全文获取类型
收费全文 | 312篇 |
免费 | 38篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 40篇 |
综合类 | 12篇 |
化学工业 | 19篇 |
金属工艺 | 69篇 |
机械仪表 | 18篇 |
建筑科学 | 22篇 |
矿业工程 | 4篇 |
能源动力 | 26篇 |
轻工业 | 10篇 |
水利工程 | 2篇 |
石油天然气 | 4篇 |
武器工业 | 1篇 |
无线电 | 11篇 |
一般工业技术 | 52篇 |
冶金工业 | 22篇 |
原子能技术 | 6篇 |
自动化技术 | 39篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 13篇 |
2018年 | 12篇 |
2017年 | 11篇 |
2016年 | 12篇 |
2015年 | 9篇 |
2014年 | 19篇 |
2013年 | 29篇 |
2012年 | 32篇 |
2011年 | 38篇 |
2010年 | 29篇 |
2009年 | 30篇 |
2008年 | 20篇 |
2007年 | 22篇 |
2006年 | 12篇 |
2005年 | 8篇 |
2004年 | 8篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
排序方式: 共有357条查询结果,搜索用时 16 毫秒
41.
本文通过表面纳米化处理(SMAT)在P92钢表层中形成纳米组织结构,研究了回火温度对表层纳米组织演化行为和析出行为的影响.结果表明:淬火态和回火态P92钢组织经过SMAT处理后沿深度方向依次是纳米层、剧烈变形层、最终过渡到正常组织.随后分别研究了淬火和回火态SMAT试样经不同温度回火后微观组织的再结晶及长大行为.经SMAT处理的铁素体纳米晶粒在550℃时仍能保持较好的纳米结构,甚至高达650℃时表层晶粒仍为纳米晶,当温度超过760℃时表层组织发生显著的再结晶和晶粒长大现象.纳米晶界能抑制淬火态P92钢在较低温度回火时M23C6碳化物的析出.纳米组织提高了高温回火过程中合金元素在铁素体中的扩散速率,加速了M23C6碳化物的长大过程.不同温度回火过程中SMAT纳米层中析出行为的变化将在本文中详细描述. 相似文献
42.
This paper deals with the influence of post-weld heat treatment (PWHT) of T92/TP316H martensitic/austenitic transition weldment on the resulting microstructure and creep characteristics. Experimental weldments were fabricated by gas tungsten arc welding using a nickel-based weld metal (Ni WM). After the welding, two individual series of produced weldments were heat-treated according to two different PWHT procedures. The first “conventional PWHT” was carried out via subcritical tempering (i.e. bellow Ac1 temperature of T92 steel), whereas the other one, the so-called “full PWHT” consisted of a complete reaustenitization of the weldments followed by water-quenching and final tempering. The use of “conventional PWHT” preserved microstructural gradient of T92 steel heat-affected zone (HAZ), consisting of its typical coarse-grained and fine-grained subregions with tempered martensitic and recrystallized ferritic–carbidic microstructures respectively. In contrast, the “full PWHT” led to the complete elimination of the original HAZ via transformation processes involved, i.e. the reaustenitization and back on-cooling martensite formation. The observed microstructural changes depending on the initial PWHT conditions were further manifested by corresponding differences in the weldments’ creep performance and their failure mode. The weldments in “conventional PWHT” state ruptured after long-term creep tests by premature “type IV failure” within their recrystallized intercritical HAZs. On the contrary, the long-term creep behavior of the weldments processed by “full PWHT” was characterized by their remarkable creep life extension but also by the occurrence of unfavorable “decohesion failure” along T92/Ni WM interface. 相似文献
43.
用透射电镜、扫描电镜和X射线能谱仪对P92钢在不同时效状态下δ-铁素体内的析出相进行了分析,结果表明,δ-铁素体内包含两种析出相,分别为VN与Laves相。VN呈短棒状,尺寸20~70 nm,较为稳定,Laves相平均等效直径在600℃下随时间的增加则有较大改变。此外,研究表明P92钢中的Laves相不但在晶界与亚晶界上析出,也在δ-铁素体晶内析出。 相似文献
44.
《International Journal of Hydrogen Energy》2020,45(16):10189-10198
Precipitation of Cr-rich carbides, diffusible hydrogen content and heterogeneous microstructure formation across the weldments makes heat-affected zone (HAZ) susceptible to intergranular cracking and makes weldability of creep strength enhanced ferritic (CSEF) Grade P92 steel a critical issue. In the present research work, the Granjon implant test and mercury method (for diffusible hydrogen measurement) have been performed on Grade P92 steel welded specimens to study the effect of welding parameters on diffusible hydrogen levels and their subsequent effect on hydrogen-assisted cracking (HAC). The weld metal was deposited by a shielded metal arc welding process on Grade P92 steel samples using P92 matching filler. The three different welding conditions are used to measure the diffusible hydrogen level in the deposited metal. Granjon implant test was performed to evaluate HAZ HAC susceptibility with similar welding conditions which were used in the mercury method. Lower critical stress (LCS) was also evaluated using the Granjon implant test. The higher susceptibility of CSEF Grade P92 steel welded plate towards HAZ HAC was noticed in case of lower heat input or higher diffusible hydrogen content. However, by considering LCS, fracture mode and diffusible hydrogen content, the weld deposited using the highest heat input (condition III) offers great resistance to HAZ HAC. 相似文献
45.
按照GB/T 17747.2—1999《天然气压缩因子的计算第2部分:用摩尔组成进行计算》,采用AGA8—92DC计算方法,用VB编程计算了天然气压缩因子。用二分法求解状态方程,精度满足工程需要。 相似文献
46.
表征非晶聚合物分子取向分布的ODF分析法 总被引:1,自引:1,他引:0
本文对单轴取向非晶聚合物的分子分布状态进行了物理描述和数学表征,详细论证了广角X射线方法测定和计算全取向分布函数ODF(All orientation distribution function)。在此基础上,用Fortran语言编写计算ODF的ODF92型程序,并用于单轴取向蜚 晶态聚脂(PET)的取向分布分析,获得 了令人满意的结果。 相似文献
47.
48.
The transformation relationship of the coordinate variables between principal stress space and deviatoric stress plane has been deduced and the isochronous creep rupture loci of disparate criteria have been described on deviatoric stress plane so as to analyze the creep behaviour under multiaxial stress state. The creep experiments of P92 steel smooth and notched specimens subjected to various stresses at 650 °C have been conducted. A modified constitutive model for the creep of P92 steel has been proposed and used to simulate the creep of P92 steel notched specimens with FEA software. The FEA results were consistent with the experimental data and the fracture morphology observation. It was found that the Hayhurst criterion had the best correlation with the experimental results of P92 steel under multiaxial stress state than other criteria through the comparison of the isochronous creep rupture loci on deviatoric plane. 相似文献
49.
50.
Spatial competition and regulatory change in the grain handling and transportation system in western Canada 总被引:2,自引:0,他引:2
The grain handling and transportation system (GHTS) has been a defining component of the western Canadian economy since the
early part of the last century. Only two major railways serve the grain handling industry, so the potential for the exercise
of market power in transportation appears to be significant. In fact, spatially oriented regulations applicable to railways
exist in Canada to mitigate this, but to date they have not often been used by shippers. While the reasons for this are not
completely clear, we suggest that the regulations are now inadequate for the current state of the GHTS. Using a unique data
set from the year 2000, we assess the effect on the grain handling industry of modifications to these regulations, and find
that significant gains for shippers from these modifications are possible. These gains are computed to be on the order of
C$10–15 million per year for grain shippers alone.
We would like to thank conference and presentation participants (Transportation Research Board, Canadian Agricultural Economics
Society, University of British Columbia, University of Leeds and California State University, Long Beach) as well as the anonymous
reviewers who commented on the earlier versions of this paper. We would also like to acknowledge support from the Saskatchewan
Department of Highways. 相似文献