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   8073篇
  免费   623篇
  国内免费   15篇
耳鼻咽喉   24篇
儿科学   283篇
妇产科学   240篇
基础医学   1124篇
口腔科学   90篇
临床医学   1314篇
内科学   1312篇
皮肤病学   126篇
神经病学   734篇
特种医学   168篇
外科学   724篇
综合类   115篇
一般理论   22篇
预防医学   1076篇
眼科学   246篇
药学   604篇
中国医学   11篇
肿瘤学   498篇
  2024年   13篇
  2023年   93篇
  2022年   105篇
  2021年   220篇
  2020年   177篇
  2019年   273篇
  2018年   297篇
  2017年   226篇
  2016年   240篇
  2015年   259篇
  2014年   354篇
  2013年   482篇
  2012年   672篇
  2011年   662篇
  2010年   362篇
  2009年   314篇
  2008年   506篇
  2007年   554篇
  2006年   496篇
  2005年   520篇
  2004年   470篇
  2003年   449篇
  2002年   348篇
  2001年   62篇
  2000年   41篇
  1999年   54篇
  1998年   77篇
  1997年   57篇
  1996年   52篇
  1995年   44篇
  1994年   42篇
  1993年   46篇
  1992年   16篇
  1991年   14篇
  1990年   10篇
  1989年   6篇
  1988年   13篇
  1987年   5篇
  1986年   7篇
  1985年   7篇
  1984年   11篇
  1983年   4篇
  1982年   10篇
  1981年   6篇
  1980年   6篇
  1979年   3篇
  1978年   7篇
  1977年   5篇
  1974年   3篇
  1973年   5篇
排序方式: 共有8711条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
105.
Modest dietary restriction (DR) prolongs life in a wide range of organisms, spanning single-celled yeast to mammals. Here, we report the use of recent techniques in nutrition research to quantify the detailed relationship between diet, nutrient intake, lifespan, and reproduction in Drosophila melanogaster. Caloric restriction (CR) was not responsible for extending lifespan in our experimental flies. Response surfaces for lifespan and fecundity were maximized at different protein-carbohydrate intakes, with longevity highest at a protein-to-carbohydrate ratio of 1:16 and egg-laying rate maximized at 1:2. Lifetime egg production, the measure closest to fitness, was maximized at an intermediate P:C ratio of 1:4. Flies offered a choice of complementary foods regulated intake to maximize lifetime egg production. The results indicate a role for both direct costs of reproduction and other deleterious consequences of ingesting high levels of protein. We unite a body of apparently conflicting work within a common framework and provide a platform for studying aging in all organisms.  相似文献   
106.
107.
Pelvic lymphadenectomy is widely accepted as an essential part of radical cystectomy. It provides important information (number of lymph nodes involved, tumor volume, capsular perforation) for prognosis, which may help identify patients at increased risk for progression. More important, there is a growing body of evidence indicating that meticulous, extended pelvic lymphadenectomy may cure a substantial number of patients who would otherwise develop local recurrences or distant metastases. Furthermore, extended bilateral lymph node dissection facilitates cystectomy, makes it safer to perform and does not substantially alter morbidity of the operation.  相似文献   
108.
OBJECTIVE: Susceptibility to sarcoidosis and coeliac disease has been linked to the class II haplotype HLA-DR3, DQ2, and an association between the two disorders has been suggested. As a pilot study, we have sought to determine the prevalence of coeliac disease in a cohort of Irish patients with sarcoidosis. DESIGN: Prospective, case-controlled study. METHODS: One hundred and two sarcoid patients (47 males, 55 females) from the west of Ireland and 105 (52 males, 53 females) healthy, ethnically matched, controls underwent interview and screening for coeliac disease and human leucocyte antigen typing by serology. Those with elevated anti-gliadin IgA (AGA) and/or positive endomysial antibody (EMA) were offered small intestinal biopsy. RESULTS: Three (3%) sarcoid patients had a prior diagnosis of coeliac disease. A further 12 (12%) patients and four (4%) controls had elevated AGA (P = 0.047), of whom three and one, respectively, had positive EMA. Small intestinal biopsy in 11 patients and three controls confirmed coeliac disease in one individual each, giving a prevalence of coeliac disease in patients compared with controls of 4/102 (4%) versus 1/105 (1%) (P = 0.21). Sensitivity and specificity of EMA and elevated AGA in sarcoid patients was 100% and 50%, and 50% and 9%, respectively. Of the four affected sarcoid patients, three carried HLA-DR3, DQ2 and one carried DR5 (12), DR7, DQ2. CONCLUSION: We have demonstrated a moderately increased prevalence of coeliac disease in Irish patients with sarcoidosis, which we feel justifies future screening of our sarcoid population. Estimation of EMA is recommended and should be restricted to those with susceptible haplotypes.  相似文献   
109.
This preliminary study explored relationships between women's empowerment and HIV prevention on the national and individual level with a focus on Botswana. Among sub-Saharan Africa countries, HIV prevalence was positively correlated with indirect indicators of women's empowerment relating to their education (female enrollment in secondary education and ratio of female to male secondary school enrollment), but not to their economic status (female share of paid employment in industry and services) or political status (women's share of seats in national parliament), while controlling for gross national income, percentage of births attended, and percentage of roads paved. Condom use at last sexual encounter was positively and significantly correlated with both indicators of women's educational empowerment, but was not significantly related to the other two indices. Empowerment at the individual level was explored through a preliminary quantitative survey of 71 sexually active women in Gaborone, Botswana, that was conducted in February 2001. Regression analyses showed that women's negotiating power and economic independence were the factors most strongly related to condom use, and did not show that education was a crucial factor. Economic independence was the factor most strongly related to negotiating power. These results suggest that in Botswana, HIV prevention efforts may need to improve women's negotiating skills and access to income-generating activities.  相似文献   
110.
Thyroid hormone is essential for fetal and neonatal development in particular of the brain, but little is known about regulation of fetal thyroid hormone levels throughout human gestation. The purpose of this study was to clarify developmental trends and interrelationships among T(4), free T(4) (FT4), thyroxine-binding globulin (TBG), TSH, T(3), rT(3), and T(4) sulfate (T4S) levels in cord and fetal blood sera (n = 639, 15-42 wk gestation) and correlate infant levels (23-42 wk gestation) to maternal values (n = 428, 16-45 yr) and those of nonpregnant women (n = 233, 16-46 yr). In cord and fetal serum, T(4), T(3), and TBG levels increase with gestation until term; TSH, FT4, T4S, and rT(3) levels increase and peak in the late second/early third trimester and then decline to term; T(4)/TBG ratios increase until late second trimester and plateau to term. Term cord sera TSH, TBG, and all iodothyronine levels, except T(3), are higher than nonpregnant women. In the third trimester, cord serum FT4, TSH, rT(3), and T4S levels are also higher than corresponding maternal levels, but T(4), T(3), and TBG levels are lower than maternal values. The late second/early third trimester is a critical transition period in fetal thyroid hormone metabolism, which may be interrupted by preterm birth and contribute to postnatal thyroid dysfunction.  相似文献   
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