全文获取类型
收费全文 | 11900篇 |
免费 | 1170篇 |
国内免费 | 430篇 |
专业分类
电工技术 | 299篇 |
技术理论 | 1篇 |
综合类 | 824篇 |
化学工业 | 2014篇 |
金属工艺 | 384篇 |
机械仪表 | 530篇 |
建筑科学 | 3567篇 |
矿业工程 | 451篇 |
能源动力 | 204篇 |
轻工业 | 2168篇 |
水利工程 | 182篇 |
石油天然气 | 154篇 |
武器工业 | 27篇 |
无线电 | 617篇 |
一般工业技术 | 931篇 |
冶金工业 | 518篇 |
原子能技术 | 144篇 |
自动化技术 | 485篇 |
出版年
2024年 | 61篇 |
2023年 | 268篇 |
2022年 | 385篇 |
2021年 | 566篇 |
2020年 | 559篇 |
2019年 | 427篇 |
2018年 | 367篇 |
2017年 | 407篇 |
2016年 | 446篇 |
2015年 | 437篇 |
2014年 | 996篇 |
2013年 | 1008篇 |
2012年 | 973篇 |
2011年 | 887篇 |
2010年 | 710篇 |
2009年 | 667篇 |
2008年 | 528篇 |
2007年 | 667篇 |
2006年 | 630篇 |
2005年 | 504篇 |
2004年 | 380篇 |
2003年 | 348篇 |
2002年 | 321篇 |
2001年 | 225篇 |
2000年 | 184篇 |
1999年 | 116篇 |
1998年 | 82篇 |
1997年 | 69篇 |
1996年 | 47篇 |
1995年 | 38篇 |
1994年 | 33篇 |
1993年 | 21篇 |
1992年 | 27篇 |
1991年 | 20篇 |
1990年 | 24篇 |
1989年 | 14篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1974年 | 3篇 |
1963年 | 3篇 |
1962年 | 2篇 |
1957年 | 3篇 |
1954年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
建筑供排水用聚丙烯管道(PP-R)特性简析 总被引:2,自引:0,他引:2
PP -R管道具有质轻、连接方便、良好耐热性和较小导热系数、耐腐蚀且管道阻力小等优点 ,属绿色产品 ,本文对施工过程中就PP -R管与混凝土的粘结不密、抗紫外性能差等问题提出了相应的处理措施 相似文献
93.
Theoretical Models for Binder Burnout 总被引:8,自引:0,他引:8
The kinetics of binder burnout, from a ceramic green body, are considered for the case of an "unzipping" binder which decomposes to produce a volatile monomer. The process is considered to fail if the concentration of monomer in the green body exceeds that in equilibrium with vapor at 1 atm (≅105 Pa), when an internal bubble would be expected to form. Steady-state diffusional calculations and computer simulations explore the size and temperature dependence of the process and are in agreement. The model suggests that it is not feasible to burn out a large flat piece greater than about 3 mm thick, without going to very long times of burnout. The kinetics are significantly improved if porosity develops in the piece during the early stages of decomposition, as opposed to the retreat of the binder into the piece on a uniform front. 相似文献
94.
95.
96.
This paper presents an experimental investigation into various aspects of epoxy-bonded polymethylmethacrylate (PMMA) and PMMA-to-aluminium joints. The effects of adhesive thickness, overlap area, surface roughness, and environmental exposure on the joint strength were studied. Results indicated that the joint strength was not directly proportional to the overlap area, while sanding had a positive effect on the joint strength. A negative effect was observed when adhesive thickness was increased. The fatigue behaviour of adhesively-bonded joints under dynamic loading was found to be independent of frequency, for the range of values tested; however, it was dependent on the test temperature with greater reduction in fatigue life observed in PMMA-to-aluminium joints at higher temperature. Empirical equations from which the fatigue life of joints can be predicted were obtained by regression analysis. Intermittent fatigue testing of the joints was also performed. The epoxy adhesive tested proved to be a satisfactory choice for outdoor exposure. The rate of degradation of the adhesive was slow with the adherend itself degrading at a faster rate than the adhesive or the bondline. 相似文献
97.
Office workers perform tasks using different information and communication technologies (ICT) involving various postures. Adequate variation in postures and muscle activity is generally believed to protect against musculoskeletal complaints, but insufficient information exists regarding the effect on postural variation of using different ICT. Thus, this study among office workers aimed to determine and compare postures and postural variation associated with using distinct types of ICT. Upper arm, head and trunk postures of 24 office workers were measured with the Physiometer® over a whole day in their natural work and away-from-work environments. Postural variation was quantified using two indices: APDF(90-10) and EVA(sd). Various ICT had different postural means and variation. Paper-based tasks had more non-neutral, yet also more variable postures. Electronics-based tasks had more neutral postures, with less postural variability. Tasks simultaneously using paper- and electronics-based ICT had least neutral and least variable postures. Tasks without ICT usually had the most posture variability. Interspersing tasks involving different ICT could increase overall exposure variation among office workers and may thus contribute to musculoskeletal risk reduction. 相似文献
98.
该文基于概率论与泥沙起动基本理论,考虑了起动概率、相对暴露度与细颗粒泥沙间黏结力和附加下压力对泥沙起动的影响,采用滑动起动模型,从理论上推导出了适用于弯道岸坡上粗、细泥沙颗粒起动的统一流速公式,完善了已有研究成果对泥沙起动概率考虑的不足。公式综合了弯道岸坡、顺直岸坡、正负坡及平坡等条件下粗细泥沙颗粒起动流速计算,可简化为各简单条件下泥沙起动流速公式。通过各简单条件下泥沙起动流速实测资料验证,该文公式与实测数据符合良好。 相似文献
99.
采用绿色合成法,在水相条件下,在Pd/C催化剂的作用下用苯甲酸催化氢化合成环己基甲酸.通过一系列的实验,得到了较好的合成环己基甲酸的工艺条件,在该条件下,能够得到比较纯的产物和较好的产物收率. 相似文献
100.
叙述硫化外胎胎冠花纹沟露线、胎冠中心线露线、胎肩露线、胎圈露线以及胎里露线等问题的特征和弊端,提出结构设计、生产工艺和设备条件各方面的预防和改进措施:同一规格、不同花纹的轮胎要用不同的胎面挤出口型,胎肩曲线、内衬层厚度等设计要合理;压延、挤出、成型和定型、硫化各工序要严格执行工艺规程;要经常检查硫化设备运行状况,对磨损和老化部件及时更换。 相似文献