全文获取类型
收费全文 | 4911篇 |
免费 | 223篇 |
国内免费 | 237篇 |
专业分类
电工技术 | 146篇 |
综合类 | 275篇 |
化学工业 | 489篇 |
金属工艺 | 495篇 |
机械仪表 | 251篇 |
建筑科学 | 822篇 |
矿业工程 | 71篇 |
能源动力 | 123篇 |
轻工业 | 237篇 |
水利工程 | 120篇 |
石油天然气 | 87篇 |
武器工业 | 30篇 |
无线电 | 132篇 |
一般工业技术 | 698篇 |
冶金工业 | 1047篇 |
原子能技术 | 75篇 |
自动化技术 | 273篇 |
出版年
2024年 | 10篇 |
2023年 | 49篇 |
2022年 | 58篇 |
2021年 | 83篇 |
2020年 | 87篇 |
2019年 | 98篇 |
2018年 | 100篇 |
2017年 | 115篇 |
2016年 | 138篇 |
2015年 | 113篇 |
2014年 | 187篇 |
2013年 | 338篇 |
2012年 | 203篇 |
2011年 | 352篇 |
2010年 | 280篇 |
2009年 | 311篇 |
2008年 | 305篇 |
2007年 | 336篇 |
2006年 | 320篇 |
2005年 | 229篇 |
2004年 | 219篇 |
2003年 | 211篇 |
2002年 | 190篇 |
2001年 | 116篇 |
2000年 | 79篇 |
1999年 | 108篇 |
1998年 | 70篇 |
1997年 | 69篇 |
1996年 | 47篇 |
1995年 | 69篇 |
1994年 | 51篇 |
1993年 | 41篇 |
1992年 | 42篇 |
1991年 | 26篇 |
1990年 | 28篇 |
1989年 | 23篇 |
1988年 | 16篇 |
1987年 | 20篇 |
1986年 | 8篇 |
1985年 | 25篇 |
1984年 | 22篇 |
1983年 | 19篇 |
1982年 | 26篇 |
1981年 | 9篇 |
1965年 | 14篇 |
1961年 | 8篇 |
1960年 | 6篇 |
1957年 | 11篇 |
1955年 | 16篇 |
1954年 | 9篇 |
排序方式: 共有5371条查询结果,搜索用时 296 毫秒
51.
52.
53.
翁永基 《腐蚀科学与防护技术》2002,14(5):249-252
以塔里木和大港油田区域土壤腐蚀试验数据为例,论 证了区域腐蚀试验数据整体概率分布符合正态随机函数、其极大值数据符合Gumbel极值函数 .根据分布参数可以计算区内不同腐蚀性土壤比例、可能存在最大土壤腐蚀性和出现的概率 等工程信息. 相似文献
54.
无损检测的质量控制技术 总被引:1,自引:0,他引:1
以控制无损检测中的误判为例,介绍了质量控制技术在无损检测质量管理工作中的应用.首先利用流程图发现出现误判问题的产生环节,即缺陷的定位或定量错误.然后利用两图一表(因果图、排列图和检查表)分析引起缺陷定量或定位错误的原因.最后制定了防止误判产生的对策表.采用质量控制技术可以实现无损检测质量的持续改进. 相似文献
55.
This paper presents a novel approach to the problem of nondestructive pipeline testing using ultrasonic imaging. The identification of the flaw type and its dimensions are the most important problems in the pipeline inspection. Unlike typical methods, a decision based neural network is used for the detection of flaws. We train a generalized regression neural network to determine the dimensions of the corrosions and generate the whole image of both the internal and external walls of the oil pipeline. As an improvement to the detection algorithm, we introduce fuzzy decision-based neural network algorithms for the detection and classification of the corrosions. The simulation and experimental systems results show that these new methods outperform the existing methods. 相似文献
56.
无损检测的几个热点问题和技术 总被引:5,自引:0,他引:5
介绍当前无损检测领域几项快速发展的并受人普遍关注的热点问题和技术,如输油、输气管道和地下管网的在线监测、复合材料粘接层的检测、成像技术以及信号处理。介绍其基本原理、技术特点和近期进展。最后指出,当前新材料新领域的质量控制发展对无损检测技术提出了更高的要求和更广阔的应用空间。 相似文献
57.
Experiment and simulation study of 3D magnetic field sensing for magnetic flux leakage defect characterisation 总被引:1,自引:0,他引:1
Magnetic flux leakage (MFL) testing is widely used to detect and characterise defects in pipelines, rail tracks and other structures. The measurement of the two field components perpendicular to the test surface and parallel to the applied field in MFL systems is well established. However, it is rarely effective when the shapes of the specimens and defects with respect to the applied field are arbitrary. In order to overcome the pitfalls of traditional MFL measurement, measurement of the three-dimensional (3D) magnetic field is proposed. The study is undertaken using extensive finite element analysis (FEA) focussing on the 3D distribution of magnetic fields for defect characterisation and employing a high sensitivity 3-axis magnetic field sensor in experimental study. Several MFL tests were undertaken on steel samples, including a section of rail track. The experimental and FEA test results show that data from not only the x- and z-axes but also y-axis can give comprehensive positional information about defects in terms of shape and orientation, being especially advantageous where the defect is aligned close to parallel to the applied field. The work concludes that 3D magnetic field sensing could be used to improve the defect characterisation capabilities of existing MFL systems, especially where defects have irregular geometries. 相似文献
58.
X-ray microtomography (microCT) of the progression of sulfate attack of cement paste 总被引:2,自引:0,他引:2
High-resolution X-ray computed tomography (i.e., microCT or microtomography) was used to study the sulfate attack of cylinders of Type I cement paste cast with water-cement (w/c) ratios of 0.45, 0.50 and 0.60. Damage levels in samples exposed to a Na2SO4 solution with 10,000 ppm sulfate ion concentration were qualitatively rated from 0 (no damage) to 4 (extreme damage) based upon visual examination of the samples' exteriors and microtomography of the samples' interiors. The greater the w/c ratio, the more rapid the onset of sulfate damage. The corners of the cylinders appeared to be particularly susceptible to spalling, and damage may have continued into the cement paste by formation of subsurface cracks. 相似文献
59.
西北口水库大坝是我国建设的第一座百米级钢筋混凝土面板堆石坝,其百年一遇洪水渡汛水位降落幅度21.63 m,水位骤降速度最大可达3.65 m/h。面板尚未浇筑前的堆石坝体需临时拦洪渡汛,坝体垫层既起面板垫层作用,还要保证堆石坝体安全渡汛,水位骤降对垫层将产生拖拽力作用,影响到垫层的稳定性。本文通过面板堆石坝垫层渡汛离心模型试验,对不同渗透性垫层安全渡汛进行了试验研究,试验研究成果被西北口面板堆石坝工程施工期安全渡汛设计采纳,为面板坝工程建设特别是施工期安全渡汛提供了技术支撑。 相似文献
60.
In this paper, the design, simulation and experimental tests are presented for THROO: a Tracked Hybrid Rover, which has been developed to Overpass Obstacles. The proposed mobile robot has 3-DOFs and it is capable of straight motion, turning ability and two operations, namely rover-like motion with tracks on flat terrain and walking-like motion with track and legs to overpass obstacles to move on uneven terrain. The leg mechanism is composed of a four-bar linkage, which has been synthesized according to the desired features. In particular, the Burmester problem, which aims at finding the geometric parameters of a four-bar linkage required for a prescribed set of finitely separated poses are solved for the case understudy. Dynamic simulations have been carried out and a prototype has been built. The proposed results show the hybrid rover ability to overpass obstacles, for which size is comparable or greater than the track high. 相似文献