全文获取类型
收费全文 | 51630篇 |
免费 | 6262篇 |
国内免费 | 21981篇 |
出版年
2024年 | 461篇 |
2023年 | 1457篇 |
2022年 | 2439篇 |
2021年 | 2951篇 |
2020年 | 2599篇 |
2019年 | 3206篇 |
2018年 | 2343篇 |
2017年 | 2052篇 |
2016年 | 2388篇 |
2015年 | 3145篇 |
2014年 | 4311篇 |
2013年 | 3984篇 |
2012年 | 5265篇 |
2011年 | 5170篇 |
2010年 | 4003篇 |
2009年 | 4044篇 |
2008年 | 4352篇 |
2007年 | 4107篇 |
2006年 | 3753篇 |
2005年 | 3159篇 |
2004年 | 2431篇 |
2003年 | 2113篇 |
2002年 | 1861篇 |
2001年 | 1773篇 |
2000年 | 1605篇 |
1999年 | 1073篇 |
1998年 | 597篇 |
1997年 | 429篇 |
1996年 | 371篇 |
1995年 | 286篇 |
1994年 | 206篇 |
1993年 | 197篇 |
1992年 | 231篇 |
1991年 | 201篇 |
1990年 | 160篇 |
1989年 | 122篇 |
1988年 | 138篇 |
1987年 | 115篇 |
1986年 | 106篇 |
1985年 | 122篇 |
1984年 | 61篇 |
1983年 | 56篇 |
1982年 | 85篇 |
1981年 | 45篇 |
1980年 | 13篇 |
1979年 | 21篇 |
1978年 | 16篇 |
1957年 | 22篇 |
1953年 | 13篇 |
1950年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
21.
22.
Yan Xue Liu Jia Wu Ke-Xin Yang Nan Pan Li-Ben Song Ying Liu Yang Tang Zhong-Hua 《Journal of Plant Growth Regulation》2022,41(6):2421-2434
Journal of Plant Growth Regulation - Early-spring plants are a special type of plant that complete their life cycle promptly in cold, early spring. Very little effort has been made into researching... 相似文献
23.
In eukaryotes, small RNAs play important roles in both gene regulation and resistance to viral infection. Argonaute proteins have been identified as a key component of the effector complexes of various RNA-silencing pathways, but the mechanistic roles of Argonaute proteins in these pathways are not clearly understood. To address this question, we performed single-molecule fluorescence experiments using an RNA-induced silencing complex (core-RISC) composed of a small RNA and human Argonaute 2. We found that target binding of core-RISC starts at the seed region of the guide RNA. After target binding, four distinct reactions followed: target cleavage, transient binding, stable binding, and Argonaute unloading. Target cleavage required extensive sequence complementarity and accelerated core-RISC dissociation for recycling. In contrast, the stable binding of core-RISC to target RNAs required seed-match only, suggesting a potential explanation for the seed-match rule of microRNA (miRNA) target selection. [BMB Reports 2015; 48(12): 643-644] 相似文献
24.
25.
Zhan Wang Yuxin Song Xingwen Han Peng Qu Wenji Wang 《Journal of cellular physiology》2020,235(4):3634-3645
Exosomes derived from differentiated P12 cells and MSCs were proved to suppress apoptosis of neuron cells, and phosphatase and tensin homolog pseudogene 1 (PTENP1) was reported to inhibit cell proliferation. In this study, we aimed to investigate the role of PTENP1 in the process of post-spinal cord injury (SCI) recovery, so as to evaluate the therapeutic effects of exosomes derived from MSCs transfected with PTENP1 short hairpin RNA (shRNA), as a type of novel biomarkers in the treatment of SCI. Electron microscopy was used to observe the morphology of different exosomes. Real-time polymerase chain reaction and western blot, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays, flow cytometry, Nissl staining, immunohistochemistry assay, and terminal deoxynucleotidyl transferase dUTP nick end labeling assay were conducted to investigate and validate the underlying molecular signaling pathway. PTENP1-shRNA downregulated PTENP1 and PTEN while upregulating miR-21 and miR-19b. PTENP1-shRNA also accelerated cell apoptosis and reduced cell viability. In addition, PTENP1 reduced the miR-21 and miR-19b expression by directly targeting miR-21 and miR-19b. Meanwhile, both miR-21 and miR-19b reduced the expression of PTEN by directly targeting the 3′-untranslated region of PTEN. Furthermore, PTEN level and apoptosis index of neuron cells was the highest in the SCI group, while the treatment with exosomes+PTENP1-shRNA reduced the PTEN expression to a level similar to that in the sham group. Finally, PTENP1 inhibited miR-21 and miR-19b expression but upregulated PTEN expression. The upregulation of miR-21/miR-19b also suppressed the apoptosis of neuron cells by downregulating the PTEN expression. PTENP1 is involved in the recovery of SCI by regulating the expression of miR-19b and miR-21, and exosomes from PTENP1-shRNA-transfected cells may be used as a novel biomarker in SCI treatment. 相似文献
26.
Ying Jin Dan Long Juan Li Ruichao Yu Yueming Song Jie Fang Xi Yang Shu Zhou Shishu Huang Zhihe Zhao 《Journal of cellular physiology》2019,234(9):14838-14851
Bone and tooth, fundamental parts of the craniofacial skeleton, are anatomically and developmentally interconnected structures. Notably, pathological processes in these tissues underwent together and progressed in multilevels. Extracellular vesicles (EVs) are cell-released small organelles and transfer proteins and genetic information into cells and tissues. Although EVs have been identified in bone and tooth, particularly EVs have been identified in the bone formation and resorption, the concrete roles of EVs in bone and tooth development and diseases remain elusive. As such, we review the recent progress of EVs in bone and tooth to highlight the novel findings of EVs in cellular communication, tissue homeostasis, and interventions. This will enhance our comprehension on the skeletal biology and shed new light on the modulation of skeletal disorders and the potential of genetic treatment. 相似文献
27.
The objective of this investigation was to find a simple method for the production of phenolic-rich products and sugar derivatives via separation of liquefied lignocellulosic materials. After liquefaction, the liquefied products were separated by addition of a sufficient amount of water. It was found that those hydrophobic phenolics could be largely separated from aqueous solutions. Preparation of polyurethane foams using biopolyol and isocyanate was studied. Water was used as an environmentally friendly blowing agent. The factors influencing the cell structure of foams such as catalyst, dosage of blowing agent, and mass ratio of biopolyol to PEG were studied. The microstructure of synthesized foams was characterized by SEM. 相似文献
28.
29.
30.