全文获取类型
收费全文 | 44300篇 |
免费 | 3169篇 |
国内免费 | 1054篇 |
专业分类
电工技术 | 527篇 |
综合类 | 6403篇 |
化学工业 | 2912篇 |
金属工艺 | 561篇 |
机械仪表 | 255篇 |
建筑科学 | 26323篇 |
矿业工程 | 926篇 |
能源动力 | 513篇 |
轻工业 | 257篇 |
水利工程 | 4939篇 |
石油天然气 | 220篇 |
武器工业 | 148篇 |
无线电 | 153篇 |
一般工业技术 | 3153篇 |
冶金工业 | 716篇 |
原子能技术 | 79篇 |
自动化技术 | 438篇 |
出版年
2024年 | 123篇 |
2023年 | 314篇 |
2022年 | 844篇 |
2021年 | 956篇 |
2020年 | 980篇 |
2019年 | 665篇 |
2018年 | 817篇 |
2017年 | 1068篇 |
2016年 | 1175篇 |
2015年 | 1488篇 |
2014年 | 2924篇 |
2013年 | 1919篇 |
2012年 | 3043篇 |
2011年 | 3315篇 |
2010年 | 2633篇 |
2009年 | 3291篇 |
2008年 | 3142篇 |
2007年 | 3752篇 |
2006年 | 3028篇 |
2005年 | 2631篇 |
2004年 | 2005篇 |
2003年 | 1762篇 |
2002年 | 1532篇 |
2001年 | 1201篇 |
2000年 | 991篇 |
1999年 | 726篇 |
1998年 | 496篇 |
1997年 | 402篇 |
1996年 | 311篇 |
1995年 | 232篇 |
1994年 | 201篇 |
1993年 | 139篇 |
1992年 | 111篇 |
1991年 | 70篇 |
1990年 | 48篇 |
1989年 | 47篇 |
1988年 | 32篇 |
1987年 | 31篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 11篇 |
1982年 | 17篇 |
1980年 | 24篇 |
1979年 | 2篇 |
1975年 | 2篇 |
1967年 | 1篇 |
1964年 | 1篇 |
1962年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 650 毫秒
51.
52.
通过对洛阳热电厂拟选择的地基处理方案进行比较,并结合该电厂施工实例论证了φ800/1600扩底钢筋混凝土灌注桩是最适于该电厂及相似地区的地基处理方式。 相似文献
53.
曹娥江大闸是国内最大的河口大闸,其中闸墩施工在夏季高温季节进行.较全面地阐述了混凝土原材料取料温度值的选取及控制措施,已浇筑混凝土内外温差及降温速率的控制措施等.根据闸墩的结构及边界条件,为了控制温度应力防止裂缝的产生,在施工过程中采取了骨料预冷、冷水拌和、掺冰屑拌和、仓面遮阳、内部通冷却水及外侧保温等综合温控措施,确保了闸墩混凝土的施工质量. 相似文献
54.
55.
Different qualities of concrete have been fire tested using different geometries of the specimens as well as different load levels and load configurations. The main objective with the study was to examine a test methodology consisting of a full‐scale test and different small scale‐tests for determining the probability of spalling and the amount of spalling of fire exposed concrete structures. A reference specimen was defined as a one‐sided fire exposed slab with the dimensions 1800 × 1200 mm2 giving an exposed area of 1500 × 1200 mm2. A number of concrete qualities with different probabilities for spalling, were tested using the reference specimen. These tests showed that the reference specimens worked well giving the expected test results. Small specimens were manufactured in different shapes with the same concrete as the one used in the reference tests. These small specimens were tested either at the same time as the reference specimens in the large furnace or afterwards on a small‐scale furnace where the fire exposed surface was 450 × 360 mm2. The test results clearly show the increased probability and the increased amount of spalling by using external compressive loading. The results also show that by using pre‐stress through bars or wires the load can be lost due to heating of the bars/wires which results in a decreased amount of spalling. The boundary of the specimen also affects the amount of spalling. The spalling around the edges was in all tests less than the spalling on the central parts of the exposed area. It could also be noted that the spalling did not pass completely through any of the specimens. The reason for this is probably that the water/vapour could migrate out from the unexposed surface of the specimen. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
56.
LU Hailin ZHANG Mingyuan LI Zhongxian 《武汉理工大学学报(材料科学英文版)》2007,22(2):371-375
The effect of steel fibre used in concrete was systematically analyzed by model testing of 30 2-pile thick caps of steel-fibre reinforced concrete, in which the model scale was 1:5. The experiment system composed of a loading device, strain measurement system and a data-acquisition system was used, also an electromechanic centigrade scale, a lens and a Y J-25 static resistance strainometer were used.The experimental results show that the volumetric rate of steel fibre and draw ratio have an important influence on its load-bearing capacity. The incorporation of steel fibre can effectively improve the extension and reduce the thickness of the caps. 相似文献
57.
An incremental iterative process based on direct energy minimization is presented for a limit analysis of nonlinear elastic lateral displacements and twists of reinforced and prestressed beams. Problems encountered with the constitutive relations are discussed and two possible material models are presented. 相似文献
58.
连续、高强度、快速施工既是碾压混凝土坝的施工特点,也是层间结合质量的根本保证。龙滩水电站碾压混凝土浇筑采用了合理的入仓手段和机械设备配置,通过配套的碾压混凝土施工技术的应用和健全的管理体系,有效地提高了碾压混凝土施工强度,保证了施工进度和施工质量。 相似文献
59.
在搜集国内外有关资料的基础上,通过对混凝土在多轴应力作用下的徐变与强度关系分析,说明在多轴应力状态下不能简单地采用叠加原理。展示了新的三轴徐变量测仪器及其徐变试验成果以及2组多轴与单轴应力状态下的徐变恢复试验成果,并对试验数据进行比较分析,得到多轴应力状态下徐变恢复与应力大小以及持荷时间之间的规律,证实了多轴应力状态下的徐变恢复与已经产生的压缩徐变有密切的关系。 相似文献
60.
In wintertime, the use of studded tyres is common in the Nordic countries, steeply in creasing road wear. Apart from reducing surface quality and durability, the airborne dust presents a potential health hazard. To reduce road wear and dust release, there is a tendency to use harder and more wear-resistant aggregate materials.On the roads in and around Trondheim, mid-Norway, three types of aggregate material are common: greenstone, jasper and ‘mylonite’, in fact a cataclasite. Extensive laboratory testing suggests that cataclasite aggregate has better wear resistance than greenstone, but less than jasper [Erichsen E, Schiellerup H, Gautneb, H, Ottesen RT, Broekmans M. Road dust in Trondheim — analysis of the mineral content of airborne dust. (In Norwegian.) Geological Survey of Norway, NGU-report 2004. 037; 2004. p. 73]. However , observations on fluorescence-impregnated plane and thin sections demonstrate that in practice, cataclasite wears faster than greenstone, which may be attributed to its oriented fabric, as opposed to the random fabric in greenstone and jasper. The original article by Rosiwal from 1896 [Rosiwal A. Neue Untersuchungser gebnisse über die Härte von Mineralien und Gesteine. Verhandlungen der kaiserlich-königlichen geologischen Reichsanstalt, vol. 17/18; 1896. p. 475–491] on abrasion hardness and anisotropy provides an elegant explanation for the field observations. 相似文献