全文获取类型
收费全文 | 3209篇 |
免费 | 217篇 |
国内免费 | 38篇 |
专业分类
耳鼻咽喉 | 25篇 |
儿科学 | 38篇 |
妇产科学 | 8篇 |
基础医学 | 608篇 |
口腔科学 | 84篇 |
临床医学 | 257篇 |
内科学 | 538篇 |
皮肤病学 | 18篇 |
神经病学 | 582篇 |
特种医学 | 109篇 |
外科学 | 273篇 |
综合类 | 280篇 |
预防医学 | 142篇 |
眼科学 | 32篇 |
药学 | 385篇 |
1篇 | |
中国医学 | 64篇 |
肿瘤学 | 20篇 |
出版年
2023年 | 45篇 |
2022年 | 64篇 |
2021年 | 118篇 |
2020年 | 116篇 |
2019年 | 94篇 |
2018年 | 75篇 |
2017年 | 84篇 |
2016年 | 77篇 |
2015年 | 103篇 |
2014年 | 162篇 |
2013年 | 191篇 |
2012年 | 143篇 |
2011年 | 171篇 |
2010年 | 157篇 |
2009年 | 153篇 |
2008年 | 136篇 |
2007年 | 150篇 |
2006年 | 131篇 |
2005年 | 99篇 |
2004年 | 90篇 |
2003年 | 107篇 |
2002年 | 89篇 |
2001年 | 70篇 |
2000年 | 56篇 |
1999年 | 49篇 |
1998年 | 62篇 |
1997年 | 46篇 |
1996年 | 40篇 |
1995年 | 53篇 |
1994年 | 49篇 |
1993年 | 45篇 |
1992年 | 36篇 |
1991年 | 38篇 |
1990年 | 32篇 |
1989年 | 34篇 |
1988年 | 26篇 |
1987年 | 33篇 |
1986年 | 23篇 |
1985年 | 27篇 |
1984年 | 34篇 |
1983年 | 22篇 |
1982年 | 27篇 |
1981年 | 24篇 |
1980年 | 16篇 |
1979年 | 20篇 |
1978年 | 14篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1975年 | 9篇 |
1973年 | 3篇 |
排序方式: 共有3464条查询结果,搜索用时 15 毫秒
1.
糖尿病视网膜病变(DR)作为常见的糖尿病并发症之一,是导致失明的主要原因。传统上,DR主要被认为是一种微血管疾病,随着研究的进展,目前认为神经-胶质-血管单元(NVU)破坏及其耦联机制(coupling)失衡在DR发病的早期起到了关键作用。了解NVU的细胞和分子基础,以及糖尿病如何改变正常的细胞通讯和破坏细胞环境,对DR的早期防治具有重要的意义。本文总结视网膜NVU及其参与DR发病分子机制,基于视网膜NVU修复的DR治疗,并对DR未来发展前景及问题进行探讨。 相似文献
2.
如何准确、合理地衡量中枢神经系统调控下的肌间耦合关系,是一个富有挑战性的研究课题。在时变copula函数的基础上,通过与熵理论相结合,提出一种时变copula互信息估计方法,并将其应用于10名被试腕屈、腕展运动过程中,肱二头肌(BB)和肱三头肌(TB)记录的表面肌电(sEMG)信号在theta、alpha、beta等特征频段的耦合分析,同时对照静态copula函数验证其有效性,所用数据源自Ninapro DB4。实验结果表明,较之静态copula函数,时变copula函数对肌间相依结构的拟合优度更高,由时变copula互信息描述的肌间耦合强度存在显著的频段差异(P<0.05),具体表现为频段越高肌间耦合强度越低(腕屈:0.075 7~0.214 7 bit;腕展:0.078 0~0.237 3 bit),而静态copula互信息严重地低估肌间耦合强度。时变copula互信息为肌间耦合分析提供一种先进的理论指导方法,具有广阔的应用前景。 相似文献
3.
为了治疗药物难治性癫痫,提出一种无线闭环迷走神经刺激器及系统,包括头戴式头皮脑电记录器、迷走神经刺激器、电磁耦合能量发射器和控制应用App,设计一种可以分离局部场电位和动作电位的生物信号前置放大器,一种刺激脉冲参数可调的迷走神经刺激器,一种电磁耦合能量发射器以及一个控制应用App。使用海岸线参数检测算法判定癫痫脑电信号的产生。测试结果表明,生物信号前置放大器对局部场电位和动作电位的放大增益分别为40和60 dB。迷走神经刺激器接收到来自控制应用App的刺激参数后,可以产生对应参数的双极性刺激脉冲。当发射器发射功率为30 dBm,发射线圈和接收线圈距离2 cm时,电磁耦合能量传输效率最大为15.4%。海岸线参数算法的正检率为88%。 相似文献
4.
5.
目的 调查复数菌与单菌血流感染患者的临床特征及预后的影响因素。方法 回顾性分析某三甲医院2017年1月-2021年12月临床和病原学确诊的血流感染患者的病历资料,依据检出病原菌种数分为单菌组和复数菌组,研究结局为住院期间全因死亡率。比较两组患者的临床特征及复数菌患者预后的影响因素。结果 共有430例患者血培养阳性。单菌血流感染367例(85.3%),复数菌血流感染63例(14.7%)。复数菌组患者医院感染所占比率较单菌组高(76.2% VS 56.9%),差异有统计学意义(P=0.003);复数菌组患者下呼吸道感染比率较单菌组高(44.4% VS 29.2%),差异有统计学意义(P=0.018)。复数菌组患者住院时间较单菌组高[24(16~39) VS 19(13~26) d],差异有统计学意义(P=0.002)。复数菌组患者病死率高于单菌组(12.7% VS 3.8%),且住院时间延长,差异均有统计学意义(均P<0.05)。多因素分析显示,复数菌感染(OR=3.24,95%CI:1.20~8.75)、消化道肿瘤(OR=3.28,95%CI=1.21~8.84)、有创机械通气(OR=3.40,95%CI=1.22~9.42)、深静脉置管(OR=2.76,95%CI=1.00~7.64)、留置导尿管(OR=3.28,95%CI=1.04~10.40)是血流感染患者死亡的独立危险因素。相较于单菌组,复数菌组送检时间至出院时间间隔显著延长[20(15~36) d VS 16(10~22) d,P<0.001]。单菌组与复数菌组患者检出的金黄色葡萄球菌、溶血葡萄球菌和大肠埃希菌的构成比较,差异均有统计学意义(均P<0.05)。结论 住院患者复数菌血流感染死亡风险显著增加,消化道肿瘤、有创机械通气、深静脉置管、留置导尿管是血流感染患者死亡的独立危险因素,应引起临床的重要关注。 相似文献
6.
7.
Qian Wang Xiaoxia Qu Weiwei Chen Huaizhou Wang Caiyun Huang Ting Li Ningli Wang Junfang Xian 《Journal of cerebral blood flow and metabolism》2021,41(4):901
Primary open-angle glaucoma (POAG) has been suggested to be a neurodegenerative disease associated with altered cerebral vascular hemodynamics and widespread disruption of neuronal activity within the visual, working memory, attention and executive networks. We hypothesized that disturbed neurovascular coupling in visual and higher order cognitive cortices exists in POAG patients and correlates with glaucoma stage and visual field defects. Through multimodal magnetic resonance imaging, we evaluated the cerebral blood flow (CBF)-functional connectivity strength (FCS) correlations of the whole gray matter and CBF/FCS ratio per voxel for all subjects. Compared with normal controls, POAG patients showed reduced global CBF-FCS coupling and altered CBF/FCS ratios, predominantly in regions in the visual cortex, salience network, default mode network, and dorsal attentional network. The CBF/FCS ratio was negatively correlated with glaucoma stage, and positively correlated with visual field defects in the lingual gyrus in POAG patients. Moreover, early brain changes were detected in early POAG. These findings indicate neurovascular coupling dysfunction might exist in the visual and higher order cognitive cortices in POAG patients and its clinical relevance. The results may contribute to the monitoring of POAG progression and provide insight into the pathophysiology of the neurodegenerative process in POAG. 相似文献
8.
目的观察高频喷射通气对老年无痛苦纤维支气管镜检患者血气结果的影响。方法 102例患者随机均分为两组,观察组喷射频率60次/min,对照组喷射频率25次/min。分别在麻醉前及喷射通气10 min时采股动脉血行血气分析,记录呛咳、呼吸抑制、体动反应和二氧化碳CO2蓄积例数。结果麻醉前及喷射通气10 min后动脉血氧分压(PaO2)、动脉血二氧化碳分压(PaCO2)和动脉血氧饱和度(SaO2)组间比较,差异均无统计学意义(P0.05)。每组喷射通气10 min后,PaO2、PaCO2和SaO2均明显升高,与麻醉前比较,差异有统计学意义(P 0.05)。观察组有4例、对照组有7例发生CO2蓄积,但PaCO265 mmHg,组间比较,差异无统计学意义(P0.05)。结论高频喷射通气可以为老年患者纤维支气管镜检查麻醉提供可靠的氧供,但不一定能阻止呼吸抑制等因素引起的CO2蓄积,应引起足够的临床重视。 相似文献
9.
Joonhyuk Lee Chloe L Stile Annie R Bice Zachary P Rosenthal Ping Yan Abraham Z Snyder Jin-Moo Lee Adam Q Bauer 《Journal of cerebral blood flow and metabolism》2021,41(4):841
Understanding cellular contributions to hemodynamic activity is essential for interpreting blood-based brain mapping signals. Optogenetic studies examining cell-specific influences on local hemodynamics have reported that excitatory activity results in cerebral perfusion and blood volume increase, while inhibitory activity contributes to both vasodilation and vasoconstriction. How specific subpopulations of interneurons regulate the brain’s blood supply is less examined. Parvalbumin interneurons are the largest subpopulation of GABAergic neurons in the brain, critical for brain development, plasticity, and long-distance excitatory neurotransmission. Despite their essential role in brain function, the contribution of parvalbumin neurons to neurovascular coupling has been relatively unexamined. Using optical intrinsic signal imaging and laser speckle contrast imaging, we photostimulated awake and anesthetized transgenic mice expressing channelrhodopsin under a parvalbumin promoter. Increased parvalbumin activity reduced local oxygenation, cerebral blood volume, and cerebral blood flow. These “negative” hemodynamic responses were consistent within and across mice and reproducible across a broad range of photostimulus parameters. However, the sign and magnitude of the hemodynamic response resulting from increased parvalbumin activity depended on the type and level of anesthesia used. Opposed hemodynamic responses following increased excitation or parvalbumin-based inhibition suggest unique contributions from different cell populations to neurovascular coupling. 相似文献
10.
Eri Minamino-Muta Takao Kato Takeshi Morimoto Tomohiko Taniguchi Chisato Izumi Kenji Nakatsuma Moriaki Inoko Shinichi Shirai Norio Kanamori Koichiro Murata Takeshi Kitai Yuichi Kawase Makoto Miyake Hirokazu Mitsuoka Yutaka Hirano Tomoki Sasa Kazuya Nagao Tsukasa Inada Takeshi Kimura 《JACC: Cardiovascular Interventions》2019,12(24):2499-2511
ObjectivesThe aim of this study was to investigate the prognostic impact of the decline in left ventricular ejection fraction (LVEF) at 1-year follow-up in patients with severe aortic stenosis (AS) managed conservatively.BackgroundNo previous study has explored the association between LVEF decline during follow-up and clinical outcomes in patients with severe AS.MethodsAmong 3,815 patients with severe AS enrolled in the multicenter CURRENT AS (Contemporary Outcomes After Surgery and Medical Treatment in Patients With Severe Aortic Stenosis) registry in Japan, 839 conservatively managed patients who underwent echocardiography at 1-year follow-up were analyzed. The primary outcome measure was a composite of AS-related deaths and hospitalization for heart failure.ResultsThere were 91 patients (10.8%) with >10% declines in LVEF and 748 patients (89.2%) without declines. Left ventricular dimensions and the prevalence of valve regurgitation and atrial fibrillation or flutter significantly increased in the group with declines in LVEF. The cumulative 3-year incidence of the primary outcome measure was significantly higher in the group with declines in LVEF than in the group with no decline (39.5% vs. 26.5%; p < 0.001). After adjusting for confounders, the excess risk of decline in LVEF over no decline for the primary outcome measure remained significant (hazard ratio: 1.98; 95% confidence interval: 1.29 to 3.06). When stratified by LVEF at index echocardiography (≥70%, 60% to 69%, and <60%), the risk of decline in LVEF on the primary outcome was consistently seen in all the subgroups, without any interaction (p = 0.77).ConclusionsPatients with severe AS with >10% declines in LVEF at 1 year after diagnosis had worse AS-related clinical outcomes than those without declines in LVEF under conservative management. (Contemporary Outcomes After Surgery and Medical Treatment in Patients With Severe Aortic Stenosis Registry; UMIN000012140) 相似文献