全文获取类型
收费全文 | 1697篇 |
免费 | 162篇 |
国内免费 | 34篇 |
专业分类
电工技术 | 3篇 |
综合类 | 82篇 |
化学工业 | 427篇 |
金属工艺 | 16篇 |
机械仪表 | 99篇 |
建筑科学 | 2篇 |
轻工业 | 1034篇 |
水利工程 | 1篇 |
石油天然气 | 4篇 |
无线电 | 42篇 |
一般工业技术 | 172篇 |
冶金工业 | 2篇 |
原子能技术 | 4篇 |
自动化技术 | 5篇 |
出版年
2024年 | 10篇 |
2023年 | 33篇 |
2022年 | 109篇 |
2021年 | 111篇 |
2020年 | 71篇 |
2019年 | 59篇 |
2018年 | 70篇 |
2017年 | 61篇 |
2016年 | 71篇 |
2015年 | 96篇 |
2014年 | 86篇 |
2013年 | 111篇 |
2012年 | 120篇 |
2011年 | 133篇 |
2010年 | 89篇 |
2009年 | 77篇 |
2008年 | 60篇 |
2007年 | 89篇 |
2006年 | 77篇 |
2005年 | 63篇 |
2004年 | 59篇 |
2003年 | 45篇 |
2002年 | 46篇 |
2001年 | 32篇 |
2000年 | 17篇 |
1999年 | 14篇 |
1998年 | 9篇 |
1997年 | 11篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 12篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有1893条查询结果,搜索用时 0 毫秒
1.
2.
Patricia A. Miguez Stephen A. Tuin Adam G. Robinson Joyce Belcher Prapaporn Jongwattanapisan Kimberly Perley Vinicius de Paiva Gon«alves Arash Hanifi Nancy Pleshko Elisabeth R. Barton 《International journal of molecular sciences》2021,22(6)
This study evaluated the direct effect of a phytochemical, hesperidin, on pre-osteoblast cell function as well as osteogenesis and collagen matrix quality, as there is little known about hesperidin’s influence in mineralized tissue formation and regeneration. Hesperidin was added to a culture of MC3T3-E1 cells at various concentrations. Cell proliferation, viability, osteogenic gene expression and deposited collagen matrix analyses were performed. Treatment with hesperidin showed significant upregulation of osteogenic markers, particularly with lower doses. Mature and compact collagen fibrils in hesperidin-treated cultures were observed by picrosirius red staining (PSR), although a thinner matrix layer was present for the higher dose of hesperidin compared to osteogenic media alone. Fourier-transform infrared spectroscopy indicated a better mineral-to-matrix ratio and matrix distribution in cultures exposed to hesperidin and confirmed less collagen deposited with the 100-µM dose of hesperidin. In vivo, hesperidin combined with a suboptimal dose of bone morphogenetic protein 2 (BMP2) (dose unable to promote healing of a rat mandible critical-sized bone defect) in a collagenous scaffold promoted a well-controlled (not ectopic) pattern of bone formation as compared to a large dose of BMP2 (previously defined as optimal in healing the critical-sized defect, although of ectopic nature). PSR staining of newly formed bone demonstrated that hesperidin can promote maturation of bone organic matrix. Our findings show, for the first time, that hesperidin has a modulatory role in mineralized tissue formation via not only osteoblast cell differentiation but also matrix organization and matrix-to-mineral ratio and could be a potential adjunct in regenerative bone therapies. 相似文献
3.
Joe A. Potter Gareth W. Price Chelsy L. Cliff Colin R. Green Paul E. Squires Claire E. Hills 《International journal of molecular sciences》2021,22(7)
Chronic Kidney Disease (CKD) is associated with sustained inflammation and progressive fibrosis, changes that have been linked to altered connexin hemichannel-mediated release of adenosine triphosphate (ATP). Kidney fibrosis develops in response to increased deposition of extracellular matrix (ECM), and up-regulation of collagen I is an early marker of renal disease. With ECM remodeling known to promote a loss of epithelial stability, in the current study we used a clonal human kidney (HK2) model of proximal tubular epithelial cells to determine if collagen I modulates changes in cell function, via connexin-43 (Cx43) hemichannel ATP release. HK2 cells were cultured on collagen I and treated with the beta 1 isoform of the pro-fibrotic cytokine transforming growth factor (TGFβ1) ± the Cx43 mimetic Peptide 5 and/or an anti-integrin α2β1 neutralizing antibody. Phase microscopy and immunocytochemistry observed changes in cell morphology and cytoskeletal reorganization, whilst immunoblotting and ELISA identified changes in protein expression and secretion. Carboxyfluorescein dye uptake and biosensing measured hemichannel activity and ATP release. A Cytoselect extracellular matrix adhesion assay assessed changes in cell-substrate interactions. Collagen I and TGFβ1 synergistically evoked increased hemichannel activity and ATP release. This was paralleled by changes to markers of tubular injury, partly mediated by integrin α2β1/integrin-like kinase signaling. The co-incubation of the hemichannel blocker Peptide 5, reduced collagen I/TGFβ1 induced alterations and inhibited a positive feedforward loop between Cx43/ATP release/collagen I. This study highlights a role for collagen I in regulating connexin-mediated hemichannel activity through integrin α2β1 signaling, ahead of establishing Peptide 5 as a potential intervention. 相似文献
4.
制备皮胶原纤维固载Zr(IV)吸附剂(ZLCF),并考察ZLCF对水体中苯甲酸(BA)、邻苯二甲酸(o-PA)、对苯二甲酸(p-PA)和间苯二甲酸(m-PA)的吸附特性.研究表明:这4种苯羧酸的吸附平衡同时符合Langmuir和Freundlich方程,但随着它们的羧基数量和位置的不同,其吸附容量也随之变化.总体看,ZLCF对所研究的苯羧酸均具有较大的吸附容量.当苯羧酸溶液(10 m1)的初始浓度为6 mmol/L、吸附温度为293 K时,ZLCF(0.05 g)对BA、o-PA、m-PA和p-PA的吸附容量分别达0.4616、0.5892、0.4912和0.3138 mmol/g.吸附动力学研究表明:BA的吸附符合拟一级速率方程,边界层扩散为主控步骤;而o一PA、m-PA和p-PA的吸附符合拟二级速率方程,化学吸附为主控步骤. 相似文献
5.
6.
采用冰乙酸和胃蛋白酶依次对新鲜林蛙皮胶原蛋白进行提取.在冰乙酸提取过程中,首先通过控制单一因素变量对料液比、pH值、冰乙酸浓度、酸解时间和温度等5个因素对新鲜林蛙皮胶原蛋白提取率的影响进行研究,并采用正交实验考察林蛙皮胶原蛋白酸解提取的最佳工艺;其次,在冰乙酸提取的最优条件下,利用胃蛋白酶将酸解后的残余物进行再次酶解提取.实验结果表明,最佳酸解的工艺条件是:料液比为1∶30,pH为7.5,酸解时间为48 h,酸解温度为4℃,冰乙酸浓度为0.5 mol/L.在此工艺条件下,胶原蛋白的提取率为11.85%,胃蛋白酶对蛙皮残渣的提取率为5.25%,所得胶原蛋白的纯度为64.70%. 相似文献
7.
采用胶原材料制备了一种密实-疏松双层结构的牙周引导再生膜材料.为改善再生膜材料的物理化学性能,采用1-乙基-3-(3-二甲基氨丙基)碳二亚胺(EDC)和N-羟基琥珀酰亚胺(NHS)为交联剂对膜材料进行交联,考察了不同交联剂质量浓度对膜材料物理化学性能的影响,并通过差示扫描量热分析仪(DSC)、扫描电镜(SEM)、吸水率测试、膨胀动力学分析、抗酶解性能分析等手段对膜材料交联前后的结构与性能进行了研究.结果表明,以EDC/NHS为交联剂,在pH为5.5、EDC质量浓度为5 g/L、交联时间为24 h的条件下,引导再生胶原膜材料的综合性能达到最佳,进一步提高交联剂的浓度,材料物理化学性能的变化并不明显.采用EDC/NHS交联后,可显著改善再生膜材料的物理化学性能.交联后膜材料的变性温度和抗酶解性能显著提高,并且维持了密实-疏松的双层结构. 相似文献
8.
针对牙周膜胶原纤维组织切片在制作过程中对力度和方向非常敏感,极易造成组织变形和空间位移的问题,采用了一种有效的图像配准方法,以便后期对胶原纤维组织空间结构的重建。在Masson染色制成的兔牙周膜石蜡切片的基础上,利用高倍光学显微镜获得了牙周膜的序列切片图像;再采用基于正规步长梯度下降的二维刚性配准和基于对数域对称Demons微分同胚非刚性配准相结合的方法,对牙周膜序列切片图像进行级联配准。实验结果表明,相对于有限元非刚性配准而言,对数域对称Demons微分同胚非刚性配准方法具有较好的优势,其配准每张图片的平均时间为有限元法的3.1%,而配准均方误差平均为有限元法的89%。 相似文献
9.
10.
M. Gelinsky U. Knig A. Sewing W. Pompe 《Materialwissenschaft und Werkstofftechnik》2004,35(4):229-233
Porous scaffolds made from mineralised collagen – a biomimetic bone graft material Using biomimetically mineralised collagen type I, a new porous bone graft material has been developed, the composition of which mimics extracellular matrix of bone tissue. The pore structure is generated by a freeze drying process, whereas the pore size can be controlled by temperature and velocity of the freezing over a wide range. The structure is stabilized by crosslinking of the collagen with the water soluble carbodiimide derivative EDC. For the seeding with bone cells, pores with diameters of about 200 μm have turned out to be optimal. These scaffolds are elastic in the wet state which allow for cell culture experiments under mechanical stimulation. 相似文献