全文获取类型
收费全文 | 73185篇 |
免费 | 8828篇 |
国内免费 | 5488篇 |
专业分类
电工技术 | 6285篇 |
技术理论 | 1篇 |
综合类 | 7574篇 |
化学工业 | 9563篇 |
金属工艺 | 4900篇 |
机械仪表 | 5250篇 |
建筑科学 | 5602篇 |
矿业工程 | 3180篇 |
能源动力 | 1944篇 |
轻工业 | 8097篇 |
水利工程 | 2497篇 |
石油天然气 | 2954篇 |
武器工业 | 1060篇 |
无线电 | 7988篇 |
一般工业技术 | 5975篇 |
冶金工业 | 2909篇 |
原子能技术 | 1331篇 |
自动化技术 | 10391篇 |
出版年
2024年 | 411篇 |
2023年 | 1225篇 |
2022年 | 2923篇 |
2021年 | 3683篇 |
2020年 | 2588篇 |
2019年 | 1967篇 |
2018年 | 2076篇 |
2017年 | 2452篇 |
2016年 | 2117篇 |
2015年 | 3377篇 |
2014年 | 4202篇 |
2013年 | 4979篇 |
2012年 | 5899篇 |
2011年 | 6113篇 |
2010年 | 5849篇 |
2009年 | 5563篇 |
2008年 | 5824篇 |
2007年 | 5766篇 |
2006年 | 4751篇 |
2005年 | 3788篇 |
2004年 | 2777篇 |
2003年 | 1984篇 |
2002年 | 1925篇 |
2001年 | 1654篇 |
2000年 | 1375篇 |
1999年 | 670篇 |
1998年 | 286篇 |
1997年 | 204篇 |
1996年 | 191篇 |
1995年 | 156篇 |
1994年 | 116篇 |
1993年 | 87篇 |
1992年 | 75篇 |
1991年 | 60篇 |
1990年 | 73篇 |
1989年 | 46篇 |
1988年 | 40篇 |
1987年 | 32篇 |
1986年 | 22篇 |
1985年 | 8篇 |
1984年 | 13篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 26篇 |
1980年 | 22篇 |
1979年 | 12篇 |
1976年 | 8篇 |
1965年 | 6篇 |
1959年 | 18篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
Yuanyuan Zhang Haiyan Lu Bing Wang Zhuo Zhang Xiaorong Lin Zhongzheng Chen Bin Li 《International Journal of Food Science & Technology》2015,50(6):1397-1404
Removal of imidacloprid and acetamiprid in tea infusions by microfiltration membrane using dead‐end model was investigated in the present study. The results showed that microfiltration significantly promoted the removal of both pesticides (P < 0.05) in tea infusions. Furthermore, the extent of removal was strongly influenced by the pore size of membrane, operational pressure and the concentrations of tea infusions. The initial concentration of imidacloprid and acetamiprid showed no significant effect on their removal rates. The maximum removal rates were 79.7% for imidacloprid and 81.9% acetamiprid. The changes in major chemical components of tea infusions after microfiltration were evaluated. The results indicated that microfiltration caused no considerable changes in total polyphenols and total free amino acids, and small but statistically significant losses (6.3–18.0%) of eight catechins and three methylxanthines when filtration volume reached to 200 mL. The present study validated the application of microfiltration as a potentially feasible and promising method for the removal of imidacloprid and acetamiprid residues from tea infusions. 相似文献
12.
通过对ADC行业当前现状的分析,包括产能、产业格局、工艺、市场、环保、运输等方面问题的阐述,提出了以联二脲取代ADC发泡剂为新的产业分界点的观点,通过产业转移和上下游的调整,发挥东西部各自的综合优势,促进ADC发泡剂产业的升级。 相似文献
13.
Yange Yang Xiangyang Zhou Bing Li Cunman Zhang 《International Journal of Hydrogen Energy》2021,46(5):4259-4282
Proton exchange membrane fuel cells (PEMFCs) have become the most attractive power supply units for stationary and mobile applications. The operation, design characteristics, as well as performance of PEMFCs, are closely related to the multiphase transport of mass, heat, and electricity in the cell, a critical of which is the gas diffusion layer (GDL). It is very important to guarantee the transmission of water and gasses under high current density, and which is the weakness of PEMFCs at present. Microporous layer (MPL) is considered to be the key variable for mass transfer, so varieties of works focus on modification of MPL materials and its structure design. However, there is still a lack of special review to summarize and prospect the progress of MPL in recent years. This review article therefore focuses on the insights and comprehensive understanding of four critical issues of the MPL, the porosity, pore size distribution, wettability, structural design and the durability of MPL. At last, the conclusion and recommendations section summarized the future prospects and recommendations for possible research opportunities. 相似文献
14.
Bing Yang Yu Zhou Wenjie Yu Song Zhang Hongxiang Chen Ju Ye 《Polymer International》2019,68(4):675-683
In order to improve the dispersity and stability of the nano‐SiO2 aqueous system with high solid content, a kind of polyacrylic acid dispersant with methoxysilicon end groups (KH590‐PAA) was synthesized by photopolymerization of acrylic acid (AA) initiated with (3‐mercaptopropyl)trimethoxysilane (KH590). After adding KH590‐PAA into the nano‐SiO2 aqueous dispersion system (20 wt% solid content), the viscosity and the curing time of the system were measured with a rotational viscometer and the inverted bottle method. Moreover, the dispersion mechanism of KH590‐PAA for the nano‐SiO2 aqueous system was researched by measuring the adsorption capacity, the particle size and the zeta potential of the nanoparticles with a conductivity meter, dynamic light scattering, SEM and TEM, respectively. The results showed that the methoxysilicon groups in KH590‐PAA could react with hydroxyl groups on the surface of nano‐SiO2 in the process of stirring, which enhanced the adsorption capacity of the dispersant and then increased the surface charge of the particles. Therefore, electrostatic repulsion and steric hindrance effects between the SiO2 nanoparticles could be further enhanced by adding the KH590‐PAA dispersant, and then the nano‐SiO2 aqueous system exhibited better dispersity and stability. Besides, the dispersion properties of SiO2 nanoparticles in water were closely related to the addition amount and the molecular weight of the KH590‐PAA dispersant. © 2018 Society of Chemical Industry 相似文献
15.
16.
The identification rate of UHF RFID system was restricted by multipath propagation effects.The system identification performance was studied considering the correlation coefficient between forward and reverse channels.Based on the generalized Rician fading channel model,the analytical expression of identification rate was derived under independent,full correlation and correlation cases.Compared with the existing analysis,the proposed uniform calculation formula of identification rate was for any correlation coefficient and kinds of channel conditions.The numerical computation and Monte-carlo simulations show that the influences of different correlation coefficients,channel conditions,sensitivity and distance on the identification rate. 相似文献
17.
18.
19.
20.
基于用户体验的产品包装设计探究 总被引:1,自引:0,他引:1
在经济繁荣发展的今天,人们对产品包装的需求已经不仅仅是功能上所完成的,用户与包装互动过程中综合感受才是重点。文章通过案例分析和研究,对现代产品包装设计中本能层次、行为层次、反思层次的体验设计进行分析。基于用户体验的产品包装设计,将使产品包装更为合理、人性化、获得更加愉悦的心情和美好回忆,同时促进销售且提升品牌文化及其附加价值。 相似文献