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   158115篇
  免费   15779篇
  国内免费   8739篇
耳鼻咽喉   1287篇
儿科学   2105篇
妇产科学   1907篇
基础医学   23255篇
口腔科学   3148篇
临床医学   18851篇
内科学   22340篇
皮肤病学   1732篇
神经病学   7935篇
特种医学   5296篇
外国民族医学   68篇
外科学   15575篇
综合类   24943篇
现状与发展   30篇
一般理论   13篇
预防医学   11030篇
眼科学   3835篇
药学   17775篇
  167篇
中国医学   8547篇
肿瘤学   12794篇
  2024年   1895篇
  2023年   3096篇
  2022年   6321篇
  2021年   7962篇
  2020年   6023篇
  2019年   5271篇
  2018年   5453篇
  2017年   4982篇
  2016年   4761篇
  2015年   6883篇
  2014年   8492篇
  2013年   8291篇
  2012年   11501篇
  2011年   12177篇
  2010年   8586篇
  2009年   6911篇
  2008年   8377篇
  2007年   8381篇
  2006年   7635篇
  2005年   6904篇
  2004年   5433篇
  2003年   5227篇
  2002年   4456篇
  2001年   3651篇
  2000年   3153篇
  1999年   2811篇
  1998年   1776篇
  1997年   1906篇
  1996年   1349篇
  1995年   1258篇
  1994年   1161篇
  1993年   839篇
  1992年   1052篇
  1991年   978篇
  1990年   876篇
  1989年   802篇
  1988年   708篇
  1987年   611篇
  1986年   567篇
  1985年   449篇
  1984年   393篇
  1983年   318篇
  1982年   277篇
  1981年   242篇
  1980年   211篇
  1979年   211篇
  1978年   200篇
  1977年   224篇
  1976年   196篇
  1974年   162篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Neuroscience and Behavioral Physiology - Objectives. To assess the severity of pain syndrome, emotional status, and quantitative levels of humoral serotonin in patients with cervical dystonia (CD)...  相似文献   
42.
Neuroscience and Behavioral Physiology - One version of the optogenetic prosthetization of the degenerative retina is an approach based on creation of an ON/OFF receptive field for ganglion neurons...  相似文献   
43.
Neuroscience and Behavioral Physiology - Confocal microscopy was used to analyze double immunolabeling and provided evidence of the locations of a large number of tyrosine...  相似文献   
44.
Neuroscience and Behavioral Physiology - Objective: To study the characteristics of the expression of inducible NO synthase (iNOS) in hippocampal fields CA1 and CA3 in adult male humans and adult...  相似文献   
45.
Comprehensive data on hepatitis C virus (HCV) genotypes distribution is critical for treatment regimen selection, vaccine design, and drug development. This study aimed to understand the dynamic distribution of HCV genotypes in Mainland China. Three hundred sixty-two studies published from January 1993 to December 2017 involving 64 891 samples (5133 injecting drug users, 2748 volunteer blood donors, 1509 former paid plasma donors, 160 sexually encounters, and 1992 human immunodeficiency virus (HIV)/HCV coinfection patients) were eligible for the quantitative synthesis estimation. Pooled proportion of HCV genotypes (and 95% confidence intervals [CIs]) was estimated through the Freeman-Tukey double arcsine transformation by period, region, and risk group. A sharp decline of the subtype 1b was observed in all regions except in northwestern and central regions. The genotypes 3 and 6 showed an obvious increase in southern and southwestern regions and have already spread nationwide. After 2010, subtype 1b was the most dominant variant in all regions and risk groups, accounting for 54.0% (95% CI, 51.9-56.1) of all national infections. Subtype 2a was the second most prevalent strain in all regions except in the south and southwest, with 15.4% (95% CI, 13.1-17.8) national infections. The subtype 6a in southern region and 3b and 3a in southwestern region had a higher proportion of infections than that in other regions. In addition, the genotypes 3 and 6 are already prevalent in almost all risk groups. The distribution of HCV genotypes were sharply shifting in China in the past three decades. The HCV subtype 1b posed a sharp decline, whereas genotypes 3 and 6 played an increasing role in the regional and populational HCV pandemic.  相似文献   
46.
47.
Some species of mycobacteria have been modified to transform sterols to valuable steroid synthons. The unique cell wall of mycobacteria has been recognized as an important organelle to absorb sterols. Some cell wall inhibitors (e.g., vancomycin and glycine) have been validated to enhance sterol conversion by interfering with transpeptidation in peptidoglycan biosynthesis. Therefore, two transpeptidase genes, pbpA and pbpB, were selected to rationally modify the cell wall to simulate the enhancement effect of vancomycin and glycine on sterol conversion in a 22‐hydroxy‐23,24‐bisnorchol‐4‐ene‐3‐one (4‐HBC) producing strain (WIII). Unexpectedly, the pbpA or pbpB gene augmentation was conducive to the utilization of sterols. The pbpB augmentation strain WIII‐pbpB was further investigated for its better performance. Compared to WIII, the morphology of WIII‐pbpB was markedly changed from oval to spindle, indicating alterations of the cell wall. Biochemical analysis indicated that the altered cell wall properties of WIII‐pbpB might contribute to the positive effect on sterol utilization. The productivity of 4‐HBC was enhanced by 28% in the WIII‐pbpB strain compared to that of WIII. These results demonstrated that the modification of peptidoglycan synthesis can improve the conversion of sterols to steroid synthons in mycobacteria.  相似文献   
48.
等离子医学是研究等离子技术在医学领域应用的一门新兴科学。简述低温常压等离子技术,着重介绍其在肿瘤学中的应用。在肿瘤学领域中,等离子技术通过直接处理肿瘤细胞,产生大量活性物质引起肿瘤细胞的凋亡、坏死和自噬,从而发挥对肿瘤组织的直接致死性作用;等离子技术也可通过活化液体,使活化液体具备细胞毒性作用,从而发挥对肿瘤组织的间接致死性作用;同时等离子技术也具有诸多对肿瘤组织的非致死性作用;此外等离子技术也可参与构建化疗药物的缓释系统,协助药物跨生物膜转运,与传统化疗药物产生协同抗肿瘤的作用等,在肿瘤药物学领域发挥重要作用。  相似文献   
49.
Myxomycetes are eukaryotic microorganisms containing characteristics akin to both fungi and amoebae. They can complete their whole life cycles while being cultured on agar media, and under‐laboratory conditions, which favors taxonomic, phylogenetic, and cytological researches. Here, we describe the life cycles of two such species: Didymium squamulosum collected from the field and Physarum rigidum cultured from moist chamber both belonging to the Order Physarales. Three per cent oat‐agar media (OAM) was used to culture the plasmodia until they aggregated and were almost starved. Natural light was then applied to the plasmodia to induce fructification. Their life cycles share the same common stages, namely: spore, myxamoebae, swarm cell, plasmodia, and sporulation. In this study, we describe the morphogenesis from spore to spore of two species by differential interference contrast (DIC) and stereoscopic microscopies, as well as discuss the differences between the development of both species and interspecies. We found that the spore germination method of both species was the same. However, there were differences noted in time taken and fruiting body formation. Unlike P. rigidum, the species D. squamulosum did not require natural light stimulation. Moreover, the maturation process of both species had similar color transitions but exhibited distinct morphology in each developmental stage except during the swarm cell stage.  相似文献   
50.
目的研究二巯基丁二酸修饰的Fe3O4纳米颗粒(dimercaptosuccinic acid-magnetite nanoparticles,DMSA-Fe3O4)对人脐静脉内皮细胞(human umbilical vein endothelial cells,HUVECs)功能的影响。方法利用动态光散射法表征DMSA-Fe3O4的粒径及表面电荷;采用普鲁士蓝染色、邻二氮菲铁定量和透射电镜观察方法研究HUVECs对DMSA-Fe3O4的摄取规律;利用细胞计数试剂盒(Cell Counting Kit-8,CCK-8)检测DMSA-Fe3O4对内皮细胞活性的影响;通过酶联免疫吸附试剂盒测定DMSA-Fe3O4对内皮细胞血管内皮生长因子(vascular endothelial growth factor,VEGF)分泌量的影响。结果HUVECs能够大量吞噬DMSA-Fe3O4,其吞噬量具有孵育时间和剂量依赖性;短时间内所测剂量范围DMSA-Fe3O4对细胞活性无显著影响,但长时间高剂量条件使细胞活性明显降低。此外,在高剂量DMSA-Fe3O4暴露下(200μg/mL),内皮细胞分泌VEGF的量约为对照组的3倍。结论DMSA-Fe3O4易于被HUVECs吞噬;高浓度DMSA-Fe3O4与HUVECs长时间培养使细胞活性降低,并刺激内皮细胞分泌VEGF。  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