全文获取类型
收费全文 | 1714篇 |
免费 | 120篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 43篇 |
综合类 | 8篇 |
化学工业 | 478篇 |
金属工艺 | 48篇 |
机械仪表 | 79篇 |
建筑科学 | 50篇 |
矿业工程 | 3篇 |
能源动力 | 94篇 |
轻工业 | 154篇 |
水利工程 | 38篇 |
石油天然气 | 21篇 |
武器工业 | 2篇 |
无线电 | 132篇 |
一般工业技术 | 311篇 |
冶金工业 | 68篇 |
原子能技术 | 17篇 |
自动化技术 | 304篇 |
出版年
2024年 | 4篇 |
2023年 | 56篇 |
2022年 | 91篇 |
2021年 | 131篇 |
2020年 | 111篇 |
2019年 | 126篇 |
2018年 | 136篇 |
2017年 | 115篇 |
2016年 | 117篇 |
2015年 | 81篇 |
2014年 | 94篇 |
2013年 | 158篇 |
2012年 | 122篇 |
2011年 | 99篇 |
2010年 | 75篇 |
2009年 | 76篇 |
2008年 | 45篇 |
2007年 | 41篇 |
2006年 | 29篇 |
2005年 | 11篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 10篇 |
2001年 | 2篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1998年 | 18篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有1850条查询结果,搜索用时 15 毫秒
81.
Railway Engineering Science - Congestion pricing is seen as an effective policy to address traffic congestion. In such policies where money, people and authorities are involved, the success... 相似文献
82.
Saeed Farahany Ali Ourdjini Tuty Asma Abu Bakar Mohd Hasbullah Idris 《Metallurgical and Materials Transactions A》2014,45(3):1085-1088
Obtained results of micro and nano studies reveal that bismuth refines the silicon in which the flake silicon changed to lamellar structure with reduction in twin spacing from 160 to 75 nm. Bismuth segregates towards the inter-dendritic regions and decreases the Al-Si contact angle resulting in suppression of the silicon growth causing refinement of the eutectic structure. Increased recalescence temperature and time confirmed that the refinement effect is attributed to the growth stage. 相似文献
83.
Mohammad Reza Foroughi Saeed Karbasi Maryam Khoroushi Abbas Ali Khademi 《Journal of Porous Materials》2017,24(6):1447-1460
Scaffolds and their features play a central role in tissue engineering; so this study is based on the production of a series of electrospun PHB/Chitosan/nBG nanocomposite scaffolds with 9 wt% polyhydroxybutyrate, 10, 15 and 20 wt% chitosan and 7.5, 10 and 15 wt% nanobioglass (nBG). Electrospinning process was performed with optimal conditions of spinning machine including voltage of 16 kV, syringe-collector spacing of 16 cm, and output rate of 1 µl per hour. The developed phases and the formation of chemical bonds between ceramic and polymer bands were studied through XRD and FTIR analyses. The FE-SEM and TEM analyses showed uniform morphology of nanofibers and dispersion of bioglass nanoparticles in the fiber structure. The presence of 10 wt% bioglass nanoparticles and 15 wt% chitosan increased the tensile strength of fibers to 3.42 MPa, which was about four times greater than strength of control sample (pure PHB). The developed fibers were kept 28 days in SBF solution and 60 days in PBS solution to assess their bioactivity and biodegradability. The results showed that the presence of bioglass nanoparticles leads to a dramatic increase in absorption of calcium and phosphorus ions and weight loss of scaffold. The developed scaffold can be used for bone and teeth tissue engineering applications. 相似文献
84.
85.
Akram Shahrjerdi Saied Saeed Hosseiny Davarani Mostafa Mohammadpour Amini Ezzatollah Najafi Mohammad Janghouri Ezeddine Mohajerani Aziz Dehpour 《Journal of Materials Science》2014,49(1):441-449
A new lead complex, [Pb(mq)2], (mq = 2-methyl-8-hydroxyquinoline) was prepared via an electrochemical route from the oxidation of lead metal in the presence of 2-methyl-8-hydroxyquinoline in a fast and facile process. The complex was fully characterized by means of NMR and IR spectra and elemental analysis. The nanostructure of the prepared compound was obtained by sonoelectrochemical process and studied by scanning electron microscopy, atomic force microscopy, X-ray powder diffraction, IR spectroscopy and elemental analysis. Thermal stability of single crystalline and nanosize samples of the prepared compound was studied by thermal gravimetric and differential thermal analysis. The photoluminescence properties of the prepared compounds, as single crystals and as nanorods, have been investigated. The results showed a good correlation between the size and the shape of the complex particles and emission wavelength. The prepared complex was doped in PVK:PBD blend as guest and its application in the fabrication of OLED was studied. The ratio of lead complex was modified and was equal to 8 (w/w %) in PVK:PBD (100:40). 相似文献
86.
Saeed Hajimirzaee Mohammad Ghavipour Mohammad Vatankhah Reza Mosayebi Behbahani 《Petroleum Science and Technology》2017,35(3):279-286
Effect of ZSM-5 zeolite promotion using potassium, strontium, and cerium metals on conversion of methanol to light olefins and aromatics was investigated. ZSM-5 catalyst was promoted using wet impregnation of metal salts and its activity was tested in methanol to hydrocarbons process under optimum operational condition obtained in our group previously. Zeolite samples were characterized by X-ray powder diffraction, scanning electron microscopy, N2 adsorption-desorption, acid sites distribution, and strength using temperature programmed desorption of NH3. Results showed that presence of these metals could significantly affect acid site distribution and therefore influence the catalyst activity and selectivity to olefins and aromatics. 相似文献
87.
Effect of various efficient vulcanization (EV) sulfur cure systems on the compression set of a nitrile rubber filled with carbon black and silica/silane fillers was examined. The cure systems had different amounts of thiuram and sulfenamide accelerators and elemental sulfur, whilst the loading of zinc oxide and stearic acid activators was kept constant. The fillers had surface areas from 35 to 175 m2/g. In this study, the lowest compression set was measured for the rubber filled with carbon black with 78 m2/g surface area, which was cured with an EV cure system made of a small amount of elemental sulfur and large amounts of the two accelerators. Interestingly, a small change in the amount of elemental sulfur had a bigger effect on the compression set than did large changes in the loading of the accelerators in the cure system. Among the fillers, carbon black caused less compression set of the rubber vulcanizate than the silica/silane system did. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41512. 相似文献
88.
89.
90.
Kai LONG Xiaoyu YANG Nouman SAEED Ruohan TIAN Pin WEN Xuan WANG 《Frontiers of Mechanical Engineering》2021,16(3):593-606
Frontiers of Mechanical Engineering - This paper proposes a novel method for the continuum topology optimization of transient vibration problem with maximum dynamic response constraint. An... 相似文献