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   29475篇
  免费   2793篇
  国内免费   2365篇
耳鼻咽喉   204篇
儿科学   375篇
妇产科学   324篇
基础医学   3817篇
口腔科学   498篇
临床医学   4021篇
内科学   4889篇
皮肤病学   287篇
神经病学   1475篇
特种医学   1362篇
外国民族医学   22篇
外科学   2972篇
综合类   4459篇
现状与发展   9篇
一般理论   4篇
预防医学   1773篇
眼科学   729篇
药学   2917篇
  31篇
中国医学   1493篇
肿瘤学   2972篇
  2024年   108篇
  2023年   497篇
  2022年   1282篇
  2021年   1642篇
  2020年   1226篇
  2019年   980篇
  2018年   1080篇
  2017年   908篇
  2016年   889篇
  2015年   1390篇
  2014年   1699篇
  2013年   1362篇
  2012年   2011篇
  2011年   2273篇
  2010年   1405篇
  2009年   1118篇
  2008年   1423篇
  2007年   1529篇
  2006年   1421篇
  2005年   1568篇
  2004年   906篇
  2003年   808篇
  2002年   754篇
  2001年   630篇
  2000年   635篇
  1999年   702篇
  1998年   607篇
  1997年   564篇
  1996年   497篇
  1995年   422篇
  1994年   345篇
  1993年   226篇
  1992年   234篇
  1991年   195篇
  1990年   170篇
  1989年   181篇
  1988年   189篇
  1987年   149篇
  1986年   123篇
  1985年   115篇
  1984年   60篇
  1983年   49篇
  1982年   53篇
  1981年   41篇
  1980年   40篇
  1979年   26篇
  1978年   16篇
  1977年   18篇
  1976年   27篇
  1975年   18篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
But PP  Hon PM  Cao H  Che CT 《Planta medica》1996,62(5):474-476
A methanolic extract of the whole plant of Elephantopus mollis was found to contain lupeol, lupeol acetate, epifriedelinol, molephantin, and 2-de-ethoxy-2-methoxyphantomolin, as well as a new sesquiterpene lactone determined to be 2-de-ethoxy-2-hydroxyphantomolin.  相似文献   
72.
艾灸对大鼠胃溃疡模型的影响   总被引:4,自引:2,他引:2  
陈演江  肖德生 《针刺研究》1992,17(2):113-116
<正> 近年来,胃粘膜的保护作用很受人们关注,这方面的研究也取得了显著的进展本文试图用醋酸烧灼胃粘膜面造成大鼠胃溃疡模型,以此为对象,研究艾灸在保护胃粘膜方面可能存在的作用。  相似文献   
73.
Reduced vasodilatory capacity resulting from occlusive lesions of the major cerebral arteries may return to normal without surgical revascularisation. We aimed to determine prospectively the frequency and predictors of recovery of impaired haemodynamics as demonstrated by acetazolamide (ACZ) reactivity on single-photon emission computed tomography (SPECT). Vasoreactivity was measured by 123I-IMP SPECT with an ACZ challenge, in 37 medically treated patients with unilateral occlusive disease of the internal carotid or middle cerebral artery at an interval of 1–2 years. Each ACZ challenge test was analysed semiquantitatively by calculating the degree of increase in cerebral blood flow (CBF) asymmetry after ACZ administration (ΔAI). Vasodilatory capacity was abnormal initially in 20 patients (65 %); eight of whom (40 %) exhibited spontaneous normalisation on follow-up. Although the baseline characteristics did not differ significantly between patients with or without increase in reactivity, logistic regression analysis revealed that the initial ΔAI (P < 0.05) and the type of vascular lesion (stenosis or occlusion) (P < 0.05) correlated significantly with a return towards normal of reduced ACZ reactivity. Spontaneous improvement of impaired vasodilatory capacity may not be a rare phenomenon. We found that mild reduction in the initial ACZ reactivity and a stenosis, but not complete occlusion, were independent factors contributing to normalisation of impaired cerebral haemodynamics. Received: 12 October 1998/Accepted: 27 April 1999  相似文献   
74.
前庭水管扩大综合征患者的人工耳蜗植入术   总被引:19,自引:2,他引:19  
目的 评价前庭水管扩大综合征患者人工耳蜗植入术的安全性和可行性。方法 1995年5月1日~2002年6月1日因双耳重-极重度感音神经性聋在北京协和医院接受人工耳蜗植入术的患者312例中诊断为双耳前庭水管扩大者10例(3.2%),其中语前聋7例,语后聋3例。回顾性分析这10例患者的临床资料。结果 10例患者人工耳蜗电极植入顺利,8例耳蜗底回开窗时发生轻度井喷,迅速用颞肌筋膜牢固封闭圆窗制止井喷。全部患者术后未出现脑脊液漏、颅内感染、面瘫、中耳炎等并发症。开机6个月时8例患者具有开放性言语识别力,已进入普通学校(幼儿园、小学、大学)就读。另2例语前聋的幼儿视觉强化测听听阈达40dB HL,与其他无内耳畸形的全聋儿童术后效果差异无显著性。全聋前语言能力较好的5例患者术后语言能力明显好于语前聋的患者,语言交流基本听不出聋人特有的语音特征。另5例患者语言均有不同程度的进步。结论 尽管前庭水管扩大患者在人工耳蜗植入术中可能出现井喷,但术后未出现并发症且听力-言语康复效果好,因此重-极重度聋的前庭水管扩大综合征患者行人工耳蜗植入术是安全可行的。  相似文献   
75.
韦群  陈瑜  曹福志 《中国药师》2004,7(8):608-609
目的: 建立肝素钠原料药的细菌内毒素检查方法.方法: 通过干扰评价试验,证明肝素钠对细菌内毒素检查有抑制作用,使用稀释剂(I)适当补充二价阳离子,对样品作适当稀释,以消除其干扰抑制作用.结果: 补充适量的二价阳离子可以消除干扰作用.结论: 肝素钠原料药可以建立细菌内毒素检查法.  相似文献   
76.
李萌葆  曹进  徐燕  叶磊 《中国药事》2004,18(2):71-73
结合中美史克公司召回康泰克的经验,浅谈企业药品召回管理规范的制定.  相似文献   
77.
BACKGROUND: Oxalate exposure produces oxidant stress in renal epithelial cells leading to death of some cells and adaptation of others. The pathways involved in these diverse actions remain unclear, but appear to involve activation of phospholipase A2 (PLA2) and redistribution of membrane phospholipids. The present studies examined the possibility that oxalate actions may also involve increased accumulation of ceramide, a lipid-signaling molecule implicated in a variety of pathways, including those leading to apoptotic cell death. METHODS: Ceramide accumulation was examined in renal epithelial cells from pig kidney (LLC-PK1 cells) and from dog kidney [Madin-Darby canine kidney (MDCK cells)] using the diacylglycerol kinase assay. Sphingomyelin degradation was assessed by monitoring the disappearance of 3H-sphingomyelin from cells that had been prelabeled with [3H]-choline. The effects of oxalate were compared with those of other oxidants (peroxide, xanthine/xanthine oxidase), other organic acids (formate and citrate), and a known activator of sphingomyelinase in these cells [tumor necrosis factor-alpha (TNF-alpha)]. Separate studies determined whether oxalate-induced accumulation of ceramide could be blocked by pretreatment with antioxidants [Mn (III) tetrakis (1-methyl-4-pyridyl) porphyrin (Mn TMPyP, a superoxide dismutase mimetic) or N-acetylcysteine (NAC; an antioxidant)], with an inhibitor of ceramide synthase [fumonisin B1 (FB1)] or with an inhibitor of PLA2 [arachidonyl trifluoromethylketone (AACOCF3)]. RESULTS: Oxalate exposure produced a significant time- and concentration-dependent increase in cellular ceramide. A reciprocal decrease in 3H-sphingomyelin was observed under these conditions. Increases in cellular ceramide levels were also observed after treatment with other oxidants (hydrogen peroxide, and xanthine/xanthine oxidase), activators of sphingomyelinase (TNF-alpha), exogenous sphingomyelinase, or arachidonic acid. Formate produced similar (albeit smaller) effects, and citrate did not. The oxidant-induced increases in ceramide were attenuated by pretreatment with NAC (a glutathione precursor) and MnTMPyP (a superoxide dismutase mimetic), suggesting a role for cellular redox states. The oxalate-induced increase in ceramide was also attenuated by pretreatment with AACOCF3, suggesting a role for PLA2. Pretreatment with FB1 produced a small but statistically insignificant attenuation of the response to oxalate. CONCLUSIONS: Oxalate exposure produces a marked accumulation of ceramide in renal epithelial cells by a process that is redox sensitive and mediated in part by activation of PLA2. Since cellular sphingomyelin decreased as ceramide increased, it seems likely that oxalate actions are mediated, at least in part, by an increase in sphingomyelinase activity, although alterations in ceramide synthase are also possible. Further study is required to define the steps involved in oxalate actions and to determine the extent to which ceramide signaling mediates oxalate actions.  相似文献   
78.
79.
The relation between trace element levels in drinking water and cognitive function was investigated in a population-based study of elderly residents (n = 1,016) in rural China in 1996-1997. Cognitive function was measured using a Chinese translation of the Community Screening Interview for Dementia. A mixed effects model was used to evaluate the effect of each of the elements on cognitive function while adjusting for age, sex, and educational level. Several of the elements examined had a significant effect on cognitive function when they were assessed in a univariate context. However, after adjustment for other elements, many of these results were not significant. There was a significant quadratic effect for calcium and a significant zinc-cadmium interaction. Cognitive function increased with calcium level up to a certain point and then decreased as calcium continued to increase. Zinc showed a positive relation with cognitive function at low cadmium levels but a negative relation at high levels.  相似文献   
80.
那法瑞林长效制剂对大鼠垂体功能影响   总被引:1,自引:0,他引:1       下载免费PDF全文
 目的:观察国产那法瑞林(nafarelin )长效制剂的长效作用及对大鼠垂体功能影响,并探讨其作用部位。方法:采用大鼠间质细胞睾酮 (RICT)法检测血清LH(luteinizing hormone)生物活性水平。结果:那法瑞林长效制剂在体内的持续释药时间为((40.0±6.8)d。单次理植3周后大鼠血LH的周期性分泌高峰及激发高峰均消失。预先理植长效制剂组大鼠血LH在切除双侧卵巢后变化不明显。结论:那法瑞林长效制剂确有长效作用,其通过作用于垂体而抑制大鼠垂体功能。  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