全文获取类型
收费全文 | 16783篇 |
免费 | 2080篇 |
国内免费 | 1268篇 |
专业分类
电工技术 | 1441篇 |
综合类 | 1830篇 |
化学工业 | 2163篇 |
金属工艺 | 1186篇 |
机械仪表 | 908篇 |
建筑科学 | 1319篇 |
矿业工程 | 844篇 |
能源动力 | 456篇 |
轻工业 | 1895篇 |
水利工程 | 600篇 |
石油天然气 | 606篇 |
武器工业 | 210篇 |
无线电 | 1981篇 |
一般工业技术 | 1477篇 |
冶金工业 | 619篇 |
原子能技术 | 212篇 |
自动化技术 | 2384篇 |
出版年
2024年 | 107篇 |
2023年 | 317篇 |
2022年 | 732篇 |
2021年 | 885篇 |
2020年 | 654篇 |
2019年 | 480篇 |
2018年 | 496篇 |
2017年 | 581篇 |
2016年 | 509篇 |
2015年 | 825篇 |
2014年 | 928篇 |
2013年 | 1072篇 |
2012年 | 1405篇 |
2011年 | 1391篇 |
2010年 | 1290篇 |
2009年 | 1227篇 |
2008年 | 1298篇 |
2007年 | 1277篇 |
2006年 | 1108篇 |
2005年 | 793篇 |
2004年 | 578篇 |
2003年 | 498篇 |
2002年 | 460篇 |
2001年 | 477篇 |
2000年 | 308篇 |
1999年 | 126篇 |
1998年 | 69篇 |
1997年 | 44篇 |
1996年 | 45篇 |
1995年 | 22篇 |
1994年 | 22篇 |
1993年 | 22篇 |
1992年 | 18篇 |
1991年 | 16篇 |
1990年 | 9篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1976年 | 3篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1959年 | 3篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
2.
Nan Wu Xiaodong Li Mu Zhang Yi Ren Qi Zhu Haijun Peng Hongqiang Ru Xudong Sun 《Journal of the European Ceramic Society》2021,41(4):2898-2907
Refining ceramic microstructures to the nanometric range to minimize light scattering provides an interesting methodology for developing novel optical ceramic materials. In this work, we reported the fabrication and properties of a new nanocomposite optical ceramic of Gd2O3-MgO. The citric acid sol-gel combustion method was adopted to fabricate Gd2O3-MgO nanocomposites with fine-grain sizes, dense microstructures and homogeneous phase domains. Nanopowders with low agglomeration and improved sinterability can be obtained by elaborating Φ values. Further refining of the microstructure of the nanocomposites was achieved by elaborating the hot-pressing conditions. The sample sintered at 65 MPa and 1300 °C showed a quite high hardness value of 14.3 ± 0.2 GPa, a high transmittance of 80.3 %–84.7 % over the 3?6 μm wavelength range, due mainly to its extremely fine-grain size of Gd2O3 and MgO (93 and 78 nm, respectively) and high density. 相似文献
3.
4.
红外偏振光治疗仪是一种将红外技术与电子技术应用到医学领域的康复理疗设备,主要用于软组织损伤和慢性疼痛的康复治疗,已在医院得到了推广使用。然而,现有医院使用的台式治疗仪由于体积大、售价高等特点,不方便居家使用。为了开发体积小、售价低、家庭可用的红外偏振光治疗仪,满足家用市场的潜在需求,本文提出了一种新的便携手持式红外偏振光治疗仪,并开发了该智能控制系统。本文首先介绍了一种新的家用手持式治疗仪应具备的特点和关键技术指标,在此基础上设计了手持式治疗仪的硬件总体方案和软件架构,简要介绍了该治疗仪的一些关键技术,最终实现了治疗仪样机的研制。为了验证该样机的性能,本文通过大量的测试,结果表明,研制的手持式红外偏振光治疗仪在关键参数指标上达到了医院同类产品的水平,能够很好地满足家用的需求,具有良好的市场前景。 相似文献
5.
经过涂装现场诸多因素的排除、面漆材料的分析及试验验证,发现了研磨印形成的主要原因。由此调整了相关的面漆材料,找到了消除汽车车身涂装沙滩银色研磨印缺陷的方法。 相似文献
6.
Longbang Qing Yuehua Cheng Ru Mu 《Fatigue & Fracture of Engineering Materials & Structures》2019,42(11):2533-2543
Based on theoretical analysis and numerical simulation, the impact of steel fibres on the stress intensity factor (SIF) at the crack tip for cementitious composite was studied. The enhanced toughness of steel fibre reinforced cementitious composite (SFRC) in resisting cracks was explained by the decrement of SIF caused by steel fibre inclusions at the crack tip of the composite. The equivalent initial fracture toughness was used to characterize the crack initiation of SFRC. A simplified method for determining the of SFRC was proposed based on a linear regression method. Fracture tests were conducted on three‐point bending notched beams with different steel fibre volume fractions and specimen sizes to study the crack initiation behaviour of aligned steel fibre reinforced cementitious composite (ASFRC). of ASFRC was calculated, and the size effect of was analysed. The results showed that slightly increased with the steel fibre volume fraction and gradually became stable. For the tested specimens, whose heights varied between 40 and 100 mm, the specimen size had little impact on the . 相似文献
7.
Hong Wei Li Li Ya‐Li Ma Ru‐Xue Liu Shuang‐Yan Meng Li‐Tong Niu Zhe Zhang Zhi‐Wang Yang 《火与材料》2019,43(7):868-879
Through the simple precipitation of palygorskite (PGS) by zinc borate (ZB) (to make PGS@ZB) and the decoration of PGS@ZB by dodecylamine (N), a novel organic‐inorganic@inorganic hybrid flame retardant of PGS@ZB‐N was prepared and was incorporated with ethylene vinyl acetate copolymer (EVA) to improve its flame retardance. The structure and morphology of PGS@ZB‐N were characterized by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), and scanning electron microscopy (SEM), and it was confirmed that the PGS@ZB‐N hybrid had been successfully prepared. The flame retardancy and burning behavior of EVA/PGS@ZB‐N/EG (EG = expandable graphite) composite were studied through thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL‐94 (by the vertical burning test), and cone calorimeter test (CCT) characterizations. The prepared EVA/PGS@ZB‐N/EG composite obtained an LOI value of 41.2% with the addition of 30 wt% PGS@ZB‐N/EG. It was found that EVA/PGS@ZB‐N/EG was protected through a gas phase and condensed phase alternating synergistic effect mechanism. 相似文献
8.
The hippocampus is crucial in learning, memory and emotion processing, and is involved in the development of different neurological and neuropsychological disorders. Several epigenetic factors, including DNA methylation, histone modifications and non-coding RNAs, have been shown to regulate the development and function of the hippocampus, and the alteration of epigenetic regulation may play important roles in the development of neurocognitive and neurodegenerative diseases. This review summarizes the epigenetic modifications of various cell types and processes within the hippocampus and their resulting effects on cognition, memory and overall hippocampal function. In addition, the effects of exposure to radiation that may induce a myriad of epigenetic changes in the hippocampus are reviewed. By assessing and evaluating the current literature, we hope to prompt a more thorough understanding of the molecular mechanisms that underlie radiation-induced epigenetic changes, an area which can be further explored. 相似文献
9.
分析了根据顶梁偏摆量设计液压支架四连杆的过程,简化支架模型写出了四连杆型液压支架的运动学和力学方程,提出一种基于Matlab设计液压支架四连杆和求解其运动学非线性方程组的方法,并编制成可视化计算程序。给出一设计要求实例,应用此程序设计及计算液压支架参数,用Auto CAD作图验证,计算结果准确可靠。 相似文献
10.
讨论了输出终端带不等式约束情形的多输入多输出系统,说明了这些约束可以通过修改输入柔化系数而使其得以满足,在柔化系数的选择范围确定过程中,为了避免矩阵求逆,采用利用已知数据辨识参数的方法来确定柔化系数,从而使得问题简化。降低了计算量且加快了收敛速度。 相似文献