全文获取类型
收费全文 | 393961篇 |
免费 | 4788篇 |
国内免费 | 1237篇 |
专业分类
电工技术 | 7171篇 |
综合类 | 2660篇 |
化学工业 | 54456篇 |
金属工艺 | 19640篇 |
机械仪表 | 16278篇 |
建筑科学 | 9196篇 |
矿业工程 | 2293篇 |
能源动力 | 8050篇 |
轻工业 | 26775篇 |
水利工程 | 4472篇 |
石油天然气 | 5488篇 |
武器工业 | 69篇 |
无线电 | 48321篇 |
一般工业技术 | 79866篇 |
冶金工业 | 54180篇 |
原子能技术 | 6554篇 |
自动化技术 | 54517篇 |
出版年
2021年 | 2115篇 |
2019年 | 2104篇 |
2018年 | 22559篇 |
2017年 | 22213篇 |
2016年 | 16009篇 |
2015年 | 3361篇 |
2014年 | 4461篇 |
2013年 | 11745篇 |
2012年 | 11395篇 |
2011年 | 23840篇 |
2010年 | 20625篇 |
2009年 | 18537篇 |
2008年 | 19889篇 |
2007年 | 22326篇 |
2006年 | 8171篇 |
2005年 | 11424篇 |
2004年 | 9597篇 |
2003年 | 9186篇 |
2002年 | 7499篇 |
2001年 | 6702篇 |
2000年 | 6520篇 |
1999年 | 6404篇 |
1998年 | 14369篇 |
1997年 | 10374篇 |
1996年 | 8233篇 |
1995年 | 6486篇 |
1994年 | 5801篇 |
1993年 | 5673篇 |
1992年 | 4612篇 |
1991年 | 4293篇 |
1990年 | 4093篇 |
1989年 | 3830篇 |
1988年 | 3678篇 |
1987年 | 3207篇 |
1986年 | 3101篇 |
1985年 | 3652篇 |
1984年 | 3425篇 |
1983年 | 3058篇 |
1982年 | 2872篇 |
1981年 | 2991篇 |
1980年 | 2778篇 |
1979年 | 2664篇 |
1978年 | 2530篇 |
1977年 | 2959篇 |
1976年 | 3576篇 |
1975年 | 2330篇 |
1974年 | 2325篇 |
1973年 | 2324篇 |
1972年 | 1853篇 |
1971年 | 1748篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
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
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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
42.
43.
44.
45.
46.
47.
48.
High-efficiency filtration in residential forced-air heating, ventilation, and air conditioning (HVAC) systems protects equipment and can reduce exposure to particulate matter. Laboratory tests provide a measure of the nominal efficiency, but they may not accurately reflect the in situ efficiency of the filters because of variations in system conditions and changes in filter performance over time. The primary focus of this paper is to evaluate the effective filtration efficiency, which is inclusive of any loading and system impacts, in 21 occupied residential homes through in-duct concentration measurements. We considered the role of filter media by testing both electret and non-electret media, as well as the role of loading by considering new and used filters. The results show that filters with higher nominal efficiency generally had higher effective filtration efficiency in the same home. In terms of performance change, there is no significant difference in efficiency between initial and 3-month non-electret filters, but the efficiency of electret filters generally decreased over time. However, both nominal efficiency and performance change were vastly overshadowed by the wide variety in loading and system conditions across homes, making it hard to predict filter efficiency in a given home without in situ measurements. 相似文献
49.
In this paper, we report on the indoor concentrations from a suite of full-scale outdoor tracer-gas point releases conducted in the downtown area of Oklahoma City in 2003. A point release experiment consisted of releases of sulfur hexafluoride (SF6) in multiple buildings and from different outdoor locations. From the measurements, we are able to estimate the concentration variations indoors for a building operating under “typical” operating conditions. The mean indoor spatial coefficients of variation are 30% to 45% from a daytime outdoor release are around 80% during an outdoor evening release. Having estimates of the spatial coefficient of variation provides stakeholders, including first responders, with the likely range of concentrations in the building when little is known about the building characteristics and operating behavior, such as developing urban-scale hazard and consequence analyses. We show differences in indoor measurements at different distances to the release points, floors of the building, and heating, ventilation, and air conditioning system (HVAC) operation. We also show estimates at different time resolutions. The statistics show that in the studied medium to large commercial buildings, spatial differences would result in peak indoor concentrations in certain parts of the buildings that may be substantially higher than the building average. To our knowledge, very few tracer gas measurements have been conducted in buildings of this scope, particularly with measurements on multiple floors and within a floor. The resulting estimates of spatial variability provide a unique opportunity for hazard assessment, and comparison to multi-zone models. 相似文献