全文获取类型
收费全文 | 528篇 |
免费 | 36篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 186篇 |
金属工艺 | 9篇 |
机械仪表 | 10篇 |
建筑科学 | 17篇 |
矿业工程 | 2篇 |
能源动力 | 25篇 |
轻工业 | 122篇 |
水利工程 | 2篇 |
无线电 | 12篇 |
一般工业技术 | 93篇 |
冶金工业 | 44篇 |
原子能技术 | 1篇 |
自动化技术 | 39篇 |
出版年
2024年 | 4篇 |
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 12篇 |
2019年 | 20篇 |
2018年 | 14篇 |
2017年 | 20篇 |
2016年 | 25篇 |
2015年 | 15篇 |
2014年 | 31篇 |
2013年 | 45篇 |
2012年 | 39篇 |
2011年 | 42篇 |
2010年 | 38篇 |
2009年 | 29篇 |
2008年 | 19篇 |
2007年 | 26篇 |
2006年 | 21篇 |
2005年 | 8篇 |
2004年 | 13篇 |
2003年 | 19篇 |
2002年 | 10篇 |
2001年 | 5篇 |
2000年 | 10篇 |
1999年 | 12篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1970年 | 1篇 |
排序方式: 共有564条查询结果,搜索用时 15 毫秒
141.
Sunitha M. Shivashankar Vishnumurthy K. Anantapadmanabha Airody Vasudeva Adhikari 《Polymer Engineering and Science》2013,53(6):1347-1356
In this communication we report synthesis of three new donor‐acceptor (D–A) type conjugated polymers carrying 1,3,4‐oxadiazole moiety and thiophene unit with different side groups at its 3,4 positions (4‐methoxybenzyl:P1, 3‐methylbenzyl:P2 and 4‐nitrobenzyl:P3) through polycondensation route using a series of newly synthesized monomers. The structures of new monomers and polymers were confirmed by NMR, FTIR spectroscopic methods followed by elemental analysis. Further, molecular weight and thermal stability were determined using gel permeation chromatography and thermogravimetric analysis. The linear optical and electrochemical properties of polymers were investigated by UV–vis absorption, fluorescence spectroscopic, and cyclic voltammetric studies. The polymers P1–P3 were found to be thermally stable and their electrochemical band gaps were determined to be 1.98, 2.14, and 2.18 eV respectively. Further their nonlinear optical properties were investigated by Z‐scan method using 532 nm, 7 ns laser pulses. The results reveal that they possess good optical limiting behavior due to effective three‐photon absorption (3PA) with absorption coefficient 2.5 × 10?24 m?3W2, 1.6 × 10?24 m?3W2, and 1.0 × 10?24 m?3W2. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers 相似文献
142.
Kanjana Khunathai Ying Xiong Biplob Kumar Biswas Birenda Babu Adhikari Hidetaka Kawakita Keisuke Ohto Katsutoshi Inoue Hisaya Kato Minoru Kurata Kinya Atsumi 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2012,87(3):393-401
BACKGROUND: This research provides a new approach to the effective use of microalgal biomass waste generated by biofuel conversion processes. In this study, a novel adsorbent for Au(III) recovery was prepared by treating microalgal residues with concentrated sulfuric acid. RESULTS: The prepared adsorbent, crosslinked microalgae, exhibited high affinity and selectivity for Au(III) over other precious and base metal ions in a hydrochloric acid medium. From the adsorption isotherms, the maximum adsorption capacity of the crosslinked microalgae for Au(III) was estimated to be 3.25 mol kg?1 (640 g kg?1), which was about eight times higher than the adsorption capacity of the microalgal residue. Microphotographs, scanning electron microscopy, and X‐ray diffraction confirmed the formation of metallic Au, suggesting that a redox reaction had taken place between the adsorbent and Au(III) ions during adsorption. Comparison of Fourier‐transform infrared spectra before and after adsorption indicated that hydroxyl groups as well as ether oxygen atoms in the crosslinked microalgae participated in the Au(III) uptake mechanism. It also suggested that the reduction of Au(III) to Au(0) was facilitated by hydroxyl groups in the crosslinked microalgae. CONCLUSION: The results presented in this paper are very promising for the practical use of microalgal residues for the recovery of Au(III) because of good selectivity and favorable adsorption capacity for Au(III). Copyright © 2011 Society of Chemical Industry 相似文献
143.
The thermodynamic state of hydrogen in aluminum during alkaline corrosion was investigated, using a two-compartment hydrogen permeation cell with an Al/Pd bilayer membrane. The open-circuit potential of the Pd layer in a pH 7.0 buffer solution was monitored to sense the hydrogen chemical potential, μH. At pH 12.5-13.5, the measurements established a minimum μH of 0.55 eV relative to the ideal gas reference, equivalent to a H2 gas pressure of 5.7 GPa. Statistical mechanics calculations show that vacancy-hydrogen defects are stable in Al at this condition. A dissolution mechanism was proposed in which H at very high μH is produced by oxidation of interfacial aluminum hydride. The mechanism explains the observed rapid accumulation of H in the metal by extensive formation of vacancy-hydrogen defects. 相似文献
144.
145.
The fibrous scaffolds are promising for tissue engineering applications because of their close structural resemblance with
native extracellular matrix. Additionally, the chemical composition of scaffold is also an important consideration as they
have significant influences on modulating cell attachment, morphology and function. In this study, chitosan-tripolyphosphate
(TPP) non-woven fibrous scaffolds were prepared through wetspinning process. Interestingly, at physiological pH these scaffolds
release phosphate ions, which have significant influences on cellular function. For the first time, cell viability in presence
of varying concentration of sodium TPP solution was analyzed and correlated with the phosphate release from the scaffolds
during 30 days incubation period. In vitro degradation of the chitosan-TPP scaffolds was higher than chitosan scaffolds, which
may be due to decrease in crystallinity as a result of instantaneous ionic cross-linking during fiber formation. The scaffolds
with highly interconnected porous structure present a remarkable cytocompatibility for cell growing, and show a great potential
for tissue engineering applications. 相似文献
146.
Bioassay-directed isolation and purification of the ethyl acetate and methanol extracts of Amelanchier canadensis resulted in 1,3-dilinoleoyl 2-olein (1), 1,3-dioleoyl 2-linolein (2), 5-hydroxymethyl-2-furfural (3), 5-(sorbitoloxymethyl)-furan-2-carboxaldehyde (4), 5-(mannitoloxymethyl)-furan-2-carboxaldehyde (5), and 5-(α-d-glucopyranosyloxymethyl) furan-2-carboxaldehyde (6). Four compounds, oleanolic acid (7), ursolic acid (8), kaempferol-3-O-α-l-rhamnopyranosyl (1 ← 2) rhamnopyranoside (9), and kaempferol-3-O-α-l-rhamnopyranoside (10) were isolated from the ethyl acetate extract of fresh fruits of Amelanchier arborea. The compounds were isolated and purified by various chromatographic techniques and characterized by NMR and GC/MS methods. The isolated compounds inhibited lipid peroxidation (by 85%) at 100 ppm when compared to 89%, 87%, and 98% for the commercial antioxidants butylated hydroxy anisole (BHA), butylated hydroxytoluene (BHT), and tert-butylhydroxyquinone (TBHQ) at 1.67, 2.2, and 1.67 ppm, respectively. Although not selective, some of these compounds inhibited cyclooxygenase (COX)-1 and -2 enzymes. Compounds 3–6 were isolated for the first time from A. canadensis and compounds 7–10 were isolated for the first time from A. arborea fruits. 相似文献
147.
After the energy crisis in the 1970s, considerable attention was focused on the development of alternate energy resources. At present, there is a renewed interest in biofuels due to increasing concerns about energy security and environmental pollution. One such biobased fuel that is being widely commercialized is biodiesel. With the increasing production of biodiesel a glut of glycerol has been created, causing market prices to plummet. This situation warrants finding alternative uses for glycerol. This study attempted to identify the possibility of blending glycerol and glycerol based co-products, such as propanediol and propanol with gasoline as oxygenates. The study revealed that there is a possibility to use glycerol and its derivatives with gasoline as an automotive fuel. Octane number and the heating value of different mixtures of gasoline, ethanol, and glycerol and its derivatives are presented. 相似文献
148.
Md. Nurul Islam Rifat Hasan Rupom Pashupati R. Adhikari Zoriana Demchuk Ivan Popov Alexei P. Sokolov H. Felix Wu Rigoberto C. Advincula Narendra Dahotre Yijie Jiang Wonbong Choi 《Advanced functional materials》2023,33(42):2302946
Additively manufactured flexible and high-performance piezoelectric devices are highly desirable for sensing and energy harvesting of 3D conformal structures. Herein, the study reports a significantly enhanced piezoelectricity in polyvinylidene fluoride (PVDF) achieved through the in situ dipole alignment of PVDF within PVDF-2D molybdenum disulfide (2D MoS2) composite by 3D printing. The shear stress-induced dipole poling of PVDF and 2D MoS2 alignment are harnessed during 3D printing to boost piezoelectricity without requiring a post-poling process. The results show a remarkable, more than the eight-fold increment in the piezoelectric coefficient (d33) for 3D printed PVDF-8wt.% MoS2 composite over cast neat PVDF. The underlying mechanism of piezoelectric property enhancement is attributed to the increased volume fraction of β phase in PVDF, filler fraction, heterogeneous strain distribution around PVDF-MoS2 interfaces, and strain transfer to the nanofillers as confirmed by microstructural analysis and finite element simulation. These results provide a promising route to design and fabricate high-performance 3D piezoelectric devices via 3D printing for next-generation sensors and mechanical–electronic conformal devices. 相似文献
149.
Saurabh Adhikari Tushar Kanti Gangopadhayay Souvik Pal D. Akila Mamoona Humayun Majed Alfayad N. Z. Jhanjhi 《计算机系统科学与工程》2023,46(2):2123-2140
Machine learning is a technique for analyzing data that aids the construction of mathematical models. Because of the growth of the Internet of Things (IoT) and wearable sensor devices, gesture interfaces are becoming a more natural and expedient human-machine interaction method. This type of artificial intelligence that requires minimal or no direct human intervention in decision-making is predicated on the ability of intelligent systems to self-train and detect patterns. The rise of touch-free applications and the number of deaf people have increased the significance of hand gesture recognition. Potential applications of hand gesture recognition research span from online gaming to surgical robotics. The location of the hands, the alignment of the fingers, and the hand-to-body posture are the fundamental components of hierarchical emotions in gestures. Linguistic gestures may be difficult to distinguish from nonsensical motions in the field of gesture recognition. Linguistic gestures may be difficult to distinguish from nonsensical motions in the field of gesture recognition. In this scenario, it may be difficult to overcome segmentation uncertainty caused by accidental hand motions or trembling. When a user performs the same dynamic gesture, the hand shapes and speeds of each user, as well as those often generated by the same user, vary. A machine-learning-based Gesture Recognition Framework (ML-GRF) for recognizing the beginning and end of a gesture sequence in a continuous stream of data is suggested to solve the problem of distinguishing between meaningful dynamic gestures and scattered generation. We have recommended using a similarity matching-based gesture classification approach to reduce the overall computing cost associated with identifying actions, and we have shown how an efficient feature extraction method can be used to reduce the thousands of single gesture information to four binary digit gesture codes. The findings from the simulation support the accuracy, precision, gesture recognition, sensitivity, and efficiency rates. The Machine Learning-based Gesture Recognition Framework (ML-GRF) had an accuracy rate of 98.97%, a precision rate of 97.65%, a gesture recognition rate of 98.04%, a sensitivity rate of 96.99%, and an efficiency rate of 95.12%. 相似文献
150.
In the present communication, a generalized procedure has been described for the performance evaluation of a solar air heater with N‐subcollectors with identical collector aspect ratio connected in various combinations such as in series, parallel and series–parallel. It has been found that the performance of a solar air heating system can be improved by operating several subcollectors in series in place of a single large collector with the same total area. Results have been presented to show the effect of various design parameters, viz. collector aspect ratio, mass flow rate, etc. on the performance of solar air heater with N‐subcollectors in series, parallel and series–parallel combinations. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献