全文获取类型
收费全文 | 114968篇 |
免费 | 6170篇 |
国内免费 | 5345篇 |
专业分类
电工技术 | 9230篇 |
技术理论 | 3篇 |
综合类 | 8315篇 |
化学工业 | 13984篇 |
金属工艺 | 6061篇 |
机械仪表 | 7529篇 |
建筑科学 | 10899篇 |
矿业工程 | 5832篇 |
能源动力 | 2755篇 |
轻工业 | 12265篇 |
水利工程 | 5241篇 |
石油天然气 | 5618篇 |
武器工业 | 1280篇 |
无线电 | 11302篇 |
一般工业技术 | 9523篇 |
冶金工业 | 5068篇 |
原子能技术 | 1492篇 |
自动化技术 | 10086篇 |
出版年
2024年 | 956篇 |
2023年 | 3263篇 |
2022年 | 3779篇 |
2021年 | 3437篇 |
2020年 | 2932篇 |
2019年 | 3461篇 |
2018年 | 3357篇 |
2017年 | 1752篇 |
2016年 | 2052篇 |
2015年 | 2653篇 |
2014年 | 6551篇 |
2013年 | 4351篇 |
2012年 | 5459篇 |
2011年 | 5965篇 |
2010年 | 4790篇 |
2009年 | 4882篇 |
2008年 | 5122篇 |
2007年 | 5271篇 |
2006年 | 4889篇 |
2005年 | 4550篇 |
2004年 | 4204篇 |
2003年 | 3753篇 |
2002年 | 3167篇 |
2001年 | 2992篇 |
2000年 | 3246篇 |
1999年 | 3312篇 |
1998年 | 3043篇 |
1997年 | 2980篇 |
1996年 | 2865篇 |
1995年 | 2563篇 |
1994年 | 2270篇 |
1993年 | 1803篇 |
1992年 | 1885篇 |
1991年 | 1803篇 |
1990年 | 1739篇 |
1989年 | 1366篇 |
1988年 | 482篇 |
1987年 | 516篇 |
1986年 | 469篇 |
1985年 | 459篇 |
1984年 | 396篇 |
1983年 | 347篇 |
1982年 | 339篇 |
1981年 | 288篇 |
1980年 | 174篇 |
1979年 | 124篇 |
1978年 | 75篇 |
1975年 | 29篇 |
1965年 | 31篇 |
1959年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Jinfeng Zeng Zhiting Liu Hanbo Zou Wei Yang Haosen Fan Haijun Yu Shengzhou Chen 《金属学报(英文版)》2021,34(8):1153-1162
A appropriate size with three-dimension(3 D) channels for lithium diffusion plays an important role in constructing highperforming LiNi_(0.5)Mn_(1.5)O_4(LNMO) cathode materials, as it can not only reduce the transport path of lithium ions and electrons, but also reduce the side effects and withstand the structural strain in the process of repetitive Li~+ intercalation/deintercalation. In this work, an e fficient method for designing the hollow LNMO microsphere with 3 D channels structure by using polyethylene oxide(PEO) as soft template agent assisted solvothermal method is proposed. Experimental results indicate that PEO can make the reagents mingle evenly and nucleate slowly in the solvothermal process, thus obtaining a homogeneous distribution of carbonate precursors. In the final LNMO products, the hollow 3 D channels structure obtained by the decomposition of PEO and carbonate precursor in the calcination can provide abundant electroactive zones and electron/ion transport paths during the charge/discharge process, which benefits to improve the cycling performance and rate capability. The LNMO prepared by adding 1 g PEO possesses the most outstanding electrochemical performance, which presented an excellent discharge capacity of 143.1 mAh g~(-1) at 0.1 C and with a capacity retention of 92.2% after 100 cycles at 1 C. The superior performance attributed to the 3 D channels structure of hollow microspheres, which provide uninterrupted conductive systems and therefore achieve the stable transfer for electron/ion. 相似文献
2.
3.
In this study, a kind of Ni-based superalloy specially designed for additive manufacturing (AM) was investigated. Thermo-Calc simulation and differential scanning calorimetry (DSC) analysis were used to determine phases and their transformation temperature. Experimental specimens were prepared by laser metal deposition (LMD) and traditional casting method. Microstructure, phase constitution and mechanical properties of the alloy were characterized by scanning electron microscopy (SEM), transmission scanning electron microscopy (TEM), X-ray diffraction (XRD) and tensile tests. The results show that this alloy contains two basic phases, γ/γ', in addition to these phases, at least two secondary phases may be present, such as MC carbides and Laves phases. Furthermore, the as-deposited alloy has finer dendrite, its mean primary dendrite arm space (PDAS) is about 30-45 μm, and the average size of γ' particles is 100-150 nm. However, the dendrite size of the as-cast alloy is much larger and its PDAS is 300-500 μm with secondary and even third dendrite arms. Correspondingly, the alloy displays different tensile behavior with different processing methods, and the as-deposited specimen shows better ultimate tensile stress (1,085.7±51.7 MPa), yield stress (697±19.5 MPa) and elongation (25.8%±2.2%) than that of the as-cast specimen. The differences in mechanical properties of the alloy are due to the different morphology and size of dendrites, γ', and Laves phase, and the segregation of elements, etc. Such important information would be helpful for alloy application as well as new alloy development. 相似文献
4.
At present, the development and implementation of digital transformation are the keys to promoting high-quality industry development. The new digital fabrication method of robotic 3D printing is a research area being studied by many to tackle the issue of the declining productivity of traditional construction methods. Although many studies have been done, most of the current 3D printing projects are facing limitations in terms of scale. In order to bridge the gap, this article proposed a mass customization 3D printing framework system for large-scale projects. This article discusses how mass customization is made possible through the joint operation of the FUROBOT software and 3D printing hardware. By taking the east gate of Nanjing Happy Valley Plaza as a case study, the article demonstrates and studies the feasibility of the large-scale mass customization 3D printing framework system. 相似文献
5.
相较于现有防火规范,北京市《文物建筑防火设计规范》(DB 11/1706—2019)提出了文物建筑消防给水仅采用一套系统,不再区分室内消火栓和室外消火栓,且利用消火栓室外设置方式进行灭火扑救,因此对消防用水量、栓口压力、消火栓设置等有了相应的新设计要求。同时针对文物建筑灭火中运用较多的自动喷水灭火系统、气体灭火系统、移动式高压喷雾灭火装置、灭火器、消防水炮等,制定了详细的设计标准。对规范中重点设计条款进行了详细解释,可为设计人员更好地理解、应用此规范提供参考。 相似文献
7.
《热铁皮屋顶上的猫》是田纳西·威廉斯最有名的戏剧三部曲之一。在我国学界,对该剧中人物对"本真性"存在的追求尚未展开深入讨论。对存在主义者萨特来说,本真的人即是自由、负责任的人。威廉斯精心塑造了面临哈姆雷特式"跳还是不跳"的存在处境之"猫"的群像,无论是面临性取向认同、不迎自来的死神还是女性自我意识等存在处境,剧中的"猫"都做出了自由选择。威廉斯对本真性的思考与剖析以存在主义本真性为基础,有着丰富的内涵和意义。 相似文献
8.
针对近年来不断出现的高地温注浆加固问题,在室内模拟相应工程环境,测试了不同养护温度(20、40、60和80℃)对不同水灰比和组成的水泥基注浆体抗压强度的影响。结果表明:浆体的抗压强度随水灰比增大而降低,水灰比较大时,降低幅度变缓;3 d抗压强度随温度的升高而提高,14 d和28 d抗压强度则在低于40℃时随温度升高而提高,高于40℃时随温度升高而降低;水灰比越小,有助于浆体强度发展的温度阈值越低;20℃和40℃养护时,浆体的抗压强度随龄期延长而提高,而养护温度为80℃时,抗压强度随龄期延长呈降低趋势。对于水灰比为1.0的浆体,在20℃和40℃养护时,掺入6%和9%的膨润土可以提高其抗压强度,而在80℃养护时,反而降低其抗压强度。 相似文献
9.