全文获取类型
收费全文 | 81272篇 |
免费 | 6791篇 |
国内免费 | 3095篇 |
专业分类
电工技术 | 4208篇 |
技术理论 | 4篇 |
综合类 | 4333篇 |
化学工业 | 14489篇 |
金属工艺 | 4264篇 |
机械仪表 | 5343篇 |
建筑科学 | 4938篇 |
矿业工程 | 1297篇 |
能源动力 | 2613篇 |
轻工业 | 6151篇 |
水利工程 | 1275篇 |
石油天然气 | 2610篇 |
武器工业 | 484篇 |
无线电 | 11257篇 |
一般工业技术 | 12408篇 |
冶金工业 | 3886篇 |
原子能技术 | 1063篇 |
自动化技术 | 10535篇 |
出版年
2024年 | 185篇 |
2023年 | 1077篇 |
2022年 | 1748篇 |
2021年 | 2987篇 |
2020年 | 2150篇 |
2019年 | 2006篇 |
2018年 | 2249篇 |
2017年 | 2425篇 |
2016年 | 2567篇 |
2015年 | 3060篇 |
2014年 | 3902篇 |
2013年 | 5017篇 |
2012年 | 5411篇 |
2011年 | 6115篇 |
2010年 | 5214篇 |
2009年 | 4890篇 |
2008年 | 4812篇 |
2007年 | 4278篇 |
2006年 | 4120篇 |
2005年 | 3564篇 |
2004年 | 2777篇 |
2003年 | 2631篇 |
2002年 | 2897篇 |
2001年 | 2426篇 |
2000年 | 1964篇 |
1999年 | 1765篇 |
1998年 | 1770篇 |
1997年 | 1320篇 |
1996年 | 1212篇 |
1995年 | 962篇 |
1994年 | 757篇 |
1993年 | 597篇 |
1992年 | 443篇 |
1991年 | 362篇 |
1990年 | 278篇 |
1989年 | 246篇 |
1988年 | 208篇 |
1987年 | 142篇 |
1986年 | 110篇 |
1985年 | 88篇 |
1984年 | 68篇 |
1983年 | 46篇 |
1982年 | 54篇 |
1981年 | 46篇 |
1980年 | 45篇 |
1979年 | 20篇 |
1977年 | 22篇 |
1976年 | 42篇 |
1975年 | 24篇 |
1974年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Properties and applications of β‐glycosidase from Bacteroides thetaiotaomicron that specifically hydrolyses isoflavone glycosides 下载免费PDF全文
Da‐Hye Byun Hye‐Jeong Choi Hye‐Won Lee Hye‐Yeon Jeon Woo‐Jae Choung Jae‐Hoon Shim 《International Journal of Food Science & Technology》2015,50(6):1405-1412
To modify the glycan part of glycosides, the gene encoding β‐glycosidase was cloned from Bacteroides thetaiotaomicron VPI‐5482. The cloned gene, bt_1780, was expressed in Escherichia coli MC1061 and the expressed enzyme was purified using Ni‐NTA affinity chromatography. The purified enzyme, BTBG, showed optimal activity at 50 °C and pH 5.5. Interestingly, this enzyme did not have any hydrolysing activity on ordinary β‐linkage–containing substrates such as xylobiose, lactose and cello‐oligosaccharide, but specifically hydrolysed isoflavone glycosides such as daidzin, genistin and glycitin. Compared to a commercial beta glucosidase, BTBG selectively hydrolysed isoflavone glycosides in soybean extract mixture solution. These results suggest that BTBG may be a specialized enzyme for the hydrolysis of glycosides and that the substrate specificity of BTBG is applicable for the bioconversion of isoflavone glycosides in the food industry. 相似文献
52.
This paper discusses the compressive performance of perforated brick masonry after fire exposure. Compressive strength tests of the mortar, clay perforated brick, and perforated brick masonry specimens were performed in accordance with ISO834 fire tests of different durations. The temperature distribution of the masonry materials and specimens was simulated using the finite element software ABAQUS, with the thermal parameters of masonry materials recommended by European standard Eurocode 6 and related literature. The compressive strength reduction factors of mortar and clay perforated brick exposed to different fire durations were calculated via the layered method suggested by European standard Eurocode 1. In addition, the compressive strength reduction factors after cooldown were obtained from the experimental data of the masonry materials, and by considering further reductions in the compressive strength after cooling from high temperatures. Experimental data of the masonry specimens were compared with the numerical results obtained using the reduction factors proposed in this work. The comparison revealed an overall acceptable approximation. Thus, the method presented in this paper can be used to evaluate the residual capacity of masonry structures after fire. 相似文献
53.
Journal of Computer Science and Technology - New non-volatile memory (NVM) technologies are expected to replace main memory DRAM (dynamic random access memory) in the near future. NAND flash... 相似文献
54.
Hwang Seongil Park Sang Hyun Jin Maolin Kang Sang Hoon 《Intelligent Service Robotics》2021,14(3):471-484
Intelligent Service Robotics - A robust control designed for multiple degrees-of-freedom (DOF) robot manipulators performing complex tasks requiring frequent physical interaction with unknown... 相似文献
55.
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
56.
Jin Huandong 《中国油气》2018,(2)
This paper analyzes the status quo and progress of overseas oil and gas business cooperation built by Chinese oil enterprises in 2017. With the slow recovery of the oil and gas industries as a whole, the overseas oil and gas business of Chinese oil enterprises has continued to grow in size, and all-round cooperation progress was made along the Belt and Road. Breakthroughs were made in oil and gas cooperation between China and the United States. In the meantime, new features have emerged in the overseas cooperation of Chinese enterprises, and a pattern of diversified investors has basically taken shape. 相似文献
57.
Li Lei Limin Li Shasha Wang Gaoyang Zhao Yoshifumi Oshima Yang Ren Lei Zhao Lihua Jin Yao Wang Chengshan Li Pingxiang Zhang 《Journal of the European Ceramic Society》2018,38(14):4694-4700
Highly (100)-oriented Ce1-x(Y0.2Zr0.8)xOδ (CYZO) films were prepared on biaxially textured NiW substrates by a chemical solution deposition approach using metal inorganic salts as starting materials. It has been found that both the preferential orientation and surface roughness of CYZO films decrease gradually with increasing of the doping percentage of Y3+ and Zr4+ ions. The epitaxial growth relationship of (220)CYZO//(200)NiW and [00?l]CYZO//[001]NiW was demonstrated by XRD texture measurement as well as atomic resolution STEM observation. XRD, Raman and XPS spectra results indicate that Y3+ and Zr4+ ions were indeed introduced into CeO2 lattice to substitute Ce4+ ions and form cubic fluorite CYZO solid solution. Moreover, CeO2 buffer layer can be endowed a strong enough capability to prevent element diffusion through co-doping of yttrium and zirconium, provided that an optimal doping ratio of them is adopted. This will provide a new approach to fabricating strong-barrier single buffer layer for coated conductor. 相似文献
58.
59.
60.