全文获取类型
收费全文 | 321303篇 |
免费 | 26483篇 |
国内免费 | 13355篇 |
专业分类
电工技术 | 18551篇 |
技术理论 | 34篇 |
综合类 | 20052篇 |
化学工业 | 54566篇 |
金属工艺 | 18724篇 |
机械仪表 | 20842篇 |
建筑科学 | 25274篇 |
矿业工程 | 10827篇 |
能源动力 | 8919篇 |
轻工业 | 19640篇 |
水利工程 | 5786篇 |
石油天然气 | 21566篇 |
武器工业 | 2687篇 |
无线电 | 35496篇 |
一般工业技术 | 37679篇 |
冶金工业 | 16747篇 |
原子能技术 | 3293篇 |
自动化技术 | 40458篇 |
出版年
2024年 | 1452篇 |
2023年 | 5384篇 |
2022年 | 9557篇 |
2021年 | 13469篇 |
2020年 | 10101篇 |
2019年 | 8386篇 |
2018年 | 9448篇 |
2017年 | 10816篇 |
2016年 | 9327篇 |
2015年 | 13122篇 |
2014年 | 16130篇 |
2013年 | 19057篇 |
2012年 | 20692篇 |
2011年 | 22339篇 |
2010年 | 19209篇 |
2009年 | 17982篇 |
2008年 | 17457篇 |
2007年 | 16810篇 |
2006年 | 17297篇 |
2005年 | 15210篇 |
2004年 | 9793篇 |
2003年 | 8489篇 |
2002年 | 7884篇 |
2001年 | 6971篇 |
2000年 | 7442篇 |
1999年 | 8720篇 |
1998年 | 7036篇 |
1997年 | 5998篇 |
1996年 | 5593篇 |
1995年 | 4632篇 |
1994年 | 3864篇 |
1993年 | 2706篇 |
1992年 | 2202篇 |
1991年 | 1640篇 |
1990年 | 1208篇 |
1989年 | 977篇 |
1988年 | 786篇 |
1987年 | 538篇 |
1986年 | 412篇 |
1985年 | 278篇 |
1984年 | 191篇 |
1983年 | 133篇 |
1982年 | 140篇 |
1981年 | 98篇 |
1980年 | 81篇 |
1979年 | 34篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1973年 | 5篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
有机-无机压电材料是一种分子铁电体,具有柔性、结构灵活、易成膜、全液相合成及环保节能等优点,可满足新一代薄膜器件及可穿戴设备的需求。该文以三甲基卤代甲基铵(TMXM, X=F, Cl, Br)为有机部分,MnCl2为无机部分,通过溶液蒸发法制备了具有钙钛矿分子结构的有机-无机压电材料三甲基氯三氯化锰(TMCM-MnCl3),并对其分子结构组成、压电、热学、声学及铁电性进行表征。结果表明,TMCM-MnCl3的压电常数为106 pC/N,居里温度为130 ℃,声阻抗值约为16.5 MRayl,低于压电陶瓷PZT-4(大于33 MRayl),具有广阔的应用前景。 相似文献
13.
Zhang Nan Zhao Man Liu Guangfa Wang Jiaoyang Chen Yunzhi Zhang Zhengjian 《Journal of Materials Science》2022,57(19):8687-8700
Journal of Materials Science - A green modification method for effectively enhancing toughness of PLA was established. Herein, alkaline lignin (LG) was firstly alkylated with dodecane, and then... 相似文献
14.
Wang Chen Bao Chun-Hui Wu Wan-Yu Hsu Chia-Hsun Zhao Ming-Jie Zhang Xiao-Ying Lien Shui-Yang Zhu Wen-Zhang 《Journal of Materials Science》2022,57(26):12341-12355
Journal of Materials Science - Molybdenum oxide (MoOx) films had been grown by using plasma-enhanced atomic layer deposition (PEALD) with Mo(CO)6 precursor and O2 plasma reactant in a substrate... 相似文献
16.
Kai Liu Chenyang Zhou Jiaming Hu Song Zhang Qingqing Zhang Ce Sun Yusheng Shi Huajun Sun Changxia Yin Yuzhen Zhang Yu Fu 《Journal of the European Ceramic Society》2021,41(12):5909-5917
A digital light processing (DLP) technology has been developed for 3D printing lead-free barium titanate (BTO) piezoelectric ceramics. By comparing the curing and rheological properties of slurries with different photosensitive monomer, a high refractive index monomer acryloyl morpholine (ACMO) was chosen, and a design and preparation method of BTO slurry with high solid content, low viscosity and high curing ability was proposed. By further selecting the printing parameters, the single-layer exposure time was reduced and the forming efficiency has been greatly improved. Sintered specimens were obtained after a nitrogen-air double-step debinding and furnace sintering process, and the BTO ceramics fabricated with 80 wt% slurry shows the highest relative density (95.32 %) and piezoelectric constant (168.1 pC/N). Furthermore, complex-structured BTO ceramics were prepared, impregnated by epoxy resin and finally assembly made into hydrophones, which has significance for the future design and manufacture of piezoelectric ceramic-based composites that used in functional devices. 相似文献
17.
Pengfei Chen Honggang Chang Tao Peng Yongfan Tang Youquan Liu Chao Xiang 《应用聚合物科学杂志》2021,138(30):50314
Hydraulic fracturing with slickwater is a field-proven stimulation technology used in tight reservoirs. Because of the high pumping rate associated with slickwater fracturing, drag reduction (DR) is critical in minimizing pressure drop and the success of oilfield operations. In this paper, a new type of drag reducer (SPR) was synthesized with acrylamide and 12-allyloxydodecyl acid sodium, and its drag reduction performance was evaluated. The results showed that the new drag reducer features low molecular weight, fast-dissolving rate and low interfacial tension. The algorithm of estimating the drag reduction rate of non-Newtonian fluid SPR was proposed and validated. Empirical or semianalytical models for estimating the friction ratio (σ) or friction factor (λ or f) were used to simulate the turbulence behavior of the SPR drag reducer under different Reynolds numbers (Re). The modified Virk's correlation could accurately model the turbulent behavior of the SPR drag reducer. A unified calculation formula was established in this study for different pipe diameters. 相似文献
18.
盾构隧道施工物料无人运输有助于提升运输效率、降低运输成本、减少运输安全事故率。与公路汽车无人驾驶、港口车辆无人驾驶、轨道交通无人驾驶等逐步成熟的无人驾驶技术不同,在隧道场景下实施施工物料无人运输存在运输物料种类繁多、运输调度困难、地下定位信号拒止、狭窄车道频繁会车、行车路面工况复杂、地上地下联动响应慢等诸多挑战。从实现盾构隧道施工物料无人运输的关键问题分析入手,综述当前盾构隧道施工物料运输方式、运输需求、无人运输发展现状及存在的挑战,提出盾构隧道施工物料无人运输的五大关键技术:多种类物料智能货控能效管理技术,无人化垂直装卸门机控制技术,多传感器融合同步定位与地图构建技术,隧道复杂环境路径规划与自主避障技术,隧-地一体化联动响应的高可靠性无线通信技术。 相似文献
19.
Jiao Zhang Junjie Li Ayesha Murtaza Aamir Iqbal Lijuan Zhu Shinawar Waseem Ali Muhammad Usman Roshan Yameen Siyi Pan Wanfeng Hu 《International Journal of Food Science & Technology》2022,57(2):963-973
This work evaluated the synergistic effects of combined high-intensity ultrasound (HIU) with β-cyclodextrin (β-CD) treatments on inhibiting browning of apple juice and explored the mechanism through simulation system. The combined treatment of 300 W HIU with 0.006 g mL−1 β-CD had a synergistic impact on maintaining juice colour, resulting in a 39.06% reduction in browning degree, only a 36.64% decrease in total phenolic content, and a 17.82% reduction in PPO activity. The inhibition of enzymatic browning in simulated system revealed that HIU suppressed the enzyme (Polyphenol oxidase, PPO) and β-CD inhibited enzyme (PPO) and embedded substrate (polyphenol). The results of spectroscopic analysis showed that the particle-size distribution of PPO narrowed, the content of α-helix in the secondary structure increased, the fluorescence intensity increased, and the maximum wavelength was red-shifted after HIU and β-CD treatment. Changes in structure could further result in PPO activity loss. Hence, the combined treatment could synthetically alleviate the browning of apple juice. 相似文献
20.
Multidimensional Systems and Signal Processing - Non-local means (NLM) method is a powerful technique in the field of image processing. The center weight CW (the weight of the pixel to be denoised)... 相似文献