全文获取类型
收费全文 | 206834篇 |
免费 | 32230篇 |
国内免费 | 11017篇 |
专业分类
电工技术 | 14874篇 |
技术理论 | 9篇 |
综合类 | 14242篇 |
化学工业 | 39760篇 |
金属工艺 | 10584篇 |
机械仪表 | 12831篇 |
建筑科学 | 15936篇 |
矿业工程 | 5308篇 |
能源动力 | 5887篇 |
轻工业 | 20198篇 |
水利工程 | 4806篇 |
石油天然气 | 8630篇 |
武器工业 | 2102篇 |
无线电 | 27163篇 |
一般工业技术 | 27420篇 |
冶金工业 | 7276篇 |
原子能技术 | 2197篇 |
自动化技术 | 30858篇 |
出版年
2024年 | 897篇 |
2023年 | 2852篇 |
2022年 | 5676篇 |
2021年 | 7786篇 |
2020年 | 7126篇 |
2019年 | 7300篇 |
2018年 | 8041篇 |
2017年 | 8904篇 |
2016年 | 8729篇 |
2015年 | 11259篇 |
2014年 | 13271篇 |
2013年 | 15539篇 |
2012年 | 15315篇 |
2011年 | 15785篇 |
2010年 | 14950篇 |
2009年 | 13992篇 |
2008年 | 13974篇 |
2007年 | 12933篇 |
2006年 | 11912篇 |
2005年 | 9747篇 |
2004年 | 7501篇 |
2003年 | 6522篇 |
2002年 | 7041篇 |
2001年 | 6004篇 |
2000年 | 4558篇 |
1999年 | 3244篇 |
1998年 | 1815篇 |
1997年 | 1435篇 |
1996年 | 1273篇 |
1995年 | 1071篇 |
1994年 | 884篇 |
1993年 | 581篇 |
1992年 | 501篇 |
1991年 | 373篇 |
1990年 | 267篇 |
1989年 | 211篇 |
1988年 | 156篇 |
1987年 | 117篇 |
1986年 | 96篇 |
1985年 | 54篇 |
1984年 | 47篇 |
1983年 | 38篇 |
1982年 | 38篇 |
1981年 | 46篇 |
1980年 | 52篇 |
1979年 | 35篇 |
1978年 | 15篇 |
1977年 | 13篇 |
1959年 | 27篇 |
1951年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
1.
油液监测是判断设备健康状况和提供设备故障隐患预警的有效方法。综述了用于监测润滑油中磨损颗粒的最新各类在线传感器的基本原理,包括批量磁吸附式传感器、微流体电容传感器、金属扫描传感器、双层平面线圈传感器、超声波传感器和光学传感器等,并讨论各种传感方法的优缺点以及未来发展面临的挑战;指出了高通量、高灵敏度、能区别金属与非金属磨粒、可采集磨粒图像信息的集成式传感器是未来研究的重点,集成式、智能化、无线传输的传感器是未来研发方向。 相似文献
2.
Shanshan Zhuang Wenxiong Zheng Yunong Na Naiyi Chen Fan Gong Bingxuan Huang Stephen Brennan Charles Congyi Liu Jian Cheng Lukai Ma Huifan Liu 《International Journal of Food Science & Technology》2022,57(2):1093-1103
The β-Carotene (BC), an important precursor of vitamin A (VA), possesses antioxidant activity but is fat-soluble and has low bioavailability. In previous in-vitro assays evaluating antioxidant and 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) free radical scavenging, both BC and VA showed a strong ability to scavenge radicals and protected cells from oxidative stress. Here, we used artificially simulated gastrointestinal digestion and Caco-2 cell absorption models to evaluate the bioavailability of the BC during gastrointestinal digestion and absorption using high-performance liquid chromatography (HPLC) analysis. We observed high absorptive and transfer rates of BC and detected retinol metabolites (Vitamin A). Therefore, BC can be detected in the acidic gastrointestinal environment using HPLC. Optimised method provided better separation of BC and VA in the column, improving the accuracy of the test results. 相似文献
4.
Peiying Wang Juanli Zhao Yun Fan Wei Zhang Yuanyuan Cui Liangmiao Zhang Bin Liu Hongqiang Nian Yiran Li 《Ceramics International》2021,47(11):15023-15029
In this work, the composition-dependent point defect types and formation energies of RE2Hf2O7 (RE = La, Ce, Pr, Nd, Pm, Sm, Eu and Gd) as well as the oxygen diffusion behavior are systematically investigated by first-principles calculations. The possible defect reactions and dominant defect complexes under stoichiometric and non-stoichiometric conditions are revealed. It is found that O Frenkel pairs are the predominant defect in stoichiometric pyrochlore hafnates. Hf-RE cation anti-site defects, accompanied by RE vacancies and/or oxygen interstitials, are stable in the non-stoichiometric case of HfO2 excess. On the other hand, RE-Hf anti-site defects together with oxygen vacancies and/or RE interstitials are preferable in the case of RE2O3 excess. The energy barriers for the migration along the VO48f - VO48f pathway of pyrochlore hafnates were calculated to be between 0.81 eV and 0.89 eV. Based on these results, a defect engineering strategy is proposed and the pyrochlore hafnates investigated here are predicted to exhibit potential oxygen ionic conductivity. 相似文献
5.
Fan Deng-Ping Huang Ziling Zheng Peng Liu Hong Qin Xuebin Van Gool Luc 《国际自动化与计算杂志》2022,19(4):257-287
Machine Intelligence Research - This paper aims to conduct a comprehensive study on facial-sketch synthesis (FSS). However, due to the high cost of obtaining hand-drawn sketch datasets, there is a... 相似文献
6.
7.
Chenchen Zhou Jia Man Haibo Yu He Xia Luming Man Bin Qi Jianfeng Li 《Ceramics International》2021,47(8):10866-10872
Ceramic microparticles have great potentials in various fields such as materials engineering, biotechnology, microelectromechanical systems, etc. Morphology of the microparticle performs an important role on their application. To date, it remains difficult to find an effective and controllable way for fabricating nonspherical ceramic microparticles with 3D features. This work demonstrates a method that combines UV light lithography and single emulsion opaque-droplet-templated microfluidic molding to prepare the crescent-shaped ceramic microparticles. By tailoring the intensity of UV light and flow rate of fluid, the shapes of microparticles are accordingly tuned. Therefore, varieties of crescent-shaped microparticles and their variations have been fabricated. After sintering, the crescent-shaped alumina ceramic microparticles were obtained. Benefitting from the light absorption and scattering behavior of most ceramic nanoparticles, this system can serve as a general platform to produce crescent-shaped microparticles made from different materials, and hold great potentials for applications in microrobotics, structural materials in MEMS, and biotechnology. 相似文献
8.
9.
10.
针对颗粒滚动摩擦作用对筒仓中玉米颗粒的力链空间分布进行研究,通过EDEM离散元软件建立筒仓模型与仿真玉米颗粒模型进行卸粮仿真模拟,并与筒仓卸料实验作流态对比,验证模型与仿真结果的准确性。通过对模拟仓进行切片观察和数据处理,对比分析了不同摩擦情况下力链的细观参数随时间演化规律。模拟结果表明:颗粒间摩擦系数越大,卸粮完成的最终时间越长;颗粒间滚动摩擦系数越小,颗粒由整体流转变为管状流的时间越早。对于有漏斗的筒仓来说,减小颗粒间摩擦会改变整体流和管状流之间的极限,从而增加产生管状流的面积。标准滚动摩擦系数下玉米颗粒在卸料过程中会出现起拱-塌陷效应;减小滚动摩擦,玉米颗粒卸料较稳定,未出现起拱的应力突增、以及拱塌陷的应力衰减;增大颗粒间滚动摩擦不但会增加拱效应,且出现成拱高度距离漏斗口更高。 相似文献