全文获取类型
收费全文 | 110151篇 |
免费 | 11103篇 |
国内免费 | 5487篇 |
专业分类
电工技术 | 7081篇 |
技术理论 | 7篇 |
综合类 | 11310篇 |
化学工业 | 10757篇 |
金属工艺 | 6757篇 |
机械仪表 | 3596篇 |
建筑科学 | 32177篇 |
矿业工程 | 4678篇 |
能源动力 | 2414篇 |
轻工业 | 5963篇 |
水利工程 | 11183篇 |
石油天然气 | 4481篇 |
武器工业 | 864篇 |
无线电 | 6523篇 |
一般工业技术 | 8612篇 |
冶金工业 | 5697篇 |
原子能技术 | 912篇 |
自动化技术 | 3729篇 |
出版年
2024年 | 179篇 |
2023年 | 1211篇 |
2022年 | 2583篇 |
2021年 | 3161篇 |
2020年 | 3386篇 |
2019年 | 2760篇 |
2018年 | 2754篇 |
2017年 | 3360篇 |
2016年 | 3790篇 |
2015年 | 4213篇 |
2014年 | 7197篇 |
2013年 | 5564篇 |
2012年 | 8160篇 |
2011年 | 8459篇 |
2010年 | 6214篇 |
2009年 | 7082篇 |
2008年 | 6608篇 |
2007年 | 8238篇 |
2006年 | 7076篇 |
2005年 | 6127篇 |
2004年 | 4991篇 |
2003年 | 4509篇 |
2002年 | 3825篇 |
2001年 | 3271篇 |
2000年 | 2645篇 |
1999年 | 2122篇 |
1998年 | 1519篇 |
1997年 | 1172篇 |
1996年 | 1029篇 |
1995年 | 811篇 |
1994年 | 684篇 |
1993年 | 442篇 |
1992年 | 370篇 |
1991年 | 274篇 |
1990年 | 198篇 |
1989年 | 164篇 |
1988年 | 129篇 |
1987年 | 100篇 |
1986年 | 48篇 |
1985年 | 55篇 |
1984年 | 33篇 |
1983年 | 25篇 |
1982年 | 35篇 |
1981年 | 23篇 |
1980年 | 45篇 |
1979年 | 8篇 |
1975年 | 8篇 |
1964年 | 11篇 |
1959年 | 12篇 |
1956年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 23 毫秒
21.
Dominik KUERES Dritan TOPUZI Maria Anna POLAK 《Frontiers of Structural and Civil Engineering》2022,16(5):624
In the past, glass fiber-reinforced polymer (GFRP)-reinforcement has been successfully applied in reinforced concrete (RC) structures where corrosion resistance, electromagnetic neutrality, or cuttability were required. Previous investigations suggest that the application of GFRP in RC structures could be advantageous in areas with seismic activity due to their high deformability and strength. However, especially the low modulus of elasticity of GFRP limited its wide application as GFRP-reinforced members usually exhibit considerably larger deformations under service loads than comparable steel-reinforced elements. To overcome the aforementioned issues, the combination of steel and GFRP reinforcement in hybrid RC sections has been investigated in the past. Based on this idea, this paper presents a novel concept for the predetermination of potential plastic hinges in RC frames using GFRP reinforcement. To analyze the efficiency of the concept, nonlinear finite element simulations were performed. The results underscore the high efficiency of hybrid steel-GFRP RC sections for predetermining potential plastic hinges on RC frames. The results also indicate that the overall seismic behavior of RC structures could be improved by means of GFRP as both the column base shear force during the seismic activity as well as the plastic deformations after the earthquake were considerably less pronounced than in the steel-reinforced reference structure. 相似文献
22.
为解决电镀砂轮磨削加工中容屑空间不足的问题,采用点胶微粘接的方法制备了磨料有序排布的电镀砂轮,分析了磨料粘接效果和镀层力学性能。通过SEM分析了磨料/镀层/导电胶的结合界面,并进行了干磨削试验。研究结果表明,直径约为磨料粒径40%的胶点可粘接住磨料,单个胶点上粘接多颗磨料的占比小于6%;双脉冲电镀工艺制备的镀层显微硬度大于500HV,表层残余应力小于100MPa,磨料/镀层/导电胶之间的界面贴合紧密,无明显缺陷;砂轮在磨削时没有出现磨料脱落现象。 相似文献
23.
Yutaka Sawada Hiroshi Nakazawa W. Andy Take Toshinori Kawabata 《Geotextiles and Geomembranes》2019,47(4):502-513
This paper reports results of full scale testing to further explore potential GCL damage mechanisms in earth dam retrofit applications in seismically active areas; in particular, to a) investigate whether shear displacements could reduce the magnitude of GCL panel overlap during earthquake shaking; b) explore the influence of gravel particles on GCL thickness at localised point of contact; and c) observe the consequences of an accidental exposure of an uncovered GCL to short duration rainfall in terms of moisture content and effects during subsequent compaction. The results of these experiments indicate that even under severe shaking no movements were detected at the GCL panel overlap. Whereas gravel particles were observed to locally reduce the thickness of the GCL to 2.2 mm, no plowing of the particle into the GCL occurred due to a lack of shear displacement at the interface, resulting in no localised internal erosion through the barrier. Furthermore, hydration of GCL panels during construction due to surface wetting was observed to result in a state of hydration less than its post-construction state. These results indicate that although each of the three GCL damage mechanisms cannot be ruled out to ever be relevant in practice, the performance of the GCL retrofitted earth dam tested was satisfactory under even severe Level 2 earthquake shaking, and suggests that the retrofitting of small earth dams with GCLs is a promising strategy to improve their static and seismic resistance. 相似文献
24.
针对常见泥石流防治结构被冲击破坏的问题,基于“柔性消能”理念,结合张弦梁结构和竖向预应力锚杆技术,提出一种既能改善结构受力性能、增加结构整体抗冲击能力、保证结构安全可靠,又能减小结构构件截面尺寸、节约成本、便于现场施工组装和后期运营维护的新型地锚张弦梁式泥石流格栅坝,并阐述其技术原理。根据泥石流荷载分布和新型地锚张弦梁式泥石流格栅坝的受力特征,给出其简化的内力计算方法;并利用SAP2000建立新结构有限元模型,分析了结构的整体受力,验证了构件简化计算方法的合理性;结合Python语言和Qt De? signer软件开发了相应的设计计算软件,对新型地锚张弦梁式泥石流格栅坝的内力进行求解。结果表明:提出的新结构抗冲击性能好,构件受力均匀;以后设计中应关注竖杆的剪切脆性破坏和立柱偏心受力情况,保证结构安全;变形协调仅使底层张弦梁与竖杆内力偏大,实际工程应用时,应着重验算底层构件,防止其破坏;文中提出的简化计算方法能较准确的反映结构的受力特性,具有一定的合理性,研究可为新型地锚张弦梁式泥石流格栅坝的设计计算和推广应用提供理论依据和技术支持。 相似文献
25.
公路建设不断发展,对公路的要求越来越高。彩色沥青混凝土有多种特殊用途,被广泛应用和普及。本文就彩色沥青混凝土的应用进行了分析研究。 相似文献
26.
Michele Faccia Giuseppe Natrella Giuseppe Gambacorta 《International Journal of Food Science & Technology》2021,56(10):5352-5361
High moisture mozzarella from cow milk is a pasta filata cheese that can be manufactured by different protocols. Fermentation by autochthonous starter is used for the traditional product, whereas direct acidification with citric acid is widely used at industrial level. Both types are stored immersed in a liquid for preserving freshness, but this packaging method is known to favour the changes of the quality characteristics. The present study aimed to assess the evolution of the soluble compounds and to evaluate their use as chemical indices for discriminating the two types of mozzarella. The contents of lactose, organic acids, water-soluble nitrogen and free amino acids differently changed over time. The whole patterns of these soluble compounds allowed discrimination of the two products during the whole storage period. The simple analyses of lactic acid and lactose could be a rapid tool to protect traditional mozzarella from industrial imitations obtained with citric acid. 相似文献
27.
《Ceramics International》2022,48(18):26233-26247
A new type of 3D-printable ‘one-part’ geopolymer was synthesized with fly ash (FA), granulated blast furnace slag (GBFS), steel slag (SS) and flue gas desulfurization gypsum (FGD). The effects of SS content (0–40%) on the rheological properties, 3D-printability, mechanical anisotropy and reaction kinetics of geopolymer were investigated. The yield stress and plastic viscosity monotonically decreased with the increasing SS content. Contrarily, the geopolymer with 10% of SS presented better extrudability, buildability and mechanical strength than those with 0, 20%, 30% and 40% of SS. This was mainly attributed to the conflicting influence of SS on geopolymerization, of which the OH? produced by hydration of SS raised the alkalinity of the reaction system and accelerated the dissolution of SiO44? and AlO45?, while the low reactivity prohibited the following polymerization process. Furthermore, the 3D-printed geopolymer presented more compact microstructure and less mechanical anisotropy thanks to the crosslinking of morphologically complementary products, including N(C)-A-S-H, C–S–H, AFt and CH, formed via synergistic reaction of FA-GBFS-SS-FGD system. 相似文献
28.
Mining high utility itemsets (HUIs) from transaction databases considers such factors as the unit profit and quantity of purchased items. Two-phase tree-based algorithms transform a database into compressed tree structures and generate candidate patterns through a recursive pattern-growth procedure. This procedure requires a lot of memory and time to construct conditional pattern trees. To address this issue, this study employs two compressed tree structures, namely, Utility Count Tree and String Utility Tree, to enumerate valid patterns and thus promote fast utility computation. Furthermore, the study presents an algorithm called single-phase utility computation (SPUC) that leverages these two tree structures to mine HUIs in a single phase by incorporating novel pruning strategies. Experiments conducted on both real and synthetic datasets demonstrate the superior performance of SPUC compared with IHUP, UP-Growth, and UP-Growth+ algorithms. 相似文献
29.
30.