全文获取类型
收费全文 | 48989篇 |
免费 | 15663篇 |
国内免费 | 478篇 |
专业分类
电工技术 | 1296篇 |
综合类 | 710篇 |
化学工业 | 19322篇 |
金属工艺 | 983篇 |
机械仪表 | 1498篇 |
建筑科学 | 2489篇 |
矿业工程 | 261篇 |
能源动力 | 1221篇 |
轻工业 | 7863篇 |
水利工程 | 463篇 |
石油天然气 | 569篇 |
武器工业 | 81篇 |
无线电 | 8329篇 |
一般工业技术 | 12869篇 |
冶金工业 | 1054篇 |
原子能技术 | 162篇 |
自动化技术 | 5960篇 |
出版年
2024年 | 70篇 |
2023年 | 228篇 |
2022年 | 376篇 |
2021年 | 699篇 |
2020年 | 1783篇 |
2019年 | 3440篇 |
2018年 | 3425篇 |
2017年 | 3818篇 |
2016年 | 4215篇 |
2015年 | 4305篇 |
2014年 | 4404篇 |
2013年 | 5632篇 |
2012年 | 3416篇 |
2011年 | 3152篇 |
2010年 | 3314篇 |
2009年 | 3157篇 |
2008年 | 2636篇 |
2007年 | 2452篇 |
2006年 | 2218篇 |
2005年 | 1788篇 |
2004年 | 1737篇 |
2003年 | 1846篇 |
2002年 | 1850篇 |
2001年 | 1589篇 |
2000年 | 1390篇 |
1999年 | 734篇 |
1998年 | 268篇 |
1997年 | 223篇 |
1996年 | 203篇 |
1995年 | 153篇 |
1994年 | 120篇 |
1993年 | 89篇 |
1992年 | 71篇 |
1991年 | 82篇 |
1990年 | 48篇 |
1989年 | 41篇 |
1988年 | 26篇 |
1987年 | 23篇 |
1986年 | 33篇 |
1985年 | 20篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1970年 | 1篇 |
1890年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
目的:设计一款满足安全、卫生、操作便捷、结构性能稳定等要求的糖霜制品3D打印机.方法:打印机主要包括机械结构和控制系统,机械结构方面采用龙门架结构,并对传统的打印料罐进行改良.控制系统采用“工控机+运动控制卡”的模式.结果:该打印机可快速更换料罐(30s内),打印机成型速度快(≥5000mm/min),速度可调;成型精度控制在1mm 以内;成型件的强度、膨胀率和表面粗糙度指标均较好.自带光源的图像识别及处理系统能够识别产品形状、个数及完整性等.结论:改良后的料罐提高了半流体食品打印的卫生性、生产效率,且便于耗材的更换,能加工出复杂糖画模型以满足造型独特的个性化糖艺制品的需求. 相似文献
2.
Bijan Nasri‐Nasrabadi Akif Kaynak Shayan Seyedin Zahra Komeily‐Nia Abbas Z Kouzani 《Polymer International》2019,68(5):922-928
Recent advances in three‐dimensional (3D) printing have enabled the fabrication of interesting structures which are not achievable using traditional fabrication approaches. The 3D printing of carbon microtube composite inks allows fabrication of conductive structures for practical applications in soft robotics and tissue engineering. However, it is challenging to achieve 3D printed structures from solution‐based composite inks, which requires an additional process to solidify the ink. Here, we introduce a wet 3D printing technique which uses a coagulation bath to fabricate carbon microtube composite structures. We show that through a facile nanogrooving approach which introduces cavitation and channels on carbon microtubes, enhanced interfacial interactions with a chitosan polymer matrix are achieved. Consequently, the mechanical properties of the 3D printed composites improve when nanogrooved carbon microtubes are used, compared to untreated microtubes. We show that by carefully controlling the coagulation bath, extrusion pressure, printing distance and printed line distance, we can 3D print composite lattices which are composed of well‐defined and separated printed lines. The conductive composite 3D structures with highly customised design presented in this work provide a suitable platform for applications ranging from soft robotics to smart tissue engineering scaffolds. © 2019 Society of Chemical Industry 相似文献
3.
Tongling Xia Yue Qi Xilei Dai Jinyu Liu Can Xiao Ruoyu You Dayi Lai Junjie Liu Chun Chen 《Indoor air》2021,31(6):2020-2032
To evaluate the separate impacts on human health and establish effective control strategies, it is crucial to estimate the contribution of outdoor infiltration and indoor emission to indoor PM2.5 in buildings. This study used an algorithm to automatically estimate the long-term time-resolved indoor PM2.5 of outdoor and indoor origin in real apartments with natural ventilation. The inputs for the algorithm were only the time-resolved indoor/outdoor PM2.5 concentrations and occupants’ window actions, which were easily obtained from the low-cost sensors. This study first applied the algorithm in an apartment in Tianjin, China. The indoor/outdoor contribution to the gross indoor exposure and time-resolved infiltration factor were automatically estimated using the algorithm. The influence of outdoor PM2.5 data source and algorithm parameters on the estimated results was analyzed. The algorithm was then applied in four other apartments located in Chongqing, Shenyang, Xi'an, and Urumqi to further demonstrate its feasibility. The results provided indirect evidence, such as the plausible explanations for seasonal and spatial variation, to partially support the success of the algorithm used in real apartments. Through the analysis, this study also identified several further development directions to facilitate the practical applications of the algorithm, such as robust long-term outdoor PM2.5 monitoring using low-cost light-scattering sensors. 相似文献
4.
5.
6.
Fangjun Zhu You Shi Guorong Hu Zhongdong Peng Yanbing Cao Qian Sun Zhichen Xue Yinjia Zhang Ke Du 《Ceramics International》2021,47(3):3070-3078
Titanium and boron are simultaneously introduced into LiNi0.8Co0.1Mn0.1O2 to improve the structural stability and electrochemical performance of the material. X-ray diffraction studies reveal that Ti4+ ion replaces Li+ ion and reduces the cation mixing; B3+ ion enters the tetrahedron of the transition metal layers and enlarges the distance of the [LiO6] layers. The co-doped sample has spherical secondary particles with elongated and enlarged primary particles, in which Ti and B elements distribute uniformly. Electrochemical studies reveal the co-doped sample has improved rate performance (183.1 mAh·g-1 at 1 C and 155.5 mAh·g-1 at 10 C) and cycle stability (capacity retention of 94.7% after 100 cycles at 1 C). EIS and CV disclose that Ti and B co-doping reduces charge transfer impedance and suppresses phase change of LiNi0.8Co0.1Mn0.1O2. 相似文献
7.
Karolina Storesund Francine Amon Anne Steen‐Hansen Shayesteh Haghighatpanah Ida Larsson 《火与材料》2021,45(1):181-190
The aim of this exploratory study has been to investigate the fire properties and environmental aspects of different upholstery material combinations, mainly for domestic applications. An analysis of the sustainability and circularity of selected textiles, along with lifecycle assessment, is used to qualitatively evaluate materials from an environmental perspective. The cone calorimeter was the primary tool used to screen 20 different material combinations from a fire performance perspective. It was found that textile covers of conventional fibres such as wool, cotton and polyester, can be improved by blending them with fire resistant speciality fibres. A new three‐dimensional web structure has been examined as an alternative padding material, showing preliminary promising fire properties with regard to ignition time, heat release rates and smoke production. 相似文献
8.
铁煤集团大兴矿(以下简称"大兴矿")2019年产240万t,井田位于铁法煤田的西南角,火成岩侵入及地质构造复杂,煤层破坏程度严重[1-2]。受火成岩影响,煤层瓦斯含量大幅增加[3-4],渗透性能差,力学强度低,煤的含水率低,自然发火期较短,是煤与瓦斯突出矿井。在采煤过程中,防治自然发火是重中之重,综采设备在设计初期未考虑实施灭火的操作空间,为此,笔者提出通过改造综采设备增加实施灭火的操作空间,降低出现自然发火灾害时防治的难度,保证采煤安全。 相似文献
9.
Fluorescence‐Activated Cell Sorters: Standing Surface Acoustic Wave (SSAW)‐Based Fluorescence‐Activated Cell Sorter (Small 40/2018) 下载免费PDF全文