全文获取类型
收费全文 | 1329篇 |
免费 | 24篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 11篇 |
综合类 | 63篇 |
化学工业 | 583篇 |
金属工艺 | 171篇 |
机械仪表 | 26篇 |
建筑科学 | 8篇 |
矿业工程 | 9篇 |
能源动力 | 51篇 |
轻工业 | 106篇 |
石油天然气 | 24篇 |
无线电 | 20篇 |
一般工业技术 | 131篇 |
冶金工业 | 97篇 |
原子能技术 | 44篇 |
自动化技术 | 29篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 14篇 |
2021年 | 14篇 |
2020年 | 35篇 |
2019年 | 16篇 |
2018年 | 11篇 |
2017年 | 24篇 |
2016年 | 24篇 |
2015年 | 26篇 |
2014年 | 43篇 |
2013年 | 79篇 |
2012年 | 55篇 |
2011年 | 83篇 |
2010年 | 44篇 |
2009年 | 78篇 |
2008年 | 85篇 |
2007年 | 81篇 |
2006年 | 85篇 |
2005年 | 66篇 |
2004年 | 68篇 |
2003年 | 46篇 |
2002年 | 63篇 |
2001年 | 27篇 |
2000年 | 34篇 |
1999年 | 53篇 |
1998年 | 33篇 |
1997年 | 39篇 |
1996年 | 29篇 |
1995年 | 26篇 |
1994年 | 28篇 |
1993年 | 18篇 |
1992年 | 7篇 |
1991年 | 11篇 |
1990年 | 3篇 |
1989年 | 8篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有1373条查询结果,搜索用时 15 毫秒
51.
《分离科学与技术》2012,47(8):2003-2022
Abstract Seabuckthorn pulp oil was fractionated using a crystallization process with acetone under controlled cooling rate of 0.25°C/min without agitation at different crystallization temperatures ranging from ? 15 to 15°C. The obtained liquid (LF) and solid (SF) fractions were analyzed for their fatty acid and triacylglycerol compositions and their melting profiles were characterized. Fractionation at ? 15°C yielded about 20% of LF where palmitoleic acid represented 53% of total lipids. The SF fraction was mainly rich in palmitic acid. LF were richer in triacylglycerol with acyl carbon numbers of 50 and 52 (C50 and C52) than SF, which contained a higher amount of C48. The melting curves of LF and SF showed multiple endothermic transitions. 相似文献
52.
《Drug development and industrial pharmacy》2013,39(9):1101-1115
ABSTRACTHydrophilic matrices are an interesting option when developing drug delivery systems. With this aim, hydroxypropyl methacrylate was grafted onto hydroxypropyl starch and hydroxypropyl cellulose substrates by following the Ce(IV) redox initiation method. Different amounts of ethyleneglycol dimethacrylate, 7 and 34 mol%, as the crosslinking monomer, were also added. The drying of grafted products was carried out by lyophilization, obtaining white powders. Reaction yields (percent grafting, grafting efficiency, etc.) and some physical characteristics of the powders (particle size, moisture uptake, density, morphology, etc.) were determined. These parameters indicate how useful these products may be as potential matrices for direct compressed tablets. In this light, the powder flowability and the binding properties of each copolymer were determined. The graft copolymers can be considered of great interest as direct compression excipients. Due to their different chemical structure and composition, they showed differences in viscoelastic properties that revealed an interesting range of possibilities for use in drug delivery formulations. Tablets formulated with conventional excipients were also tested. Dissolution tests of various tablets were carried out. In 12 hr, 60–80% of the model drugs was released. 相似文献
53.
《粉末冶金学》2013,56(4):259-264
In this study, the Selective Laser Melting (SLM) technology was used to manufacture flat specimens from Inconel 718 powder. The SLM process parameters have a major impact on the microstructure as well as on the mechanical properties of the fabricated specimens. Despite using optimized processing parameters, defects like pores cannot be completely avoided. These pores act as stress raisers and lead to premature crack initiation under cyclic loading, eventually reducing the fatigue strength of the material. Hot Isostatic Pressing (HIP) offers the possibility to eliminate the porosity and thus to increase the fatigue performance of the material. HIP combines high pressure and high temperature to produce materials with superior properties. Unfortunately, open porosity, i.e. open pores on the surface, can prevent full densification. In the present work, SLM flat specimens were encapsulated by means of Cathodic Arc Deposition (Arc-PVD) and High Velocity Oxygen Fuel Spraying (HVOF) to seal open pores. For this purpose, different encapsulation materials were investigated with a focus on materials offering additional functions such as an improved high temperature corrosion resistance or applicability as a bond coat for thermal barrier coatings. 相似文献
54.
G. Alberti R. Narducci M.L. Di Vona S. Giancola 《International Journal of Hydrogen Energy》2017,42(24):15908-15912
The last advances on the application of INCA (Ionomer Nc Analysis) methodology for a better understanding of perfluorinated ionomers are reported and discussed. It was found that INCA is a very suitable technique for the determination of the melting temperature (Tm) of un-crystallized and semi-crystalline perfluorinated ionomers. Furthermore, for these determinations, it is even more precise than dynamic mechanical analysis, a method essentially developed for polymers in which the water-uptake is negligible. Of interest, it is the information that INCA methodology gives on the phenomenon of the water-uptake memory of perfluorinated ionomers. 相似文献
55.
A.J. Chamkha A. Doostanidezfuli E. Izadpanahi M. Ghalambaz 《Advanced Powder Technology》2017,28(2):385-397
The melting process of a nano-enhanced phase-change material is investigated in a square cavity with a hot cylinder located in the middle of the cavity in the presence of both single and hybrid nanoparticles. The dimensionless partial differential equations are solved numerically using the Galerkin finite element method using a grid with 6000 quadrilateral elements. The effects of the volume fraction of nanoparticles, the Fourier number, the thermal conductivity parameter, and the viscosity parameters are studied. The results show that the solid-liquid interface and the liquid fraction are significantly affected by the volume fraction of nanoparticles and the thermal conductivity parameter. Additionally, it is found that the melting rate is much larger when the Fourier number changes between 0 and 0.5 and a further increase in the Fourier number causes a reduction in the rate of the melting. 相似文献
56.
Hongbin Gu Jiangning Wu Philip Chan Ginette Turcotte Tianjiang Ye 《Chemical Engineering Research and Design》2012
To improve surface hydrophilicity and to reduce fouling, commercial polypropylene microfiltration membranes were ozonated to generate peroxides as grafting sites for hydrophilic monomers. Ozonation was conducted in aqueous and gaseous phases, respectively. In both phases, the amount of peroxides increased with the ozonation time. A novel way to enhance the generation of peroxides was tested, i.e., adding homogeneous catalyst, CuSO4, to aqueous ozonation. Results showed that with an optimum dose of 0.05 g/L of CuSO4, the peroxides generated were 18.2% more than that by the non-catalyzed ozonation in aqueous phase. It was also confirmed by scavenger tests that during the aqueous ozonation both molecular ozone and free radicals contributed to the oxidation of the membranes, the latter was formed from the self-decomposition of ozone in water. Graft polymerization was also conducted after the generation of peroxides. A hydrophilic monomer, acrylic amide, was graft polymerized onto the membrane surface. The successful grafting of acrylic amide was confirmed by the formation of new peaks corresponding to amide groups in FTIR spectra. Results of contact angle measurements and filtration tests indicated that aqueous ozonation was more effective than its gaseous counterpart in terms of hydrophilicity improvement. In addition, the XRD analysis revealed that the ratio of the membrane surface crystallinity to amorphousity was changed by both ozonation and graft polymerization. Results of SEM scanning also showed changes in membrane surfaces after modification. 相似文献
57.
58.
The synthesis of monomodal copolymers with poly(ethylene glycol) (PEG) side chains from commercial poly(ethylene glycol) methacrylates (PEGMA) by atom transfer radical polymerization (ATRP) is verified. Two hydroxy-functionalized PEGMA macromonomers (520 g/mol and 360 g/mol) were copolymerized with methyl methacrylate (MMA) using various initial feed (1.5/98.5–50/50 mol.%). The copolymers P(MMA-co-PEGMA) with high degree of polymerization, e.g. 100–275 of repeating units in the backbone including 7–56 PEG side chains, were obtained. The relative reactivity ratios of PEGMA and MMA determined by the Jaacks method indicated slightly faster incorporation of macromonomer into polymeric chain than MMA (rMMA = 0.79; rPEGMA = 1.27). The polymers containing at least 17 mol.% of PEGMA units were water-soluble and exhibited clouding point at temperature in a broad range of 39–70 °C. The temperature-sensitive effect makes these polymers as a potential carriers in drug delivery systems. In the case of copolymers insoluble in water, a three-step procedure, including esterification to ATRP multifunctional macroinitiators, ATRP of tert-butyl methacrylate (tBMA) by grafting from, deprotection of carboxylic groups by removing tert-butyl groups, was applied to extend PEG grafts and expand the content of hydrophilic fraction (32–94 mol.%), what efficiently developed polymer solubility in polar solvents giving possibility for the future biomedical applications. 相似文献
59.
通过不同扫描速度和扫描方式的选区激光熔化(SLM)技术制备了Inconel 718合金,研究了工艺参数对熔池的形态、凝固组织、晶粒大小和晶粒取向的影响。结果表明,随着扫描速度增加,熔池的深度与宽度的比值增大,曲率增大;而扫描速度为1 450mm/s时,采用单向扫描比十字交叉扫描时深宽比值更大。在熔池内,凝固组织由熔池底部的胞晶向熔池侧面的胞枝晶转变。晶粒以<001>方向择优生长,其晶粒间的取向差角以小角度(<15°)为主。当十字交叉扫描时,随着扫描速度增加,小角度取向差角的分布分数增加。当速度一定、采用十字交叉扫描时,小角度的取向差角占比为62.57%,而采用单向扫描时为47.69%。 相似文献
60.
研究胶凝原油融化特性对原油集输及停输再启动等过程具有重要的意义。对初始温度为10℃,尺寸为30 mm×30 mm×10 mm原油试件在52.5、60、72.5℃三种不同水温中进行融化实验,并用红外热像仪记录原油融化过程随时间的变化情况,分析水温对融化时间、原油表面中心点温度以及原油形状的影响。实验结果表明,胶凝原油上表面中心点温度随时间先缓慢升高,后迅速增加,最后变缓并逐渐趋于水温;实验条件下原油融化时间分别为690、300和220 s;融化过程中原油上表面形状从方形逐渐变为圆形。 相似文献