全文获取类型
收费全文 | 2756篇 |
免费 | 280篇 |
国内免费 | 71篇 |
专业分类
电工技术 | 23篇 |
综合类 | 353篇 |
化学工业 | 60篇 |
金属工艺 | 68篇 |
机械仪表 | 168篇 |
建筑科学 | 1410篇 |
矿业工程 | 19篇 |
能源动力 | 81篇 |
轻工业 | 15篇 |
水利工程 | 33篇 |
石油天然气 | 90篇 |
武器工业 | 8篇 |
无线电 | 38篇 |
一般工业技术 | 622篇 |
冶金工业 | 33篇 |
原子能技术 | 21篇 |
自动化技术 | 65篇 |
出版年
2024年 | 2篇 |
2023年 | 24篇 |
2022年 | 47篇 |
2021年 | 57篇 |
2020年 | 54篇 |
2019年 | 60篇 |
2018年 | 59篇 |
2017年 | 85篇 |
2016年 | 102篇 |
2015年 | 117篇 |
2014年 | 183篇 |
2013年 | 203篇 |
2012年 | 226篇 |
2011年 | 248篇 |
2010年 | 177篇 |
2009年 | 195篇 |
2008年 | 208篇 |
2007年 | 199篇 |
2006年 | 157篇 |
2005年 | 120篇 |
2004年 | 114篇 |
2003年 | 59篇 |
2002年 | 70篇 |
2001年 | 54篇 |
2000年 | 54篇 |
1999年 | 40篇 |
1998年 | 32篇 |
1997年 | 38篇 |
1996年 | 24篇 |
1995年 | 12篇 |
1994年 | 10篇 |
1993年 | 18篇 |
1992年 | 12篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 11篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1980年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有3107条查询结果,搜索用时 15 毫秒
11.
12.
The elastic local post-buckling behaviour of elliptical tubes under compression is analysed in this paper. A brief outline of the local, distortional and global buckling behaviour of EHS tubes is firstly provided, where it is shown that local buckling modes govern the stability of short to intermediate length tubes while distortional modes control the stability of intermediate length to moderately long tubes and global buckling dominates the behaviour of longer tubes. Following this, an in-depth numerical study employing shell finite element modelling, of the elastic local post-buckling behaviour of compressed elliptical hollow section (EHS) tubes is presented. It is concluded that EHS tubes with a low to moderate aspect ratio can support loads up to their limit loads but are imperfection sensitive (shell-type behaviour), while EHS tubes with a moderate to high aspect ratio can carry loads higher than their limit loads (plate-type behaviour) and are imperfection insensitive. The slope of the ascending post-buckling path increases with the EHS aspect ratio and can reach values up to 40% of the slope of the linear primary path. The bound imperfection amplitude concept, separating the imperfection amplitude ranges where the EHS tube is sensitive and insensitive, is proposed. It is also found that, for increasing EHS aspect ratio, the compressive stresses grow and accumulate near the zones of minimum radius of curvature while the zones of maximum radius of curvature possess an approximately uniform and relatively low compressive stress level. Therefore, it is expected that an approach based on the effective width concept widely used for the evaluation of the strength of flat plates may be adapted to the design of EHS tubes with moderate to high aspect ratios. 相似文献
13.
Lateral–torsional buckling of cold-formed zed-purlins partial-laterally restrained by metal sheeting
This paper presents an analytical model for predicting the lateral–torsional buckling of cold-formed zed-purlins partial-laterally restrained by metal sheeting for both down and uplift loadings. The critical load is determined by using energy methods. The focus of the study is to investigate the individual influences of restraints provided by the sheeting and by interval anti-sag bars, the variation of moment distribution along the longitudinal axis, and boundary conditions on the lateral–torsional buckling behaviour of the purlin. 相似文献
14.
15.
Carbon fiber-reinforced polymer (CFRP) composites have been shown to be particularly well suited for external strengthening of reinforced concrete members. However, there is limited information about how they can be used to strengthen steel structures that are susceptible to local and global instabilities. This paper discusses test results of full-scale steel flexural specimens subjected to reversed cyclic loading, some of which are wrapped with CFRP in the plastic hinge region. The main variables investigated are lateral bracing, to study the effect of CFRP wrapping on local buckling and lateral torsional buckling, wrapping scheme, and number of layers of fibers. The test results show that application of CFRP in the plastic hinge region of flexural members has substantial benefits. In particular, the CFRP wraps can increase the size of the yielded plastic hinge region, slow down the occurrence of local buckling, and delay lateral torsional buckling. These benefits reduce strain demands in the critical plastic hinge region and substantially improve energy dissipation capacity within the plastic hinge region. 相似文献
16.
A great deal of attention has been focused on plates subjected to shear loading over the past decades. One main fact in design of such elements, which fall in the category of thin-walled structures, is their buckling behavior. Plate girders and recently shear walls are being widely used by structural engineers, as well as ship and aircraft designers. The role of stiffeners is proved to be vital in design of such structures to minimize their weight and cost.In this work, by using ANSYS finite element method of analysis, some 1200 plates are analyzed in order to study the role of stiffeners and to come up with some limits for an optimized design procedure. This eigenvalue method of analysis is first validated with the theoretical calculations and known cases for a wide range of typical panel geometries.The results show that the number of panels produced by intermediate transverse stiffeners should not be less than the value of plate's aspect ratio. In other words, the transverse stiffeners should divide the length of the plate to portions equal or less than its width.It is also shown that the optimum geometric properties of the stiffeners correspond to the point when the buckling shape of a plate changes from the overall mode to local mode. Furthermore, all stiffened plates, with a similar aspect ratio and number of stiffeners, have a specific value of EIs/aD, for which the critical shear stress is optimal. In addition, some expressions to predict these properties are presented. 相似文献
17.
利用力学原理对金属圆弧拱型波纹屋顶屈曲破坏位置进行了分析,求得一种简化计算的方法。其简化计算结果与试验和有限元计算结果进行对比验证,得出了一些结论。这些结论可为此类大跨度金属圆弧拱型波纹屋顶的设计计算、加工制作等提供有益的参考。 相似文献
18.
19.
The lateral torsional buckling resistance of a beam depends on the support conditions. In structures for buildings, coped beams are often used. A numerical model is developed to investigate the influence of copes on the lateral buckling resistance. The model was verified with laboratory tests. This paper describes the background of the numerical model, the test program and the results of the validation. In a companion paper [Maljaars J, Stark JWB, Steenbergen HMGM, Abspoel R. Lateral-torsional buckling resistance of coped beams. Journal of Constructional Steel Research 2005;61(11):1559-75], the results of a parameter study are presented. 相似文献
20.
在薄壁构件的弯扭失稳问题上近20年以来存在着传统的和较新的两种不同的理论,这两种理论的并存使得一些国家的规范和一些著作出现不一致,例如我国的(GB50017—2003)和N.S.Trahair的著作犤17犦仍然采用传统理论的结果,而(GB50018—2003)、ISO的钢结构材料标准和美国的金属结构稳定设计解说却采用较新理论的结果。作者发现被忽视的横向正应力也是影响薄壁构件稳定的重要因素。本文在考虑非线性横向应变能的基础上,导出了薄壁构件的总势能方程。从板的理论出发,全面考虑微元上各种应力以及外荷载的影响,用假想荷载法导出了薄壁构件的弯扭失稳平衡微分方程。这组平衡微分方程和本文提出能量法的是一致的,这进一步证实了本文提出理论的正确性。 相似文献