全文获取类型
收费全文 | 1936篇 |
免费 | 88篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 15篇 |
综合类 | 57篇 |
化学工业 | 1298篇 |
金属工艺 | 16篇 |
机械仪表 | 25篇 |
建筑科学 | 4篇 |
矿业工程 | 4篇 |
能源动力 | 1篇 |
轻工业 | 362篇 |
石油天然气 | 17篇 |
武器工业 | 2篇 |
无线电 | 10篇 |
一般工业技术 | 218篇 |
冶金工业 | 2篇 |
原子能技术 | 5篇 |
自动化技术 | 8篇 |
出版年
2024年 | 8篇 |
2023年 | 23篇 |
2022年 | 40篇 |
2021年 | 72篇 |
2020年 | 53篇 |
2019年 | 55篇 |
2018年 | 50篇 |
2017年 | 61篇 |
2016年 | 60篇 |
2015年 | 60篇 |
2014年 | 53篇 |
2013年 | 100篇 |
2012年 | 141篇 |
2011年 | 124篇 |
2010年 | 102篇 |
2009年 | 97篇 |
2008年 | 71篇 |
2007年 | 115篇 |
2006年 | 126篇 |
2005年 | 121篇 |
2004年 | 76篇 |
2003年 | 70篇 |
2002年 | 62篇 |
2001年 | 62篇 |
2000年 | 54篇 |
1999年 | 47篇 |
1998年 | 29篇 |
1997年 | 26篇 |
1996年 | 17篇 |
1995年 | 12篇 |
1994年 | 16篇 |
1993年 | 11篇 |
1992年 | 13篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1977年 | 1篇 |
排序方式: 共有2044条查询结果,搜索用时 13 毫秒
101.
分别研究了在湿热老化、加速湿热老化、紫外辐照老化模式下,背板的力学性能和聚酰胺熔融焓及黄度指数的变化,分析了老化前后背板的断面形貌和表面形貌变化。结果表明:湿热老化和加速湿热老化聚酰胺趋于结晶以及聚酰胺和玻璃纤维界面作用减弱;紫外辐射老化主要导致酰胺键断开,分子结构破坏。通过比较老化前后力学性能、黄度指数及表面形貌发现,紫外辐照老化对聚酰胺背板的影响较大。 相似文献
102.
采用双螺杆挤出机制备聚酰胺66(PA66)/碳纤维/玻璃纤维材料和PA66/碳纤维材料,另外加入相容剂马来酸酐接枝聚烯烃弹性体(POE–g–MAH)来改善相界面的相容性,同时评价其力学性能和摩擦磨损性能。结果表明:在碳纤维增强PA66材料的研究过程中引入玻璃纤维可降低最高界面温度并且使摩擦系数降低,有助于改善PA66材料的摩擦学性能,共混物的摩擦过程以磨粒磨损和粘着磨损为主。此外,在添加入玻璃纤维后,15%混杂纤维填充比15%碳纤维单独填充的PA66材料拉伸强度提高9.89%,冲击强度提高34.02%;而添加入20%混杂纤维与20%碳纤维单独填充的PA66材料相比,拉伸强度提高了71.65%,冲击强度提高了26.23%。 相似文献
103.
以二聚脂肪酸、二乙烯三胺、尿素等为原料制备室温自修复型聚酰胺。通过溶液水热法制备导电单质钴颗粒,并采用纳米复合工艺将导电单质钴颗粒掺杂入自修复聚酰胺体系中,经高温模压制得一种新型钴基自修复聚酰胺导电高分子材料。采用傅里叶变换红外光谱仪、X射线衍射仪、扫描电子显微镜等仪器对单质钴和自修复聚酰胺进行结构表征。系统研究了自修复聚酰胺的自修复能力及抗溶胀性能,以及自修复导电高分子材料的导电和自修复性能。结果表明,所制备的单质钴平均粒径为3.43μm,且表面粗糙易于与聚酰胺基体复合;自修复聚酰胺基体在室温下的自修复次数可达20余次;当交联剂尿素用量为6.6 g/20 g二聚脂肪酸或交联温度为145℃时,自修复聚酰胺对水、碱溶液和油具有较好的综合抗溶胀性能。当单质钴质量分数达到50%后,自修复导电高分子材料的导电率发生突变,导电能力大幅提升;单质钴的加入降低了材料的自修复能力,但单质钴质量分数为50%的材料在室温下的自修复次数仍可达10余次。由于这种材料同时具有较好的导电性能和自修复性能,有望应用于可穿戴装备、电子器件等领域。 相似文献
104.
New amide–acid functional SiO2 nanoparticle (FSNP)‐reinforced semi‐crystalline aliphatic–aromatic poly(ether‐sulfone‐amide) (PESA) was synthesized using a solution method in dimethylformamide. The surfaces of SiO2 nanoparticles were functionalized with phthalic anhydride, and subsequently PESA was synthesized using direct polymerization with good yield and desired molar mass. PESA / SiO2 nanocomposites (PSNCs) were prepared with three different contents of FSNP and the morphology and mechanical, thermal and combustion properties of the PSNCs were studied. The results of X‐ray diffraction, field‐emission scanning electron microscopy and transmission electron microscopy showed a uniform dispersion for FSNP in the PESA matrix. According to the results of mechanical tests, the tensile strength and the Young's modulus of PESA were enhanced by FSNP loading. Thermogravimetric analysis and derivative thermogravimetry results showed a substantial improvement in thermal properties of PESA. The temperature at 5% mass loss was increased from 371.7 to 395.8 °C for the PSNC containing 8 mass% of FSNP, as well as the char yield being enhanced greatly, which was about 30% higher than that of neat PESA. Significant improvements in combustion properties were observed for PSNCs from microscale combustion calorimetry. The peak heat release rate showed an obvious improvement and decreased by about 57% compared to that of neat PESA on 8 mass% loading of FSNP. © 2016 Society of Chemical Industry 相似文献
105.
Weibo Kong Yunyun Yang Zhimeng Liu Liang Jiang Changlin Zhou Jingxin Lei 《Polymer International》2017,66(3):436-442
A series of poly(urethane‐urea‐amide) thermoplastic elastomers (PUUAs) based on polytetrahydrofuran (polytetramethylene glycol, PTMG), nylon‐6 and 4,4′‐diphenylmethane diisocyanate were synthesized through reactive processing. This method solved the incompatibility of nylon‐6 and PTMG, and these model elastomers were used to gain insight into the structure–property relations of block polymers. The target products were solvent resistant, transparent and melting‐processable. Fourier transform infrared spectroscopy, XRD, DSC, TEM, dynamic mechanical analysis, tensile testing and TGA were used to study the structure, crystallization, morphology, mechanical properties and thermostability of the PUUAs. The Fourier transform infrared results proved the successful preparation of PUUAs from nylon‐6 and PTMG. TEM examination showed that all samples exhibit microphase separated morphology with the nylon‐6 domain dispersed in the PTMG phase. The results of tensile testing indicated that the elastomers exhibit excellent mechanical properties with stress at break and strain at break exceeding 40 MPa and 600% respectively. The TGA results implied that the PUUAs can be fabricated by transitional processing at proper temperature without any thermodegradation. These favorable features were related to the microphase separated structure of the PUUAs. © 2016 Society of Chemical Industry 相似文献
106.
107.
108.
109.
通过熔融纺丝法制备了系列聚酰胺6/黏土/聚乙二醇(PTFs)共混调温纤维,并采用傅里叶红外光谱仪、差示扫描量热仪、热红外成像仪、热失重分析仪和复丝强力仪测试了纤维的结构、热性能、调温性能和力学性能。研究显示,PTFs调温纤维的结晶温度为33℃,结晶焓值达到8.46 J/g,且在100次升降温热循环后调温纤维仍保持良好的热性能。通过模拟冷热环境交替下纤维的温度—时间响应行为发现,在热环境(90℃)和冷环境(10℃)下,调温纤维体现出明显的温度滞后响应,与纯PA6纤维相比温差达到3℃。黏土/聚乙二醇在纤维中的最大质量分数为15%,在牵伸4倍时,纤维的拉伸断裂强度达到3.15 cN/dtex。 相似文献
110.
Sara Asghari Mooneghi Ali Akbar Gharehaghaji Hossein Hosseini-Toudeshky Giti Torkaman 《应用聚合物科学杂志》2019,136(11):47206
The wicking phenomenon is of prime importance with regards to biomedical applications of nanofiber yarns such as suture yarns and tissue scaffolds. In such applications, the yarns are usually subjected to cyclic tensile forces and biological tensile stresses. There is a lack of science behind the effect of fatigue on wicking properties of nanofiber yarns and this work aims at exploring this venue. Wicking properties of polyamide 66 nanofiber yarns are investigated by tracing the color change in the yarn structure resulting from pH changes during the capillary rise of distilled water. Results show that applying cyclic loading increases equilibrium wicking height in the Lucus–Washburn equation, which is attributed to changes in the overall pore structure in the cyclic loaded yarn. The likely causes of these changes are studied by scanning electron microscope, which reveals disentangled, more or less aligned and parallel nanofibers with a smaller radius in the nanofibrous structure. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47206. 相似文献