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   3450827篇
  免费   277022篇
  国内免费   6099篇
耳鼻咽喉   50018篇
儿科学   110689篇
妇产科学   95250篇
基础医学   487418篇
口腔科学   102366篇
临床医学   313872篇
内科学   666819篇
皮肤病学   72873篇
神经病学   289030篇
特种医学   137672篇
外国民族医学   1247篇
外科学   519123篇
综合类   83321篇
现状与发展   4篇
一般理论   1459篇
预防医学   276967篇
眼科学   81796篇
药学   258223篇
  6篇
中国医学   6379篇
肿瘤学   179416篇
  2018年   35540篇
  2016年   30989篇
  2015年   34804篇
  2014年   48742篇
  2013年   75327篇
  2012年   100931篇
  2011年   107084篇
  2010年   63044篇
  2009年   59365篇
  2008年   102151篇
  2007年   108151篇
  2006年   109161篇
  2005年   106235篇
  2004年   102932篇
  2003年   99255篇
  2002年   97897篇
  2001年   155871篇
  2000年   162014篇
  1999年   136690篇
  1998年   39905篇
  1997年   36083篇
  1996年   35471篇
  1995年   34373篇
  1994年   32350篇
  1993年   30250篇
  1992年   110080篇
  1991年   106400篇
  1990年   103266篇
  1989年   99793篇
  1988年   92733篇
  1987年   91541篇
  1986年   86887篇
  1985年   83469篇
  1984年   63422篇
  1983年   54397篇
  1982年   33028篇
  1981年   29502篇
  1980年   27837篇
  1979年   60147篇
  1978年   42374篇
  1977年   35822篇
  1976年   33556篇
  1975年   35532篇
  1974年   43748篇
  1973年   41741篇
  1972年   38867篇
  1971年   36203篇
  1970年   33806篇
  1969年   31577篇
  1968年   28813篇
排序方式: 共有10000条查询结果,搜索用时 547 毫秒
991.
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   
992.
993.
994.
995.
996.
997.
998.
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   
999.
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   
1000.
Both vascular surgery and endovascular interventions traumatise the arterial wall, especially the endothelium. The vessel responds with neointimal hyperplasia and/or constrictive remodelling, and this is still the limiting factor in curative interventions. Stent placement prevents constrictive remodelling but is the main trigger for in-stent restenosis. Hyperproliferation of neointimal tissue is the main response to arterial thrombosis, local inflammation or medio-intimal injury such as occurs, for example, after balloon dilatation in the region of arterial anastomoses or of a thrombectomy (Fogarty-manoeuvre). At present, research on prevention of restenosis is focused on inhibiting neointimal hyperproliferation by using drug-eluting stents, and especially sirolimus- or paclitaxel-eluting stents. In addition, further experimental research work is in progress, with the aim of esablishing new treatment regimens and solving the problem of neointimal formation, thrombosis and constrictive remodelling. These include both local and systemic pharmacological therapy, brachy- and laser therapy, and many genetic treatment options, some of which are currently the subjects of experimental studies and early-stage clinical trials. Gene therapy seems like a promising way of preventing restenosis, but has not yet been tested in clinical trials. In the near future, selective, simultaneous, and perhaps even polyphasic regulation for gene silencing of two or more genes involved in the development of restenosis could improve the long-term patency rate.  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