a marker of nutritional status,interacts with race and gender to predict long-term survival in older dialysis patients. The association of survival with dialysis adequacy,nutritional indicators, and cardiovascular status in black and white dialysis patients is an important area of study. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   
76.
A random urine calcium/creatinine ratio (UCa/Cr) is of practical use in screening for hypercalciuria. However, due to worldwide variations, reference values for the pediatric population are not yet well established. Furthermore, no study has been conducted to establish normal UCa/Cr values in young African-American (AA) children. It has also been previously reported that an elevated UCa/Cr is related to a high urine Na/K ratio (UNa/K). The objectives of the present study were: (1) to set normal values of random UCa/Cr by age and race in the pediatric population of Metropolitan Kansas City, (2) to identify potential racial differences in UCa/Cr between Caucasian (CS) and AA children, and (3) to determine the relationship between UCa/Cr and UNa/K in healthy children.A total of 368 healthy children of both genders were enrolled in the study. They were divided into four age groups as follows: (1) <7 months, (2) 8–18 months, (3) 19 months to 6 years, and (4) 7–16 years. Each group was subdivided into AA and CS. A non-fasting random urine specimen from each subject was analyzed for Ca, Na, K and creatinine.The median UCa/Cr values for AA were: (1) 0.13, (2) 0.09, (3) 0.06, and (4) 0.04 and for CS they were (1) 0.26, (2) 0.11, (3) 0.10, and (4) 0.09. The data showed a strong inverse relationship between UCa/Cr and age, the youngest children demonstrating the highest UCa/Cr. In each age group, UCa/Cr in CS exceeded the corresponding value in AA. The age-dependent 95th percentiles of UCa/Cr values for CS were (1) 0.70, (2) 0.50, (3) 0.28, and (4) 0.20 and for AA they were (1) 0.38 and (3) 0.24. Due to outliers, the 95th percentile could not be established for the other two AA subgroups. The relationship between UCa/Cr and UNa/K was found to be extremely weak in both AA (r 2 =0.00005) and CS (r 2 =0.02). On the other hand, a strong linear correlation was observed between UNa/K and age (CS r 2 =0.23, P<0.001, AA r 2 =0.19, P<0.001), explaining in part the lack of correlation between UNa/K and UCa/Cr.We conclude that the child’s age, ethnicity and geographic location should be taken into consideration when assessing UCa/Cr ratio. Contrary to what has previously been reported in hypercalciuric children, no significant relationship was found between UCa/Cr and UNa/K in healthy children. Received: 7 June 2000 / Revised: 21 September 2000 / Accepted: 23 September 2000  相似文献   
77.
This paper tests the relative income hypothesis by considering the relationship between mortality, income and relative deprivation in South Africa using individual-level data on income and five measures of relative deprivation each with a different reference group. We find that income tends to be protective of, and relative deprivation detrimental to health, but the latter often gives a better account of mortality than does income alone. For some population groups the fit is improved in specifications which include both income and relative deprivation. Overall, there seems to be solid evidence in support of the relative income hypothesis, particularly for the more economically disadvantaged population groups. Relative deprivation is especially significant when age is the reference group, suggesting that the comparison of socio-economic standing that has an impact on health tends to happen within cohorts. The results are robust to splitting the sample into urban/rural subsamples and to looking at the incidence of illness as the health outcome rather than mortality. While little is known about the mechanisms underlying the effect of relative deprivation on health and mortality, the consistent evidence in favor of age as a reference group, particularly in a context like South Africa's suggests that intra-cohort comparisons should be an avenue for more in depth investigation.  相似文献   
78.
BackgroundWhile recent reports suggest that people with disabilities (PwDs) are likely to be adversely impacted by COVID-19 and face multiple challenges, previous research has not examined if COVID-19 burdens are unequally distributed with respect to the disability characteristics of the U.S. population.ObjectiveThis article presents the first national scale study of the relationship between COVID-19 incidence and disability characteristics in the U.S. The objective is to determine whether COVID-19 incidence is significantly greater in counties containing higher percentages of socio-demographically disadvantaged PwDs, based on race, ethnicity, poverty status, age, and biological sex.MethodsThis study integrates county-level data on confirmed COVID-19 cases from the Johns Hopkins Center for Systems Science and Engineering database with multiple disability variables from the 2018 American Community Survey. Statistical analyses are based on bivariate correlations and multivariate generalized estimating equations that consider spatial clustering in the data.ResultsGreater COVID-19 incidence rate is significantly associated with: (1) higher percentages of PwDs who are Black, Asian, Hispanic, Native American, below poverty, under 18 years of age, and female; and (2) lower percentages of PwDs who are non-Hispanic White, above poverty, aged 65 or more years, and male, after controlling for spatial clustering.ConclusionsSocio-demographically disadvantaged PwDs are significantly overrepresented in counties with higher COVID-19 incidence compared to other PwDs. These findings represent an important starting point for more detailed investigation of the disproportionate impacts of COVID-19 on PwDs and highlight the urgent need for COVID-19 data collection systems to incorporate disability information.  相似文献   
79.
Summary  To compare the absolute risk of fracture to the risk of other conditions by race/ethnicity, we studied 83,724 women, aged 70–79. The projected number of fractures was similar to or exceeded the combined number of cardiovascular events and breast cancers. Osteoporosis prevention efforts should target women of all ethnicities. Introduction  The relative risk of fracture is lower in non-white compared to white women but the absolute risk of fracture in comparison to other common chronic conditions is uncertain. Methods  We performed a prospective cohort study of 83,724 women, age 50–79 years. Cardiovascular disease (CVD), invasive breast cancer and all fractures were identified over an average of 7.7 ± 2.6 years. Results  The incidence of fracture, breast cancer, stroke and CVD varied across ethnicity. The annualized (%) incidence of fracture was greatest in whites (2.4%) and American Indians (2.8%) and lowest among blacks (1.3%). The majority of hip fractures occurred in white women. The projected number of women who will experience a fracture in one year exceeded the combined number of women who would experience invasive breast cancer or a broad category of CVD events in all ethnic groups except blacks. In 10,000 black women, an estimated 153 women would experience CVD, and 35 women, breast cancer compared to 126 women expected to fracture in one year. Conclusion  The annual risk of suffering a fracture is substantial in women of all ethnicities. Osteoporosis prevention efforts should target all women irrespective of their race/ethnic backgrounds. This article is discussed in an editorial that is available at .  相似文献   
80.
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