全文获取类型
收费全文 | 1141篇 |
免费 | 123篇 |
国内免费 | 34篇 |
专业分类
耳鼻咽喉 | 5篇 |
儿科学 | 2篇 |
妇产科学 | 10篇 |
基础医学 | 107篇 |
口腔科学 | 337篇 |
临床医学 | 131篇 |
内科学 | 45篇 |
皮肤病学 | 9篇 |
神经病学 | 60篇 |
特种医学 | 78篇 |
外科学 | 171篇 |
综合类 | 136篇 |
预防医学 | 42篇 |
眼科学 | 20篇 |
药学 | 67篇 |
1篇 | |
中国医学 | 40篇 |
肿瘤学 | 37篇 |
出版年
2024年 | 5篇 |
2023年 | 29篇 |
2022年 | 58篇 |
2021年 | 75篇 |
2020年 | 68篇 |
2019年 | 75篇 |
2018年 | 63篇 |
2017年 | 73篇 |
2016年 | 61篇 |
2015年 | 51篇 |
2014年 | 60篇 |
2013年 | 74篇 |
2012年 | 64篇 |
2011年 | 58篇 |
2010年 | 65篇 |
2009年 | 61篇 |
2008年 | 28篇 |
2007年 | 52篇 |
2006年 | 39篇 |
2005年 | 40篇 |
2004年 | 32篇 |
2003年 | 23篇 |
2002年 | 32篇 |
2001年 | 18篇 |
2000年 | 20篇 |
1999年 | 20篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有1298条查询结果,搜索用时 171 毫秒
31.
T波终点识别是ECG信号QT间期检测中的关键技术。由于T波末端呈对数衰减及易受杂音叠加的影响,使得高精度的T波终点识别显得困难。定义T波末端衰减率至某一阈值δ的时刻为T波终点,并将此法应用于QT间期的自动检测。以T波顶点为标识,将其后的0.2 s数据叠加成一个平均信号φ(t),以函数φ^(t)=Aeαt拟合φ的末端,并利用最小二乘法确定其参数。将此φ函数作为模板去匹配心电图的T波可获得相应的A和α值,并通过微分运算得出T波终点的位置。利用此方法进行QT间期检测,显示出良好的准确性和鲁棒性。 相似文献
32.
Starting from established CYP3A4 Template (DMPK. 2019, and 2020), CYP3A5 and CYP3A7 Templates have been constructed to be reliable tools for verification of their distinct catalytic properties. A distinct occupancy was observed on CYP3A4-selective ligands, but not on the non-selective ligands, in simulation experiments. These ligands often invade into Bay-1 region during the migration from Entrance to Site of oxidation in simulation experiments. These results offered an idea of the distinct localization of Bay-1 residue on CYP3A5 Template, in which the Bay-1 residue stayed closely to Template border. The idea also accounted for the higher oxidation rates of CYP3A5, than of CYP3A4, of noscapine and schisantherin E through their enhanced sitting-stabilization. Typical CYP3A7 substrates such as zonisamide and retinoic acids took their placements without occupying a left side region of Template for their metabolisms. In turn, the occupancies of the left-side region were inevitably observed among poor ligands of CYP3A7. Altered extent of IJK-Interaction or localization of a specific residue at the left-side would thus explain distinct catalytic properties of CYP3A7 on Template. These data suggest the alteration of each one of Template region, from CYP3A4 Template, led to the distinct catalytic properties of CYP3A5 and CYP3A7 forms. 相似文献
33.
近年来计算机断层扫描技术、种植三维修复设计软件、数字化种植外科手术导板加工技术在口腔种植学领域的应用得到了很快发展,计算机辅助设计种植手术导板在临床中已有较多临床病例报道。本文就种植手术导板的数字化加工的技术发展、数字化手术导板的分类、临床实际操作流程、适应证选择进行分析总结,为临床实际应用提供参考依据。 相似文献
34.
《Radiography》2017,23(4):310-313
IntroductionImplementation of the Clarity® Autoscan (Elekta) Transperineal Ultrasound (TPUS) system in Bristol is the first of its kind in the UK and we have already shown its utility in interfractional Image Guided Radiotherapy (IGRT).14 This study establishes the extent of intrafraction prostate motion as measured by Clarity and explores the potential benefits of TPUS for intrafraction monitoring.MethodsMonitoring data was analysed for 526 fractions from 20 localised prostate cancer patients. Intrafraction prostate displacements exceeding thresholds of 3 mm, 7 mm and 10 mm along patient axes were assessed for frequency and duration of motion.ResultsProstate motion exceeds the above displacement thresholds during 52%, 8%, and 2% of fractions analysed. Displacement at the 3 mm threshold occurred for 100% of patients, 60% at 7 mm and 35% at 10 mm. The mean frequency and duration of displacements is low for the overall population. In contrast specific patients exhibit much higher displacement values. Posterior motion is most common, averaging at 24% of the treatment time at 3 mm, 3% at 7 mm and 1% at 10 mm, ranging up to 92%, 35% and 10% for individual patients.ConclusionsIntrafraction monitoring with Clarity has the potential to improve accuracy through application of in-treatment motion correction. This is most beneficial for specific patients who exhibit a higher frequency and/or duration of prostate motion. Consideration must be given to the added time implications and radiographer workload in clinical practice to correct for prostate motion. Clarity could help facilitate future protocols using tighter treatment margins, although further research is required. 相似文献
35.
36.
Susanna Annibali MD DDS Gerardo La Monaca DDS PhD Marco Tantardini DDS & Maria Paola Cristalli DDS PhD 《Journal of prosthodontics》2009,18(2):177-183
In prosthetically guided implantology, where ideal placement of implants is determined by the definitive restoration, the use of a radiographic/surgical template plays an essential role. This article describes how to fabricate a radiographic/surgical template to be used for radiographic diagnosis of the selected implant sites and as a guide during surgery for the insertion of the implant with correct angulation. 相似文献
37.
ObjectivesIntraoperative visualization of gliomas with 5-aminolevulinic acid (5-ALA) induced fluorescence constitutes a powerful technique. While visible fluorescence is typically observed in high-grade gliomas, fluorescence is considerably less common in lower-grade gliomas (LGGs) WHO grade II&III. Whereas the exact mechanisms determining fluorescence in LGGs are not fully understood, metabolization of non-fluorescent 5-ALA to fluorescent Protoporphyrin IX by specific heme biosynthesis enzymes/transporters has been identified as relevant mechanism influencing fluorescence behavior. Furthermore, recent in-vitro studies have suggested preoperative treatment with corticosteroids and anti-epileptic drugs (AED) as potential factors influencing 5-ALA induced fluorescence.MethodsThe goal of this study was thus to investigate the effect of preoperative corticosteroid/AED treatment on heme biosynthesis mRNA expression in a clinically relevant patient population. For this purpose, we analyzed the mRNA expression levels of specific heme biosynthesis factors including ALAD, HMBS, UROS, UROD, CPOX, PPOX, FECH, ABCB6, ACG2, SLC15A1 and SLC15A2, ABCB1, ABCB10 in a cohort of LGGs from “The Cancer Genome Atlas”.ResultsAltogether, 403 patients with available data on preoperative corticosteroid/AED treatment and heme biosynthesis mRNA expression were identified. Regarding corticosteroid treatment, no significant differences in expression of any of the 11 investigated heme biosynthesis factors were found. In contrast, a marginal yet statistically significant increase in SLC15A1 levels and decrease in ABCB6 levels were observed in patients with preoperative AED treatment.ConclusionWhile no significant differences in heme biosynthesis mRNA expression were observed according to preoperative corticosteroid treatment, changes in SLC15A1 as well as ABCB6 expression were detected in patients treated with AED. However, since these alterations were minor and have opposing effects on 5-ALA metabolization, our findings do not support a distinct effect of AED and corticosteroid treatment on heme biosynthesis regulation in LGGs. 相似文献
38.
Gerhard Andersson Hugo Hesser Andrea Veilord Linn Svedling Fredrik Andersson Owe Sleman Lena Mauritzson Ali Sarkohi Elisabet Claesson Vendela Zetterqvist Mailen Lamminen Thomas Eriksson Per Carlbring 《Journal of affective disorders》2013
Background
Guided internet-delivered cognitive behaviour therapy (ICBT) has been found to be effective in the treatment of mild to moderate depression, but there have been no direct comparisons with the more established group-based CBT with a long-term follow-up.Method
Participants with mild to moderate depression were recruited from the general population and randomized to either guided ICBT (n=33) or to live group treatment (n=36). Measures were completed before and after the intervention to assess depression, anxiety, and quality of life. Follow-ups were conducted at one-year and three-year after the treatment had ended.Results
Data were analysed on an intention-to-treat basis using linear mixed-effects regression analysis. Results on the self-rated version of the Montgomery–Åsberg Depression Scale showed significant improvements in both groups across time indicating non-inferiority of guided ICBT, and there was even a tendency for the guided ICBT group to be superior to group-based CBT at three year follow-up. Within-group effect sizes for the ICBT condition at post-treatment showed a Cohen′s d=1.46, with a similar large effect at 3-year follow-up, d=1.78. For the group CBT the corresponding within-group effects were d=0.99 and d=1.34, respectively.Limitations
The study was small with two active treatments and there was no placebo or credible control condition.Conclusions
Guided ICBT is at least as effective as group-based CBT and long-term effects can be sustained up to 3 years after treatment. 相似文献39.
Michela Azzarito Sreenath P. Kyathanahally Yaël Balbastre Maryam Seif Claudia Blaiotta Martina F. Callaghan John Ashburner Patrick Freund 《Human brain mapping》2021,42(1):220-232
To validate a simultaneous analysis tool for the brain and cervical cord embedded in the statistical parametric mapping (SPM) framework, we compared trauma‐induced macro‐ and microstructural changes in spinal cord injury (SCI) patients to controls. The findings were compared with results obtained from existing processing tools that assess the brain and spinal cord separately. A probabilistic brain‐spinal cord template (BSC) was generated using a generative semi‐supervised modelling approach. The template was incorporated into the pre‐processing pipeline of voxel‐based morphometry and voxel‐based quantification analyses in SPM. This approach was validated on T1‐weighted scans and multiparameter maps, by assessing trauma‐induced changes in SCI patients relative to controls and comparing the findings with the outcome from existing analytical tools. Consistency of the MRI measures was assessed using intraclass correlation coefficients (ICC). The SPM approach using the BSC template revealed trauma‐induced changes across the sensorimotor system in the cord and brain in SCI patients. These changes were confirmed with established approaches covering brain or cord, separately. The ICC in the brain was high within regions of interest, such as the sensorimotor cortices, corticospinal tracts and thalamus. The simultaneous voxel‐wise analysis of brain and cervical spinal cord was performed in a unique SPM‐based framework incorporating pre‐processing and statistical analysis in the same environment. Validation based on a SCI cohort demonstrated that the new processing approach based on the brain and cord is comparable to available processing tools, while offering the advantage of performing the analysis simultaneously across the neuraxis. 相似文献
40.
目的:探讨侧壁开窗法上颌窦底提升术这种特殊的引导性骨再生(guided bone regeneration, GBR)过程的转录组特点。方法:3只Beagle犬,随机选择一侧经侧壁开窗行上颌窦底提升术,同时植入Bio-Oss骨粉,术后2周,对另一侧用相同的方法行上颌窦底提升术。第2次术后2周,收集植入的Bio-Oss骨粉组织块,提取总RNA,全基因组表达谱芯片检测分析上颌窦底提升后2周和4周时的差异表达基因。利用基因本体论(gene ontology, GO)对差异表达的基因进行功能分类,以及京都基因与基因组百科全书(Kyoto Encyclopedia of Genes and Genomes, KEGG)进行信号通路分析。结果:在2周时表达升高的基因与刺激反应、免疫-炎症反应和细胞增殖有关,同时,与神经元分化、破骨细胞分化和早期血管化过程相关的基因也高表达。在4周时,与细胞代谢和发育相关的基因表达升高,重要的是,与血管生成和骨骼发育相关的基因都高表达,与骨骼发育相关的基因包括骨生成相关的生长和分化因子[转化生成因子β1(transforming growth factor beta 1, TGFB1)和骨形态发生蛋白4(bone morphogenetic protein 4, BMP4)]、软骨和骨胞外基质[软骨黏附素(chondroadherin, CHAD)、Ⅰ型胶原α1链(collagen type I, alpha 1 chain, COL1A1)、Ⅰ型胶原α2链(collagen type I, alpha 2 chain, COL1A2)、Ⅴ型胶原α2链(collagen type Ⅴ, alpha 2 chain, COL5A2)、核心蛋白聚糖(decorin, DCN)、骨连接蛋白(osteonectin, SPARC)和骨钙素(osteocalcin, BGLAP)]等相关的基因。信号通路分析显示4周时表达升高的基因与转化生长因子β/骨形态发生蛋白(transforming growth factor beta/bone morphogenetic protein, TGF-β/BMP)信号通路有关。无翅型MMTV整合位点家族(wingless-type MMTV integration site family, WNT)信号通路中的关键基因WNT5A和卷曲蛋白受体9(frizzled receptor 9, FZD9)在2周时表达升高,而连环蛋白β1(catenin beta 1, CTNNB1)在4周时表达升高。结论:侧壁开窗法上颌窦底提升术2周后转录表达谱变化以免疫-炎症反应和破骨反应下调、骨生成相关基因表达升高为特点,骨再生的过程还与神经生成和血管生成过程相关。在骨再生的过程中,TGF-β/BMP和WNT信号通路起重要作用,WNT信号通路的作用复杂。 相似文献