全文获取类型
收费全文 | 1874篇 |
免费 | 105篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 78篇 |
综合类 | 34篇 |
化学工业 | 875篇 |
金属工艺 | 20篇 |
机械仪表 | 15篇 |
建筑科学 | 36篇 |
矿业工程 | 4篇 |
能源动力 | 99篇 |
轻工业 | 14篇 |
水利工程 | 1篇 |
石油天然气 | 20篇 |
无线电 | 47篇 |
一般工业技术 | 84篇 |
冶金工业 | 20篇 |
原子能技术 | 591篇 |
自动化技术 | 58篇 |
出版年
2023年 | 12篇 |
2022年 | 18篇 |
2021年 | 25篇 |
2020年 | 26篇 |
2019年 | 53篇 |
2018年 | 38篇 |
2017年 | 32篇 |
2016年 | 37篇 |
2015年 | 29篇 |
2014年 | 46篇 |
2013年 | 535篇 |
2012年 | 57篇 |
2011年 | 157篇 |
2010年 | 69篇 |
2009年 | 85篇 |
2008年 | 70篇 |
2007年 | 70篇 |
2006年 | 74篇 |
2005年 | 82篇 |
2004年 | 49篇 |
2003年 | 43篇 |
2002年 | 38篇 |
2001年 | 34篇 |
2000年 | 15篇 |
1999年 | 40篇 |
1998年 | 32篇 |
1997年 | 35篇 |
1996年 | 20篇 |
1995年 | 15篇 |
1994年 | 7篇 |
1993年 | 13篇 |
1992年 | 17篇 |
1991年 | 15篇 |
1990年 | 11篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1987年 | 19篇 |
1986年 | 13篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有1996条查询结果,搜索用时 0 毫秒
91.
N. O. Ardiaca S. P. Bressa J. A. Alves O. M. Martínez G. F. Barreto 《Catalysis Today》2001,64(3-4):205-215
A study of the liquid-phase hydrogenation of 1,3-butadiene on commercial Pd/Al2O3 catalysts of the “egg-shell” type has been performed. Experimental conditions (40°C, 4 atm and high conversion of the di-olefin) were selected in accordance to industrial operating conditions employed for selective hydrogenation of 1,3-butadiene. Three experimental schemes were tested: a slurry reactor, a rotating-basket reactor, and a recirculation system with an external fixed-bed reactor. Significant drawbacks shown by the two former devices were mainly derived from the very high activity and the egg-shell structure of the catalysts. Instead, the recirculation system was found to be an excellent alternative.
Although Pd is present only within a very thin external layer (around 50–250 μm), strong diffusion effects impairing selectivity were observed. Plausible kinetic expressions corresponding to nine series–parallel overall reactions are derived from a mechanistic model. To deal with this network of fast reactions, a rather complex set of computational and predictive tools were employed. A worked out example from several replicates demonstrates the capability of both, experimental and data analysis procedures, for inferring kinetic parameters of the proposed model. 相似文献
92.
Propane dehydrogenation on a commercial Pt-Sn/Al2O3 catalyst in a Pd-Ag membrane reactor is considered. A mathematical model is developed to evaluate the performance of the catalytic membrane reactor for the process of propane dehydrogenation. Design and operating conditions are systematically evaluated for key performance metrics such as propane conversion, propylene selectivity, hydrogen selectivity, and hydrogen recovery under different operating conditions. The results confirm that the high performance of the membrane reactor is related to the continuous removal of hydrogen from the reaction zone to shift the reaction equilibrium towards the formation of more propylene and hydrogen. 相似文献
93.
Experimental study of oscillation behaviors in confined impinging jets reactor under excitation 下载免费PDF全文
Wei‐Feng Li Wen‐Wei Qian Guang‐Suo Yu Hai‐Feng Liu Fu‐Chen Wang 《American Institute of Chemical Engineers》2015,61(1):333-341
Dynamic behaviors in a three‐dimensional confined impinging jets reactor (CIJR) under excitation were experimentally studied by a flow visualization technique at 75 ≤ Re ≤ 150. The effects of inlet Reynolds numbers (Re), excitation frequencies and excitation amplitudes on the oscillation behaviors in CIJR have been investigated by a particle image velocimetry (PIV) and a high‐speed camera. Results indicate that the excitation in the inflow of the opposed jets can induce periodic oscillation of the impingement plane along the axis, whose oscillation frequency is equal to the excitation frequency. At Re ≤ 100, the induced axial oscillation can further cause a deflective oscillation with a frequency nearly equal to the excitation, and the scale of the vortex in the impingement plane is well regulated by the excitation frequency. At Re = 150, the excitation of amplitude less than 20% has insignificant effect on the deflective oscillation existing in CIJR. A semiempirical formula has been proposed to predict the oscillation amplitude of the impingement plane in CIJR under excitation. © 2014 American Institute of Chemical Engineers AIChE J, 61: 333–341, 2015 相似文献
94.
The impeller configuration with a six parabolic blade disk turbine below two down-pumping hydrofoil propellers, identified as PDT + 2CBY, was used in this study. The effect of the impeller diameter D, ranging from 0.30T to 0.40T (T as the tank diameter), on gas dispersion in a stirred tank of 0.48 m diameter was investigated by experimental and CFD simulation methods. Power consumption and total gas holdup were measured for the same impeller configuration PDT + 2CBY with four different D/T. Results show that with D/T increases from 0.30 to 0.40, the relative power demand (RPD) in a gas–liquid system decreases slightly. At low superficial gas velocity VS of 0.0078 m·s-1, the gas holdup increases evidently with the increase of D/T. However, at high superficial gas velocity, the systemwith D/T=0.33 gets a good balance between the gas recirculation and liquid shearing rate, which resulted in the highest gas holdup among four different D/T. CFD simulation based on the two-fluid model along with the Population Balance Model (PBM) was used to investigate the effect of impeller diameter on the gas dispersion. The power consumption and total gas holdup predicted by CFD simulation were in reasonable agreement with the experimental data. 相似文献
95.
96.
97.
98.
An experimental study was conducted on the liquid‐liquid extraction of isobutyric acid by means of cumene from its aqueous solutions in an air‐operated impinging streams contactor (AOISC) with spray nozzles. Aqueous and organic streams may or may not contact one another inside the spray nozzles depending on the modes of operation. The overall volumetric mass transfer coefficient, KLa, determined enabled us to evaluate the performance capability of the contactor. The effects of air and solution flow rates, contactor length and diameter, impingement zone as well as modes of operation have been investigated. These experimental results verify the capability of the method of impinging streams in liquid‐liquid extraction. 相似文献
99.
The mean flow field in a tank stirred with a pitched blade turbine was measured using a two-component Laser Doppler Anemometer system (LDA). The effects of impeller clearances and impeller geometries (number of blades, blade angle and blade size) on the mean flow field have been studied. The primary pumping number, induced pumping number of the primary circulation loop and the induced pumping number of the secondary circulation loop, which often has been ignored, are reported. The flow patterns and circulation loops are more complex than those traditional ones, which vary with the geometries of the PTD and the clearances. 相似文献
100.
Dynamic Matrix Control of a Bubble‐Column Reactor for Microbial Synthesis Gas Fermentation 下载免费PDF全文
A spatiotemporal metabolic model of a representative syngas bubble‐column reactor was applied to design and evaluate dynamic matrix control (DMC) schemes for regulation of the desired by‐product ethanol and the undesired by‐product acetate. This model was used to develop linear step response models for controller design and also served as the process in closed‐loop simulations. A 2 × 2 DMC scheme with manipulation of the liquid and gas feed flows to the column provided a superior performance to proportional integral (PI) control due to slow process dynamics combining the multivariable and constrained nature of the control problem. Ethanol concentration control for large disturbances was further improved by adding the flow of a pure hydrogen stream as a third manipulated variable. The advantages of DMC for syngas bubble‐column reactor control are demonstrated and a design strategy for future industrial applications is provided. 相似文献