全文获取类型
收费全文 | 2165篇 |
免费 | 56篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 4篇 |
技术理论 | 1篇 |
综合类 | 69篇 |
化学工业 | 1718篇 |
金属工艺 | 5篇 |
机械仪表 | 6篇 |
建筑科学 | 13篇 |
矿业工程 | 3篇 |
能源动力 | 7篇 |
轻工业 | 145篇 |
石油天然气 | 41篇 |
无线电 | 9篇 |
一般工业技术 | 204篇 |
冶金工业 | 2篇 |
原子能技术 | 10篇 |
自动化技术 | 5篇 |
出版年
2024年 | 12篇 |
2023年 | 20篇 |
2022年 | 39篇 |
2021年 | 49篇 |
2020年 | 39篇 |
2019年 | 28篇 |
2018年 | 23篇 |
2017年 | 42篇 |
2016年 | 59篇 |
2015年 | 54篇 |
2014年 | 58篇 |
2013年 | 111篇 |
2012年 | 112篇 |
2011年 | 108篇 |
2010年 | 86篇 |
2009年 | 104篇 |
2008年 | 93篇 |
2007年 | 114篇 |
2006年 | 151篇 |
2005年 | 140篇 |
2004年 | 135篇 |
2003年 | 103篇 |
2002年 | 83篇 |
2001年 | 77篇 |
2000年 | 67篇 |
1999年 | 81篇 |
1998年 | 59篇 |
1997年 | 31篇 |
1996年 | 23篇 |
1995年 | 20篇 |
1994年 | 20篇 |
1993年 | 16篇 |
1992年 | 15篇 |
1991年 | 12篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1985年 | 14篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 13篇 |
排序方式: 共有2242条查询结果,搜索用时 15 毫秒
21.
塑料在包装领域有着广泛的应用,其中聚酯(PET)性能优良,应用领域不断扩大。介绍了塑料包装不断通现的新技术,以及塑料包装环保问题的几点思路。 相似文献
22.
The α and β relaxation processes in two types of poly(ethylene terephthalate) with different degrees of crystallinity were studied by means of three methods, differential scanning calorimetry, dynamic-mechanical analysis and fluorescence spectroscopy. Information provided is complementary in the mean that every method sense phenomena that may occur at different times and length scales. Several probes, Coumarin 152 (C152), Coumarin 153 (C153), Coumarin 337 (C337) and 4′-dimethylamino-4-nitrostilbene (DMANS), were adsorbed in polymer films, and their fluorescence analysed over the temperature range from −150 to 150 °C. In general, a decrease in fluorescence intensity of probes as temperature increase was observed. This behaviour has been explained as a consequence of the enhancement of the free volume fraction that favoured the radiationless process of the lowest excited singlet state. Plots of fluorescence intensity versus temperature showed changes around the secondary relaxation temperatures. Therefore, good correlations between fluorescence and dynamic mechanical and calorimetric analysis were established. The obtained results indicated that the fluorescence from the probes incorporated to the material was dependent on the crystallinity of polymer. It would indicate that the fluorescence emission from those probes can be used to analyse annealing processes in semicrystalline polymers. 相似文献
23.
24.
PEN/PTT共混聚酯的熔融行为 总被引:1,自引:0,他引:1
利用差示扫描量热仪对不同配比的聚萘二甲酸乙二醇酯/聚对苯二甲酸丙二醇酯(PEN/PTT)共混体系的熔融行为进行了分析,发现在共混体系中两组分形成各自的晶体,PEN和PTT的熔点均随另一组分含量的增加而下降。根据Nishi-Wang方程,按300℃计算,由PEN/PTT共混体系中PEN熔点下降计算所得到的相互作用能密度为-0.214 2 J/cm~3,相互作用参数为-0.006 8,表明PEN/PTY共混体系在熔融态是热力学性质稳定的相容体系。 相似文献
25.
Richard Kotek Dong‐Wook Jung Joon Ho Kim Brent Smith Patricia Guzman Benjamin Schmidt 《应用聚合物科学杂志》2004,92(3):1724-1730
The surface alkaline hydrolysis of fibers made from poly(trimethylene terephthalate) (PTT) was studied after extruding the polymer at high spinning speeds from 2000 to 6000 m/min and heat setting in the range of temperatures from 100 to 180°C. Fiber weight loss increased with an increasing heat‐setting temperature but it was also dependent on the spinning speed. Some of the partially hydrolyzed fibers had a well‐developed, hydrophilic surface, and pore size in the range of 0.69 to 1.20 μm. The optimum reaction and morphological conditions for increasing porosity in PTT fibers depends on spinning speed and heat‐setting temperature. A temperature of 180°C is the upper limit for heat‐setting PTT filaments but seems to be the most effective for making porous fibers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1724–1730, 2004 相似文献
26.
In this study, poly(ethylene terephthalate) (PET)/SiO2 nanocomposites were synthesized by in situ polymerization and melt‐spun to fibers. The superfine structure, physical properties, and dyeability of alkaline hydrolyzed PET/SiO2 nanocomposite fibers were studied. According to the TEM, SiO2 nanoparticles were well dispersed in the PET matrix at a size level of 10–20 nm. PET/SiO2 nanocomposite fibers were treated with aqueous solution of sodium hydroxide and cetyltrimethyl ammonium bromide at 100°C for different time. The differences in the alkaline hydrolysis mechanism between pure PET and PET/SiO2 nanocomposite fibers were preliminarily investigated, which were evaluated in terms of the weight loss, tensile strength, specific surface area, as well as disperse dye uptake. PET/SiO2 nanocomposite fibers showed a greater degree of weight loss as compared with that of pure PET fibers. More and tougher superfine structures, such as cracks, craters, and cavities, were introduced, which would facilitate the certain application like deep dyeing. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3691–3697, 2006 相似文献
27.
A ArósteguiJ Nazábal 《Polymer》2003,44(1):239-249
New super-tough poly(butylene terephthalate) (PBT) materials were obtained by melt blending PBT with both 20 wt% phenoxy (Ph) and 0-30 wt% maleic anhydride grafted poly(ethylene-octene) (mPEO) copolymers with different grafting levels. Ph was completely miscible in the PBT matrix. The presence of mPEO did not influence either the nature of the PBT-Ph matrix or the crystallization of PBT. The overall decrease in particle size and in interfacial tension upon grafting indicated that compatibilization had taken place. Super-tough (impact strength 23-fold that of the PBT) and stiffer PBT based blends were obtained at mPEO contents equal to or higher than 15%. The dependence of the critical inter-particle distance (τc), on both adhesion measured by means of the interfacial tension, and on the relation between the modulus of the matrix and that of the rubbery dispersed phase (Em/Ed), is proposed. 相似文献
28.
介绍了国内外废旧PET瓶通过物理或化学回收方法制取再生薄片、粒料、纤维、片材、泡沫塑料、复合材料、涂料等的应用进展;另外,对于闭环循环的PET“瓶-瓶”回收工艺技术进行了专门介绍。 相似文献
29.
采用双螺杆挤出机制备了聚丙烯(PP)/回收聚对苯二甲酸乙二酯(r-PET)、r-PET/马来酸酐接枝PP(PP-g-MAH)和r-PET/甲基丙烯酸缩水甘油酯接枝PP(PP-g-GMA)共混物,并研究了共混物组成、熔融温度与时间以及降温速率对共混物非等温结晶与熔融行为的影响.结果表明,r-PET与PP共混,结晶温度均提高,这与组分间起到异相成核诱导结晶作用有关.r-PET结晶温度随PP-g-MAH用量增加而降低,但受PP-g-GMA用量影响较小;r-PET可提高PP-g-MAH结晶温度,但降低PP-g-GMA结晶温度.熔融温度提高,共混物中PP结晶温度和熔点均降低,r-PET熔融峰形和熔点取决于共混物的熔融温度及界面相互作用. 相似文献
30.
以乙烯-丙烯酸丁酯-甲基丙烯酸缩水甘油酯三元共聚物(PTW)作为高密度聚乙烯(PE-HD)/聚对苯二甲酸乙二醇酯(PET)共混合金的反应性相容剂,采用熔融挤出法制备了以PE-HD为基体的PE~Hi)/PET、共混合金。通过力学性能和流变性能测试,扫描电镜(SEM)和动态力学分析(DMA)等手段,研究丁PTW对共混合金性能的影响。结果表明:PTW提高了体系的综合性能,当PE-HD/PET配比为90/10,PTW含量在5份时,其缺口冲击强度提高了近400%,拉伸强度和断裂伸长率分别提高了25%和50%,同时改善了共混合金的加工性能。SEM分析表明PTW的加入增大了共混合金的界面相互作用,促进了分散相粒子的细化,从而提高丁体系相容性,DMA测试表明,PTW的加入使PET的玻璃化转变温度向PE—HD的玻璃化转变温度靠近: 相似文献