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   3613186篇
  免费   261982篇
  国内免费   9483篇
耳鼻咽喉   48863篇
儿科学   120027篇
妇产科学   99498篇
基础医学   508570篇
口腔科学   102303篇
临床医学   331265篇
内科学   705302篇
皮肤病学   85474篇
神经病学   292825篇
特种医学   137283篇
外国民族医学   944篇
外科学   540763篇
综合类   77816篇
现状与发展   8篇
一般理论   1395篇
预防医学   276901篇
眼科学   83857篇
药学   264163篇
  12篇
中国医学   8004篇
肿瘤学   199378篇
  2021年   28097篇
  2019年   28838篇
  2018年   41121篇
  2017年   31274篇
  2016年   35558篇
  2015年   40294篇
  2014年   55772篇
  2013年   83255篇
  2012年   112268篇
  2011年   118820篇
  2010年   71135篇
  2009年   67491篇
  2008年   110567篇
  2007年   117641篇
  2006年   119238篇
  2005年   114386篇
  2004年   110043篇
  2003年   105812篇
  2002年   102173篇
  2001年   175765篇
  2000年   179895篇
  1999年   151302篇
  1998年   43002篇
  1997年   37882篇
  1996年   38000篇
  1995年   36851篇
  1994年   33693篇
  1993年   31569篇
  1992年   117096篇
  1991年   112949篇
  1990年   109315篇
  1989年   105613篇
  1988年   96572篇
  1987年   94592篇
  1986年   88804篇
  1985年   84791篇
  1984年   63209篇
  1983年   53636篇
  1982年   31464篇
  1979年   55911篇
  1978年   39255篇
  1977年   33403篇
  1976年   31143篇
  1975年   32960篇
  1974年   39317篇
  1973年   37579篇
  1972年   35093篇
  1971年   32572篇
  1970年   30100篇
  1969年   28768篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
科学研究的目标是创造和传播知识。这得通过对系统收集以及报告信息的批判性分析来完成。批判性分析始于一个简单的步骤,即在运用复杂统计学分析方法进行比较之前对所收集的数据进行深入检查。根据所收集的数据类型按照标准化方式进行统计学分析。在为解决研究问题而需采用合理、标准化步骤进行比较时,新知识就产生了,同时要避免错误的结论。在对数据进行仔细检查和分析之后,为了保证结论的正确性,再对数据进行一次批判性评论是非常重要的补充步骤。在科学文献中发表研究成果过程中涉及的同行评价对于传播新知识并保证其质量方面是一个非常重要的步骤。如果没有将研究成果发表供同行参考,这项研究就不算完整。  相似文献   
992.
BACKGROUND: Abnormalities in calcium and vitamin D metabolism have been reported after bariatric surgery. The purpose of this study was to evaluate vitamin D nutritional status among morbidly obese patients before gastric bypass surgery. METHODS: We prospectively studied 279 morbidly obese patients seeking gastric bypass surgery for vitamin D nutritional status as assessed by serum 25-hydroxyvitamin D level. In addition, serum samples were analyzed for calcium, alkaline phosphatase (AP), intact parathyroid hormone (PTH), and 1,25-dihydroxyvitamin D. RESULTS: Mean patient age was 43 +/- 9 years; 87% of the study patients were women, and 72% were white. Serum calcium and AP levels were normal in 88% and 89% of the patients, respectively. Vitamin D depletion, defined as serum 25-hydroxyvitamin D level 相似文献   
993.
BACKGROUND: Preoperative dietary counseling (PDC) before bariatric surgery is mandated by a growing number of insurance payers. Their claim is that PDC improves outcomes and postoperative compliance. We compared outcomes of GBP patients undergoing a mandatory 13 weeks of PDC (n = 72) to a contemporaneous group of patients with no such requirement (no-PDC; n = 252) who underwent operation between January 2000 and December 2002. METHODS: The PDC and no-PDC groups were characterized by similar male:female ratios (1:4 vs 1:4.6), mean age (42 years), mean body weight (324 lb vs 309 lb), and mean body mass index (BMI) (52 kg/m2 vs 50 kg/m2). The PDC group had a higher incidence of obstructive sleep apnea compared with the no-PDC group (41% vs 28%; P < .04) but otherwise the two groups had similar incidences of obesity-related comorbidities. The presurgery dropout rate was 50% higher in the PDC group than in the no-PDC group (28% vs 19%; P < .05). RESULTS: At 1 year follow-up, the no-PDC patients had a statistically greater percentage excess weight loss (67% vs 60%; P < .0001), lower BMI (32 vs 35; P < .015), and lower body weight (197 vs 218; P < .01). Resolution of major comorbidities, complication rates, 30-day postoperative mortality, and postoperative compliance with follow-up were similar in the two groups. CONCLUSIONS: The data demonstrate that insurance-mandated PDC is an obstacle to patient access for surgical treatment of severe obesity and has no impact on weight loss outcome or postsurgical compliance. PDC should be abandoned by the insurance industry.  相似文献   
994.
Early micromotion of implant components and periprosthetic bone loss in patients undergoing total knee arthroplasty are thought to contribute to late aseptic loosening. In the pursuit of longer implant survival, the administration of bisphosphonates may be advocated as a means to buffer implants against microinstability and periprosthetic bone loss. A bibliographic search identified one metaanalysis and two randomised controlled trials dealing with this topic. Current evidence supports the hypothesis that the inhibiting effects of bisphosphonates on bone resorption reduce implant micromotion and periprosthetic bone loss at the one-year follow-up. Tested bisphosphonates include clodronate, pamidronate and alendronate. However, a decline in periprosthetic BMD is observed at the three-year follow-up following a sixmonth course of bisphosphonate administration. Length of follow-up in available studies is currently too short to determine whether bisphosphonates increase the longevity of implants. Furthermore, the optimal dose, modality and length of bisphosphonate administration have yet to be determined.  相似文献   
995.
Carbon monoxide (CO), a byproduct of heme catalysis, was shown to have potent cytoprotective and anti-inflammatory effects. In vivo recipient CO inhalation at low concentrations prevented ischemia/reperfusion (I/R) injury associated with small intestinal transplantation (SITx). This study examined whether ex vivo delivery of CO in University of Wisconsin (UW) solution could ameliorate intestinal I/R injury. Orthotopic syngenic SITx was performed in Lewis rats after 6 h cold preservation in control UW or UW that was bubbled with CO gas (0.1-5%) (CO-UW). Recipient survival with intestinal grafts preserved in 5%, but not 0.1%, CO-UW improved to 86.7% (13/15) from 53% (9/17) with control UW. At 3 h after SITx, grafts stored in 5% CO-UW showed improved intestinal barrier function, less mucosal denudation and reduced inflammatory mediator upregulation compared to those in control UW. Preservation in CO-UW associated with reduced vascular resistance (end preservation), increased graft cyclic guanosine monophosphate levels (1 h), and improved graft blood flow (1 h). Protective effects of CO-UW were reversed by ODQ, an inhibitor of soluble guanylyl cyclase. In vitro culture experiment also showed better preservation of vascular endothelial cells with CO-UW. The study suggests that ex vivo CO delivery into UW solution would be a simple and innovative therapeutic strategy to prevent transplant-induced I/R injury.  相似文献   
996.
997.
998.
InrecentcorrespondencewithasurgeonfriendfromChina ,IwastoldthatChinahaschangedconsid erablyinthepastdecade.Icanbelieveit.Theever presentpressuresofsocietyandpolitics,theworld widedemandsforcooperationansmutualassistance ,therecentwarsandthreatsthereof,theapparentin creasedincidenceofnaturaldisasters ,andmoststrikinglythequantumleapoftechnologyandcommunica tionovertherecentpasthaveaffectedeveryareaoflife .Onecansaywithoutequivocationthatthewholeworldhaschangeddramaticallyoverthepastdecade .Th…  相似文献   
999.
2000年11月,作者得知从Aarhus大学医院皮肤科患者分离到的金黄色葡萄球菌对苯唑西林出现界线耐药(BORSA)。本文旨在描述其表型和基因型,并评估可能的传播途径以干预和阻止进一步蔓延。菌株由脉冲场凝胶电泳鉴定。几个感染控制方案的缺口显示患者间可直接或间接传播。皮肤屏障缺陷、皮肤病患者金黄色葡萄球菌的高携带率和院内双氯西林的高消耗率可促使传播。改善普通感染控制措施和重新评价院内抗生素政策后,该菌的暴发感染消失。  相似文献   
1000.
The onset of the sporadic Creutzfeldt-Jakob disease is usually characterized by dementia or neurological symptoms. We are reporting the case of a 31 year-old man with a sporadic Creutzfeldt-Jakob disease characterized by a schizophrenia-like onset. The schizophrenic symptoms developed for sixteen months before the neurological symptoms appeared. The psychiatric onset of the present case was linked with the early age of onset and the long duration of the disease and could have been influenced by polymorphism of the codon 129 of the prion protein gene (PRNP) and a type of pathological prion protein (PrPres).  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