全文获取类型
收费全文 | 256672篇 |
免费 | 22763篇 |
国内免费 | 12443篇 |
专业分类
电工技术 | 16300篇 |
技术理论 | 18篇 |
综合类 | 18227篇 |
化学工业 | 41624篇 |
金属工艺 | 14871篇 |
机械仪表 | 16407篇 |
建筑科学 | 19388篇 |
矿业工程 | 7674篇 |
能源动力 | 7161篇 |
轻工业 | 18592篇 |
水利工程 | 4925篇 |
石油天然气 | 15166篇 |
武器工业 | 2087篇 |
无线电 | 30065篇 |
一般工业技术 | 29658篇 |
冶金工业 | 12686篇 |
原子能技术 | 2846篇 |
自动化技术 | 34183篇 |
出版年
2024年 | 1160篇 |
2023年 | 4315篇 |
2022年 | 8102篇 |
2021年 | 10936篇 |
2020年 | 8262篇 |
2019年 | 6625篇 |
2018年 | 7514篇 |
2017年 | 8434篇 |
2016年 | 7658篇 |
2015年 | 10389篇 |
2014年 | 13024篇 |
2013年 | 15887篇 |
2012年 | 17383篇 |
2011年 | 18522篇 |
2010年 | 16352篇 |
2009年 | 15536篇 |
2008年 | 15298篇 |
2007年 | 14468篇 |
2006年 | 14440篇 |
2005年 | 12320篇 |
2004年 | 8481篇 |
2003年 | 6923篇 |
2002年 | 6342篇 |
2001年 | 5630篇 |
2000年 | 5366篇 |
1999年 | 5859篇 |
1998年 | 4809篇 |
1997年 | 4105篇 |
1996年 | 3845篇 |
1995年 | 3115篇 |
1994年 | 2576篇 |
1993年 | 1824篇 |
1992年 | 1499篇 |
1991年 | 1102篇 |
1990年 | 807篇 |
1989年 | 696篇 |
1988年 | 546篇 |
1987年 | 382篇 |
1986年 | 303篇 |
1985年 | 190篇 |
1984年 | 178篇 |
1983年 | 122篇 |
1982年 | 129篇 |
1981年 | 97篇 |
1980年 | 85篇 |
1979年 | 41篇 |
1978年 | 29篇 |
1977年 | 32篇 |
1976年 | 34篇 |
1975年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
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
103.
104.
105.
在分析单一MU(Most Uncertainty)采样缺陷的基础上,提出一种"全局最优搜寻"方法 GOS(Global Optimal Search),并结合MU共同完成查询选择。GOS+MU方法中,GOS着眼全局寻找目标,在应用环境能提供的训练样本数量有限、分类器受训不充分时,该方法选择的对象学习价值高,能快速推进分类器学习进程;MU则能够在GOS采样失效情形下,利用分类器当前训练成果,选择查询不确定性最强的样本补充训练集。通过对网络商品的用户评论进行分类仿真,并比较其他采样学习方法的效果,证明了GOS+MU方法在压缩学习成本、提高训练效率方面的有效性。 相似文献
106.
Anxiang Su Gaoxing Ma Minhao Xie Yang Ji Xiangfei Li Liyan Zhao Qiuhui Hu 《International Journal of Food Science & Technology》2019,54(6):2277-2287
In this study, in vitro digestion and fermentation of Flammulina velutipes -derived polysaccharides (FVP) were investigated. It was found that FVP mainly consisted of 48.45% glucose, 15.40% mannose, 14.60% xylose, 11.80% fucose and 9.90% galactose. The -human saliva, simulated gastric and small intestinal juices conditions did not break down the FVP. Based on in vitro fermentation tests, FVP modulated the composition of gut microbiota by elevating the amounts of Bifidobacteriaceae and Bacteroidaceae and reducing the numbers of genera Lachnospiraceae and Enterococcaceae. Meanwhile, FVP affected the synthesis of short-chain fatty acids derived from gut microbiota. 相似文献
107.
Priyadarshi Chakraborty Yiming Tang Tomoya Yamamoto Yifei Yao Tom Guterman Shai Zilberzwige-Tal Nofar Adadi Wei Ji Tal Dvir Ayyalusamy Ramamoorthy Guanghong Wei Ehud Gazit 《Advanced materials (Deerfield Beach, Fla.)》2020,32(9):1906043
Self-assembled peptide hydrogels represent the realization of peptide nanotechnology into biomedical products. There is a continuous quest to identify the simplest building blocks and optimize their critical gelation concentration (CGC). Herein, a minimalistic, de novo dipeptide, Fmoc-Lys(Fmoc)-Asp, as an hydrogelator with the lowest CGC ever reported, almost fourfold lower as compared to that of a large hexadecapeptide previously described, is reported. The dipeptide self-assembles through an unusual and unprecedented two-step process as elucidated by solid-state NMR and molecular dynamics simulation. The hydrogel is cytocompatible and supports 2D/3D cell growth. Conductive composite gels composed of Fmoc-Lys(Fmoc)-Asp and a conductive polymer exhibit excellent DNA binding. Fmoc-Lys(Fmoc)-Asp exhibits the lowest CGC and highest mechanical properties when compared to a library of dipeptide analogues, thus validating the uniqueness of the molecular design which confers useful properties for various potential applications. 相似文献
108.
109.
110.