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61.
根据矿井已揭露瓦斯地质参数信息,运用煤与瓦斯突出地质预测方法,结合数量化理论,建立了矿井32煤层瓦斯地质预测模型及瓦斯地质区划预测指标体系,从而提高了瓦斯防治的前瞻性、针对性。 相似文献
62.
Roberta Di Monte Paolo Fornasiero Jan Ka
par Paolo Rumori Giuseppe Gubitosa Mauro Graziani 《Applied catalysis. B, Environmental》2000,24(3-4):157-167
Pd-loaded Ce0.6Zr0.4O2 solid solutions supported on Al2O3 are investigated as catalysts for the reduction of NO by CO. The attention is focused on the role of the Ce0.6Zr0.4O2 and of the Pd dispersion on the catalytic activity. The system shows a very high activity below 500 K, which is almost independent on the Pd dispersion. The high activity is attributed to a promoting effect of the Ce0.6Zr0.4O2 on the NO conversion. Investigation of the influence of high temperature treatments disclosed a thermal stabilisation of both Ce0.6Zr0.4O2 and Al2O3 in the Ce0.6Zr0.4O2/Al2O3 system. 相似文献
63.
文中提出了基于移动激光扫描技术的隧道断面变形检测方法.通过对移动激光扫描车获取的隧道点云数据进行环片提取,并利用改进多边形裁剪算法统计隧道环片的拉伸度及挤压度指标,结合环片各角度形变值综合检测隧道变形状况.采用成都地区的圆形盾构隧道数据进行了方法的验证,实验结果证实了该方法的可行性和有效性. 相似文献
64.
65.
Renaldas Raišutis Rymantas Kažys Egidijus Žukauskas Liudas Mažeika 《NDT & E International》2011,44(7):645-654
In aerospace industry, one of the most important parts of gliders and motor-gliders is a lightweight longeron reinforcement made of carbon fibre reinforced plastics (CFRP) rods, known as Graphlite SM315 composite. During manufacturing, the rods as constructional elements are glued together in epoxy-filled matrix in order to build the arbitrary spar profile. The defects present in single rods such as breakage of fibres, multiple delaminations due to the lack of bonding between fibres and reduction in density affect essentially the strength and the fail-safety of the overall construction.The aim of the present work is to investigate the effects (transmission, reflection, scattering and mode conversion) of guided waves propagation along a square-shape CFRP rod in the case of contactless excitation/reception and interaction with region of multiple delaminations applying the numerical model and performing experiments.The square-shape CFRP composite rods possessing internal artificial delamination type defects have been investigated by numerical modelling and experiments employing the developed air-coupled technique (pitch-catch set-up) for cases of conventional transmission and advanced back-scattering configurations. Numerical predictions of guided wave interaction with a multiple delamination type defect in a CFRP composite rod have been made and the interaction mechanism explained. It is possible to conclude, that the actual sizes of the internal defects have been clearly detected using reception of the back-scattered waves over the edges of the defective regions only. 相似文献
66.
This study presents a methodology for the assessment of photovoltaic potential in urban areas using open-source solar radiation tools and a 3-D city model implemented in a geographic information system (GIS). The solar radiation tools are represented by the r.sun solar radiation model and PVGIS estimation utility. The applicability of the methodology has been demonstrated on a selected urban area of a small city in eastern Slovakia. The relevant attributes of buildings have been mapped and implemented in a GIS database. The selected urban area consists of various urban zones characterized by different morphology and functionality. The photovoltaic potential of buildings has been assessed using the PVGIS estimation utility. The analysis has shown a high photovoltaic potential that could cover about 2/3 of current electricity consumption in the city. However, this potential exhibits large spatial and temporal variations caused by global and local factors. This study has also shown that national assessments of photovoltaic potential can be improved by extrapolation of local assessments using spatial databases of urban areas. 相似文献
67.
A new method for measuring the elastic properties of paper on-line in a paper machine by using ultrasound has been developed. The unique feature of the method is that a continuous stochastic ultrasonic signal is used for measurements, which is generated by means of a dry friction between a running paper web and a rigidly fixed friction head. The signals from the web are picked up by an array of air-coupled ultrasonic receivers, which have no mechanical contact with the paper web. The ultrasound velocity in the web is obtained by means of the correlation processing. By using advanced digital signal processing, the tensile stiffness index (TSI) of the running web is determined. From the sensor we get the TSI values both in the machine direction and the cross-machine direction.The on-line ultrasonic sensors have been installed on two different paper machines for more than two years. This paper describes the background of the method, as well as some experiences and applications from two mill installations. 相似文献
68.
Adequacy of approximation of ellipsoidal particles composed of a set of sub-spheres for numerical Discrete Element Method
(DEM) simulations is examined. The algorithm of adaptive hierarchical multi-sphere (MS) model is suggested for composing elliptical
particles. Numerical simulation of the piling problem is used as a test problem for evaluating the adequacy of MS model approximation
in comparison to the model of smooth ellipses for multiparticle system. The accuracy of MS approximation with the increasing
number of sub-spheres is examined in detail by comparison of macroscopic and microscopic parameters of granular dynamics.
It was determined that the data on macroscopic parameters yielded by the MS model tend to converge to those of the smooth
ellipsoid with the increasing number of the constituent sub-spheres, and the MS model approximates the smooth perfect ellipsoid
with a reasonable number of sub-spheres within the limits of the appropriate tolerance. It can be concluded that a multi-sphere
model remains a realistic and relatively simple particle model applicable to DEM simulations of the behaviour of the real
smooth and rough elliptically shaped particles. 相似文献
69.
By using the discrete element method (DEM) a comparison and observations on material flow patterns in plane-wedged, space-wedged, and flat-bottomed hopper were accounted for. Numerical results obtained by combining data of individual particles, statistical processing of particle assemblies and evaluation of the field variables provided the essential characteristics for different regimes of the discharge flow (within steady or unsteady state of flow) and the differences in differently shaped hoppers due to different microscopic inter-particle friction. For validation of the performed simulations, velocity patterns developed in three-dimensional flat-bottomed hopper containing 20,400 pea grains were also analysed. To represent the continuum by avoiding the local effects produced by the individual grains, the simulation results were focused on the mean velocity distributions with data smoothening. The effect of rolling resistance on granular material flow was also considered. 相似文献
70.
S. Thomas Ng Michael M.Y. Mak R. Martin Skitmore Ka Chi Lam Mark Varnam 《Construction Management & Economics》2013,31(2):165-173
Bromilow's log-log time-cost (BTC) model is tested and refitted with a new set of data for Australian construction projects completed between 1991 and 1998. It is shown that, as anticipated by earlier research, different parameter estimates are needed for different project types, with smaller industrial projects taking less time to complete than the smaller educational and residential projects. This results in the development of two separate models, one for industrial projects and one for non-industrial projects. No changes in parameter estimates are needed for projects with different client sectors, contractor selection methods and contractual arrangements. Alternatives to the log-log model failed to produce any improved fit. Finally, the results are compared with previous work to indicate the extent of changes in time-cost relationships in Australian construction projects over the last 40 years. This indicates a clear improvement in construction speed over the period. Furthermore, the ‘public’ sector group in particular has exhibited a greater variation (up to 132%) over the years. 相似文献