全文获取类型
收费全文 | 81876篇 |
免费 | 8075篇 |
国内免费 | 4127篇 |
专业分类
电工技术 | 5698篇 |
技术理论 | 8篇 |
综合类 | 5835篇 |
化学工业 | 12922篇 |
金属工艺 | 4797篇 |
机械仪表 | 5657篇 |
建筑科学 | 6105篇 |
矿业工程 | 2764篇 |
能源动力 | 2413篇 |
轻工业 | 5818篇 |
水利工程 | 1549篇 |
石油天然气 | 4352篇 |
武器工业 | 861篇 |
无线电 | 9856篇 |
一般工业技术 | 9517篇 |
冶金工业 | 3519篇 |
原子能技术 | 1076篇 |
自动化技术 | 11331篇 |
出版年
2024年 | 375篇 |
2023年 | 1431篇 |
2022年 | 2692篇 |
2021年 | 3782篇 |
2020年 | 2887篇 |
2019年 | 2270篇 |
2018年 | 2641篇 |
2017年 | 3018篇 |
2016年 | 2724篇 |
2015年 | 3918篇 |
2014年 | 4849篇 |
2013年 | 5577篇 |
2012年 | 6075篇 |
2011年 | 6424篇 |
2010年 | 5528篇 |
2009年 | 5087篇 |
2008年 | 4968篇 |
2007年 | 4644篇 |
2006年 | 4367篇 |
2005年 | 3642篇 |
2004年 | 2581篇 |
2003年 | 1996篇 |
2002年 | 1903篇 |
2001年 | 1623篇 |
2000年 | 1556篇 |
1999年 | 1445篇 |
1998年 | 1165篇 |
1997年 | 967篇 |
1996年 | 910篇 |
1995年 | 696篇 |
1994年 | 570篇 |
1993年 | 391篇 |
1992年 | 329篇 |
1991年 | 236篇 |
1990年 | 198篇 |
1989年 | 171篇 |
1988年 | 127篇 |
1987年 | 66篇 |
1986年 | 57篇 |
1985年 | 37篇 |
1984年 | 30篇 |
1983年 | 23篇 |
1982年 | 28篇 |
1981年 | 20篇 |
1980年 | 19篇 |
1979年 | 9篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1959年 | 6篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Multimedia Tools and Applications - In Wyner-Ziv (WZ) video coding, decoder side information (SI) takes a key role in a WZ video codec among other building blocks. In this paper, we review the... 相似文献
43.
44.
Longzhi Li Xiaowei Jiang Zhiguo Bian Jianwei Wang Fumao Wang Zhanlong Song 《Drying Technology》2019,37(2):173-185
Microwave lignite drying with assistance of biomass-derived char was addressed and effect of bio-char on drying rate and energy consumption was investigated in this work. Effective diffusion coefficient and activation energy for the drying process were also analyzed. The results indicated the drying process was largely dependent on the variation of sample temperature. Bio-char originated from pine wood was most favorable for lignite drying, considering its better promoting effect and advanced security. There existed an optimal bio-char addition ratio for drying process at different power. The corresponding optimal ratio was 10% at 231?W and 15% at 385?W, at which the biggest drying rate and the least energy consumption were reached. It was compared lignite drying initiated at 385?W was better for energy conservation. Effective diffusivity was improved and activation energy was simultaneously reduced, with the addition of bio-char. The minimum activation energy was 15.54?W?·?g?1, which was gained at bio-char addition ratio of 10%. The results revealed the effect of bio-char on depressing activation energy could rival that of metal-based additives. The drying process with assistance of microwave and bio-char could present technical and economical benefits on lignite upgrading. 相似文献
45.
Fei Xu Xiangli Shi Qingzhu Zhang Wenxing Wang 《International journal of molecular sciences》2015,16(8):18714-18731
The chlorothiophenoxy radicals (CTPRs) are key intermediate species in the formation of polychlorinated dibenzothiophenes/thianthrenes (PCDT/TAs). In this work, the formation of CTPRs from the complete series reactions of 19 chlorothiophenol (CTP) congeners with H and OH radicals were investigated theoretically by using the density functional theory (DFT) method. The profiles of the potential energy surface were constructed at the MPWB1K/6-311+G(3df,2p)//MPWB1K/6-31+G(d,p) level. The rate constants were evaluated by the canonical variational transition-state (CVT) theory with the small curvature tunneling (SCT) contribution at 600–1200 K. The present study indicates that the structural parameters, thermal data, and rate constants as well as the formation potential of CTPRs from CTPs are strongly dominated by the chlorine substitution at the ortho-position of CTPs. Comparison with the study of formation of chlorophenoxy radicals (CPRs) from chlorophenols (CPs) clearly shows that the thiophenoxyl-hydrogen abstraction from CTPs by H is more efficient than the phenoxyl-hydrogen abstraction from CPs by H, whereas the thiophenoxyl-hydrogen abstraction from CTPs by OH is less impactful than the phenoxyl-hydrogen abstraction from CPs by OH. Reactions of CTPs with H can occur more readily than that of CTPs with OH, which is opposite to the reactivity comparison of CPs with H and OH. 相似文献
46.
Shanquan Chen Sicong Wei Fei Jin Shanming Ke Xierong Zeng Lang Chen Chuanwei Huang 《Ceramics International》2018,44(12):13695-13698
From the perspectives of scientific researches and practical applications, it is desirable to explore high operating temperature ferromagnetic films. The effect of biaxial strain on magnetic properties of (110)-oriented La0.7Sr0.3MnO3 films was studied. High quality La0.7Sr0.3MnO3 films were grown on (110)-oriented perovskite single crystal substrates using pulsed laser deposition, varying substrate-induced misfit strains from ??2.27–0.75%. A remarkable enhancement of Curie temperature has been achieved for (110)-oriented La0.7Sr0.3MnO3 films clamped with small misfit strains (i.e., grown on LAST (110)). The enhanced Curie temperature of (110)-oriented La0.7Sr0.3MnO3 films could be attributed to the misfit strain between the films and the underlying substrates and may have technological implication for applications at high temperature environments. 相似文献
47.
Fei Li Xin-Gang Wang Xiao Huang Ji-Xuan Liu Weichao Bao Guo-Jun Zhang Hongzhi Wang 《Journal of the European Ceramic Society》2018,38(14):4806-4813
We present a straightforward method via sol-gel process using polyethylene glycol (PEG) as phase separation inducer to prepare zirconium carbide/silicon carbide (ZrC/SiC) porous monoliths. Organic/inorganic hybrid gels are prepared using zirconium oxychloride, furfuryl alcohol, and tetraethyl orthosilicate as major starting materials. In the presence of PEG, crack-free hybrid monoliths are obtained by drying the wet gels under ambient pressure, whereas in the absence of PEG, the wet gels break into pieces as expected. PEG plays a key role in maintaining the macroscopic shape of the monoliths. After ceramization at 1300–1500?°C, ZrC/SiC porous monoliths are obtained. SEM and mercury intrusion porosimetry data show that PEG also has strong influence on the microstructures of the monoliths. The compressive strengths of the ceramic monoliths are in the range of 0.3 to 0.7?MPa. And their compressive behavior starts to differ due to the changes in their microstructures, especially the pore structure. 相似文献
48.
49.
50.