全文获取类型
收费全文 | 363699篇 |
免费 | 29460篇 |
国内免费 | 16239篇 |
学科分类
工业技术 | 409398篇 |
出版年
2024年 | 740篇 |
2023年 | 5494篇 |
2022年 | 8876篇 |
2021年 | 13923篇 |
2020年 | 10710篇 |
2019年 | 8682篇 |
2018年 | 10094篇 |
2017年 | 11289篇 |
2016年 | 10335篇 |
2015年 | 14311篇 |
2014年 | 18035篇 |
2013年 | 21669篇 |
2012年 | 23795篇 |
2011年 | 26156篇 |
2010年 | 23174篇 |
2009年 | 21861篇 |
2008年 | 21434篇 |
2007年 | 20467篇 |
2006年 | 20643篇 |
2005年 | 18093篇 |
2004年 | 12272篇 |
2003年 | 10913篇 |
2002年 | 10086篇 |
2001年 | 9003篇 |
2000年 | 8905篇 |
1999年 | 9468篇 |
1998年 | 7210篇 |
1997年 | 6145篇 |
1996年 | 5750篇 |
1995年 | 4780篇 |
1994年 | 3876篇 |
1993年 | 2618篇 |
1992年 | 2065篇 |
1991年 | 1553篇 |
1990年 | 1225篇 |
1989年 | 988篇 |
1988年 | 811篇 |
1987年 | 491篇 |
1986年 | 391篇 |
1985年 | 239篇 |
1984年 | 188篇 |
1983年 | 141篇 |
1982年 | 130篇 |
1981年 | 74篇 |
1980年 | 97篇 |
1979年 | 43篇 |
1978年 | 17篇 |
1977年 | 23篇 |
1976年 | 29篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Amino acid modified polyaspartic acids were evaluated as calcium-scale inhibitors. Feasibility of scale inhibition experiments was analyzed by molecular dynamics simulation and Gaussian optimization, and the scale inhibition mechanism was theoretically analyzed. Scale inhibition performance was studied by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, static scale inhibition experiments, and electrochemical performance testing, which provided an experimental basis for the molecular dynamics simulation. The experimental results showed that Arg-SA-PASP has better scale inhibition and corrosion inhibition performance than His-SA-PASP. The scale inhibition effect increased with increasing concentration. Electrochemical tests indicated that Arg-SA-PASP is an excellent scale and corrosion inhibitor. 相似文献
103.
Yihua Feng Peidong Yuan Li Wang Jiyun Zhang Jiahui Zhang Xuan Zhou 《International Journal of Applied Ceramic Technology》2020,17(3):1108-1118
Surface texture is considered an important measure to improve the cutting performance of a tool. In this study, we have prepared three types of textured and conventional tools on the rake face by an in-situ formed method. During the experiment, the best parameters of three types of textured tools were selected for dry cutting AISI 1045 steel at different cutting speeds. Cutting forces, cutting temperatures, workpiece surface roughness, and tool wear were measured during the cutting process. The results showed that textured tools have significantly reduced cutting force, cutting temperature, and tool wear, and the roughness of the workpiece was improved compared with the conventional tool. The micro-pit texture tool has less stress contact region than the micro-groove width texture tool, but the micro-groove width texture tool exhibiting the best cutting performance. This investigation clearly showed that the textured tool prepared by the in-situ formed method has improved cutting performance. 相似文献
104.
105.
Fluorescence‐Activated Cell Sorters: Standing Surface Acoustic Wave (SSAW)‐Based Fluorescence‐Activated Cell Sorter (Small 40/2018) 下载免费PDF全文
107.
为了极大限度地提高本煤层预抽效果,以马兰煤矿为研究对象,针对目前马兰煤矿的瓦斯赋存情况和现阶段所采取的抽放措施,从抽放钻孔的孔径、孔深、布置方式、封孔质量和增加煤层透气性等方面进行探索。实践表明,以上方法的运用,能够有效地提高本煤层预抽抽放效果,保证工作面安全生产。 相似文献
108.
ABSTRACT Separation of ilmenite from titanaugite was investigated by magnetic coating. By enlarging magnetic difference between ilmenite and titanaugite, ilmenite was efficiently recovered. Scanning electron microscope and vibrating sample magnetometer results indicated that magnetite selectively coated onto ilmenite surface and increased its magnetism, which resulted in different magnetic separation behavior between ilmenite and titanaugite. FTIR and contact angle measurements confirmed that the adsorption difference of sodium oleate resulted in a stronger hydrophobicity on magnetite and ilmenite than titanaugite. Interaction energy analysis illustrated that hydrophobic association interaction on ilmenite was stronger than that on titanaugite, and which led to the selective coating of magnetite onto ilmenite. 相似文献
109.
110.
溶剂萃取法是盐湖提锂的重要工艺方法。采用磷酸三丁酯(TBP)/1-丁基-3-甲基咪唑双三氟甲基磺酰亚胺盐([C4mim][NTf2])离子液体体系对高镁锂比盐湖卤水中的锂进行萃取分离提取实验,对负载有机相的洗涤和反萃过程进行了研究。萃取实验:在TBP与[C4mim][NTf2]体积比为9∶1、相比(有机相与水相的体积比)为2∶1条件下,锂离子与其他离子的分离系数分别为β(锂/钠)=94.70、β(锂/钾)=148.85、β(锂/镁)=131.81。洗涤实验:系统考察了洗涤剂种类及浓度、相比、洗涤次数等因素对杂质离子洗脱率的影响,结果发现氯化锂和盐酸的混合溶液是从负载有机相中洗涤除去杂质离子的有效洗涤剂。洗涤过程适宜条件:洗涤剂中氯化锂浓度为4 mol/L、盐酸浓度为0.5 mol/L,相比为5∶1,洗涤次数为2次。反萃实验:用稀盐酸(1.0 mol/L)对负载有机相进行反萃取,在相比为1∶1条件下,单级反萃率达到97.81%。研究表明,离子液体体系作为一种新型萃取体系,在高镁锂比盐湖卤水中提取锂具有较好的应用前景。 相似文献