全文获取类型
收费全文 | 6447篇 |
免费 | 365篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 53篇 |
综合类 | 13篇 |
化学工业 | 1662篇 |
金属工艺 | 193篇 |
机械仪表 | 145篇 |
建筑科学 | 264篇 |
矿业工程 | 13篇 |
能源动力 | 250篇 |
轻工业 | 917篇 |
水利工程 | 44篇 |
石油天然气 | 35篇 |
武器工业 | 2篇 |
无线电 | 360篇 |
一般工业技术 | 1085篇 |
冶金工业 | 687篇 |
原子能技术 | 69篇 |
自动化技术 | 1029篇 |
出版年
2024年 | 11篇 |
2023年 | 55篇 |
2022年 | 121篇 |
2021年 | 227篇 |
2020年 | 147篇 |
2019年 | 157篇 |
2018年 | 238篇 |
2017年 | 233篇 |
2016年 | 252篇 |
2015年 | 193篇 |
2014年 | 267篇 |
2013年 | 463篇 |
2012年 | 401篇 |
2011年 | 505篇 |
2010年 | 364篇 |
2009年 | 341篇 |
2008年 | 331篇 |
2007年 | 240篇 |
2006年 | 245篇 |
2005年 | 210篇 |
2004年 | 153篇 |
2003年 | 164篇 |
2002年 | 150篇 |
2001年 | 90篇 |
2000年 | 84篇 |
1999年 | 64篇 |
1998年 | 195篇 |
1997年 | 152篇 |
1996年 | 93篇 |
1995年 | 70篇 |
1994年 | 64篇 |
1993年 | 68篇 |
1992年 | 28篇 |
1991年 | 24篇 |
1990年 | 24篇 |
1989年 | 25篇 |
1988年 | 22篇 |
1987年 | 25篇 |
1986年 | 20篇 |
1985年 | 29篇 |
1984年 | 18篇 |
1983年 | 20篇 |
1982年 | 19篇 |
1981年 | 25篇 |
1980年 | 18篇 |
1979年 | 23篇 |
1978年 | 16篇 |
1977年 | 14篇 |
1976年 | 34篇 |
1971年 | 11篇 |
排序方式: 共有6821条查询结果,搜索用时 687 毫秒
961.
Utilization and partition of dietary nitrogen in dairy cows fed grass silage-based diets 总被引:2,自引:0,他引:2
Data from 207 production trials (998 treatment means) were used to study the effects of animal and dietary characteristics on the efficiency of N utilization for milk protein production, and on fecal N, urinary N, and total manure N output. The average efficiency of transferring dietary N to milk N (MNE; milk N/N intake) was 277 (SD = 36.0) g/kg. Nitrogen efficiency was poorly related to milk yield. Dietary concentrations of crude protein (CP) and protein balance in the rumen (PBV) were the best single predictors of MNE. Dietary CP concentration explained variation in MNE better than did N intake. Bivariate models with PBV or metabolizable protein (MP) explained the variation better than CP alone. The effects of protein feeding parameters on MNE were consistent among data subsets from studies investigating the effects of the amount and protein concentration of concentrate supplement, silage digestibility, silage fermentation quality, or substitution of grass silage with legume silage. The model with total dry matter and N intakes as independent variables explained fecal, urinary, and total manure N output more precisely than N intake alone. The model of fecal N output suggested that the true digestibility of dietary N was 0.91, and that metabolic and endogenous N was the major component in fecal N. The proportion of urine N in manure N was strongly related to dietary CP concentration. Including the concentration of dietary carbohydrates only slightly improved the models, indicating that the most effective strategy to improve MNE and to decrease N losses in manure, especially in urine, is to avoid feeding diets with excessively high CP concentration and especially excess ruminally degradable CP. 相似文献
962.
963.
964.
965.
Adam H. Metherel William S. Harris Liu Ge Robert A. Gibson Raphaël Chouinard-Watkins Richard P. Bazinet Lei Liu J. Thomas Brenna Juan J. Aristizabal-Henao Ken D. Stark Robert C. Block 《Lipids》2019,54(11-12):755-761
Dried blood spots for fatty acid profiling are increasing in popularity; however, variability in results between laboratories has not been characterized. Whole blood from two subjects (low and high n-3 polyunsaturated fatty acid [PUFA] status) was collected, 25 μL applied to butylated hydroxytoluene (BHT)-treated chromatography strips, dried in air, and shipped to five laboratories. Results were reported as “routine” (typical fatty acids for each laboratory) or “standardized” (a set of 19 fatty acids), and outliers and variability (%CV) were determined. Five and eight outliers of a possible 91 measures each were identified by routine and standardized reporting, respectively, including eicosapentaenoic acid (EPA, 20:5n-3) in the low n-3 PUFA sample and arachidonic acid in the high n-3 PUFA sample. By standardized reporting, no outliers were identified for EPA or docosahexaenoic acid (DHA, 22:6n-3), and %CV decreased from 8.6% to 6.0% and 9.1% to 6.6% for EPA and 10.5% to 7.2% and 10.5% to 6.6% for DHA in the low and high n-3 PUFA sample, respectively. In conclusion, fatty acid profiles yielded few outliers, and standardization of reporting reduced the variability between laboratories. 相似文献
966.
Katlijn R. N. Moelants Paul R. Smith Tristan E. Lipkie Adam J. Steinbach Gerardo Leyva Fenja C. H. Süverkrüp Joël R. Wallecan 《Journal of the American Oil Chemists' Society》2019,96(8):865-876
Structuring of fatty products is important in producing palatable food products. Saturated fat (SAFA) crystals are needed to bring structure to many products (such as bakery or confectionery). In a product control of the structure by fat nucleation and crystallization, it is important to deliver the correct performance. Many techniques only work on quiescent systems and give limited information about the sheared systems that are generally found in industrial production of products. This article presents a novel rheological technique that can be used to probe crystallization and network structure under sheared conditions. The results show that crystallization of palm oil can be divided into different key stages. These result from initial nucleation, structuring by the crystals, polymorphic transformation, further structure building, and then subsequent relaxation. Significant postcrystallization (sintering) events occur over at least a day. It is seen that the shear rate leads to possibilities for crystallization control. Higher shear gives a reduction in network strength (as measured by G′) of the initial crystal network. However, after longer posthardening, results are very similar. This work enables the development of a fast tool that can be used to monitor structure formation in fats and reveals the relative importance of the nucleation–crystallization and postcrystallization events in sheared systems. 相似文献
967.
Jos Agustín Tapia‐Hernndez Carmen Lizette Del‐Toro‐Snchez Francisco Javier Cinco‐Moroyoqui Saúl Ruiz‐Cruz Josu Jurez Daniela Denisse Castro‐Enríquez Carlos Gregorio Barreras‐Urbina Guadalupe Amanda Lpez‐Ahumada Francisco Rodríguez‐Flix 《Journal of food science》2019,84(4):818-831
Currently, electrospraying is a novel process for obtaining the nanoparticles from biopolymers. Zein nanoparticles have been obtained by this method and used to protect both hydrophilic and hydrophobic antioxidant molecules from environmental factors. The objective of this work was to prepare and characterize gallic acid‐loaded zein nanoparticles obtained by the electrospraying process to provide protection to gallic acid from environmental factors. Thus, it was related to the concentration of gallic acid in physicochemical and rheological properties of the electrosprayed solution, and also to equipment parameters, such as voltage, flow rate, and distance of the collector in morphology, and particle size. The physicochemical properties showed a relationship in the formation of a Taylor cone, in which at a low concentration of gallic acid (1% w/v), low viscosity (0.00464 ± 0.00001 Pa·s), and density (0.886 ± 0.00002 g/cm3), as well as high electrical conductivity (369 ± 4.3 µs/cm), forms a stable cone‐jet mode. The rheological properties and the Power Law model of the gallic acid‐zein electrosprayed solution demonstrated Newtonian behavior (n = 1). The morphology and size of the particle were dependent on the concentration of gallic acid. Electrosprayed parameters with high voltage (15 kV), low flow rate (0.1 mL/hr), and short distance (10 cm) exhibited a smaller diameter and spherical morphology. FT–IR showed interaction in the gallic acid‐loaded zein nanoparticle by hydrogen bonds. Therefore, the electrospraying process is a feasible technique for obtaining gallic acid‐loaded zein nanoparticles and providing potential protection to gallic acid from environmental factors. 相似文献
968.
Francisco Rodríguez‐Flix Carmen Lizette Del‐Toro‐Snchez Francisco Javier Cinco‐Moroyoqui Josu Jurez Saúl Ruiz‐Cruz Guadalupe Amanda Lpez‐Ahumada Elizabeth Carvajal‐Millan Daniela Denisse Castro‐Enríquez Carlos Gregorio Barreras‐Urbina Jos Agustín Tapia‐Hernndez 《Journal of food science》2019,84(10):2883-2897
969.