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   4453篇
  免费   385篇
  国内免费   275篇
  5113篇
  2024年   11篇
  2023年   46篇
  2022年   135篇
  2021年   231篇
  2020年   165篇
  2019年   186篇
  2018年   201篇
  2017年   134篇
  2016年   183篇
  2015年   289篇
  2014年   356篇
  2013年   330篇
  2012年   414篇
  2011年   349篇
  2010年   210篇
  2009年   224篇
  2008年   253篇
  2007年   200篇
  2006年   164篇
  2005年   134篇
  2004年   111篇
  2003年   120篇
  2002年   111篇
  2001年   80篇
  2000年   73篇
  1999年   52篇
  1998年   30篇
  1997年   36篇
  1996年   37篇
  1995年   43篇
  1994年   34篇
  1993年   25篇
  1992年   27篇
  1991年   22篇
  1990年   17篇
  1989年   14篇
  1988年   8篇
  1987年   8篇
  1986年   10篇
  1985年   3篇
  1984年   6篇
  1983年   6篇
  1982年   3篇
  1977年   4篇
  1975年   3篇
  1974年   2篇
  1971年   3篇
  1970年   1篇
  1969年   1篇
  1967年   1篇
排序方式: 共有5113条查询结果,搜索用时 0 毫秒
981.
14-3-3 proteins are highly conserved in species ranging from yeast to mammals and regulate numerous signalling pathways via direct interactions with proteins carrying phosphorylated 14-3-3–binding motifs. Recent studies have shown that 14-3-3 proteins can also play a role in viral infections. This review summarizes the biological functions of 14-3-3 proteins in protein trafficking, cell-cycle control, apoptosis, autophagy and other cell signal transduction pathways, as well as the associated mechanisms. Recent findings regarding the role of 14-3-3 proteins in viral infection and innate immunity are also reviewed.  相似文献   
982.
Inorganic CsPbI3 perovskite with an optical bandgap ranging from 1.67 to 1.75 eV is a promising light-harvesting material as a top cell in tandem solar cells, but its high fabrication temperature can damage the middle layers or the bottom subcells. Here, an additive-involved leaching method to fabricate CsPbI3 perovskite films is demonstrated, which can decrease the preparation temperature to 100 °C. The CsPbI3 perovskite films with high crystallinity are achieved by a solution assisted reaction between DMAPbI3 and Cs4PbI6 with the leaching of DMA+, Cs+, and I. The as-prepared CsPbI3 perovskite films exhibit much superior stability compared to their high-temperature counterparts. As a result, a power conversion efficiency of over 16% is obtained, and the unencapsulated device maintains over 93% of the initial efficiency after aging for 30 days in air with a relative humidity of 10%.  相似文献   
983.
Hadal environments (depths below 6,000 m) are characterized by extremely high hydrostatic pressures, low temperatures, a scarce food supply, and little light. The evolutionary adaptations that allow vertebrates to survive in this extreme environment are poorly understood. Here, we constructed a high-quality reference genome for Yap hadal snailfish (YHS), which was captured at a depth of ~7,000 m in the Yap Trench. The final YHS genome assembly was 731.75 Mb, with a contig N50 of 0.75 Mb and a scaffold N50 of 1.26 Mb. We predicted 24,329 protein-coding genes in the YHS genome, and 24,265 of these genes were successfully functionally annotated. Phylogenetic analyses suggested that YHS diverged from a Mariana Trench snailfish approximately 0.92 million years ago. Many genes associated with DNA repair show evidence of positive selection and have expanded copy numbers in the YHS genome, possibly helping to maintain the integrity of DNA under increased hydrostatic pressure. The levels of trimethylamine N-oxide (TMAO), a potent protein stabilizer, are much higher in the muscles of YHS than in those of shallow-water fish. This difference is perhaps due to the five copies of the TMAO-generating enzyme flavin-containing monooxygenase-3 gene (fmo3) in the YHS genome and the abundance of trimethylamine (TMA)-generating bacteria in the YHS gut. Thus, the high TMAO content might help YHS adapt to high hydrostatic pressure by improving protein stability. Additionally, the evolutionary features of the YHS genes encoding sensory-related proteins are consistent with the scarce food supply and darkness in the hadal environments. These results clarify the molecular mechanisms underlying the adaptation of hadal organisms to the deep-sea environment and provide valuable genomic resources for in-depth investigations of hadal biology.  相似文献   
984.
Zhou  Yu  Zhong  Zhuohang  Dai  Mingyue  Shao  Chunqiang 《Plasmonics (Norwell, Mass.)》2021,16(4):1119-1126

In this paper, hyperbolic plasmonic responses of phosphorene under uniaxial strains have been explored within density functional theory. In the hyperbolic regime, plasmonic slab waveguide modes are found only along armchair direction. Then, uniaxial strains up to 10% have been applied along zigzag and armchair directions, which can significantly modify its plasmonic responses. Under appropriate strain, the signs of permittivities along two in-plane directions can be even reversed, causing switching of the propagating direction of the plasmonic modes into zigzag direction. Our investigations may give a general idea about how to control the hyperbolic plasmonic modes in phosphorene via strain.

  相似文献   
985.
986.
987.
Chordoma is a malignant bone tumor originating from the embryonic remnants of the notochord. lncRNAs act as competing endogenous RNAs (ceRNAs) and play a critical role in tumor pathology. However, the biological role of lncRNA-NONHSAT024778 and the underlying molecular mechanism in chordoma remains unknown. qRT-PCR was used to analyze the expression changes of NONHSAT024778 and miR-1290 in chordoma tissues and cell lines. Bioinformatics analysis and luciferase reporter assay were applied to detect the targeting binding effect between NONHSAT024778 and miR-1290, and between Robo1 and miR-1290. The effect of NONHSAT024778 on chordoma cell proliferation and invasion and its regulation of miR-1290 by acting as a ceRNA were also investigated. An increased NONHSAT024778 expression was correlated with a decreased miR-1290 level in chordoma tissues. NONHSAT024778 knockdown suppressed the proliferation and invasion of chordoma cells. miR-1290 restored expression rescued the carcinogenic function of NONHSAT024778. Bioinformatics analysis showed that NONHSAT024778 acted as ceRNA to regulate Robo1 via sponging miR-1290 in chordoma cells, thereby promoting chordoma cell malignant progression. In vivo results confirmed the anti-tumor effects of NONHSAT024778 knockdown activating miR-1290 to inhibit the oncogene Robo1. NONHSAT024778 is substantially overexpressed, whereas miR-1290 is decreased in chordoma tissue. NONHSAT024778-miR-1290-Robo1 axis plays a critical role in chordoma tumorigenesis and might be a potential predictive biomarker for the diagnosis and therapeutic target among patients with chordoma.  相似文献   
988.
Background and AimsThe ribosomal DNA (rDNA) gene family, encoding ribosomal RNA (rRNA), has long been regarded as an archetypal example illustrating the model of concerted evolution. However, controversy is arising, as rDNA in many eukaryotic species has been proved to be polymorphic. Here, a metagenomic strategy was applied to detect the intragenomic polymorphism as well as the evolutionary patterns of 26S rDNA across the genus Camellia.MethodsDegenerate primer pairs were designed to amplify the 26S rDNA fragments from different Camellia species. The amplicons were then paired-end sequenced on the Illumina MiSeq platform.Key ResultsAn extremely high level of rDNA polymorphism existed universally in Camellia. However, functional rDNA was still the major component of the family, and was relatively conserved among different Camellia species. Sequence variations mainly came from rRNA pseudogenes and favoured regions that are rich in GC. Specifically, some rRNA pseudogenes have existed in the genome for a long time, and have even experienced several expansion events, which has greatly enriched the abundance of rDNA polymorphism.Conclusions Camellia represents a group in which rDNA is subjected to a mixture of concerted and birth-and-death evolution. Some rRNA pseudogenes may still have potential functions. Conversely, when released from selection constraint, they can evolve in the direction of decreasing GC content and structural stability through a methylation-induced process, and finally be eliminated from the genome.  相似文献   
989.
This study tested the hypothesis that Jagged2/Notches promoted the endothelial-mesenchymal transition (endMT)-mediated pulmonary arterial hypertension (PAH) (i.e. induction by monocrotaline [MCT]/63 mg/kg/subcutaneous injection) through increasing the expression of GATA-binding factors which were inhibited by propylthiouracil (PTU) (i.e. 0.1% in water for daily drinking since Day 5 after PAH induction) in rodent. As compared with the control (i.e. HUVECs), the protein expressions of GATAs (3/4/6) and endMT markers (Snail/Zeb1/N-cadherin/vimentin/fibronectin/α-SMA/p-Smad2) were significantly reduced, whereas the endothelial-phenotype markers (CD31/E-cadherin) were significantly increased in silenced JAG2 gene or in silenced GATA3 gene of HUVECs (all p < 0.001). As compared with the control, the protein expressions of intercellular signallings (GATAs [3/4/6], Jagged1/2, notch1/2 and Snail/Zeb1/N-cadherin/vimentin/fibronectin/α-SMA/p-Smad2) were significantly upregulated in TGF-ß/monocrotaline-treated HUVECs that were significantly reversed by PTU treatment (all p < 0.001). By Day 42, the results of animal study demonstrated that the right-ventricular systolic-blood-pressure (RVSBP), RV weight (RVW) and lung injury/fibrotic scores were significantly increased in MCT group than sham-control (SC) that were reversed in MCT + PTU groups, whereas arterial oxygen saturation (%) and vasorelaxation/nitric oxide production of PA exhibited an opposite pattern of RVW among the groups (all p < 0.0001). The protein expressions of hypertrophic (ß-MHC)/pressure-overload (BNP)/oxidative-stress (NOX-1/NOX-2) biomarkers in RV and the protein expressions of intercellular signalling (GATAs3/4/6, Jagged1/2, notch1/2) and endMT markers (Snail/Zeb1/N-cadherin/vimentin/fibronectin/TGF-ß/α-SMA/p-Smad2) in lung parenchyma displayed an identical pattern of RVW among the groups (all p < 0.0001). Jagged-Notch-GATAs signalling, endMT markers and RVSBP that were increased in PAH were suppressed by PTU.  相似文献   
990.
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