全文获取类型
收费全文 | 37310篇 |
免费 | 2642篇 |
国内免费 | 1631篇 |
专业分类
电工技术 | 2355篇 |
综合类 | 1519篇 |
化学工业 | 8872篇 |
金属工艺 | 3181篇 |
机械仪表 | 1478篇 |
建筑科学 | 475篇 |
矿业工程 | 396篇 |
能源动力 | 8308篇 |
轻工业 | 3190篇 |
水利工程 | 77篇 |
石油天然气 | 236篇 |
武器工业 | 85篇 |
无线电 | 3736篇 |
一般工业技术 | 4900篇 |
冶金工业 | 1081篇 |
原子能技术 | 394篇 |
自动化技术 | 1300篇 |
出版年
2025年 | 16篇 |
2024年 | 642篇 |
2023年 | 1019篇 |
2022年 | 1995篇 |
2021年 | 2390篇 |
2020年 | 1692篇 |
2019年 | 1612篇 |
2018年 | 1262篇 |
2017年 | 1509篇 |
2016年 | 1366篇 |
2015年 | 1267篇 |
2014年 | 1964篇 |
2013年 | 2185篇 |
2012年 | 2295篇 |
2011年 | 3107篇 |
2010年 | 2240篇 |
2009年 | 2026篇 |
2008年 | 1950篇 |
2007年 | 1939篇 |
2006年 | 1658篇 |
2005年 | 1339篇 |
2004年 | 1112篇 |
2003年 | 862篇 |
2002年 | 774篇 |
2001年 | 624篇 |
2000年 | 503篇 |
1999年 | 391篇 |
1998年 | 350篇 |
1997年 | 275篇 |
1996年 | 213篇 |
1995年 | 192篇 |
1994年 | 152篇 |
1993年 | 129篇 |
1992年 | 103篇 |
1991年 | 73篇 |
1990年 | 63篇 |
1989年 | 60篇 |
1988年 | 43篇 |
1987年 | 29篇 |
1986年 | 31篇 |
1985年 | 30篇 |
1984年 | 20篇 |
1983年 | 13篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1980年 | 16篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1975年 | 2篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Sabrina Valente Carmen Ciavarella Gloria Astolfi Elisa Bergantin Nico Curti Marina Buzzi Luigi Fontana Piera Versura 《International journal of molecular sciences》2022,23(18)
Blood-based preparations are used in clinical practice for the treatment of several eye disorders. The aim of this study is to analyze the effect of freeze-drying blood-based preparations on the levels of growth factors and wound healing behaviors in an in vitro model. Platelet-rich plasma (PRP) and serum (S) preparations from the same Cord Blood (CB) sample, prepared in both fresh frozen (FF) and freeze-dried (FD) forms (and then reconstituted), were analyzed for EGF and BDNF content (ELISA Quantikine kit). The human MIO-M1 glial cell line (Moorfield/Institute of Ophthalmology, London, UK) was incubated with FF and FD products and evaluated for cell migration with scratch-induced wounding (IncuCyte S3 Essen BioScience), proliferation with cyclin A2 and D1 gene expression, and activation with vimentin and GFAP gene expression. The FF and FD forms showed similar concentrations of EGF and BDNF in both the S and PRP preparations. The wound healing assay showed no significant difference between the FF and FD forms for both S and PRP. Additionally, cell migration, proliferation, and activation did not appear to change in the FD forms compared to the FF ones. Our study showed that reconstituted FD products maintained the growth factor concentrations and biological properties of FF products and could be used as a functional treatment option. 相似文献
62.
Bowen Yan Haoyu Zheng Yuwei Sang Yan Wang Jian Sun Fengcheng Li Jiayu Wang Xiaoxue Wang 《International journal of molecular sciences》2022,23(16)
Lesion mimic mutants are an ideal model system for elucidating the molecular mechanisms of programmed cell death and defense responses in rice. In this study, we identified a lesion mimic mutant termed miner infection like 1-1 (mil1-1). The mil1-1 exhibited lesions on the leaves during development, and the chloroplasts of mil1-1 leaves were disrupted. Reactive oxygen species were found to accumulate in mil1-1 leaves. Cell death and DNA fragmentation were observed in mil1-1 leaves, indicating that the cells in the spots of mil1-1 leaves experienced programmed cell death. Most agronomic traits decreased in mil1-1, suggesting that the growth retardation in mil1-1 caused reduced per-plant grain yield. However, the mutation of MIL1 activated the expression of pathogen response genes and enhanced resistance to bacterial blight. The MIL1 gene was cloned using the positional cloning approach. A missense mutation 751 bp downstream of ATG was found in mil1-1. The defects of mil1-1 were able to be rescued by delivering a wild-type MIL1 gene into mil1-1. MIL1 encoded hydroperoxide lyase 3 (OsHPL3), and the expression of OsHPL3 was induced via hormone and abiotic stresses. Our findings provide insights into the roles of MIL1 in regulating programmed cell death, development, yield, and defense responses in rice. 相似文献
63.
Glioblastoma (GB) cells physically interact with peritumoral pericytes (PCs) present in the brain microvasculature. These interactions facilitate tumor cells to aberrantly increase and benefit from chaperone-mediated autophagy (CMA) in the PC. GB-induced CMA leads to major changes in PC immunomodulatory phenotypes, which, in turn, support cancer progression. In this review, we focus on the consequences of the GB-induced up-regulation of CMA activity in PCs and evaluate how manipulation of this process could offer new strategies to fight glioblastoma, increasing the availability of treatments for this cancer that escapes conventional therapies. We finally discuss the use of modified PCs unable to increase CMA in response to GB as a cell therapy alternative to minimize undesired off-target effects associated with a generalized CMA inhibition. 相似文献
64.
Daisuke Akahori Naoki Inui Yusuke Inoue Hideki Yasui Hironao Hozumi Yuzo Suzuki Masato Karayama Kazuki Furuhashi Noriyuki Enomoto Tomoyuki Fujisawa Takafumi Suda 《International journal of molecular sciences》2022,23(16)
Pulmonary fibrosis is a progressive and fatal disorder characterized by dysregulated repair after recurrent injury. Destruction of the lung architecture with excess extracellular matrix deposition induces respiratory failure with hypoxia and progressive dyspnea. The impact of hypoxia on pulmonary endothelial cells during pulmonary fibrogenesis is unclear. Using a magnetic-activated cell sorting system, pulmonary endothelial cells were isolated from a mouse model of pulmonary fibrosis induced by intratracheally administered bleomycin. When endothelial cells were exposed to hypoxic conditions, a hypoxia-inducible factor (HIF)-2α protein was detected in CD31- and α-smooth muscle actin (SMA)-positive cells. Levels of plasminogen activator inhibitor 1, von Willebrand factor, and matrix metalloproteinase 12 were increased in endothelial cells isolated from bleomycin-treated mice exposed to hypoxic conditions. When endothelial cells were cultured under hypoxic conditions, levels of fibrotic mediators, transforming growth factor-β and connective tissue growth factor, were elevated only in endothelial cells from bleomycin-treated and not from saline-treated lungs. The increased expression of α-SMA and mesenchymal markers and collagen production in bleomycin- or hypoxia-stimulated endothelial cells were further elevated in endothelial cells from bleomycin-treated mouse lungs cultured under hypoxic conditions. Exposure to hypoxia damaged endothelial cells and enhanced fibrogenesis-related damage in bleomycin-treated pulmonary endothelial cells. 相似文献
65.
66.
Joon Seok Lee Hyun Geun Cho Jeong Yeop Ryu Eun Jung Oh Hyun Mi Kim Suin Kwak Seok-Jong Lee Jongmin Lee Sang Yub Lee Seung Huh Ji Yoon Kim Ho Yun Chung 《International journal of molecular sciences》2022,23(16)
Arteriovenous malformation (AVM) is characterized by high-flow blood vessels connecting arteries and veins without capillaries. This disease shows increased angiogenesis and a pathophysiological hypoxic environment in proximal tissues. Here, we analyzed the effects of hypoxia on angiogenesis in the endothelial cells (ECs) of AVM and normal tissues. ECs from human normal and AVM tissues were evaluated using immunocytochemistry with CD31. In vitro tube formation under hypoxia was tested in both ECs using Matrigel. The relative expression of angiogenesis-related genes was measured using real-time PCR. Under normoxia, CD31 was significantly higher in AVM ECs (79.23 ± 0.65%) than in normal ECs (74.15 ± 0.70%). Similar results were observed under hypoxia in AVM ECs (63.85 ± 1.84%) and normal ECs (60.52 ± 0.51%). In the tube formation test under normoxic and hypoxic conditions, the junction count and total vessel length were significantly greater in AVM ECs than normal ECs. Under both normoxia and hypoxia, the angiogenesis-related gene FSTL1 showed a significantly higher expression in AVM ECs than in normal ECs. Under hypoxia, CSPG4 expression was significantly lower in AVM ECs than in normal ECs. Accordingly, the angiogenic effect was increased in AVM ECs compared with that in normal ECs. These results provide a basic knowledge for an AVM treatment strategy. 相似文献
67.
研究功能知识是现代设计过程中的一个重要环节,从功能的数学表达方法着手,研究单输入单输出系统的输入输出功能特征矢量,得出基本变换单元的功能变换矩阵。再通过分析功能变换矩阵类型、方向信息的转换和特征值信息的转换,得出一种方便于数据库储存和后续方案设计运算的知识库。 相似文献
68.
69.
In a recent article, Chen et al. [Electrochimica Acta, 2014, 130: 279] presented their fabrication and characterization results on a graphene/n-Si solar cell where the Au nanoparticles were inserted in graphene to increase its optical and electrical properties. The higher efficiency of the device was attributed to increased conductivity of graphene after doping with Au nanoparticles. However, the knowledge in the field of Schottky diode solar cells relates this to increased band bending at the junction. Also, to explain the instability behaviour, they concluded that the growth of silicon oxide on the Si surface or oxygen adsorption on the window layer resulted in the device performance increasing initially and decreasing in the end. However, this instability seems to be due to variation in series resistance reduced at the beginning because of slightly lowered Fermi level and increased at the end by the self-compensation by deep in-diffusion of Au nanoparticles into n-Si layer. We also propose that inserting a very thin p-type layer at the junction will enhance the carrier collection and performance of this device. 相似文献
70.
对多壁碳纳米管(MWCNT)进行了预处理.红外光谱分析证明:预处理后,MWCNT的表面生成了较多的活性官能团.以处理后的MWCNT为载体、乙二醇为还原剂,用交替微波法制备了Pt/CNT催化剂.相比于在10%HF中搅拌和在10%HF与浓HNO_3混合溶液中搅拌,在10%HF中搅拌再用浓HNO_3回流后的MWCNT作为载体制备的Pt/CNT催化剂,粒径为3.76 nm,具有最大的活性面积,对甲醇的氧化性能最好. 相似文献