全文获取类型
收费全文 | 2045篇 |
免费 | 124篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 44篇 |
化学工业 | 498篇 |
金属工艺 | 47篇 |
机械仪表 | 33篇 |
建筑科学 | 44篇 |
矿业工程 | 1篇 |
能源动力 | 50篇 |
轻工业 | 200篇 |
水利工程 | 23篇 |
石油天然气 | 17篇 |
无线电 | 263篇 |
一般工业技术 | 301篇 |
冶金工业 | 422篇 |
原子能技术 | 21篇 |
自动化技术 | 207篇 |
出版年
2023年 | 11篇 |
2022年 | 35篇 |
2021年 | 41篇 |
2020年 | 36篇 |
2019年 | 36篇 |
2018年 | 37篇 |
2017年 | 59篇 |
2016年 | 70篇 |
2015年 | 55篇 |
2014年 | 74篇 |
2013年 | 89篇 |
2012年 | 68篇 |
2011年 | 105篇 |
2010年 | 80篇 |
2009年 | 84篇 |
2008年 | 81篇 |
2007年 | 87篇 |
2006年 | 73篇 |
2005年 | 61篇 |
2004年 | 57篇 |
2003年 | 55篇 |
2002年 | 68篇 |
2001年 | 40篇 |
2000年 | 31篇 |
1999年 | 37篇 |
1998年 | 143篇 |
1997年 | 76篇 |
1996年 | 66篇 |
1995年 | 61篇 |
1994年 | 40篇 |
1993年 | 42篇 |
1992年 | 22篇 |
1991年 | 23篇 |
1990年 | 22篇 |
1989年 | 19篇 |
1988年 | 16篇 |
1987年 | 21篇 |
1986年 | 22篇 |
1985年 | 16篇 |
1984年 | 15篇 |
1983年 | 12篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1977年 | 5篇 |
1976年 | 17篇 |
1975年 | 4篇 |
1970年 | 6篇 |
1968年 | 4篇 |
排序方式: 共有2171条查询结果,搜索用时 31 毫秒
91.
Asla Medeiros e Sá Karina Rodriguez Echavarria David Arnold 《The Visual computer》2014,30(12):1321-1331
The increasing popularity of 3D printing is drawing the interest of the research community to the possibilities and challenges of this manufacturing method. Amongst its many uncertainties, we are concerned here with one of its certainties—that reduction of the material required in 3D printing is critical for efficiency and affordability. In this paper, we propose a solution to the computer graphics problem of, given a volume boundary, automatically defining the mesh of a low density internal structure that is 3D-printable. The proposed solution involves two steps. The first step is to define a cell complex partition for the internal space of a volume defined by its boundaries. The second step, is to apply the Skin4Skeleton algorithm, which uses the cell complex dual to produce a 3D-printable cell-complex mesh with a parametrised thickness. 相似文献
92.
This work proposes an analytic method for resolving planar multi-point indeterminate impact problems for rigid-body systems. An event-based approach is used to detect impact events, and constraints consistent with the rigid-body assumption are used to resolve the indeterminacy associated with multi-point impact analysis. The work-energy relation is utilized to determine post-impact velocities based on an energetic coefficient of restitution to model energy dissipation, thereby yielding an energetically consistent set of post-impact velocities based on Stronge’s energetic coefficient of restitution for the treatment of rigid impacts. The effect of stick–slip transition is analyzed based on Coulomb friction. This paper also discusses the transition from impact to contact. This analysis is essential for considering the rocking block problem that is used as an example herein. The predictions of the model for the rocking block problem are compared to experimental results published in the literature. An example of a planar ball undergoing two-point impact is also presented. 相似文献
93.
Ozonation of Pyrolytic Aqueous Phase: Changes in the Content of Phenolic Compounds and Color 下载免费PDF全文
Shi‐Shen Liaw Oselys Rodriguez Justo Victor Haber Perez Shuai Zhou Manuel Garcia‐Perez 《化学工程与技术》2016,39(10):1828-1834
Ozonation on the phenols present in pyrolytic aqueous phases attained from biomass thermochemical conversion was evaluated. During ozonation, the dark color of original samples was found to decrease as a function of ozonation time. The oxidation kinetics of phenols was quantified by a method based on the color changes of samples. The oxidation profiles showed different behaviors and in some cases the phenols presented a positive correlation with the relative R color parameter, except eugenol, syringol, and vanillin which were markedly different. Finally, the color changes observed seem to be associated with the changes in the overall content of phenols and with the change in the molecular weight of the heavy fractions that include lignin oligomers. 相似文献
94.
Amanda Siwik Erica Pensini Braulio Macias Rodriguez Alejandro G. Marangoni Christopher M. Collier Brent Sleep 《应用聚合物科学杂志》2020,137(11):48465
This study investigated the potential effect of shear rheology and humic acids (HA) on the subsurface transport of polymeric fluids used for the remediation of contaminants. Polymeric fluids were prepared with guar, scleroglucan, and carboxymethyl cellulose (CMC). Guar fluids can be used to suspend reactive particles for contaminant degradation. Fluids prepared with 2.5 g/L of guar in water were viscous, and the crosslinker borax (1 g/L) made them viscoelastic. Microfluidics experiments showed that the increase in elasticity blocked the flow of guar in 350 μm channels. Guar, CMC, or scleroglucan fluids containing sodium thiosulfate can be used to trap toxic Cr(VI) in the subsurface and reduce it to harmless Cr(III). Trapping of Cr(VI) is achieved by the gelation of the fluids upon contact with chromium. Before mixing with chromium, HA did not affect the flow of CMC, guar, and scleroglucan in microfluidic channels. Quartz-crystal microbalance with dissipation monitoring experiments indicates that HA reduced sorption of guar onto silica, potentially promoting the transport of guar fluids in sandy aquifers. While HA slightly decreased the rate of gelation of CMC and scleroglucan upon contact with chromium, it did not affect the fast gelation rate of guar. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48465. 相似文献
95.
Taste perception and purchase intent of oil‐in‐water spreads: effects of oil types and salt (NaCl or KCl) concentrations 下载免费PDF全文
Wilfredo Alejandro Cerrato Rodriguez Damir Dennis Torrico Luis Fernando Osorio Jorge Cardona Witoon Prinyawiwatkul 《International Journal of Food Science & Technology》2017,52(10):2138-2147
Associations of sodium intake with heart‐related problems are creating awareness towards reducing sodium. Potassium chloride (KCl), a substitute for sodium chloride (NaCl), has the disadvantage of imparting bitterness at high concentrations. We evaluated physical characteristics, taste perception and purchase intent of KCl and NaCl in oil‐in‐water spreads/emulsions composed by olive, rice bran and soya bean oils. Consumers (N = 300) evaluated saltiness/bitterness of emulsions prepared with 65% oil, and NaCl (0.5% and 1.0%) or KCl (0.75% and 1.5%). Olive oil spreads (104.07–107.43 Pa s) had higher viscosity compared to other spreads (59.16–74.96 Pa s). Type of oil had significant effects on bitterness, overall taste liking and viscosity. Taste liking decreased due to bitterness of olive oil spreads (mean drop=1.72–2.43). Purchase intent was positively associated with saltiness and pH and increased with oil claims (increase = 1.3%–22.1%) compared to sodium claims (increase = 0.0%–12.9%). These findings are useful for understanding taste perception of emulsions. 相似文献
96.
Solution to indeterminate multipoint impact with frictional contact using constraints 总被引:1,自引:0,他引:1
This work presents a method for determining the post-impact behavior of a rigid body undergoing multiple, simultaneous impact with friction. A discrete algebraic model is used with an event-driven function which finds impact events. In this work, the indeterminate nature of the equations of motion encountered at impact is examined. Velocity constraints are developed based on the rigid body assumption to address the equations and an impact law is used to determine the impulsive forces. The slip-state of each impact point is then determined and appropriate methods are used to resolve the post-impact velocities. These techniques are applied to a 3-D model of a ball which is forced to impact a corner between the ground and two wall planes. Additionally, a rocking block example is considered. Simulations are presented for 2-D and 3-D cases of the ball example, and a 2-D model of the rocking block problem to demonstrate the effectiveness of the proposed approach. 相似文献
97.
98.
N. Keleshian R. Kyser J. Rodriguez C. Cueva V. Vega E. W. Lee J. Ogren O. S. Es-Said 《Journal of Materials Engineering and Performance》2011,20(7):1230-1234
The objective of this study is to determine the effect of solution treatment temperature, quenching media, and various machining
sequences on the warpage behavior of aluminum 7249 alloy aged to T6 and T7′ tempers. Large extrusions of 7249 aluminum alloy
with fins were cut into 108 “T” sections. The samples were solution-treated, aged, and machined. Three solution temperatures
(445, 474, and 505 °C), two quenching media (water and 20% polyalkylene glycol), two aging treatments (T6 and T7′), and three
machine sequences were used. The flatness of the samples was measured on the surfaces orthogonal to the z-axis. Three points were on top of both shoulders (six total), six were at the bottom of the sample, and six were on the top
of the fin, in the cases where the fin was not milled off. They were then averaged together by surface to represent the overall
warpage of each sample. 相似文献
99.
K.S. Mohandas N. Sanil M. Noel P. Rodriguez 《Journal of Applied Electrochemistry》2001,31(9):997-1007
The anodic behaviour of compacted graphite, graphite powder, glassy carbon and reticulated vitreous carbon electrodes in basic sodium chloroaluminate melt in the temperature range 428–573 K was studied using cyclic voltammetry. Chlorine evolution (> + 2.1 V vs Al) alone was the predominant reaction on the compact glassy carbon and fresh RVC electrodes. On compacted graphite, chlorine-assisted chloroaluminate intercalation was found to be a competitive process to the chlorine evolution. At high sweep rates, intercalation/deintercalation near the graphite lattice edges occur faster than chlorine evolution. Subsequent intercalation, however, is a slow process. Chlorine evolution predominates at higher temperatures and at higher anodic potentials. On graphite powders, a more reversible free radical chlorine adsorption/desorption process also occurs in the potential region below chlorine evolution. The process occurs at the grain boundaries, edges and defects of the graphite powder material. Intercalation/deintercalation processes are mainly responsible for the disintegration of graphitic materials in low-temperature chloroaluminate melts. Repeated intercalation/deintercalation cycles result in the irreversible transformation of the electrode surface and electrode characteristics. The surface area of the electrode is increased substantially on cycling. Electrode materials and operating conditions suitable for chlorine generation, intercalation/deintercalation and chlorine adsorption/desorption and power sources based on these processes are identified in this work. 相似文献
100.
Patricia Bautista Angel F. Mohedano Jose A. Casas Juan A. Zazo Juan J. Rodriguez 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2011,86(4):497-504
BACKGROUND: A highly stable Fe/γ‐Al2O3 catalyst for catalytic wet peroxide oxidation has been studied using phenol as target pollutant. The catalyst was prepared by incipient wetness impregnation of γ‐Al2O3 with an aqueous solution of Fe(NO3)3· 9H2O. The influence of pH, temperature, catalyst and H2O2 doses, as well as the initial phenol concentration has been analyzed. RESULTS: The reaction temperature and initial pH significantly affect both phenol conversion and total organic carbon removal. Working at 50 °C, an initial pH of 3, 100 mg L?1 of phenol, a dose of H2O2 corresponding to the stoichiometric amount and 1250 mg L?1 of catalyst, complete phenol conversion and a total organic carbon removal efficiency close to 80% were achieved. When the initial phenol concentration was increased to 1500 mg L?1, a decreased efficiency in total organic carbon removal was observed with increased leaching of iron that can be related to a higher concentration of oxalic acid, as by‐product from catalytic wet peroxide oxidation of phenol. CONCLUSION: A laboratory synthesized γ‐Al2O3 supported Fe has shown potential application in catalytic wet peroxide oxidation of phenolic wastewaters. The catalyst showed remarkable stability in long‐term continuous experiments with limited Fe leaching, < 3% of the initial loading. Copyright © 2010 Society of Chemical Industry 相似文献