全文获取类型
收费全文 | 30548篇 |
免费 | 2557篇 |
国内免费 | 1330篇 |
专业分类
电工技术 | 550篇 |
综合类 | 1830篇 |
化学工业 | 10204篇 |
金属工艺 | 2893篇 |
机械仪表 | 796篇 |
建筑科学 | 1400篇 |
矿业工程 | 1195篇 |
能源动力 | 549篇 |
轻工业 | 3942篇 |
水利工程 | 167篇 |
石油天然气 | 2459篇 |
武器工业 | 301篇 |
无线电 | 594篇 |
一般工业技术 | 3654篇 |
冶金工业 | 3643篇 |
原子能技术 | 121篇 |
自动化技术 | 137篇 |
出版年
2024年 | 113篇 |
2023年 | 445篇 |
2022年 | 861篇 |
2021年 | 1133篇 |
2020年 | 973篇 |
2019年 | 801篇 |
2018年 | 763篇 |
2017年 | 952篇 |
2016年 | 918篇 |
2015年 | 949篇 |
2014年 | 1438篇 |
2013年 | 1570篇 |
2012年 | 1949篇 |
2011年 | 2070篇 |
2010年 | 1562篇 |
2009年 | 1499篇 |
2008年 | 1332篇 |
2007年 | 1894篇 |
2006年 | 1962篇 |
2005年 | 1782篇 |
2004年 | 1534篇 |
2003年 | 1313篇 |
2002年 | 1204篇 |
2001年 | 990篇 |
2000年 | 877篇 |
1999年 | 707篇 |
1998年 | 591篇 |
1997年 | 464篇 |
1996年 | 363篇 |
1995年 | 307篇 |
1994年 | 300篇 |
1993年 | 229篇 |
1992年 | 184篇 |
1991年 | 94篇 |
1990年 | 76篇 |
1989年 | 64篇 |
1988年 | 33篇 |
1987年 | 30篇 |
1986年 | 15篇 |
1985年 | 15篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 15篇 |
1980年 | 13篇 |
1979年 | 2篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
两步法合成双氰胺工艺 总被引:1,自引:0,他引:1
采用两步法由氰氨化钙合成双氰胺,通过正交试验,考察了水解温度、聚合温度、聚合时间对产品收率的影响,确定了最佳的工艺条件:水解温度42℃、聚合温度70℃、聚合时问150 min,此条件下,双氰胺收率可达85.73%。 相似文献
42.
A Oyane M Kasahara N Ichinose Y Yokoyama M Uchida A Ito 《武汉理工大学学报(材料科学英文版)》2005,20(B12):220-222
A synthetic polymer with a laminin-apatite composite layer on its surface would be useful as a percutaneous device. The preparation of such a composite was attempted in the present study using poly( ethylene terephthalate ) (PET) and polyethylene (PE) as the synthetic polymer. PET and PE plates and those pretreated with an oxygen plasma were alternately dipped in calcium and phosphate ion solutions, and then immersed in a metastable calcium phosphate solution supplemented with laminin ( LCP solution ). The PET and PE plates pretreated with an oxygen plasma formed a uniform and continuous layer of a laminin-apatite composite on their surfaces. In contrast, the PET and PE plates that had not been pretreated with an oxygen plasma did not form a continuous layer of a laminin-apatite composite on their surfaces. The hydrophilic functional groups on the PET and PE surfaces introduced by the plasma treatment were responsible for the successful laminin-apatite coruposite coating. 相似文献
43.
QifengShu JiayunZhang 《北京科技大学学报(英文版)》2005,12(3):221-224
Based on recently published experimental data, the Riboud model was modified for viscosity estimation of the slags containing calcium fluoride. The estimated values were in good agreement with measured data. Reasonable estimation can be achieved using the modified Riboud model for mould fluxes and ESR (eletro slag remelting) slags. Especially for ESR slags, the modified Riboud model can provide much more precise values than the original Riboud model. 相似文献
44.
45.
Tomi Gominek Andrej Lubej Ciril Pohar 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(8):939-947
Precipitation of calcium sulfate dihydrate, gypsum, from (i) a pure sulfuric acid/lime suspension and (ii) a waste sulfuric acid/lime suspension in a continuous pilot plant in the temperature range from 40 °C to 80 °C was studied. It was observed that in the case of waste sulfuric acid with a high content of Mg2+ and Fe2+ ions, several hours after the beginning of the precipitation, partial dissolution of the product and modification of the crystals from needle‐ and plate‐like to agglomerated structures occurred. It is suggested that the secondary changes occur due to the increased concentration of Mg2+ and Fe2+ ions in the reactor. Below 60 °C, and above 70 °C plate‐like and needle‐like single crystals respectively were formed. The mean size (d50) of the crystals was found to increase with increasing temperature and decrease with the initial concentration of lime. Gypsum produced between 70 °C and 80 °C is suitable for further processing for construction plaster. In a precipitation process with pure sulfuric acid only single perfect needle‐like crystals occurred. Copyright © 2005 Society of Chemical Industry 相似文献
46.
47.
用化学还原法合成了FeBP非晶态合金超细微粒,用电感耦合等离子体光谱(ICP)、X射线粉末衍射(XRD)、透射电子显微镜(TEM)和差热分析(DSC)等手段对其进行了物性表征,并用微型催化反应装置考察了其对PH3分解的催化作用,结果表明,非晶态合金FeBP对PH3的分解具有良好的催化作用,能使PH3的分解温度从800℃以上降到500℃左右。490℃时分解率超过90%,540℃时达100%。 相似文献
48.
49.
In order to improve the physical properties and slag corrosion resistance of refractory materials for hot metal pretreatment, different contents of composite metal powders (CMP) were introduced into Al2O3-SiC-C refractory castables. The effect of CMP on the microstructure, physical properties and slag corrosion resistance of Al2O3-SiC-C refractory castables were studied. The results show that the multi scale reinforcing phases including flake crystals, rod shaped fibers, filamentous fibers and whiskers are in situ formed in the samples with addition of CMP, which result to the improvement of the cold modulus of rupture and cold crushing strength. When the addition of CMP is 6 wt.%, the high temperature modulus of rupture increases by 231%, the thermal shock resistance increases by 77% after thermal shock by water cooling 5 times and the percentage of the slag resistant area reduces by 37.2%. 相似文献
50.
分析了电石法PVC生产链中电石炉烟气及电厂烟气二氧化硫的排放情况,指出利用电石炉烟气中的CO合成氨、再将合成氨用于燃煤电厂烟气的"氨法"脱硫是具有较大应用潜力的循环经济产业链。 相似文献