全文获取类型
收费全文 | 599篇 |
免费 | 33篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 7篇 |
综合类 | 2篇 |
化学工业 | 206篇 |
金属工艺 | 6篇 |
机械仪表 | 14篇 |
建筑科学 | 15篇 |
矿业工程 | 1篇 |
能源动力 | 66篇 |
轻工业 | 79篇 |
水利工程 | 5篇 |
石油天然气 | 8篇 |
无线电 | 56篇 |
一般工业技术 | 69篇 |
冶金工业 | 29篇 |
原子能技术 | 2篇 |
自动化技术 | 68篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 18篇 |
2021年 | 41篇 |
2020年 | 28篇 |
2019年 | 25篇 |
2018年 | 37篇 |
2017年 | 31篇 |
2016年 | 31篇 |
2015年 | 22篇 |
2014年 | 42篇 |
2013年 | 70篇 |
2012年 | 47篇 |
2011年 | 53篇 |
2010年 | 32篇 |
2009年 | 30篇 |
2008年 | 22篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 9篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 8篇 |
1999年 | 4篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1973年 | 1篇 |
1965年 | 1篇 |
1958年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有633条查询结果,搜索用时 15 毫秒
31.
Formation and Phase Behavior of Winsor Type III <Emphasis Type="Italic">Jatropha curcas</Emphasis>-Based Microemulsion Systems
下载免费PDF全文
![点击此处可从《Journal of surfactants and detergents》网站下载免费的PDF全文](/ch/ext_images/free.gif)
M. S. W. Nordiyana Munawar Khalil Badrul Mohamed Jan Brahim Si Ali Chong Wen Tong 《Journal of surfactants and detergents》2016,19(4):701-712
The formation and phase behavior of Jatropha curcas-based microemulsion systems, which could potentially be used in enhanced oil recovery applications, has been investigated. Winsor type III microemulsions were obtained by adding n-octane to Winsor type I microemulsion systems prepared using various concentrations of alkyl polyglucoside (APG). To optimize the formulation of type III microemulsion systems, five different types of co-surfactants, i.e. normal butyl alcohol (NBA), isobutyl alcohol, isopropyl alcohol, fatty acid alcohol C8 (FAC8) and fatty acid alcohol C8/C10 (FAC8/C10) were used. The microemulsion phase behavior was determined along with particle size distributions by dynamic light scattering measurements. Results show that the optimum Winston type III system can be achieved by mixing 3 wt% of NBA, 1 wt% APG and 3 wt% NaCl. At the optimum formulation, the IFT reached a minimum value (0.016 mN/m) and formed very small emulsion droplets with a narrow particle size distribution. 相似文献
32.
Nor Halaliza Alias Robiah Yunus Azni Idris Rozita Omar 《European Journal of Lipid Science and Technology》2009,111(4):368-375
Hydraulic fluids represent one of the most important groups of industrial lubricants. Increasing attention to environmental issues drives the lubricant industry to choose vegetable‐based hydraulic fluids which are biodegradable as compared to mineral‐based fluids. However, the lubricating properties of vegetable oil, such as poor oxidative stability and high pour point, have hindered their use. In this study, trimethylolpropane ester, which was derived from palm‐based methyl ester, was used as the base hydraulic fluid. The purpose of the study was to determine the optimum formulation for palm oil‐based synthetic lubricants by using suitable additives that can improve the oxidative stability and viscosity in accordance with the standard regulations for hydraulic fluid applications. The oxidative stability of the oil was evaluated by total acid number (TAN) and viscosity tests. In general, base oil without additive began to degrade after 200 h. The formulated oil, on the other hand, was quite stable even after 800 h of operation. The best formulation was obtained using 1.0% of either additive A or additive B. Both TAN and viscosity values were found to increase with increasing heating temperature. Meanwhile, the results have also shown that additive A performs better than additive B. After 800 h of exposure, the final TAN value for the formulated oil was only at 0.32 as compared to 4.88 mg KOH/g for the oil without additive. However, the kinematic viscosity of the oil at 40 and 100 °C was almost unchanged as compared to the oil without additive. 相似文献
33.
Reinforcement of graphene nanoplatelets on plasticized poly(lactic acid) nanocomposites: Mechanical,thermal, morphology,and antibacterial properties
下载免费PDF全文
![点击此处可从《应用聚合物科学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Buong Woei Chieng Nor Azowa Ibrahim Wan Md Zin Wan Yunus Mohd Zobir Hussein Yoon Yee Then Yuet Ying Loo 《应用聚合物科学杂志》2015,132(11)
Plasticized poly(lactic acid) (PLA)‐based nanocomposites filled with graphene nanoplatelets (xGnP) and containing poly(ethylene glycol) (PEG) and epoxidized palm oil (EPO) with ratio 2 : 1 (2P : 1E) as hybrid plasticizer were prepared by melt blending method. The key objective is to take advantage of plasticization to increase the material ductility while preserving valuable stiffness, strength, and toughness via addition of xGnP. The tensile modulus of PLA/2P : 1E/0.1 wt % xGnP was substantially improved (30%) with strength and elasticity maintained, as compared to plasticized PLA. TGA analysis revealed that the xGnP was capable of acting as barrier to reduce thermal diffusion across the plasticized PLA matrix, and thus enhanced thermal stability of the plasticized PLA. Incorporation of xGnP also enhanced antimicrobial activity of nanocomposites toward Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, and Listeria monocytogenes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41652. 相似文献
34.
M. Z.M. Nor M. A. Noranizan N. L. Chin K. Hashim 《International Journal of Food Properties》2013,16(5):966-977
This work describes the effect of a repetitive cooking-chilling process on resistant starch content in crackers prepared from a mixture of fish and starch, which are popularly known in Malaysia as “keropok.” Three fish cracker formulations were prepared using tapioca, wheat, and sago starch. Up to four cycles of repetitive cooking-chilling increased the resistant starch content in all products; however, the hardness of chilled samples decreased, and their moisture content increased. For the fried samples, the texture became harder, the color turned darker, and linear expansion was reduced. The dried fish cracker samples prepared with sago starch yielded the highest resistant starch content. The results demonstrated that four cycles of repetitive cooking-chilling were able to enhance resistant starch in fish crackers. 相似文献
35.
Spermatogenesis has been studied in testicular biopsies by means of microfluorometric assessment of the DNA-DNP complex using ethidium bromide in 10 men with histologically normal spermatogenesis and in 10 men with histologically reduced spermatogenesis. The expected haploid DNA value was found in the round spermatids, whereas only 70% of the haploid fluorescence value was found in the elongated spermatids and around 60% in the testicular spermatozoa. No difference was found in the mean fluorescence values between the pathological group and the controls. it is suggested that structural changes or an increase in basic nuclear proteins gradually exclude the ethidium bromide from the binding to the DNA molecule and that this phenomenon occurs concomitantly with a decrease in double-stranded RNA. The difference in fluorescence intensity before and after RNAase treatment was regarded as an approximate estimate of the RNA content. There was a significant decrease of these values during spermatogenesis. 相似文献
36.
Helmi Zulhaidi M. Shafri Nasrulhapiza Hamdan Mohamad Izzuddin Anuar 《International journal of remote sensing》2013,34(14):4293-4311
Existing vegetation indices and red-edge techniques have been widely used for the assessment of vegetation status and vegetation health from remote-sensing instruments. This study proposed and applied optimized Airborne Imaging Spectrometer for Applications (AISA) airborne hyperspectral indices in assessing and mapping stressed oil palm trees. Six vegetation indices, four red-edge techniques, a standard supervised classifier and three optimized AISA spectral indices were compared in mapping diseased oil palms using AISA airborne hyperspectral imagery. The optimized AISA spectral indices algorithms used newly defined reflectance values at wavelength locations of 734 nm (near-infrared (NIR)) and 616 nm (red). The selection of these two bands was based on laboratory statistical analysis using field spectroradiometer reflectance data. These two bands were then applied to the AISA airborne hyperspectral imagery using the three optimized algorithms for AISA data. The newly formulated AISA hyperspectral indices were D2 = R 616/R 734, normalized difference vegetation index a (NDVIa)?=?(R 734 – R 616)/(R 734?+?R 616) and transformed vegetation index a (TVIa)?=?((NDVIa?+?0.5)/(abs (NDVIa?+?0.5))?×?[abs (NDVIa?+?0.5)]1/2. The classification results from the optimized AISA hyperspectral indices were compared with the other techniques and the optimized AISA spectral indices obtained the highest overall accuracy. D2 and NDVIa obtained 86% of overall accuracy followed by TVIa with 84% of overall accuracy. 相似文献
37.
Norhayati Hashim Nor Saleha Misuan Illyas Md Isa Azlan Kamari Azmi Mohamed Suriani Abu Bakar 《Journal of Experimental Nanoscience》2016,11(10):776-797
ABSTRACTMagnesium layered hydroxide (MLH) intercalated with anionic 3-(4-methoxyphenyl)propionic acid (MPP) was synthesised by a direct reaction method using magnesium oxide and MPP as precursors. A further coating of chitosan was applied on the external surface of MLH–MPP nanocomposite to form a new material, named MLH–MPP/chitosan nanocomposite. The XRD pattern showed an intense and sharp peak at basal spacing 18.9 Å, proving that MPP anions were successfully intercalated into the interlayer gallery of MLH in a monolayer arrangement. The XRD pattern of the MLH–MPP/chitosan nanocomposite shows similar peaks with the MLH–MPP nanocomposite. The result was also supported by FTIR spectra and elemental analysis. TGA/DTG spectra showed that the thermal stabilities of the guest anion in the both nanocomposites were markedly enhanced. A controlled-release study of the MPP ion from the MLH–MPP/chitosan nanocomposite showed a slower release compared to MLH–MPP nanocomposite with an initial rapid release and slow release thereafter. Meanwhile, the release behaviours of MPP ions from both nanocomposites were governed by pseudo-second order kinetics. This result highlights the potential of the nanocomposite as an encapsulated material for the controlled-release formulation of MPP anions. 相似文献
38.
A technique was developed for transfer of fat and polychlorinated biphenyls from cod liver oil into the lipophilic gel Lipidex 5000. Subsequent elution of the gel separated about 60% of the fat from the sample. Following further purification on aluminium oxide and silica gel, toxic non-ortho- and mono-ortho-PCB congeners were isolated in two separate fractions on charcoal. Recoveries were studied by addition of twelve different PCB congeners to 0.2 g of fat. The non-ortho-PCBs were labelled with 13C. The recoveries of 5-50 ng of the unlabelled compounds were 80-100% and those of 50-100 pg of the labelled compounds were 76-106%. 相似文献
39.
Yasir Amer Al-Jawhar Khairun N. Ramli Montadar Abas Taher Nor Shahida M. Shah Salama A. Mostafa Bashar Ahmed Khalaf 《ETRI Journal》2021,43(2):209-220
The filtered orthogonal frequency division multiplexing (F-OFDM) system has been recommended as a waveform candidate for fifth-generation (5G) communications. The suppression of out-of-band emission (OOBE) and asynchronous transmission are the distinctive features of the filtering-based waveform frameworks. Meanwhile, the high peak-to-average power ratio (PAPR) is still a challenge for the new waveform candidates. Partial transmit sequence (PTS) is an effective technique for mitigating the trend of high PAPR in multicarrier systems. In this study, the PTS technique is employed to reduce the high PAPR value of an F-OFDM system. Then, this system is compared with the OFDM system. In addition, the other related parameters such as frequency localization, bit error rate (BER), and computational complexity are evaluated and analyzed for both systems with and without PTS. The simulation results indicate that the F-OFDM based on PTS achieves higher levels of PAPR, BER, and OOBE performances compared with OFDM. Moreover, the BER performance of F-OFDM is uninfluenced by the use of the PTS technique. 相似文献
40.
Massive multiple-input multiple-output (MIMO) systems combined with beamforming antenna array technologies are expected to play a key role in next-generation wireless communication systems (5G), which will be deployed in 2020 and beyond. The main objective of this review paper is to discuss the state-of-the-art research on the most favourable types of beamforming techniques that can be deployed in massive MIMO systems and to clarify the importance of beamforming techniques in massive MIMO systems for eliminating and resolving the many technical hitches that massive MIMO system implementation faces. Classifications of optimal beamforming techniques that are used in wireless communication systems are reviewed in detail to determine which techniques are more suitable for deployment in massive MIMO systems to improve system throughput and reduce intra- and inter-cell interference. To overcome the limitations in the literature, we have suggested an optimal beamforming technique that can provide the highest performance in massive MIMO systems, satisfying the requirements of next-generation wireless communication systems. 相似文献