全文获取类型
收费全文 | 692篇 |
免费 | 15篇 |
国内免费 | 12篇 |
专业分类
化学工业 | 519篇 |
金属工艺 | 3篇 |
机械仪表 | 4篇 |
建筑科学 | 1篇 |
矿业工程 | 2篇 |
能源动力 | 69篇 |
轻工业 | 59篇 |
石油天然气 | 3篇 |
无线电 | 4篇 |
一般工业技术 | 45篇 |
冶金工业 | 1篇 |
原子能技术 | 4篇 |
自动化技术 | 5篇 |
出版年
2024年 | 2篇 |
2023年 | 29篇 |
2022年 | 22篇 |
2021年 | 13篇 |
2020年 | 27篇 |
2019年 | 23篇 |
2018年 | 29篇 |
2017年 | 19篇 |
2016年 | 33篇 |
2015年 | 42篇 |
2014年 | 71篇 |
2013年 | 60篇 |
2012年 | 68篇 |
2011年 | 65篇 |
2010年 | 45篇 |
2009年 | 47篇 |
2008年 | 28篇 |
2007年 | 34篇 |
2006年 | 21篇 |
2005年 | 1篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1993年 | 1篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有719条查询结果,搜索用时 15 毫秒
81.
《Fuel》2006,85(12-13):1851-1859
Pyrolysis of Euphorbia rigida and sesame stalk biomass samples with two selected commercial catalyst, namely DHC-32 and HC-K 1.3Q, have been conducted in a fixed-bed reactor. The effect of different catalysts and their ratio (5, 10 and 20% w/w) and pyrolysis temperature (500 and 750 °C) on the pyrolysis product yields were investigated and the obtained results were compared with similar experiments without catalyst. Bio-oil yield was increased comparing with non-catalytic experiments, at final pyrolysis temperature of 500 °C for both biomass samples and catalysts. In the catalytic experiments; when the temperature reached to 750 °C, although bio-oil product yield was reduced, the gas product yield was increased comparing with non-catalytic experiments.The pyrolysis oils were examined using spectroscopic and chromatographic analyses and then fractioned by column chromatography. Although the aliphatic and aromatic fractions were decreased and polar fraction was increased with catalytic pyrolysis of E. rigida; an opposite trend was observed in the sesame stalk pyrolysis oil, comparing with non-catalytic results.Obtained results were compared with petroleum fractions and determined the possibility of being a potential source of renewable fuels. 相似文献
82.
比较了采用高效液相色谱法和化学滴定法2种方法测定3,4,5-三甲氧基苯甲酸的含量,提出了测定操作的实验条件,并对测定结果进行统计分析,以判断和评价2种方法的准确性和实用性。经过Grubbs检验表明2种方法的测定数据均无异常值;通过偏态系数和峰态系数来检验方法的正态性分布,统计结果表明2种方法均遵从正态分布;同时进行了2种方法测定值的均数检验(t检验),结果表明二者的测定值无显著性差异。高效液相色谱法的测定值有更高的准确度和精密度,可以作为首选,在不具备色谱仪的情况下也可使用化学滴定法。 相似文献
83.
以通过溶胶-凝胶法自制的Fe3O4@壳聚糖(CTS)微球为载体,甲基橙(MO)为模板分子,采用水溶液聚合法制得磁性壳聚糖表面分子印迹聚合物(MMIPs)。通过SEM、XRD、FT-IR和VSM表征了MMIPs的结构和性能,并探究了其对MO的识别与选择性吸附特性。研究表明:与非印迹聚合物(NIMPs,饱和吸附量为20.56 mg/g)相比,在相同条件(pH值6.5、25℃)下,MMIPs对MO具有明显的特异性吸附能力,在60 min左右吸附饱和,饱和吸附量(Qe)可达113.16 mg/g;MMIPs对MO的吸附符合Langmuir等温吸附模型和准二级吸附动力学模型;在其他干扰染料的存在下,MMIPs的选择性系数(K)最高可达2.85,对MO具有选择识别性;此外,吸附完成后MMIPs可在磁场作用下快速分离,解吸附后循环使用5次,吸附率均在90%以上。 相似文献
84.
Haibo Zhang Yanping Yang Minggui Shen Shibin Shang Jie Song Jianxin Jiang Zhanqian Song 《Iranian Polymer Journal》2018,27(6):405-411
A full bio-based cured resin was synthesized by copolymerization of acrylated-epoxidized soybean oil (AESO) and 2-acrylamidoethyl dehydroabietic acid (DHA-HEMAA). The rigid rosin-based monomer 2-acrylamidoethyl dehydroabietic acid was first prepared from dehydroabietic acid and N-hydroxyethylacrylamide, which was characterized by nuclear magnetic resonance and Fourier transform infrared (FTIR) spectrometry techniques. The cured resin was then synthesized and characterized by FTIR spectroscopy, differential scanning calorimetry, dynamic thermomechanical analysis, and thermogravimetric analysis, as well as using a Kruss tensiometer and a universal testing machine. The results indicated that the resin cured with rosin-based monomer exhibited excellent thermomechanical properties. The crosslink density and thermal stability of cured samples containing DHA-HEMAA at molar ratio between 10 and 30% were higher than those of AESO/DHA-HEMAA0 sample. With increasing DHA-HEMAA content, the glass transition temperature (Tg), elongation-at-break, and tensile strength of samples increased, in the stated order, from 16 to 38 °C, from 24 to 45.8%, and from 1.7 to 6.5 MPa. Due to DHA-HEMAA with a hydrophenanthrene structure, the θ values increased with the increase of DHA-HEMAA molar ratios. The full bio-based rosin thermosetting resins may have great potentials in practical application fields, such as coating, adhesive, and packaging materials. 相似文献
85.
A new general and green synthetic protocol for the synthesis of manganese(III) metallocorroles has been developed from substituted aryl aldehydes and 5-(4-nitrophenyl)dipyrromethane using manganese salt as template. This is the first report in the synthesis of corroles: the formation of direct CC bond through metal initiation. This method allows higher working concentrations than those previously reported. The new A2B manganese(III) metallocorroles were synthesized in good yield for different applications. The single crystal X-ray structure of 10-(3,4,5-fluorophenyl)-5,15-bis(4-nitrophenyl)manganese(III) corrole is also reported and shows that manganese atom is situating atop on macrocyclic plane. 相似文献
86.
《International Journal of Hydrogen Energy》2020,45(53):29212-29221
To increase proton conductivity of chitosan (CS) based polymer electrolyte membranes, a novel nanofiller-solid superacide SO42--TiO2 (STi) coated carbon nanotubes (STi@CNTs) are introduced into CS matrix to fabricate membranes for polymer electrolyte membrane fuel cells (PEMFCs). Owing to the STi coating, the dispersion ability of CNTs and interfacial bonding are obviously improved, hence, CNTs can more fully play their reinforcing role, which makes the CS/STi@CNTs composite membranes exhibit better mechanical properties than that of pure CS membrane. More importantly, STi possesses excellent proton transport ability and may create facile proton transport channels in the membranes with the help of high aspect ratio of CNTs. Particularly, the CS/STi@CNTs-1 membrane (1 wt% STi@CNTs loading) obtains the highest proton conductivity of 4.2 × 10−2 S cm–1 at 80 °C, enhancing by 80% when compared with that of pure CS membrane. In addition, the STi@CNTs also confer the composite membranes low methanol crossover and outstanding cell performance. The maximum power density of the CS/STi@CNTs-1 membrane is 60.7 mW cm−2 (5 M methanol concentration, 70 °C), while pure CS membrane produces the peak power density of only 39.8 mW cm−2. 相似文献
87.
88.
89.
Qing Li Jing Li Guangfu Liao Zushun Xu 《Journal of materials science. Materials in medicine》2018,29(8):126
1,3,5-Tris(4-aminophenoxy) benzene (TAPOB) and 2,2-bis [4-(3,4-dicarboxyphenoxy) phenyl] propane dianhydride (BPADA) were used to synthesize an amino-terminated hyperbranched polyimide (AM-HBPI). Then, the 2-methacryloyloxyethyl phosphorylcholine-modified hyperbranched polyimide (HBPI-MPC) was obtained through the graft modification of MPC onto AM-HBPI by Michael addition. The infrared spectroscopy and X-ray photoelectron spectroscopy spectra showed MPC molecules were successfully grafted onto the HBPI molecules. The HBPI-MPC films exhibited slightly decreased thermal stabilities with 5% weight loss temperature in the range of of 418–483?°C in nitrogen, compared with the pure HBPI film. With the increase of MPC grafting amount, the static water contact angles decreased from average 84.0° of the pure HBPI film to average 45.0° of the HBPI-MPC film with 20% MPC. Meanwhile, the increased surface roughness of the HBPI-MPC films increased the contact areas with the platelets, enhancing their anticoagulant efficiency. The number of platelet adhesion declined and the shape of platelet changed from flat to round. The recalcification times grew from average 300?s of pure HBPI to average 551?s of the HBPI-MPC film with 20% MPC, indicating improved anticoagulant properties and biocompatibility. Bacterial adhesion test also demonstrated the number of bacterial adhesion was significantly reduced and antibacterial properties were improved. Thus, the HBPI-MPC films have great application prospects as biomedical anticoagulant materials. 相似文献
90.
为提高双组分水性聚氨酯的室温交联速度,将N-苄基乙醇胺引入到环氧树脂制备了环氧树脂基水性多元醇,表征了多元醇的化学结构,并测定了其相对分子质量、粒径分布和玻璃化温度等主要技术参数。将环氧树脂基水性多元醇与多异氰酸酯配合制备了双组分水性聚氨酯,采用红外光谱法研究了室温交联反应过程。研究结果表明:多元醇分子结构中引入苄胺基加快了双组分水性聚氨酯的交联反应速度。将双组分水性聚氨酯制备成水性木器涂料,漆膜具有优异的耐冲击性、附着力、柔韧性、光泽、耐液体介质、硬度、丰满度等性能。 相似文献