全文获取类型
收费全文 | 7562篇 |
免费 | 853篇 |
国内免费 | 640篇 |
专业分类
电工技术 | 273篇 |
技术理论 | 4篇 |
综合类 | 638篇 |
化学工业 | 1384篇 |
金属工艺 | 563篇 |
机械仪表 | 299篇 |
建筑科学 | 848篇 |
矿业工程 | 218篇 |
能源动力 | 456篇 |
轻工业 | 637篇 |
水利工程 | 241篇 |
石油天然气 | 807篇 |
武器工业 | 61篇 |
无线电 | 1039篇 |
一般工业技术 | 644篇 |
冶金工业 | 322篇 |
原子能技术 | 266篇 |
自动化技术 | 355篇 |
出版年
2024年 | 28篇 |
2023年 | 114篇 |
2022年 | 244篇 |
2021年 | 322篇 |
2020年 | 263篇 |
2019年 | 287篇 |
2018年 | 228篇 |
2017年 | 334篇 |
2016年 | 310篇 |
2015年 | 333篇 |
2014年 | 425篇 |
2013年 | 539篇 |
2012年 | 513篇 |
2011年 | 581篇 |
2010年 | 443篇 |
2009年 | 448篇 |
2008年 | 373篇 |
2007年 | 483篇 |
2006年 | 460篇 |
2005年 | 341篇 |
2004年 | 320篇 |
2003年 | 259篇 |
2002年 | 223篇 |
2001年 | 206篇 |
2000年 | 171篇 |
1999年 | 118篇 |
1998年 | 126篇 |
1997年 | 110篇 |
1996年 | 74篇 |
1995年 | 76篇 |
1994年 | 52篇 |
1993年 | 40篇 |
1992年 | 31篇 |
1991年 | 35篇 |
1990年 | 30篇 |
1989年 | 18篇 |
1988年 | 22篇 |
1987年 | 11篇 |
1986年 | 4篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 13篇 |
1982年 | 10篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1959年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有9055条查询结果,搜索用时 15 毫秒
1.
There are many potential causes of corrosion in animal buildings. Animals exhale large quantities of moisture into the air creating high relative humidity in the building if the moisture is not properly vented. High humidity increases the potential for condensation. In addition, ammonia may be found in large quantities in animal buildings. Ammonia is released from manure and urine. In addition, ammonium chloride is used as a nitrogen source in fertilisers. In this study, the atmospheric corrosion of hot-dip-galvanised steel and zinc alloy-coated steel such as zinc–aluminium and zinc–aluminium–magnesium has been studied in atmospheres containing different levels of ammonia. Investigations have also been conducted at different levels of ammonium chloride. The results are discussed in view of the mechanisms of corrosion of zinc and zinc alloy-coated steel in ammonia and ammonium chloride-containing environments. 相似文献
2.
Xiaopu Lyu Yunxi Huo Jin Yang Dawen Yao Kaimin Li Haoxian Lu Yangzong Zeren Hai Guo 《Indoor air》2021,31(5):1340-1352
Due to the high health risks associated with indoor air pollutants and long-term exposure, indoor air quality has received increasing attention. In this study, we put emphasis on the molecular composition, source emissions, and chemical aging of air pollutants in a residence with designed activities mimicking ordinary Hong Kong homes. More than 150 air pollutants were detected at molecular level, 87 of which were quantified at a time resolution of not less than 1 hour. The indoor-to-outdoor ratios were higher than 1 for most of the primary air pollutants, due to emissions of indoor activities and indoor backgrounds (especially for aldehydes). In contrast, many secondary air pollutants exhibited higher concentrations in outdoor air. Painting ranked first in aldehyde emissions, which also caused great enhancement of aromatics. Incense burning had the highest emissions of particle-phase organics, with vanillic acid and syringic acid as markers. The other noteworthy fingerprints enabled by online measurements included linoleic acid, cholesterol, and oleic acid for cooking, 2,5-dimethylfuran, stigmasterol, iso-/anteiso-alkanes, and fructose isomers for smoking, C28-C34 even n-alkanes for candle burning, and monoterpenes for the use of air freshener, cleaning agents, and camphor oil. We showed clear evidence of chemical aging of cooking emissions, giving a hint of indoor heterogeneous chemistry. This study highlights the value of organic molecules measured at high time resolutions in enhancing our knowledge on indoor air quality. 相似文献
3.
The potential energy profile of the reaction between dimethyl disulfide and OH? radicals is explored by utilizing ab initio and hybrid meta density functional theory methods. Having the energies and structural data of the stationary points, statistical rate theories, such as transition state theory and variable reaction coordinate-transition state theory, are employed to compute the overall rate constants, and discuss the mechanism and product channels. On the basis of the calculations, the overall rate coefficient is predicted to be 2.49?×?10?10?cm3?molecule?1?s?1 at 298?K. It is found that in the most favorable pathway, the reaction proceeds via formation of the relatively unstable intermediate CH3S?(OH)SCH3 decomposing rapidly to yield CH3S?+CH3SOH. 相似文献
4.
随着我国环境保护法规《大气污染防治法》的修订和《涂料征收消费税通知》的公布,探讨了其对船舶涂料企业的冲击及其应对措施。 相似文献
5.
《Planning》2019,(2)
2017年,美国心脏病学会和美国心脏协会提出将高血压诊断标准降为130/80 mm Hg (1 mm Hg=0. 133 kPa),这与其他指南有所不同。降压治疗的核心目标在于靶器官的保护,近年来降压治疗与脑小血管病预防的相关问题日益受到临床重视。目前研究结果表明,降压治疗对腔隙性卒中患者的二级预防以及白质病变进展的预防可能有一定积极意义,但确切的降压目标值并未确定。血压与临床结局可能呈现J型关系,血压过低或过高可能均有害,而取得最大获益的降压目标有待进一步探索。 相似文献
6.
K. Borer G. Czapek F. Hasenbalg M. Hauser S. Janos P. Loaiza U. Moser K. Pretzl C. Schütz P. Wicht S. Wüthrich 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2004,520(1-3):112-115
The ORPHEUS dark matter detector consists of 450 g superconducting tin granules with diameters of 28 and 36 μm. The detector has been operating in the shallow site of the underground laboratory in Bern (70 m.w.e). First preliminary results on WIMP detection sensitivity will be presented. 相似文献
7.
选取具有代表性的碳钢、不锈钢、镀锌碳钢、铝、钛和铜挂片,在某企业不同部位投放后进行为期半年的大气腐蚀试验,得出了在半年期中的腐蚀规律。在此基础上,对每种金属材料的腐蚀特点进行总结,并对大气腐蚀的各种影响因素进行分析,提出了行之有效的防护措施。 相似文献
8.
R. Maciel Filho C. B. Batistella P. Sbaite A. Winter C. J. G. Vasconcelos M. R. Wolf Maciel A. Gomes L. Medina R. Kunert 《Petroleum Science and Technology》2006,24(3):275-283
The term atmospheric residue describes the material at the bottom of the atmospheric distillation tower having a lower boiling point limit of about 340°C; the term vacuum residue (heavy petroleum fractions) refers to the bottom of the vacuum distillation, which has an atmospheric equivalent boiling point (AEBP) above 540°C. In this work, the objective is to evaluate the behavior of different kinds of Brazilian atmospheric and vacuum residues using molecular distillation. The Falling Film Molecular Distillator was used. For the results obtained through this process, a significant range of temperature can be explored avoiding the thermal decomposition of the material. So these results are very important to the refinery decisions and improvements. The Experimental Factorial Design results showed that the temperature has more influence on the process than the feed flow rate, when a higher percentage of distillate is required. 相似文献
9.
报道了大气探测红外分光辐射计Ⅱ型(ASIS-2)模样,它具有20个通道,可以从卫星探测大气温度廓线和水汽垂直分布.它与美国TIROS-N/NOAA气象卫星上的高分辨率红外辐射探测仪(HIRS)相比,在光学、电子学和机械等方面都作了改进.其仪器灵敏度优于HIRS-1仪器,而与HIRS-2接近.它具有可增加2个红外通道和多个可见光通道的潜力. 相似文献
10.