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   1529篇
  免费   69篇
  国内免费   22篇
耳鼻咽喉   9篇
儿科学   26篇
妇产科学   20篇
基础医学   112篇
口腔科学   23篇
临床医学   338篇
内科学   221篇
皮肤病学   13篇
神经病学   107篇
特种医学   61篇
外科学   246篇
综合类   181篇
预防医学   70篇
眼科学   29篇
药学   104篇
  1篇
中国医学   37篇
肿瘤学   22篇
  2023年   12篇
  2022年   38篇
  2021年   64篇
  2020年   42篇
  2019年   29篇
  2018年   44篇
  2017年   48篇
  2016年   50篇
  2015年   61篇
  2014年   104篇
  2013年   108篇
  2012年   87篇
  2011年   111篇
  2010年   69篇
  2009年   89篇
  2008年   95篇
  2007年   77篇
  2006年   87篇
  2005年   56篇
  2004年   46篇
  2003年   34篇
  2002年   38篇
  2001年   28篇
  2000年   19篇
  1999年   14篇
  1998年   12篇
  1997年   18篇
  1996年   8篇
  1995年   14篇
  1994年   14篇
  1993年   8篇
  1992年   9篇
  1991年   8篇
  1990年   9篇
  1989年   8篇
  1988年   4篇
  1987年   3篇
  1986年   3篇
  1985年   3篇
  1984年   7篇
  1983年   7篇
  1982年   5篇
  1981年   5篇
  1980年   4篇
  1979年   6篇
  1978年   2篇
  1977年   3篇
  1976年   2篇
  1974年   4篇
  1973年   2篇
排序方式: 共有1620条查询结果,搜索用时 15 毫秒
31.
32.
A 41-year-old female was diagnosed with retinitis pigmentosa (RP) after bilateral implantation of multifocal intraocular lenses (IOLs). Due to persistent dissatisfaction with her visual performance, she came to our hospital for medical help. We exchanged the multifocal IOL in the dominant eye with a monofocal IOL (hybrid monovision therapy), and the visual inconvenience was alleviated to a large extent. To our knowledge, this is the first case report on the effect of hybrid monovision therapy applied to a patient with RP.  相似文献   
33.
《Medical image analysis》2014,18(5):711-724
Blood Oxygen Level Dependent (BOLD) functional magnetic resonance imaging (fMRI) maps the brain activity by measuring blood oxygenation level, which is related to brain activity via a temporal impulse response function known as the Hemodynamic Response Function (HRF). The HRF varies from subject to subject and within areas of the brain, therefore a knowledge of HRF is necessary for accurately computing voxel activations. Conversely a knowledge of active voxels is highly beneficial for estimating the HRF. This work presents a joint maximum likelihood estimation of HRF and activation based on low-rank matrix approximations operating on regions of interest (ROI). Since each ROI has limited data, a smoothing constraint on the HRF is employed via Tikhonov regularization. The method is analyzed under both white noise and colored noise. Experiments with synthetic data show that accurate estimation of the HRF is possible with this method without prior assumptions on the exact shape of the HRF. Further experiments involving real fMRI experiments with auditory stimuli are used to validate the proposed method.  相似文献   
34.
目的 探讨右美托咪定在颅内动脉瘤介入手术全身麻醉诱导期减少血流动力学波动中的应用.方法 选择全身麻醉下行颅内动脉瘤介入手术的患者60例,采用随机数字表法分为低剂量芬太尼组、高剂量芬太尼组和低剂量芬太尼复合右美托咪定组(复合组),每组20例.麻醉诱导前,复合组经微量泵持续静脉注射右美托咪定,总量1μg/kg,泵注时间10 min;低剂量芬太尼组和高剂量芬太尼组注射等量0.9%氯化钠.麻醉诱导时,低剂量芬太尼组和复合组静脉注射芬太尼3μg/kg、高剂量芬太尼组静脉注射芬太尼5μg/kg,余用药相同.记录入手术室平静休息3 min (T0)、气管内插管前即刻(T1)、插管后即刻(T2)、插管后3 min (T3)的收缩压(SBP)、舒张压(DBP)、心率(HR).将每例患者麻醉诱导期间(T0~T3)SBP、DBP、HR最大值与最小值之差定义为各参数的波动值:△SBP、△DBP、△HR.记录诱导期间麻黄碱、阿托品的使用情况.结果 复合组△SBP、△DBP、△HR[(26.9±14.8) mm Hg(1 mm Hg =0.133 kPa)、(10.7±8.9) mm Hg、(12.5±4.3)次/min]均低于低剂量芬太尼组[(40.4±15.6) mm Hg、(20.3±9.4) mm Hg、(30.1±15.0)次/min](P< 0.05),高剂量芬太尼组△SBP、△HR [(29.8±16.8) mm Hg、(19.5±7.4)次/min]均低于低剂量芬太尼组(P<0.05),复合组△HR低于高剂量芬太尼组(P<0.05).麻醉诱导期三组阿托品使用率比较差异无统计学意义(P=0.364),高剂量芬太尼组麻黄碱使用率高于低剂量芬太尼组[30%(6/20)比5%(1/20),P=0.032].结论 麻醉诱导前应用1μg/kg右美托咪定,既能够良好抑制插管反应,又不会导致插管后血压严重下降,达到了稳定血流动力学的目标,特别适用于颅内动脉瘤患者的麻醉诱导.  相似文献   
35.
Electrical brain stimulations (EBS) sometimes induce reminiscences, but it is largely unknown what type of memories they can trigger. We reviewed 80 years of literature on reminiscences induced by EBS and added our own database. We classified them according to modern conceptions of memory.We observed a surprisingly large variety of reminiscences covering all aspects of declarative memory. However, most were poorly detailed and only a few were episodic. This result does not support theories of a highly stable and detailed memory, as initially postulated, and still widely believed as true by the general public.Moreover, memory networks could only be activated by some of their nodes: 94.1% of EBS were temporal, although the parietal and frontal lobes, also involved in memory networks, were stimulated. The qualitative nature of memories largely depended on the site of stimulation: EBS to rhinal cortex mostly induced personal semantic reminiscences, while only hippocampal EBS induced episodic memories. This result supports the view that EBS can activate memory in predictable ways in humans.  相似文献   
36.
比较右室双部位 (RV Bi)起搏和双室 (BiV)同步起搏对血液动力学的影响 ,并与右室心尖部 (RVA)、右室流出道 (RVOT)、左室基底部 (LVB)起搏相比较 ,明确双部位起搏是否优于单部位起搏。 15例患者中病窦综合征 8例、Ⅲ度房室阻滞 7例。分别行RVA、RVOT、LVB、RV Bi、BiV起搏 (VVI,6 0~ 90次 /分 ) ,测定心输出量 (CO)和心脏指数(CI)、肺毛细血管嵌顿压 (PCWP)和QRS波时限 (QRSd)。结果 :①与RVA起搏相比 ,RVOT、LVB、RV Bi、BiV起搏CI分别增加了 7.5 %、11.3%、15 .5 %和 17.2 % ,PCWP分别降低了 14.9%、10 .3%、2 1.7%和 2 0 .0 % (P均 <0 .0 1)。②RV Bi、BiV起搏较RVOT、LVB起搏的CO、CI增高而PCWP降低 (P均 <0 .0 5 )。③RV Bi与BiV起搏、RVOT与LVB起搏之间CO、CI和PCWP无显著差异。④RVOT、RV Bi、BiV起搏的QRSd(分别为 12 8± 11,111± 16 ,10 3± 13ms)较RVA起搏 (146± 18ms)时显著缩短 (P≤ 0 .0 0 1) ,而LVB起搏 (142± 15ms)与RVOT、RVA起搏时无显著差异。结论 :RV Bi起搏和BiV同步起搏的急性血液动力学效果无明显差异 ,但双部位起搏的效果明显优于单部位起搏 ;双部位起搏的QRSd也比单部位起搏明显缩短  相似文献   
37.
中国和希腊,看似遥远的两个国家在古代哲学思想方面却近乎一致。古人一直在探寻自然现象的本质问题,并一直在试图回答这些系统联系的基础。在诸多问题中,他们最感兴趣的是天体运动,健康与疾病的相互关系,以及物质运动的原理。通过探究两种不同文化背景基础哲学理论的异同。  相似文献   
38.
The objective of this study was to assess the degree of concordance between two popular classification systems [the Centers for Disease Control and Prevention (CDC)‐2000 and the Institute of Medicine (IOM)‐2009] used to categorise the nutritional status of pregnant adolescents. This cross‐sectional study involved 327 pregnant adolescents (10–19 years) booking for antenatal care at a single public maternity in São Paulo, Brazil. Participants were classified into one of four categories, by both systems according to their pre‐pregnancy body mass index and age. The CDC‐2000 system classified significantly fewer pregnant adolescents as underweight (3.7% vs. 12.5%, P < 0.0001) and significantly more adolescents as normal‐weight (86.8% vs. 75.6%, P = 0.0003) than the IOM‐2009 system. The distribution of the adolescents in the two systems differed significantly. The global rate of discordance was 13.5%. The overall concordance between the two systems was marginally good (K = 0.63), being moderate for younger (<16 years) adolescents (K = 0.52). Approximately one in every seven pregnant adolescent would be classified in a non‐corresponding category if the IOM‐2009 classification was used instead of the CDC‐2000 classification. The IOM‐2009 nutritional classification, which does not take into account age and gender, tends to overestimate the proportion of underweight adolescents, especially in the younger‐age group. The use of this classification system can lead to recommendations of higher gestational weight gain in a substantial proportion of pregnant adolescents, which could predispose to post‐partum weight retention and future obesity.  相似文献   
39.
40.
Objective To observe the effects of dopamine in different doses on hemodynamics and cerebral oxygen metabolism in the early stage of post-resuscitation in rabbit with cardiac arrest. Methods Healthy adult rabbits were randomly(random number) divided into 4 groups according to the different doses of dopamine administration: control group (CG), low dose group (LG), medium dose group (MG), high dose group (HG), (n=15 in each group). Ventricular fibrillation (VF) was induced by electricity and cardiopulmonary resuscitation (CPR) was performed subsequently as the experiment designed. When 10 rabbits with restoration of spontaneous circulation (ROSC) were got each group, it was enough for experiment carried out. Cardiac output (CO), mean arterial pressure (MAP), heart rate (HR), systemic vascular resistance index (SVRI) and the cerebral local tissue blood oxygen saturation (TOI) were observed at 0 min, 15 min, 30 min, 60 min, 120 min after ROSC. The animals were sacrificed at 120 min after ROSC, brain tissues were harvested for study by using HE staining. Repeated measure analysis of variance was used to determine the statistical significance among the four groups at different intervals. Multi-group quantitative data was analyzed by one way ANOVA and then further by LSD test for multiple comparisons. Chi-square test or Fisher's exact probabilities was applied for multi-group binomial classification variable. Log-rank test was used for comparisons of survival curves in four groups. A two-tailed value of P<0.05 was considered statistically significant. Results There were no differences in the rate of ROSC among groups. Compared with CG and LG, ROSC time was shorter in MG (27715 vs. 19012, PO.01 ; 25216 vs. 19012, P=0.016 ) with higher 120 min survival rate ( 20% vs. 90%,∗2=9.899, P=0.005; 30% vj. 90%,∗2=7.5, P=0.02) . CO was higher in MG than that in other groups at all given intervals in the early stage of post-resuscitation(P<0.05). MAP levels were significantly higher in MG and HG compared with CG and LG at given intervals 15 min after ROSC (P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