全文获取类型
收费全文 | 86661篇 |
免费 | 6123篇 |
国内免费 | 2931篇 |
专业分类
电工技术 | 4353篇 |
技术理论 | 9篇 |
综合类 | 4649篇 |
化学工业 | 15513篇 |
金属工艺 | 4454篇 |
机械仪表 | 5232篇 |
建筑科学 | 7029篇 |
矿业工程 | 1985篇 |
能源动力 | 2480篇 |
轻工业 | 4901篇 |
水利工程 | 1447篇 |
石油天然气 | 4539篇 |
武器工业 | 488篇 |
无线电 | 10445篇 |
一般工业技术 | 11305篇 |
冶金工业 | 4687篇 |
原子能技术 | 831篇 |
自动化技术 | 11368篇 |
出版年
2024年 | 324篇 |
2023年 | 1314篇 |
2022年 | 2280篇 |
2021年 | 3118篇 |
2020年 | 2337篇 |
2019年 | 2034篇 |
2018年 | 2255篇 |
2017年 | 2518篇 |
2016年 | 2359篇 |
2015年 | 2942篇 |
2014年 | 4019篇 |
2013年 | 5071篇 |
2012年 | 5243篇 |
2011年 | 5519篇 |
2010年 | 4899篇 |
2009年 | 4716篇 |
2008年 | 4466篇 |
2007年 | 4402篇 |
2006年 | 4647篇 |
2005年 | 4133篇 |
2004年 | 2784篇 |
2003年 | 2497篇 |
2002年 | 2192篇 |
2001年 | 2019篇 |
2000年 | 2281篇 |
1999年 | 2560篇 |
1998年 | 2386篇 |
1997年 | 1886篇 |
1996年 | 1743篇 |
1995年 | 1446篇 |
1994年 | 1216篇 |
1993年 | 880篇 |
1992年 | 655篇 |
1991年 | 543篇 |
1990年 | 409篇 |
1989年 | 367篇 |
1988年 | 318篇 |
1987年 | 175篇 |
1986年 | 165篇 |
1985年 | 112篇 |
1984年 | 98篇 |
1983年 | 63篇 |
1982年 | 60篇 |
1981年 | 54篇 |
1980年 | 38篇 |
1979年 | 32篇 |
1978年 | 13篇 |
1977年 | 33篇 |
1976年 | 16篇 |
1975年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
121.
Hsiang-Cheh Huang Chi-Ming Chu Jeng-Shyang Pan 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2009,13(4):333-343
Applications for robust watermarking is one of the major branches in digital rights management (DRM) systems and related researches.
Based on existing experiences to evaluate the applicability of robust watermarking, it is generally agreed that three parameters
or requirements, including the quality of watermarked contents, the survivability of extracted watermark after deliberate
or unintentional attacks, and the number of bits embedded, need to be considered. However, performances relating to these
three parameters conflict with each other, and the trade off must be searched for. In this paper, we take all the three requirements
into consideration, and add the flexibility to meet the specific design in implementation. With the aid of genetic algorithm,
we design an applicable system that would obtain the good quality, acceptable survivability, and reasonable capacity after
watermarking. Simulation results present the effectiveness in practical implementation and possible application of the proposed
algorithm. 相似文献
123.
日益复杂的数字系统设计,须由各种专业的设计人员分工完成。他们之间需要一种描述系统的“共同语言”来沟通,这对于提高设计质量、缩短设计周期、减少设计费用具有积极意义。Petri网十分适合担任这一“共同语言”的角色。文章给出了数字电路测试仪器中的硬件设计的部分实例。 相似文献
124.
Based on the diffractive properties of a transmission-type phase volume hologram, a new type of polarization-division multi/demultiplexer for optical communications is presented. 相似文献
125.
This note describes the results of research into the anthropometric measurements of women in Taiwan, for use in pantihose design. 相似文献
126.
127.
佛手凉果是具有功能特性的岭南特色凉果品种,探究佛手凉果制作过程中功能性成分及其体外抗氧化活性变化规律,可为佛手凉果产业工艺优化与改良提供依据。结果表明,加工提高了佛手中总酸、多糖、黄酮和膳食纤维含量,导致多酚含量下降。制作过程中,1,1-二苯基-2-三硝基苯(DPPH)自由基、2,20 -联氮- 2 -三硝基苯肼(ABTS)自由基清除能力和铁离子还原抗氧化能力(Ferric Reducing Antioxidant Power, FRAP)呈现先下降后上升的趋势,效果分别是新鲜佛手的1.35倍、1.57倍和2.16倍。总黄酮与FRAP之间呈现极显著相关性(P<0.01);与DPPH、ABTS呈显著相关性(P<0.05);有机酸、总多糖分别与ABTS和FRAP之间相关性(P<0.05)。为此,在佛手凉果的制作过程中,糖制和干燥工艺对功能性成分的转化与浓缩起关键作用,可作为工艺优化的重点。 相似文献
128.
Shiyu Huang Yuan Chang Zhuwei Li Jiaqi Cao Yurou Song Junfeng Gao Licheng Sun Jungang Hou 《Advanced functional materials》2023,33(21):2211631
Photoredox catalysis is a green solution for organics transformation and CO2 conversion into valuable fuels, meeting the challenges of sustainable energy and environmental concerns. However, the regulation of single-atomic active sites in organic framework not only influences the photoredox performance, but also limits the understanding of the relationship for photocatalytic selective organic conversion with CO2 valorization into one reaction system. As a prototype, different single-atomic metal (M) sites (M2+ = Fe2+, Co2+, Ni2+, Cu2+, and Zn2+) in hydrogen-bonded organic frameworks (M-HOF) backbone with bridging structure of metal-nitrogen are constructed by a typical “two-in-one” strategy for superior photocatalytic C N coupling reactions integrated with CO2 valorization. Remarkably, Zn-HOF achieves 100% conversion of benzylamine oxidative coupling reactions, 91% selectivity of N-benzylidenebenzylamine and CO2 conversion in one photoredox cycle. From X-ray absorption fine structure analysis and density functional theory calculations, the superior photocatalytic performance is attributed to synergic effect of atomically dispersed metal sites and HOF host, decreasing the reaction energy barriers, enhancing CO2 adsorption and forming benzylcarbamic acid intermediate to promote the redox recycle. This work not only affords the rational design strategy of single-atom active sites in functional HOF, but also facilitates the fundamental insights upon the mechanism of versatile photoredox coupling reaction systems. 相似文献
129.
Ding Chun Wang Meimin Zhou Zhili Huang Teng Wang Xiaoliang Li Jin 《Neural computing & applications》2023,35(11):8125-8142
Neural Computing and Applications - As a fundamental technique for mining and analysis of remote sensing (RS) big data, content-based remote sensing image retrieval (CBRSIR) has received a lot of... 相似文献
130.
Dongsheng Xie Yue Zhang Xiyue Yuan Youle Li Fei Huang Yong Cao Chunhui Duan 《Advanced functional materials》2023,33(11):2212601
Semitransparent organic solar cells (ST-OSCs) have attracted increasing attention due to their promising prospect in building-integrated photovoltaics. Generally, efficient ST-OSCs with good average visible transmittance (AVT) can be realized by developing active layer materials with light absorption far from the visible light range. Herein, the development of ultrawide bandgap polymer donors with near-ultraviolet absorption, paired with near-infrared acceptors, is proposed to achieve high-performance ST-OSCs. The key points for the design of ultrawide bandgap polymers include constructing donor–donor type conjugated skeleton, suppressing the quinoidal resonance effect, and minimizing the twist of conjugated skeleton via noncovalent conformational locks. As a proof of concept, a polymer named PBOF with an optical bandgap of 2.20 eV is synthesized, which exhibited largely reduced overlap with the human eye photopic response spectrum and afforded a power conversion efficiency (PCE) of 16.40% in opaque device. As a result, ST-OSCs with a PCE over 10% and an AVT over 30% are achieved without optical modulation. Moreover, colorful ST-OSCs with visual aesthetics can be achieved by tuning the donor/acceptor weight ratio in active layer benefiting from the ultrawide bandgap nature of PBOF. This study demonstrates the great potential of ultrawide bandgap polymers for efficient colorful ST-OSCs. 相似文献