全文获取类型
收费全文 | 94003篇 |
免费 | 3704篇 |
国内免费 | 2834篇 |
出版年
2023年 | 741篇 |
2022年 | 864篇 |
2021年 | 2062篇 |
2020年 | 1468篇 |
2019年 | 1899篇 |
2018年 | 1551篇 |
2017年 | 1270篇 |
2016年 | 1892篇 |
2015年 | 3990篇 |
2014年 | 7724篇 |
2013年 | 7899篇 |
2012年 | 5764篇 |
2011年 | 6558篇 |
2010年 | 4857篇 |
2009年 | 4568篇 |
2008年 | 4729篇 |
2007年 | 5095篇 |
2006年 | 3664篇 |
2005年 | 3250篇 |
2004年 | 2403篇 |
2003年 | 2111篇 |
2002年 | 1921篇 |
2001年 | 1394篇 |
2000年 | 1327篇 |
1999年 | 1278篇 |
1998年 | 1175篇 |
1997年 | 987篇 |
1996年 | 1021篇 |
1995年 | 1225篇 |
1994年 | 1124篇 |
1993年 | 1025篇 |
1992年 | 1005篇 |
1991年 | 886篇 |
1990年 | 831篇 |
1989年 | 750篇 |
1988年 | 799篇 |
1987年 | 641篇 |
1986年 | 574篇 |
1985年 | 846篇 |
1984年 | 1203篇 |
1983年 | 777篇 |
1982年 | 1000篇 |
1981年 | 845篇 |
1980年 | 645篇 |
1979年 | 634篇 |
1978年 | 394篇 |
1977年 | 388篇 |
1976年 | 362篇 |
1974年 | 255篇 |
1973年 | 259篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
高血压是常见的慢性疾病,也是心脑血管病最主要的风险因素。原发性高血压是由多基因和环境因素共同作用引起的复杂疾病,但具体的发病机制仍不清楚。随着研究的深入,DNA甲基化等表观遗传学因素在原发性高血压病理过程中起到的作用逐渐受到重视。本文总结了部分原发性高血压关联基因中DNA甲基化在其患病中的研究进展,阐述可受环境因素影响的DNA甲基标记与原发性高血压的关系,进一步了解高血压的发病机制。 相似文献
4.
5.
6.
Marco Dogs Bernd Wemheuer Laura Wolter Nils Bergen Rolf Daniel Meinhard Simon Thorsten Brinkhoff 《Systematic and applied microbiology》2017,40(6):370-382
Macroalgae harbour specific microbial communities on their surface that have functions related to host health and defence. In this study, the bacterial biofilm of the marine brown alga Fucus spiralis was investigated using 16S rRNA gene amplicon-based analysis and isolation of bacteria. Rhodobacteraceae (Alphaproteobacteria) were the predominant family constituting 23% of the epibacterial community. At the genus level, Sulfitobacter, Loktanella, Octadecabacter and a previously undescribed cluster were most abundant, and together they comprised 89% of the Rhodobacteraceae. Supported by a specific PCR approach, 23 different Rhodobacteraceae-affiliated strains were isolated from the surface of F. spiralis, which belonged to 12 established and three new genera. For seven strains, closely related sequences were detected in the 16S rRNA gene dataset. Growth experiments with substrates known to be produced by Fucus spp. showed that all of them were consumed by at least three strains, and vitamin B12 was produced by 70% of the isolates. Since growth of F. spiralis depends on B12 supplementation, bacteria may provide the alga with this vitamin. Most strains produced siderophores, which can enhance algal growth under iron-deficient conditions. Inhibiting properties against other bacteria were only observed when F. spiralis material was present in the medium. Thus, the physiological properties of the isolates indicated adaption to an epiphytic lifestyle. 相似文献
7.
Maria Weinert Tharakeswari Selvakumar Travis S. Tierney Kambiz N. Alavian 《Journal of visualized experiments : JoVE》2015,(96)
Degeneration of mesencephalic dopaminergic (mesDA) neurons is the pathological hallmark of Parkinson’s diseae. Study of the biological processes involved in physiological functions and vulnerability and death of these neurons is imparative to understanding the underlying causes and unraveling the cure for this common neurodegenerative disorder. Primary cultures of mesDA neurons provide a tool for investigation of the molecular, biochemical and electrophysiological properties, in order to understand the development, long-term survival and degeneration of these neurons during the course of disease. Here we present a detailed method for the isolation, culturing and maintenance of midbrain dopaminergic neurons from E12.5 mouse (or E14.5 rat) embryos. Optimized cell culture conditions in this protocol result in presence of axonal and dendritic projections, synaptic connections and other neuronal morphological properties, which make the cultures suitable for study of the physiological, cell biological and molecular characteristics of this neuronal population. 相似文献
8.
We sought to develop nuclear DNA (nDNA) probes which could be used to complement mtDNA and DNA fingerprinting markers in distinguishing striped bass, Morone saxatilis (Walbaum), from discrete spawning systems. Restriction endonuclease-generated single copy, 10–20-kb striped bass nuclear nDNA fragments were cloned into the bacteriophage vector Lambda Dash II and tested in Southern blot analyses for their abilities to reveal population-specific polymorphisms. Three of the I7 nDNA sequences tested exhibited polymorphisms which potentially could be used to delineate striped bass populations. One probe, DSB 22, revealed significant genotypic frequency differences between Gulf of Mexico and Atlantic striped bass and among striped bass representative of some Atlantic systems. These preliminary results suggest that single copy nDNA sequences may provide sufficient polymorphisms to aid in stock identification of species which proved genetically monomorphic using other approaches. 相似文献
9.
Abstract. Anopheles stephensi mosquitoes which had fed upon mice infected with Plasmodium yoelii nigeriensis malaria parasites produced significantly fewer eggs than mosquitoes fed on an uninfected mouse. Fecundity reduction was more pronounced when the bloodmeal contained malaria gametocytes and the mosquitoes developed oocysts. Egg production and haematin excretion were correlated for uninfected bloodfed mosquitoes; the presence of P.y. nigeriensis in the blood affected this relationship. Reduced fecundity was associated with a significant reduction of bloodmeal size (measured by haematin excretion) in mosquitoes which ingested gametocytaemic blood. The bloodmeal size in mosquitoes fed on parasitaemic blood without gametocytes was not significantly reduced. The use of haematin assays for determination of bloodmeal size in mosquitoes is discussed. 相似文献
10.