全文获取类型
收费全文 | 61941篇 |
免费 | 17787篇 |
国内免费 | 2677篇 |
专业分类
82405篇 |
出版年
2024年 | 92篇 |
2023年 | 523篇 |
2022年 | 1186篇 |
2021年 | 2212篇 |
2020年 | 3323篇 |
2019年 | 5124篇 |
2018年 | 5179篇 |
2017年 | 5122篇 |
2016年 | 5600篇 |
2015年 | 6182篇 |
2014年 | 6184篇 |
2013年 | 6904篇 |
2012年 | 5057篇 |
2011年 | 4566篇 |
2010年 | 4799篇 |
2009年 | 3343篇 |
2008年 | 2485篇 |
2007年 | 2007篇 |
2006年 | 1779篇 |
2005年 | 1562篇 |
2004年 | 1334篇 |
2003年 | 1243篇 |
2002年 | 1097篇 |
2001年 | 812篇 |
2000年 | 713篇 |
1999年 | 627篇 |
1998年 | 340篇 |
1997年 | 277篇 |
1996年 | 311篇 |
1995年 | 254篇 |
1994年 | 209篇 |
1993年 | 169篇 |
1992年 | 236篇 |
1991年 | 215篇 |
1990年 | 162篇 |
1989年 | 154篇 |
1988年 | 126篇 |
1987年 | 132篇 |
1986年 | 97篇 |
1985年 | 113篇 |
1984年 | 67篇 |
1983年 | 72篇 |
1982年 | 36篇 |
1981年 | 34篇 |
1980年 | 29篇 |
1979年 | 43篇 |
1978年 | 33篇 |
1977年 | 22篇 |
1975年 | 29篇 |
1974年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
ShuChun Kuo ChungChing Chio ChaoHung Yeh JuiTi Ma WenPin Liu MaoTsun Lin KaoChang Lin ChingPing Chang 《Aging cell》2021,20(5)
Amyloid‐beta (Aβ) oligomer is known to contribute to the pathophysiology of age‐related macular degeneration. Herein, we aimed to elucidate the in vivo and in vitro effects of Aβ1‐42 application on retinal morphology in rats. Our in vivo studies revealed that intracerebroventricular administration of Aβ1‐42 oligomer caused dysmorphological changes in both retinal ganglion cells and retinal pigment epithelium. In addition, in vitro studies revealed that ARPE‐19 cells following Aβ1‐42 oligomer application had decreased viability along with apoptosis and decreased expression of the tight junction proteins, increased expression of both phosphor‐AKT and phosphor‐GSK3β and decreased expression of both SIRT1 and β‐catenin. Application of conditioned medium (CM) obtained from mesenchymal stem cells (MSC) protected against Aβ1‐42 oligomer‐induced retinal pathology in both rats and ARPE‐19 cells. In order to explore the potential role of peptides secreted from the MSCs, we applied mass spectrometry to compare the peptidomics profiles of the MSC‐CM. Gene ontology enrichment analysis and String analysis were performed to explore the differentially expressed peptides by predicting the functions of their precursor proteins. Bioinformatics analysis showed that 3‐8 out of 155–163 proteins in the MSC‐CM maybe associated with SIRT1/pAKT/pGSK3β/β‐catenin, tight junction proteins, and apoptosis pathway. In particular, the secretomes information on the MSC‐CM may be helpful for the prevention and treatment of retinal pathology in age‐related macular degeneration. 相似文献
992.
Bo Hu Xiaolu Ma Peiyao Fu Qiman Sun Weiguo Tang Haixiang Sun Zhangfu Yang Mincheng Yu Jian Zhou Jia Fan Yang Xu 《基因组蛋白质组与生物信息学报(英文版)》2021,19(6):913
The aim of this study was to identify novel prognostic mRNA and microRNA (miRNA) biomarkers for hepatocellular carcinoma (HCC) using methods in systems biology. Differentially expressed mRNAs, miRNAs, and long non-coding RNAs (lncRNAs) were compared between HCC tumor tissues and normal liver tissues in The Cancer Genome Atlas (TCGA) database. Subsequently, a prognosis-associated mRNA co-expression network, an mRNA–miRNA regulatory network, and an mRNA–miRNA–lncRNA regulatory network were constructed to identify prognostic biomarkers for HCC through Cox survival analysis. Seven prognosis-associated mRNA co-expression modules were obtained by analyzing these differentially expressed mRNAs. An expression module including 120 mRNAs was significantly correlated with HCC patient survival. Combined with patient survival data, several mRNAs and miRNAs, including CHST4, SLC22A8, STC2, hsa-miR-326, and hsa-miR-21 were identified from the network to predict HCC patient prognosis. Clinical significance was investigated using tissue microarray analysis of samples from 258 patients with HCC. Functional annotation of hsa-miR-326 and hsa-miR-21-5p indicated specific associations with several cancer-related pathways. The present study provides a bioinformatics method for biomarker screening, leading to the identification of an integrated mRNA–miRNA–lncRNA regulatory network and their co-expression patterns in relation to predicting HCC patient survival. 相似文献
993.
采用纤维素黄原酸酯——过氧化氢构成氧化还原体系,把丙烯酰胺接枝到蔗渣纤维浆泊上。探讨了引发剂用量、初始pH值、单体比、反应温度、反应时间诸因素对接枝共聚反应的影响。 相似文献
994.
Vendela K. Lagerholm Edson Sandoval‐Castellanos Dorothee Ehrich Natalia I. Abramson Adam Nadachowski Daniela C. Kalthoff Mietje Germonpr Anders Angerbjrn John R. Stewart Love Daln 《Molecular ecology》2014,23(8):2060-2071
The Pleistocene glacial cycles resulted in significant changes in species distributions, and it has been discussed whether this caused increased rates of population divergence and speciation. One species that is likely to have evolved during the Pleistocene is the Norwegian lemming (Lemmus lemmus). However, the origin of this species, both in terms of when and from what ancestral taxon it evolved, has been difficult to ascertain. Here, we use ancient DNA recovered from lemming remains from a series of Late Pleistocene and Holocene sites to explore the species' evolutionary history. The results revealed considerable genetic differentiation between glacial and contemporary samples. Moreover, the analyses provided strong support for a divergence time prior to the Last Glacial Maximum (LGM), therefore likely ruling out a postglacial colonization of Scandinavia. Consequently, it appears that the Norwegian lemming evolved from a small population that survived the LGM in an ice‐free Scandinavian refugium. 相似文献
995.
996.
Xia C Xia Z 《Analytical and quantitative cytology and histology / the International Academy of Cytology [and] American Society of Cytology》2000,22(3):258-262
OBJECTIVE: To study the reliability of volume parameter measured on tissue sections through different sampling, measurement and calculation methods. STUDY DESIGN: The largest nuclear profile image under a 100x, NA 1.30 oil immersion objective of primary spermatocytes and spherical spermatoblasts on 11-micron-thick seminiferous tubule sections and tissue images, under a 20x objective, on 4-micron sections were captured. Their volumes were measured and calculated by the five methods provided by the Technology for Image and Graphics Engineering Research cell image analysis system. RESULTS: The nuclear volumes obtained by nucleator and area equivalent diameter on the largest nuclear profile image were almost the same, including binary images by automated and manual interactive nucleator and grey scale images only by the latter. Nuclear volumes, calculated by random Feret diameter and equivalent diameter of the perimeter, the minimal circumference of the largest nuclear profile binary image, were obviously larger than those of the nucleator and area equivalent diameter. Due to different-sized nuclear slices entrapped in the same section, those nuclear volumes from the seminiferous tubule tissue images were strikingly lower than that of the largest nuclei profile image. The shape factors of primary spermatocytes and spherical spermatoblast nuclei under 100x and 20x objectives were approximately the same. CONCLUSION: The sample preparation, sampling methods and calculation formulas suitable to nuclear form are necessary to obtain reproducible volume parameters. 相似文献
997.
厦门凤林红树林湿地大型底栖动物群落 总被引:8,自引:0,他引:8
为摸清厦门集美凤林红树林湿地的大型底栖动物群落结构及其多样性现状,2002年1、4、7和10月在厦门集美凤林红树林区进行大型底栖动物调查,4个季度共获得大型底栖动物42种。生物量优势种是软体动物门的珠带拟蟹守螺(Cerithideacingulata)和节肢动物门的弧边招潮(Ucaarcuata)。密度优势种是软体动物门的短拟沼螺(Assimineabrevicula)和环节动物门的沼蚓(Limnodriloidessp.)。集美凤林红树林区大型底栖动物年平均密度和年平均生物量分别为1,990ind./m2和139.0g/m2。密度的季节变化是:1月>4月>10月>7月,生物量的季节变化是1月>10月>4月>7月。聚类分析和数量分布表明,优势种珠带拟蟹守螺、短拟沼螺、弧边招潮和沼蚓的季节变化各不相同。与2002年10月深圳湾福田红树林区大型底栖动物群落的物种多样性指数平均值(0.56)比较,厦门凤林红树林区的平均值较高(2.66)。文中分析了影响大型底栖动物多样性的环境因素。 相似文献
998.
999.
The SNPlex genotyping system: a flexible and scalable platform for SNP genotyping. 总被引:10,自引:0,他引:10
Andreas R Tobler Sabine Short Mark R Andersen Teodoro M Paner Jason C Briggs Stephen M Lambert Priscilla P Wu Yiwen Wang Alexander Y Spoonde Ryan T Koehler Nicolas Peyret Caifu Chen Adam J Broomer Dana A Ridzon Hui Zhou Bradley S Hoo Kathleen C Hayashibara Lilley N Leong Congcong N Ma Barnet B Rosenblum Joseph P Day Janet S Ziegle Francisco M De La Vega Michael D Rhodes Kevin M Hennessy H Michael Wenz 《Journal of biomolecular techniques》2005,16(4):398-406
We developed the SNPlex Genotyping System to address the need for accurate genotyping data, high sample throughput, study design flexibility, and cost efficiency. The system uses oligonucleotide ligation/polymerase chain reaction and capillary electrophoresis to analyze bi-allelic single nucleotide polymorphism genotypes. It is well suited for single nucleotide polymorphism genotyping efforts in which throughput and cost efficiency are essential. The SNPlex Genotyping System offers a high degree of flexibility and scalability, allowing the selection of custom-defined sets of SNPs for medium- to high-throughput genotyping projects. It is therefore suitable for a broad range of study designs. In this article we describe the principle and applications of the SNPlex Genotyping System, as well as a set of single nucleotide polymorphism selection tools and validated assay resources that accelerate the assay design process. We developed the control pool, an oligonucleotide ligation probe set for training and quality-control purposes, which interrogates 48 SNPs simultaneously. We present performance data from this control pool obtained by testing genomic DNA samples from 44 individuals. in addition, we present data from a study that analyzed 521 SNPs in 92 individuals. Combined, both studies show the SNPlex Genotyping system to have a 99.32% overall call rate, 99.95% precision, and 99.84% concordance with genotypes analyzed by TaqMan probe-based assays. The SNPlex Genotyping System is an efficient and reliable tool for a broad range of genotyping applications, supported by applications for study design, data analysis, and data management. 相似文献
1000.