全文获取类型
收费全文 | 118611篇 |
免费 | 11473篇 |
国内免费 | 9118篇 |
专业分类
耳鼻咽喉 | 1021篇 |
儿科学 | 1126篇 |
妇产科学 | 1194篇 |
基础医学 | 14077篇 |
口腔科学 | 1968篇 |
临床医学 | 15997篇 |
内科学 | 17421篇 |
皮肤病学 | 1240篇 |
神经病学 | 6286篇 |
特种医学 | 4358篇 |
外国民族医学 | 81篇 |
外科学 | 12065篇 |
综合类 | 21245篇 |
现状与发展 | 42篇 |
一般理论 | 6篇 |
预防医学 | 7916篇 |
眼科学 | 3393篇 |
药学 | 12544篇 |
105篇 | |
中国医学 | 7279篇 |
肿瘤学 | 9838篇 |
出版年
2024年 | 395篇 |
2023年 | 1856篇 |
2022年 | 4510篇 |
2021年 | 6539篇 |
2020年 | 4894篇 |
2019年 | 4103篇 |
2018年 | 4289篇 |
2017年 | 3843篇 |
2016年 | 3665篇 |
2015年 | 5551篇 |
2014年 | 6860篇 |
2013年 | 6011篇 |
2012年 | 8709篇 |
2011年 | 9562篇 |
2010年 | 6039篇 |
2009年 | 4790篇 |
2008年 | 6164篇 |
2007年 | 6112篇 |
2006年 | 5903篇 |
2005年 | 5954篇 |
2004年 | 3885篇 |
2003年 | 3552篇 |
2002年 | 3050篇 |
2001年 | 2703篇 |
2000年 | 2851篇 |
1999年 | 3023篇 |
1998年 | 2018篇 |
1997年 | 2013篇 |
1996年 | 1562篇 |
1995年 | 1480篇 |
1994年 | 1280篇 |
1993年 | 794篇 |
1992年 | 991篇 |
1991年 | 798篇 |
1990年 | 667篇 |
1989年 | 626篇 |
1988年 | 520篇 |
1987年 | 448篇 |
1986年 | 398篇 |
1985年 | 299篇 |
1984年 | 136篇 |
1983年 | 116篇 |
1982年 | 68篇 |
1981年 | 72篇 |
1980年 | 47篇 |
1979年 | 54篇 |
1974年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
Zheng Xingming Ding Yanling Zhao Xiaowei Bai Yu Li Xiaofeng Zhao Kai 《Remote sensing letters.》2019,10(6):563-572
Vegetation water content (VWC) is the key input parameter for a soil moisture retrieval algorithm based on microwave remote sensing, and VWC uncertainty can limit the estimated accuracy of soil moisture. There has been little research on VWC algorithm development and validation in China, and the uncertainty of the VWC estimation method has not been well evaluated. Therefore, the aim of this study is to evaluate the uncertainty of the VWC estimation method used in the SMAP (Soil Moisture Active Passive) algorithm on three spatial scales (the point-scale, 30 m scale, and 1 km scale) for maize in northeast China. Results from three ground experimental datasets showed that the SMAP VWC estimation method was strongly biased with an average overestimation of 1.16 kg m?2,1.04 kg m?2, and 1.13 kg m?2 for the point-scale, 30 m scale, and 1 km scale respectively, and maximum bias occurred in the mid-stage of maize. Also, a new power relationship between NDVI (Normalized Difference Vegetation Index) and VWC was proposed for the 30 m scale based on Sentinel 2 NDVI and field VWC values from 2017 experiment, with respective R2 (coefficient of determination) and Root Mean Squared Error (RMSE) values of 0.80 and 0.67 kg m?2. The results confirmed that this power relationship was still suitable for VWC estimation at the 1 km scale, and it has smaller bias than the original SMAP VWC method. Future work will be carried out to evaluate the applicability of this VWC estimation method over a lager region. It is expected that it can improve the accuracy of soil moisture by providing high precision VWC input parameters. 相似文献
13.
European Archives of Oto-Rhino-Laryngology - Several polymorphisms in a disintegrin and metalloproteinase 33 (ADAM33) have been implicated in susceptibility to allergic rhinitis (AR), but the... 相似文献
14.
15.
Dan-Feng Xu Bing Wu Jin-Xin Wang Jian Yu Jian-Xin Xie 《World Journal of Clinical Cases》2021,9(5):1096-1102
BACKGROUNDGuillain-Barré syndrome (GBS) is a rare disorder that typically presents with ascending weakness, pain, paraesthesias, and numbness, which mimic the findings in lumbar spinal stenosis. Here, we report a case of severe lumbar spinal stenosis combined with GBS.CASE SUMMARYA 70-year-old man with a history of lumbar spinal stenosis presented to our emergency department with severe lower back pain and lower extremity numbness. Magnetic resonance imaging confirmed the diagnosis of severe lumbar spinal stenosis. However, his symptoms did not improve postoperatively and he developed dysphagia and upper extremity numbness. An electromyogram was performed. Based on his symptoms, physical examination, and electromyogram, he was diagnosed with GBS. After 5 d of intravenous immunoglobulin (0.4 g/kg/d for 5 d) therapy, he gained 4/5 of strength in his upper and lower extremities and denied paraesthesias. He had regained 5/5 of strength in his extremities when he was discharged and had no symptoms during follow-up.CONCLUSIONGBS should be considered in the differential diagnosis of spinal disorder, even though magnetic resonance imaging shows severe lumbar spinal stenosis. This case highlights the importance of a careful diagnosis when a patient has a history of a disease and comes to the hospital with the same or similar symptoms. 相似文献
16.
目的 检测分析被诊断为X连锁视网膜色素变性(XLRP)的三个中国家系内的基因突变。设计 基因研究。研究对象 三个中国XLRP家系共27位受试者(其中18人为男性)。方法 由同一医生收集家系成员的详细临床资料并进行眼部检查,采集三个家系的先证者及有条件采血者的外周静脉血,提取基因组DNA。应用PCR技术扩增RPGR和RP2基因的全部外显子和内含子交界区序列,包括RPGR基因15号外显子开放阅读框,产物直接测序进行突变分析。主要指标 临床特征及基因测序结果。结果 基因筛查证实了两个RPGR基因的新型无义突变(c.1541C>G;p.S514X 和 c.2833G>T;p.E945X) 及一个错义突变(c.607G>C;p.A203P)。基因型-表型的相关性分析表明家系3患者在接近ORF15下游位置存在突变,这种突变导致视锥细胞功能的早期丧失。ORF15无义突变的女性携带者临床表型重,呈现出部分显性遗传的特点。结论 本研究证实了三种RPGR基因的新型突变,这一结果扩展了RPGR的突变谱及表型谱。 相似文献
17.
18.
Tianying Yang Jiawei Li Yichen Jia Chunchen Yang Ruirui Sang Tongyu Zhu Ming Xu Ruiming Rong Cheng Yang 《Translational andrology and urology》2021,10(1):204
BackgroundIn the field of transplantation, inducing immune tolerance in recipients is of great importance. Blocking co-stimulatory molecule using anti-CD28 antibody could induce tolerance in a rat kidney transplantation model. Myeloid-derived suppressor cells (MDSCs) reveals strong immune suppressive abilities in kidney transplantation. Here we analyzed key genes of MDSCs leading to transplant tolerance in this model.MethodsMicroarray data of rat gene expression profiles under accession number in the Gene Expression Omnibus (GEO) database were analyzed. Running the LIMMA package in R language, the differentially expressed genes (DEGs) were found. Enrichment analysis of the DEGs was conducted in the Database for Annotation, Visualization and Integrated Discovery (DAVID) database to explore gene ontology (GO) annotation and their Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Their protein-protein interactions (PPIs) were provided by STRING database and was visualized in Cytoscape. Hub genes were carried out by CytoHubba.ResultsThree hundred and thirty-eight DEGs were exported, including 27 upregulated and 311 downregulated genes. The functions and KEGG pathways of the DEGs were assessed and the PPI network was constructed based on the string interactions of the DEGs. The network was visualized in Cytoscape; the entire PPI network consisted of 192 nodes and 469 edges. Zap70, Cdc42, Stat1, Stat4, Ccl5 and Cxcr3 were among the hub genes.ConclusionsThese key genes, corresponding proteins and their functions may provide valuable background for both basic and clinical research and could be the direction of future studies in immune tolerance, especially those examining immunocyte-induced tolerance. GSE28545相似文献
19.
目的本研究立足于项目组前期研究的成果上,积极探索吉林辽宁两省目标设置水平的差异,并进一步探究受目标设置影响下的工作落实结果情况,探讨产生差异的原因。
方法以系统穷尽的方式收集吉林辽宁两省2000至2017年有关目标与工作落实情况的指标,利用Spearman相关和线性回归分析吉林辽宁两省目标设置对于突发应急工作落实情况的影响。
结果吉林辽宁两省突发应急领域的目标设置水平与工作落实情况总体均呈现上升趋势,截至2017年,吉林目标设置水平与工作落实情况分别为46%与60%,辽宁为60%与53.3%,且目标设置水平与工作落实呈正相关。
结论有公众需要为依据且定量可考的目标设置对于工作落实、推进、完善具有积极的正反馈作用,建立科学量化的突发应急目标设置评价体系是适宜可行的。 相似文献
20.