全文获取类型
收费全文 | 1110篇 |
免费 | 103篇 |
国内免费 | 58篇 |
专业分类
电工技术 | 32篇 |
综合类 | 56篇 |
化学工业 | 513篇 |
金属工艺 | 37篇 |
机械仪表 | 15篇 |
建筑科学 | 21篇 |
矿业工程 | 29篇 |
能源动力 | 31篇 |
轻工业 | 215篇 |
水利工程 | 5篇 |
石油天然气 | 43篇 |
武器工业 | 10篇 |
无线电 | 55篇 |
一般工业技术 | 109篇 |
冶金工业 | 53篇 |
原子能技术 | 33篇 |
自动化技术 | 14篇 |
出版年
2024年 | 1篇 |
2023年 | 28篇 |
2022年 | 26篇 |
2021年 | 47篇 |
2020年 | 40篇 |
2019年 | 36篇 |
2018年 | 24篇 |
2017年 | 32篇 |
2016年 | 33篇 |
2015年 | 35篇 |
2014年 | 52篇 |
2013年 | 63篇 |
2012年 | 100篇 |
2011年 | 97篇 |
2010年 | 67篇 |
2009年 | 60篇 |
2008年 | 56篇 |
2007年 | 76篇 |
2006年 | 55篇 |
2005年 | 69篇 |
2004年 | 53篇 |
2003年 | 35篇 |
2002年 | 30篇 |
2001年 | 22篇 |
2000年 | 21篇 |
1999年 | 13篇 |
1998年 | 15篇 |
1997年 | 20篇 |
1996年 | 8篇 |
1995年 | 14篇 |
1994年 | 8篇 |
1993年 | 8篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
排序方式: 共有1271条查询结果,搜索用时 15 毫秒
21.
Direct methanol alkaline fuel cells with catalysed anion exchange membrane electrodes 总被引:2,自引:0,他引:2
Membrane electrodes prepared by chemical deposition of platinum directly onto the anion exchange membrane electrolyte were tested in direct methanol alkaline fuel cells. Data on the cell voltage against current density performance and anode potentials are reported. The relatively low fuel cell performance was probably due to the low active surface area of Pt deposits on the membrane comparing to other membrane electrode assembly (MEA) fabrication methods. However, the catalysed membrane electrode showed good performance for oxygen reduction. A reduction in cell internal resistance was also obtained for the catalysed membrane electrode. By combining the catalysed membrane electrodes with a catalysed mesh, maximum current density of 98 mA cm–2 and peak power density of 18 mW cm–2 were achieved. 相似文献
22.
23.
F~-对钛在NaBr水溶液中阳极极化行为的影响 总被引:1,自引:0,他引:1
利用电化学方法研究了F对工业纯钛(TAl)在NaBr水溶液中阳极极化行为的影响。结果发现,F加速了钛表面膜的阳极溶解速度,减缓了膜的增厚,提高了孔蚀电位,但对再钝化电位无影响。 相似文献
24.
25.
Kang Cui Kunal S. Mali Klaus Müllen Michael Walter Steven De Feyter Stijn F. L. Mertens 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(46)
Ionic self‐assembly of charged molecular building blocks relies on the interplay between long‐range electrostatic forces and short‐range, often cooperative, supramolecular interactions, yet has been seldom studied in two dimensions at the solid–liquid interface. Here, we demonstrate anion‐driven switching of two‐dimensional (2D) crystal structure at the Au(111)/octanoic acid interface. Using scanning tunneling microscopy (STM), three organic salts with identical polyaromatic cation (PQPC6+) but different anions (perchlorate, anthraquinonedisulfonate, benzenesulfonate) are shown to form distinct, highly ordered self‐assembled structures. Reversible switching of the supramolecular arrangement is demonstrated by in situ exchange of the anion on the pre‐formed adlayer, by changing the concentration ratio between the incoming and outgoing anion. Density functional theory (DFT) calculations reveal that perchlorate is highly mobile in the adlayer, and corroborate why this anion is only resolved transiently in STM. Surprisingly, the templating effect of the anion persists even where it does not become part of the adlayer 2D fabric, which we ascribe to differences in stabilization of cation conformations by the anion. Our results provide important insight into the structuring of mixed anion–cation adlayers. This is essential in the design of tectons for ionic self‐assembled superstructures and biomimetic adaptive materials and valuable also to understand adsorbate–adsorbate interactions in heterogeneous catalysis. 相似文献
26.
水煤浆添加剂的研究进展 总被引:15,自引:0,他引:15
随着世界原油资源的日渐减少及燃煤污染的日趋严重,水煤浆作为一种新型的环保型煤基流体燃料日益受到人们的重视。从70年代至今,国内外学都研究过多种添加剂,目前制浆用添加剂主要分为阴离子表面活性和非离子表面活性剂两大类,但高效、价廉、适用性广的添加剂为数并不多。 相似文献
27.
阴离子交换树脂分离提取发酵液中的乳酸 总被引:1,自引:0,他引:1
为提高乳酸产品收率和纯度,实验筛选得到国产315型阴离子交换树脂,用于分离提取发酵液中乳酸,并研究其对乳酸、乙酸、丙酮酸及柠檬酸的吸附等温线、吸附动力学和动态吸附及洗脱效果.吸附等温线结果表明,315型树脂对乳酸等有机酸的吸附等温线符合Freundlich方程,特征参数n>1,属于优惠吸附.吸附动力学研究表明,液膜扩散是吸附过程的主要控制步骤,符合Boyd 液膜扩散模型.动态吸附及洗脱实验结果表明,以15 BV/h、pH 188上柱吸附,再用1 BV/h的去离子水洗脱,可实现发酵液中乳酸的良好分离. 相似文献
28.
大学校园空气负离子的分布规律研究 总被引:1,自引:0,他引:1
为研究城市小区域空气负离子的分布规律,以陕西科技大学西安校区内多处典型环境为测量样本,分别在不同天气条件和不同时间段进行测量.统计分析表明,天气由晴转雨时的空气负离子浓度会迅速提升;雨中,空气负离子浓度最大;室内空气负离子浓度远低于室外;中午,空气负离子浓度最高.研究认为,空气负离子浓度主要受温度、湿度、气流、水流、空气悬浮物等环境因子影响. 相似文献
29.
Growth units and the crystallization habit of BaTiO3 nanocrystals have been investigated. It has been proposed that the growth units of BaTiO3 were surface hydroxylated Ti(OH)62- octahedra. The relationship between crystal morphology and the variation of the current intensity in the solution has been obtained through the measurement of the OH in the solution and the hydrothermal experiment with superimposed direct electric field. Based on the computation of the stability energy of the growth units, the relationship between the crystallized morphology of crystallites and the most favorable growth units under different conditions has been derived. It has been found that there is structure similarity between anatase (TiO2) and BaTiO3 from the crystal chemistry viewpoint, so they are soluble in each other, which can serve as a reasonable explanation for the abnormal phenomenon of the retention of cubic substable phase at room temperature. 相似文献
30.
研究测定了各种运行条件下弱碱性阴离子交换树脂的残余交换容量,导出了根据层高、流向、流速、温度、进水酸度和二氧化碳及硫酸浓度等求残余交换容量的经验公式. 相似文献