全文获取类型
收费全文 | 51500篇 |
免费 | 4047篇 |
国内免费 | 2064篇 |
专业分类
电工技术 | 1790篇 |
技术理论 | 1篇 |
综合类 | 2555篇 |
化学工业 | 12628篇 |
金属工艺 | 976篇 |
机械仪表 | 2496篇 |
建筑科学 | 770篇 |
矿业工程 | 864篇 |
能源动力 | 2154篇 |
轻工业 | 10467篇 |
水利工程 | 268篇 |
石油天然气 | 19492篇 |
武器工业 | 65篇 |
无线电 | 312篇 |
一般工业技术 | 1259篇 |
冶金工业 | 817篇 |
原子能技术 | 53篇 |
自动化技术 | 644篇 |
出版年
2024年 | 162篇 |
2023年 | 629篇 |
2022年 | 1244篇 |
2021年 | 1571篇 |
2020年 | 1663篇 |
2019年 | 1698篇 |
2018年 | 1404篇 |
2017年 | 1769篇 |
2016年 | 1924篇 |
2015年 | 1754篇 |
2014年 | 2852篇 |
2013年 | 3187篇 |
2012年 | 3480篇 |
2011年 | 3617篇 |
2010年 | 2582篇 |
2009年 | 2400篇 |
2008年 | 2127篇 |
2007年 | 2778篇 |
2006年 | 3019篇 |
2005年 | 2666篇 |
2004年 | 2367篇 |
2003年 | 2198篇 |
2002年 | 1898篇 |
2001年 | 1585篇 |
2000年 | 1377篇 |
1999年 | 1164篇 |
1998年 | 945篇 |
1997年 | 800篇 |
1996年 | 638篇 |
1995年 | 506篇 |
1994年 | 393篇 |
1993年 | 254篇 |
1992年 | 233篇 |
1991年 | 178篇 |
1990年 | 124篇 |
1989年 | 84篇 |
1988年 | 49篇 |
1987年 | 45篇 |
1986年 | 23篇 |
1985年 | 61篇 |
1984年 | 57篇 |
1983年 | 39篇 |
1982年 | 26篇 |
1981年 | 8篇 |
1980年 | 14篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1976年 | 4篇 |
1951年 | 5篇 |
1944年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
101.
白马循环流化床示范电站600MW超临界CFB机组自投运以来,A、B汽动给水泵组经常出现润滑油质偏差现象,主要原因为油中含水过大造成。通过对给水泵相关系统进行全面的分析研究,指出了润滑油进水的原因是,给水泵轴承和密封水采用的呼吸器易堵塞造成回油室为较大负压状态。给水泵转速变化时,低压密封水室压力轻微波动,微正压的水进入微负压的回油室,造成油中微量带水。经过分析研究提出改进建议,运行后取得了较好效果,汽动给水泵组的油中含水量大幅降低,保证了机组安全稳定运行。 相似文献
102.
103.
Yashvir Singh Abhishek Sharma Nishant Singh Amneesh Singla Pankaj Mohan Rastogi 《国际自然能源杂志》2020,41(13):1534-1547
ABSTRACT Fossil fuel resource is on the draining stage which leads to an increment in the cost of the petroleum products. Nowadays, research is focused on the development of environmental friendly lubricants which are derivatives of renewable sources. Inedible plant oil-driven bio-lubricants are environmentally friendly because they are non-hazardous, biodegradable, as well as there is no emission of toxic gases. This study involves the characterisations, advantages, as well as utilisation of inedible plant oil-driven bio-lubricants as an alternative for tribological applications. This report presents the status about the global lubricant market as well as potential outlook. Inedible plant oil-driven bio-lubricants bear high viscosity, high lubricity, and high viscosity index which can enhance the equipment service life and has the ability to carry high load and results in minimum amount of metal traces during combustion. 相似文献
104.
A heavy crude oil has been treated with deuterated alkylating reagents (CD3I and C2D5I) and directly analyzed without any prior fractionation and chromatographic separation by high-field Orbitrap Fourier Transform Mass Spectrometry (FTMS) and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) using electrospray ionization (ESI). The reaction of a polycyclic aromatic sulfur heterocycles (PASHs) dibenzothiophene (DBT), in the presence of silver tetrafluoroborate (AgBF4) with ethyl iodide (C2H5I) in anhydrous dichloroethane (DCE) was optimized as a sample reaction to study heavy crude oil mixtures, and the reaction yield was monitored and determined by proton nuclear magnetic resonance spectroscopy (1H-NMR). The obtained conditions were then applied to a mixture of standard aromatic CH-, N-, O- and S-containing compounds and then a heavy crude oil, and only sulfur-containing compounds were selectively alkylated. The deuterium labeled alkylating reagents, iodomethane-d3 (CD3I) and iodoethane-d5 (C2D5I), were employed to the alkylation of heavy crude oil to selectively differentiate the tagged sulfur species from the original crude oil. 相似文献
105.
Francesco Di Girolamo Andrea Masotti Isabella Lante Margherita Scapaticci Cosima Damiana Calvano Carlo Zambonin Maurizio Muraca Lorenza Putignani 《International journal of molecular sciences》2015,16(9):20896-20912
Extra virgin olive oil (EVOO) with its nutraceutical characteristics substantially contributes as a major nutrient to the health benefit of the Mediterranean diet. Unfortunately, the adulteration of EVOO with less expensive oils (e.g., peanut and corn oils), has become one of the biggest source of agricultural fraud in the European Union, with important health implications for consumers, mainly due to the introduction of seed oil-derived allergens causing, especially in children, severe food allergy phenomena. In this regard, revealing adulterations of EVOO is of fundamental importance for health care and prevention reasons, especially in children. To this aim, effective analytical methods to assess EVOO purity are necessary. Here, we propose a simple, rapid, robust and very sensitive method for non-specialized mass spectrometric laboratory, based on the matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) coupled to unsupervised hierarchical clustering (UHC), principal component (PCA) and Pearson’s correlation analyses, to reveal corn oil (CO) adulterations in EVOO at very low levels (down to 0.5%). 相似文献
106.
油浸变压器的消防及排水系统关系着电厂安全,但目前其消防排水的设计多凭经验估算。本文提出一套较为完整的变压器消防排水系统的计算方法,有利于提高设计质量。 相似文献
107.
This paper studies synthesis and characterization of 2-monoacylglycerols (2-MAGs), generally used for structured lipid production. Synthesis used canarium oil by enzymatic reaction using immobilized lipase from Mucor miehei that has a specific activity on the sn-1 and 3 of the triacylglycerol structure. Characterization of 2-MAGs by thin layer chromatography using a standard of 2-oleoylglycerol followed by isolation and purification to determine the fatty acids composition.The highest composition of fatty acids on 2-MAGs were unsaturated fatty acids, namely oleic acid (939.8 ppm) and linoleic acid (445.5 ppm), therefore it could be used for the synthesis of structured lipid. 相似文献
108.
介绍了基于MCGS的洗油空穴反应实验装置远程计算机自动控制系统的硬件、软件设计及其实现过程,为后续进一步的研究工作提供理论和实践基础。 相似文献
109.
介绍了普旭真空泵的工艺作用、结构及工作原理,日常操作维护注意事项、常见故障及排除措施等。及时发现了设备问题,实现了设备的计划维修,使设备能够达到长周期稳定运转的目的。 相似文献
110.
Correlation of structural characterization and viscosity measurements with total unsaturation: An effective method for controlling ozonation in the preparation of ozonated grape seed and sunflower oils 下载免费PDF全文