首页 | 官方网站   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   11159篇
  免费   1012篇
  国内免费   234篇
工业技术   12405篇
  2024年   62篇
  2023年   240篇
  2022年   379篇
  2021年   554篇
  2020年   535篇
  2019年   456篇
  2018年   386篇
  2017年   383篇
  2016年   427篇
  2015年   458篇
  2014年   552篇
  2013年   627篇
  2012年   907篇
  2011年   830篇
  2010年   576篇
  2009年   503篇
  2008年   408篇
  2007年   649篇
  2006年   596篇
  2005年   499篇
  2004年   399篇
  2003年   372篇
  2002年   306篇
  2001年   200篇
  2000年   200篇
  1999年   144篇
  1998年   142篇
  1997年   101篇
  1996年   77篇
  1995年   88篇
  1994年   56篇
  1993年   55篇
  1992年   55篇
  1991年   27篇
  1990年   27篇
  1989年   26篇
  1988年   27篇
  1987年   20篇
  1986年   12篇
  1985年   11篇
  1984年   6篇
  1983年   1篇
  1982年   8篇
  1981年   7篇
  1980年   6篇
  1979年   1篇
  1978年   1篇
  1976年   2篇
  1955年   1篇
排序方式: 共有10000条查询结果,搜索用时 812 毫秒
61.
研究了脲醛树脂的预聚物通过原位聚合对红磷进行包覆的一些影响因素。实验表明影响预聚物质量的主要因素是第一阶段尿醛比(F/U)1,第二阶段尿醛比(F/U)2,反应温度和pH值。制备预聚物的最佳条件为:第一阶段尿醛比为2.3∶1(摩尔比),第二阶段尿醛比为1.3∶1(摩尔比),pH值为5.1,反应温度为75℃。制备的预聚物来包覆红磷,颜色为白色;用微胶囊红磷阻燃聚乙烯,当含量为9%时,在500℃下残余物为4.85%。  相似文献   
62.
The electrochemical oxidation of neutral red in 0.5 mol dm−3 sulfuric acid and 0.2 mol dm−3 ferrocenesulfonic acid solution was carried out using repeated potential cycling between −0.20 and 1.40 V (versus SCE). The polymer film was electrochemically deposited on a platinum anode and had an electrochemical activity in the solution of 0.5 mol dm−3 Na2SO4 with pH ≤ 7.0. The result from the X-ray photoelectron spectroscopy (XPS) experiment shows that the anions can be doped into the polymer film during the electrochemical polymerization reaction of neutral red. The scanning electron microscopy (SEM) micrograph shows that the surface of the resulting polymer film formed on the platinum foil is covered with a compact surface consisting of micro fibers. The visible spectrum and infrared spectrum (IR) of the polymer are different from those of the corresponding monomer. A possible chemical structure of the resulting polymer was also proposed.  相似文献   
63.
A comprehensive scientific assessment of CH4 budget estimation for Indian rice paddies, based on a decade of measurements in India, is presented. Indian paddy cultivation areas contain soils that have low to medium levels of soil organic carbon. The average seasonally integrated CH4 flux (E sif) values calculated from these measurements were 15.3 ± 2.6 g m–2 for continuously flooded (CF), 6.9 ± 4.3 g m–2 for intermittently flooded (IF) single aeration (SA) and 2.2 ± 1.5 g m–2 for IF multiple aeration (MA) rice ecosystems. For CF and IF (MA) rice ecosystems having high soil organic carbon, without organic amendments, the CH4 flux (E sif) may be increased by 1.7 times relative to low soil organic carbon, whereas it may enhance by 5.3 for CF if amended organically. Organic amendment and high soil organic carbon paddy areas do not alter the methane budget estimates for India (3.6±1.4 TgY–1) much, due to their small paddy harvested area. Methane estimated using average emission factors (E sif) for all paddy water regimes, which include harvested areas having soils with high organic carbon and organic amendments, may give a budget of 5 TgY–1 for India.  相似文献   
64.
Extract of purple sunflower hulls is a potential red food colorant; however, suitable process conditions must still be identified. Selected process variables were studied using bench-scale units to prepare, clarify, concentrate and spray dry extracts. Concentration by evaporation at 32°C and addition of maltodextrin to 15% (wt/dry wt) prior to drying largely eliminated pigment degradation during those steps. Relative to water extracts, extracts prepared with 5 to 15% ethanol in water generally yielded more pigment with similar levels of degradation and loss during subsequent processing. Use of 5% ethanol/2% citric acid reduced yield by about half relative to water, but gave a powder with a lower degradation index and wetting time. Percentage recovery of pigment during concentration and drying was not greatly affected by solvent type or extraction temperature.  相似文献   
65.
李碧英  张帆  彭波 《塑料科技》2007,35(9):100-104
研究了白度化微胶囊红磷阻燃剂的制备方法,并研究了其对聚丙烯材料的氧指数影响。采用XPS、SEM、TG、磷化氢释放量、抗氧化性、吸湿性等对其进行了表征,结果表明:红磷阻燃剂微胶囊包覆效果有明显改善作用,其吸湿性、抗氧化性、PH3释放量均大大减少;XPS图谱表明99.5%的红磷已被包覆;扫描电镜显示红磷阻燃剂平均粒径为0.24μm;TG显示红磷阻燃剂的着火点已提高到435℃;氧指数测试结果表明:经红磷阻燃剂阻燃后,聚丙烯的氧指数已提高到28。  相似文献   
66.
氰烯菌酯(JS399-19)防治水稻恶苗病的研究   总被引:6,自引:2,他引:6  
氰烯菌酯(JS399-19)是一种结构新颖、作用方式独特的高效杀菌剂。离体抑菌活性测定表明,JS399-19对水稻恶苗病多菌灵敏感菌株和抗性菌株均有相似活性,EC50为0.1612~0.3136μg/mL,EC95为1.5387~6.0455μg/mL;持效性测定表明,JS399-19在10d内对恶苗病菌的抑菌率是稳定的,抑菌率为77.9%~81.4%;种子安全性试验表明,以25%JS399-19SC1:1000倍浸种处理对水稻种子的发芽势有一定的影响,但不影响发芽率、出苗率及成苗率,1:2000、1:3000、1:4000倍浸种处理时水稻种子的发芽势、发芽率、出苗率成苗率等均与空白对照无明显差异;温室小区筛选试验表明,当25%JS399-19SC1:500、1:1000、1:2000、1:3000浸种处理时30d防效均为100%,1:4000倍时防效大于92%;初步应用技术研究表明,JS399-19防治水稻恶苗病,浸种处理剂量为1:3000~4000倍,当浸种温度为15~20℃时,浸种时间以48~72h为宜。本研究为氰烯菌酯防治水稻恶苗病的应用开发提供了依据。  相似文献   
67.
The contents of natural antioxidants and the oxidative stability of rice bran oils at different refining steps were determined. Tocopherols and oryzanols were constant in crude and degummed oils but decreased in alkali-refined, bleached and deodorized oils. The process of degumming, alkali-refining, bleaching and deodorization removed 34% of the tocopherols and 51% of the oryzanols. During storage of deodorized oil for 7 wk, 34% of the tocopherols and 19% of the oryzanols were lost. The maximum weight gain, peroxide value and anisidine value were obtained from alkali-refined oil during storage. The order of oxidation stability was crude ≥ degummed > bleached = deodorized > alkali-refined oil.  相似文献   
68.
胡波年 《涂料工业》2004,34(11):49-51
米糠油主要由油酸、亚油酸和棕榈酸组成,属半干性油,具有了作为涂料基料的良好理化特性。研究表明,选用米糠油、桐油、环氧树脂和氧化铁红合成的铁红环氧酯防锈底漆,具有无毒、低温固化、防锈能力强等特点。本介绍了底漆的配方、生产工艺,并讨论了影响底漆性能的因素。  相似文献   
69.
In laboratory tests the allelopathic potential ofErica vagans, Calluna vulgaris, andDaboecia cantabrica was determined. Aqueous extracts of flowers ofD. cantabrica and leaves ofC. vulgaris inhibit root and hypocotyl growth of red clover, the former causing 51% inhibition of germination. Intact aerial parts of the Ericaceae here studied drastically reduced the growth of red clover and 100% inhibition of germination was caused by flowers ofD. cantabrica. Inhibition of aqueous extracts remains after Chromatographic separation, and two well-defined inhibition zones may be observed. Hydrosoluble organic compounds (phenol-like compounds) could probably be responsible for the inhibitions detected.  相似文献   
70.
占晓初  石荣国 《中国陶瓷》2007,43(10):74-76
青花红绿彩作为加彩器的一种,比传统的观点早一个朝代,根据明中青花红绿彩盖罐结合最新的窑址考古成果,得出元代的窑炉设计和釉面配方的缺陷,使元代青花红绿彩的生产和存世极少,明官窑中由于斗彩的出现,青花红绿彩在民间一直沿烧。与元代风格相近,只是到了后期风格才大变。  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-23

京公网安备 11010802026262号