全文获取类型
收费全文 | 2896篇 |
免费 | 265篇 |
国内免费 | 95篇 |
专业分类
电工技术 | 14篇 |
综合类 | 129篇 |
化学工业 | 1355篇 |
金属工艺 | 8篇 |
机械仪表 | 31篇 |
建筑科学 | 112篇 |
矿业工程 | 30篇 |
能源动力 | 85篇 |
轻工业 | 736篇 |
水利工程 | 21篇 |
石油天然气 | 429篇 |
武器工业 | 10篇 |
无线电 | 45篇 |
一般工业技术 | 176篇 |
冶金工业 | 15篇 |
原子能技术 | 23篇 |
自动化技术 | 37篇 |
出版年
2024年 | 12篇 |
2023年 | 51篇 |
2022年 | 73篇 |
2021年 | 98篇 |
2020年 | 91篇 |
2019年 | 96篇 |
2018年 | 109篇 |
2017年 | 89篇 |
2016年 | 99篇 |
2015年 | 106篇 |
2014年 | 118篇 |
2013年 | 340篇 |
2012年 | 203篇 |
2011年 | 207篇 |
2010年 | 164篇 |
2009年 | 149篇 |
2008年 | 110篇 |
2007年 | 152篇 |
2006年 | 129篇 |
2005年 | 109篇 |
2004年 | 89篇 |
2003年 | 84篇 |
2002年 | 66篇 |
2001年 | 72篇 |
2000年 | 80篇 |
1999年 | 59篇 |
1998年 | 46篇 |
1997年 | 37篇 |
1996年 | 37篇 |
1995年 | 23篇 |
1994年 | 22篇 |
1993年 | 16篇 |
1992年 | 19篇 |
1991年 | 17篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1978年 | 1篇 |
1973年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有3256条查询结果,搜索用时 15 毫秒
81.
Thermal stabilities and flame retardancies of phloroglucinol‐based organo phosphates when applied to polycarbonate
下载免费PDF全文
![点击此处可从《火与材料》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A series of organo phosphorus flame retardants (FRs) based on aromatic phosphate and cyclic phosphate were synthesized in an attempt to develop an efficient FR for polycarbonate. Their successful synthesis was confirmed by FT‐IR and 1 H and 31P NMR. Their thermal stability and flame retarding efficiency as a single‐component additive were investigated and compared with the commercial FR, resorcinol bis(diphenyl phosphate). The thermogravimetric analysis results revealed that the aromatic phosphate synthesized in this study, phloroglucinol diphenyl phosphate (PDP), shows a higher thermal degradation temperature and better flame retardancy even though it has a lower P content than cyclic phosphate‐based FRs. The flame retarding efficiency was evaluated by the UL‐94 test method. The V‐0 rating was achieved at a PDP loading of 2 wt% in polycarbonate in the presence of an anti‐dripping agent (1 wt%), which is better than that of resorcinol bis(diphenyl phosphate) and cyclic phosphate‐based FRs. The high thermal stability and P–OH generation tendency is responsible for the better flame‐retarding performance of PDP. The degradation path of PDP is also discussed. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
82.
A novel aromatic diamine, 3,3′‐diisopropyl‐4,4′‐diaminophenyl‐4″‐methyltoluene with a 4‐methylphenyl pendant group and isopropyl side groups, was designed and synthesized in this study. Then it was polymerized with various aromatic dianhydrides including pyromellitic dianhydride, 3,3′,4,4′‐biphenyltetracarboxylic dianhydride, 4,4′‐oxydiphthalic anhydride, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride and 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride via a one‐pot high temperature polycondensation procedure to produce a series of aromatic polyimides. These polyimides exhibited excellent solubility even in common organic solvents, such as chloroform and tetrahydrofuran. The flexible and tough films can be conveniently obtained by solution casting. The films were nearly colorless and exhibited high optical transparency, with the UV cutoff wavelength in the range 302–365 nm and the wavelength of 80% transparency in the range 385–461 nm. Moreover, they showed low dielectric constants (2.73–3.23 at 1 MHz) and low moisture absorption (0.13%–0.46%). Furthermore, they also possessed good thermal and thermo‐oxidative stability with 10% weight loss temperatures (T10%) in the range 489–507 °C in a nitrogen atmosphere. The glass transition temperatures of all polyimides are in the range 262–308 °C. Copyright © 2012 Society of Chemical Industry 相似文献
83.
84.
85.
86.
《Food Control》2014,35(2):347-355
The contents of polycyclic aromatic hydrocarbons (15 + 1 EU priority PAH) and phenolic substances (guaiacol, 4-methylguaiacol, syringol, eugenol, and trans-isoeugenol) in smoked Frankfurter-type sausages were investigated depending on the smoke generation method applied in a total of 63 smoking experiments. The smoke was generated by smouldering with different air supplies (smouldering smoke), by leading overheated steam through wood chips (steam smoke), by friction of a log (friction smoke), and by heating plates (touch smoke). The type of smoke generator had a noticeable influence on the contents of PAH and phenolic compounds. The highest mean content of PAH4 (2.6 μg/kg) was observed for sausages when intensive smouldering smoke was applied, the lowest (0.3 μg/kg) in friction-smoked sausages. The highest mean sum content of the five phenolic compounds was observed for sausages smoked with steam smoke (45 mg/kg) whereas the contents in friction- (15 mg/kg) and touch- (18 mg/kg) smoked products were relatively low. 相似文献
87.
FTIR是从傅立叶级数转换而来的红外定性和定量分析法的缩写,能有效监测淬火油在使用过程中的老化过程和监控基础油的质量,对于稳定淬火剂质量和监测淬火剂在使用过程的变化具有重要作用。 相似文献
88.
The preparation of new compounds, 1,1‐bis[4‐(2‐(4,4‐dimethyl‐1,3‐oxazolyl))phenyl]ethanol and a new symmetrically disubstituted 1,1‐diphenylethylene derivative, 1,1‐bis[4‐(2‐(4,4‐dimethyl‐1,3‐oxazolyl))phenyl]ethylene, is described. 1,1‐Bis[4‐(2‐(4,4‐dimethyl‐1,3‐oxazolyl))phenyl]ethylene was utilized as a dioxazolyl initiator precursor for the polymerization of styrene by atom transfer radical polymerization (ATRP) methods to produce α‐bis(oxazolyl) polystyrene. The kinetic study of the polymerization process indicated that the free radical polymerization reaction for the preparation of α‐bis(oxazolyl) polystyrene follows first‐order rate kinetics with respect to monomer consumption. α,ω‐Tetrakis(oxazolyl) polystyrene was prepared by a new, in situ, controlled/living, post‐ATRP chain‐end‐functionalization reaction which involves the direct addition of 1,1‐bis[4‐(2‐(4,4‐dimethyl‐1,3‐oxazolyl))phenyl]ethylene to the ω‐terminus of the α‐bis(oxazolyl) polystyrene derivative, without the isolation and purification of the polymeric precursor. α‐Bis(carboxyl) and α,ω‐tetrakis(carboxyl) polystyrene derivatives were obtained by the quantitative chemical transformation of the oxazoline groups of the respective aromatic oxazolyl chain‐end‐functionalized polystyrene derivatives to the aromatic carboxyl groups. The organic precursor compounds, the dioxazolyl‐functionalized 1,1‐diphenylethylene derivative and the functionalized polymers were characterized using 1H NMR and 13C NMR spectrometry and Fourier transform infrared spectroscopy, size‐exclusion and thin‐layer chromatography and non‐aqueous titration measurements. © 2014 Society of Chemical Industry 相似文献
89.
Empty fruit bunch (EFB) from oil palm is one of the potential biomass to produce biofuels like bio-oil due to its abundant supply and favorable physicochemical characteristics. Confirming the assertion, this paper presents an overview of EFB as a feedstock for bio-oil production. The fundamental characteristics of EFB in terms of proximate analysis, ultimate analysis and chemical composition, as well as the recent advances in EFB conversion processes for bio-oil production like pyrolysis and solvolysis are outlined and discussed. A comparison of properties in terms of proximate analysis, ultimate analysis and fuel properties between the bio-oil from EFB and petroleum fuel oil is included. The major challenges and future prospects towards the utilization of EFB as a useful resource for bio-oil production are also addressed. 相似文献
90.
Pleurotus ostreatus spent mushroom substrate for the degradation of polycyclic aromatic hydrocarbons: the case study of a pilot dynamic biopile for the decontamination of a historically contaminated soil
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)