全文获取类型
收费全文 | 115632篇 |
免费 | 10337篇 |
国内免费 | 7745篇 |
专业分类
电工技术 | 4646篇 |
技术理论 | 2篇 |
综合类 | 7296篇 |
化学工业 | 35133篇 |
金属工艺 | 10827篇 |
机械仪表 | 3613篇 |
建筑科学 | 2696篇 |
矿业工程 | 1947篇 |
能源动力 | 4919篇 |
轻工业 | 7554篇 |
水利工程 | 983篇 |
石油天然气 | 4649篇 |
武器工业 | 704篇 |
无线电 | 11759篇 |
一般工业技术 | 16639篇 |
冶金工业 | 5421篇 |
原子能技术 | 1532篇 |
自动化技术 | 13394篇 |
出版年
2024年 | 392篇 |
2023年 | 2077篇 |
2022年 | 3957篇 |
2021年 | 4424篇 |
2020年 | 3477篇 |
2019年 | 3292篇 |
2018年 | 2967篇 |
2017年 | 3705篇 |
2016年 | 4027篇 |
2015年 | 3923篇 |
2014年 | 5603篇 |
2013年 | 6447篇 |
2012年 | 7229篇 |
2011年 | 9116篇 |
2010年 | 7024篇 |
2009年 | 8165篇 |
2008年 | 7079篇 |
2007年 | 8067篇 |
2006年 | 7374篇 |
2005年 | 5794篇 |
2004年 | 4906篇 |
2003年 | 4397篇 |
2002年 | 3731篇 |
2001年 | 3052篇 |
2000年 | 2635篇 |
1999年 | 2055篇 |
1998年 | 1562篇 |
1997年 | 1248篇 |
1996年 | 1134篇 |
1995年 | 913篇 |
1994年 | 845篇 |
1993年 | 636篇 |
1992年 | 506篇 |
1991年 | 400篇 |
1990年 | 352篇 |
1989年 | 267篇 |
1988年 | 170篇 |
1987年 | 115篇 |
1986年 | 110篇 |
1985年 | 97篇 |
1984年 | 76篇 |
1983年 | 49篇 |
1982年 | 60篇 |
1981年 | 61篇 |
1980年 | 45篇 |
1979年 | 33篇 |
1978年 | 16篇 |
1977年 | 19篇 |
1975年 | 19篇 |
1951年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Effect of gums on viability and β‐galactosidase activity of Lactobacillus spp. in milk drink during refrigerated storage 下载免费PDF全文
Bernice D. Karlton‐Senaye Reza Tahergorabi Valerie L. Giddings Salam A. Ibrahim 《International Journal of Food Science & Technology》2015,50(1):32-40
The viability and β‐galactosidase activity of four Lactobacillus strains in milk drink containing gums during 28 days of refrigerated storage at 4 °C were assessed. The population of Lactobacillus rhamnosus GGB101 and Lactobacillus rhamnosus GGB103 were maintained, whereas the population of Lactobacillus reuteri DSM20016 and Lactobacillus reuteri SD2112 significantly decreased. The recommended level of 6 log CFU g?1 was exceeded for all tested trains throughout storage. The highest viable number of Lactobacillus rhamnosus GGB103 (8.76 ± 0.03 log CFU mL?1) was obtained in the product containing carrageenan–maltodextrin. The addition of guar–locust bean–carrageenan led to 20‐fold increase in the level of β‐galactosidase activity for L. rhamnosus GGB101 (1208 ± 2.12 Miller units mL?1) compared to the control (61 ± 2.83 Miller units mL?1). Our results suggested that gums could be added to milk to improve viability and enhance β‐galactosidase activity of Lactobacillus. 相似文献
3.
4.
5.
Akira Yamamoto Kentaro Teramura Saburo Hosokawa Tsunehiro Tanaka 《Science and Technology of Advanced Materials》2015,16(2)
The effect of SO2 gas was investigated on the activity of the photo-assisted selective catalytic reduction of nitrogen monoxide (NO) with ammonia (NH3) over a TiO2 photocatalyst in the presence of excess oxygen (photo-SCR). The introduction of SO2 (300 ppm) greatly decreased the activity of the photo-SCR at 373 K. The increment of the reaction temperature enhanced the resistance to SO2 gas, and at 553 K the conversion of NO was stable for at least 300 min of the reaction. X-ray diffraction, FTIR spectroscopy, thermogravimetry and differential thermal analysis, x-ray photoelectron spectroscopy (XPS), elemental analysis and N2 adsorption measurement revealed that the ammonium sulfate species were generated after the reaction. There was a strong negative correlation between the deposition amount of the ammonium sulfate species and the specific surface area. Based on the above relationship, we concluded that the deposition of the ammonium sulfate species decreased the specific surface area by plugging the pore structure of the catalyst, and the decrease of the specific surface area resulted in the deactivation of the catalyst. 相似文献
6.
通过制备不同晶相结构〔单斜相(m-ZrO_2)、四方相(t-ZrO_2)和无定型(a-ZrO_2)〕ZrO_2载体,再通过沉积沉淀法制得Cu/m-ZrO_2、Cu/t-ZrO_2和Cu/a-ZrO_2催化剂,分别用于催化二乙醇胺脱氢合成亚氨基二乙酸反应。采用XRD、氮气物理吸附脱附、XPS、H_2-TPR、CO_2-TPD对催化剂的结构进行了表征。结果表明,Cu/m-ZrO_2催化剂界面更加有利于Cu~+/Cu~0稳定存在,具有更多的碱性位点,且抗氧化性较好。在二乙醇胺脱氢反应中,Cu/m-ZrO_2催化剂性能最好,反应时间为2.5 h,亚氨基二乙酸收率为97.64%。 相似文献
7.
8.
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
9.
10.
介绍了一种基于高性能浮点DSP芯片TMS320C32、CPLD芯片XC95288和A/D采样芯片AD976组成的多路采集系统的工作原理以及设计方法。通过对第一路施加特殊的电压量,在CCS开发环境下读取采样缓冲区的值,并利用Matlab对采样数据进行了全波傅氏变换。此外,该系统已在继电保护中得到广泛应用,实践表明,该系统能较好地解决多路模拟量的采集,并确保了采样数据的安全可靠性。 相似文献