全文获取类型
收费全文 | 10834篇 |
免费 | 926篇 |
国内免费 | 1087篇 |
专业分类
电工技术 | 129篇 |
技术理论 | 1篇 |
综合类 | 623篇 |
化学工业 | 6431篇 |
金属工艺 | 598篇 |
机械仪表 | 197篇 |
建筑科学 | 335篇 |
矿业工程 | 221篇 |
能源动力 | 209篇 |
轻工业 | 378篇 |
水利工程 | 94篇 |
石油天然气 | 247篇 |
武器工业 | 1153篇 |
无线电 | 406篇 |
一般工业技术 | 948篇 |
冶金工业 | 368篇 |
原子能技术 | 127篇 |
自动化技术 | 382篇 |
出版年
2024年 | 19篇 |
2023年 | 153篇 |
2022年 | 189篇 |
2021年 | 275篇 |
2020年 | 298篇 |
2019年 | 314篇 |
2018年 | 298篇 |
2017年 | 319篇 |
2016年 | 343篇 |
2015年 | 513篇 |
2014年 | 863篇 |
2013年 | 751篇 |
2012年 | 904篇 |
2011年 | 1052篇 |
2010年 | 857篇 |
2009年 | 844篇 |
2008年 | 665篇 |
2007年 | 749篇 |
2006年 | 642篇 |
2005年 | 561篇 |
2004年 | 447篇 |
2003年 | 393篇 |
2002年 | 242篇 |
2001年 | 195篇 |
2000年 | 173篇 |
1999年 | 146篇 |
1998年 | 84篇 |
1997年 | 65篇 |
1996年 | 76篇 |
1995年 | 53篇 |
1994年 | 39篇 |
1993年 | 39篇 |
1992年 | 69篇 |
1991年 | 37篇 |
1990年 | 31篇 |
1989年 | 32篇 |
1988年 | 17篇 |
1987年 | 14篇 |
1986年 | 13篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1975年 | 3篇 |
1971年 | 5篇 |
1959年 | 3篇 |
1957年 | 4篇 |
1955年 | 2篇 |
1954年 | 5篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《Food Control》2015
Cookies and biscuits are a recognized source of trans fatty acids (TFA). Aware of its consumption worldwide, an update on TFA content was taken in 2012, in a total of 50 samples commercialized in Portugal. Despite the absence of specific Portuguese legislation, TFA amounts in cookies and biscuits are generally low, with TFA amounts lower than 0.1 g per 100 g, and an average of 0.6% in the extracted fat in 49 of the 50 samples analyzed. Unfortunately, one sample presented 27% of TFA in the lipids, highlighting that the problem is still present. Also, a high prevalence of saturated fatty acids was observed, as high as 92.4% in the fat (53.0% on average). This fact is also a major health concern, particularly when the reformulation of these products in the last years (2006–2012) was effective regarding TFA reduction but seemed to have occurred at expenses of increasing SFA, thus reducing the potential beneficial effect achievable by replacing with cis-unsaturated fats, as generally recommended. 相似文献
2.
The surface chemistry and mineral liberation changes of a porphyry copper ore after high voltage pulse (HVP) electrical comminution have been investigated using X-ray photoelectron spectroscopy (XPS) and mineral liberation analysis (MLA). Previous studies suggest that electrical comminution has the potential to improve downstream flotation recoveries, due to increased mineral liberation. However, until now the effects on the surface chemistry have not been investigated in detail.The mineral liberation results showed that chalcopyrite was more liberated in the electrical comminution product than in mechanical comminution, noticeably in the coarser size fractions. The surface chemistry of pure chalcopyrite was investigated, using XPS, and high resolution scans of iron and sulphur showed that both comminution methods led to iron oxidising preferentially leaving behind a passivating film of copper sulphides. However, the HVP product oxidisation was more severe with more iron oxide being produced and further oxidation of the remaining copper sulphides into copper sulphate. An attrition grinding stage may be useful in removing the oxidised layer from the surface of the particles prior to flotation separation. This paper presents a new application of the HVP technology in hybrid procedures using electrical comminution and mechanical grinding to prepare the flotation feed, rather than using excessive pulse energy to fully disintegrate ore to the flotation size. Better liberation and flotation performance were achieved through the hybrid procedures than the comparative mechanical comminution. 相似文献
3.
Two‐dimensional arrangements of molecules can show remarkable cooperative electronic effects. Such effects can serve to achieve direct electronic sensing of chemical and physical processes via electrostatic effects, i.e., without transfer of charge or matter between the locus of sensing and that of detection. 相似文献
4.
5.
Anumberoflanthanideternarycomplexescon tainingheterocyclicamineshavebeenreportedsince1960 [1] .Inrecentyearsmuchattentionhasbeenpaidtoquaternarycomplexesoflanthanidesbecauseofin terestingstructure ,coordinationmode ,competitionre actionandproperty[2~ 9] .ESRcane… 相似文献
6.
7.
应用型机械本科专业教学体系改革研究与实践 总被引:4,自引:0,他引:4
根据当前高等教育改革与发展的指导思想,紧紧围绕国家实施制造业信息化建设工程为背景,积极配合打造浙江先进制造业基地建设,结合现代机械专业结构调整,本着交叉、复合、应用型人才的培养目标,塑造具有宽口径、厚基础和强创新意识的人才培养理念,以数字化设计制造为核心,以机械技术、电子技术、信息技术和管理学科结合为主线,突出知识综合与创新能力,强调专业实践与专业知识的有效结合,有的放矢实施机械专业教学改革与实践。 相似文献
8.
介绍了隔河岩电厂220kV线路保护的原理设计及运行情况,以及采用了双重微机化继电保护装置后带来的优越性,简要描述了CSL-101A高频保护和RCS-931A光纤保护的应用特点。 相似文献
9.
文中介绍了工程化学基础课程改革思想的提出,在教改过程中通过遴选合适的教材、修订教学大纲,建全教学文件、适当运用现代化教学手段和积极进行师资队伍建设等改革方案的实施,在教学实践中适应科技发展,培养工程概念,增强环保和经济意识,及时更新教学内容,提高教学质量。 相似文献
10.
Photoacousticspectroscopy (PAS)hasbeenusedtonondestructivelyinvestigatealmostallkindsofsam ples,whetherthesampleiscrystalline ,powderorgel .PAspectr oscopyisacalorimetrictechniquewhichmeasurestheenergyabsorbedandsubsequentheatingofthesamplesduetoanonradiativerelaxationpro cess .ThereforePAScanbeusedtostudyopaque ,highlyreflectiveandscatteringsamples ,whicharedif ficulttostudybyconventionalspectroscopytech niques[1] .Withouttheneedofsamplepreparation ,PASavoidstheriskofsamplealteration ,pre… 相似文献