全文获取类型
收费全文 | 50915篇 |
免费 | 3980篇 |
国内免费 | 2832篇 |
专业分类
电工技术 | 860篇 |
综合类 | 4149篇 |
化学工业 | 11018篇 |
金属工艺 | 6663篇 |
机械仪表 | 2882篇 |
建筑科学 | 9466篇 |
矿业工程 | 2065篇 |
能源动力 | 916篇 |
轻工业 | 2356篇 |
水利工程 | 1460篇 |
石油天然气 | 1354篇 |
武器工业 | 321篇 |
无线电 | 974篇 |
一般工业技术 | 8963篇 |
冶金工业 | 3159篇 |
原子能技术 | 231篇 |
自动化技术 | 890篇 |
出版年
2024年 | 156篇 |
2023年 | 757篇 |
2022年 | 1416篇 |
2021年 | 1803篇 |
2020年 | 1612篇 |
2019年 | 1418篇 |
2018年 | 1511篇 |
2017年 | 1903篇 |
2016年 | 1944篇 |
2015年 | 2271篇 |
2014年 | 3136篇 |
2013年 | 3649篇 |
2012年 | 3400篇 |
2011年 | 4098篇 |
2010年 | 2800篇 |
2009年 | 2890篇 |
2008年 | 2552篇 |
2007年 | 2955篇 |
2006年 | 2700篇 |
2005年 | 2320篇 |
2004年 | 1981篇 |
2003年 | 1785篇 |
2002年 | 1532篇 |
2001年 | 1236篇 |
2000年 | 1092篇 |
1999年 | 932篇 |
1998年 | 737篇 |
1997年 | 630篇 |
1996年 | 538篇 |
1995年 | 440篇 |
1994年 | 356篇 |
1993年 | 280篇 |
1992年 | 199篇 |
1991年 | 147篇 |
1990年 | 135篇 |
1989年 | 121篇 |
1988年 | 69篇 |
1987年 | 57篇 |
1986年 | 18篇 |
1985年 | 23篇 |
1984年 | 19篇 |
1983年 | 16篇 |
1982年 | 28篇 |
1981年 | 11篇 |
1980年 | 16篇 |
1979年 | 18篇 |
1964年 | 4篇 |
1961年 | 2篇 |
1959年 | 2篇 |
1954年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Micro assembly injection moulding 总被引:1,自引:0,他引:1
Injection moulding is established as one of the most common manufacturing processes of thermoplastics due to its high degree of automation and the short cycle times. Micro injection moulding is a rapidly growing technology that allows for the efficient production of very complex micro parts in high series. The “Market Analysis for Microsystems II 2002–2005” of the Nexus Task Force anticipates a yearly growth in the field of micro system technology of about 20% (Wechsung et al. 2002). This study identifies in addition to the continuous miniaturization the growing use of polymers in micro systems (Schneider et al. 2001). No other material group offers this wide range of material properties and permits to choose processing parameters and application properties according to necessities (Gächter 2000). While the production processes of micro technical components are mainly controllable, the assembly of these components to hybrid micro systems is a bottleneck to the industrial large scale production. The assembly itself represents a large fraction of the added product value and gains in importance with growing complexity and miniaturization of the systems. 相似文献
92.
CMP系统技术与市场 总被引:3,自引:1,他引:2
葛劢冲 《电子工业专用设备》2003,32(1):17-24
概述了CMP系统技术的发展历史、发展趋势以及在IC生产中的重要性,介绍了国外CMP设备主要制造厂家的设备型号和性能及CMP设备市场分布和需求,阐述了CMP系统技术的基础研究、关键技术和国内研究概况。 相似文献
93.
94.
Namshik Ahn 《应用聚合物科学杂志》2003,90(4):991-1000
The bond strengths of polymer concretes containing up to 15% (based on polymer resin) of diacrylate (DA) monomers were examined and compared with those without DA. A change occurring with the addition of DA monomers was an increase in the bond strength of polymer concrete to wet substrates. Zinc diacrylate (ZDA) and calcium diacrylate (CDA) were each used as an additive to monomers and resins [methyl methacrylate (MMA), polyester, and two kinds of epoxies]. The variables were amount of the DA monomers and surface conditions (wet or dry and smooth or rough). Bond strengths were measured by tension bond. ZDA was found to improve the bond strength of MMA and polyester, whereas CDA improved the bond strength of epoxies. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 991–1000, 2003 相似文献
95.
The work describes various physical and chemical treatments to eliminate the deleterious effects of impurities in phosphogypsum on the delayed setting time and impaired strength development behaviour of cement to which it was added as a set regulator. The physical treatments included washing, milling, and ultrasonic treatment of the material, while the chemical treatments dealt with acidic and basic additions to the phosphogypsum during the washing stage. It was found that chemical treatment with a milk of lime solution, which is often recommended in literature, was ineffective in reducing set retardation. Treatment with ammonium hydroxide or sulphuric acid was more effective in this regard. Intergrinding phosphogypsum with slaked lime improved its effectiveness in reducing set retardation, but the use of unslaked lime was less effective and also resulted in marked reductions in compressive strengths. A combined treatment of wet milling phosphogypsum with a lime slurry in a ball mall was derived from these experiments and is recommended for full-scale plant applications. 相似文献
96.
The aim of this work was to establish the important parameters that control the hot compaction behaviour of woven oriented polypropylene. Five commercial woven cloths, based on four different polypropylene polymers, were selected so that the perceived important variables could be studied. These include the mechanical properties of the original oriented tapes or fibres, the geometry of the oriented reinforcement (fibres or tapes), the mechanical properties of the base polymer (which are crucially dependant on the molecular weight and morphology), and the weave style. The five cloths were chosen so as to explore the boundaries of these various parameters, i.e. low and high molecular weight: circular or rectangular reinforcement (fibres or tapes): low or high tape initial orientation: coarse or fine weave.A vital aspect of this study was the realisation that hot compacted polypropylene could be envisaged as a composite, comprising an oriented ‘reinforcement’ bound together by a matrix phase, formed by melting and recrystallisation of the original oriented material. We have established the crucial importance of the properties of the melted and recrystallised matrix phase, especially the level of ductility, in controlling the properties of the hot compacted composite. 相似文献
97.
根据石油开采业对石油机械产品的需求 ,利用机械理论基础知识 ,通过实践设计 ,提出了对几何尺寸长的金属管类进行调质处理后的均匀冷却方法 ,以满足其性能要求。 相似文献
98.
99.
从孔隙水的存在状态出发 ,围绕Bishop抗剪强度公式中存在的几个疑点展开讨论 .认为非饱和土中支配强度和变形的应力之所以不同 ,是因为非饱和土中存在一种性质与有效应力不同的应力———内部应力 ,它不传递 ,仅影响土的塑性变形 .同时还对Bishop ,Fredlund和卢肇钧提出的抗剪强度公式中的参数测试方法进行分析 ,指出 :各种抗剪强度理论在概念上都是相同的 ,其区别仅在于确定由吸力产生的那部分有效应力时采用的参数和测试方法不同 相似文献
100.
通过加入增强剂、增韧剂、抗氧剂等添国剂可改善聚丙烯力学性能。以SiO2为填料,丁苯橡胶(SBS)为增韧剂,探讨SiO2、丁苯橡胶含量对共混体系强度、韧性的影响,结果表明,在SBS含量大于5%、SiO2一小于10%的范围内,可使PP/SiO2/SBS复合的拉伸弹性模量和冲击强度明显提高,其力学性能均为均衡。 相似文献