全文获取类型
收费全文 | 73220篇 |
免费 | 4195篇 |
国内免费 | 893篇 |
专业分类
电工技术 | 1767篇 |
技术理论 | 3篇 |
综合类 | 1229篇 |
化学工业 | 12842篇 |
金属工艺 | 2922篇 |
机械仪表 | 4030篇 |
建筑科学 | 2635篇 |
矿业工程 | 499篇 |
能源动力 | 2697篇 |
轻工业 | 5216篇 |
水利工程 | 538篇 |
石油天然气 | 1313篇 |
武器工业 | 110篇 |
无线电 | 12094篇 |
一般工业技术 | 13653篇 |
冶金工业 | 6836篇 |
原子能技术 | 817篇 |
自动化技术 | 9107篇 |
出版年
2023年 | 769篇 |
2022年 | 665篇 |
2021年 | 1911篇 |
2020年 | 1455篇 |
2019年 | 1458篇 |
2018年 | 1857篇 |
2017年 | 1826篇 |
2016年 | 2122篇 |
2015年 | 1928篇 |
2014年 | 2848篇 |
2013年 | 4447篇 |
2012年 | 4297篇 |
2011年 | 5112篇 |
2010年 | 4032篇 |
2009年 | 4246篇 |
2008年 | 3931篇 |
2007年 | 3427篇 |
2006年 | 3240篇 |
2005年 | 2812篇 |
2004年 | 2428篇 |
2003年 | 2254篇 |
2002年 | 2099篇 |
2001年 | 1638篇 |
2000年 | 1560篇 |
1999年 | 1557篇 |
1998年 | 2571篇 |
1997年 | 1798篇 |
1996年 | 1515篇 |
1995年 | 1302篇 |
1994年 | 966篇 |
1993年 | 884篇 |
1992年 | 640篇 |
1991年 | 585篇 |
1990年 | 520篇 |
1989年 | 516篇 |
1988年 | 388篇 |
1987年 | 312篇 |
1986年 | 281篇 |
1985年 | 252篇 |
1984年 | 215篇 |
1983年 | 161篇 |
1982年 | 168篇 |
1981年 | 137篇 |
1980年 | 142篇 |
1979年 | 104篇 |
1978年 | 97篇 |
1977年 | 122篇 |
1976年 | 167篇 |
1975年 | 78篇 |
1974年 | 74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.
Anisse Pereira Hong C. Lee Robert Lammert Jr. Cailyn Wolberg Jr. Danyi Ma Chad Immoos Federico Casassa Iksoon Kang 《International Journal of Food Science & Technology》2022,57(3):1814-1823
This study was conducted to evaluate the effect of red-wine grape pomaces on the quality and sensory attributes of beef hamburger patties. Both phenolic content and antioxidant activity were assessed using Syrah, Merlot and Cabernet Sauvignon pomaces. Following the assessment, hamburger patties were prepared with Merlot pomace at 0%, 2% and 4% for the patty quality and sensory attributes. Grape seeds possessed significantly higher phenolics and antioxidant activities over the seedless pomace (P < 0.05), whereas no significant difference was found for phenolics and antioxidant activities within the seeds and seedless pomaces. The patty pH decreased as the pomace was added for 2% and 4%. Colour values (L*, a* and b*) of patties lowered as the pomace was added. Allo-Kramer shear force and hardness values increased while cooking yield decreased (P < 0.05) with the addition of pomace. No significant difference between control and Merlot patties was found for flavour, juiciness and colour, whereas lower sensory attributes were observed for texture, taste and overall acceptability. It is observed that the addition of fermented red-wine grape pomace provides hamburger patties with health promoting factors such as antioxidant and other functional components, but it also provided darker, sourer and lower cooking yield. 相似文献
3.
4.
Jang Hye Ji Kim Jong Ha Lee Hyun-Sook Paik Hyun-Dong 《Food science and biotechnology》2022,31(6):731-737
Food Science and Biotechnology - The objective of this study was to develop a non-fermented probiotic milk that maintains its physicochemical properties, microbial properties, antioxidant activity,... 相似文献
5.
Lee Jusang Chung Minyoung Lee Minkyung Shin Yeong-Gil 《Multimedia Tools and Applications》2022,81(13):18327-18342
Multimedia Tools and Applications - Individual tooth segmentation and identification from cone-beam computed tomography images are preoperative prerequisites for orthodontic treatments. Instance... 相似文献
6.
7.
Magnetic Resonance Materials in Physics, Biology and Medicine - This study aims to compare an electrocardiogram (ECG)-gated four-dimensional (4D) phase-contrast (PC) magnetic resonance imaging... 相似文献
8.
9.
Qing Li Jun Wang Jie Ma Meng Ni Fan Yang Peng Liu Kuo Yang Lee Hsing-I Hsiang Deyuan Shen Dingyuan Tang 《Journal of the American Ceramic Society》2022,105(5):3375-3381
High-efficiency Yb:Y2O3 laser ceramics were fabricated using the vacuum-sintering plus hot isostatic pressing (HIP) without sintering additives. High-purity well-dispersed nanocrystalline Yb:Y2O3 powder was synthesized using a modified co-precipitation method in-house. The green bodies were first vacuum sintered at a temperature as low as 1430°C and then HIPed at 1450°C. Finally, the samples were air annealed at 800°C for 10 h. Although no sintering aids were used, full density of the samples with excellent optical homogeneity and an inline transmission of 80% at 400 nm could be obtained. Moreover, photodarkening phenomenon was not detected in the ceramics. Preliminary laser experiment with the fabricated ceramics in a two-mirror cavity has demonstrated 32 W continuous-wave (CW) output at ∼1077 nm with an optical-to-optical conversion efficiency of 58.2%. To the best of our knowledge, this is so far the highest CW output power and optical-to-optical conversion efficiency achieved with the Yb3+-doped sesquioxide ceramics in a simple two-mirror cavity. 相似文献
10.
Gui-Yang Luo Yi-Jing Gu Yuan Liu Zi-Liang Chen Yong-lin Huo Fu-Zhong Wu Yi Mai Xin-Yi Dai Yong Deng 《Ceramics International》2021,47(8):11332-11339
LiFePO4 modified by N-doped graphene (NG) with a three-dimensional conductive network structure was synthesized via a one-step in situ hydrothermal method. The effects of N amount of NG on the phase structure, morphology, and electrochemical properties of LiFePO4 are investigated in this study. X-ray diffraction (XRD) results show that doping suitable N amounts in NG do not alter the crystal structure of LiFePO4, and scanning electron microscopy (SEM) images show that NG can slightly reduce the particle size of LiFePO4. The high-resolution transmission electron microscopy (HRTEM) results show that the LiFePO4 particles are well covered and connected by NG. The electrochemical performance confirms that LiFePO4 modified by 20% N-doped graphene (named LFP/NG-4) displays a perfect specific capacity of 166.6 mAh·g?1 at a rate of 0.2C and can reach 125 mAh·g?1 at a rate of 5 C. Electrochemical impedance spectroscopy (EIS) results illustrate that the charge transfer resistance value of the LFP/NG-4 composite is only 58.6 Ω, which is very low compared with LiFePO4. Cyclic voltammetry (CV) tests indicate that the addition of 20% N-doped graphene can effectively reduce electrode polarization and improve reversibility. The LFP/NG-4 composite with a three-dimensional conductive network structure can be regarded as a promising cathode material for Li-ion batteries. 相似文献