全文获取类型
收费全文 | 70040篇 |
免费 | 16534篇 |
国内免费 | 1127篇 |
专业分类
电工技术 | 2216篇 |
技术理论 | 1篇 |
综合类 | 1723篇 |
化学工业 | 22351篇 |
金属工艺 | 2473篇 |
机械仪表 | 2321篇 |
建筑科学 | 3390篇 |
矿业工程 | 796篇 |
能源动力 | 1358篇 |
轻工业 | 8881篇 |
水利工程 | 1021篇 |
石油天然气 | 2363篇 |
武器工业 | 203篇 |
无线电 | 9355篇 |
一般工业技术 | 17243篇 |
冶金工业 | 3302篇 |
原子能技术 | 1069篇 |
自动化技术 | 7635篇 |
出版年
2023年 | 292篇 |
2022年 | 649篇 |
2021年 | 1131篇 |
2020年 | 2175篇 |
2019年 | 3792篇 |
2018年 | 3856篇 |
2017年 | 4270篇 |
2016年 | 4632篇 |
2015年 | 4964篇 |
2014年 | 5074篇 |
2013年 | 6448篇 |
2012年 | 4264篇 |
2011年 | 3902篇 |
2010年 | 3986篇 |
2009年 | 3876篇 |
2008年 | 3335篇 |
2007年 | 3162篇 |
2006年 | 2821篇 |
2005年 | 2357篇 |
2004年 | 2266篇 |
2003年 | 2334篇 |
2002年 | 2646篇 |
2001年 | 2306篇 |
2000年 | 1742篇 |
1999年 | 966篇 |
1998年 | 375篇 |
1997年 | 360篇 |
1996年 | 319篇 |
1995年 | 270篇 |
1990年 | 255篇 |
1989年 | 276篇 |
1986年 | 262篇 |
1985年 | 269篇 |
1984年 | 283篇 |
1983年 | 272篇 |
1982年 | 261篇 |
1981年 | 253篇 |
1980年 | 257篇 |
1979年 | 281篇 |
1978年 | 358篇 |
1977年 | 334篇 |
1976年 | 348篇 |
1975年 | 329篇 |
1974年 | 394篇 |
1973年 | 372篇 |
1972年 | 357篇 |
1971年 | 329篇 |
1970年 | 280篇 |
1969年 | 277篇 |
1968年 | 267篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
2.
Ya Gu Quanmin Zhu Hassan Nouri 《International Journal of Adaptive Control and Signal Processing》2022,36(1):138-154
This article presents a state-space model with time-delay to map the relationship between known input-output data for discrete systems. For the given input-output data, a model identification algorithm combining parameter estimation and state estimation is proposed in line with the causality constraints. Consequently, this article proposes a least squares parameter estimation algorithm, and analyzes its convergence for the studied systems to prove that the parameter estimation errors converge to zero under the persistent excitation conditions. In control system design, the U-model based control is introduced to provide a unilateral platform to improve the design efficiency and generality. A simulation portfolio from modeling to control is provided with computational experiments to validate the derived results. 相似文献
3.
Kravchenko V. F. Konovalov Ya. Yu. 《Journal of Communications Technology and Electronics》2022,67(8):952-964
Journal of Communications Technology and Electronics - A new design of wavelets based on the convolution of a compactly supported function with a rectangular pulse is proposed and theoretically... 相似文献
4.
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
5.
A novel CdS/CaFe2O4 (CS/CFO) heterogeneous p-n junction was created by thermal deposition of CaFe2O4 nanoparticles on CdS rods. The CS/CFO hetero-structured photocatalysts exhibited increasingly efficient visible light harvesting compared to the bare CdS. The CS/CFO composites also presented higher photocurrent and slower decay of photoluminescence, suggesting a better separation of the photo-generated electrons and holes. The photocatalytic H2 evolution quantity on the optimized CS/CFO composite from water in the presence of ethanol was up to 2200 μmol after 3-h visible light illumination, which is more than twice that of the pristine CdS. The chemical interaction between CdS and CaFe2O4 was confirmed by the shifts in the XPS peaks, which made it possible for the charge carriers to transfer across the p-n junction interface. This research highlights the importance of forming an interfacial p-n heterojunction between two semiconductors for efficient charge separation and improved photocatalytic performance. 相似文献
6.
A new aqueous slurry-based laminated object manufacturing process for porous ceramics is proposed: firstly, an organic mesh sheet is pre-paved as a pore-forming template before slurry layer scraping; secondly, the 2D pattern is built with laser outline cutting of the dried mesh–ceramic composite layer; finally, the pore structure is formed after degreasing and sintering. Alumina parts with porosities of 51.5 %, round hole diameters of 80 ± 5 μm were fabricated using 70 wt. % solid content slurry and 100 mesh nylon net. Using an organic mesh as the framework and template not only reduces the risk of damage of the green body but also ensures the regularity, uniformity and connectivity of the micron scaled pore network. The layer-by-layer drying method avoids the delamination phenomenon and improves the paving density. The new method can realize the flexible design of the pore structure by using various organic mesh templates. 相似文献
7.
Uzun İlhan Orak İkram Yağmur Hatice Karaer Karakaplan Mehmet Yalman Murat 《SILICON》2021,13(12):4703-4713
Silicon - 5-(2,4-dichlorophenyl)-2-furoic acid and anthraquinone-2-carboxylic acid were reacted separately with chitin. The synthesized products were characterized by various spectroscopic methods... 相似文献
8.
综述了铁素体与铁素体异种金属焊缝(dissimilar metal welds,DMWs)接头界面组织及其影响。结果表明,在焊后热处理或运行温度下的铁素体钢DMWs接头的不均匀界面组织中,通常会形成脱碳层和增碳层。在铁素体钢DMWs焊接接头界面组织影响因素中,焊缝金属的化学成分有重要影响;焊后热处理规范(温度和时间)、工作温度下运行时间的影响较为突出;焊接工艺参数的影响亦不可忽略。异种钢接头界面处近缝区裂纹的产生,以及接头的蠕变强度随Larson Miller 参数增大而下降等不利影响,均为异种钢界面碳迁移行为所导致。焊缝成分控制法是接头界面组织控制或改善的必要条件,而脱碳层部位转移法能有效防止裂纹发生,亦是接头安全运行的重要工艺措施之一。 相似文献
9.
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
10.
Fluorescence‐Activated Cell Sorters: Standing Surface Acoustic Wave (SSAW)‐Based Fluorescence‐Activated Cell Sorter (Small 40/2018) 下载免费PDF全文