全文获取类型
收费全文 | 8724篇 |
免费 | 812篇 |
国内免费 | 77篇 |
专业分类
电工技术 | 26篇 |
综合类 | 324篇 |
化学工业 | 582篇 |
金属工艺 | 25篇 |
机械仪表 | 99篇 |
建筑科学 | 331篇 |
矿业工程 | 14篇 |
能源动力 | 82篇 |
轻工业 | 7457篇 |
水利工程 | 33篇 |
石油天然气 | 79篇 |
武器工业 | 1篇 |
无线电 | 41篇 |
一般工业技术 | 398篇 |
冶金工业 | 40篇 |
原子能技术 | 15篇 |
自动化技术 | 66篇 |
出版年
2024年 | 64篇 |
2023年 | 197篇 |
2022年 | 312篇 |
2021年 | 431篇 |
2020年 | 365篇 |
2019年 | 387篇 |
2018年 | 291篇 |
2017年 | 320篇 |
2016年 | 299篇 |
2015年 | 334篇 |
2014年 | 412篇 |
2013年 | 452篇 |
2012年 | 765篇 |
2011年 | 735篇 |
2010年 | 424篇 |
2009年 | 373篇 |
2008年 | 349篇 |
2007年 | 539篇 |
2006年 | 486篇 |
2005年 | 384篇 |
2004年 | 302篇 |
2003年 | 280篇 |
2002年 | 213篇 |
2001年 | 170篇 |
2000年 | 128篇 |
1999年 | 132篇 |
1998年 | 117篇 |
1997年 | 66篇 |
1996年 | 45篇 |
1995年 | 44篇 |
1994年 | 33篇 |
1993年 | 34篇 |
1992年 | 31篇 |
1991年 | 18篇 |
1990年 | 21篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 10篇 |
1978年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有9613条查询结果,搜索用时 31 毫秒
31.
针对生鲜闭环供应链网络设计问题,建立了一种基于生鲜闭环供应链网络的鲁棒优化模型,以解决供应链网络中的不确定性问题。首先,针对涵盖五个节点的生鲜供应链网络结构建立了多周期、多产品,以最小化成本、最小环境影响为目标的混合整数规划模型,采用模糊折中规划与区间数据鲁棒优化方法进行处理;其次,在原有蜜獾算法的基础上引入差分进化原则,增强算法的全局搜索能力与收敛速度;最后,通过MATLAB数值分析与仿真实例表明,所提鲁棒优化模型与蜜獾算法在求解生鲜闭环供应链网络设计问题中具有明显优势。 相似文献
32.
Natsuhiko Kuratomi Shinichi Takano Mitsuharu Fukasawa Shinya Maekawa Makoto Kadokura Hiroko Shindo Ei Takahashi Sumio Hirose Yoshimitsu Fukasawa Satoshi Kawakami Hiroshi Hayakawa Hitomi Takada Natsuko Nakakuki Ryoh Kato Tatsuya Yamaguchi Yasuhiro Nakayama Hiromichi Kawaida Hiroshi Kono Taisuke Inoue Tetsuo Kondo Daisuke Ichikawa Nobuyuki Enomoto 《International journal of molecular sciences》2021,22(6)
New biomarkers are needed to further stratify the risk of malignancy in intraductal papillary mucinous neoplasm (IPMN). Although microRNAs (miRNAs) are expected to be stable biomarkers, they can vary owing to a lack of definite internal controls. To identify universal biomarkers for invasive IPMN, we performed miRNA sequencing using tumor-normal paired samples. A total of 19 resected tissues and 13 pancreatic juice samples from 32 IPMN patients were analyzed for miRNA expression by next-generation sequencing with a two-step normalization of miRNA sequence data. The miRNAs involved in IPMN associated with invasive carcinoma were identified from this tissue analysis and further verified with the pancreatic juice samples. From the tumor-normal paired tissue analysis of the expression levels of 2792 miRNAs, 20 upregulated and 17 downregulated miRNAs were identified. In IPMN associated with invasive carcinoma (INV), miR-10a-5p and miR-221-3p were upregulated and miR-148a-3p was downregulated when compared with noninvasive IPMN. When these findings were further validated with pancreatic juice samples, miR-10a-5p was found to be elevated in INV (p = 0.002). Therefore, three differentially expressed miRNAs were identified in tissues with INV, and the expression of miR-10a-5p was also elevated in pancreatic juice samples with INV. MiR-10a-5p is a promising additional biomarker for invasive IPMN. 相似文献
33.
Nuchanart Suealek Thipaporn Tharavanij Robert M. Hackman Carl L. Keen Roberta R. Holt Benjapun Burawat Ammara Chaikan Rattana Tiengtip Panadda Rojpibulstit 《European Journal of Lipid Science and Technology》2021,123(2):2000126
The potential cardiovascular benefit of virgin olive oil (VOO) is widely recognized. However, the use of VOO at very high cooking temperatures makes these oils poorly suited for many Asian dishes. The use of tea seed oil (TSO) is increasing in Thailand, with TSO having a higher smoke point than VOO. The current study examines the effects of daily TSO intake in healthy adults. In a randomized, single-blind crossover design, 12 men consumed for 3 weeks 40 g day−1 of food prepared with either TSO or VOO as a cooking oil. Plasma lipids, thiobarbituric acid reactive substances (TBARS), and oxidant defense enzyme activities are measured before and after each 3-week intervention period. Gas chromatography analysis of TSO and VOO demonstrates that both oils are equally high in monounsaturated fatty acid. The dietary incorporation of TSO and VOO for three weeks reduces low-density lipoprotein cholesterol (LDL-C) concentrations by 15% and 13%, respectively; with total cholesterol (TC) levels lowered by 10% in both groups. No significant changes in TBARS or antioxidant enzyme activity is observed. These results support the concept that Thai TSO can be utilized as a suitable and healthy alternative oil for high-temperature cooking in many Thai and Asian diets. Practical Applications: Tea seed oil from Camellia oleifera grown in Thailand has been recently reported to favorably lower lipid profiles in hamsters fed a high-fat diet in a manner similar to feeding refined olive oil or grapeseed oil. A pilot crossover trial is conducted to compare the effects of three weeks of daily intake of either TSO or VOO in healthy human adults. Consumption of both oils produced significant reductions in TC and LDL-C. Thai TSO leads to favorable lipid profiles and is a reasonable choice for many Thai and Asian food recipes. 相似文献
34.
采用客观仪器评价方法对含鲜奶面霜单次使用后的缓解皮肤红斑反应的功效进行研究。选择30名18~55周岁有效受试者为研究对象,使用胶带粘贴及组胺刺激构建皮肤红斑反应模型,并采用无创仪器的方式检测并记录实验组、安慰剂组、阴性组及空白组受试者在组胺造模前、造模后、涂抹产品后30 min和60 min时的皮肤红斑指数EI值、皮肤敏感度值,采集皮肤图像,通过SPSS数据统计软件对实验结果进行统计分析。结果显示,含鲜奶面霜可以持续改善皮肤红斑指数EI值和皮肤敏感度,缓解由组胺导致的皮肤红晕反应,说明其具有一定的缓解皮肤红斑反应,改善皮肤敏感状态的功能。 相似文献
35.
超滤法生产锦橙清汁的研究 总被引:3,自引:0,他引:3
采用不同超滤膜进行锦橙汁的澄清试验,测定透液通量和清汁万分的变化,评价澄清效果,试探膜的清洗方法,结果表明:几种膜均能得到稳定的锦橙清汁,PAN5万膜透液通量最大。 相似文献
36.
欧盟在对硫丹进行风险评估的基础上,于2005年5月3日和6月2日,先后发布SPS和TBT通报,撤销硫丹作为植物保护产品登记。按照欧盟相关指令的要求,硫丹在茶叶中的MRLs由30mg/kg调整为0.01mg/kg。硫丹是目前我国茶叶生产中的农药推广品种,而且欧盟是我国重要的茶叶出口市场,欧盟的此项规定对我国茶叶出口有一定的影响,应当采取措施积极应对。 相似文献
37.
Raffaele Sacchi Isabel Medina Santiago P. Aubourg Francesco Addeo Livio Paolillo 《Journal of the American Oil Chemists' Society》1993,70(3):225-228
Based on proton nuclear magnetic resonance (1H-NMR) spectroscopy, a rapid and structure-specific method for the determination of ω-3 polyunsaturated fatty acids (PUFAs)
in fish lipids is presented. The different chemical shift observed for the methyl resonance of ω-3 PUFAs (δ=0.95 ppm) with
respect to the methyl resonance of all other fatty acids (δ=0.86 ppm) has provided the possibility of proposing a new and
rapid method for the determination of ω-3 PUFA content. Twenty-four fish lipid samples (raw, cooked and canned albacore tuna)
produced results that showed good agreement between1H-NMR analysis and gas chromatographic determination. Raw and cooked samples showed significantly higher levels of ω-3 PUFA
than canned tuna. 相似文献
38.
39.
分子修饰法制备油溶性茶多酚及其抗氧化性能的研究 总被引:4,自引:0,他引:4
采用分子修饰法制备了豆油脂肪酸酐修饰的茶多酚,通过红外光谱对分子修饰的茶多酚进行了结构表征。将修饰后的茶多酚作为油脂的抗氧化剂,添加到豆油中,考察其溶解性及抗氧化性能。结果表明,有机基团修饰的茶多酚具有优良的分散性,可提高豆油的抗氧化性能。在相同浓度时,豆油脂肪酸酐修饰的茶多酚抗氧化活性优于茶多酚和BHT。 相似文献
40.
超声波提取-吸附分离-气相色谱法测定茶叶中农药残留 总被引:1,自引:0,他引:1
将超声提取-吸附分离的预处理技术用于气相色谱法检测茶叶中的农药残留。对超声波提取条件和吸附分离柱(自制)的结构进行了优化。建立了茶叶中有机磷类和菊酯类农药残留的气相色谱法定量测定的方法。进行了3个质量分数的标准添加,甲胺磷、乐果、联苯菊酯、氯氟氰菊酯、溴氰菊酯的回收率相应为75%~95%、87%~110%、89%-102%、88%-105%、80%-93%,相对标准偏差为2.6%.4.8%,检出限为0.005-0.02mg/kg。该方法速度快、灵敏度高、重现性好。 相似文献