全文获取类型
收费全文 | 42641篇 |
免费 | 3014篇 |
国内免费 | 1023篇 |
专业分类
电工技术 | 490篇 |
综合类 | 6196篇 |
化学工业 | 2430篇 |
金属工艺 | 571篇 |
机械仪表 | 242篇 |
建筑科学 | 25779篇 |
矿业工程 | 846篇 |
能源动力 | 484篇 |
轻工业 | 97篇 |
水利工程 | 4759篇 |
石油天然气 | 184篇 |
武器工业 | 145篇 |
无线电 | 225篇 |
一般工业技术 | 2955篇 |
冶金工业 | 666篇 |
原子能技术 | 72篇 |
自动化技术 | 537篇 |
出版年
2024年 | 106篇 |
2023年 | 274篇 |
2022年 | 763篇 |
2021年 | 874篇 |
2020年 | 909篇 |
2019年 | 610篇 |
2018年 | 768篇 |
2017年 | 987篇 |
2016年 | 1086篇 |
2015年 | 1399篇 |
2014年 | 2811篇 |
2013年 | 1821篇 |
2012年 | 2937篇 |
2011年 | 3186篇 |
2010年 | 2541篇 |
2009年 | 3188篇 |
2008年 | 3102篇 |
2007年 | 3677篇 |
2006年 | 2937篇 |
2005年 | 2575篇 |
2004年 | 1957篇 |
2003年 | 1727篇 |
2002年 | 1486篇 |
2001年 | 1160篇 |
2000年 | 966篇 |
1999年 | 711篇 |
1998年 | 486篇 |
1997年 | 392篇 |
1996年 | 301篇 |
1995年 | 221篇 |
1994年 | 188篇 |
1993年 | 134篇 |
1992年 | 108篇 |
1991年 | 69篇 |
1990年 | 48篇 |
1989年 | 42篇 |
1988年 | 30篇 |
1987年 | 26篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 11篇 |
1982年 | 16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 15 毫秒
11.
影响混凝土强度的因素及控制措施 总被引:3,自引:3,他引:0
分析了水泥强度等级、水灰比和骨料质量等内因,及施工条件、养护温度、湿度、龄期等外因对混凝土强度的影响,并提出了控制混凝土强度的相应措施,以确保混凝土强度符合设计及施工要求,从而保证建筑物结构安全。 相似文献
12.
结合大同铁路分局中心医院直线加速器室工程实际,介绍了大体积防射线混凝土的特点及施工中应注意的事项,并阐述了具体的施工技术。 相似文献
13.
高 2 7m的水塔建于 193 4年 ,其顶部水罐由 12根钢筋混凝土柱支撑。在倒向侧 7根立柱上形成不同高度的爆破切口 ,背向侧倾倒中心线上的一根立柱上形成小爆破切口 ,其余 4根立柱底部打贯通孔 ,使水塔准确定向倾倒。文中讨论了立柱切口高度的计算 ,爆破参数的确定 ,并介绍了所采用的安全措施。 相似文献
14.
运用Excel软件,高效解决了混凝土结构计算中较复杂的圆形截面偏压构件的承载力计算问题。该编程计算方法同样适用于土力学、水力学、钢结构等领域。对于解决工程中的各种学科计算问题有着广阔的应用前景。 相似文献
15.
The main subject of this paper is to demonstrate the response of structural concrete to different imposed strain rates. Attention is focused on the strain rate about 10-2 s -1>, where some technical difficulties are experienced when an exact determination of mechanical properties for quasi-brittle materials is attempted. The design of a measurement system, which realizes computer acquisition, analysis, and graphic representation of data, is also presented. 相似文献
16.
17.
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
18.
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
19.
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
20.
冲切成槽法施工薄壁砼防渗墙,是一种新型防渗墙施工方法,它是利用特制的扁钻头对风化基岩或卵石层进行冲切成槽的施工方法,在工艺上有着较强的优越性. 相似文献