全文获取类型
收费全文 | 26391篇 |
免费 | 1717篇 |
国内免费 | 71篇 |
专业分类
电工技术 | 384篇 |
综合类 | 38篇 |
化学工业 | 5960篇 |
金属工艺 | 1065篇 |
机械仪表 | 1628篇 |
建筑科学 | 530篇 |
矿业工程 | 8篇 |
能源动力 | 1047篇 |
轻工业 | 2299篇 |
水利工程 | 102篇 |
石油天然气 | 16篇 |
无线电 | 4512篇 |
一般工业技术 | 5709篇 |
冶金工业 | 1699篇 |
原子能技术 | 372篇 |
自动化技术 | 2810篇 |
出版年
2024年 | 32篇 |
2023年 | 341篇 |
2022年 | 506篇 |
2021年 | 862篇 |
2020年 | 608篇 |
2019年 | 637篇 |
2018年 | 871篇 |
2017年 | 832篇 |
2016年 | 971篇 |
2015年 | 783篇 |
2014年 | 1184篇 |
2013年 | 1710篇 |
2012年 | 1803篇 |
2011年 | 2189篇 |
2010年 | 1616篇 |
2009年 | 1658篇 |
2008年 | 1458篇 |
2007年 | 1116篇 |
2006年 | 1004篇 |
2005年 | 859篇 |
2004年 | 788篇 |
2003年 | 714篇 |
2002年 | 707篇 |
2001年 | 587篇 |
2000年 | 508篇 |
1999年 | 489篇 |
1998年 | 778篇 |
1997年 | 482篇 |
1996年 | 444篇 |
1995年 | 299篇 |
1994年 | 193篇 |
1993年 | 163篇 |
1992年 | 132篇 |
1991年 | 110篇 |
1990年 | 89篇 |
1989年 | 98篇 |
1988年 | 81篇 |
1987年 | 70篇 |
1986年 | 55篇 |
1985年 | 49篇 |
1984年 | 39篇 |
1983年 | 29篇 |
1982年 | 31篇 |
1981年 | 28篇 |
1980年 | 32篇 |
1979年 | 14篇 |
1977年 | 22篇 |
1976年 | 35篇 |
1975年 | 19篇 |
1974年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Hong Sae Jin Park Nam Il Hwang Dae Keun Yi Tae Gyu Eum Hyang Lan 《Food science and biotechnology》2022,31(6):669-679
Food Science and Biotechnology - Various hilling materials (rice hulls, pine sawdust, and perlite) were compared to produce sprout vegetables using beach silvertop (Glehnia littoralis Fr. Schm. ex... 相似文献
2.
International Journal of Information Security - Machine learning techniques have been widely used and shown remarkable performance in various fields. Along with the widespread utilization of... 相似文献
3.
Qianying Hoo Xiaohu Wang Feng Yuan Xuewei Cao Tiewa Cao Maolin Zhang 《Journal of the European Ceramic Society》2021,41(6):3816-3822
Jingdezhen is famous for its bluish white (Qingbai) porcelains of the Song Dynasty, and those decorated with iron spots are distinctive among them. Herein, iron spots on a bluish white porcelain were investigated using a series of microscopic and spectroscopic characterizations. We found the decreasing iron content from more than 8 wt% to about 2 wt% during the glaze color transition from rusty to brown and finally into green, which built a connection on the coloring mechanism of iron-rich crystallized glaze and celadon glaze. We identified the rare ε-Fe2O3, a promising magnetic material, in both the dark brown crystals and the triangular crystals in the rusty area, which is its first discovery among bluish white porcelains. Based on these findings, we discussed the coloring mechanism of iron-spot decoration along with the physical form of the iron oxide crystals, indicating the partially reducing atmosphere during firing process. 相似文献
4.
5.
6.
Food Science and Biotechnology - Aluminum based reflective nanolens arrays were developed via a series of aluminum electropolishing and anodization steps with subsequent selective dissolution of... 相似文献
7.
8.
Eui Dae Jung Amit Kumar Harit Do Hui Kim Chung Hyeon Jang Jong Hyun Park Shinuk Cho Myoung Hoon Song Han Young Woo 《Advanced materials (Deerfield Beach, Fla.)》2020,32(30):2002333
A series of anionic conjugated polyelectrolytes (CPEs) is synthesized based on poly(fluorene-co-phenylene) by varying the side-chain ionic density from two to six per repeat units (MPS2-TMA, MPS4-TMA, and MPS6-TMA). The effect of MPS2, 4, 6-TMA as interlayers on top of a hole-extraction layer of poly(bis(4-phenyl)-2,4,6-trimethylphenylamine (PTAA) is investigated in inverted perovskite solar cells (PeSCs). Owing to the improved wettability of perovskites on hydrophobic PTAA with the CPEs, the PeSCs with CPE interlayers demonstrate a significantly enhanced device performance, with negligible device-to-device dependence relative to the reference PeSC without CPEs. By increasing the ionic density in the MPS-TMA interlayers, the wetting, interfacial defect passivation, and crystal growth of the perovskites are significantly improved without increasing the series resistance of the PeSCs. In particular, the open-circuit voltage increases from 1.06 V for the PeSC with MPS2-TMA to 1.11 V for the PeSC with MPS6-TMA. The trap densities of the PeSCs with MPS2,4,6-TMA are further analyzed using frequency-dependent capacitance measurements. Finally, a large-area (1 cm2) PeSC is successfully fabricated with MPS6-TMA, showing a power conversion efficiency of 18.38% with negligible hysteresis and a stable power output under light soaking for 60 s. 相似文献
9.
10.
Jeongchan Lee Dr. Joonwon Kim Hyun Kim Eun-Jung Kim Prof. Dr. Hee-Jin Jeong Prof. Dr. Kwon-Young Choi Prof. Dr. Byung-Gee Kim 《Chembiochem : a European journal of chemical biology》2020,21(10):1446-1452
Tryptophan halogenases are found in diverse organisms and catalyze regiospecific halogenation. They play an important role in the biosynthesis of halogenated indole alkaloids, which are biologically active and of therapeutic importance. Here, a tryptophan 6-halogenase (SatH) from Streptomyces albus was characterized by using a whole-cell reaction system in Escherichia coli. SatH showed substrate specificity for chloride and bromide ions, leading to regiospecific halogenation at the C6-position of l -tryptophan. In addition, SatH exhibited higher performance in bromination than that of previously reported tryptophan halogenases in the whole-cell reaction system. Through structure-based protein mutagenesis, it has been revealed that two consecutive residues, A78/V79 in SatH and G77/I78 in PyrH, are key determinants in the regioselectivity difference between tryptophan 6- and 5-halogenases. Substituting the AV with GI residues switched the regioselectivity of SatH by moving the orientation of tryptophan. These data contribute to an understanding of the key residues that determine the regioselectivity of tryptophan halogenases. 相似文献