全文获取类型
收费全文 | 64108篇 |
免费 | 9213篇 |
国内免费 | 4250篇 |
专业分类
电工技术 | 11589篇 |
技术理论 | 1篇 |
综合类 | 5694篇 |
化学工业 | 10482篇 |
金属工艺 | 5194篇 |
机械仪表 | 5049篇 |
建筑科学 | 5964篇 |
矿业工程 | 2674篇 |
能源动力 | 1716篇 |
轻工业 | 1948篇 |
水利工程 | 1019篇 |
石油天然气 | 3187篇 |
武器工业 | 1080篇 |
无线电 | 3058篇 |
一般工业技术 | 10254篇 |
冶金工业 | 1743篇 |
原子能技术 | 219篇 |
自动化技术 | 6700篇 |
出版年
2024年 | 252篇 |
2023年 | 1053篇 |
2022年 | 1948篇 |
2021年 | 2393篇 |
2020年 | 2595篇 |
2019年 | 2034篇 |
2018年 | 1907篇 |
2017年 | 2461篇 |
2016年 | 2647篇 |
2015年 | 2786篇 |
2014年 | 3956篇 |
2013年 | 3575篇 |
2012年 | 4928篇 |
2011年 | 4971篇 |
2010年 | 3816篇 |
2009年 | 4098篇 |
2008年 | 3525篇 |
2007年 | 4597篇 |
2006年 | 4178篇 |
2005年 | 3449篇 |
2004年 | 2831篇 |
2003年 | 2555篇 |
2002年 | 2050篇 |
2001年 | 1876篇 |
2000年 | 1506篇 |
1999年 | 1209篇 |
1998年 | 886篇 |
1997年 | 726篇 |
1996年 | 638篇 |
1995年 | 558篇 |
1994年 | 406篇 |
1993年 | 348篇 |
1992年 | 239篇 |
1991年 | 190篇 |
1990年 | 118篇 |
1989年 | 68篇 |
1988年 | 56篇 |
1987年 | 34篇 |
1986年 | 8篇 |
1985年 | 14篇 |
1984年 | 15篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 3篇 |
1980年 | 21篇 |
1979年 | 11篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
31.
《Ceramics International》2022,48(14):20237-20244
Composite anode materials with a unique architecture of carbon nanotubes (CNTs)-chained spinel lithium titanate (Li4Ti5O12, LTO) nanoparticles are prepared for lithium ion capacitors (LICs). The CNTs networks derived from commercial conductive slurry not only bring out a steric hindrance effect to restrict the growth of Li4Ti5O12 particles but greatly enhance the electronic conductivity of the CNTs/LTO composites, both have contributed to the excellent rate capability and cycle stability. The capacity retention at 30 C (1 C = 175 mA g?1) is as high as 89.7% of that at 0.2 C with a CNTs content of 11 wt%. Meanwhile, there is not any capacity degradation after 500 cycles at 5 C. The LIC assembled with activated carbon (AC) cathode and such a CNTs/LTO composite anode displays excellent energy storage properties, including a high energy density of 35 Wh kg?1 at 7434 W kg?1, and a high capacity retention of 87.8% after 2200 cycles at 1 A g?1. These electrochemical performances outperform the reported data achieved on other LTO anode-based LICs. Considering the facile and scalable preparation process proposed herein, the CNTs/LTO composites can be very potential anode materials for hybrid capacitors towards high power-energy outputs. 相似文献
32.
One of the major challenges in wireless body area networks (WBANs) is sensor fault detection. This paper reports a method for the precise identification of faulty sensors, which should help users identify true medical conditions and reduce the rate of false alarms, thereby improving the quality of services offered by WBANs. The proposed sensor fault detection (SFD) algorithm is based on Pearson correlation coefficients and simple statistical methods. The proposed method identifies strongly correlated parameters using Pearson correlation coefficients, and the proposed SFD algorithm detects faulty sensors. We validated the proposed SFD algorithm using two datasets from the Multiparameter Intelligent Monitoring in Intensive Care database and compared the results to those of existing methods. The time complexity of the proposed algorithm was also compared to that of existing methods. The proposed algorithm achieved high detection rates and low false alarm rates with accuracies of 97.23% and 93.99% for Dataset 1 and Dataset 2, respectively. 相似文献
33.
Baofu Qiu Xiaoming Duan Zhuo Zhang Delong Cai Ning Liao Peigang He Dechang Jia Yu Zhou 《Ceramics International》2021,47(1):73-79
The effects of La2O3–Al2O3–SiO2 addition on the thermal conductivity, coefficient of thermal expansion (CTE), Young's modulus and cyclic thermal shock resistance of hot-pressed h-BN composite ceramics were investigated. The samples were heated to 1000 °C and then quenched to room temperature with 1–50 cycles, and the residual flexural strength was used to evaluate cyclic thermal shock resistance. h-BN composite ceramics containing 10 vol% La2O3–Al2O3 and 20 vol% SiO2 addition exhibited the highest flexural strength, thermal conductivity and relatively low CTE, which were beneficial to the excellent thermal shock resistance. In addition, the viscous amorphous phase of ternary La2O3–Al2O3–SiO2 system could accommodate and relax thermal stress contributing to the high thermal shock resistance. Therefore, the residual flexural strength still maintained the value of 234.3 MPa (86.9% of initial strength) after 50 cycles of thermal shock. 相似文献
34.
Ceramic matrix composites (CMC) are highly required in many fields of science and engineering. However, the CMC parts always have poor surface finish. This study attempts to improve cutting performance of CMC material by combing the advantages of ultrasonic assisted cutting and diamond wire sawing. Cutting force, surface roughness, machined edge and tool wear are analyzed based on experimental results. It shows that the oscillatory movement of tool edges provides positive effect on particle ejection and residual material reduction. Ductile chip formation can be achieved due to the small tip radius of grits. Obvious decrease in cutting force, surface roughness and tool wear are obtained. Moreover, burrs, fuzzing and fracture are reduced. Meanwhile, both the surface characteristics and shape accuracy are significantly improved. These results provide a valuable basis for application of ultrasonic assisted wire sawing and understanding of CMC cutting mechanisms. 相似文献
35.
Leo H. Chiang Birgit Braun Zhenyu Wang Ivan Castillo 《American Institute of Chemical Engineers》2022,68(6):e17644
In the Industry 4.0 era, the chemical industry is embracing broad adoption of artificial intelligence (AI) and machine learning (ML) methods. This article provides a holistic view of how the industry is transforming digitally towards AI at scale. First, a historical perspective on how the industry used AI to aid humans in better decision-making is shown. Then state-of-the-art AI research addressing industrial needs on reliability and safety, process optimization, supply chain, material discovery, and reaction engineering is highlighted. Finally, a vision of the plant of the future is illustrated with critical components of AI-ready culture, model life cycle management, and renewed role of humans in chemical manufacturing. 相似文献
36.
37.
38.
The present study proposes an algorithm for fault detection in terms of condition‐based maintenance with data mining techniques. The proposed algorithm is applied on an aircraft turbofan engine using flight data and consists of two main sections. In the first section, the relationship between engine exhaust gas temperature (EGT) as the main engine health monitoring criterion and other operational and environmental parameters of the engine was modelled using the data‐driven models. In the second section, a data set including EGT residuals, that is, the difference between the actual EGT of the system and the EGT estimated by the developed model in the health conditions of the engine, was created. Finally, faults occurring in each flight were detected based on the identification of abnormal events by a one‐class support vector machine trained by the health condition EGT residual data set. The results indicated that the proposed algorithm was an effective approach for inspecting aircraft engine conditions and detecting faults, with no need for technical knowledge on the interior characteristics of the aircraft engine. 相似文献
39.
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
40.
Yong Zhang Zi-Ran Liu Ding-Wang Yuan Qin Shao Jiang-Hua Chen Cui-Lan Wu Zao-Li Zhang 《金属学报(英文版)》2019,32(9):1099-1110
Owing to the excellent elastic properties and chemical stability, binary metal or light element borides, carbides and nitrides have been extensively applied as hard and low-compressible materials. Researchers are searching for harder materials all the time. Recently, the successful fabrication of nano-twinned cubic BN(Tian et al. Nature 493:385–388, 2013) and diamond(Huang et al. Nature 510:250–253, 2014) exhibiting superior properties than their twin-free counterparts allows an efficient way to be harder. From this point of view, the borides, carbides and nitrides may be stronger by introducing twins, whose formation tendency can be measured using stacking fault energies(SFEs). The lower the SFEs, the easier the formation of twins. In the present study, by means of first-principles calculations, we first calculated the fundamental elastic constants of forty-two borides, seventeen carbides and thirty-one nitrides, and their moduli, elastic anisotropy factors and bonding characters were accordingly derived. Then, the SFEs of the {111} 112 glide system of twenty-seven compounds with the space group F43 m or Fm3m were calculated. Based on the obtained elastic properties and SFEs, we find that(1) light element compounds usually exhibit superior elastic properties over the metal borides, carbides or nitrides;(2) the 5 d transitionmetal compounds(ReB_2, WB, OsC, RuC, WC, OsN_2, TaN and WN) possess comparable bulk modulus( B) with that of cBN( B = 363 GPa);(3) twins may form in ZrB, HfN, PtN, VN and ZrN, since their SFEs are lower or slightly higher than that of diamond(SFE = 277 mJ/m~2). Our work can be used as a valuable database to compare these compounds. 相似文献