全文获取类型
收费全文 | 1377篇 |
免费 | 28篇 |
国内免费 | 22篇 |
专业分类
电工技术 | 15篇 |
综合类 | 33篇 |
化学工业 | 517篇 |
金属工艺 | 124篇 |
机械仪表 | 99篇 |
建筑科学 | 6篇 |
矿业工程 | 41篇 |
能源动力 | 155篇 |
轻工业 | 34篇 |
石油天然气 | 2篇 |
武器工业 | 2篇 |
无线电 | 25篇 |
一般工业技术 | 279篇 |
冶金工业 | 43篇 |
原子能技术 | 42篇 |
自动化技术 | 10篇 |
出版年
2023年 | 12篇 |
2022年 | 28篇 |
2021年 | 39篇 |
2020年 | 32篇 |
2019年 | 33篇 |
2018年 | 25篇 |
2017年 | 28篇 |
2016年 | 36篇 |
2015年 | 26篇 |
2014年 | 51篇 |
2013年 | 70篇 |
2012年 | 53篇 |
2011年 | 106篇 |
2010年 | 71篇 |
2009年 | 71篇 |
2008年 | 76篇 |
2007年 | 84篇 |
2006年 | 101篇 |
2005年 | 78篇 |
2004年 | 61篇 |
2003年 | 61篇 |
2002年 | 66篇 |
2001年 | 27篇 |
2000年 | 34篇 |
1999年 | 27篇 |
1998年 | 29篇 |
1997年 | 15篇 |
1996年 | 21篇 |
1995年 | 9篇 |
1994年 | 14篇 |
1993年 | 6篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有1427条查询结果,搜索用时 984 毫秒
21.
22.
Shielding coatings based on graphite nanosheets were prepared by compounding method. The surface morphology of the graphite nanosheets and conductive coatings was examined by scanning electron microscopy. The surface resistivity of the coatings was greatly declined by incorporating the graphite nanosheets. The electromagnetic interference shielding effectiveness (SE) from 0.3 MHz to 1.5 GHz was also studied, and found that the SE of the coatings was consistent with its conductivity. The best sample was shown to exhibit up to 38 dB of SE at 1.5 GHz (with a thickness of 400 μm). The main shielding mechanism of the system was reflection and multiple reflections. 相似文献
23.
Laurence J. Hardwick Matthias Hahn Michael Holzapfel Hilmi Buqa Petr Novák 《Electrochimica acta》2006,52(2):675-680
An initial Raman study on the effects of intercalation for aprotic electrolyte-based electrochemical double-layer capacitors (EDLCs) is reported. In situ Raman microscopy is employed in the study of the electrochemical intercalation of tetraethylammonium (Et4N+) and tetrafluoroborate (BF4−) into and out of microcrystalline graphite. During cyclic voltammetry experiments, the insertion of Et4N+ into graphite for the negative electrode occurs at an onset potential of +1.0 V versus Li/Li+. For the positive electrode, BF4− was shown to intercalate above +4.3 V versus Li/Li+. The characteristic G-band doublet peak (E2g2(i) (1578 cm−1) and E2g2(b) (1600 cm−1)) showed that various staged compounds were formed in both cases and the return of the single G-band (1578 cm−1) demonstrates that intercalation was fully reversible. The disappearance of the D-band (1329 cm−1) in intercalated graphite is also noted and when the intercalant is removed a more intense D-band reappears, indicating possible lattice damage. For cation intercalation, such irreversible changes of the graphite structure are confirmed by scanning electron microscopy (SEM). 相似文献
24.
Zunli Mo Yinxia Sun Hong Chen Ping Zhang Dandan Zuo Yanzhi Liu Hejun Li 《Polymer》2005,46(26):1046-12676
An easy process for the synthesis of poly(methyl methacrylate)/Ce(OH)3, Pr2O3/graphite nanosheet (PMMA/Ce(OH)3, Pr2O3/NanoG) composite was developed. Graphite nanosheets (NanoG) were prepared by treating the expanded graphite with sonication in aqueous alcohol solution. The PMMA/Ce(OH)3, Pr2O3/NanoG composites were prepared via in situ polymerization of MMA monomer in the presence of graphite nanosheets and Ce(OH)3, Pr2O3 through reverse micelle template, in which the methyl methacrylate was designated as the oily phase. The composites were then dispersed with chloroform and coated on glass slides to form films. Scanning and transmission electron microscopy were used to characterize the structure and dispersion of the graphite nanosheets and the composites. The results showed that the high-aspect-ratio structure of the nanosheets played an important role in forming a conducting network in the PMMA matrix. From thermogravimetric analysis, the introduction of graphite nanosheets and inorganic nanopartices exhibited a beneficial effect on the thermal stability of PMMA. 相似文献
25.
Natural graphite particles with high crystallinity sieved to obtain a particle size range of under 63 μm were ground with a ball mill, under various well-controlled grinding atmospheres such as N2, O2, He, H2, and vacuum. The ratio, Xdif50/Xst50, i.e. between the 50 wt.% Stokes diameter and the 50 wt.% laser diffraction diameter, of the ground particles, was used as an index of the flakiness of the particles. The specific resistance of films composed of the ground graphite particles was systematically measured. The rate of reduction in the size of the particles by grinding was slow under an O2-rich atmosphere such as 100% O2 and dry air. On the other hand, it was relatively fast in vacuum, or under an N2 or He atmosphere, and a gas mixture of 99% N2 and 1% O2. The rate of size reduction by grinding under a H2 atmosphere was intermediate. In our experimental conditions, the flakiness of the ground particles increased with the decrease in the particles’ sizes. The electrical conductivity of the ground particles, however, tended to decrease with the decrease in their sizes. Under the condition that the Stokes diameter of the ground particles remains constant, the electrical conductivity of films made from the ground particles increases with the increase in the flakiness of the particles. It was finally determined from our systematic grinding experiments that small flaky particles, which had a size, Xst of ∼1 μm, with a high electrical conductivity can be produced by grinding in a gas mixture of 99% N2 and 1% O2. In this case, the flaky shape of the ground particles was visually confirmed by scanning electron microscopy. 相似文献
26.
Adsorption properties of graphite oxides hydrophobized by n-hexadecylamine, (C16)xGO, were investigated using pyrene molecules as a model of nonionic organic contaminants. A large quantity of pyrene (28.5 mg/g) was adsorbed from a water-ethanol mixture (1:2) containing 2 mM of pyrene when (C16)0.6GO was used. The isotherm of pyrene adsorption was better described by Freundlich equation rather than Langmuir equation, which indicated a single adsorption mechanism was involved. The change in the amount of adsorbed pyrene as a function of amine content in GO was very similar to that which occurs upon introduction of pyrene into (C16)xGO films from chloroform solution, as determined by X-ray measurements. This suggests that pyrene molecules were adsorbed not only on the outer surface but also within the interlayer space of the intercalation compound. Swelling of the intercalation compound by ethanol can render the interlayers more organophilic and make access to hexadecylamine molecules bonded to the graphite oxide layer easier for pyrene molecules, especially in (C16)xGOs with lower amine contents. 相似文献
27.
随着工业的发展,化石燃料消耗巨大,环境问题也日益突出,寻找一种绿色新型能源已成为一个被广泛讨论的问题。氢气是一种清洁、可再生燃料,利用光催化剂分解水制氢气是一种制取氢气的有效途径。石墨碳氮化物(g-C3N4)作为光催化剂不仅成本低、反应稳定,而且其尺寸、厚度、结构、形貌等可控,在众多光催化剂中脱颖而出。但g-C3N4目前在光催化领域主要存在两个局限:g-C3N4不能有效地吸收光来产生足够多的光生电子-空穴对;g-C3N4不能有效的运输及分离光生电子-空穴对,以至于电子与空穴的复合率较高。文章综述了g-C3N4在光催化制氢领域的进展成果,分析了g-C3N4存在的问题并总结了其改进方法,最后对g-C3N4进行了展望,以期为设计高效、稳定的光催化制氢材料提供参考。 相似文献
28.
Jernej Drofenik Robert Dominko Mogens Mogensen Stane Pejovnik 《Electrochimica acta》2003,48(7):883-889
Four types of cellulose, in particular carboxy methyl cellulose (CMC), are tested as potential binding materials in graphitic anodes for lithium ion batteries. It is shown that a minimum content of a cellulose which gives acceptable anode properties (reversible capacity>300 mA h g−1 during the first 10 cycles, irreversible loss<20%) is about 2 wt.%, which is less than in the case of conventional polymeric binders (5-10 wt.%). Kinetics of insertion-deinsertion and passivation processes seem not to be affected by the presence of cellulose. Explanation for the electrode failure at cellulose contents lower than 1 wt.% is given based on X-ray diffraction and microscopy investigations. Finally, the structure (distribution) of cellulose in the composite anode material is discussed and (indirectly) checked with a series of experiments. Most results are compared with the corresponding results obtained either with gelatin or conventional polymeric binders or both. 相似文献
29.
借助谐响应分析辨识出柔性石墨纸轧机动刚度的薄弱环节,并利用灵敏度分析方法建立该环节的优化数学模型,进而实现对整机动刚度的提升。通过对各部件刚度提升前后的柔性石墨纸轧机进行模态分析,并对比各部件对整机固有频率的影响,辨识出薄弱部位为底座,故以底座为优化对象;将牌坊Y向共振频率对底座尺寸的灵敏度曲线拟合得出优化目标函数,以Y向共振频率为优化目标,质量为约束条件建立优化方程并求解;对比优化前后整机的动刚度,得出:在质量不增加的情况下,整机薄弱频率提升了24.1%,Y向振幅降低了15.9%。为提高优化效率提供了理论依据和参考。 相似文献
30.
石墨颗粒表面化学镀铜研究 总被引:15,自引:2,他引:15
为了充分利用Cu的导电性能,碳石墨的润滑性能,改善Cu/C的润湿性,用化学镀铜的方法成功地对石墨颗粒表面进行镀覆,详细地研究了镀铜液组分及工艺与石墨颗粒表面镀铜层厚度、沉积速率的关系,并得出较好的组分工艺方案,采用优化工艺可以得到平均厚度约7.1μm的镀铜层。同时应用X射线、金相显微镜、扫描电镜及电子探针对镀铜层的厚度、表面形貌、镀铜层与基体的界面进行了全面观察。分析表明,Cu/C界面存在过渡层,界面成锯齿状,机械冶金结合的特征十分明显,改善了铜碳界面的相溶性。 相似文献