全文获取类型
收费全文 | 46576篇 |
免费 | 2758篇 |
国内免费 | 1301篇 |
专业分类
电工技术 | 1490篇 |
技术理论 | 4篇 |
综合类 | 2848篇 |
化学工业 | 11628篇 |
金属工艺 | 6490篇 |
机械仪表 | 1208篇 |
建筑科学 | 6449篇 |
矿业工程 | 1576篇 |
能源动力 | 1014篇 |
轻工业 | 4334篇 |
水利工程 | 1795篇 |
石油天然气 | 1699篇 |
武器工业 | 153篇 |
无线电 | 876篇 |
一般工业技术 | 3486篇 |
冶金工业 | 4651篇 |
原子能技术 | 277篇 |
自动化技术 | 657篇 |
出版年
2024年 | 118篇 |
2023年 | 403篇 |
2022年 | 973篇 |
2021年 | 1317篇 |
2020年 | 1201篇 |
2019年 | 871篇 |
2018年 | 871篇 |
2017年 | 1120篇 |
2016年 | 1157篇 |
2015年 | 1297篇 |
2014年 | 2454篇 |
2013年 | 2368篇 |
2012年 | 3164篇 |
2011年 | 3395篇 |
2010年 | 2882篇 |
2009年 | 3025篇 |
2008年 | 2305篇 |
2007年 | 3184篇 |
2006年 | 3166篇 |
2005年 | 2657篇 |
2004年 | 2280篇 |
2003年 | 2097篇 |
2002年 | 1726篇 |
2001年 | 1347篇 |
2000年 | 1071篇 |
1999年 | 821篇 |
1998年 | 636篇 |
1997年 | 515篇 |
1996年 | 391篇 |
1995年 | 371篇 |
1994年 | 261篇 |
1993年 | 196篇 |
1992年 | 187篇 |
1991年 | 147篇 |
1990年 | 94篇 |
1989年 | 123篇 |
1988年 | 70篇 |
1987年 | 65篇 |
1986年 | 45篇 |
1985年 | 46篇 |
1984年 | 50篇 |
1983年 | 42篇 |
1982年 | 21篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1966年 | 9篇 |
1965年 | 7篇 |
1964年 | 9篇 |
1959年 | 7篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
《Intermetallics》2015
Fine-grained fully-lamellar (FL) microstructure is desired for TiAl components to serve as compressor/turbine blades and turbocharger turbine wheels. This study deals with the process and phase transformation to produce FL microstructure for Mo stabilized beta-gamma TiAl alloys without single α-phase field. Unlike the α + γ two-phased TiAl or beta-gamma TiAl with single α-phase field, the wrought multi-phase TiAl–4/6Nb–2Mo–B/Y alloys exhibit special annealing process to obtain FL microstructure. Short-term annealing at temperatures slightly above β-transus is recommended to produce the desired FL microstructure. The related mechanism is to guarantee the sufficient diffusion homogenization of β stabilizers during single β-phase annealing, and further avoid α decomposition by α → γ + β when cooling through α + β + γ phase field. The colony boundary β phase contributes to fine-grained nearly FL microstructure, by retarding the coarsening of the α phase grains. 相似文献
32.
《稀有金属材料与工程》2019,36(1):25-29
研究了轧制变形量对WSTi544221合金棒材显微组织和力学性能的影响,并对Φ10 mm规格的棒材进行不同制度的固溶+时效处理,对比了不同热处理状态下棒材的组织和力学性能。结果表明,随着轧制变形量的增大,WSTi544221合金棒材的晶粒细化程度增大,强度逐渐提高,但塑性变化不大。经870℃×1 h/WC+520℃×6 h/AC固溶+时效处理后,强度与塑性可以获得良好匹配,当抗拉强度达到1 610 MPa、屈服强度达到1 531 MPa时,延伸率和断面收缩率可分别保持在12%和43%。 相似文献
33.
34.
在Fe-As(Ⅲ)-Cu(Ⅱ)-H2O体系中, 研究了酸性废水中As(Ⅲ)、Cu(Ⅱ)与金属铁粉的反应行为, 考察了反应过程中As在气、液、固三相中的分配比。结果表明, As(Ⅲ)和Cu(Ⅱ)离子被Fe还原为单质As和Cu后, As、Cu进一步结合成Cu5As2等金属间化合物, 从而促进As(Ⅲ)沉淀反应的发生, 且无AsH3生成。在反应时间40min、铁粉过量系数1.2、溶液初始pH=0.0、温度40 ℃、Cu/As摩尔比1.0条件下, As在气、液、固三相中的分配比分别为0、20.7%和79.3%, 沉砷率为79.3%。 相似文献
35.
以无锡某厂食堂污水处理及中水回用为例,探讨采用"隔油+混凝沉淀+A^2/O+MBR"工艺就地处理餐厨污水,并将出水回用于厂区冲厕可行性。经过78 d的调试,该工艺实现了餐厨污水中污染物的去除,COD小于50mg/L,NH4^+-N质量浓度小于5 mg/L,总氮小于10 mg/L,总磷小于0.5 mg/L,大肠杆菌数小于2个/L,基本满足中水回用要求。经计算吨水处理成本9.83元,含电费、药剂费、人工费、污泥处理费及膜更换费用。结合中水回用节省自来水后计算吨水处理综合成本为5.23元,大幅降低公司对市政供水的依赖,降低公司用水成本。 相似文献
36.
37.
38.
The rapid expansion of the photovoltaic (PV) module market in the last years will determine in the near future a remarkable growth of corresponding waste. Then, the hazardous materials contained in the modules, such as Cd, Pb and Cr, could be released in the environment if the waste panels will not be handled adequately. Recycling processes of silicon crystalline panels, finalized to separate PV cells from the glass, involve the removal of the EVA (Ethylene Vinyl Acetate) layer through different methods, as the thermal treatment. During this treatment, some hazardous components can be released due to thermal degradation process. In this paper the metals released in the gas emissions and in the ashes due to the thermal treatment of modules were evaluated. For this purpose, three samples of crystalline panels were heated in furnace up to 600 °C and the complete degradation of the EVA was obtained. A mass balance between the sample and its components, before and after treatment, was performed in order to assess the weight loss percentage. Finally, after thermal treatment a qualitative analysis on the separated PV cell surface was performed by SEM-EDS (Scanning Electron Microscope equipped with Energy Dispersive Spectrometer). 相似文献
39.
Izabella Jackowska Monika Bojanowska Monika Staszowska-Karkut Monika Sachadyn-Król 《International Journal of Food Science & Technology》2019,54(12):3175-3184
Ozonation is an innovative way to preserve high quality of seed during storage and it is an alternative to harmful organophosphorus agents. Disclosure of changes in the rapeseed oil under the influence of oxidative action of ozone on the seeds was the aim of the work and is presented for the first time. Two ozone concentrations and different length of ozonation were applied. The changes in tocopherols, phenolics, flavonoids contents, antiradical activity and oxidative stability were examined. The average vitamin E concentration was 33 mg per 100 g of oil before and 31.7 after ozonation of seeds. The average content of phenolic compounds was 14.3 mg of sinapic acid g−1 and 16.9 after the ozone treatment. Changes in the flavonoids content and antioxidant activity were observed too. Ozonation caused a decrease in the vitamin E concentration which resulted also in reducing the quenching of free radicals and reduction of oil induction time. 相似文献
40.
Photocatalysts have attracted great research interest owing to their excellent properties and potential for simultaneously addressing challenges related to energy needs and environmental pollution. Photocatalytic particles need to be in contact with their respective media to exhibit efficient photocatalytic performances. However, it is difficult to separate nanometer-sized photocatalytic materials from reaction media later, which may lead to secondary pollution and a poor recycling performance. Hydrogel photocatalysts with a three-dimensional (3D) network structures are promising support materials for photocatalysts based on features such as high specific surface areas and adsorption capacities and good environmental compatibility. In this review, hydrogel photocatalysts are classified into two different categories depending on their elemental composition and recent progresses in the methods for preparing hydrogel photocatalysts are summarized. Moreover, current applications of hydrogel photocatalysts in energy conversion and environmental remediation are reviewed. Furthermore, a comprehensive outlook and highlight future challenges in the development of hydrogel photocatalysts are presented. 相似文献