全文获取类型
收费全文 | 2537篇 |
免费 | 294篇 |
国内免费 | 152篇 |
专业分类
电工技术 | 299篇 |
综合类 | 302篇 |
化学工业 | 146篇 |
金属工艺 | 65篇 |
机械仪表 | 155篇 |
建筑科学 | 442篇 |
矿业工程 | 62篇 |
能源动力 | 80篇 |
轻工业 | 33篇 |
水利工程 | 118篇 |
石油天然气 | 29篇 |
武器工业 | 10篇 |
无线电 | 302篇 |
一般工业技术 | 438篇 |
冶金工业 | 87篇 |
原子能技术 | 48篇 |
自动化技术 | 367篇 |
出版年
2024年 | 5篇 |
2023年 | 35篇 |
2022年 | 59篇 |
2021年 | 81篇 |
2020年 | 93篇 |
2019年 | 84篇 |
2018年 | 65篇 |
2017年 | 101篇 |
2016年 | 98篇 |
2015年 | 83篇 |
2014年 | 150篇 |
2013年 | 173篇 |
2012年 | 199篇 |
2011年 | 216篇 |
2010年 | 171篇 |
2009年 | 171篇 |
2008年 | 140篇 |
2007年 | 154篇 |
2006年 | 141篇 |
2005年 | 124篇 |
2004年 | 106篇 |
2003年 | 84篇 |
2002年 | 71篇 |
2001年 | 66篇 |
2000年 | 42篇 |
1999年 | 22篇 |
1998年 | 31篇 |
1997年 | 38篇 |
1996年 | 24篇 |
1995年 | 30篇 |
1994年 | 22篇 |
1993年 | 24篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1990年 | 18篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1971年 | 1篇 |
1964年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有2983条查询结果,搜索用时 15 毫秒
61.
In this study, porous clay heterostructures (PCH) are synthesized through gallery template approach and characterized using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Nitrogen adsorption–desorption techniques. Batch adsorption studies are conducted to investigate the effect of parameters such as adsorbent dosage, pH, concentration, and contact time on adsorption of toluene by PCH in aqueous solutions. Equilibrium data were fitted to the Langmuir and Freundlich models. Based on the results, by increasing the PCH dosage from 0.5 g/L to 4 g/L, toluene removal is enhanced from 34% to 88.1%. 相似文献
62.
63.
随机缺陷模态法在弦支穹顶稳定性计算中的应用 总被引:2,自引:0,他引:2
初始几何缺陷对弦支穹顶的稳定性能有较大的影响。在结构整体稳定性计算中,利用随机缺陷模态法为结构施加合理的初始几何缺陷是该文的主要研究目的。首先采用一致缺陷模态法,在不同初始几何缺陷下,对肋环2型弦支穹顶结构进行稳定性能分析,然后讨论随机缺陷模态中方差的取值方法,并利用该方法对肋环2型弦支穹顶结构进行了210种不同初始几何缺陷下的稳定性能分析,两种分析方法所施加缺陷的最大值均为结构跨度的1/300。分析结果表明:结构的初始几何缺陷对结构的稳定性能影响较大,考虑初始几何缺陷后结构稳定性能为完善结构的50%左右,且采用一致缺陷模态法时也需通过考虑不同缺陷分布形式的多次计算才能合理评估结构的稳定性能,建议在跨度较大、较为复杂的结构中采用随机模态法来考虑初始几何缺陷对结构稳定性能的影响。 相似文献
64.
65.
The target displacement ductility requirements for circular RC single-column bridge bents are considered using a proposed multifailure mode algorithm to determine the required thickness of fiber-reinforced polymer wraps (FRPs). The procedure is developed using two in-house computer algorithms, PACCC (plastic analysis of circular concrete columns) and PACCC-FRP, to generate a moment-curvature analysis using circular segment slices and subsequent failure mode predictions in single-column bents for both FRP-wrapped and unwrapped circular RC sections. The results of the study showed good comparison to published experimental tests at the ultimate force-deflection states of RC sections and against three commercial “software test beds.” The study uses PACCC-FRP to show that single columns experiencing a brittle failure may be retrofitted with FRP wraps in order to increase the displacement ductility and satisfy target ductility values within the ductility wrap envelope, or wrap-saturation level, as established herein. 相似文献
66.
Behzad D. Manshadi Anastasios P. Vassilopoulos Julia de Castro Thomas Keller 《Canadian Metallurgical Quarterly》2011,15(5):833-840
Glass-fiber-reinforced polymer (GFRP) cell-core sandwiches are composed of outer GFRP face sheets, a foam core, and a grid of GFRP webs integrated into the core to reinforce the shear load capacity. One of the critical failure modes of cell-core sandwich structures is shear wrinkling, a local buckling failure in the sandwich webs because of shear loading. The shear wrinkling behavior of GFRP laminates with different laminate sequences, stabilized by a polyurethane foam core, was experimentally and numerically investigated. Shear wrinkling was simulated by a biaxial compression–tension setup. The results show that an increasing transverse tension load significantly decreases the wrinkling load. The decreasing effect of tension is explained by the lateral contraction because of Poisson’s effect, which causes an increase in the initial imperfections and subsequent accelerated bending. 相似文献
67.
68.
A. R. Gersborg O. Sigmund 《International journal for numerical methods in engineering》2011,87(9):822-843
This paper studies topology optimization of a coupled opto‐mechanical problem with the goal of finding the material layout which maximizes the optical modulation, i.e. the difference between the optical response for the mechanically deformed and undeformed configuration. The optimization is performed on a periodic cell and the periodic modeling of the optical and mechanical fields have been carried out using transverse electric Bloch waves and homogenization theory in a plane stress setting, respectively. Two coupling effects are included being the photoelastic effect and the geometric effect caused by the mechanical deformation. For the studied objective and material choice it is concluded that the photoelastic effect and the geometric effect counteract each other, which yields designs which are fundamentally different if the optimization takes only one effect into account. When both effects are active a compromise is found; however, a strong regularization is needed in order to achieve reasonable 0–1 designs with a clear physical interpretation. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
69.
70.
基于多参考振型的Rayleigh阻尼系数计算方法在单层柱面网壳中的应用 总被引:2,自引:0,他引:2
传统的Rayleigh阻尼系数计算法(两参考振型法)并不总是适用于单层柱面网壳的地震时程分析,对基于多参考振型的Rayleigh阻尼系数计算方法在单层柱面网壳中的应用进行了研究.分析结果表明,在某些地震波作用下,主要贡献振型数目较多,分布较为离散,且频率值相差较大,此种情况下基于多参考振型的计算方法比两参考振型法更为合理;而在另外一些地震波下,结构的主要贡献振型数目较少,分布较为集中,且频率值较为接近,此时基于多参考振型的计算方法和两参考振型法都可以应用. 相似文献