全文获取类型
收费全文 | 802篇 |
免费 | 39篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 13篇 |
化学工业 | 204篇 |
金属工艺 | 35篇 |
机械仪表 | 31篇 |
建筑科学 | 4篇 |
矿业工程 | 3篇 |
能源动力 | 74篇 |
轻工业 | 40篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 78篇 |
一般工业技术 | 212篇 |
冶金工业 | 71篇 |
自动化技术 | 73篇 |
出版年
2024年 | 4篇 |
2023年 | 14篇 |
2022年 | 33篇 |
2021年 | 51篇 |
2020年 | 42篇 |
2019年 | 25篇 |
2018年 | 40篇 |
2017年 | 49篇 |
2016年 | 31篇 |
2015年 | 26篇 |
2014年 | 56篇 |
2013年 | 73篇 |
2012年 | 43篇 |
2011年 | 47篇 |
2010年 | 48篇 |
2009年 | 33篇 |
2008年 | 36篇 |
2007年 | 29篇 |
2006年 | 23篇 |
2005年 | 13篇 |
2004年 | 10篇 |
2003年 | 15篇 |
2002年 | 10篇 |
2001年 | 12篇 |
2000年 | 6篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 5篇 |
排序方式: 共有847条查询结果,搜索用时 15 毫秒
1.
Investigation on the miniaturized parallel multichannel-based devices packed with glass beads to improve the mass exchange execution is the critical focal point of the current study. One of the essential parameters to specify the miniaturized devices' flow distribution is the residence time distribution (RTD). In the present context, the RTDs of a liquid tracer were investigated for the air-water multiphase flows (concurrent) across the multichannel-based miniaturized devices (comprising of 11 similar dimensional parallel channels). The devices were variable in height and packed with glass beads. The conductivity estimations generated the RTD curves and were addressed by the axial dispersion model (ADM). The fluid-flow rates differed within the range of 5–23 ml min−1. The axial dispersion coefficients and the rate of the specific energy dispersion were investigated. The effects of pressure difference and geometry on the hydrodynamic attributes and mixing properties were well-illustrated, and the new correlations were suggested. 相似文献
2.
3.
Chinh Ngo Radhika Mehta Kanchan Aggarwal Audrey G. Fikes Dr. Ines C. Santos Dr. Sylvester M. Greer Prof. Dr. Emily L. Que 《Chembiochem : a European journal of chemical biology》2019,20(8):1003-1007
One-third of all proteins are estimated to require metals for structural stability and/or catalytic activity. Desthiobiotin probes containing metal binding groups can be used to capture metalloproteins with exposed active-site metals under mild conditions so as to prevent changes in metallation state. The proof-of-concept was demonstrated with carbonic anhydrase (CA), an open active site, Zn2+-containing protein. CA was targeted by using sulfonamide derivatives. Linkers of various lengths and structures were screened to determine the optimal structure for capture of the native protein. The optimized probes could selectively pull down CA from red blood cell lysate and other protein mixtures. Pull-down of differently metallated CAs was also investigated. 相似文献
4.
Sonika Sahu Mohd. Zahid Ansari Dehi Pada Mondal Chongdu Cho 《Materials Science & Technology》2019,35(7):856-864
In this paper, cenosphere particles embedded in AA2014 aluminium matrix are used to fabricate syntactic foam by stir casting method. The particle size is about 100?µm and foam density is about 1990?kg?m?3. Compression tests at strain rate 0.001/s are performed on foam samples to characterise their mechanical properties which are then used in numerical analysis on commercial finite element analysis software ABAQUS/CAE with isotropic elastic-plastic material model. Experimental and numerical results show good conformity in deformation behaviour with elastic and plateau zones showing average deviations less than 5% and 20%, respectively. Foams showed high yield stress and energy absorption capabilities that can be useful in making blast and impact resistant structures. 相似文献
5.
6.
7.
The hydraulic resistance of polyurethane foams is studied by means of simulations of water penetration into model foams. The model foams of cubical shape are constructed by generating the centers of the cells randomly. The strength of the window separating two cells is assumed to be a function of the distance between the centers of the cells in one set of computations. In another set of computations the strengths of the windows are assigned randomly from a specified distribution. The foam is exposed to an elevated pressure at its boundaries and water penetrates into the foam by rupturing the windows with strengths lesser than the applied pressure. The variation of equilibrium volume fraction of the foam filled with water for increasing hydraulic pressures shows typical percolation behavior: there is a sharp increase in the volume filled beyond a threshold pressure. Simulations show that beyond a certain sample size there is no change in the percolation curve with sample size, and indicate that it is mainly the weaker windows that control the hydraulic resistance of the foam. The simulation results are compared with experimental data. POLYM. ENG. SCI. 46:970–983, 2006. © 2006 Society of Plastics Engineers 相似文献
8.
The deformation behavior of several single- and two-phase coarse microstructures has been examined using microhardness measurements.
It has been found that the strength response of a coarse phase in isolation is distinctly different from its response when
it exists in a two-phase system. The second phase alters the mechanical state of the first one andvice versa even in the plastically undeformed condition. This phenomenon is explained in terms of the existence of an appreciable amount
of residual stresses in two-phase coarse microstructures. These stresses primarily arise due to the difference in thermal
expansion coefficients of the phases. The in- fluence of elastic stress field on microhardness response is shown with a new
type of experiment to support the proposed explanation. The present results question the existing expressions for deformation
modeling of multiphase materials because of the uncertainties in the estimation of the average strength of the phases in a
two-phase system. 相似文献
9.
The issues in synchronised implementation of space vector-based pulse width modulation (SVPWM) signal generation are addressed on a conventional DSP platform. With the present day digital signal processors (DSPs) with clock over 10 MHz, it is possible to include additional tasks for synchronisation in the interrupt service routine (ISR). Also, the task of the synchronisation can be easily accommodated within the same ISR without disturbing the time critical pulse width modulation (PWM) operation. The authors systematically present the additional software requirements to determine the time period proportional to the half carrier switching time interval that is required for the synchronisation. First, the DSP implementation of the conventional multi-level SVPWM based on the sampled amplitudes of reference voltages is presented and then the additional requirements to maintain the PWM in synchronisation are discussed. The simulation results as well as experimental results are presented for a five-level PWM signal generation. A five-level inverter configuration, using a 1.5 kW open-end winding induction motor drive, is used for experimentally verifying the SVPWM 相似文献
10.
Electrical conduction in non-metallic rare-earth solids 总被引:1,自引:0,他引:1
Schematic energy band diagrams for the genesis of charge carriers in non-metallic rare-earth solids have been presented. It has been shown that positions of 4f bands have significant effect on the genesis and nature of charge carriers, their conduction mechanism and magnitude of electrical conductivity () and Seebeck coefficient (S) of the solid. Relevant relations have been given for both and S in different situations. Experimental data on rare-earth sesquioxides (R2O3), rare-earth tungstates [R2(WO4)3] and rare-earth molybdates [R2(MoO4)3] in the intrinsic range have been explained as examples for the validity of energy band diagrams. 相似文献