全文获取类型
收费全文 | 11077篇 |
免费 | 1074篇 |
国内免费 | 217篇 |
专业分类
电工技术 | 133篇 |
综合类 | 427篇 |
化学工业 | 2517篇 |
金属工艺 | 288篇 |
机械仪表 | 409篇 |
建筑科学 | 374篇 |
矿业工程 | 177篇 |
能源动力 | 143篇 |
轻工业 | 5191篇 |
水利工程 | 42篇 |
石油天然气 | 338篇 |
武器工业 | 39篇 |
无线电 | 222篇 |
一般工业技术 | 1029篇 |
冶金工业 | 373篇 |
原子能技术 | 242篇 |
自动化技术 | 424篇 |
出版年
2024年 | 93篇 |
2023年 | 250篇 |
2022年 | 391篇 |
2021年 | 591篇 |
2020年 | 550篇 |
2019年 | 467篇 |
2018年 | 479篇 |
2017年 | 442篇 |
2016年 | 460篇 |
2015年 | 461篇 |
2014年 | 642篇 |
2013年 | 919篇 |
2012年 | 782篇 |
2011年 | 702篇 |
2010年 | 558篇 |
2009年 | 512篇 |
2008年 | 452篇 |
2007年 | 527篇 |
2006年 | 486篇 |
2005年 | 394篇 |
2004年 | 335篇 |
2003年 | 320篇 |
2002年 | 262篇 |
2001年 | 219篇 |
2000年 | 169篇 |
1999年 | 144篇 |
1998年 | 121篇 |
1997年 | 118篇 |
1996年 | 70篇 |
1995年 | 65篇 |
1994年 | 59篇 |
1993年 | 51篇 |
1992年 | 53篇 |
1991年 | 15篇 |
1990年 | 25篇 |
1989年 | 20篇 |
1988年 | 15篇 |
1987年 | 26篇 |
1986年 | 23篇 |
1985年 | 31篇 |
1984年 | 22篇 |
1983年 | 10篇 |
1982年 | 17篇 |
1981年 | 5篇 |
1980年 | 10篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1970年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
M Isabel Sánchez de Rojas Julián Rivera Moisés Frías Félix Marín 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(3):209-217
Copper slag is a by‐product generated during smelting to extract copper metal from the ore. The copper slag obtained may exhibit pozzolanic activity and may therefore be used in the manufacture of addition‐containing cements. In this paper the effect of the incorporation of the copper slag in cement is measured. Blends of copper slag with Portland cement generally possess properties equivalent to Portland cement containing fly ash, but very different to the silica fume incorporation. Copper slag and fly ash reduce the heat of hydration more effectively than silica fume in mortars. The replacement of 30% cement by copper slag reduces the flexural and compressive strength in a similar way to fly ash; however, after 28 days, the reduction is less than the percentage of substitution. Hydrated calcium aluminate phases were analysed using scanning electron microscopy (SEM) and X‐ray diffraction (XRD) techniques. The pozzolanic activity of copper slag is similar to that of fly ash and higher than silica fume. In the presence of low water/cement ratios, certain pozzolanic materials produce a very compact cement paste that limits the space available for hydration products, a determining factor in the formation of hydrated calcium aluminates. SEM was found to be a useful analytical technique when aluminates are formed and can be clearly detected by XRD. Copyright © 2008 Society of Chemical Industry 相似文献
32.
The interaction of different metal oxides such as Co3O4, NiO, Al2O3, Cr2O3, Fe2O3 and SiO2 with Na2SO4 at a temperature of 1100 and 1200 K in flowing oxygen has been studied. The thermogravimetric studies for each system were
carried out as a function of Na2SO4 in the mixture. The presence of different constituents in the reaction products were identified by X-ray diffraction analysis
and the morphologies of the reaction products were characterized using metallography and scanning electron microscopy (SEM).
The formation of products was also investigated by thermodynamic computation of free energies of the reactions and the study
of relevant equilibrium phase diagrams. The soluble species in the aqueous solutions of the reaction products were determined
quantitatively using atomic absorption spectrophotometry.
The high temperature interaction products usually contain a 3-phase structure namely, Na2O·M2O
x
, M2O
x
and metal sulphide and/or metal sulphate. The formation of Na2O·M2O
x
depends upon the solid state solubility of metal oxide in the molten salt at high temperatures. Under limited solubility
conditions Na2O·M2O
x
is invariably formed, but as soon as this condition is relaxed the oxide. M2O
x
, precipitates and forms a separate phase. 相似文献
33.
实验采用复合酶制剂处理美国红鱼,红鱼肉中的蛋白质及各种营养成分的价值都得到了提高,通过优化实验工艺条件,确定了红鱼重组香肠加工生产的最佳加工工艺条件。 相似文献
34.
Tang Yuanyan 《Frontiers of Computer Science in China》2007,1(2):123-125
This paper gives an introduction and remarks on two review papers for Chinese character recognition. One review is made by
Chinese authors, another is from American scientists. They investigate Chinese character from different language environments;
they do the research from different points of view. Thus, a more comprehensive view on Chinese character recognition, which
is an important branch of pattern recognition, can be provided to the readers. Meantime, one article pays attention to online
process, and other paper deals with offline recognition, which complement each other.
The author is the Associate Editor-in-Chief of Frontiers of Computer Science in China 相似文献
35.
36.
37.
对照IS0 9001质量管理体系标推的要求,结合石化销售企业质量管理工作中存在的主要问题,提出质量管理工作创新的建议。 相似文献
38.
国际乳业的热点论题:蛋白质标准化 总被引:1,自引:0,他引:1
介绍了蛋白质的标准化这一国际乳品界正热的研究和讨论题目,综述了蛋白质标准化的必要性和世界上目前采用的方法,展望了膜技术在蛋白质标准化上的应用前景。 相似文献
39.
40.