全文获取类型
收费全文 | 530篇 |
免费 | 30篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 144篇 |
金属工艺 | 16篇 |
机械仪表 | 17篇 |
建筑科学 | 20篇 |
矿业工程 | 1篇 |
能源动力 | 8篇 |
轻工业 | 38篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 39篇 |
一般工业技术 | 100篇 |
冶金工业 | 60篇 |
原子能技术 | 1篇 |
自动化技术 | 111篇 |
出版年
2023年 | 7篇 |
2022年 | 16篇 |
2021年 | 22篇 |
2020年 | 6篇 |
2019年 | 17篇 |
2018年 | 8篇 |
2017年 | 11篇 |
2016年 | 22篇 |
2015年 | 25篇 |
2014年 | 25篇 |
2013年 | 38篇 |
2012年 | 35篇 |
2011年 | 32篇 |
2010年 | 29篇 |
2009年 | 22篇 |
2008年 | 25篇 |
2007年 | 29篇 |
2006年 | 18篇 |
2005年 | 18篇 |
2004年 | 9篇 |
2003年 | 18篇 |
2002年 | 17篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 11篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 8篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1971年 | 2篇 |
1957年 | 1篇 |
1955年 | 1篇 |
1954年 | 2篇 |
1924年 | 2篇 |
1923年 | 1篇 |
排序方式: 共有560条查询结果,搜索用时 15 毫秒
461.
462.
463.
Daniel J. Lege Frederic Barlat John C. Brem 《International Journal of Mechanical Sciences》1989,31(7)
A 2008-T4 sheet sample has been characterized and its mechanical behavior and formability have been modeled. Uniaxial tensile and equal biaxial tensile stress-strain data, compressive yield strengths, crystallographic texture, earing and the forming limit curve were experimentally determined. Bulge test specimen shape and thickness profiles were also measured after various amounts of biaxial strain. A recently developed phenomenological constitutive model of anisotropic mechanical behavior was used to predict the directionality of strength, plastic strain ratio (R) and shear strain ratio (Г) values. In addition, this model was used to predict the forming limit curve for this sample. Predictions made with the recent model generally compare favorably with experimental results and with predictions made using the Taylor/Bishop and Hill theory. According to the data obtained in hydraulic bulge testing, the 2008-T4 exhibited apparent isotropic behavior. However, in cup drawing—another axisymmetric deformation mode—this material exhibited anisotropic behavior, as indicated by the formation of ears and troughs. 相似文献
464.
David Frederic Emerson Amir Al Ghatta Benjamin M. Woolston Adrian Fay Amit Kumar Gregory Stephanopoulos 《American Institute of Chemical Engineers》2017,63(9):3642-3650
Current natural gas harvesting technologies are only economically viable at high gas flow rates. Subsequently, a significant quantity of gas remains unused in abandoned wells. Methanotrophic organisms are under development to capitalize on this resource given their preference for ambient conditions, however capital and methane mass transfer costs must be minimized. We propose using the well as the bioreactor negating capital costs, and leveraging the gas pressure for mass transfer. We evaluate the Deep Well Reactor's feasibility by developing mathematical models to simulate mass transfer and explore how operating parameters impact ethanol production. The results show sufficient mass transfer for 100% conversion, despite minimal complexity. Current aerobic methanotrophs and inorganic catalysts provide sufficient reaction rates. Conversely, anaerobic methanotrophs rates must be improved by a factor of 1200. With an appropriate catalyst, this technology allows the recovery of methane at flow rates an order of magnitude lower than current technologies. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3642–3650, 2017 相似文献
465.
Amir Bazrafshan Mohammad Taherzadeh-Sani Frederic Nabki 《Analog Integrated Circuits and Signal Processing》2013,76(2):245-249
A digital background calibration technique to estimate the sample-time error (timing-skew) in time-interleaved ADCs is presented. Compared to the state-of-the-art, this technique requires a simpler digital block and, hence, a lower power dissipation. The proposed technique detects timing skew for each channel by means of finding zero-crossing samples with respect to a reference comparator. Simulation results show that it can effectively correct timing errors for any type of input signal up to Nyquist, and achieves a high convergence speed with a very low computational complexity. 相似文献
466.
Qingyuan Gu Maud Gicquel-Guézo Slimane Loualiche Julie Le Pouliquen Thomas Batte Hervé Folliot Olivier Dehaese Frederic Grillot Yann Battie Annick Loiseau Baolai Liang Diana Huffaker 《Nanoscale research letters》2013,8(1):300
Among direct-bandgap semiconducting nanomaterials, single-walled carbon nanotubes (SWCNT) exhibit strong quasi-one-dimensional excitonic optical properties, which confer them a great potential for their integration in future photonics devices as an alternative solution to conventional inorganic semiconductors. In this paper, we will highlight SWCNT optical properties for passive as well as active applications in future optical networking. For passive applications, we directly compare the efficiency and power consumption of saturable absorbers (SAs) based on SWCNT with SA based on conventional multiple quantum wells. For active applications, exceptional photoluminescence properties of SWCNT, such as excellent light-emission stabilities with temperature and excitation power, hold these nanometer-scale materials as prime candidates for future active photonics devices with superior performances. 相似文献
467.
Frederic Auger Guillaume Delaplace Laurent Bouvier Andreas Redl Christophe André Marie-Hélène Morel 《Journal of food engineering》2013
The objective of this paper is to better characterize the influence of process parameters (impeller revolution speeds) on the performance of a planetary flour-beater mixer (mixer bowl P600 from Brabender) used in dough production. 相似文献
468.
Oxidation behavior of titanium carbonitride based materials 总被引:2,自引:0,他引:2
The oxidation behavior of two different Ti(C,N)-WC based materials (a ceramic type containing 0.9 wt.% Co and a cermet type containing (6.2Ni+2.9 Co) wt.%), was tested at 900 and 1000 °C in static laboratory air. The values of the mass gain (∼50 mg/cm2 after 100 h at 1000 °C) and extended microstructural modifications demonstrated that these materials are rather unstable under oxidizing conditions. After an initial transitory period where the mass change resulted from the competition between the mass gain due to formation of solid TiO2 and the mass loss due to released volatile tungsten oxides that were formed, the oxidation process obeyed a linear law in function of the exposure time, i.e. it is governed by a chemical reaction at the interface of the titanium based carbonitrides transformed into TiO2. Oxidation kinetics and mechanisms were discussed in terms of the phase composition, presence of metal binder at grain boundaries, and of the residual porosity of the starting materials. 相似文献
469.
The intensity and origin of volume changes under uniaxial tension is investigated at room temperature in high-density polyethylene samples with a large initial degree of crystallinity. At the macroscopic scale, volume strain is defined as the trace of the finite strain tensor whose components are recorded in situ by means of a 2D video extensometer within a representative volume element situated at the center of the neck. At the microscopic scale, volume strain is ascribed to the competition of cohesive mechanisms and non-cohesive mechanisms. The former are associated both to the packing of oriented chains in the amorphous phase (compaction) and to the decrease of crystallinity (dilatation), as characterized by wide-angle X-ray diffraction analysis. The latter are due to the development of crazes and voids (dilatation) while the spherulitic morphology is progressively transformed into a highly fibrillated structure, as revealed by scanning electron microscopy. Detailed evaluation of the relative importance of these two classes of mechanisms shows that they compensate nearly exactly at moderate strains, so that volume strain is very small in the first stage of the tensile tests. By contrast, the effect of cavitation becomes prominent at large deformation, so that the overall dilatation reaches more than 30% before rupture. It is demonstrated that volume strain measurements obtained from mechanical testing and from microstructural investigation agree fairly satisfactorily. 相似文献
470.
Stewart Jonathan W.; Bruder Gerard E.; McGrath Patrick J.; Quitkin Frederic M. 《Canadian Metallurgical Quarterly》2003,112(2):253
Illness course separates patients with atypical depression into tricyclic responders and nonresponders as does perceptual asymmetry. The authors therefore investigated whether the course-of-illness parameters would define groups within atypical depression differing in brain laterality. Patients with atypical depression were assessed for illness course and brain laterality. Two patient groups were defined, 1 with onset prior to age 20 plus a very chronic course, and a 2nd group having later onset or less chronic illness. Patients reporting early onset of very chronic dysphoria showed significantly less right-ear (left-hemisphere) accuracy and also differed in characteristic perceptual asymmetry when compared to patients with later onset or less chronicity. Course of illness may usefully define more homogeneous depressive subgroups within atypical depression. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献