全文获取类型
收费全文 | 25587篇 |
免费 | 2830篇 |
国内免费 | 2094篇 |
专业分类
电工技术 | 598篇 |
综合类 | 2545篇 |
化学工业 | 1787篇 |
金属工艺 | 3287篇 |
机械仪表 | 2753篇 |
建筑科学 | 3890篇 |
矿业工程 | 879篇 |
能源动力 | 555篇 |
轻工业 | 927篇 |
水利工程 | 687篇 |
石油天然气 | 1962篇 |
武器工业 | 566篇 |
无线电 | 1079篇 |
一般工业技术 | 6739篇 |
冶金工业 | 947篇 |
原子能技术 | 501篇 |
自动化技术 | 809篇 |
出版年
2024年 | 116篇 |
2023年 | 400篇 |
2022年 | 751篇 |
2021年 | 915篇 |
2020年 | 953篇 |
2019年 | 823篇 |
2018年 | 797篇 |
2017年 | 959篇 |
2016年 | 1111篇 |
2015年 | 1148篇 |
2014年 | 1428篇 |
2013年 | 1525篇 |
2012年 | 1572篇 |
2011年 | 1917篇 |
2010年 | 1359篇 |
2009年 | 1436篇 |
2008年 | 1309篇 |
2007年 | 1475篇 |
2006年 | 1442篇 |
2005年 | 1253篇 |
2004年 | 1076篇 |
2003年 | 894篇 |
2002年 | 843篇 |
2001年 | 746篇 |
2000年 | 651篇 |
1999年 | 574篇 |
1998年 | 458篇 |
1997年 | 424篇 |
1996年 | 410篇 |
1995年 | 291篇 |
1994年 | 231篇 |
1993年 | 212篇 |
1992年 | 180篇 |
1991年 | 167篇 |
1990年 | 142篇 |
1989年 | 108篇 |
1988年 | 85篇 |
1987年 | 48篇 |
1986年 | 38篇 |
1985年 | 46篇 |
1984年 | 48篇 |
1983年 | 41篇 |
1982年 | 47篇 |
1981年 | 4篇 |
1980年 | 21篇 |
1979年 | 8篇 |
1966年 | 3篇 |
1965年 | 3篇 |
1964年 | 3篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
101.
提出底敞口充气浮箱的结构和概念。经模型模拟试验研究分析,经典浮力定律可用于这种浮箱的浮力计算;其动充气状况还具有一定的允许伤损面积。它的研究将为水陆两用车辆增大浮力,缩小外形,提高水上自下而上能力和潜驶潜伏提供具有诱惑力的工程应用前景。 相似文献
102.
C. M. Branco J. M. Ferreira M. O. W. Richardson P. Fael 《International Journal of Fatigue》1992,14(6):367-376
This paper presents results of a fatigue life investigations carried out in plate specimens of a fibre-glass-reinforced phenolic matrix composite. Tensile and Young's modulus data were obtained at four different testing temperatures (room temperature, 100, 150 and 200 °C). The fatigue S−N data were obtained at room temperature only and for two stress ratio values (R=0 and 0.4). Fatigue and tensile behaviour was assesesed in the composite with the fibres aligned in the longitudinal loading direction. The results were obtained for two values of volume fraction (0.28 and 0.42) and three different glass surface treatments. A detailed comparison of fatigue results is given taking into account several fatigue parameters and also the testing variables. Results of observations of SEM fracture surfaces are also presented. 相似文献
103.
104.
105.
高含酸性气碳酸盐岩气藏流体敏感性实验研究 总被引:2,自引:0,他引:2
对川东北雷口坡组、嘉陵江组、飞仙关组、长兴组高含H,S及032的碳酸盐岩储层流体敏感性进行了实验研究,结果表明岩样速敏损害弱~强,水敏和盐敏损害中偏弱~极强,碱敏损害严重。岩石学分析揭示,川东北高含酸性气碳酸盐岩储层发育伊利石、微晶石英、白云石、方解石、硫化钙等潜在损害物质。钻井完井液侵入会破坏储层各物质间的原始动态平衡,诱发储层损害。主要损害机理为:①储层流体pH增加引起黏土矿物以及微晶石英失稳;②碱液与微晶石英、长石、白云石反应生成硅酸盐、高岭石、水镁石等新矿相;③流体矿化度改变可降低伊利石微粒间的连接力;④硫化钙水解产生OH^-,过量的OH-与Ca^2+结合形成氢氧化钙沉淀;⑤储层含水饱和度和流体离子浓度改变,致使焦沥青脱附并在储层深部沉积;⑥硬石膏水化膨胀、分散运移。针对该气藏损害机理,可采用屏蔽暂堵技术以形成优质滤饼,有效降低储层流体敏感性损害。图5表2参10。 相似文献
106.
107.
108.
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
109.
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
110.
In-phase(IP) and out-of-phase(OP)thermal-mechanical fatigue(TMF) behavior of cast Ni-base superalloy K417 was studied.All experiments were carried out under total strain control with temperature cycling between 400-850℃.Both in-phase and out-of-phase TMF specimens exhibited cyclic hardening followed by cyclic softening at the minimum temperature.Besides,they cyclically hardened in the early stage of life followed by cyclic softening at the minimum temperature.Besides,they cyclically hardened in the early stage of life followed by cyclic softening at the maximum temperature.OP TMF life was longer than of IP TMF.Various damage mechanisms operating in different controlled strain ranges and phasing were discussed.A few life prediction methods for isothermal fatigue were used to handle TMF fatigue and their applicability to superalloy K417 was evaluated.The SEM analysis of the fracture surface showed that transgranular fracture was the principal cracking mode for both IP and OP TMF.Oxidation was the main damage mechanism in causing shorter fatigue life for IP TMF compared with OP TMF. 相似文献