全文获取类型
收费全文 | 7369篇 |
免费 | 380篇 |
国内免费 | 24篇 |
专业分类
电工技术 | 3篇 |
综合类 | 108篇 |
化学工业 | 350篇 |
金属工艺 | 5篇 |
机械仪表 | 57篇 |
建筑科学 | 22篇 |
矿业工程 | 9篇 |
能源动力 | 7篇 |
轻工业 | 7031篇 |
石油天然气 | 61篇 |
无线电 | 16篇 |
一般工业技术 | 66篇 |
冶金工业 | 14篇 |
原子能技术 | 3篇 |
自动化技术 | 21篇 |
出版年
2024年 | 38篇 |
2023年 | 199篇 |
2022年 | 309篇 |
2021年 | 427篇 |
2020年 | 194篇 |
2019年 | 415篇 |
2018年 | 381篇 |
2017年 | 392篇 |
2016年 | 181篇 |
2015年 | 183篇 |
2014年 | 412篇 |
2013年 | 414篇 |
2012年 | 354篇 |
2011年 | 452篇 |
2010年 | 363篇 |
2009年 | 332篇 |
2008年 | 310篇 |
2007年 | 433篇 |
2006年 | 356篇 |
2005年 | 327篇 |
2004年 | 269篇 |
2003年 | 243篇 |
2002年 | 206篇 |
2001年 | 86篇 |
2000年 | 77篇 |
1999年 | 82篇 |
1998年 | 73篇 |
1997年 | 45篇 |
1996年 | 42篇 |
1995年 | 36篇 |
1994年 | 31篇 |
1993年 | 26篇 |
1992年 | 35篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1980年 | 7篇 |
1972年 | 1篇 |
排序方式: 共有7773条查询结果,搜索用时 13 毫秒
111.
离子色谱法检测硝酸盐亚硝酸盐前处理方法的研究 总被引:1,自引:0,他引:1
目的 利用离子色谱法检测乳及乳制品中亚硝酸盐、硝酸盐,在实际检测中用该国标方法在前处理样品时,存在沉淀样品不完全进而影响检测准确性、重复性不理想的弊端,为提高检测的准确性,缩小检测偏差,需对国标方法中样品的前处理改进。方法 样品经乙腈沉淀脂肪蛋白质后,采用相应的方法提取和净化,以氢氧化钾溶液为淋洗液,阴离子交换柱分离,电导检测器检测。以保留时间定性,外标法定量。结果 该方法克服了乳及乳制品GB5009.33-2010第三法检测检出限高及检测用时长,精密度低的的弊端。结论本方法适合于乳及乳制品定量测定。 相似文献
112.
113.
Marilù Decimo Stefano Morandi Tiziana Silvetti Milena Brasca 《Journal of food science》2014,79(10):M2081-M2090
Eighty psychrotrophic bacterial strains, isolated from different northwest Italian bulk tank milks destined for Grana Padano cheese production, were identified by 16S rRNA gene amplification and partial sequence analysis of the rpoB gene. Pseudomonas spp. were the most commonly occurring contaminants, P. fluorescens being the predominant isolated species, along with Enterobacteriaceae, primarily Serratia marcescens. RAPD‐PCR was used to study genetic variability and distinguish closely related strains; a high degree of genetic heterogeneity among the strains was highlighted. All the strains were characterized for their ability to produce proteases, lipases and lecithinases at different temperatures (7, 22, and 30 °C). Forty‐one of the psychrotrophic strains were positive for all the enzymatic activities. The highest number of positive strains for all the incubation temperatures was found for lipolytic activity (59), followed by proteolytic (31) and lecithinase (28) activities, and the enzymatic traits varied among the Pseudomonas and Enterobacteriaceae strains. The proteolytic psychrotrophic strains were screened for the presence of the aprX gene, coding for a heat‐resistant metalloprotease in Pseudomonas spp. The aprX gene was detected in 19 of 63 Pseudomonas strains, and was widespread in the P. fluorescens strains (14/19). 相似文献
114.
利用酒精试验对羊乳的酒精稳定性进行了研究,研究结果表明:在pH6.4~7.2时,羊乳酒精稳定性随羊乳pH的升高而增强,羊乳(pH=6.70)中添加44%浓度的等量酒精出现絮状沉淀物,而牛乳通常是添加70%浓度的酒精出珑沉淀;在30~80℃时,羊乳酒精稳定性随着温度的升高而降低;羊乳酒精稳定性随着羊乳中游离Ca2+浓度增大而降低. 相似文献
115.
116.
前表面荧光法在牛奶美拉德反应检测中的应用 总被引:1,自引:0,他引:1
在热处理中,牛奶中的乳蛋白容易与乳糖发生美拉德反应,使牛奶的色泽、风味、营养等发生变化。与传统化学检测法相比,前表面荧光法具有快速灵敏、前处理简便等优点。为了评估前表面荧光法在检测牛奶美拉德反应程度上的准确性和适用性,本文对比了不同热处理下牛奶的美拉德反应的荧光图谱和美拉德产物的含量,分析了指标间的相关性。并以前表面荧光法和羟甲基糠醛含量建立模型对商业乳品进行预测,结果良好,为荧光检测的工业应用提供理论依据。结果显示,前表面荧光法可应用于牛奶前中期美拉德产物的无损检测。 相似文献
117.
118.
Concentrations of retinol, α-tocopherol, and major carotenoids in dairy products are often determined simultaneously by liquid chromatography. These compounds have different polarity and solubility; thus, extracting them simultaneously can be difficult and inefficient. In milks with low carotenoid concentrations, the xanthophylls lutein and zeaxanthin may not be completely resolved using common extraction techniques. A simplified method was developed to optimize extraction efficiency and the limit of detection and limit of quantification (LoQ) of lutein and zeaxanthin in bovine milk without decreasing sensitivity to other vitamins or carotenoids. The developed method evaluates lutein, zeaxanthin, β-carotene, retinol, and α-tocopherol simultaneously by ultra-high performance liquid chromatography–photodiode array detection. Common saponification temperatures (40–60°C) and concentrations of KOH in water (10–50% KOH wt/vol) were evaluated. Multiple solvents were evaluated for optimal xanthophyll extraction (diethyl ether, dichloromethane, hexane, and tetrahydrofuran) following saponification. The limit of detection and LoQ were defined as 3:1 and 10:1 signal-to-noise ratio, respectively. All experiments were performed in triplicate. The optimal saponification procedure was a concentration of 25% KOH at either 40 or 50°C. Saponified extracts solubilized in solutions containing diethyl ether had greater concentrations of lutein- than hexane- or tetrahydrofuran-based solutions, with peak areas above LoQ values. The solution containing diethyl ether solubilized similar concentrations of retinol, α-tocopherol, and β-carotene when compared with other solutions. The proposed optimized method allows for the simultaneous determination of carotenoids from milk with increased lutein and zeaxanthin sensitivity without sacrificing recovery of retinol, α-tocopherol, and β-carotene. 相似文献
119.
120.
建立了固相萃取-高效液相色谱-柱后衍生荧光法用于测定奶粉中维生素B11含量。奶粉酶解样液经固相萃取小柱纯化后,在ZORBAX SB-C18色谱柱上,以pH=3.5、浓度为0.05mol/L磷酸二氢钾-乙腈体系为流动相,流速为1.0mL/min,进样量20μL,以0.5%过硫酸钾溶液为衍生试剂,反应器温度为60℃,流速0.5mL/min,经荧光检测器(Ex=365nm,Em=440nm,增幅值100,衰减值16)检测定量。结果表明:在0.02~1.76μg/mL范围内该方法线性良好,R2=0.9999,检测限为4ng/mL,定量限为12ng/mL,灵敏度足以满足奶粉检测的需要,方法回收率在92.5%~95.7%之间,变异系数为1.32%。 相似文献