全文获取类型
收费全文 | 60010篇 |
免费 | 6795篇 |
国内免费 | 3298篇 |
专业分类
电工技术 | 4668篇 |
技术理论 | 1篇 |
综合类 | 4580篇 |
化学工业 | 8712篇 |
金属工艺 | 3422篇 |
机械仪表 | 4345篇 |
建筑科学 | 4844篇 |
矿业工程 | 2133篇 |
能源动力 | 1772篇 |
轻工业 | 4812篇 |
水利工程 | 1346篇 |
石油天然气 | 2793篇 |
武器工业 | 652篇 |
无线电 | 7397篇 |
一般工业技术 | 6599篇 |
冶金工业 | 2286篇 |
原子能技术 | 758篇 |
自动化技术 | 8983篇 |
出版年
2024年 | 154篇 |
2023年 | 1158篇 |
2022年 | 2272篇 |
2021年 | 3153篇 |
2020年 | 2529篇 |
2019年 | 1973篇 |
2018年 | 2186篇 |
2017年 | 2387篇 |
2016年 | 2183篇 |
2015年 | 3392篇 |
2014年 | 3945篇 |
2013年 | 4390篇 |
2012年 | 4813篇 |
2011年 | 4904篇 |
2010年 | 4255篇 |
2009年 | 3883篇 |
2008年 | 3737篇 |
2007年 | 3408篇 |
2006年 | 3165篇 |
2005年 | 2581篇 |
2004年 | 1847篇 |
2003年 | 1253篇 |
2002年 | 1137篇 |
2001年 | 911篇 |
2000年 | 837篇 |
1999年 | 759篇 |
1998年 | 553篇 |
1997年 | 449篇 |
1996年 | 428篇 |
1995年 | 340篇 |
1994年 | 273篇 |
1993年 | 178篇 |
1992年 | 160篇 |
1991年 | 118篇 |
1990年 | 89篇 |
1989年 | 87篇 |
1988年 | 48篇 |
1987年 | 39篇 |
1986年 | 30篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 16篇 |
1980年 | 18篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1959年 | 7篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Journal of Porous Materials - In this work, a trifluoromethanesulfonic acid (TFOH) modified clay (TFOH-Clay) was developed for the removal of trace olefins in heavy naphtha. 5%TFOH-Clay can... 相似文献
2.
Zhai Shengnan Yu Kejing Meng Chaoran Wang Hongbo Fu Jiajia 《Journal of Materials Science》2022,57(15):7491-7502
Journal of Materials Science - In this paper, an eco-friendly method of producing hybrid silica aerogels by freeze-drying method (FD) is proposed. In the freeze-drying system, deionized water was... 相似文献
3.
4.
The carbon vacancy in high-entropy carbides (HECs) has a significant impact on their physical and chemical properties, yet relevant studies have still been relatively few. In this study, we investigate the surface energies of HECs with variable carbon vacancies through first-principles calculations. The results show that the surface energy of the (1 0 0) surface of the stoichiometric HECs is significantly lower than that of (1 1 1) surface. With the decrease in carbon stoichiometry, the surface energies of both (1 0 0) and (1 1 1) surfaces increase gradually, which is mainly due to the weakening of covalent bonding and the decrease of metal Hirshfeld-I (HI) charges. However, the surface energy of (1 0 0) surface increases more quickly than that of (1 1 1) surface and will exceed that of (1 1 1) surface when the carbon stoichiometry decreases to a certain extent, which is primarily attributed to the greater decrease rate of metal HI charges of (1 0 0) surface. 相似文献
6.
针对配电自动化终端优化布局问题,提出了一种基于重要度排序的终端优化布局方法。首先以等年值综合费用为目标函数,供电可靠性和投入产出比为双重约束建立了配电自动化终端优化布局模型。然后通过分析配电自动化终端对供电可靠性提升的影响,给出各个节点的“二遥”及“三遥”终端安装重要度定义及计算公式。最后采用枚举法确定最优终端安装数量,基于节点终端安装重要度排序确定终端的最优安装位置。该方法考虑了已布局节点对剩余节点终端安装重要度的影响,能够在降低计算量的同时兼顾布局合理性。运用所提方法RBTS-BUS2系统及扩充模型进行终端优化布局并与智能优化算法的布局结果进行对比,验证了本文方法的有效性及优越性。 相似文献
7.
Scientometrics - Examining the relationships among scientific disciplines is important today, but existing methods are limited by the contents and structure of their bibliographic databases. We... 相似文献
8.
Xiuyun Guo Junjun Wu Xiangren Meng Yawei Zhang Zengqi Peng 《International Journal of Food Science & Technology》2022,57(4):2556-2567
This study investigated the effects of l -lysine (Lys) and l -histidine (His) on the oxidative characteristics and gel properties of porcine myofibrillar proteins (MP). Results showed that Lys and His had a strong ferrous ion-chelating ability and hydroxyl radical-scavenging activity. Moreover, Lys and His inhibited the protein carbonyl formation and MP aggregation at 0.2 M and 0.6 M NaCl, respectively, in a dose-dependent manner. Furthermore, 2 and 4 mg mL−1 Lys and His decreased the oxidation-induced loss of the tertiary structure of MP accompanied by the lower surface hydrophobicity. The water-holding capacity and gel strength of MP gels increased with increasing Lys and His concentrations due to more regular and lamellar structures with smaller and homogeneous pores at 0.6 M NaCl and more orderly crosslinking via fibrous filament at 0.2 M NaCl. In summary, Lys and His chelated the ferrous ions and scavenged hydroxyl radicals, decreased the oxidation-induced physicochemical changes, thus preventing oxidative damage during the formation of a three-dimensional gel network, which resulted in better gel quality. 相似文献
9.
Zhenzhen Huang Xinxi Yang Qiqi Chen Leqi Chen Siyue Liang Qingzhu Zeng Ruifen Zhang Fei Huang Lihong Dong Dongxiao Su 《International Journal of Food Science & Technology》2022,57(5):3060-3068
This study aims to fabricate mineral-loading nanocarriers using natural materials. The interaction patterns between ovalbumin (OVA) and four water-soluble polyphenols, namely ferulic acid (FA), (-)-Epigallo-catechin 3-gallate (EGCG), gallic acid (GA) and epicatechin (EC), were investigated. Results showed that the optimised conditions for preparing stable OVA–polyphenol complexes are at the OVA–polyphenol ratio of 4:1 at pH 6, under which OVA–FA and OVA–EGCG showed the highest stability and mineral-loading capacity among four OVA–polyphenol complexes. The fluorescence results indicated that the addition of EGCG and FA induced a significant fluorescence quenching to OVA. The interaction between OVA and polyphenols involved hydrogen bonding, hydrophobic interaction and electrostatic interaction. Fourier transform infrared spectroscopy (FTIR) analysis suggested that both FA and EGCG enhanced the stability and orderliness of the structure of OVA. The transmission electron microscopy images also exhibited the spherical structure of OVA after the addition of FA and EGCG. Furthermore, scanning electron microscope–energy dispersive X-ray spectrum results suggested that OVA–FA and OVA–EGCG complexes were better mineral carriers than OVA–GA and OVA–EC. This study may serve as the theoretical support for the promising application of OVA in the fabrication of mineral-loading nanocarriers in functional food and pharmaceutic. 相似文献
10.
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