全文获取类型
收费全文 | 2472篇 |
免费 | 171篇 |
国内免费 | 80篇 |
专业分类
电工技术 | 16篇 |
综合类 | 188篇 |
化学工业 | 1588篇 |
金属工艺 | 43篇 |
机械仪表 | 15篇 |
建筑科学 | 69篇 |
矿业工程 | 34篇 |
能源动力 | 11篇 |
轻工业 | 255篇 |
水利工程 | 13篇 |
石油天然气 | 284篇 |
武器工业 | 8篇 |
无线电 | 9篇 |
一般工业技术 | 126篇 |
冶金工业 | 47篇 |
原子能技术 | 8篇 |
自动化技术 | 9篇 |
出版年
2024年 | 4篇 |
2023年 | 19篇 |
2022年 | 18篇 |
2021年 | 35篇 |
2020年 | 44篇 |
2019年 | 54篇 |
2018年 | 48篇 |
2017年 | 63篇 |
2016年 | 63篇 |
2015年 | 68篇 |
2014年 | 112篇 |
2013年 | 136篇 |
2012年 | 191篇 |
2011年 | 178篇 |
2010年 | 128篇 |
2009年 | 142篇 |
2008年 | 109篇 |
2007年 | 165篇 |
2006年 | 170篇 |
2005年 | 156篇 |
2004年 | 113篇 |
2003年 | 103篇 |
2002年 | 105篇 |
2001年 | 79篇 |
2000年 | 97篇 |
1999年 | 52篇 |
1998年 | 47篇 |
1997年 | 36篇 |
1996年 | 41篇 |
1995年 | 25篇 |
1994年 | 24篇 |
1993年 | 22篇 |
1992年 | 12篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有2723条查询结果,搜索用时 31 毫秒
51.
剑麻纤维/酚醛树脂复合材料研究 总被引:20,自引:5,他引:20
本文采用碱处理、硅烷偶联剂处理、化学接枝和热处理等物理化学方法,对剑麻纤维进行改性。研究了改性后短剑麻纤维/酚醛树脂复合材料的弯曲性能、无缺口冲击强度和布氏硬度,借助扫描电子显微镜观察了复合材料的弯曲断口形貌,并研究了剑麻纤维的不同处理方法对复合材料耐水浸泡性的影响。结果表明:剑麻纤维经硅烷偶联剂处理后,能有效改善刚性的剑麻纤维与脆性的酚醛树脂基体之间的粘结,从而提高了复合材料的综合力学性能,剑麻 相似文献
52.
2000年世界苯酚总生产能力约为740万t/a,总消费量为636万t/a,主要用于生产双酚A和酚醛树脂。预计世界苯酚需求将以每年4%-5%的速度增长。美国、西欧和日本是世界上3个最主要的苯酚生产国家和地区,北美地区的总生产能力为300万t/a,占世界总产能的40.6%,而德国酚化学公司是世界最大的苯酚生产厂家,其产能为145万t/a,占世界总产能的19.6%。2000年,我国有30家苯酚生产企业,总生产能力为28.9万t/a,总产量为24.94万t/a,主要用于酚醛树脂和水杨酸的生产。在1996-2000年间,中国大陆苯酚的净进口量分别为9.79万t、6.22万t、3.72万t、7.38万t和9.69万t,从2000年9月开始,从中国台湾的苯酚进口量增长很快。为增强市场竞争力,中国大陆苯酚生产企业应提高单套装置的生产能力,采用一体化生产模式。 相似文献
53.
54.
以壬基酚聚氧乙烯醚(TX-10)、P2O5为原料,合成了水乳剂壬基酚聚氧乙烯醚磷酸酯。通过对还原剂用量等因素的讨论,确定最佳工艺条件为:次亚磷酸钠用量为TX-10的0.4%,n(TX-10)∶n(P2O5)∶n(H2O)=2∶1∶0.8,反应温度60℃,反应时间5h。在此条件下产品的酯化率为96.84%。 相似文献
55.
The photopolymerization of wood coatings under UV and visible light in industrial type conditions has been investigated. The inhibiting effect of the phenolic compounds found in wood extractives, especially quercetin, on the final properties of the coating (hardness, gel content) as well as the polymerization kinetics (rates, final conversion) has been discussed. Model clear‐coating formulations — based on an acrylate oligomer, a reactive diluent and a bis‐acylphosphine oxide as photo‐initiator — have been used. This article focuses on the influence of the nature of the acrylate oligomer (polyester, epoxy, polyurethane), the type of phenolic derivative (POHs) and the irradiation conditions (UV conveyor, Xe lamp). It appears that lead to through the strong inner‐filter effect in the presence of quercetin is responsible for the loss of all the observed properties. In order to mimic what happens at the wood–coating interface, the role of the diffusion of the phenolic derivatives have been also investigated and discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3285–3298, 2007 相似文献
56.
57.
ABSTRACT Treatments of phenol formaldehyde producing wastewater (PFPW) by electrooxidation (EO) and electro-Fenton (EF) successive processes were carried out in a batch electrolytic reactor using graphite (Gr) and stainless steel (Ss) electrodes. After the completion of the EO process, the wastewater was further treated with EF process. The influence of operating variables such as current density, operating time, initial pHi and H2O2 concentration was evaluated for removals of phenol, TOC and COD in PFPW. Gr/Gr, Gr/Ss or Ss/Ss and Ss/Gr electrode pair were used as anode and cathode. The best removal efficiency in the EO process was obtained with Gr/Gr (93%) as compared to Gr/Ss (82%), Ss/Ss (63%) and Ss/Gr (55%). The removal efficiencies for the EO process using Gr-Gr electrode pair were obtained as 93% for phenol, 61% for COD and 44% for TOC at initial pHi 7,5 g/L of NaCl, 50 mA/cm2 and 5 h. In the EF process, the removal efficiencies at pHi 3,5 mA/cm2 and 30 mM H2O2 and 45 min were 100% for phenol, 76% for COD and 59% for TOC. This study provided that the successive processes are an effective method for the removal of phenolic compounds from the wastewater. 相似文献
58.
In this study, phenolated wood resin was used an adsorbent for the removal of Cr(III), Ni(II), Zn(II), Co(II) ions by adsorption from aqueous solution. The adsorption of metal ions from solution was carried at different contact times, concentrations and pHs at room temperature (25°C). For individual metal ion, the amount of metal ions adsorbed per unit weight of phenolated wood resin at equilibrium time increased with increasing concentration and pH. Also, when the amounts of metal ions adsorbed are compared to each other, it was seen that this increase was order of Cr(III) > Ni(II) > Zn(II) > Co(II). This increase was order of Cr(III) > Ni(II) > Co(II) > Zn(II) for commercial phenol–formaldehyde resin. Kinetic studies showed that the adsorption process obeyed the intraparticle diffusion model. It was also determined that adsorption isotherm followed Langmuir and Freundlich models. Adsorption isotherm obtained for commercial phenol–formaldehyde resin was consistent with Freundlich model well. Adsorption capacities from Langmuir isotherm for commercial phenol–formaldehyde resin were higher than those of phenolated wood resin, in the case of individual metal ions. Original adsorption isotherm demonstrated the monolayer coverage of the surface of phenolated wood resin. Adsorption kinetic followed the intraparticle diffusion model. The positive values of ΔG° determined using the equilibrium constants showed that the adsorption was not of spontaneous nature. It was seen that values of distribution coefficient (KD) decreasing with metal ion concentration in solution at equilibrium (Ce) indicated that the occupation of active surface sites of adsorbent increased with metal ions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2838–2846, 2006 相似文献
59.
The main cause to the deactivation of ZSM-5 catalyst, used for oxidation of benzene to phenol (BTOP) by nitrous oxide, is that the carbon deposition on the catalyst surface blocks the mouth of pores of the catalyst.In the experiments, ZSM-5 catalyst was modified by chemical surface deposition of silicon, and then the effect of modification condition on the catalyst activation was studied. The catalyst samples were characterized by XRF,EPS, XRD, TEM, N2 adsorption at low temperature, pyridine adsorption-infrared technique and etc. All the above results show that the uniform SiO2 membrane can be formed on ZSM-5 crystal surface. The SiO2 membrane covers the acid centers on ZSM-5 surface to inhibit surface coking, to avoid or decrease the possibility of ZSM-5 pore blockage so that the catalyst activity and stability can be improved efficiently. The optimum siliconiting conditions determined by the experiments are as follows: 4% load of silanizing agent, volume (ml)/mass (g) ratio of hexane/ZSM-5=15/1, and 16 h of modification time. Compared with the samples without siliconiting treatment,the samples treated under the above optimum condition can increase the productivity of phenol by 14% for 3 h reaction time and by 41% for 6 h reaction time respectively. 相似文献
60.
Copper(II), nickel(II) and zinc(II) complexes of amidate ligand 1,2-bis(2-hydroxybenzamido)ethane(H2hybe) encapsulated in the super cages of zeolite-Y have been prepared and characterized by spectroscopic studies and thermal as well as X-ray diffraction (XRD) patterns. These complexes catalyze the liquid-phase hydroxylation of phenol with H2O2 to catechol as a major product and hydroquinone as a minor product. Considering the concentration of substrate and oxidant, amount of catalyst, temperature of the reaction and volume of solvent, a best-suited reaction condition has been optimized to get maximum hydroxylation. Under the optimized reaction conditions, [Cu(hybe)]-Y has shown the highest conversion of 40% after 6h, which is followed by [Ni(hybe)]-Y with 37% conversion and [Zn(hybe)]-Y has shown the poorest performance with 33% conversion. All these catalysts are more selective towards catechol formation (90%), irrespective of their catalytic performance. 相似文献