全文获取类型
收费全文 | 28052篇 |
免费 | 2890篇 |
国内免费 | 929篇 |
专业分类
电工技术 | 306篇 |
综合类 | 2176篇 |
化学工业 | 7271篇 |
金属工艺 | 4080篇 |
机械仪表 | 645篇 |
建筑科学 | 4580篇 |
矿业工程 | 1435篇 |
能源动力 | 393篇 |
轻工业 | 257篇 |
水利工程 | 505篇 |
石油天然气 | 1355篇 |
武器工业 | 72篇 |
无线电 | 353篇 |
一般工业技术 | 2948篇 |
冶金工业 | 5228篇 |
原子能技术 | 134篇 |
自动化技术 | 133篇 |
出版年
2024年 | 168篇 |
2023年 | 449篇 |
2022年 | 893篇 |
2021年 | 928篇 |
2020年 | 999篇 |
2019年 | 713篇 |
2018年 | 793篇 |
2017年 | 1133篇 |
2016年 | 1049篇 |
2015年 | 1143篇 |
2014年 | 1763篇 |
2013年 | 1476篇 |
2012年 | 1861篇 |
2011年 | 1946篇 |
2010年 | 1483篇 |
2009年 | 1539篇 |
2008年 | 1169篇 |
2007年 | 1860篇 |
2006年 | 1714篇 |
2005年 | 1498篇 |
2004年 | 1302篇 |
2003年 | 1062篇 |
2002年 | 917篇 |
2001年 | 784篇 |
2000年 | 647篇 |
1999年 | 524篇 |
1998年 | 431篇 |
1997年 | 333篇 |
1996年 | 276篇 |
1995年 | 208篇 |
1994年 | 201篇 |
1993年 | 129篇 |
1992年 | 117篇 |
1991年 | 75篇 |
1990年 | 95篇 |
1989年 | 68篇 |
1988年 | 32篇 |
1987年 | 18篇 |
1986年 | 13篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1976年 | 4篇 |
1975年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
《中国耐火材料》2012,(2)
Six kinds of Cr2O3 Al2O3 fused grains ( the mass percent of Cr2O3 was 15% ,40% ,50% ,60% ,85% and 99% ,respectively) were prepared using chrome green and Al2O3 powder as starting materials by electrofusion,named as CR15,CR40,CR50,CR60,CR85, and CR99,respectively. The corrosion resistance of the six kinds of Cr2O3 Al2O3 fused grains ( 4 1 mm) was studied using rotary slag corrosion method. The results show that: ( 1) the corrosion resistance of the fused grains increases with the Cr2O3 content and the grain size increasing; ( 2) the grains of CR99 and CR85 with higher Cr2O3 content are corroded at the slag surface layer,because FeO and Al2O3 in the slag corrode the grains; FeO reacts with Cr2O3 in the aggregates forming ( Fe,Cr) 3O4 spinel firstly,and the spinel reacts with other phases forming composite spinel; when FeO is fully consumed,Al2O3 penetrated into the grains reacts with Cr2O3 forming Al2O3 Cr2O3 solid solution on the grains surface; ( 3) for CR60,the corrosion exists both in the slag surface layer and in the penetration layer; in the penetration layer,CaO and SiO2 react with Al2O3 in Al2O3 Cr2O3 solid solution forming anorthite, gehlenite, and glass phase; the grains of CR50,CR40 and CR15 have the same corrosion mechanism with CR60 in the penetration layer. 相似文献
992.
A copolymer comprising of 2‐acrylamido‐2‐methyl propane sulfonic acid (AMPS®) and itaconic acid (molar ratio 1 : 0.32) was synthesized by aqueous free radical polymerization and probed as high temperature retarder for oil well cement. Characteristic properties of the copolymer including molar masses (Mw and Mn), polydispersity index and anionic charge amount were determined. The copolymer possesses a Mw of ~ 2 × 105 g/mol and is highly anionic. HT/HP consistometer tests confirmed effectiveness of the retarder at temperatures up to 200°C. The working mechanism of NaAMPS®‐co‐itaconic acid was found to rely exclusively on its huge calcium binding capacity (5 g calcium/g copolymer). It reduces the amount of freely dissolved, nonbound calcium ions present in cement pore solution and thus hinders the growth of cement hydrates because of lack of calcium. The value for the calcium binding capability is 46 times higher than the stoichiometric amount per ? COO? functionality. Consequently, calcium also coordinates to other donor atoms present in the retarder. NaAMPS®‐co‐itaconic acid also adsorbs onto cement, as was evidenced by TOC analysis of cement filtrates, zeta potential measurement and decreased rheology of cement pastes. However, adsorption plays no role in the retarding mechanism of this copolymer. Combination of NaAMPS®‐co‐itaconic acid retarder with a common CaAMPS®‐co‐NNDMA fluid loss additive (FLA) revealed that competitive adsorption on cement between these two admixtures occurs. The retarder fills interstitial adsorption sites on cement located between those occupied by the larger FLA molecules. In consequence, fewer amounts of CaAMPS®‐co‐NNDMA can adsorb and its effectiveness is reduced. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
993.
《国际聚合物材料杂志》2012,61(8):591-602
Nano-sized TiO2 was successfully synthesized and deposited onto wool fibers using the sol–gel process at ambient temperature. The prepared samples were characterized using several structural, textural, and morphological techniques. The electron micrographs show formation of TiO2 nanoparticles 10–30 nm in size. The photocatalytic activity of TiO2-coated wool fibers was investigated through the solid-phase self-cleaning of methylene blue (MB) under UV-vis irradiation by the diffuse reflectance spectroscopy (DRS) method. The fibers' structure is not altered upon light exposure. This preparation technique can also be applied to new fabrics to create self-cleaning and UV irradiation protection properties in them. 相似文献
994.
995.
996.
997.
998.
磷矿渣用于陶瓷坯料试验研究 总被引:2,自引:0,他引:2
磷矿渣作为工业废料,其合理利用极具经济价值,根据其组成特点,适当配合其它原料,经试验证明,完全可以用于陶瓷产品的坯料配制,再配以高强乳浊釉对有色坯体进行有效的遮盖,则可以生产出各项性能指标符合要求的釉面砖制品。 相似文献
999.
论述了运用一氧化二氮 -乙炔火焰原子吸收光谱法测定 771 5 D高温钛合金中的铝含量。介绍了铝的最佳测定条件及呈良好线性范围的浓度 ,并对样品消化处理条件、干扰因素进行了综合考虑。该方法灵敏度高 ,干扰小 ,选择性和重现性好。同时具有方法步骤简单、操作容易掌握、分析周期短等优点。对样品进行 6次测定的结果表明 ,相对标准偏差均小于 1 .0 % ;标准加入回收率均在97%~ 1 0 2 %范围内。完全适用于实验室质量控制的要求。同时提供了一种非常实用的仪器分析方法 相似文献
1000.
固相法合成La2 O3 TiO3 系陶瓷介质材料 ,XRD、SEM、EDS分析其结构、形貌和成分。高精度电容测量仪测试其介电性能。La2 O3/TiO2 比 1∶2、2∶9组分可获得极低介质损耗 ,XRD分析主晶相为La2 Ti2 O7和La4 Ti9O2 4 。La2 O3/TiO2 比 1∶3组分可获得La2 / 3TiO3、La4 Ti9O2 4 复相。缺陷型钙钛矿相La2 / 3TiO3不利于介质损耗降低。EDS分析表明晶界富集Si杂质 ,有效促进了液相烧结 相似文献