全文获取类型
收费全文 | 109042篇 |
免费 | 10856篇 |
国内免费 | 6392篇 |
专业分类
电工技术 | 7100篇 |
技术理论 | 4篇 |
综合类 | 10093篇 |
化学工业 | 17730篇 |
金属工艺 | 5937篇 |
机械仪表 | 6159篇 |
建筑科学 | 8959篇 |
矿业工程 | 2941篇 |
能源动力 | 2908篇 |
轻工业 | 11526篇 |
水利工程 | 2289篇 |
石油天然气 | 4703篇 |
武器工业 | 933篇 |
无线电 | 12242篇 |
一般工业技术 | 11474篇 |
冶金工业 | 4259篇 |
原子能技术 | 1270篇 |
自动化技术 | 15763篇 |
出版年
2024年 | 563篇 |
2023年 | 1925篇 |
2022年 | 3583篇 |
2021年 | 4666篇 |
2020年 | 3635篇 |
2019年 | 3155篇 |
2018年 | 3259篇 |
2017年 | 3627篇 |
2016年 | 3205篇 |
2015年 | 4549篇 |
2014年 | 5804篇 |
2013年 | 6607篇 |
2012年 | 7342篇 |
2011年 | 7937篇 |
2010年 | 7362篇 |
2009年 | 6936篇 |
2008年 | 6958篇 |
2007年 | 6456篇 |
2006年 | 6142篇 |
2005年 | 4976篇 |
2004年 | 3909篇 |
2003年 | 3999篇 |
2002年 | 4904篇 |
2001年 | 4084篇 |
2000年 | 2555篇 |
1999年 | 1924篇 |
1998年 | 1194篇 |
1997年 | 980篇 |
1996年 | 947篇 |
1995年 | 773篇 |
1994年 | 577篇 |
1993年 | 402篇 |
1992年 | 330篇 |
1991年 | 229篇 |
1990年 | 178篇 |
1989年 | 143篇 |
1988年 | 126篇 |
1987年 | 68篇 |
1986年 | 60篇 |
1985年 | 51篇 |
1984年 | 35篇 |
1983年 | 25篇 |
1982年 | 19篇 |
1981年 | 11篇 |
1980年 | 30篇 |
1979年 | 16篇 |
1976年 | 4篇 |
1965年 | 2篇 |
1959年 | 9篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
This work is concerned with the prediction of visual colour difference between pairs of palettes. In this study, the palettes contained five colours arranged in a horizontal row. A total of 95 pairs of palettes were rated for visual difference by 20 participants. The colour difference between the palettes was predicted using two algorithms, each based on one of six colour-difference formulae. The best performance (r2 = 0.86 and STRESS = 16.9) was obtained using the minimum colour-difference algorithm (MICDM) using the CIEDE2000 equation with a lightness weighing of 2. There was some evidence that the order (or arrangement) of the colours in the palettes was a factor affecting the visual colour differences although the MICDM algorithm does not take order into account. Application of this algorithm is intended for digital design workflows where colour palettes are generated automatically using machine learning and for comparing palettes obtained from psychophysical studies to explore, for example, the effect of culture, age, or gender on colour associations. 相似文献
72.
Although Mg alloy attracts great attention for engineering applications because of high specific strength and low density, low corrosion resistance limits its extensive use. In this study, Mg–Al–Zn–Mn alloy was treated via a laser cladding process to generate a dense and compact laser cladding layer with solid metallurgical bonding on the substrate for improving corrosion resistance, effectively hindering the corrosion pervasion into Mg alloy. The corrosion current density declined from 103 μA/cm2 for Mg alloy to 13 μA/cm2 for the laser cladding layer in NaCl aqueous solution. Moreover, the laser cladding layer was slightly corroded in comparison with Mg alloy in NaCl aqueous solution. Besides, the microhardness of the cladding layer reached a mean value of 170.5 HV, 3.1 times of Mg alloy (56.8 HV) due to the in situ formation of hardening intermetallic phases. Wear resistance of laser cladding layer was also obviously improved. These results demonstrated that the laser cladding layer obviously enhanced anticorrosion property of Mg alloy for engineering applications. 相似文献
73.
The cover image is based on the Research Article Observer‐Based Cooperative Distributed Fault‐tolerant Model Predictive Control with Imperfect Network Communication and Asynchronous Measurements by Guannan Xiao and Fei Liu, https://doi.org/10.1002/rnc.4994 .
74.
User Modeling and User-Adapted Interaction - Personality plays a pivotal role at work. Many scholars have investigated the association between personality and language usage habits in the English... 相似文献
75.
Xiangrong Ma Rui Dang Ning Yang Xiao Li Ya zhang Ying Gong Zhipan Liu Wei Guo Yuanyuan Zhang Chunyan Li 《International Journal of Hydrogen Energy》2021,46(44):22842-22851
The high cost of noble metal catalysts has been a great bottleneck for the catalyst industry. Using the noble metal at a single-atom level for catalytic applications could dramatically decrease the cost. The impacts of single Pt atoms on the photocatalytic performance of Ag3VO4 have been investigated and reported. In this report, single Pt atoms were anchored on the surface of Ag3VO4 (AVO) as a cocatalyst, and the resultant composite photocatalyst has been studied for photocatalytic H2 production from water driven by visible light. The as-prepared AVO particles are hollow nanospheres in the monoclinic phase with a bandgap of 2.20 eV. The light absorption edge of AVO/Pt is slightly red-shifted compared to that of the pristine AVO, indicating more visible light absorption of AVO/Pt. The XPS peaks of Ag, V, and Pt exhibit a significant shift after AVO and Pt get into contact, suggesting the strong interaction between the surface Ag and V atoms, and single Pt atoms. After 3-h illumination, the photocatalytic H2 evolution amount from AVO/Pt is improved up to 1400 μmol, which is 2.8 times that on the bare AVO. Such efficient photocatalytic H2 evolution on AVO/Pt is still maintained after five reaction cycles. The better photocatalytic performance of AVO/Pt has been attributed to the more efficient visible light utilization and the lower interfacial charge transfer resistance, as demonstrated in the DRS and EIS spectra. The presence of the surface Pt atoms also leads to a higher amount of reactive radicals, which could efficiently promote the surface redox reactions. 相似文献
76.
77.
如何在海量不确定数据集中提高频繁模式挖掘性能是目前研究的热点.传统算法大多是以期望、概率或者权重等单一指标为数据项集支持度,在大数据背景下,同时考虑概率和权重支持度的算法难以兼顾其执行效率.为此,本文提出一种基于Spark的不确定数据集频繁模式挖掘算法(UWEFP),首先,为了同时兼顾数据项的概率和权重,计算一项集的最大概率权重值并进行剪枝;然后,为了减少对数据集的多次扫描,结合Spark框架的优点,设计了一种具有FP-tree特征的新颖的UWEFP-tree结构进行模式树的构建及挖掘;最后在Spark环境下,以UCI数据集进行实验验证.实验结果表明本文的方法在保证挖掘结果的同时,提高了效率. 相似文献
78.
The titanium carbides are potential candidates to achieve both high hardness and refractory property. We carried out a structural search for titanium carbides at three pressures of 0 GPa, 30 GPa and 50 GPa. A phase diagram of the Ti-C system at 0 K was obtained by elucidating formation enthalpies as a function of compositions, and their mechanical and metallic properties of titanium carbides were investigated systematically. We also discussed the relation of titanium concentration to the both mechanical and metallic properties of titanium carbides. It has been found that the average valence electron density and tractility improved at higher concentrations of titanium, while the degree of covalent bonding directionality decreased. To this effect, the hardness of titanium carbide decreases as the content of titanium increases. Our results indicated that the titanium content significantly affected the metallic properties of the Ti-C system. 相似文献
79.
入侵检测是保障网络安全的重要手段,针对现有入侵检测系统中告警数量多、协调性差等问题,论文提出了一种具有告警融合与关联功能的告警处理系统模型,该模型冗余告警量少、整体检测能力强,并能进行攻击企图的预测,能有效提高入侵检测的效率,有助于进一步增强网络的健壮性。 相似文献
80.
在充分考虑目前移动网络发展现状的基础上,对我国发展3G网络时与2G网络漫游的优势进行了深入的讨论,并提出漫游的解决方案。 相似文献