全文获取类型
收费全文 | 52068篇 |
免费 | 4988篇 |
国内免费 | 4646篇 |
专业分类
电工技术 | 1489篇 |
综合类 | 3471篇 |
化学工业 | 10877篇 |
金属工艺 | 13772篇 |
机械仪表 | 2419篇 |
建筑科学 | 4925篇 |
矿业工程 | 1152篇 |
能源动力 | 879篇 |
轻工业 | 1480篇 |
水利工程 | 964篇 |
石油天然气 | 4877篇 |
武器工业 | 661篇 |
无线电 | 1923篇 |
一般工业技术 | 8091篇 |
冶金工业 | 2431篇 |
原子能技术 | 794篇 |
自动化技术 | 1497篇 |
出版年
2024年 | 285篇 |
2023年 | 856篇 |
2022年 | 1554篇 |
2021年 | 1939篇 |
2020年 | 1929篇 |
2019年 | 1713篇 |
2018年 | 1648篇 |
2017年 | 2150篇 |
2016年 | 2170篇 |
2015年 | 2112篇 |
2014年 | 2962篇 |
2013年 | 3289篇 |
2012年 | 3374篇 |
2011年 | 4077篇 |
2010年 | 3070篇 |
2009年 | 3212篇 |
2008年 | 2656篇 |
2007年 | 3149篇 |
2006年 | 3100篇 |
2005年 | 2482篇 |
2004年 | 2325篇 |
2003年 | 2014篇 |
2002年 | 1724篇 |
2001年 | 1395篇 |
2000年 | 1153篇 |
1999年 | 1002篇 |
1998年 | 759篇 |
1997年 | 677篇 |
1996年 | 527篇 |
1995年 | 482篇 |
1994年 | 367篇 |
1993年 | 295篇 |
1992年 | 256篇 |
1991年 | 210篇 |
1990年 | 169篇 |
1989年 | 145篇 |
1988年 | 81篇 |
1987年 | 66篇 |
1986年 | 55篇 |
1985年 | 46篇 |
1984年 | 40篇 |
1983年 | 24篇 |
1982年 | 52篇 |
1981年 | 15篇 |
1980年 | 28篇 |
1979年 | 18篇 |
1978年 | 8篇 |
1975年 | 6篇 |
1959年 | 7篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
低碳微合金钢中的晶内铁素体及组织控制 总被引:1,自引:0,他引:1
回顾和评述了晶内铁素体的发现、发展及其与组织控制的关系.介绍了晶内铁素体的形核机制和影响晶内铁素体形成的因素,讨论了晶内铁素体的三维形态和长大动力学,并从以上几方面分析了晶内铁素体对低碳微合金钢组织细化的重要作用和影响. 相似文献
92.
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
93.
94.
中山包水电站钢岔管在天生桥二级水电站 6号压力钢管下平段分岔 ,岔管HD值达 15 40m2 ,结构体形复杂 ,采用NK HITEN780A Z35和NK HITEN6 90B高强度钢材制造安装 ,在国内水电工程中实际应用较少。文章着重介绍岔管的布置、结构分析和焊缝的无损检验要求。中山包水电站的正常发电运行 ,为 80kg/mm2 级高强钢在国内水电行业的应用提供了第 3个成功实例 相似文献
95.
A nanocrystalline coating of K38G alloy was obtained by means of magnetron sputtering. The corrosion behavior of cast K38G alloy and its sputtered nanocrystalline coating with a solid NaCl deposit in dry air or wet oxygen at 600 and 700°C have been studied and compared. The results indicated that the mass gain of the coating is higher than that of the cast alloy at 600 and 700°C. Therefore, nanocrystallization reduced the corrosion resistance at these temperatures. Furthermore, the mass gains of the coating and the cast alloy with a NaCl deposit in wet oxygen were less than that with a NaCl deposit in dry air. The relevant corrosion mechanisms are discussed. 相似文献
96.
蒸馏与减粘热联合装置的设备腐蚀及防护 总被引:4,自引:2,他引:2
介绍了锦西石化分公司南蒸馏与减粘热联合装置炼制辽河高酸值原油及带炼高硫进口油在 2 0 0~40 0℃范围内对设备、管线和阀门的腐蚀特点、腐蚀机理以及针对高温环烷酸腐蚀所采取的防护措施。通过试验和理论分析 ,提出了应用新材料和新工艺解决减粘后高温渣油系统的腐蚀及低温露点腐蚀的建议 相似文献
97.
Melting and crystallization behaviour of elastoplastic semicrystalline copolymers: poly(ether ester)
The melting and crystallization behaviour of an elastoplastic semi-crystalline poly(etherester) has been studied by differential scanning calorimetry. The shape of the melting endotherm is strongly dependent on heating rate and annealing time and results from the sum of simultaneous melting and crystallization phenomena. Samples prepared by different techniques, i.e. by solvent evaporation or by melt extrusion, behave very differently owing to specific crystal morphologies. By applying the Hoffman-Weeks plot, the equilibrium melting temperature has been extrapolated. The Avrami treatment allows the calculation of the index n and of the rate constant K from the isothermal kinetic data. 相似文献
98.
The present paper will outline the main aspects of the design and construction of cooling towers in Germany in the last decade. As part of electricity generating power plants, cooling towers play a significant role for the availability of reliable energy supplies, in a manner compatible with environmental requirements. They definitely belong to the largest and thinnest concrete structures at present. Because of the combined action of wind, thermal and moisture effects, special care has to be taken with regard to fatigue, cracking and corrosion to ensure an adequate level of safety and durability. Such a design strategy has been employed for the world’s tallest cooling tower at the Niederaussem power plant in Germany, with an overall height of 200 m and thickness values of 22–24 cm. Special considerations included the realistic non-axisymmetric distribution of soil characteristics, wind action due to interference effects (as determined by wind-tunnel tests), optimisation of the shell shape to improve structural and dynamic behaviour, injection of the cleaned flue-gas into the cooling tower, and the use of high-performance concrete (85 MPa) to improve shell resistance against acid attack by the cleaned flue-gas. The paper will present some results of an actual research project on this problem, which was conducted at the University of Wuppertal, to explore the use of high-performance concrete on design, stability and durability of cooling tower shells. 相似文献
99.
100.
通过电化学极化曲线和失重实验,研究了氨荒酸盐对铜在氯化钠溶液中的缓蚀性能,并与相应胺的缓蚀性能进行了对比。结果表明:氨荒酸盐对铜具有较好的缓蚀性能。 相似文献