全文获取类型
收费全文 | 30346篇 |
免费 | 1427篇 |
国内免费 | 1109篇 |
专业分类
电工技术 | 682篇 |
技术理论 | 1篇 |
综合类 | 1388篇 |
化学工业 | 7605篇 |
金属工艺 | 2361篇 |
机械仪表 | 674篇 |
建筑科学 | 1228篇 |
矿业工程 | 530篇 |
能源动力 | 1801篇 |
轻工业 | 618篇 |
水利工程 | 192篇 |
石油天然气 | 4257篇 |
武器工业 | 39篇 |
无线电 | 342篇 |
一般工业技术 | 1766篇 |
冶金工业 | 8571篇 |
原子能技术 | 118篇 |
自动化技术 | 709篇 |
出版年
2024年 | 48篇 |
2023年 | 192篇 |
2022年 | 483篇 |
2021年 | 560篇 |
2020年 | 625篇 |
2019年 | 507篇 |
2018年 | 488篇 |
2017年 | 631篇 |
2016年 | 815篇 |
2015年 | 779篇 |
2014年 | 1717篇 |
2013年 | 1541篇 |
2012年 | 1952篇 |
2011年 | 2061篇 |
2010年 | 1568篇 |
2009年 | 1581篇 |
2008年 | 1228篇 |
2007年 | 1837篇 |
2006年 | 1852篇 |
2005年 | 1775篇 |
2004年 | 1490篇 |
2003年 | 1463篇 |
2002年 | 1258篇 |
2001年 | 1132篇 |
2000年 | 982篇 |
1999年 | 952篇 |
1998年 | 675篇 |
1997年 | 614篇 |
1996年 | 464篇 |
1995年 | 424篇 |
1994年 | 332篇 |
1993年 | 207篇 |
1992年 | 167篇 |
1991年 | 128篇 |
1990年 | 95篇 |
1989年 | 79篇 |
1988年 | 45篇 |
1987年 | 21篇 |
1986年 | 15篇 |
1985年 | 22篇 |
1984年 | 17篇 |
1983年 | 14篇 |
1982年 | 24篇 |
1981年 | 3篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977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 0 毫秒
111.
Xinsheng Zhu Hansong Xu Jianmei Lu Juying Wang Shunhua Zhou 《Journal of Polymer Research》2008,15(4):295-300
Poly(ethylene terephthalate) (PET) is of excellent mechanical properties and melt processability and is widely used as raw
material for textile fibers. However, the flame retardant properties of PET were rather poor, and both reactive and additive
phosphorus- and halogen-containing compounds have been employed to enhance the reaction-to-fire properties while the meltdripping
behaviour during burning hasn’t been handled properly with the flame retardants. In this work, fluoropolymer was blended with
both pure PET (pPET) and reactive phosphorus-containing flame retarded copolyester (fPET), and the flame retardance and char
formation and mechanical properties of the resulted pPET and fPET blends were investigated. The tensile strengths of modified
pPET samples were worsen whereas those of modified fPET samples were improved at low concentrations. The initial thermal degradation
in nitrogen was accelerated remarkably for the two polyesters with fluoropolymer. The oxygen indices of the all modified samples
were reduced while char formation and meltdripping suppression were encouraged. The apparent melt viscosity and elasticity
for the two polyesters were gained much with antidripping agent. Therefore, fluoropolymer improved char formation of the two
polyesters based on the gaseous phase mechanism while the partial suppression of meltdripping behavior and the decrease of
mechanical properties mainly originated from the increase of melt viscosity via fibrillation for pPET. 相似文献
112.
大庆蜡油在酸性催化剂上反应机理的研究 总被引:11,自引:5,他引:6
以大庆蜡油为原料,采用两种不同类型的催化剂,在流化床反应器实验装鬣上进行催化裂化反应。结果表明,大庆蜡油在酸性催化剂上反应所产生的干气组成与高烯烃催化裂化汽油相同,干气的产生主要是单分子裂化反应所造成的。从干气产率、组成以及液化气组成可以看出,大庆蜡油在不同类型的催化剂上明显地表现出裂化反应类型的差异。 相似文献
113.
M.S. Thompson Author Vitae Author Vitae 《Polymer》2008,49(2):345-373
Poly(ethylene oxide) (PEO) oligomers are employed extensively in pharmaceutical and biomedical arenas mainly due to their excellent physical and biological properties, including solubility in water and organic solvents, lack of toxicity, and absence of immunogenicity. PEO can be chemically modified and reacted with, or adsorbed onto, other molecules and surfaces. Sophisticated applications for PEO have increased the demand for PEO oligomers with tailored functionalities, and heterobifunctional PEOs are often needed. This review discusses the synthesis and applications of heterobifunctional PEO oligomers possessing amine, carboxylate, thiol, and maleimide functional groups. 相似文献
114.
世界乙烯工业及其进展 总被引:9,自引:3,他引:6
阐述了世界乙烯产能需求现状,近扑扩能增产预测,乙烯原料分析以及乙烯生产的技术进展。 相似文献
115.
117.
118.
119.
以塔河减压渣油(简称塔河减渣)为原料,在实验室小型试验装置和中型连续试验装置上,对在较高温度条件下催化临氢热转化加工塔河减渣的工艺操作条件及改质效果进行了系统研究。采用高分散的油溶性催化剂,在高压釜反应器中考察了反应温度、反应压力、催化剂添加量、溶剂油添加量、反应时间以及助剂添加量对塔河减渣催化临氢热转化反应的转化率和缩合率的影响,优化了操作参数。在优化的操作条件下,进行了塔河减渣催化临氢热转化中型试验,得到初馏点大于524 ℃组分的裂化率为85.2%,馏分油收率为80%,金属(Ni+V)和沥青质脱除率均大于90%。 相似文献
120.
Synthesis and characterization of acidic properties of Al-SBA-15 materials with varying Si/Al ratios
G. Muthu Kumaran Shelu Garg Kapil Soni Manoj Kumar J.K. Gupta L.D. Sharma K.S. Rama Rao G. Murali Dhar 《Microporous and mesoporous materials》2008,114(1-3):103-109
Al-SBA-15 of varying Si/Al ratios in the range 11.4–78.4 was synthesized using tri-block copolymer P123. The calcined materials were examined by XRD, pore size distribution, surface area, 27Al NMR spectroscopy. The acidity and acid strength distribution were studied using microcalorimetric adsorption of NH3. The acidic properties were also examined by cumene cracking reaction as a function of Si/Al ratios. Systematic variation of acidity and activity was observed as a function of Si/Al ratio. The initial heats of NH3 adsorption correlated well with activity indicate that acid sites with ΔH > 100 kJ/mole is responsible for cumene cracking activity. Linear correlations were obtained with total acidity and cumene cracking activities. The tetrahedral aluminum was found to be responsible for the observed acidities and catalytic activities. 相似文献