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   3220436篇
  免费   255280篇
  国内免费   7525篇
耳鼻咽喉   45457篇
儿科学   101488篇
妇产科学   86693篇
基础医学   460563篇
口腔科学   92476篇
临床医学   302839篇
内科学   620600篇
皮肤病学   64969篇
神经病学   270936篇
特种医学   125151篇
外国民族医学   1128篇
外科学   471862篇
综合类   76362篇
现状与发展   2篇
一般理论   1361篇
预防医学   269136篇
眼科学   74964篇
药学   240792篇
  10篇
中国医学   6506篇
肿瘤学   169946篇
  2018年   34762篇
  2017年   26576篇
  2016年   29077篇
  2015年   33106篇
  2014年   47029篇
  2013年   72387篇
  2012年   98249篇
  2011年   103951篇
  2010年   60983篇
  2009年   57639篇
  2008年   97470篇
  2007年   103600篇
  2006年   104443篇
  2005年   101430篇
  2004年   97154篇
  2003年   93435篇
  2002年   91608篇
  2001年   144608篇
  2000年   149459篇
  1999年   126441篇
  1998年   37233篇
  1997年   33784篇
  1996年   33220篇
  1995年   32102篇
  1994年   30138篇
  1993年   28217篇
  1992年   102224篇
  1991年   99307篇
  1990年   96197篇
  1989年   92258篇
  1988年   85730篇
  1987年   84297篇
  1986年   80188篇
  1985年   76631篇
  1984年   58250篇
  1983年   49714篇
  1982年   30261篇
  1981年   26934篇
  1979年   54331篇
  1978年   38437篇
  1977年   32134篇
  1976年   30613篇
  1975年   32085篇
  1974年   39423篇
  1973年   37949篇
  1972年   35356篇
  1971年   32799篇
  1970年   30682篇
  1969年   28388篇
  1968年   26267篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
951.
Research coordinators in intensive care are a growing specialty about which little is known. This cross-sectional study surveyed the Australia and New Zealand Intensive Care Research Coordinators' Group (n = 49) regarding demographics, education, employment history, job structure, and role content. Most research coordinators were highly qualified and experienced nurses who undertake pharmaceutical trials, multicenter projects, departmental medical and nursing research, audits and data registries, and their own projects.  相似文献   
952.
Surfactant     
Surfactant, a complex substance containing specific proteins and phospholipids, is essential for gas exchange in the lungs. Research shows that surfactant not only lowers surface tension, but also plays a role in host defense. Surfactant replacement therapy is a cornerstone in the treatment of respiratory distress syndrome in premature infants. New information on endogenous surfactant composition including surfactant apoproteins has led to advances in the surfactant replacement products currently available. Because of the success of surfactant deficiency treatment in neonates, surfactant replacement therapy has been studied in both the pediatric and adult population for the treatment of other respiratory disorders. This article describes the composition, metabolism, and function of endogenous surfactant and other uses of surfactant replacement therapies in neonates.  相似文献   
953.
954.
955.
956.
957.
958.
959.
Introduction Patients with cystic fibrosis (CF) are known to be at risk for early osteoporosis, and the mechanisms that mediate bone loss are still being delineated. The aim of the present investigation was to investigate if a correlation exists in these patients between skeletal measurements by dual-energy x-ray absorptiometry (DXA) and two anabolic factors, dehydroepiandrosterone (DHEA) and insulin-like growth factor I (IGF-I), and proresorptive factors such as the cytokines interleukin-1β, tumor necrosis factor α, and interleukin-6. Methods We studied 32 outpatients (18 females; mean age: 26.2 ± 7.9 years) at a tertiary care medical center. The subjects had venous samples obtained, underwent anthropometric and bone mineral density (BMD) measurements, and completed a health survey. Serum IGF-I concentrations were below the age-adjusted mean in 78% of the participants, and DHEA sulfate (DHEAS) concentrations were low in 72%. Serum concentrations of all cytokines were on the low side of normal; nonetheless, there was a modest inverse correlation between IL-1β and BMD at all sites. Results In univariate analyses, IGF-I and DHEAS were significant correlates of BMD or bone mineral content. In final multivariate models controlling for anthropometric and other variables of relevance to bone density, only IGF-I was identified as a significant independent skeletal predictor. While alterations in DHEAS, IGF-I, and specific cytokines may contribute to skeletal deficits in patients with CF, of these factors a low IGF-I concentration appears to be most strongly correlated with BMD. Conclusions These findings may have therapeutic implications for enhancing bone density in these patients.  相似文献   
960.
Introduction Vitamin D plays an important role in bone health. Our purpose was to measure serum 25-hydroxyvitamin D concentrations and their determinants in a national sample (n=2,946) of New Zealanders aged 15 years and over.Findings Mean (99% CI) serum 25-hydroxyvitamin D concentrations were 47 (45–50) nmol/l in women and 52 (49–55) nmol/l in men. Mean concentrations in New Zealand European and Others (NZEO, n=2,440), Mori (n=370), and Pacific (n=136) were 51 (49–53), 42 (38–46) and 37 (33–42) nmol/l, respectively. Three percent of New Zealanders had serum 25-hydroxyvitamin D concentrations indicative of deficiency (≤17.5 nmol/l); 48% and 84% were insufficient based on cutoffs of ≤50 and ≤80 nmol/l. Determinants of serum 25-hydroxyvitamin D concentrations in women were age, ethnicity, obesity, latitude and season; determinants in men were ethnicity and season. Serum 25-hydroxyvitamin D in women declined with age; mean concentration was 13 (8–18) nmol/l lower in women 65 years or older and 9 (5–13) nmol/l lower in women 45–64 years compared with women 15–18 years. Spring to summer differences in serum 25-hydroxyvitamin D were 31 (28–34) and 28 (25–31) nmol/l in women and men, respectively. Obese women had lower vitamin status than normal-weight women by 6 (3–10). Women living in the South Island had a mean serum 25-hydroxyvitamin D that was 6 (3–9) nmol/l lower than women living in the North Island. Ethnicity and season are the major determinants of serum 25-hydroxyvitamin D in New Zealanders.Conclusion The high prevalence of vitamin D insufficiency in New Zealanders, particularly in older women, may warrant strategies to improve vitamin D status.  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