全文获取类型
收费全文 | 19417篇 |
免费 | 1192篇 |
国内免费 | 744篇 |
专业分类
电工技术 | 593篇 |
技术理论 | 6篇 |
综合类 | 1437篇 |
化学工业 | 2606篇 |
金属工艺 | 2196篇 |
机械仪表 | 1209篇 |
建筑科学 | 3586篇 |
矿业工程 | 1000篇 |
能源动力 | 687篇 |
轻工业 | 762篇 |
水利工程 | 222篇 |
石油天然气 | 498篇 |
武器工业 | 50篇 |
无线电 | 394篇 |
一般工业技术 | 1547篇 |
冶金工业 | 2942篇 |
原子能技术 | 167篇 |
自动化技术 | 1451篇 |
出版年
2024年 | 75篇 |
2023年 | 211篇 |
2022年 | 481篇 |
2021年 | 467篇 |
2020年 | 546篇 |
2019年 | 357篇 |
2018年 | 348篇 |
2017年 | 371篇 |
2016年 | 500篇 |
2015年 | 582篇 |
2014年 | 1128篇 |
2013年 | 1207篇 |
2012年 | 1326篇 |
2011年 | 1609篇 |
2010年 | 1218篇 |
2009年 | 1091篇 |
2008年 | 941篇 |
2007年 | 1202篇 |
2006年 | 1168篇 |
2005年 | 968篇 |
2004年 | 839篇 |
2003年 | 746篇 |
2002年 | 671篇 |
2001年 | 533篇 |
2000年 | 430篇 |
1999年 | 464篇 |
1998年 | 365篇 |
1997年 | 313篇 |
1996年 | 224篇 |
1995年 | 257篇 |
1994年 | 205篇 |
1993年 | 104篇 |
1992年 | 66篇 |
1991年 | 52篇 |
1990年 | 40篇 |
1989年 | 29篇 |
1988年 | 37篇 |
1987年 | 13篇 |
1986年 | 16篇 |
1985年 | 12篇 |
1984年 | 9篇 |
1983年 | 21篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1966年 | 7篇 |
1964年 | 7篇 |
1961年 | 9篇 |
1960年 | 6篇 |
1959年 | 8篇 |
1956年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
本文介绍了一种用于成品钢管生产线上的悬臂式钢管喷印装置,它是一台结构和功能都较复杂的大型机电一体化设备。文中简介了它的性能、特点和工作原理,对其各部分机械装置的构成及动作以及喷印控制系统的组成和功能进行了较为深入的描述。 相似文献
62.
Ali Hassanzadeh 《Corrosion Science》2007,49(4):1895-1906
In our previous works, the corrosion inhibition properties of propylamine (PA), iso-propylamine (i-PA), butylamine (BA), tert-butylamine (t-BA), hexylamine (HA), ethylenediamine (EDA), diethanolamine (DEA), 3-amino-1-propanol (3-AP), 2-dimethylethanolamine (2-DEA), cyclohexylamine (CHA), N-methylcyclohexylamine (N-MCA) and dicyclohexylamine (DCHA) have been investigated by means of electrochemical impedance spectroscopy (EIS) with a carbon steel rotating disc electrode in some petroleum/water corrosive mixtures containing acetic acid and NaCl at 25 °C. In this work, the Kramers-Kronig transformations (KKTs) were applied to evaluate the validity of the impedance data of these amine compounds in hydrodynamic condition. The results obtained showed that experimental impedance data did not satisfy in K-K relations completely viz. indicated some errors. These errors were related to stray capacitances, external transmission line effects, pits formation and change in interface during data acquisition at high and low frequencies regions. In addition, the selection of a suitable equivalent circuit strongly emphasized to better interpret of EIS data which in turn cause better resulted KKTs spectra. With considering obtained transformations, more effective inhibitor was selected with regard to its charge transfer resistance, the corrosion capacitance and well satisfying in K-K relations. 相似文献
63.
R. James Maguire Richard J. Tkacz David L. Sartor 《Journal of Great Lakes research》1985,11(3):320-327
Water and sediment samples from 29 locations in the Detroit and St. Clair rivers were analyzed for the highly toxic tri-n-butyltin (Bu3Sn+) species and for the less toxic di-n-butyltin (Bu2Sn2+) and n-butyltin (BuSn3+) species and inorganic tin. In general, locations sampled in the St. Clair River were less contaminated with butyltin species than those in the Detroit River. Inorganic tin and BuSn3+ were detected in over 90% of all subsurface water samples, while Bu2Sn2+ and Bu3Sn+ were detected in 45 and 28% of the same samples, respectively. The highest concentration ofBu3Sn+ in subsurface water, 5.9 × 10?10 mol Sn/L, was at the mouth of the Ecorse River, a tributary of the Detroit River. The three butyltin species and inorganic tin were also detected in 23–46% of all sediment samples. The highest concentrations of Bu3Sn+ in sediment were found close to the mouths of the River Rouge, another tributary of the Detroit River, and the Ecorse River, and were 6.2 × I0–7 and 1.7 × I0–7 mol Sn/kg dry weight, respectively, for the top 2 cm of sediment. 相似文献
64.
低温下“龙塔”材料的选择 总被引:1,自引:1,他引:0
结合黑龙江电视塔 (龙塔 ) ,就低温下钢塔材料的选择、结构选型与构造作了简要介绍。 相似文献
65.
兰州石化公司以加工新疆原油为主,重油收率高,平均在37%左右,所生产的重油主要靠催化裂化装置来加工,多余部分以低附加值重油出厂。随着涩宁兰天然气工程的逐渐建成,低附加值重油出厂将受到严重威胁,因此,催化裂化装置加工重油显得尤为重要。兰州石化公司炼油厂1.2Mt/a重催装置通过采用先进技术进行改造,使重油掺炼比由41.52%提高到52.20%,提高了10.68个百分点,年多加工重油14.95万t,产品收率达到79.20%以上,能够灵活调节产品结构,创造了良好的经济效益。 相似文献
66.
67.
吴正太 《精细石油化工进展》2007,8(6):42-46
采用中石化金陵分公司研究院研制的CI-50(Pd/丝光沸石)作C5/C6烷烃异构化催化剂.详细介绍了该催化剂的工业放大试验装置的工艺流程、首次开工过程中技术问题及处理方法. 相似文献
68.
69.
Morphology and Forming Mechanism of Rare Earth Inclusions During Solidification of Steel 总被引:2,自引:0,他引:2
翟启杰 《中国稀土学报(英文版)》1994,(3)
MorphologyandFormingMechanismofRareEarthInclusionsDuringSolidificationofSteel¥ZhaiQi-Jie(DepartmentofMetallurgy,UniversityofS... 相似文献
70.
Long term exposure tests have been carried out on a 3 NiCrMoV steam turbine disc steel in the form of cylindrical tensile test specimens self-loaded to 90% of σ0.2 and exposed to three environmental conditions, viz. deaerated pure water, aerated pure water, and aerated water containing 1.5 ppm of chloride ion. Pitting occurred in all environments but the density and depth of pits in the chloride-containing medium was markedly greater. No cracking was observed in deaerated pure water but cracks initiated in aerated water between 13 and 19 months and in less than 7 months in aerated 1.5 ppm Cl− solution. The probability of a crack initiating from a pit of specific depth in aerated solution could be described well by a Weibull function. Profiling of pits and cracks in the disc steel tested in aerated 1.5 ppm Cl− solution showed that there while there were many cracks with a depth greater than that of the corresponding pit the depth of some cracks was smaller than that of the corresponding pit, suggesting that cracks do not necessarily initiate from the bottom of the pits. The growth rate of short cracks emerging from pits appeared greater than that of long cracks in fracture mechanics specimens. 相似文献