全文获取类型
收费全文 | 2871篇 |
免费 | 186篇 |
国内免费 | 28篇 |
专业分类
电工技术 | 56篇 |
综合类 | 14篇 |
化学工业 | 646篇 |
金属工艺 | 69篇 |
机械仪表 | 115篇 |
建筑科学 | 142篇 |
矿业工程 | 4篇 |
能源动力 | 201篇 |
轻工业 | 196篇 |
水利工程 | 44篇 |
石油天然气 | 33篇 |
无线电 | 271篇 |
一般工业技术 | 463篇 |
冶金工业 | 180篇 |
原子能技术 | 28篇 |
自动化技术 | 623篇 |
出版年
2024年 | 9篇 |
2023年 | 53篇 |
2022年 | 103篇 |
2021年 | 181篇 |
2020年 | 156篇 |
2019年 | 186篇 |
2018年 | 182篇 |
2017年 | 178篇 |
2016年 | 168篇 |
2015年 | 119篇 |
2014年 | 194篇 |
2013年 | 295篇 |
2012年 | 212篇 |
2011年 | 239篇 |
2010年 | 157篇 |
2009年 | 149篇 |
2008年 | 88篇 |
2007年 | 46篇 |
2006年 | 58篇 |
2005年 | 45篇 |
2004年 | 26篇 |
2003年 | 26篇 |
2002年 | 29篇 |
2001年 | 18篇 |
2000年 | 14篇 |
1999年 | 16篇 |
1998年 | 22篇 |
1997年 | 13篇 |
1996年 | 12篇 |
1995年 | 12篇 |
1994年 | 6篇 |
1993年 | 10篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1975年 | 6篇 |
1974年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有3085条查询结果,搜索用时 15 毫秒
121.
122.
Mir Mohammad Alavi Nikje Amir Bagheri Garmarudi 《Polymer-Plastics Technology and Engineering》2013,52(10):1101-1107
Waste polyurethane rigid foam (PUF) is recycled by the glycolysis process. The recycled product is used in a polyol blend, applied in a new foam formulation. Polyurethane rigid foams formulated by recycled polyols are highly dense compared to rigid foams formulated by virgin polyols. As these foams are mostly used in insulation, they make an extra mass to the main product or system that is insulated. Therefore, it is important to decrease their density as much as possible. Some density modifiers such as starch, sucrose, and REZOL® IL800 were investigated to recognize their effect on PUF's density. 相似文献
123.
Mir Mohammad Alavi Nikje Amir Bagheri Garmarudi Moslem Haghshenas 《Polymer-Plastics Technology and Engineering》2013,52(11):1213-1217
This article reports on the properties of polyurethane rigid foams, which are used as insulating materials. Most polyurethane rigid foams, derived from cellular polymers, are unstable and tend to crack when acted upon by external forces. These foams are classified as a subgroup of cellular polymers, and thus their low stabilization levels can be partly explained by the fact that they contain cells. In these experiments, we attempted to add talc, to polyurethane rigid foams, as a filler, in an attempt to investigate its effect on the physical properties of the constructed foams in both horizontal and vertical directions. Physical and comparative tests were performed on various compositions of polyurethane foam to chart their insulating capabilities, and our comparative analysis indicated that advances had been achieved with respect to some of its properties. 相似文献
124.
Mohammad Riahi Khalil Kooshayan Mohammad Faraji Ghanati 《Polymer-Plastics Technology and Engineering》2013,52(9):907-915
The butt fusion process is one of the most effective processes in welding polyethylene pipes. The heating stage is the most important step in this process. In this investigation, while the main objective was to reduce the final bead's size of the weld, 9 different experiments with different heat and pressure conditions and equal timing for each heating stage were defined. Numerical modeling of Finite Element Method (FEM) of the heating process was carried out in the computer software considering governing physical conditions in the weld to determine heat distribution as well as primary bead geometry. Subsequently, the model was compared with results from experimentations. Cross-cut of the formed primary beads at the end of the heating process were prepared and compared with results from the model. To review final quality of the weld and its mechanical characteristics, all samples were welded under equal pressure conditions. Cross-sections of beads formed at the final stage as well as some samples for tension test and impact test from all welded areas were prepared according to standard for determination of mechanical characteristics and then compared with each other. From mechanical strength perspective, the weld formed in 210°C and 0.18 MPa pressure demonstrated higher values. However, impact strength in the weld formed in 180°C was higher. By reducing pressure in a specified heating process, value of impact energy required to break the piece was reduced. Mechanical strength in heating condition 240°C was lower than all other cases. As for geometry of the formed bead; its size in 180°C and 0.03 MPa pressure in the first stage of the heating process was smaller than other cases. 相似文献
125.
Mehdi Javani Amir Abdolmaleki Amin Nouri Khorasani 《Journal of Adhesion Science and Technology》2013,27(10):975-985
Crosslinking reaction of polymer by ultraviolet (UV) irradiation has been important in industries. In this work, photocrosslinking of styrene–isoprene–styrene (SIS) triblock copolymer in the presence of benzoin photoinitiator and a dimethacrylate monomer as crosslinking agent was investigated. Curing of samples was initiated under UV irradiation. Benzoin was used as photoinitiator because it contains chromophore group that could absorb UV irradiation. Ethylene glycol dimethacrylate (EGDMA) was used as crosslinking agent, since it has alkene functional groups that could react with the alkene group of SIS. ATR-FTIR spectra of samples show that absorption band of double bond at 1500–1600?cm?1 decreases after UV exposure. Increasing the concentration of benzoin (0.1–1?phr) and EGDMA (1–10?phr) leads to an increase in gel content and hardness, while swelling ratio decreases. After 5?min heating at 150?°C, about 20%wt of the unirradiated compound became insoluble, because heating of compound at 150?°C causes crosslinking reaction without any irradiation. 相似文献
126.
Amir Jourak Vilnis Frishfelds T. Staffan Lundström Inga Herrmann Annelie Hedström 《American Institute of Chemical Engineers》2013,59(3):1002-1011
The longitudinal (DL) and transverse (DT) dispersion coefficients in two‐dimensional (2‐D) randomly packed beds of circular particles in a laminar flow regime are derived. A 2‐D discrete system of particles is divided into cells using modified Voronoi diagrams. The relationship between the variation of the stream function and the averaged vorticity is obtained from computational fluid dynamics (CFD) simulations. The whole flow pattern is then obtained by using the principle of energy dissipation rate minimization. The obtained values of DL agree well with 3‐D experimental data for all velocities investigated. At very high velocities, DT in 2‐D appears to be higher than 3‐D experimental data. In addition, the effects of particle‐size distributions, packing structure, and porosity on the DL and DT were studied. One result was that an increase in the width of the particle‐size distribution resulted in higher values of DL and DT at high velocities. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1002–1011, 2013 相似文献
127.
128.
Amir Reza Abbasi Ali Morsali 《Journal of Inorganic and Organometallic Polymers and Materials》2013,23(2):286-292
Nano-structures of AgCl have been prepared by reaction between AgNO3 and KCl under ultrasound irradiation. Particle sizes and morphology of nanoparticle are depending on temperature and reaction time. The effects of these parameters in growth and morphology of the nano-structures have been studied. The solvents have noticeable influences on the morphology of the silver chloride particles. With an increase in the temperature and reaction time, growth toke place on more nuclei. As a result, an increase in temperature and reaction time led to increase of particle size. The physicochemical properties of the nanoparticles were determined by X-ray diffraction and scanning electron microscopy. 相似文献
129.
Fathollah Pourfayaz Seyed-Hassan Jafari Abbas Ali Khodadadi Yadollah Mortazavi Hossein Ali Khonakdar 《Polymer Bulletin》2013,70(8):2387-2398
In this study, polyamide 6 (PA 6)/multi-walled carbon nanotube (MWCNT) nanocomposites were prepared by different solution methods based on phase inversion, drop-casting and simple evaporation processes. Optical microscopy and field emission scanning electron microscopy techniques were used to investigate the dispersion states of the nanotubes in PA 6 matrix. The results indicated that the dispersion state of MWCNTs in the nanocomposites prepared by the phase inversion-based method was better than those in the nanocomposites prepared by the other two methods. Electrical, rheological, differential scanning calorimetry and thermo-gravimetric analysis measurements showed that the PA 6/MWCNTs nanocomposites prepared by the phase inversion-based method had higher electrical conductivity, storage modulus, crystallization temperature and thermal stability in comparison with those prepared by the other two methods, attributed to the better dispersion state of MWCNTs. These results confirmed achievement of a good dispersion state of MWCNTs within PA 6 matrix by the phase inversion-based efficient approach. 相似文献
130.
Mohammad Shirmardi Amir Hossein Mahvi Bayram Hashemzadeh Abolfazl Naeimabadi Ghasem Hassani Mehdi Vosoughi Niri 《Korean Journal of Chemical Engineering》2013,30(8):1603-1608
Synthetic dyes are widely used by several industries to color their products. The discharge of colored wastewater into the hydrosphere causes serious environmental problems. We used functionalized multi wall carbon nanotubes as an adsorbent for the adsorption of cationic dye, malachite green, from aqueous solution. Based on information provided by the Iranian Research Institute of Petroleum Industry, carbon nanotubes are produced using a chemical vapor deposition (CVD) technique. These as-received MWCNTs were functionalized by acid treatment. The remaining dye concentration was read by UV-visible absorption spectroscopy at maximum adsorption wavelength. The effect of different operational parameters such as contact time, pH of solution, adsorbent dose and initial dye concentration were studied. The results showed that by increasing of contact time, pH and adsorbent dose the removal of dye increased, but by increasing initial dye concentration, the removal efficiency decreased. Adsorption isotherms and kinetics behavior of f-MWCNTs for removal of malachite green was analyzed, and fitted to various existing models. The experimental data were well correlated with the Langmuir isotherm with a maximum adsorption capacity (q m ) and regression coefficient (R2) of 142.85 mg/g and 0.997, respectively. The results of this study indicate that functionalized multi wall carbon nanotubes can be used as an effective adsorbent for the removal of dyes. 相似文献