全文获取类型
收费全文 | 7516篇 |
免费 | 860篇 |
国内免费 | 485篇 |
专业分类
电工技术 | 68篇 |
综合类 | 831篇 |
化学工业 | 1857篇 |
金属工艺 | 49篇 |
机械仪表 | 106篇 |
建筑科学 | 2300篇 |
矿业工程 | 954篇 |
能源动力 | 232篇 |
轻工业 | 652篇 |
水利工程 | 658篇 |
石油天然气 | 60篇 |
武器工业 | 17篇 |
无线电 | 124篇 |
一般工业技术 | 401篇 |
冶金工业 | 88篇 |
原子能技术 | 13篇 |
自动化技术 | 451篇 |
出版年
2024年 | 31篇 |
2023年 | 96篇 |
2022年 | 165篇 |
2021年 | 246篇 |
2020年 | 248篇 |
2019年 | 208篇 |
2018年 | 189篇 |
2017年 | 270篇 |
2016年 | 329篇 |
2015年 | 334篇 |
2014年 | 507篇 |
2013年 | 624篇 |
2012年 | 507篇 |
2011年 | 601篇 |
2010年 | 499篇 |
2009年 | 450篇 |
2008年 | 460篇 |
2007年 | 581篇 |
2006年 | 522篇 |
2005年 | 382篇 |
2004年 | 343篇 |
2003年 | 247篇 |
2002年 | 197篇 |
2001年 | 152篇 |
2000年 | 139篇 |
1999年 | 119篇 |
1998年 | 85篇 |
1997年 | 58篇 |
1996年 | 50篇 |
1995年 | 50篇 |
1994年 | 49篇 |
1993年 | 19篇 |
1992年 | 20篇 |
1991年 | 16篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有8861条查询结果,搜索用时 15 毫秒
51.
一种新颖的室温固化双组分水性木器涂料与相应的单组分涂料相比,其显著特点涂膜有极好的附着力、更高的硬度、优异的耐水、耐烫、耐溶剂和抗粘连及耐污渍性等。其配漆后的适用期室温下可达30d以上,涂料的综合性能可与溶剂型漆相媲美。 相似文献
52.
著名的景德镇松柴窑,简称镇窑,已属于宝贵的历史文化遗产。其建造、生产过程及烧制的瓷器,正是该文化遗产的具体内容。着重介绍这些概念和内容,说明新建个别小型柴窑,恢复其制瓷烧造,不仅可以产生很大经济效益;对保护景德镇传统陶瓷文化更具有积极的社会价值。 相似文献
53.
Various softwood and hardwood bark residues, primary sludges and softwood sawdust residues were processed by vacuum pyrolysis in a laboratory scale batch reactor. The pyrolysis oil, water, charcoal, and gas were recovered and analyzed. The pyrolysis oils were analyzed in details for their content in phenolic compounds after derivatization to their acetyl derivatives. The influence of temperature, heating rate, feedstock bed thickness, particle size and feedstock water pretreatment on the yield of phenols was investigated. The highest yield of phenols was obtained when hardwood bark was soaked in water for 48 hours and pyrolyzed at a temperature of 450°C and a heating rate of 10°C/min. Pyrolysis performance was evaluated in terms of total phenolic yield and composition. 相似文献
54.
The objective of this work was to demonstrate the utility of lignin-based resins designed for application as an adhesive in the production of particleboard. Bond qualities of lignin-phenol-formaldehyde resins, phenolated-lignin-formaldehyde resins and commercial phenol-formaldehyde (PF-com) resin were assessed by using an automatic bonding evaluation system, prior to production of particleboards. In order to evaluate the quality of lignin-based resins, particleboards were produced and physical and mechanical properties were investigated. These physical properties included internal bond, modules of rupture and modulus of elasticity. Thickness swell and water absorption properties of particleboards bonded with lignin-based resins were also determined. The lignin-based resins have been reported previously in Part I of this study. The results showed that particleboards bonded with phenolated-lignin formaldehyde resins (up to 30% lignin content) exhibited similar physical and mechanical properties when compared to particleboards bonded with PF-com. The work has indicated that phenolated-lignin formaldehyde resins (up to 30% substitution level) can be used successfully as a wood adhesive for constructing particleboard. The performance of these panels is comparable to those of boards made using PF-com resin. 相似文献
55.
This article aimed to investigate the mechanical, morphological and thermal properties of PVC/LDPE blend with and without the addition of compatibilizers. The effects of LDPE content, compatibilizer type and rubber‐wood sawdust loading on the properties of the blend were evaluated. The experimental results suggested that as the LDPE content was increased the mechanical properties of PVC‐LDPE blend progressively decreased due to poor interfacial adhesion. The continuity and compatibility between PVC and LDPE phases could be improved through three different types of compatibilizers which included chlorinated polyethylene (CPE) poly(methyl‐methacrylate‐co‐butyl acrylate) (PA20) and poly(ethylene‐co‐methacrylate) (Elvaloy). The PA20 was found to be the most suitable compatibilizer for the blend. A radical transfer reaction was proposed in this work to explain the structure and thermal changes of the PVC in PVC‐LDPE blend. The decomposition temperature of PVC in the blend decreased with the loading of the PA20 and the wood sawdust. As the sawdust content was increased the tensile and flexural moduli increased with considerable decreased in the tensile, flexural and impact strength, a slight improvement being achieved if the PA20 was incorporated in the composite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 598–606, 2006 相似文献
56.
Preparation of HDPE/SEBS‐g‐MAH and its effect on mechanical properties of HDPE/wood flour composites
In this article, high density polyethylene/styrene‐ethylene‐butylene‐styrene block copolymer blends (HDPE/SEBS) grafted by maleic anhydride (HDPE/SEBS‐g‐MAH), which is an effective compatibilizer for HDPE/wood flour composites was prepared by means of torque rheometer with different contents of maleic anhydride (MAH). The experimental results indicated that MAH indeed grafted on HDPE/SEBS by FTIR analysis and the torque increased with increasing the content of maleic anhydride and dicumyl peroxide (DCP). Styrene may increase the graft reaction rate of MAH and HDPE/SEBS. When HDPE/SEBS MAH was added to HDPE/wood flour composites, tensile strength and flexural strength of composites can reach 25.9 and 34.8 MPa in comparison of 16.5 and 23.8 MPa (without HDPE/SEBS‐g‐MAH), increasing by 157 and 146%, respectively. Due to incorporation of thermoplastic elastomer in HDPE/SEBS‐g‐MAH, the Notched Izod impact strength reached 5.08 kJ m?2, increasing by 145% in comparison of system without compatibilizer. That HDPE/SEBS‐g‐MAH improved the compatibility was also conformed by dynamic mechanical measurement. Scanning electron micrographs provided evidence for strong adhesion between wood flour and HDPE matrix with addition of HDPE/SEBS‐g‐MAH. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
57.
In this study, phenolated wood resin was used an adsorbent for the removal of Cr(III), Ni(II), Zn(II), Co(II) ions by adsorption from aqueous solution. The adsorption of metal ions from solution was carried at different contact times, concentrations and pHs at room temperature (25°C). For individual metal ion, the amount of metal ions adsorbed per unit weight of phenolated wood resin at equilibrium time increased with increasing concentration and pH. Also, when the amounts of metal ions adsorbed are compared to each other, it was seen that this increase was order of Cr(III) > Ni(II) > Zn(II) > Co(II). This increase was order of Cr(III) > Ni(II) > Co(II) > Zn(II) for commercial phenol–formaldehyde resin. Kinetic studies showed that the adsorption process obeyed the intraparticle diffusion model. It was also determined that adsorption isotherm followed Langmuir and Freundlich models. Adsorption isotherm obtained for commercial phenol–formaldehyde resin was consistent with Freundlich model well. Adsorption capacities from Langmuir isotherm for commercial phenol–formaldehyde resin were higher than those of phenolated wood resin, in the case of individual metal ions. Original adsorption isotherm demonstrated the monolayer coverage of the surface of phenolated wood resin. Adsorption kinetic followed the intraparticle diffusion model. The positive values of ΔG° determined using the equilibrium constants showed that the adsorption was not of spontaneous nature. It was seen that values of distribution coefficient (KD) decreasing with metal ion concentration in solution at equilibrium (Ce) indicated that the occupation of active surface sites of adsorbent increased with metal ions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2838–2846, 2006 相似文献
58.
木粉/低密度聚乙烯复合材料的发泡研究 总被引:1,自引:1,他引:1
用模压法制备木粉/低密度聚乙烯发泡材料。通过差示量热扫描分析,考察了纯偶氮二甲酰胺(AC)及与 ZnO共混物、纯NaHCO3及与柠檬酸(L)共混物的热分解特性,探讨了发泡剂AC、NaHCO3、柠檬酸、交联剂过氧化二异丙苯等对材料力学性能的影响,并在扫描电镜下观察了材料断面的微观形态。结果表明:采用放热发泡剂和复合发泡剂都能使复合材料密度下降20%左右,发泡后材料的冲击性能为发泡前体系的1.5倍左右;复合发泡剂的发泡效果优于单放热发泡剂的效果。 相似文献
59.
针对农村生活污水直接排放已经成为影响我国农村水环境质量主要因素之一的现状,从适合我国农村的以村落或居民点为单位进行生活污水分散式处理的思维入手,介绍了我国现今主要的分散式生活污水处理技术的原理、特点、不足及其应用现状;继而综合比较了这些技术的技术经济指标,提出了适合我国农村的分散式生活污水处理技术的设计原则;最后提出发展有较高水力负荷,并具备小规模设备化特征和多种生物处理单元复合的创新技术是我国农村生活污水处理技术发展的主要方向。 相似文献
60.
目的 分析格兰杰因果关系检验模型,应用格兰杰因果检验模型检验房地产市场中的地价与房价之间的因果关系.方法 修正了沈阳市地价与房价的环比价格指数,对沈阳市地价与房价之间的关系进行平稳性检验,协整检验和格兰杰因果检验.结果 沈阳市房价是地价的格兰杰原因,房价的上涨会带动地价的上涨;而地价不是房价的格兰杰原因,但地价作为房价的重要组成部分,对房价有一定的影响作用.土地只是构成房地产的一个生产要素,其需求的变化是受房屋市场需求变化影响的,房屋市场供不应求,价格上涨,才使开发商对土地的需求增加,造成地价上涨.结论 土地招标、拍卖和挂牌政策的实施不是造成房价上涨的主要原因. 相似文献