全文获取类型
收费全文 | 1466篇 |
免费 | 74篇 |
国内免费 | 109篇 |
专业分类
电工技术 | 11篇 |
综合类 | 74篇 |
化学工业 | 271篇 |
金属工艺 | 140篇 |
机械仪表 | 30篇 |
建筑科学 | 17篇 |
矿业工程 | 16篇 |
能源动力 | 137篇 |
轻工业 | 222篇 |
水利工程 | 6篇 |
石油天然气 | 8篇 |
武器工业 | 3篇 |
无线电 | 57篇 |
一般工业技术 | 201篇 |
冶金工业 | 51篇 |
原子能技术 | 7篇 |
自动化技术 | 398篇 |
出版年
2024年 | 6篇 |
2023年 | 102篇 |
2022年 | 51篇 |
2021年 | 70篇 |
2020年 | 88篇 |
2019年 | 101篇 |
2018年 | 44篇 |
2017年 | 77篇 |
2016年 | 66篇 |
2015年 | 56篇 |
2014年 | 104篇 |
2013年 | 92篇 |
2012年 | 95篇 |
2011年 | 84篇 |
2010年 | 75篇 |
2009年 | 86篇 |
2008年 | 58篇 |
2007年 | 100篇 |
2006年 | 88篇 |
2005年 | 27篇 |
2004年 | 21篇 |
2003年 | 18篇 |
2002年 | 15篇 |
2001年 | 16篇 |
2000年 | 7篇 |
1999年 | 16篇 |
1998年 | 13篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 15篇 |
1986年 | 8篇 |
1985年 | 1篇 |
1984年 | 7篇 |
1983年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有1649条查询结果,搜索用时 0 毫秒
61.
分子筛由于具有规则的孔道结构、适宜的酸性、良好的热和水热稳定性等特点,广泛应用于吸附、分离、离子交换及催化等领域。传统水热法制备分子筛因需要使用大量溶剂和有机模板剂,存在合成效率低、生产成本高、污染环境等一系列问题。近年来,随着"绿色化学"理念的深入人心,开发绿色、可持续的分子筛制备路线备受关注,逐渐成为该领域的研究热点。本文主要从水热法、离子热法、干胶法以及无溶剂法等几个方面,对国内外分子筛绿色合成的最新研究进展进行综述,并归纳比较上述合成方法的优缺点。最后,提出目前绿色合成分子筛过程中存在的问题,展望其未来发展前景。 相似文献
62.
《Ceramics International》2020,46(4):4595-4601
The effects of the vacancies on the structural stability, elastic constants, elastic moduli, brittle-to-ductile transition and electronic properties of Tantalum Silicide (TaSi2) are investigated in detail by first-principles calculations. The values of vacancy formation energy confirm that the perfect TaSi2 and TaSi2 with different atomic vacancies can exhibit the structural stability at ground state. It is found that Ta atom vacancies are more stable than Si atom vacancies in TaSi2 with vacancies. The elastic constants and elastic moduli describe the mechanical behavior for TaSi2 and TaSi2 with vacancies. The different atomic vacancies weaken the elastic stiffness for TaSi2. But the values of B/G confirm that the brittle-to-ductile transition occurs with different atomic vacancies for TaSi2. Although these vacancies make the shear and volume deformation resistance of TaSi2 weaker, they obviously improve the brittle behavior of TaSi2. The difference charge density and electronic structures are calculated to discuss and analyze the structural stability and mechanical properties for the perfect TaSi2 and TaSi2 with vacancies. 相似文献
63.
《Ceramics International》2020,46(13):20788-20797
In this work, BiVO4 composites, containing the tetragonal zircon phase (tz-BiVO4), and monoclinic scheelite phase (ms-BiVO4), were synthesized using the microemulsion method. The effect of pH on phase composition and photocatalytic activity were investigated. Based on X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), a ms/tz-BiVO4 composite forms at pH = 1.0 and pure ms-BiVO4 is obtained in the pH range 4.0–10.0. The three primary steps in preparing BiVO4 were monitored by optical microscopy and the role played by the microemulsion on the phase composition of BiVO4 is explained. Photoluminescence spectroscopy (PL), UV–visible diffuse reflectance spectroscopy (UV-DRS), Brunauer-Emmett-Teller (BET), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were employed to characterize the physical and chemical properties of BiVO4 composites. The composite formed at pH = 1 exhibited the lowest hole-electron (h+-e-) recombination rate, resulting in the highest photocatalytic activity towards microcystin-LR (MC-LR), with near 100% removal of MC-LR in 5 h. ESR and trapping experiments indicated that MC-LR degradation was mediated primarily by hydroxyl radicals (•OH), superoxide radicals (O2•−) and photogenerated holes (h+). 相似文献
64.
基于无线传感器网络SPIN协议的一种改进方案 总被引:1,自引:0,他引:1
针对无线传感器网络的路由协议SPIN-1存在的问题提出了改进方案(SPIN-G),并对SPIN-G协议和SPIN-1协议在节点的能量消耗、数据投递率和传输延时方面进行了仿真,仿真结果表明,SPIN-G协议不仅解决了SPIN-1协议存在的数据盲点问题,而且还平衡了节点的能量消耗,延长了网络的生命周期. 相似文献
65.
《Materials Research Bulletin》1987,22(6):813-817
The luminescence of MgWO4.2H2O contains two emission bands, one due to the tungstate tetrahedron, and another one related to the hydrate group. The former is compared with the tungstate luminescence of anhydrous MGWO4. 相似文献
66.
67.
68.
《Ceramics International》2017,43(11):8183-8189
Hierarchical WO3 dendrites were synthesized via low-cost and environmental-friendly solvothermal strategy. Characterization results indicated that WO3 dendrites were composed of several multi-directional dendritic nanosheets. To further understand the formation of WO3 dendrites, time-dependent experiments were carried out and formation mechanism was investigated. Since such dendritic structures rarely occurred in the field of gas sensing, the synthesized WO3 dendrites were subjected to detailed NO2 sensing tests. Results demonstrated that WO3 dendrites based sensors had low detection limit (200 ppb) and fast response and recovery (7 s, 12 s to 5 ppm NO2). Moreover, the sensor was also highly sensitive, selective and stable at low optimal operating temperature of 140 °C. 相似文献
69.
With the gradual rise of enzyme engineering, it has played an essential role in synthetic biology, medicine, and biomanufacturing. However, due to the limitation of the cell membrane, the complexity of cellular metabolism, the difficulty of controlling the reaction environment, and the toxicity of some metabolic products in traditional in vivo enzyme engineering, it is usually problematic to express functional enzymes and produce a high yield of synthesized compounds. Recently, cell-free synthetic biology methods for enzyme engineering have been proposed as alternative strategies. This cell-free method has no limitation of the cell membrane and no need to maintain cell viability, and each biosynthetic pathway is highly flexible. This property makes cell-free approaches suitable for the production of valuable products such as functional enzymes and chemicals that are difficult to synthesize. This article aims to discuss the latest advances in cell-free enzyme engineering, assess the trend of this developing topical filed, and analyze its prospects. 相似文献
70.
《International Journal of Hydrogen Energy》2020,45(7):4390-4402
TiO2–CdS nanotubes (NTs) were used for the first time as a support to load metal nanoparticles (NPs) for the hydrolysis of ammonia borane (AB) which is a new strategy. The TiO2–CdS NTs support was first synthesized using a hydrothermal method, and then the CuNi NPs were loaded using a liquid-phase reduction method. The synthesized samples were characterized by XRD, SEM-EDS, TEM, XPS, ICP, UV–Vis, and PL analyses. The characterization results show that the CuNi NPs existed in the form of an alloy with a size of ~1.2 nm and uniformly dispersed on the support. Compared with their single metal counterparts, the bimetallic CuNi-supported catalysts showed a higher catalytic activity in the hydrolysis of AB under visible-light irradiation: Cu0·45Ni0·55/TiO2–CdS catalyst had the fastest hydrogen evolution rate with a high conversion frequency (TOF) of 25.9 molH2·molcat−1 min−1 at 25 °C and low activation energy of 32.8 kJ mol−1. Cu0.45Ni0.55/TiO2–CdS catalyst showed good recycle performance, maintaining 99.3% and 85.6% of the original hydrogen evolution rate even after five and ten recycles, respectively. Strong absorption of visible light, improved electron–hole separation efficiency, and metal synergy between Cu and Ni elements played a crucial role in improving the catalytic hydrolysis performance of AB. The catalyst prepared in this study provides a new strategy for the application of photocatalysts. 相似文献