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   1430315篇
  免费   115281篇
  国内免费   6370篇
耳鼻咽喉   17490篇
儿科学   46267篇
妇产科学   38073篇
基础医学   195214篇
口腔科学   36837篇
临床医学   126485篇
内科学   297034篇
皮肤病学   32420篇
神经病学   119926篇
特种医学   59833篇
外国民族医学   274篇
外科学   226456篇
综合类   32279篇
现状与发展   2篇
一般理论   414篇
预防医学   115186篇
眼科学   29137篇
药学   98781篇
  5篇
中国医学   2231篇
肿瘤学   77622篇
  2018年   23832篇
  2017年   19170篇
  2016年   22977篇
  2015年   14724篇
  2014年   20301篇
  2013年   30097篇
  2012年   39239篇
  2011年   48437篇
  2010年   31995篇
  2009年   29498篇
  2008年   46255篇
  2007年   50953篇
  2006年   40281篇
  2005年   40608篇
  2004年   39286篇
  2003年   39571篇
  2002年   36430篇
  2001年   66466篇
  2000年   68520篇
  1999年   56857篇
  1998年   16965篇
  1997年   15294篇
  1996年   16183篇
  1995年   16412篇
  1994年   15299篇
  1993年   14311篇
  1992年   47280篇
  1991年   45943篇
  1990年   44182篇
  1989年   41993篇
  1988年   38916篇
  1987年   38261篇
  1986年   36021篇
  1985年   34790篇
  1984年   26463篇
  1983年   22204篇
  1982年   13958篇
  1981年   12478篇
  1980年   11845篇
  1979年   23683篇
  1978年   17152篇
  1977年   14425篇
  1976年   13271篇
  1975年   13758篇
  1974年   16158篇
  1973年   15434篇
  1972年   14204篇
  1971年   13073篇
  1970年   11929篇
  1969年   11153篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
41.
42.
Pediatric trachyonychia is an acquired nail disease that can cause distress to families. It is a poorly understood disease, and long‐term follow‐up data are lacking. We present an institutional review of 11 children with isolated pediatric trachyonychia followed over time. Children with the diagnosis of pediatric trachyonychia were identified and invited to participate. Pictures were taken on follow‐up and a questionnaire was answered. Exclusion criteria include having another diagnosis at the initial visit that causes nail dystrophy. Eleven patients with the diagnosis of pediatric trachyonychia were available for follow‐up. The mean age of appearance was 2.7 years (range 2–7 yrs) and the average follow‐up was 66 months (range 10–126 mos). Nine patients were treated with potent topical corticosteroids, one used only petrolatum, and one took vitamin supplements. One patient was found to have an additional skin and hair diagnosis of alopecia areata on follow‐up. On follow‐up, 82% noted improvement of the nails, whereas 18% noted no change. A majority of cases of pediatric trachyonychia are isolated and improve with time, regardless of treatment.  相似文献   
43.
Sinus venosus atrial septal defect (SV‐ASD) usually coexists with partial anomalous pulmonary vein connection (PAPVC). It is a difficult diagnosis in transthoracic echocardiography (TTE) due to eccentric position of defects. We present a rare case of atypical anatomical variation in PAPVC, which was never described before. Two right pulmonary veins drained into superior vena cava, which overrode SV‐ASD and interatrial septum, a third pulmonary vein into the right atrium. Complete diagnosis could not be set after TTE, nor transesophageal echocardiography, whereas angio‐CT was finally conclusive. This diagnostic approach allowed the surgical planning.  相似文献   
44.
45.
Analyzing functional species’ characteristics (species traits) that represent physiological, life history and morphological characteristics of species help understanding the impacts of various stressors on aquatic communities at field conditions. This research aimed to study the combined effects of pesticides and other environmental factors (temperature, dissolved oxygen, dissolved organic carbon, floating macrophytes cover, phosphate, nitrite, and nitrate) on the trait modality distribution of aquatic macrofauna communities. To this purpose, a field inventory was performed in a flower bulb growing area of the Netherlands with significant variation in pesticides pressures. Macrofauna community composition, water chemistry parameters and pesticide concentrations in ditches next to flower bulb fields were determined. Trait modalities of nine traits (feeding mode, respiration mode, locomotion type, resistance form, reproduction mode, life stage, voltinism, saprobity, maximum body size) likely to indicate pesticides impacts were analyzed. According to a redundancy analysis, phosphate -and not pesticides- constituted the main factor structuring the trait modality distribution of aquatic macrofauna. The functional composition could be ascribed for 2–4 % to pesticides, and for 3–11 % to phosphate. The lack of trait responses to pesticides may indicate that species may have used alternative strategies to adapt to ambient pesticides stress. Biomass of animals exhibiting trait modalities related to feeding by predation and grazing, presence of diapause form or dormancy, reproduction by free clutches and ovoviviparity, life stage of larvae and pupa, was negatively correlated to the concentration of phosphate. Hence, despite the high pesticide pollution in the area, variation in nutrient-related stressors seems to be the dominant driver of the functional composition of aquatic macrofauna assembly in agricultural ditches.  相似文献   
46.
47.
48.
49.
50.
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