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   1855755篇
  免费   140665篇
  国内免费   24251篇
耳鼻咽喉   24896篇
儿科学   53381篇
妇产科学   46447篇
基础医学   257124篇
口腔科学   48126篇
临床医学   173848篇
内科学   360439篇
皮肤病学   37517篇
神经病学   137847篇
特种医学   72333篇
外国民族医学   914篇
外科学   272740篇
综合类   78411篇
现状与发展   76篇
一般理论   447篇
预防医学   125687篇
眼科学   44131篇
药学   148931篇
  302篇
中国医学   19759篇
肿瘤学   117315篇
  2022年   15360篇
  2021年   23940篇
  2020年   16913篇
  2019年   20352篇
  2018年   26052篇
  2017年   20942篇
  2016年   21512篇
  2015年   27377篇
  2014年   36282篇
  2013年   44338篇
  2012年   62163篇
  2011年   67135篇
  2010年   40481篇
  2009年   36294篇
  2008年   57121篇
  2007年   60333篇
  2006年   61025篇
  2005年   59390篇
  2004年   52689篇
  2003年   50870篇
  2002年   48585篇
  2001年   92597篇
  2000年   96437篇
  1999年   83080篇
  1998年   24006篇
  1997年   21857篇
  1996年   20914篇
  1995年   19749篇
  1994年   18155篇
  1993年   16070篇
  1992年   60444篇
  1991年   57970篇
  1990年   55944篇
  1989年   53666篇
  1988年   48977篇
  1987年   47703篇
  1986年   44117篇
  1985年   41971篇
  1984年   30536篇
  1983年   25435篇
  1982年   14187篇
  1979年   26372篇
  1978年   17856篇
  1977年   15236篇
  1976年   13697篇
  1975年   15033篇
  1974年   17475篇
  1973年   16750篇
  1972年   15556篇
  1971年   14275篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
123.
Birth weight on 12,644 singleton infants from 6,196 sibships born in Maryland between 1980 and 1984 were used to estimate the effects of nine maternal and infant covariates on the sibship correlation in birth weight. Assuming a homogeneous correlation across all families, the estimated intraclass correlation was 0.4664 (+/- 0.0099). This high sibship correlation makes it possible to predict, with reasonable accuracy, the birth weight of a child given information on previous sibs, as well as covariates on the mother and/or infant pertinent to a given pregnancy. The reduction in variance associated with incorporating information on the nine covariates used here was approximately equal to that obtained by conditioning on a single previous sib. Testing for heterogeneity in correlation among different groups of families showed that a crude measure of parity (first live birth vs. other), time between births, mother's marital status, and maternal age at the birth of the last child significantly influenced the sibship correlation in birth weight.  相似文献   
124.
This study was conducted to follow up healthy subjects from a previous study (Warwick & Williams, 1987) in which favourable dietary changes were achieved during 1 week immediately after dietary advice but were accompanied by reduced energy intakes and weight loss. Twenty-one subjects (8m, 13f; 57 per cent of the original group) participated in the follow-up study. Dietary intakes were measured using 7-d weighed records on three occasions: before, immediately after and 1 year after receiving dietary advice. Intakes 1 year after dietary advice continued to show some of the favourable changes observed immediately after the advice but were not accompanied by reduced energy intakes and weight loss. Intakes before, immediately after, and 1 year after dietary advice respectively were: energy, 9.0, 7.8 and 8.9 MJ/d (2150, 1860 and 2120 kcal/d); fat, 36.9, 32.9 and 31.5 per cent of total energy; carbohydrate, 44.2, 47.9 and 49.6 per cent of total energy; dietary fibre, 32, 36 and 36 g/d; sodium, 116, 97 and 110 mmol/d; and Na:K ratio, 1.4, 1.2 and 1.2 mmol. Nutrient densities for fibre and most micronutrients tended to be higher 1 year after dietary advice than before, but were highest immediately after the advice. Nutrient densities for sodium and total sugars did not vary between the 3 study weeks. It was concluded that our healthy subjects adapted their intakes to maintain energy balance while retaining favourable dietary changes for at least 1 year after dietary advice.  相似文献   
125.
Eledoisin has been tried as a possible treatment for dry eye based on the hypothesis that it pharmacologically stimulates tear secretion when topically applied to the eye. To determine if topically applied eledoisin pharmacologically stimulates orbital lacrimal secretion, the orbital lacrimal gland excretory duct of normal rabbits was cannulated, and eledoisin was applied topically with and without prior administration of proparacaine. To determine if topically applied eledoisin stimulated accessory lacrimal gland secretion, isotonic buffer with and without eledoisin was tested in a rabbit model with only accessory lacrimal tissue remaining after the administration of proparacaine. Topically applied eledoisin did not pharmacologically stimulate lacrimal secretion but rather increased lacrimal gland secretion only in non-anesthetized eyes through a sensory reflex mechanism that is blocked by proparacaine.  相似文献   
126.
人体蠕形螨的生物学研究   总被引:4,自引:0,他引:4  
用透明胶带法观察蠕形螨在人体面部的寄生、逸出及其在体外的存活能力。结果表明:毛囊蠕形螨(Demod-exfoliculorum,D.f.)主要以颚体朝向毛囊底部寄生,且常常有多条群居现象,而皮脂蠕形螨,(Demodexbrevis,D.b.)一般为单条独居生活。两种人体蠕形螨昼夜均可主动爬出毛囊口出现在皮肤表面,D.f.以白天1000~1800为逸出高峰;D.b.则以夜间2200~200逸出最多。此外,蠕形螨在体外有较强的活动力和存活力。透明胶带法在人体蠕形螨的流行病学调查和生物学研究方面具有较高的应用价值  相似文献   
127.
Transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (TES) of the human motor cortex produce a silent period (SP) following motor evoked potentials (MEPs). The early part of the SP can be explained by decreased alpha motor neuron excitability, whereas the late part is presumably due to suprasegmental mechanisms. In order to determine the level of the suprasegmental contribution to the generation of SPs, we recorded excitatory and inhibitory responses to TMS, TES, and percutaneous electrical brainstem stimulation (PBS) in the voluntarily activated first dorsal interosseous muscle of the hand. Stimulus intensities were set so that PBS and TES induced MEPs with areas equal to or larger than those of MEPs obtained with TMS. This procedure revealed that SPs were 49% and 83% shorter with TES and PBS, respectively, than with TMS. As TMS is more effective than TES or PBS in activating cortical interneurons, these findings support the idea that a significant component of the SP arises from intracortical mechanisms.  相似文献   
128.
Six patients who injured their wrists had radiographs documenting a dorsal, 5- to 10-mm oblong fragment of bone immediately proximal to the base of the fourth and/or fifth metacarpal bones. The fragment was seen on the pronation oblique and/or lateral projections, but not on the posteroanterior projection. The radiographic appearance of the fragment was remarkably similar in all cases. In the one patient in which it was performed, pluridirectional tomography demonstrated that the fragment originated from the dorsal surface of the hamate. Five of the six patients also had associated posterior dislocation of the fourth and/or fifth metacarpals. We conclude that this fragment represents a coronal fracture through the body of the hamate resulting from posterior dislocation or subluxation of the fourth and/or fifth metacarpal.  相似文献   
129.
Case report 506   总被引:1,自引:0,他引:1  
  相似文献   
130.
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