全文获取类型
收费全文 | 26686篇 |
免费 | 2810篇 |
国内免费 | 2218篇 |
专业分类
电工技术 | 3615篇 |
技术理论 | 3篇 |
综合类 | 2774篇 |
化学工业 | 2797篇 |
金属工艺 | 1605篇 |
机械仪表 | 2016篇 |
建筑科学 | 1272篇 |
矿业工程 | 542篇 |
能源动力 | 1587篇 |
轻工业 | 427篇 |
水利工程 | 492篇 |
石油天然气 | 987篇 |
武器工业 | 61篇 |
无线电 | 3557篇 |
一般工业技术 | 2651篇 |
冶金工业 | 257篇 |
原子能技术 | 232篇 |
自动化技术 | 6839篇 |
出版年
2024年 | 44篇 |
2023年 | 639篇 |
2022年 | 801篇 |
2021年 | 925篇 |
2020年 | 973篇 |
2019年 | 769篇 |
2018年 | 455篇 |
2017年 | 665篇 |
2016年 | 699篇 |
2015年 | 678篇 |
2014年 | 1553篇 |
2013年 | 1931篇 |
2012年 | 2924篇 |
2011年 | 2992篇 |
2010年 | 2199篇 |
2009年 | 2544篇 |
2008年 | 1654篇 |
2007年 | 2944篇 |
2006年 | 2648篇 |
2005年 | 1095篇 |
2004年 | 512篇 |
2003年 | 367篇 |
2002年 | 350篇 |
2001年 | 284篇 |
2000年 | 323篇 |
1999年 | 203篇 |
1998年 | 171篇 |
1997年 | 99篇 |
1996年 | 60篇 |
1995年 | 49篇 |
1994年 | 37篇 |
1993年 | 55篇 |
1992年 | 41篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1986年 | 2篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1976年 | 1篇 |
1959年 | 1篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Journal of Materials Science - Three polyimides (PIs) were prepared from a diamine containing biphenyl ester group as a side chain and a corresponding dianhydride chosen from... 相似文献
2.
Zhang Junbao Huang Haojun Yang Changlin Liu Jizhao Fan Yinting Yang Guan 《Wireless Networks》2022,28(3):1301-1312
Wireless Networks - Although centrality is widely used to differentiate the importance of nodes for social-aware routing in mobile opportunistic networks (MONs), it is destination-agnostic since... 相似文献
3.
《Ceramics International》2022,48(5):6266-6276
Porous diatomite ceramics with hierarchical pores and high apparent porosity (50.29–56%) were successfully fabricated via direct stereolithography. The pre-ball-milling time, dispersant type and dispersant concentration were systematically investigated to prepare diatomite pastes with high solid loading, low viscosity and a self-supporting effect. The results showed that a pre-ball-milling time of 24 h was more suitable to prepare diatomite pastes with high solid loading, and Span80 at 2 wt% was the optimal dispersant to obtain 40 vol% diatomite paste with a low viscosity and a self-supporting effect. To restrain the formation of defects, a heating rate as low as 0.2 °C/min was allowed to control the pyrolysis rate in the multistage debinding process. At sintering temperatures ranging from 900 °C to 1000 °C, porous diatomite ceramics exhibited a typical bimodal porosity, high apparent porosity and great flexural strength. 相似文献
4.
《Ceramics International》2022,48(20):29959-29966
High-purity SiC ceramic devices are applied in semiconductor industry owing to their outstanding properties. Nevertheless, it is difficult to densify SiC ceramics without any sintering additive even by HP sintering. In this work, high-purity and dense SiC ceramics were fabricated by HP sintering with very low amounts of sintering aids. Residual B content was only 556 ppm and relative density was more than 99.5%. Furthermore, thermal conductivity of as-prepared SiC ceramics was improved from 155 W m?1 K?1 to 167 W m?1 K?1 by increasing holding time and their plasma corrosion resistance was promoted in the meantime. The as-prepared high-purity SiC ceramics have broad application prospects in the field of semiconductor industry. 相似文献
5.
Knowledge and Information Systems - Crowdsourcing systems provide an efficient way to collect labeled data by employing non-expert crowd workers. In practice, each instance obtains a multiple noisy... 相似文献
6.
7.
为解决塔式光热的核心构筑物吸热塔"方变圆"变径超高筒体结构施工难题,选用一套可变形的滑模平台系统,通过操作系统上可调千斤顶支座、门架横向液压千斤顶装置、多处可调节模板角度和收缩模板的丝杆等,使得滑模根据施工需求可在一定的范围内调节模板倾角、间距,并逐步完成收缩变形,其理论滑模允许偏角20°,最终高效完成异形结构施工。该滑模系统刚度大、承载及堆料能力强、空间大、机械化程度高,施工操作简单,安全性高,适应沙漠极端环境。全过程仅需使用一套滑模体系,就能完成方形段、方变圆的变形段及圆形段施工,大大提高了施工效率,为类似环境下相似结构的施工提供了一定的参考。 相似文献
8.
9.
Everything you need to know about e-commerce. The term "e-commerce" refers to any commercial transaction type that requires the transmission of information over the Internet. By definition, it uses the Internet as a platform for communication and financial transactions or, at the same time, covering various business activities. In the previous method based on Deep learning and .net for Collaborative Innovation of E-Commerce platform. In the existing method, perception of security and reliability and data integrity and protection are drawbacks of the previous method. The proposed FPGA (Field-programmable gate array) and Convolutional Neural Network (CNN) are used to develop the Collaborative Innovation of E-Commerce platform and easily interface with the network without any complexity. E-commerce is an Internet-based tool, usually the exchange of Internet-based products and services. E-commerce refers to commercial transactions and commercial transactions involving exchange (e.g., money) within organizational or personal boundaries. The Web exchanges cross-organizational or personal boundary value (such as gold) for products and services for commercial transactions and commercial transactions. Here focus effectively on trade between digital companies and individuals. 相似文献
10.
N. Clament Sagaya Selvam Lijie Du Bao Yu Xia Pil J. Yoo Bo You 《Advanced functional materials》2021,31(12):2008190
Electroreduction of small molecules such as H2O, CO2, and N2 for producing clean fuels or valuable chemicals provides a sustainable approach to meet the increasing global energy demands and to alleviate the concern on climate change resulting from fossil fuel consumption. On the path to implement this purpose, however, several scientific hurdles remain, one of which is the low energy efficiency due to the sluggish kinetics of the paired oxygen evolution reaction (OER). In response, it is highly desirable to synthesize high-performance and cost-effective OER electrocatalysts. Recent advances have witnessed surface reconstruction engineering as a salient tool to significantly improve the catalytic performance of OER electrocatalysts. In this review, recent progress on the reconstructed OER electrocatalysts and future opportunities are discussed. A brief introduction of the fundamentals of OER and the experimental approaches for generating and characterizing the reconstructed active sites in OER nanocatalysts are given first, followed by an expanded discussion of recent advances on the reconstructed OER electrocatalysts with improved activities, with a particular emphasis on understanding the correlation between surface dynamics and activities. Finally, a prospect for clean future energy communities harnessing surface reconstruction-promoted electrochemical water oxidation will be provided. 相似文献