全文获取类型
收费全文 | 1780篇 |
免费 | 197篇 |
国内免费 | 115篇 |
专业分类
电工技术 | 44篇 |
综合类 | 67篇 |
化学工业 | 464篇 |
金属工艺 | 120篇 |
机械仪表 | 110篇 |
建筑科学 | 39篇 |
矿业工程 | 13篇 |
能源动力 | 137篇 |
轻工业 | 132篇 |
水利工程 | 14篇 |
石油天然气 | 7篇 |
武器工业 | 1篇 |
无线电 | 222篇 |
一般工业技术 | 231篇 |
冶金工业 | 41篇 |
原子能技术 | 13篇 |
自动化技术 | 437篇 |
出版年
2024年 | 9篇 |
2023年 | 144篇 |
2022年 | 134篇 |
2021年 | 145篇 |
2020年 | 132篇 |
2019年 | 83篇 |
2018年 | 51篇 |
2017年 | 90篇 |
2016年 | 67篇 |
2015年 | 61篇 |
2014年 | 144篇 |
2013年 | 143篇 |
2012年 | 203篇 |
2011年 | 172篇 |
2010年 | 109篇 |
2009年 | 95篇 |
2008年 | 36篇 |
2007年 | 50篇 |
2006年 | 38篇 |
2005年 | 11篇 |
2004年 | 13篇 |
2003年 | 19篇 |
2002年 | 16篇 |
2001年 | 18篇 |
2000年 | 11篇 |
1999年 | 11篇 |
1998年 | 9篇 |
1997年 | 1篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 14篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1979年 | 4篇 |
1976年 | 1篇 |
排序方式: 共有2092条查询结果,搜索用时 11 毫秒
101.
《Artificial Intelligence in Engineering》1989,4(3):106-114
The O[M] formalism for Order-of-Magnitude reasoning is described. O[M] is based on seven primitive relations among absolute magnitudes of quantities: ‘much less than’ (< <), ‘moderately less than’ (− <), ‘slightly less than’ (∼ <), ‘equal to’ (= =), ‘slightly greater than’ (> ∼), ‘moderately greater than’ (> −), and ‘much greater than’ (> >). 21 compound relations are formed as implicit disjunctions of consecutive primitive relations. A strict interpretation of the relations allows exact conservative inferences, while a heuristic interpretation allows more aggressive and human-like inferences, by permitting some slack at each inference step. Inference strategies are based on propagation of order-of-magnitude relations through properties of the relations, algebraic constraints, and rules. O[M] operates mainly in the data-driven direction with assumption-based truth-maintenance for the resolution of contradictions. O[M] provides efficient integration of quantitative and qualitative knowledge in the expression and solution of engineering problems. The system has been applied in process engineering and biochemical engineering. 相似文献
102.
103.
聚丙烯亚胺(PPI)树状物由于其独特的化学结构,已经在合成化学、材料科学及生物医学等诸多领域受到广泛关注。采用漆原Co催化剂合成了2.0代聚丙烯基亚胺(PPI)树状物,使用N-羟基琥珀酰亚胺活化的单甲氧基聚乙二醇(mPEG)并对其进行了聚乙二醇(PEG)改性,采用红外光谱和核磁共振表征了中间产物和目标产物的结构。结果表明:所得的中间产物和目标产物均符合分子设计要求,合成路线合理可行。 相似文献
104.
实际公交路网通常为复杂的非线性时变系统,难以有效构建线路间的时空间依赖关系.因此,文中提出基于注意力机制和分时图卷积的公交客流预测模型,提升公交客流量预测的准确性.首先通过长短期记忆网络提取历史数据中的时间特征,并利用通道注意力模块加权特征.再使用分时图卷积方法分析不同时段下公交线路间的空间依赖性,根据预测时段选择不同... 相似文献
105.
非对称用户数字线路的性能受多个因素影响,故障复杂.本文在简要介绍宽带测试方案的基础上,介绍了一种基于统计决策法的方案.用这样的方案改进原有的测试方案,可以使系统具有更优的精度. 相似文献
106.
107.
《Ceramics International》2020,46(6):7531-7540
The modified 0.7Ba (Co1/3Nb2/3)O3-0.3Ba(Zn1/3Nb2/3)O3 (BCZN) powders filled PTFE composites were synthesized by hot-pressing. The influences of BCZN content on the microstructure, dielectric, thermal, mechanical properties and moisture absorption were investigated systematically. The modified BCZN powders filled PTFE composites exhibited better microstructure and dielectric properties compared with untreated powders. Various mathematic models were utilized to predict the dielectric constant of different composites and the effective medium theory (EMT) showed perfect consistency with the experimental results. The modified BCZN/PTFE composites possess the best comprehensive properties at the powders content of 50 vol% with high dielectric constant (εr) of 7.7, low loss (tanδ) of 0.0014, acceptable temperature coefficient of dielectric constant (τε) of −125.6 ppm/°C and temperature coefficient of resonant frequency (τf) of 29.4 ppm/°C at 7 GHz, low moisture absorption of 0.07% and low coefficient of thermal expansion (CTE) of 33 ppm/°C. All the results show modified BCZN/PTFE composites are the potential materials for microwave substrate applications. 相似文献
108.
《Ceramics International》2020,46(11):18690-18697
Bi0.9Er0.1Fe1−xMnxO3 (BEFMxO, x = 0.00–0.03) films are synthesized by a sol–gel technique. The BEFO film exhibits a conduction mechanism based on electron tunneling. The high applied electric field causes dissociation of the defect complex, and the resulting oxygen vacancies contribute to fake polarization. Consequently, the BEFO film has poor polarization stability at high applied electric fields. Coexistence of two phases (with space groups R3c:H and R3m:R) and reduced concentrations of oxygen vacancies and Fe2+ in BEFMxO are achieved by co-doping with Er and Mn. The presence of bulk-based conduction in the BEFMxO films then leads to ferroelectric domain switching contributing to the real polarization and to excellent ferroelectric stability. In addition, the BEFM0.02O film shows a typical symmetrical butterfly curve, the highest remnant polarization of ~109 μC/cm2, and the highest switching current of ~1.66 mA. It also has the smallest oxygen vacancy concentration and thus the smallest amount of defect complex, which means that there are fewer pinning effects on ferroelectric domains and therefore excellent ferroelectric stability. This excellent ferroelectric stability makes the BEFMxO films obtain good stability and reliability in the application of ferroelectric memory devices. 相似文献
109.
《Ceramics International》2020,46(17):26454-26465
Aluminum-ion batteries (AIBs) are considered as alternatives to lithium-ion batteries (LIBs) due to their low cost, good safety and high capacity. Based on aqueous and non-aqueous AIBs, this review focuses on the research progress of the latter cathode materials. Firstly, we fully explain the aluminum storage mechanism of different types of materials. Next, according to relative statistical data, the research trend of different cathode materials (transition metal chalcogenides, transition metal oxides and carbon-based materials) in non-aqueous AIBs is summarized, and related electrochemical performance are analyzed and compared in detail. In addition, as for the research of non-aqueous AIBs cathode materials, the existing problems and expected solutions are discussed, as well as the proposed future research directions. 相似文献
110.
《Ceramics International》2020,46(4):4344-4350
Indium-free flexible transparent conductive thin films (TCFs) composed of silver nanowire (AgNW) networks and Sb doped SnO2 (ATO) layers were prepared on polyethylene terephthalate (PET) substrates. The ATO layers were deposited via radio frequency (RF) magnetron sputtering at room temperature. The AgNWs were achieved via a modified polyol reduction method and embedded between the ATO layers. The effects of AgNW networks and ATO layers on electrical and optical properties of the ATO/AgNWs/ATO flexible tri-layer thin films are investigated. The ATO layers can improve the optical transmittance and reduce the resistivity of tri-layers, and the corresponding mechanisms are proposed. Typically, an ATO/AgNWs/ATO flexible tri-layers show a high figure of merit value (30.06 × 10-3 Ω-1) with a low sheet resistance of 7.1 Ω/sq. and a high transmittance of 85.7%. Meanwhile, the tri-layers present excellent mechanical flexibility, and the ATO layers acted as the protecting layers improve the adhesive and environmental stability at high temperature and humidity for the ATO/AgNWs/ATO flexible tri-layers. These results indicate that ATO/AgNWs/ATO flexible tri-layer thin films can be useful for the fabrication of wearable electronic devices. 相似文献