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   15445篇
  免费   842篇
  国内免费   151篇
耳鼻咽喉   96篇
儿科学   372篇
妇产科学   227篇
基础医学   1740篇
口腔科学   386篇
临床医学   1315篇
内科学   4777篇
皮肤病学   185篇
神经病学   1502篇
特种医学   609篇
外科学   2202篇
综合类   27篇
预防医学   573篇
眼科学   142篇
药学   670篇
中国医学   10篇
肿瘤学   1605篇
  2023年   127篇
  2022年   221篇
  2021年   417篇
  2020年   287篇
  2019年   352篇
  2018年   413篇
  2017年   333篇
  2016年   409篇
  2015年   430篇
  2014年   599篇
  2013年   811篇
  2012年   1167篇
  2011年   1213篇
  2010年   682篇
  2009年   700篇
  2008年   1076篇
  2007年   1144篇
  2006年   1040篇
  2005年   1013篇
  2004年   998篇
  2003年   824篇
  2002年   739篇
  2001年   106篇
  2000年   84篇
  1999年   113篇
  1998年   128篇
  1997年   124篇
  1996年   94篇
  1995年   86篇
  1994年   63篇
  1993年   77篇
  1992年   50篇
  1991年   62篇
  1990年   46篇
  1989年   29篇
  1988年   29篇
  1987年   39篇
  1986年   42篇
  1985年   24篇
  1984年   33篇
  1983年   27篇
  1982年   17篇
  1981年   18篇
  1980年   16篇
  1979年   12篇
  1978年   16篇
  1977年   11篇
  1976年   12篇
  1974年   12篇
  1967年   11篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
OBJECTIVE: A role of female hormones, including oral contraceptives, has been suggested in the etiology of focal nodular hyperplasia of the liver. There is, however, no epidemiologic quantification of this relationship. STUDY DESIGN: A hospital-based case-control study was conducted in Italy of 23 women with histologically confirmed focal nodular hyperplasia of the liver and 94 controls in the hospital for acute diseases. Odds ratios (ORs) were computed by use of multiple logistic regression models. RESULTS: Focal nodular hyperplasia was not associated with menstrual and reproductive factors. Ever oral contraceptive use was reported by 83% of cases and 59% of controls. The multivariate OR was 2.8 (95% confidence interval [CI], 0.8-9.4) for ever use, and 4.5 (95% CI, 1.2-16.9) for use > or = 3 years. The trend in risk with duration was statistically significant. CONCLUSIONS: This study confirms previous clinical observations, and provides a quantitative estimate of the association between use of oral contraceptives and focal nodular hyperplasia of the liver.  相似文献   
992.
993.
Research for new biocompatible and easily implantable materials continously proposes new molecules and new substances with biological, chemical and physical characteristics more and more adapted to aesthetic and reconstructive surgery. Bio-Alcamid (Polymekon, Italy) is a non reabsorbable polymeric material composed of alkylimide-amide groups. This cosmetic agent has been used for the treatment of 2000 patients by a multicentric trial led by different Hospitals and University in Italy and abroad. Very serious aesthetic defects such as pectus excavatum, Poland Syndrome, postoperative traumas, in addition to common aesthetic defects such as lips, cheek-bone and chin hypovolumetry and relaxing of nasolabial sulcus, have been treated by surgical implant of Bio-Alcamid. Aesthetic results were excellent; tissues felt soft and the implants were uniformly distributed. No migration or dislocation of the implants, no granulomas, no allergic response and no kind of intolerance were observed. Only 12/2000 patients had post-operative complications (Staphylococcus infections) and only 3/12 cases could be directly ascribed to the implanted material. For its characteristics Bio-Alcamid can be considered a novelty in the aesthetic and reconstructive surgery; it is absolutely biocompatible, non toxic, non allergenic, easily injectable and quickly removable. Bio-Alcamid can be defined a sort of "endoprosthetis", perfectly suitable for soft tissue augmentation and for the correction of different tissue deficiences, with a long-term safety and efficiency.  相似文献   
994.
The aim of this study was to evaluate in sedentary male subjects the effects of an acute bout of strenuous and moderate exercise on ex vivo platelet responsiveness and its possible relationship with exercise-associated modifications of oxidant-antioxidant status. An increased ADP- and collagen-evoked platelet aggregation associated with modified membrane fluidity and ion homeostasis was observed after exhaustive exercise. After moderate exercise, we found a decrease of platelet aggregation evoked by low concentrations of agonists. Strenuous exercise, but not moderate exertion, resulted in the enhanced accumulation of secondary products of lipid peroxidation, decreased total antioxidant capacity, including a diminished superoxide dismutase activity, and increased susceptibility of low-density lipoprotein (LDL) to in vitro oxidation. Acute elevation of plasma nitrite/nitrate (NOX) content was observed following each single session of physical test, whilst the platelet NOX content was decreased after strenuous exercise and increased after moderate exercise. Findings of the present study suggest that oxidative stress induced by acute strenuous exercise may interfere with platelet responsiveness most likely by promoting oxidized LDL-mediated platelet activation and by decreasing plasma and platelet-derived nitric oxide (NO) bioactivity. Moreover, our results further suggest that platelet responsiveness following an acute moderate physical stressor may depend on the efficiency of plasma and intraplatelet NO to desensitize platelets to agonist stimulation. Electronic Publication  相似文献   
995.
996.
997.
Several papers have shown that in young people sports activity is associated with a higher prevalence of cardiac valves incompetence, that can be detected, though to a lesser extent, even in healthy subjects randomly selected from the population. Aim of the present study was to analyse the effects of physical activity not only in young subjects but even in the elderly, with particular reference to valve competence, by using the Echo-Color-Doppler. The study cohort was represented by 80 healthy young subjects, 40 men and 40 women, aged between 20 and 25 years, each group subdivided into two subgroups, sedentary and non sedentary, and 80 healthy elderly subjects, 40 men and 40 women, aged between 65 and 91 years, again divided into sedentary and non sedentary. Valve incompetence was more frequent in the elderly if compared to young subjects (P<0.001) and in non sedentary if compared to sedentary subjects (P<0.01), while no significant difference was found between males and females. Worth of interest the fact that in young subjects valve incompetence was more frequent in non sedentary if compared to sedentary subjects (P<0.001), while in the elderly no significant difference was found between sedentary and non sedentary subjects. This original datum may be explained both by the natural higher prevalence of valve incompetence in the elderly, and by the kind of physical activity usually performed by the elderly, i.e. endurance activity.  相似文献   
998.
999.
1000.
We report on a male child with "apple-peel" atresia associated with microcephaly and ocular anomalies. To date, no magnetic resonance imagings have been published. We report on the fourth reported case with this phenotype, but the first to be studied by brain magnetic resonance imaging.  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