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排序方式: 共有804条查询结果,搜索用时 15 毫秒
1.
铝合金由于其密度小、强度高、耐腐蚀等一系列优良性能,已经成为世界上第二大金属材料。随着原铝产量的严重短缺和各种铝产品相继达到报废年限,人们对各类废旧铝合金的回收利用越发关注。再生铝行业的兴起不仅可以有效缓解全球铝土矿资源日益匮乏的局面,而且对经济、环境和能源的可持续发展都有很大贡献。航空航天用铝由于工作环境特殊,对铝合金强度、耐热性、抗腐蚀性和抗疲劳性等有严格的要求,航空铝有更高的循环利用价值。通过几十年的研究探索,针对废铝回收过程产品质量不稳定、烧损率高、氧化严重等问题,相继开发了重介质分离、双室炉熔炼、LARS变质处理等技术和设备。本工作对常见废旧铝合金在预处理、重熔再生和金属熔体精炼过程中所用设备和技术进行了总结,重点归纳了航空铝的回收利用现状,对铝回收行业存在的难点问题和未来发展趋势进行了讨论和展望。 相似文献
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Yu Wang He Zhang Shuqiang Jiao Kuo-Chih Chou Guo-Hua Zhang 《Journal of the American Ceramic Society》2020,103(4):2399-2406
Molybdenum boride is an ideal hard and wear-resistant material. In this study, a new method is proposed for preparing molybdenum boride, by which Mo first reacts with B4C to generate the mixture of molybdenum boride and C, and then the product is decarburized by molten Ca to generate CaC2. Pure molybdenum boride could be obtained after acid leaching to remove the by-product CaC2. According to the experimental and thermodynamic calculation results, it is concluded that the single-phase MoB could be successfully prepared, while Mo2B, Mo2B5, and MoB4 could not be synthesized by this method. Moreover, it was found that the particle size of finally prepared MoB is determined by particle size of raw Mo powder. The residual carbon content of the product could be decreased to 0.10 wt% after first reaction at 1673 K for 6 hours and then decarburization reaction at 1673 K for 6 hours. 相似文献
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《International Journal of Hydrogen Energy》2020,45(21):11923-11942
Hydrogen fuel cells (H2–FCs) are promising devices for pollution-free and efficient power production. Renewable H2 from biomass is often produced through catalytic ethanol steam reforming (ESR), which requires a steam/ethanol molar ratio of at least three. The bioethanol obtained by biomass fermentation contains large amounts of water and can be directly subjected to ESR without complex purification steps. However, a wide spectrum of impurities is present in such bioethanol samples, thus complicating the ESR process. Acetic acid, fusel alcohols, ethyl acetate, and sulfur components have been reported as important bioethanol impurities, and also as the main precursors of carbon deposits on the ESR catalyst. On the other hand, amines, methanol, and aldehydes, which are minor bioethanol impurities, have been reported to enhance the H2 production. This review seeks to define alternatives to reduce the above negative impurities and increase the positive ones during biomass pretreatment and fermentation. Additionally, ESR catalysts are reviewed to identify the features that make them more resistant to deactivation. The combination of strategies to control the impurities during biomass pretreatment, fermentation, purification and the development of highly resistant catalysts may allow processes to produce H2 from biomass with a low carbon footprint, rendering H2–FCs an environmentally friendly technology for power production. 相似文献
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Antonio Bonati Gabriele Pisano Gianni Royer Carfagni 《Journal of the American Ceramic Society》2019,102(5):2506-2521
Nickel Sulfide (NiS) inclusions can provoke the rupture of thermally treated glass due to a phase transformation with volume increase that stresses the surrounding glass. Starting from a Pareto statistics for the population of inclusion sizes, from an assumed kinetics of the phase transformation, a micro-mechanically motivated model provides the statistical characterization of the probability of spontaneous failure of glass during lifetime. A distinction based upon the composition of NiS is used to discuss the effects of the heat soak test (HST), where glass remains at high temperature for a certain time to speed-up the phase transformation and destroy those elements with critical inclusions. Three functions à la Weibull for the probability of spontaneous rupture during lifetime are theoretically derived for the case of no HST, short HST, and long HST. In particular, the probability of collapse for long HSTs depends upon the holding time in the oven. An explanatory example shows the potentiality of the model for optimizing the HST parameters toward a target probability of failure, but experimental campaigns are needed for a proper calibration. 相似文献
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Polymeric membrane-based gas separation has found wide applications in industry, such as carbon capture, hydrogen recovery, natural gas sweetening, as well as oxygen enrichment. Commercial gas separation membranes are required to have high gas permeability and selectivity, while being cost-effective to process. Mixed matrix membranes (MMMs) have a composite structure that consists of polymers and fillers, therefore featuring the advantages of both materials. Much effort has been made to improve the gas separation performance of MMMs as well as general membrane properties, such as mechanical strength and thermal stability. This perspective describes potential use of MMMs for carbon capture applications, explores their limitations in fabrication and methods to overcome them, and addresses their performance under industry gas conditions. 相似文献
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采用硫酸化焙烧-浸出-电积工艺来处理硫化铜精矿时增加预浸出可以使得铜浸出率增加,焙砂浸出液中影响铜电积的主要杂质元素Fe、Mn、Co等含量降低,预浸出段酸矿比0.3:1、温度50 ℃、时间3 h、液固比1:1时,Cu的最终浸出率大于99%,焙砂浸出液中Fe、Mn含量分别为0.12g/L和0.005g/L。通过预浸出段正交试验,确定了酸矿比对各个元素的浸出率影响最大,当酸矿比0.6:1,温度70 ℃,时间2 h,液固比1:1时,Fe的渣计浸出率为93.61%,Mn的渣计浸出率为59.50%,Mg的渣计浸出率为32.97%。 相似文献
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Yuhui ZHANG 《等离子体科学和技术》2019,21(7):74003-33
In this paper, a two-dimensional axisymmetric fluid model was established to investigate the influence of nitrogen impurity content on the discharge pattern and the relevant discharge characteristics in an atmosphere pressure helium dielectric barrier discharge (DBD). The results indicated that when the nitrogen content was increased from 1 to 100 ppm, the discharge pattern evolved from a concentric-ring pattern into a uniform pattern, and then returned to the concentricring pattern. In this process, the discharge mode at the current peak moment transformed from glow mode into Townsend mode, and then returned to glow mode. Further analyses revealed that with the increase of impurity level, the rate of Penning ionization at the pre-ionization stage increased at first and decreased afterwards, resulting in a similar evolution pattern of seed electron level. This evolution trend was believed to be resulted from the competition between the N2 partial pressure and the consumption rate of metastable species. Moreover, the discharge uniformity was found positively correlated with the spatial uniformity of seed electron density as well as the seed electron level. The reason for this correlation was explained by the reduction of radial electric field strength and the promotion of seed electron uniformity as pre-ionization level increases. The results obtained in this work may help better understand the pattern formation mechanism of atmospheric helium DBD under the variation of N2 impurity level, thereby providing a possible means of regulating the discharge performance in practical application scenarios. 相似文献