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   405706篇
  免费   28893篇
  国内免费   11450篇
耳鼻咽喉   4167篇
儿科学   11139篇
妇产科学   6812篇
基础医学   32070篇
口腔科学   8443篇
临床医学   43351篇
内科学   59390篇
皮肤病学   4819篇
神经病学   20281篇
特种医学   10413篇
外国民族医学   47篇
外科学   44076篇
综合类   64153篇
现状与发展   31篇
一般理论   33篇
预防医学   38783篇
眼科学   5609篇
药学   37096篇
  464篇
中国医学   38011篇
肿瘤学   16861篇
  2023年   6532篇
  2022年   10094篇
  2021年   16011篇
  2020年   15041篇
  2019年   20540篇
  2018年   18141篇
  2017年   15402篇
  2016年   13369篇
  2015年   12362篇
  2014年   24461篇
  2013年   25735篇
  2012年   22222篇
  2011年   24605篇
  2010年   20028篇
  2009年   17929篇
  2008年   17390篇
  2007年   17982篇
  2006年   16103篇
  2005年   13786篇
  2004年   11087篇
  2003年   9778篇
  2002年   7803篇
  2001年   7021篇
  2000年   5781篇
  1999年   4981篇
  1998年   4174篇
  1997年   3905篇
  1996年   3418篇
  1995年   3205篇
  1994年   3083篇
  1993年   2455篇
  1992年   2462篇
  1991年   2090篇
  1990年   1888篇
  1989年   1638篇
  1988年   1551篇
  1987年   1321篇
  1985年   4008篇
  1984年   5013篇
  1983年   3487篇
  1982年   3981篇
  1981年   3697篇
  1980年   3296篇
  1979年   3025篇
  1978年   2650篇
  1977年   2000篇
  1976年   2250篇
  1975年   1682篇
  1974年   1474篇
  1973年   1310篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
991.
镉对肾脏的毒作用   总被引:6,自引:0,他引:6  
雄性Wistar大鼠24只,随机等分为4组,皮下注射不同剂量的CdMT。结果显示镉接触组尿钙和尿蛋白都高于对照组;肾皮质钠泵和钙泵活性低于对照组,体外试验也显示镉能抑制钙泵活性,GSH和半胱氨酸对这种抑制有保护作用;肾皮质GSH含量低于对照组,MDA含量则高于对照组,但肝脏的这两个指标无变化;高剂量组cAMP/cGMP的比值低于对照组。提示脂质过氧化和钙代谢障碍是镉引起肾损害的机理之一。  相似文献   
992.
993.
本实验采用记录翻转小肠和结肠囊葡萄糖转运电位的方法,来研究大黄泻下作用的有效成分大黄总甙、大黄素和番泻甙对小肠及结肠囊跨肠壁电应差的变化,发现上述成分可阻止葡萄糖和Na~+的转运,这一结果为进一步阐明大黄泻下作用的原理提供新的理论依据。  相似文献   
994.
在连续361例患者心内电生理检查中,发现4例有心脏传导的裂隙现象。其特点表现为激动传导方向上远端平面相对不应期(RRP)长,程序刺激中先出现传导延缓,随后近端平面也进入RRP使传导变为延缓,激动经过近端平面延缓传导后,到达远端平面时其已脱离了RRP,使已经在远端传导延缓的情况变为传导正常,与经典的裂隙现象相比,这种裂隙现象的发生机制,与心内电图的表现均有不同,暂定名为变异性裂隙现象。  相似文献   
995.
Abstract The aim of this study was to describe the periodontal conditions in 372 35–44-yr-old and 537 noninstitutionalized 65–74-yr-old Hong Kong Chinese who were examined clinically for loss of attachment, recession, probing depth, calculus, and bleeding after probing. Community Periodontal Index (CPI) data and treatment need indications were compiled from index teeth or their substitutes. The prevalence of loss of attachment varied considerably in both cohorts according to the definition of the threshold (≥6, ≥9, and ≥12 mm, respectively). The mean numbers of teeth with loss of attachment at the ≥6-mm threshold and at higher thresholds were small. In both age cohorts, about one-fifth of subjects had probing depths ≥6-mm, while al the ≥9-mm threshold only 2–3% were so affected. Although recession was an important component of loss of attachment in the younger cohort, in the older cohort the prevalence and extent of recession were greater than for probing depths at thresholds ≥4 mm. All subjects had one or more teeth with calculus, bleeding, or both, most teeth being so affected. Eighty-four of the 537 65–74-yr-old subjects were excluded either because of edentulousness or because extractions indicated for the remaining teeth would have rendered the subjects edentulous. The distribution of subjects according to their highest CPI score was remarkably similar for the two cohorts. No subjects in either age group were assessed as “healthy” (CPI code 0) or had “bleeding only” (code 1) as their highest score. While most subjects scored CPI code 2 or 3 us their highest score, only 17% of the younger and 15% of the older cohort scored Community Periodontal Index of Treatment Needs (CPITN) code 4. Differences in the mean number of sextants affected by CPI codes between the two cohorts were mainly due to a greater number of excluded sextants in the older cohort. CPI findings for 35–44-yr-olds differed little from those reported in 1984.  相似文献   
996.
根据热分析谱图峰顶的数学特征与Coats-Redfern方程,推得在一定实验条件下,在系列相关反应中,若峰顶温度相接近,则各反应的表观活化能E与指前因子A之间存在着有动力学意义的补偿效应,即lnA=aE+b。并经系列含水硫酸盐脱水反应实验验证。  相似文献   
997.
The morphological types of ganglion cells in the dog and wolf retina were studied by intracellular staining with Lucifer Yellow. These retinae contain a range of ganglion cell types that closely correspond to those found in cat retina: alpha cells with large somata and large, relatively densely branched dendritic trees; beta cells with medium-sized somata and small, densely branched dendritic trees; and a variety of other types with smaller somata and varying dendritic branching patterns and dendritic field sizes. The correspondence of canine and cat ganglion cell types strengthens the view that there is a common set of ganglion cell types in carnivores. Alpha and beta cell dendritic trees of dog and wolf are monostratified in either the inner or the outer part of the inner plexiform layer, suggesting an on/off dichotomy in the response to light. Dendritic field sizes of dog alpha and beta cells increase from the central area to peripheral retina: alpha cell fields from 160-200 microns to about 1,100 microns diameter, and beta cell fields from 25 microns to about 360 microns diameter. These sizes are quantitatively very similar to those found in cat retina. The close qualitative and quantitative morphological correspondence of cat and dog ganglion cells suggests that they are also functionally very similar. It is likely that dog alpha cells have brisk-transient (Y), and dog beta cells brisk-sustained (X) concentric receptive fields. From the smallest beta cell sizes it is concluded that the visual acuity of the dog may be as good as that of the cat.  相似文献   
998.
999.
乳必泰胶囊药效学研究   总被引:2,自引:0,他引:2  
方敏  李茂  韦宝伟 《广西医学》2003,25(11):2133-2136
目的:探讨乳必泰胶囊的药效学。方法:通过大鼠乳腺增生模型及其它试验观察本品对乳腺增生的抑制作用及其它药理作用。结果:乳必泰胶囊能明显抑制乳腺组织增生,降低血清雌二醇水平,减少乳头直径及子宫系数,能明显抑制角叉菜胶引起的足肿胀。结论:这些作用说明乳必泰胶囊用于治疗乳腺增生,可能对患的症状有一定缓解作用。  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