全文获取类型
收费全文 | 3725篇 |
免费 | 180篇 |
国内免费 | 25篇 |
专业分类
电工技术 | 55篇 |
综合类 | 5篇 |
化学工业 | 910篇 |
金属工艺 | 104篇 |
机械仪表 | 102篇 |
建筑科学 | 122篇 |
矿业工程 | 9篇 |
能源动力 | 463篇 |
轻工业 | 330篇 |
水利工程 | 21篇 |
石油天然气 | 63篇 |
无线电 | 309篇 |
一般工业技术 | 659篇 |
冶金工业 | 256篇 |
原子能技术 | 26篇 |
自动化技术 | 496篇 |
出版年
2023年 | 62篇 |
2022年 | 144篇 |
2021年 | 196篇 |
2020年 | 137篇 |
2019年 | 119篇 |
2018年 | 199篇 |
2017年 | 144篇 |
2016年 | 164篇 |
2015年 | 102篇 |
2014年 | 155篇 |
2013年 | 274篇 |
2012年 | 187篇 |
2011年 | 228篇 |
2010年 | 148篇 |
2009年 | 161篇 |
2008年 | 132篇 |
2007年 | 123篇 |
2006年 | 106篇 |
2005年 | 65篇 |
2004年 | 74篇 |
2003年 | 77篇 |
2002年 | 59篇 |
2001年 | 38篇 |
2000年 | 43篇 |
1999年 | 44篇 |
1998年 | 77篇 |
1997年 | 54篇 |
1996年 | 45篇 |
1995年 | 61篇 |
1994年 | 34篇 |
1993年 | 45篇 |
1992年 | 30篇 |
1991年 | 29篇 |
1990年 | 22篇 |
1989年 | 24篇 |
1988年 | 14篇 |
1987年 | 15篇 |
1986年 | 15篇 |
1985年 | 25篇 |
1984年 | 29篇 |
1983年 | 16篇 |
1982年 | 25篇 |
1981年 | 28篇 |
1980年 | 20篇 |
1979年 | 24篇 |
1978年 | 17篇 |
1977年 | 15篇 |
1976年 | 13篇 |
1975年 | 12篇 |
1973年 | 13篇 |
排序方式: 共有3930条查询结果,搜索用时 15 毫秒
991.
Sergey F. Golovashchenko Alan J. Gillard Alexander V. Mamutov Ramy Ibrahim 《Journal of Materials Processing Technology》2014,214(11):2796-2810
Electrohydraulic calibration (EHC) of springback is a novel method of removing springback from stamped sheet metal panels and is based upon the electro-hydraulic effect: a complex phenomenon related to the discharge of high voltage electrical current through a liquid. The EHC process involves clamping a stamped panel against a female die with the desired part shape and then applying several pulses of pressure onto and through the thickness of the sheet, in a process somewhat similar to conventional coining operations. However, in EHC the pressure is applied by a fluid and through the use of the electrohydraulic effect, and not with a matching hard tool as done in coining. In EHC, electrical energy is stored in a bank of capacitors and is converted into kinetic energy within the liquid by rapidly discharging the stored energy across a pair of electrodes submerged in a fluid. The objective of this paper is to describe the newly developed EHC process, to report the results of early proof-of-concept experiments, to present the results of more advanced experiments using a more industrial tool and actual part geometry, and to describe how numerical modeling techniques were used to optimize the design of the larger and more industrial tool. The developed concept of electrohydraulic stress relieving calibration is based upon clamping a stamped panel to the calibration die surface with the target shape and then applying pulses of pressure to eliminate internal stresses in the stamped panel. When a stamped blank is removed from a forming die, allowed to springback, and then clamped to a calibration die, the internal elastic stresses within the panel in such a configuration serve as a memory of the shape of the blank after springback, and it is these residual stresses that EH calibration is intended to remove from the panel. The developed concept of stress relieving calibration was initially validated by a simple experiment consisting of submerging a bent strip of aluminum into the fluid within an EH chamber, so that both the outer and inner surfaces of the strip (where the internal stresses from bending are located) were exposed to the fluid and the pressure pulse. This experiment served as an initial confirmation that impact with the tool is not necessary to achieve the calibration effect. The sheet metal materials used in this study, and for which springback was eliminated after forming, include DP 980 at 1.0 mm and 1.4 mm thick, and also DP600 at 1.0 mm thick. 相似文献
992.
Onion extract (Allium cepa L.), quercetin and catechin up‐regulate paraoxonase 1 activity with concomitant protection against low‐density lipoprotein oxidation in male Wistar rats subjected to oxidative stress
下载免费PDF全文
![点击此处可从《Journal of the science of food and agriculture》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Nidhi Jaiswal Syed Ibrahim Rizvi 《Journal of the science of food and agriculture》2014,94(13):2752-2757
993.
Jillian E. Smith Chen Liang Michael Tseng Noel Li Sha Li Allisandra K. Mowles Anil K. Mehta David G. Lynn 《Israel journal of chemistry》2015,55(6-7):763-769
Structurally defined cross-β assemblies have allowed for the development of basis sets for isotope-edited infrared spectra to follow progressive assembly over time. These basis sets, composed of a minimal number of individual spectra, are sufficient to identify the populations of polymorphs evolving throughout the assembly process. This approach provides, for the first time, the spectral assignment and relative distribution of paracrystalline intermediates formed from the intermolecular molten globule phase where nucleation occurs. Using the basis sets, we can now follow how subtle changes in assembly energetics impact the accessible polymorphs along the assembly pathway. Here, simple methylation of the Gln22 side chain of the nucleating core of the Dutch mutant of the Aβ of Alzheimer’s disease, Aβ(16-22)E22Q, dramatically increases the distribution of sampled polymorphs and slows progression to the final thermodynamic assembly. These data establish that amyloid cross-β structures can assemble through a dynamic conformational phylogeny. This fluid context-dependent network, so accessible to simple peptides, may provide the basis for the conformational selection and evolution of the complex supramolecular assemblies implicated in the many protein misfolding and prion diseases. 相似文献
994.
Meriem Fodil Amine Mounir Mohammed Ameri Hadj Baltache Bachir Bouhafs Y. Al-Douri Ibrahim Ameri 《Materials Science-Poland》2014,32(2):220-227
First-principles calculations of the lattice constants, bulk modulus, pressure derivatives of the bulk modulus and elastic constants of AlN and TiN compounds in rock-salt (B1) and wurtzite (B4) structures are presented. We have used the fullpotential linearized augmented plane wave (FP-LAPW) method within the density functional theory (DFT) in the generalized gradient approximation (GGA) for the exchange-correlation functional. Moreover, the elastic properties of cubic TiN and hexagonal AlN, including elastic constants, bulk and shear moduli are determined and compared with previous experimental and theoretical data. Our results show that the structural transition at 0 K from wurtzite to rock-salt phase occurs at 10 GPa and ?26 GPa for AlN and TiN, respectively. These results are consistent with those of other studies found in the literature. 相似文献
995.
Dr. Israa A. Seliem Dr. Siva S. Panda Prof. Adel S. Girgis Queen L. Tran Dr. Mona F. Said Dr. Mohamed S. Bekheit Prof. Anwar Abdelnaser Soad Nasr Prof. Walid Fayad Dr. Ahmed A. F. Soliman Dr. Rajeev Sakhuja Dr. Tarek S. Ibrahim Prof. Zakaria K. M. Abdel-Samii Dr. Amany M. M. Al-Mahmoudy 《ChemMedChem》2022,17(13):e202200164
Three sets of isatin-based Schiff bases were synthesized utilizing the molecular hybridization approach. Some of the synthesized Schiff bases show significant to moderate antiproliferative properties against MCF7 (breast), HCT116 (colon), and PaCa2 (pancreatic) cancer cell lines with potency compared to reference drugs 5-fluorouracil (5-FU) and Sunitinib. Among all, compound 17 f (3-((1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)imino)-1-((1-(2-methoxyphenyl)-1H-1,2,3-triazol-4-yl)methyl)-5-methylindolin-2-one) exhibits promising antiproliferative properties against the MCF7 cancer cell line with 2.1-fold more potency than Sunitinib. However, among all the synthesized compounds, three (5-methylisatin derivatives) were the most effective against HCT116 in comparison to 5-FU. Compound 17 f exhibited the highest anti-angiogenic effect on the vasculature as it significantly reduced BV from 43 mm to 2 mm in comparison to 5.7 mm for Sunitinib and flow cytometry supports the arrest of the cell cycle at G1/S phases. In addition, compound 17 f also showed high VEGFR-2 inhibition properties against breast cancer cell lines. Robust 2D-QSAR studies supported the biological data. 相似文献
996.
Catalysis Letters - A set of facile room temperature catalytic systems for the oxidation of cyclohexane C–H bonds was developed from in situ generated triazole-functionalised Schiff base... 相似文献
997.
Hassan Abdelrhman Ibrahim Khalifa Mohamed Gamal Meraikib Mohamed Aziz Ahmed Belal Saleh 《Metallurgist》2021,65(1-2):3-12
Metallurgist - The partial and complete replacement of coke breeze with anthracite for sintering Bahariya iron ore at the Egyptian Iron & Steel Company (EISCO) was carried out. The best... 相似文献
998.
Shaban Samy M. Fouda A. S. Rashwan S. M. Ibrahim Hoyeda E. Elbhrawy M. F. 《Protection of Metals and Physical Chemistry of Surfaces》2018,54(4):709-723
Protection of Metals and Physical Chemistry of Surfaces - A new cationic surfactant namely, N-(2-(2-hydroxyethoxy)ethyl)-N,N-dimethylhexadecan-1-ammonium bromide (HEDHB) was prepared and its... 相似文献
999.
Polyether polyols as GPC calibration standards for determination of molecular weight distribution of polyether polyols
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)
Mohd Azmil Mohd Noor Vahid Sendijarevic Hazimah Abu Hassan Ibrahim Sendijarevic Tuan Noor Maznee Tuan Ismail Hoong Seng Soi Nurul ‘Ain Hanzah Razmah Ghazali 《应用聚合物科学杂志》2015,132(43)
Average molecular weights (Mn, Mw and Mp) are important characteristics of oligomers and polymers, and therefore there is a need to have a precise and reliable determination method. A gel permeation chromatography (GPC) coupled with a single refractive index detector was used to determine the molecular weight distributions of commercial polyether polyols calibrated against a series of polyether polyols with known molecular weights and low polydispersity. Results of these GPC analyses were compared to the ones calibrated against the commercially available polystyrene (PS) standards. The number‐average molecular weights (Mn) obtained with GPC using polyether polyols calibration were closer to the theoretical values than the Mn obtained using PS as calibration standards. Hence, these GPC analyses using polyether polyols as calibration standards can provide reliable determination of molecular weight distribution of polyether polyols and can be potentially applied to natural oil‐based polyols, including palm oil‐based polyols. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42698. 相似文献
1000.
Wenzheng Zhai Xiaoliang Shi Ahmed Mohamed Mahmoud Ibrahim Zengshi Xu Qiaoxin Zhang 《Lubrication Science》2016,28(7):407-422
The sliding wear of Ni3Al matrix composites with addition of 1.5 wt.% graphene nanoplates was studied through pin‐on‐disc wear testing. The spontaneous formation of a tribo‐layer produced during sliding wear was found to result in a deviation from Archard scaling and an unexpected high wear resistance that was not based on hardness alone. The tribo‐layer exhibited specific microstructural evolution with significant severe deformation and grain refinement after wear. In the grain refinement area, the accumulation of dislocations and an increase in misorientations were found to lead to strain hardening. For the plastic deformed area, reduction in the dislocation density inside the elongated ultrafine grains reduced strain hardening compared with the grain refinement area. It can be concluded that the deviation from Archard scaling occurred primarily as a result of the microstructural evolution of the tribo‐layer, resulting in the specific performance of mechanical and tribological properties of Ni3Al matrix composites under cyclic sliding wear process. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献