全文获取类型
收费全文 | 11504篇 |
免费 | 1637篇 |
国内免费 | 975篇 |
专业分类
电工技术 | 993篇 |
综合类 | 1251篇 |
化学工业 | 1337篇 |
金属工艺 | 825篇 |
机械仪表 | 288篇 |
建筑科学 | 1331篇 |
矿业工程 | 1048篇 |
能源动力 | 614篇 |
轻工业 | 612篇 |
水利工程 | 358篇 |
石油天然气 | 1701篇 |
武器工业 | 65篇 |
无线电 | 572篇 |
一般工业技术 | 968篇 |
冶金工业 | 1090篇 |
原子能技术 | 211篇 |
自动化技术 | 852篇 |
出版年
2024年 | 20篇 |
2023年 | 189篇 |
2022年 | 341篇 |
2021年 | 444篇 |
2020年 | 518篇 |
2019年 | 406篇 |
2018年 | 352篇 |
2017年 | 418篇 |
2016年 | 498篇 |
2015年 | 455篇 |
2014年 | 672篇 |
2013年 | 764篇 |
2012年 | 793篇 |
2011年 | 909篇 |
2010年 | 664篇 |
2009年 | 690篇 |
2008年 | 633篇 |
2007年 | 706篇 |
2006年 | 652篇 |
2005年 | 592篇 |
2004年 | 555篇 |
2003年 | 394篇 |
2002年 | 381篇 |
2001年 | 300篇 |
2000年 | 262篇 |
1999年 | 254篇 |
1998年 | 157篇 |
1997年 | 173篇 |
1996年 | 140篇 |
1995年 | 137篇 |
1994年 | 129篇 |
1993年 | 106篇 |
1992年 | 90篇 |
1991年 | 61篇 |
1990年 | 52篇 |
1989年 | 46篇 |
1988年 | 39篇 |
1987年 | 22篇 |
1986年 | 30篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1960年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
为探究膨胀机主轴的缝隙腐蚀行为,搭建了模拟缝隙腐蚀实验装置。通过电化学测试,确定了不同缝隙位置处的自腐蚀电位随时间的变化规律,并揭示了缝隙内腐蚀反应的发展过程。结果表明:缝隙内腐蚀反应经历双电层形成-氧浓差电池形成-金属水解三个反应过程。在富氧条件下,腐蚀产物的主要成分为Fe(OH)2。随着氧气的耗尽,氧浓差电池形成,腐蚀产物逐渐向FeOOH和Fe3O4转变。 相似文献
12.
13.
14.
Identification of potential technologies for 1,4-Butanediol production using prospecting methodology
Ramon Geraldo Campos Silva Tatiana Felix Ferreira Élcio Ribeiro Borges 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2020,95(12):3057-3070
1,4-Butanediol (1,4-BDO) is a four-carbon diol used for industrial applications such as organic solvents, and the production of adhesives, fibers and polyurethanes. 1,4-BDO currently is produced through several petrochemical routes: hydrogenation of maleic anhydride, isomerization of propylene oxide, acetoxylation of butadiene, and the reaction between formaldehyde and acetylene. The current trends in 1,4-BDO production involve the utilization of renewable sources such as biomass. In this context, the present study aimed to identify promising technologies of 1,4-BDO production through prospecting methodology based on the analyses of patents and scientific article, describing the most relevant aspects of those emerging technologies. An increasing amount of 1,4-BDO production focused on biotechnological routes has been reported, with the US heavily involved in the development of new technologies. This study tracked three promising technologies which have potential for application in a biorefinery context because those processes involve (i) production of 1,4-BDO from sugars, classified herein as the biotechnological route; (ii) production of intermediates from sugar fermentation followed by catalytic conversion into 1,4-BDO, classified herein as the hybrid route, and (iii) furan/furfural conversion into 1,4-BDO. © 2020 Society of Chemical Industry 相似文献
15.
《International Journal of Hydrogen Energy》2020,45(53):28272-28284
Anion exchange membrane water electrolysis (AEMWE) has acquired substantial consideration as a cost-effective hydrogen production technology. The anion ionomer content in the catalyst layers during hydrogen and oxygen evolution reaction (HER and OER) is of ultimate significance. Herein, an in-situ half-cell analysis with reference electrodes was carried out for simultaneous potential measurements and identification of the influence of the anion exchange ionomer (AEI) content on anode and cathode performance. The measured half-cell potentials proved the influence of AEI content on the catalytic activity of HER and OER, which was supported by the rotating disk electrode (RDE) measurements. Cathode overpotential of Ni/C was not negligible and more affected by the AEI content than anode with the optimized AEI content of 10 wt% while NiO anode OER overpotential was independent of the AEI content. For the same AEI content, PGM catalysts showed higher electroactivity than Ni-based catalysts for HER and OER and the cathode catalyst's intrinsic activity is of high importance in the AEM electrolysis operation. Post-mortem analysis by SEM mapping of both AEI and catalyst distributions on the electrode surface showed the effect of AEI loading on the catalyst morphology, which could be related to the electrode performance. 相似文献
16.
《International Journal of Hydrogen Energy》2020,45(38):19324-19334
The effective Ni–Cu bimetallic nanocomposite was deposited on a glassy carbon electrode, GCE, that modified with carbon quantum dots, CQDs. The deposition process was done by one-step and controllable electrochemical method in an electrolyte of nickel and copper sulfate. The structural properties of composite studied by techniques such as X-ray diffraction, XRD, energy dispersive X-ray analysis, EDX, field emission scanning electron microscopy, FESEM, and transmission electron microscopy, TEM. Ni–Cu/RCQDs nanocomposite was applied as a cathode for catalysis of hydrogen evolution reaction, HER, in acidic media by cyclic voltammetry, CV, linear sweep voltammetry, LSV, chronoamperometry, CA, and electrochemical impedance spectroscopy, EIS. The onset potential, Eonset, for the evolution of hydrogen at the current density of −10 mA cm−2 for Ni–Cu/RCQDs was −230 mV vs. SHE that had a 100 mV shift to positive voltages in comparison with Ni–Cu catalyst. It can be related to the synergistic effect between metallic nanoparticles. V. dec−1, respectively. 相似文献
17.
18.
《International Journal of Hydrogen Energy》2020,45(7):4054-4064
The feasibility of microbial hydrogen consumption to mitigate the hydrogen embrittlement (HE) under different cathodic potentials was evaluated using the Devanathan-Stachurski electrochemical test and the hydrogen permeation efficiency η. The hydrogen permeation efficiency η in the presence of strain GA-1 was lower than that in sterile medium. The cathodic potential inhibited the adherence of strain GA-1 to AISI 4135 steel surface, thereby reducing the hydrogen consumption of strain GA-1. The adherent GA-1 cells were capable of consuming ‘cathodic hydrogen’ and reducing the proportions of absorbed hydrogen, indicating that it is theoretically possible to control HE by hydrogen-consuming microbes. 相似文献
19.
Multilayer assembly of ionic starches on old corrugated container recycled cellulosic fibers 下载免费PDF全文
Hamidreza Rudi Yahya Hamzeh Esmaeil Rasooly Garmaroody Seyed Rahman Djafari Petroudy Mousa M Nazhad 《Polymer International》2018,67(1):85-90
In this study, old corrugated container recycled fibers were treated with polyelectrolyte multilayers consisting of biopolymer cationic starch with two degrees of substitution (DS) each in combination with one anionic starch. Pulp zeta potential, paper strength and the thin layer ellipsometry technique were applied to examine the influence of cationic starch DS on the formation of polyelectrolyte multilayers. The results indicated a significant interaction between the DS of cationic starch and the number of ionic starch layers formed. When low‐DS cationic starch was used, the pulp zeta potential and the paper strength increased significantly in assembling the first cationic layer. However, in depositing high‐DS cationic starch a greater zeta potential and a stronger influence on the paper strength were observed with a larger number of starch layers. This was confirmed by thin layer ellipsometry when a greater thickness of multilayers was achieved by employing high‐DS cationic starch to form a higher number of layers. © 2017 Society of Chemical Industry 相似文献
20.
《Journal of the European Ceramic Society》2020,40(15):5029-5036
Interaction between grain boundaries and impurities usually leads to significant altering of material properties. Understanding the composition-structure-property relationship of grain boundaries is a key avenue for tailoring and designing high performance materials. In this work, we studied segregation of W into ZrB2 grain boundaries by a hybrid method combining Monte Carlo (MC) and molecular dynamics (MD), and examined the effects of segregation on grain boundary strengths by MD tensile testing with a fitted machine learning potential. It is found that W prefers grain boundary sites with local compression strains due to its smaller size compared to Zr. Rich segregation patterns (including monolayer, off-center bilayer, and other complex patterns); segregation induced grain boundary structure reconstruction; and order-disorder like segregation pattern transformation are discovered. Strong segregation tendency of W into ZrB2 grain boundaries and significant improvements on grain boundary strengths are certified, which guarantees outstanding high temperature performance of ZrB2-based UHTCs. 相似文献