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   71971篇
  免费   4409篇
  国内免费   273篇
耳鼻咽喉   1112篇
儿科学   2029篇
妇产科学   1335篇
基础医学   7985篇
口腔科学   1457篇
临床医学   7089篇
内科学   15024篇
皮肤病学   1115篇
神经病学   6946篇
特种医学   2496篇
外国民族医学   5篇
外科学   12480篇
综合类   856篇
一般理论   94篇
预防医学   5990篇
眼科学   1382篇
药学   4566篇
中国医学   115篇
肿瘤学   4577篇
  2023年   394篇
  2022年   649篇
  2021年   1791篇
  2020年   933篇
  2019年   1559篇
  2018年   1824篇
  2017年   1317篇
  2016年   1343篇
  2015年   1484篇
  2014年   2281篇
  2013年   3213篇
  2012年   4876篇
  2011年   5074篇
  2010年   2788篇
  2009年   2461篇
  2008年   4482篇
  2007年   4740篇
  2006年   4593篇
  2005年   4579篇
  2004年   4306篇
  2003年   3968篇
  2002年   3688篇
  2001年   580篇
  2000年   507篇
  1999年   650篇
  1998年   748篇
  1997年   670篇
  1996年   594篇
  1995年   526篇
  1994年   511篇
  1993年   431篇
  1992年   392篇
  1991年   381篇
  1990年   315篇
  1989年   295篇
  1988年   303篇
  1987年   279篇
  1986年   293篇
  1985年   380篇
  1984年   451篇
  1983年   377篇
  1982年   540篇
  1981年   501篇
  1980年   461篇
  1979年   218篇
  1978年   286篇
  1977年   271篇
  1976年   215篇
  1975年   227篇
  1973年   190篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
OBJECTIVES: This study was designed to evaluate the immediate and long-term clinical results of patients undergoing endoluminal reconstruction in diffusely degenerated saphenous vein grafts (SVGs) with elective implantation of one or more less-shortening Wallstents. BACKGROUND: The optimal treatment strategy for patients with diffusely degenerated SVGs is controversial. Endoluminal reconstruction by stent implantation is one proposed strategy; however, there are few data regarding long-term clinical outcome. METHODS: Between May 1995 and September 1998, 6,534 consecutive patients underwent angioplasty in our institution, including 440 who were treated for SVG lesions. Of these, 126 (115 men, 11 women, median age 69.5 years, range: 33-86 years) with old SVGs (mean age: 13+/-5 years) diffusely degenerated stenosed or occluded (mean lesion length: 27+/-12 mm) were treated electively with implantation of one or multiple (total 197) less-shortening Wallstents. RESULTS: Before discharge, 13 patients (10.3%) sustained at least one major cardiovascular event, including 4 deaths (3.2%), 11 myocardial infarctions (MI) (8.7%), and 3 repeat revascularizations (target vessel = 1, nontarget vessel = 2, 2.4%). Surviving patients were followed for 22+/-11 months: 13 patients (11.1%) died, 11 (9.4%) sustained an MI, 37 underwent angioplasty (31.6%), and 4 (3.4%) underwent bypass surgery. The estimated three-year event-free survival rates (freedom from death, and freedom from death/MI/target vessel revascularization) were (mean +/- SE) 81.1+/-7.8% and 43.2+/-18.5%, respectively. CONCLUSIONS: The long-term clinical outcome of patients undergoing endoluminal reconstruction in diffusely degenerated SVG is relatively poor, mainly because of a high incidence of death or MI and the frequent need for repeat angioplasty. It is unlikely that percutaneous intervention alone will provide a satisfactory or definitive solution for these patients.  相似文献   
994.
Malaria a mosquito-borne disease caused by Plasmodium remains to be a main global burden despite concerted efforts to eliminate it. While diverse control strategies have been put in place for mosquito-borne diseases, vector control continues to be a critical component in infection prevention. Vector control majorly focuses on the eradication of mosquitoes using a variety of chemical insecticides that includes organochlorides, carbamates, organophosphates, and pyrethroids. The use of conventional insecticide-based as mosquito control strategies poses several challenges such as the widespread development of insecticide resistance, environmental damage concerns, and effects on non-target organisms. These challenges create a demand for the development and use of alternative pest control strategies that are sustainable, safer, and environmentally friendly to mosquito vector management. This review provides insight into alternative sustainable interventions for mosquito vector control in the form of biorational pesticides. Biorational pesticides are pesticides that have little or no effect on humans and environments and include entomopathogenic microorganisms, insect growth regulators, and endosymbiotic bacteria. It also puts into perspective their environmental impacts, benefits, and challenges. Further, countries like Sri Lanka, that are certified as malaria free by World Health Organization (WHO) incorporated the use of entomopathogenic bacteria, insect growth regulators and larvivorous fish in their national vector control programs leading to the successful elimination of malaria in 2016. We therefore highlight success stories of the countries that have implemented these interventions bringing out the lessons for countries that are battling malaria epidemics.  相似文献   
995.
Direct alcohol biomarkers, including urinary ethyl glucuronide (EtG), urinary ethyl sulfate (EtS), and blood phosphatidylethanol (PEth), are used to monitor alcohol abstinence in individuals who are mandated to abstain. In this consecutive case series study, we examined 1000 forensic reports of participants enrolled in a professionals health program who were contractually obligated to abstain from alcohol and who underwent recovery status evaluations. We identified 52 evaluations in which urinary EtG, EtS, and blood PEth were measured and which produced a positive result for at least one of these analytes. PEth, at a cutoff concentration of 20 ng/mL, revealed alcohol use more frequently than EtG or EtS at our laboratory's cutoff concentrations of 100 and 25 ng/mL, respectively. This was true, as well, at alternative EtG/EtS cutoff concentrations of 200/50, 300/75, and 400/100 ng/mL. PEth was more likely than EtG/EtS to be positive in participants previously diagnosed with alcohol use disorders (AUD), whereas EtG/EtS was more likely than PEth to be positive in participants without AUD. In this study, blood PEth was the most sensitive biomarker for evidencing alcohol use.  相似文献   
996.
997.
998.
999.
Sports-related concussion is the most common athletic head injury with football having the highest rate among high school athletes. Traditionally, research on the biomechanics of football-related head impact has been focused at the collegiate level. Less research has been performed at the high school level, despite the incidence of concussion among high school football players. The objective of this study is to twofold: to quantify the head impact exposure in high school football, and to develop a cumulative impact analysis method. Head impact exposure was measured by instrumenting the helmets of 40 high school football players with helmet mounted accelerometer arrays to measure linear and rotational acceleration. A total of 16,502 head impacts were collected over the course of the season. Biomechanical data were analyzed by team and by player. The median impact for each player ranged from 15.2 to 27.0 g with an average value of 21.7 (±2.4) g. The 95th percentile impact for each player ranged from 38.8 to 72.9 g with an average value of 56.4 (±10.5) g. Next, an impact exposure metric utilizing concussion injury risk curves was created to quantify cumulative exposure for each participating player over the course of the season. Impacts were weighted according to the associated risk due to linear acceleration and rotational acceleration alone, as well as the combined probability (CP) of injury associated with both. These risks were summed over the course of a season to generate risk weighted cumulative exposure. The impact frequency was found to be greater during games compared to practices with an average number of impacts per session of 15.5 and 9.4, respectively. However, the median cumulative risk weighted exposure based on combined probability was found to be greater for practices vs. games. These data will provide a metric that may be used to better understand the cumulative effects of repetitive head impacts, injury mechanisms, and head impact exposure of athletes in football.  相似文献   
1000.
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