首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1966篇
  免费   66篇
  国内免费   257篇
电工技术   48篇
综合类   96篇
化学工业   228篇
金属工艺   114篇
机械仪表   94篇
建筑科学   94篇
矿业工程   17篇
能源动力   12篇
轻工业   226篇
水利工程   34篇
石油天然气   51篇
无线电   193篇
一般工业技术   873篇
冶金工业   56篇
原子能技术   28篇
自动化技术   125篇
  2024年   40篇
  2023年   122篇
  2022年   142篇
  2021年   152篇
  2020年   44篇
  2019年   35篇
  2018年   33篇
  2017年   33篇
  2016年   27篇
  2015年   40篇
  2014年   48篇
  2013年   53篇
  2012年   251篇
  2011年   314篇
  2010年   61篇
  2009年   46篇
  2008年   169篇
  2007年   138篇
  2006年   134篇
  2005年   87篇
  2004年   66篇
  2003年   48篇
  2002年   28篇
  2001年   37篇
  2000年   24篇
  1999年   24篇
  1998年   13篇
  1997年   13篇
  1996年   11篇
  1995年   9篇
  1994年   7篇
  1993年   3篇
  1992年   2篇
  1991年   10篇
  1990年   7篇
  1989年   1篇
  1987年   3篇
  1986年   2篇
  1984年   2篇
  1983年   1篇
  1982年   8篇
  1978年   1篇
排序方式: 共有2289条查询结果,搜索用时 15 毫秒
1.
Pathogens pose a serious challenge to environmental sanitation and a threat to public health.The frequent use of chemicals for sterilization in recent years has not only caused secondary damage to the environment but also increased pathogen resistance to drugs,which further threatens public health.To address this issue,the use of non-chemical antibacterial means has become a new trend for environmental disinfection.In this study,we developed red phosphorus nanoparticles(RPNPs),a safe and degradable photosensitive material with good photocatalytic and photothermal properties.The red phosphorus nanoparticles were prepared using a template method and ultrasonication.Under the irradiation of simulated sunlight for 20 min,the RPNPs exhibited an efficiency of 99.98%in killing Staphylococcus aureus due to their excellent photocatalytic and photothermal abilities.Transmission electron microscopy and ultraviolet–visible spectroscopy revealed that the RPNPs exhibited degradability within eight weeks.Both the RPNPs and their degradation products were nontoxic to fibroblast cells.Therefore,such RPNPs are expected to be used as a new type of low-cost,efficient,degradable,biocompatible,and eco-friendly photosensitive material for environmental disinfection.  相似文献   
2.
Thermosetting materials are widely used as encapsulation in the electrical packaging to protect the core electronic components from external force, moisture, dust, and other factors. However, the spreading and curing behaviors of such kind of fluid on a heated surface have been rarely explored. In this study, we experimentally and numerically investigated the spreading and curing behaviors of the silicone(OE6550 A/B, which is widely used in the light-emitting diode packaging) droplet with diameter of ~2.2 mm on a heated surface with temperature ranging from 25 ℃ to 250 ℃. For the experiments, we established a setup with high-speed camera and heating unit to capture the fast spreading process of the silicone droplet on the heated surface. For the numerical simulation, we built a viscosity model of the silicone by using the Kiuna's model and combined the viscosity model with the Volume of Fluid(VOF) model by the User Defined Function(UDF) method. The results show that the surface temperature significantly affected the spreading behaviors of the silicone droplet since it determines the temperature and viscosity distribution inside the droplet. For surface temperature varied from 25 ℃ to 250 ℃, the final contact radius changed from ~2.95 mm to ~1.78 mm and the total spreading time changed from ~511 s to ~0.15 s. By further analyzing the viscosity evolution of the droplet, we found that the decreasing of the total spreading time was caused by the decrease of the viscosity under high surface temperature at initial spreading stage, while the reduction of the final contact radius was caused by the curing of the precursor film. This study supplies a strategy to tuning the spreading and curing behavior of silicone by imposing high surface temperature, which is of great importance to the electronic packaging.  相似文献   
3.
The method for refining the straight-run diesel fuel was studied in laboratory scale in order to make the acid number of diesel fraction comply with the standard while removing the naphthenic acids contained in diesel without causing environmental pollution. After comparing the effect of refining using three solvents, the isopropyl alcohol-HOA was specified as the best solvent. Meanwhile, the relationship between the acid number of diesel fraction and the amount of solvent used and the relationship between the concentration of solvent and temperature and the stability of diesel in terms of its acid number were also investigated. Experimental results had shown that when the mass fraction of the HOA-IPA solvent was 20% at a dosage of 17 mL of the solvent and a temperature of 30℃, the acid number of the refined diesel fraction was 0.015 mg KOH/g with a good stability of acidity in the diesel fraction,  相似文献   
4.
膜技术在醋酸生产中的应用   总被引:3,自引:0,他引:3  
膜技术在醋酸生产中的应用孙晓辉,郝建飞,王竞(大连市卫生防疫站食品科)(吉林省粮油运销总公司)(哈尔滨工业大学应化系)膜分离技术是近二十年迅速发展起来的分离技术,由于它具有节能、优质、高效等优点,已广泛用于医药、化工、生化、电子以及食品工业等领域,展...  相似文献   
5.
High speedsteel (HSS) ,ischaracterizedbyex cellenthardness ,wearresistance ,and goodredhardness .Recently ,HSSisappliedtomanufacturehotrollingrollstoproducestripsofgoodshapeandsmallcrownwithextendedrollservicelife[1,2 ] .TheHSSisappliedtomanufacturerollcollarfor…  相似文献   
6.
OntheRealizationofCurrent-ModeContinuousTimeOperationalTransconductanceCapacitanceFilter¥GuoJingboandHanQingquan(ChangchunPos...  相似文献   
7.
珠宝首饰高贵华丽,是出席宴会场合的最佳拍档,时尚配饰款式灵匚,是衬托时装的最佳首选,在今年6月香港珠宝钟表展暨亚洲时尚首饰及配饰展上,时尚配饰呈现出多姿多彩的面貌。  相似文献   
8.
有梭织机的两项改进措施1前IN斩棘断后的修复措施我厂现有1515系列有梭织机461台,在生产过程中,因装备不当、换梭轧校等原因,造成前阳翰损坏,数量较大。为降低税件消耗,我们制作了同心轴(如罔1),以保证修复后的前闭轨同心度的要求。具体办法如下:(l...  相似文献   
9.
ElectronmicroscopicobservationsandDNAchainfragmentationstudiesonapoptosisinbonetumorcelsinducedby153SmEDTMPZhuShouPeng,Xia...  相似文献   
10.
1 OverviewTheGeheyanPowerStationhasfourcircularinlettun nels,ontherightbankofdamsite,withtheirexcavationdi ameterof 11.3mto 12.5m,after liningdiameterof 9.5m,axis to axisspacingof2 4m.Thethicknessofpillarsareequaltothetunneldiameter.Theintakecenterisateleva ti…  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号