全文获取类型
收费全文 | 804篇 |
免费 | 33篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 34篇 |
综合类 | 70篇 |
化学工业 | 83篇 |
金属工艺 | 56篇 |
机械仪表 | 47篇 |
建筑科学 | 158篇 |
矿业工程 | 21篇 |
能源动力 | 44篇 |
轻工业 | 5篇 |
水利工程 | 26篇 |
石油天然气 | 129篇 |
无线电 | 12篇 |
一般工业技术 | 61篇 |
冶金工业 | 75篇 |
原子能技术 | 3篇 |
自动化技术 | 34篇 |
出版年
2023年 | 10篇 |
2022年 | 19篇 |
2021年 | 19篇 |
2020年 | 18篇 |
2019年 | 11篇 |
2018年 | 15篇 |
2017年 | 25篇 |
2016年 | 33篇 |
2015年 | 19篇 |
2014年 | 54篇 |
2013年 | 48篇 |
2012年 | 60篇 |
2011年 | 58篇 |
2010年 | 52篇 |
2009年 | 47篇 |
2008年 | 38篇 |
2007年 | 65篇 |
2006年 | 55篇 |
2005年 | 44篇 |
2004年 | 34篇 |
2003年 | 24篇 |
2002年 | 24篇 |
2001年 | 16篇 |
2000年 | 10篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1984年 | 4篇 |
1982年 | 1篇 |
排序方式: 共有858条查询结果,搜索用时 20 毫秒
1.
A shale gas gathering and transportation pipeline in a good block in Sichuan Province started leaking after less than a year of operation. To investigate the causes of corrosion of the sulfate-reducing bacteria (SRB), optical microscopy, scanning electron microscopy, and X-ray diffraction were used to analyze the corrosion and perforation of the shale gas surface pipeline in conjunction with bacterial corrosion simulation experiments. The results showed that the pipeline material (L360N) conformed to the requirements of the American Petroleum Institute 5 L standard and that extracellular polymeric substances were present in the corrosion pits. The corrosion products mainly included FeCO3, FeS, CaCO3, MgCO3, and Fe mineralization. At 40°C, the uniform corrosion rate of L360N in the simulation experiment was 0.234 mm/a, and the local corrosion rate was 0.458 mm/a. SRB, saprophytes, and iron bacteria were detected in the on-site water medium and corrosion products, indicating that the main causes of shale gas pipeline corrosion are bacterial and CO2 corrosion. 相似文献
2.
Machine learning techniques play a preponderant role in dealing with massive amount of data and are employed in almost every possible domain. Building a high quality machine learning model to be deployed in production is a challenging task, from both, the subject matter experts and the machine learning practitioners.For a broader adoption and scalability of machine learning systems, the construction and configuration of machine learning workflow need to gain in automation. In the last few years, several techniques have been developed in this direction, known as AutoML.In this paper, we present a two-stage optimization process to build data pipelines and configure machine learning algorithms. First, we study the impact of data pipelines compared to algorithm configuration in order to show the importance of data preprocessing over hyperparameter tuning. The second part presents policies to efficiently allocate search time between data pipeline construction and algorithm configuration. Those policies are agnostic from the metaoptimizer. Last, we present a metric to determine if a data pipeline is specific or independent from the algorithm, enabling fine-grain pipeline pruning and meta-learning for the coldstart problem. 相似文献
3.
Location plays a major role in the building of artistic, technological or scientific movements that emerge in specific locations before achieving a worldwide reach. However, a deeper understanding is needed about the interplay of local/global knowledge dynamics in the epistemic construction of a movement. Based on an in-depth longitudinal study of a critical case, this article sheds light on these issues by analysing the case of ‘techno-emotional cuisine’, a global gastronomic movement initiated and led by chef Ferran Adrià and his team at the restaurant elBulli in Catalonia (in Northern Spain). The results suggest that the dynamics of formation of a new epistemic movement depend on the form and nature of the interactions between the local buzz and global pipelines, and on the capacity of the originating community to develop and diffuse the new rules and ‘episteme’ on a global scale while consolidating them locally. 相似文献
4.
Dionissios D. Papadias Jui-Kun Peng Rajesh K. Ahluwalia 《International Journal of Hydrogen Energy》2021,46(47):24169-24189
Recognizing the potential role of liquid hydrogen carriers in overcoming the inherent limitations in transporting and storing gaseous and liquid hydrogen, a complete production and use scenario is postulated and analyzed for perspective one-way and two-way carriers. The carriers, methanol, ammonia and toluene/MCH (methylcyclohexane), are produced at commercially viable scales in a central location, transmitted by rail or pipelines for 2000 miles, and decomposed near city gates to generate fuel-cell quality hydrogen for distribution to refueling stations. In terms of the levelized cost of H2 distributed to the stations, methanol is less expensive to produce ($1.22/kg-H2) than MCH ($1.35/kg-H2) or ammonia ($2.20/kg-H2). Levelized train transmission cost is smaller for methanol ($0.63/kg-H2) than ammonia ($1.29/kg-H2) or toluene/MCH system ($2.07/kg-H2). Levelized decomposition cost is smaller for ammonia ($0.30–1.06/kg-H2) than MCH ($0.54–1.22/kg-H2) or methanol ($0.43–1.12/kg-H2). Over the complete range of demand investigated, 10–350 tpd-H2, the levelized cost of H2 distributed to stations is aligned as methanol « ammonia ~ MCH. With pipelines at much larger scale, 6000 tpd-H2, the levelized cost decreases by ~1 $/kg-H2 for ammonia and MCH and much less for methanol. Methanol is a particularly attractive low-risk carrier in the transition phase with lower than 50-tpd H2 demand. 相似文献
5.
目的研究海底管道在点腐蚀和腐蚀疲劳双重影响下的整个破坏过程,基于动态贝叶斯网络构建系统失效模型,对海底管道系统不同疲劳寿命下的失效概率进行预测。方法将点蚀疲劳损伤过程分为腐蚀点成核、腐蚀坑增长、短裂纹扩展和长裂纹扩展四个阶段,采用蒙特卡洛模拟方法对腐蚀点形成到短裂纹发生前的管道破坏过程进行分析,结合疲劳裂纹扩展的动态贝叶斯网络结构图,在充分考虑相关影响因素不确定性的基础上,为海底点蚀管道系统提出一种创新性的概率分析方法,对点蚀管道疲劳寿命的失效概率进行科学预测。结果结合实例分析,通过蒙特卡洛模拟方法,求解得出腐蚀坑增长转变为短裂纹扩展状态的临界裂纹尺寸为0.8mm。采用动态贝叶斯网络分析方法,对未经受维修保养的点蚀管道进行疲劳寿命预测,当管道运行到第35年时将会面临失效风险。结论所构建的模型可以对海底点蚀管道腐蚀疲劳寿命失效概率进行合理预测,通过观测相关影响参数的变化,及时更新预测结果,有助于为海底管道系统制定有效的维修策略。 相似文献
6.
文中分析了国内外常用的几种外检测技术的检测原理及适用范围,包括交流电流衰减法、交流电位梯度法、直流电位梯度法、密间隔电位法、皮尔逊检测法,并对检测方法的组合应用进行了举例说明。 相似文献
7.
8.
9.
地下燃气管道导向钻进非开挖敷设技术 总被引:2,自引:7,他引:2
介绍了燃气工程中采用的地下管道导向钻进非开挖敷设技术基本原理、施工工艺及优缺点 相似文献
10.
本文利用随机振动理论 ,研究了地下管线在大空间地面运动过程中的动力反应问题。在建立管线模型时 ,接头简化为刚性接头 ,同时管线简化为弹性地基梁。在分析过程中 ,不考虑管线的弯曲应力和应变 ,仅考虑轴向应力和应变。采用随机反应分析的方法 ,通过输入地面运动的功率谱 ,求出管线在轴向的应力及应变的功率谱 相似文献