全文获取类型
收费全文 | 691篇 |
免费 | 35篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 8篇 |
综合类 | 34篇 |
化学工业 | 441篇 |
金属工艺 | 1篇 |
机械仪表 | 5篇 |
建筑科学 | 2篇 |
能源动力 | 4篇 |
轻工业 | 106篇 |
石油天然气 | 51篇 |
武器工业 | 1篇 |
无线电 | 8篇 |
一般工业技术 | 44篇 |
冶金工业 | 19篇 |
自动化技术 | 8篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 9篇 |
2019年 | 9篇 |
2018年 | 14篇 |
2017年 | 14篇 |
2016年 | 14篇 |
2015年 | 17篇 |
2014年 | 26篇 |
2013年 | 42篇 |
2012年 | 52篇 |
2011年 | 51篇 |
2010年 | 45篇 |
2009年 | 40篇 |
2008年 | 30篇 |
2007年 | 50篇 |
2006年 | 43篇 |
2005年 | 44篇 |
2004年 | 26篇 |
2003年 | 25篇 |
2002年 | 26篇 |
2001年 | 29篇 |
2000年 | 25篇 |
1999年 | 19篇 |
1998年 | 7篇 |
1997年 | 13篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 9篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
排序方式: 共有732条查询结果,搜索用时 15 毫秒
681.
双(对-羧苯基)苯基氧化膦(BCPPO)具有较高的热稳定性、氧化稳定性和耐水解性,是一种有很好发展前景的阻燃剂。阐述了BCPPO的阻燃机理;通过分析不同研究者制备BCPPO的合成工艺,客观评述了各种工艺的特点;并全面介绍了BCPPO在高分子材料领域中的应用;对今后BCPPO的研究提出了一些建议。 相似文献
682.
683.
Poly(N‐phenyl acrylamide) (PPA) and poly(N‐phenyl methacrylamide) (PPMA) were prepared by using N‐phenyl acrylamide and N‐phenyl methacrylamide as monomer, respectively, in tetrahydrofuran using azobisisobutyronitrile as initiator. FT‐IR, 1H‐NMR, and GPC were used to characterize their molecular structure. The PPA obtained exhibited higher molecular weight and wider molecular weight distribution than that of PPMA. Their thermal degradation and kinetics were systematically investigated in two atmospheres of nitrogen and air from room temperature to 800°C by thermogravimetric analysis at 10°C/min. Based on the thermal decomposition reactions in nitrogen and air, it is shown that a three‐step degradation process in nitrogen and a four‐step degradation process for two polymers were observed in this investigation. The initial thermal degradation temperature was lower than 190°C. Under two atmospheres, PPA exhibits higher degradation temperature, higher temperature at the maximum weight‐loss rate, faster maximum weight‐loss rates, and larger weight loss for the first‐stage decomposition, as well as higher char yield at 500°C than those of PPMA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1065–1071, 2003 相似文献
684.
Lara Finelli Cesare Lorenzetti Massimo Messori Laura Sisti Micaela Vannini 《应用聚合物科学杂志》2004,91(3):1887-1892
The miscibility behavior of poly(vinyl phenyl ketone hydrogenated) (PVPhKH) and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) are studied by differential scanning calorimetry, thermomechanical analysis, and FTIR spectroscopy. Two miscibility windows between 10 to 40 and 60 to 90 wt % PPO are detected. Only the blend with 50 wt % PPO is immiscible. The best fit of the Gordon–Taylor equation of the experimental glass‐transition temperatures for miscible PVPhKH/PPO blends is shown. A study by FTIR spectroscopy suggests that hydrogen bonding interactions are formed between the hydroxyl groups of PVPhKH and the ether groups of PPO. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1887–1892, 2004 相似文献
685.
以乙酰甘氨酸和苯甲醛及其衍生物为原料,合成了一系列含碳碳双键的前手性底物,(Z)-2-乙酰氨基苯丙烯酸,(Z)-2-乙酰氨基-3-(对甲氧苯基)-丙烯酸,(Z)-2-乙酰氨基-3-(对氯苯基)-丙烯酸,(Z)-2-乙酰氨基-3-(间氯苯基)-丙烯酸,(Z)-2-乙酰氨基-3-(间硝基苯基)-丙烯酸。后4种是新的有机化合物,产物结构经过核磁共振,质谱分析确证。 相似文献
686.
合成了乙炔基苯基偶氮酚醛树脂(EPAN),通过溶液共混的方法用其对含硅芳炔树脂(PSA)进行改性,研究了PSA-EPAN树脂的热性能,并制备了PSA-EPAN的碳布预浸料,经热模压制备碳纤维布(T300CF)增强PSA-EPAN复合材料,对其力学性能进行了研究。结果表明:EPAN均匀分布于PSA树脂中,EPAN共混改性PSA树脂的固化温度提高,混入质量分数为7%的EPAN,N2中固化PSA-EPAN树脂在800℃残留率超过90%,其玻璃化转变温度高于500℃,PSA-EPAN共混树脂浇铸体的弯曲性能高于PSA树脂,达40.7 MPa,提高了95.5%;PSA树脂经T300CF/PSA-EPAN复合材料力学性能显著提高,弯曲强度达到了423.5 MPa,提高了74%,层间剪切强度(ILSS)提高至29.53 MPa,增加了65%。 相似文献
687.
以4-氯代邻苯二甲酸酐(4-CPA)和双酚A为主要原料,经缩合、水解、酸化、脱水,合成了双酚A型二醚二酐(BPADA),并用核磁共振氢谱和红外光谱对产物的结构进行了表征。利用差示扫描量热分析和动态力学分析方法研究了BPADA作为E-51环氧树脂的固化剂并与邻苯二甲酸酐(PA)进行了比较,考察了2种固化体系所得产物的力学性能。结果表明,采用四步法成功合成出了BPADA,2种体系的固化反应活化能和反应级数相近,但BPADA体系活化能稍高于PA体系,且PA体系具有更高的反应速率。BPADA体系固化物的Tg比PA体系提高了40℃。相比PA体系,BPADA体系的冲击强度提高了35%,而弯曲性能略有下降,E-51/BPADA固化体系的冲击断面呈典型的韧性断裂,而E-51/PA固化体系呈典型的脆性断裂。 相似文献
688.
Ti—PF—Tween80光度法测定钨精矿中微量钛 总被引:1,自引:0,他引:1
本文提出在非离子表面活性剂聚乙烯醇(PVA)—Tween80存在下,以苯基萤光酮(PF)为显色剂测定微量钛,其灵敏度较高,摩尔吸光系数ε_(535)=1.91×10~5L·mol~(-1)·cm~(-1),可与取代苯基萤光酮显色媲美,应用于钨精矿中微量钛的测定,回收率为97~101%,结果令人满意。 相似文献
689.
The alternating copolymerization of N‐phenyl maleimide (NPMI) with ethyl α‐ethylacrylate (EEA) by the reversible addition fragmentation chain‐transfer process was investigated. The monomer reactivity ratios were measured and r1 = 0.19 ± 0.03 for NPMI and r2 = 0.20 ± 0.04 for EEA. It was found that before about 45% of the comonomer conversion, the molecular weight of the copolymer increased with the conversion, the molecular weight distribution was rather narrow, and the molecular weight of the copolymer approached a constant value, irrespective of the length of the polymerization time. Electronic spin resonance determined that the radical signal disappeared quickly after the conversion of comonomer exceeded 45%, which may be attributed to the coupling termination of the propagating polymer chains with the EEA end with the intermediate radicals when the concentration of comonomers decreased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2376–2382, 2004 相似文献
690.
A semicrystalline polymer, isotactic poly(phenyl glycidyl ether) (i‐PPGE) was used as a modifier for epoxy resin; 1,8‐Diamino‐p‐methane (MNDA) and 4,4′‐Diamino diphenyl sulfone (DDS) were used as curing agents. In the MNDA‐cured resins, the dispersed phase were spherical particles with diameters in the range of 0.5–1.0 μm when the resin was blended with 5 phr i‐PPGE. In the DDS‐cured resins, the particle size distribution of the dispersed phase was much wider. The difference was traced back to the reactivity of the curing agent and the different regimes used for curing. Through dynamic mechanical analysis, it was found that in the MNDA‐cured systems, i‐PPGE had a lower crystallinity than in the DDS‐cured system. In spite of the remarkable difference in the morphology and microstructure of the modified resins cured with these two curing agents, the toughening effects of i‐PPGE were similar for these resins. The critical stress intensity factor (KIC) was increased by 54% and 53%, respectively, for the resins cured by DDS and by MNDA, blending with 5 phr of the toughner. i‐PPGE was comparable with the classical toughners carboxyl‐terminated butadiene‐acrylonitrile copolymers in effectiveness of toughening the epoxy resin. An advantage of i‐PPGE was that the modulus and the glass‐transition temperature of the resin were less affected. However, this modifier caused the flexural strength to decrease somewhat. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1223–1232, 2002; DOI 10.1002/app.10445 相似文献