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   342655篇
  免费   22649篇
  国内免费   7607篇
耳鼻咽喉   4093篇
儿科学   9620篇
妇产科学   6606篇
基础医学   27814篇
口腔科学   8073篇
临床医学   38180篇
内科学   42940篇
皮肤病学   4628篇
神经病学   19530篇
特种医学   7951篇
外国民族医学   32篇
外科学   36647篇
综合类   50686篇
现状与发展   13篇
一般理论   30篇
预防医学   35720篇
眼科学   5308篇
药学   30349篇
  384篇
中国医学   30689篇
肿瘤学   13618篇
  2024年   1138篇
  2023年   5605篇
  2022年   9886篇
  2021年   13500篇
  2020年   12500篇
  2019年   18349篇
  2018年   16014篇
  2017年   12880篇
  2016年   10386篇
  2015年   9732篇
  2014年   19864篇
  2013年   21491篇
  2012年   18188篇
  2011年   19722篇
  2010年   15842篇
  2009年   14536篇
  2008年   14189篇
  2007年   14627篇
  2006年   12779篇
  2005年   11090篇
  2004年   9016篇
  2003年   7938篇
  2002年   6221篇
  2001年   5595篇
  2000年   4623篇
  1999年   4007篇
  1998年   3240篇
  1997年   3103篇
  1996年   2680篇
  1995年   2585篇
  1994年   2485篇
  1993年   1986篇
  1992年   2014篇
  1991年   1737篇
  1990年   1549篇
  1989年   1377篇
  1988年   1310篇
  1985年   3787篇
  1984年   4796篇
  1983年   3348篇
  1982年   3803篇
  1981年   3548篇
  1980年   3160篇
  1979年   2904篇
  1978年   2535篇
  1977年   1909篇
  1976年   2150篇
  1975年   1631篇
  1974年   1431篇
  1973年   1278篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
43.
While much time has been spent deliberating about the definition of play, little emphasis has been placed on what children themselves perceive as play. The aim of the present study was to examine social context as a cue for children's perceptions of play and learning. Ninety-two children aged between four and six years (mean four years nine months) participated in the study and completed the Activity Apperception Story Procedure. Children were asked to sort photographic stimuli into those they believed depicted play/not play and learning/not learning. Each of the stimuli were identified by independent raters as containing one of the following social cues; teacher absence (solitary activity, parallel activity or cooperative activity) or teacher presence (teacher involved activity or teacher directed activity). Findings revealed that children associated teacher absence with play. More specifically, children made links between play and the presence of peers (parallel and cooperative activity). Findings are discussed in relation to play in the early years curriculum, differences in children's early educational experiences and the importance of understanding children's perceptions of play.  相似文献   
44.
本文应用核磁共振法(NMR)测定了几种混合体系的 HLB 值与混合体系中各组分的 HLB 值。实验结果表明,混合体系中各组分在核磁共振图谱中的积分曲线高度也具有加和性。混合体系的 HLB 值是体系中各组分 HLB 值的加权平均值。因此,对混合体系的 HLB 值可以应用 NMR 法直接测定,也可应用 NMR 法测定各组分的 HLB值,通过计算求得,计算值与实测值完全一致。  相似文献   
45.
Summary Aspergillosis belongs to the group of mycotic diseases of paranasal sinuses. The invasive forms, and particularly the fulminant forms, are potentially fatal. Isolated aspergillosis of the sphenoid sinus or the clivus is a difficult diagnosis, since the often misleading clinical manifestations of this rare disease develop late. These patients become apparent by neurological signs such as cavernous sinus syndrome, pseudotumor of the pituitary or the orbit. Diagnosis is often made intra-operatively or on histological examination. We report a case of invasive aspergillosis uniquely involving the sellar area revealed by clinical features suggesting a pseudotumor of the pituitary. Although such lesions are almost always seen in immune suppressed subjects, in our case, the patient was immune competent and had no past history of sinusitis. The question of whether, and when to perform limited or extensive surgery remains an issue for discussion, owing to the rarity of this disease honed by lack of experience. It depends on several factors: the kind of disease, the immunity, the subtype of invasive fungal sinusitis and the degree of tissue invasion.  相似文献   
46.
X Dong  M He  X Song  B Lu  Y Yang  S Zhang  N Zhao  L Zhou  Y Li  X Zhu  R Hu 《Diabetic medicine》2007,24(12):1482-1486
AIMS: Our aim was to assess performances of the Cockcroft-Gault and simplified Modification of Diet in Renal Disease (MDRD) formulae in estimating glomerular filtration rate (GFR) in Chinese diabetic populations and their association with vascular risks. METHODS: A total of 1009 patients with Type 2 diabetes were categorized into low estimated GFR groups (GFR < 60 ml/min/1.73 m(2)) and control groups by the two equations. The performances of these formulae were assessed at different stages of kidney function. Carotid artery intima-media thickness (IMT) and the prevalence of diabetic retinopathy or albuminuria were compared among the groups. The ability of these formulae to identify established vascular risk markers using sensitivity, specificity, positive and negative predictive values were also compared. RESULTS: The prevalence of low estimated GFR was 32.7% with the Cockcroft-Gault formula and 5.2% with the MDRD formula, respectively. In low estimated GFR subjects by the MDRD formula, IMT was significantly thicker than those by the Cockcroft-Gault formula (1.2 mm vs. 1.0 mm; P < 0.05), with a higher prevalence of albuminuria (78.4 vs. 52.8%, P < 0.05) and diabetic retinopathy (46.5 vs. 30.5%; P < 0.05). The Cockcroft-Gault formula gave a specificity of 71.7% and a sensitivity of 37.0%, and the MDRD formula gave a specificity of 96.6% and a sensitivity of 7.9% in estimating low GFR relevant for established vascular risks. CONCLUSIONS: These formulae performed differently in Chinese diabetic populations. The simplified MDRD formula is minimally superior to the Cockcroft-Gault formula for its high specificity and positive predictive values in estimating low GFR relevant for vascular risks.  相似文献   
47.
Femoral and lateral cutaneous nerve of the thigh blocks have been performed in a group of 50 children; the method has not previously been described in paediatric practice. The technique was judged to have been successful in 48 (96%) of the children. There were no early or late complications. It is concluded that these blocks are easy to perform, even in small children and infants, and that they can produce reliable postoperative analgesia for a variety of orthopaedic and plastic procedures.  相似文献   
48.
以曼氏血吸虫的虫卵和成虫免疫家兔后所产生的特异性抗体,可用以日本血吸虫虫卵、尾蚴和成虫为抗原分别进行的COP,CHR和ELACIEP测出,表明两种人体血吸虫存有显著的交叉抗原成分。应用此种血清交叉反应性,以检测抗异种人体血吸虫的抗体,似有效而可取的,可用以辅助诊断援外回国人员是否感染国外人体血吸虫病。  相似文献   
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