全文获取类型
收费全文 | 39564篇 |
免费 | 3271篇 |
国内免费 | 1638篇 |
专业分类
电工技术 | 826篇 |
技术理论 | 1篇 |
综合类 | 4134篇 |
化学工业 | 2335篇 |
金属工艺 | 2308篇 |
机械仪表 | 1987篇 |
建筑科学 | 14962篇 |
矿业工程 | 1573篇 |
能源动力 | 978篇 |
轻工业 | 829篇 |
水利工程 | 1782篇 |
石油天然气 | 729篇 |
武器工业 | 175篇 |
无线电 | 4196篇 |
一般工业技术 | 4324篇 |
冶金工业 | 1038篇 |
原子能技术 | 1288篇 |
自动化技术 | 1008篇 |
出版年
2024年 | 52篇 |
2023年 | 320篇 |
2022年 | 666篇 |
2021年 | 863篇 |
2020年 | 921篇 |
2019年 | 750篇 |
2018年 | 783篇 |
2017年 | 1009篇 |
2016年 | 1088篇 |
2015年 | 1225篇 |
2014年 | 2376篇 |
2013年 | 2161篇 |
2012年 | 2862篇 |
2011年 | 3286篇 |
2010年 | 2514篇 |
2009年 | 2639篇 |
2008年 | 2421篇 |
2007年 | 2926篇 |
2006年 | 2555篇 |
2005年 | 2191篇 |
2004年 | 1686篇 |
2003年 | 1512篇 |
2002年 | 1284篇 |
2001年 | 1119篇 |
2000年 | 957篇 |
1999年 | 809篇 |
1998年 | 625篇 |
1997年 | 537篇 |
1996年 | 435篇 |
1995年 | 357篇 |
1994年 | 338篇 |
1993年 | 231篇 |
1992年 | 186篇 |
1991年 | 153篇 |
1990年 | 115篇 |
1989年 | 96篇 |
1988年 | 89篇 |
1987年 | 78篇 |
1986年 | 63篇 |
1985年 | 40篇 |
1984年 | 38篇 |
1983年 | 19篇 |
1982年 | 29篇 |
1981年 | 11篇 |
1980年 | 27篇 |
1979年 | 6篇 |
1975年 | 2篇 |
1959年 | 16篇 |
1954年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
Donghai Xu Peng Feng Yang Wang Wanpeng Yang Yu Wang Shaoyan Sun 《American Institute of Chemical Engineers》2022,68(2):e17472
Corrosion and salt deposition problems severely restrict the industrialization of supercritical water oxidation. Transpiring wall reactor can effectively weaken these two problems by a protective water film. In this work, methanol was selected as organic matter, and the influences of vital structural parameters on water film properties and organic matter removal were studied via numerical simulation. The results indicate that higher than 99% of methanol conversion could be obtained and hardly affected by transpiration water layer, transpiring wall porosity and inner diameter. Increasing layer and porosity reduced reactor center temperature, but inner diameter's influence was lower relatively. Water film temperature reduced but coverage rate raised as layer, porosity, and inner diameter increased. Notably, the whole reactor was in supercritical state and coverage rate was only approximately 85% in the case of one layer. Increasing reactor length affected slightly the volume of the upper supercritical zone but enlarged the subcritical zone. 相似文献
3.
4.
《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
5.
6.
7.
8.
《Ceramics International》2022,48(6):8025-8030
In order to meet the high demand for joining ceramic/superalloy composite structure in extreme environments, a novel high-temperature resistant adhesion technique was developed for joining ZrO2 and Inconel 625 by applying an aluminum phosphate emulsion/zirconium sol based adhesive. With increasing temperature, a series of reactions occurred in adhesive, and its high-temperature bonding was attributed to the formation of a composite structure containing various ceramics and intermetallics. The adhesive after RT curing could find direct applications in extreme environments, and provide bonding strength no less than 2.5 MPa in the temperature range of RT-1100 °C. The bonding strength was higher than 4 MPa in the temperature range of 800–1000 °C, which was further attributed to the formation of an effective CTE-gradient relationship among ZrO2, adhesive and Inconel 625, as well as the interfacial reactions between the two substrates. The work broadened the application of adhesion technique and brought new ideas for joining dissimilar engineering materials. 相似文献
9.
Chengcong Zhang 《Science & Technology of Welding & Joining》2018,23(5):394-399
The longitudinal residual stresses in the friction stir-welded plates of 5A06 aluminium and pure copper were determined using the contour method. The results revealed the presence of high tensile and compressive residual stresses on the aluminium and copper sides, respectively. The residual stresses were detected on the weld zone as well as the thermo-mechanically affected zone (TMAZ) of the aluminium plate. In contrast, the compressive residual stresses in the copper plate had a much narrower width along the weld line. Peak tensile stresses up to 240?MPa were found in the TMAZ of the aluminium plate. 相似文献
10.