全文获取类型
收费全文 | 9019篇 |
免费 | 907篇 |
国内免费 | 561篇 |
专业分类
电工技术 | 233篇 |
综合类 | 964篇 |
化学工业 | 979篇 |
金属工艺 | 241篇 |
机械仪表 | 134篇 |
建筑科学 | 4007篇 |
矿业工程 | 583篇 |
能源动力 | 83篇 |
轻工业 | 81篇 |
水利工程 | 761篇 |
石油天然气 | 60篇 |
武器工业 | 31篇 |
无线电 | 213篇 |
一般工业技术 | 642篇 |
冶金工业 | 407篇 |
原子能技术 | 7篇 |
自动化技术 | 1061篇 |
出版年
2024年 | 40篇 |
2023年 | 221篇 |
2022年 | 404篇 |
2021年 | 379篇 |
2020年 | 337篇 |
2019年 | 224篇 |
2018年 | 188篇 |
2017年 | 215篇 |
2016年 | 212篇 |
2015年 | 311篇 |
2014年 | 622篇 |
2013年 | 439篇 |
2012年 | 626篇 |
2011年 | 683篇 |
2010年 | 636篇 |
2009年 | 674篇 |
2008年 | 561篇 |
2007年 | 675篇 |
2006年 | 523篇 |
2005年 | 469篇 |
2004年 | 409篇 |
2003年 | 316篇 |
2002年 | 282篇 |
2001年 | 199篇 |
2000年 | 162篇 |
1999年 | 137篇 |
1998年 | 92篇 |
1997年 | 85篇 |
1996年 | 62篇 |
1995年 | 48篇 |
1994年 | 34篇 |
1993年 | 22篇 |
1992年 | 37篇 |
1991年 | 20篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1980年 | 5篇 |
1966年 | 6篇 |
1965年 | 9篇 |
1964年 | 17篇 |
1963年 | 12篇 |
1962年 | 3篇 |
1961年 | 8篇 |
1960年 | 6篇 |
1959年 | 5篇 |
1958年 | 5篇 |
1957年 | 3篇 |
1956年 | 3篇 |
1955年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《Geotextiles and Geomembranes》2022,50(5):910-921
This paper presents a field-scale experimental track over a poor subgrade with an unreinforced section and a geocell-reinforced section subjected to in-situ performance tests. Plate load tests and Benkelman beam tests were carried out distributed in several unreinforced and reinforced layers. The objective was to: (1) examine the variability of the elastic modulus of unbound granular material (UGM) due the influence of its thickness and the presence of poor subgrade in its base, (2) evaluate the modulus improvement factor (MIF) generated by the geocell reinforcement in the UGM and (3) verify the most appropriate condition to apply the MIF to transport infrastructure design. The results showed that there is a significant influence of the thickness of the UGM layer on its elastic modulus when the layer is supported directly over a soft subgrade. The MIF values obtained in field suggest that its determination is mostly related to the UGM maximum elastic modulus rather than its decreased values (by virtue of poor subgrade or reduced thicknesses), and that the analytical formulation presented for MIF calculation has good predictive capability to be applied to pavement design. 相似文献
2.
3.
4.
Expanded graphite (EG) is introduced into poly(vinylidene fluoride) (PVDF) by melt mixing extrusion with water injection. The results demonstrate that the unfunctionalized EG in composite prepared with water injection exbibits better dispersion than that in the one prepared without water injection due to the promoting role of water during extrusion. Thus, the PVDF/EG composite with loading of 4 wt% prepared by water‐assisted mixing extrusion (WAME) exhibits electrical conductivity of about three orders of magnitude higher than the neat PVDF and one order of magnitude higher than the one prepared without water injection. Comparing to the neat PVDF, the thermal conductivity of the composites prepared with and without water injection is increased by 101.5% and 75.0%, respectively. The introduced EG leads to increased Young’s modulus and tensile strength especially for the composite prepared by WAME. The present work indicates that WAME can promote the dispersion of EG in PVDF matrix without any extra functionalization. 相似文献
5.
This paper presents results from a second stage of an experimental study of the dependence of steel fibers distribution along RFC prismatic specimens on the conventional reinforcement ratio and on the total amount of fibers in the concrete mix. The experimental program included two types of prismatic specimens with 30- and 60- kg/m3 of hooked-end steel fibers. Each specimen was sawed into equal segments and the numbers of fibers appearing at the cross-sections were counted and used for a further statistical analysis. This analysis comprised calculations of the average value and standard deviation of a non-dimensional variable, which represents the distribution of the total steel along the specimen. They were used to calibrate a theoretical model, which had been previously proposed by the authors. The test results showed reasonable to good agreement with the theoretical model. A comparison between the results of the 30- and 60-kg/m3 fibers shows that as the conventional reinforcement ratio increases, the standard deviations for the different mixtures approach each other. 相似文献
6.
为了解决大采高综放工作面回风侧端头顶板控制问题,针对马道头矿8211工作面的地质情况,通过对回风顺槽超前注浆加固,提高超前支护范围和支护强度,并对回风侧端头三角区煤壁和顶板进行化学浆加固的技术方案,有效控制了顺槽超前区围岩变形和工作面回风侧端头三角区煤壁片帮,保证了工作面端头区顶板安全。 相似文献
7.
Erdin Ibraim Jean-Francois Camenen Andrea Diambra Karolis Kairelis Laura Visockaite Nilo Cesar Consoli 《Geotextiles and Geomembranes》2018,46(4):497-510
This paper explores the aspects related to the energy consumption for the compaction of unreinforced and fibre reinforced samples fabricated in the laboratory. It is well known that, for a fixed soil density, the addition of fibres invariably results in an increased resistance to compaction. However, similar peak strength properties of a dense unreinforced sample can be obtained using looser granular soil matrices mixed with small quantities of fibres. Based on both experimental and discrete element modelling (DEM) procedures, this paper demonstrates that less compaction energy is required for building loose fibre reinforced sand samples than for denser unreinforced sand samples while both samples show similar peak strength properties. Beyond corroborating the macro-scale experimental observations, the result of the DEM analyses provides an insight into the local micro-scale mechanisms governing the fibre-grain interaction. These assessments focus on the evolution of the void ratio distribution, re-arrangement of soil particles, mobilisation of stresses in the fibres, and the evolution of the fibre orientation distribution during the stages of compaction. 相似文献
8.
Sarabjeet Singh Sidhu Malkeet Singh Preetkanwal Singh Bains 《Particulate Science and Technology》2018,36(3):324-331
The present study investigates the thermal conductivity of bimodal SiC particulate distribution in aluminum matrix composites fabricated via powder metallurgy route. The effects of the SiCp reinforcement size distribution and processing parameters such as sintering time and temperature on the thermal conductivity have been examined. The Box–Behnken experimental array was employed to identify the effects of selected variables on the thermal conductivity of the composite. A reasonable augmentation in the thermal conductivity was observed with an increase in sintering time and %volume fraction of fine SiC particulates. It has been demonstrated that the matrix doped with fine SiC particulates (37?µm) occupied interstitial positions and formed continuous SiC–matrix network resulting in minimizing the micropores that contributed for good thermal conductivity, that is, 235?W/mK. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were conducted to evaluate the microstructure architecture and interfacial phase formation. 相似文献
9.
In an environment where robots coexist with humans, mobile robots should be human-aware and comply with humans' behavioural norms so as to not disturb humans' personal space and activities. In this work, we propose an inverse reinforcement learning-based time-dependent A* planner for human-aware robot navigation with local vision. In this method, the planning process of time-dependent A* is regarded as a Markov decision process and the cost function of the time-dependent A* is learned using the inverse reinforcement learning via capturing humans' demonstration trajectories. With this method, a robot can plan a path that complies with humans' behaviour patterns and the robot's kinematics. When constructing feature vectors of the cost function, considering the local vision characteristics, we propose a visual coverage feature for enabling robots to learn from how humans move in a limited visual field. The effectiveness of the proposed method has been validated by experiments in real-world scenarios: using this approach robots can effectively mimic human motion patterns when avoiding pedestrians; furthermore, in a limited visual field, robots can learn to choose a path that enables them to have the larger visual coverage which shows a better navigation performance. 相似文献
10.
Kh. Lotfy 《International Journal for Computational Methods in Engineering Science and Mechanics》2019,20(1):14-28
In this article, two theories of the generalized thermoelasticity Green-Naghdi theory (of type II and III) are applied, as well as the coupled theory to study the effect of magnetic field and rotation under influence of gravity on 2D problem of a fibre-reinforced thermoelastic. The normal mode analysis is used to obtain the expressions for the temperature, displacement components and the thermal stresses distributions. The resulting formulation is applied for two different concrete problems. The first concerns the case of a punch moving across the surface of semi-infinite thermoelastic half-space subjected to appropriate boundary conditions. The second deals with a thick plate subjected to a time-dependent heat source on each face. Numerical results are illustrated graphically for each problem considered. A comparison is made with the results predicted obtained by the two theories in the presence and absence of magnetic field, rotation and gravity field. 相似文献