全文获取类型
收费全文 | 29997篇 |
免费 | 2313篇 |
国内免费 | 1228篇 |
专业分类
电工技术 | 1657篇 |
综合类 | 2304篇 |
化学工业 | 5221篇 |
金属工艺 | 1415篇 |
机械仪表 | 1724篇 |
建筑科学 | 2073篇 |
矿业工程 | 726篇 |
能源动力 | 758篇 |
轻工业 | 2721篇 |
水利工程 | 636篇 |
石油天然气 | 1788篇 |
武器工业 | 213篇 |
无线电 | 3294篇 |
一般工业技术 | 3419篇 |
冶金工业 | 1244篇 |
原子能技术 | 364篇 |
自动化技术 | 3981篇 |
出版年
2024年 | 89篇 |
2023年 | 447篇 |
2022年 | 764篇 |
2021年 | 1120篇 |
2020年 | 867篇 |
2019年 | 719篇 |
2018年 | 781篇 |
2017年 | 949篇 |
2016年 | 819篇 |
2015年 | 1162篇 |
2014年 | 1497篇 |
2013年 | 1845篇 |
2012年 | 2060篇 |
2011年 | 2241篇 |
2010年 | 2056篇 |
2009年 | 1956篇 |
2008年 | 1951篇 |
2007年 | 1837篇 |
2006年 | 1798篇 |
2005年 | 1531篇 |
2004年 | 1081篇 |
2003年 | 824篇 |
2002年 | 749篇 |
2001年 | 597篇 |
2000年 | 609篇 |
1999年 | 599篇 |
1998年 | 477篇 |
1997年 | 405篇 |
1996年 | 390篇 |
1995年 | 309篇 |
1994年 | 244篇 |
1993年 | 189篇 |
1992年 | 150篇 |
1991年 | 118篇 |
1990年 | 60篇 |
1989年 | 67篇 |
1988年 | 64篇 |
1987年 | 27篇 |
1986年 | 27篇 |
1985年 | 20篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1959年 | 1篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
以MoCl3(OC8H17)2-(i-Bu)2AlOPhCH3为催化剂的丁二烯聚合反应,应用胶体的光学、电学、动力性质,对催化剂制备方法影响催化活性的原因进行了分析,得出〈Al〉/〈Mo〉比值影响催化剂颗粒大小,数密度及还原程度;混合顺序影响颗粒形态,固而影响催化活性。由于溶胶具有一定动力稳定性,所以陈化时间对催化活性影响较小。三元陈化加入低浓度的丁二烯,在陈化时能够发生聚合反应生成短链聚合物,阻碍了催化剂颗粒聚集,形成了细小的催化剂颗粒,提高了催化活性。 相似文献
993.
994.
对近年来一步法合成双乙酸钠的工艺研究进行了评述,指出醋酸一烧碱法因兼具经济及环境友好优势而最有工业化前景。 相似文献
995.
996.
A new type of modified bismaleimide resin was obtained by copolymerization between tris(allylphenoxy)triazine monomer (TAPT) and an aromatic diamine‐chain‐extension bismaleimide [e.g., 4,4′‐diaminodiphenylmethane (DADPM)‐chain‐extension 4,4′‐bismaleimidodiphenylmethane (BMDPM)]. The new three‐component‐polymer system had good processibility and mechanical properties. Better results were obtained when the weight ratio of TAPT to the DADPM‐chain‐extension BMDPM resin was 30%. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 475–480, 2004 相似文献
997.
A complex process of micro electrolysis and biofilm was developed to continuously treat organic wastew-aters containing heavy metal ions such as Cu^2 and Cr^3 ,and the relevant purifying mechanism was also addressed. In detail,organic materials in wastewater could be consumed as nutritious source by biofilm composed of aerobes and anaerobes,However,for heavy metal ions (Cu^2 ,Cr^3 ),part was removed by electrodeposition,and some was adorbed on biofilm.In order to compare with the combined process of micro electrolysis and biofilm,the experimental data of micro electrolysis process (intermittent )or biofilm process (continuous)were provided,and the kinetic data of C6H12O6(glucose)biodegradation by cultured microbes or acclimated microbes were also obtained,These experimental results indicated that for wastewater initially consisted of C6H12O6(500 mg.L^-1),Cu^2 and Cr^3 (10mg.L6-1),after treatment,its concentrations of C6H12O6,Cu^2 and Cr^3 were lowered to the leve of 55-65 mg.L^-1),after treatment,its concentrations of C6H12O6,Cu^2 and Cr^3 were lowered to the level of 55-65 mg.L^-1,and less than 1mg.L^-1,respectively,And the industrial reused water standards could be met by treated wastewater. 相似文献
998.
Vinyl ester resin is a major thermoset polymer used in low‐temperature composite manufacturing processes such as the Seemann composite resin infusion‐molding process (SCRIMP). Volume shrinkage and residual styrene are important concerns for composites produced in such processes. A low‐shrinkage additive (LSA) is a typical agent added to control the volume shrinkage of vinyl ester resins during molding. In this study, the effects of LSA content and the temperature profile (the temperature gradient and peak temperature) on the volume shrinkage control of a vinyl ester resin were investigated. The reaction kinetics of the resin system were also studied. We achieved good volume shrinkage control if we raised the curing temperature slowly to allow sufficient time for phase separation and if the curing temperature reached a high value after phase separation to allow microvoid formation. On the basis of experimental results, we designed an improved SCRIMP to increase resin conversion, reduce resin shrinkage, and produce composites with better properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1486–1496, 2003 相似文献
999.
1000.
The crystallization has significant influence on fluidity of slag and slag discharge of entrained-flow-bed(EFB) gasifier. The crystallization characteristics and fluidity of five synthetic slags with different MgO/CaO ratios prepared on the basis of the range of oxide contents of Zhundong coal ash were investigated in this study. The results show that with the MgO/CaO ratio increase, the initial crystallization temperature increases, and the main temperature range of crystallization ratio growth... 相似文献