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   10490篇
  免费   2029篇
  国内免费   279篇
电工技术   75篇
综合类   253篇
化学工业   4266篇
金属工艺   474篇
机械仪表   245篇
建筑科学   72篇
矿业工程   40篇
能源动力   721篇
轻工业   544篇
水利工程   11篇
石油天然气   126篇
武器工业   7篇
无线电   1299篇
一般工业技术   4314篇
冶金工业   155篇
原子能技术   56篇
自动化技术   140篇
  2024年   53篇
  2023年   395篇
  2022年   300篇
  2021年   716篇
  2020年   692篇
  2019年   652篇
  2018年   713篇
  2017年   721篇
  2016年   723篇
  2015年   711篇
  2014年   862篇
  2013年   1013篇
  2012年   770篇
  2011年   922篇
  2010年   604篇
  2009年   674篇
  2008年   593篇
  2007年   439篇
  2006年   392篇
  2005年   282篇
  2004年   140篇
  2003年   120篇
  2002年   73篇
  2001年   59篇
  2000年   58篇
  1999年   37篇
  1998年   17篇
  1997年   13篇
  1996年   8篇
  1995年   11篇
  1994年   7篇
  1993年   9篇
  1992年   3篇
  1991年   2篇
  1990年   3篇
  1989年   4篇
  1988年   1篇
  1986年   1篇
  1985年   1篇
  1951年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Pyrolysis in air at 800°C of [{NP(OC12H10)}0.6{NP(OC6H4PPh2·(π-CH3C5H4)−Mn(CO)2)2}0.4] n (1) in the solid state affords product 2 containing nanoclusters of Mn2P2O7 with sizes ranging from 50 to 90 nm and averaging about 74 nm. The egg-shape of the unpyrolyzed organometallic polymer is retained but with increased particle size after pyrolysis. The pyrolytic material shows near-infrared photoluminescence attributed to the emission of tetrahedral Mn2+ embedded in a matrix of Mn2P2O7. The solid-state pyrolysis of organometallic derivatives of polyphosphazenes may be a useful and general route to nano-structured Mn2P2O7. An erratum to this article can be found at  相似文献   
92.
纳米粒子增韧聚氯乙烯研究新进展   总被引:1,自引:0,他引:1  
本文主要综述了纳米粒子在聚氯乙烯增韧改性中的应用研究状况.现有的结果表明,纳米复合技术在聚氯乙烯增韧改性中具有同时提高材料韧性和强度的特点.因此,纳米复合技术将成为聚氯乙烯增韧改性的一种重要方法,并得到广泛应用.  相似文献   
93.
Uniform polyaniline (PANI) nanoparticles with typical sizes of about 50 nm were electropolymerized on indium tin oxide surfaces in the presence of Co2+, Ni2+, Cu2+, or Zn2+. According to shaping theory, we first suggest the reason forming PANI spherical particles. Their conductivity, UV‐vis spectra, FTIR spectra, X‐ray diffraction, and thermogravimetric analysis were investigated. The conductivities and crystallinity of PANI doped with these ions are higher than those of PANI doped with HCl (PANI/HCl). Both UV‐vis absorption spectra and FTIR spectra indicate the interactions between Co2+, Ni2+, Cu2+, or Zn2+ and PANI chains. TG analysis also shows that the thermal stability of PANI doped by Co2+, Ni2+, Cu2+, or Zn2+ is lower than that of PANI/HCl. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007  相似文献   
94.
Conducting polydiphenylamine was used to encapsulate silica nanoparticles through the oxidative polymerization of diphenylamine in the presence of ultrasonic irradiation. The polymerization was performed in the presence of sodium lauryl sulfate as a surfactant. Experiments performed in the absence of ultrasound clearly demonstrated that the application of ultrasonication played multiple roles in the preparation of a composite of polydiphenylamine with silica nanoparticles. Ultrasonication dispersed the silica nanoparticles, converted sodium lauryl sulfate to lauryl alcohol, and augmented the dispersion of the silica‐nanoparticle/polydiphenylamine composite in an organic medium. Silica‐nanoparticle/polydiphenylamine composites were also prepared in the absence of ultrasound and/or sodium lauryl sulfate. The silica‐nanoparticle/polydiphenylamine composites were characterized with Fourier trans form infrared spectroscopy, ultraviolet–visible/near‐infrared spectroscopy, and thermogravimetric analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3912–3918, 2006  相似文献   
95.
热处理条件对硅酸盐玻璃中原位形成银纳米颗粒的影响   总被引:3,自引:2,他引:3  
杨修春  杜天伦  李志会  黄文旵 《硅酸盐学报》2006,34(12):1481-1484,1490
用离子交换结合热处理法制备银(Ag)纳米颗粒-玻璃复合材料.用透射电镜、高分辨透射电子显微镜、Ruthefford背散射谱和紫外-可见光吸收光谱研究了热处理条件对玻璃中原位形成Ag纳米颗粒的影响.结果显示:随着热处理温度升高,玻璃表面的Ag原子逐渐向玻璃内部扩散,其表面摩尔浓度逐渐降低.提高热处理温度和延长热处理时间都有利于提高玻璃中Ag纳米颗粒的体积分数.空气中,高温热处理高掺Ag量的白玻璃样品时发生二次成核,因此,Ag纳米颗粒尺寸呈双峰分布.Ag纳米颗粒尺寸的双峰分布导致其等离子体共振吸收峰出现双峰.在氢气气氛中,在250℃热处理2min,即可在玻璃中形成大量Ag纳米颗粒,颗粒尺寸小于空气中高温热处理样品的尺寸,从而引起表面等离子体共振吸收峰发生蓝移.  相似文献   
96.
草酸镁分解法制备纳米氧化镁   总被引:1,自引:0,他引:1  
凌程凤  高雪艳  杨姣  宗俊 《无机盐工业》2005,37(9):29-30,34
以草酸和氯化镁为原料,采用固液法制备了纳米级氧化镁粉体。优化了试验条件,并用TEM和XRD对纳米氧化镁的粒子结构和形貌进行了研究。结果表明,在600℃焙烧,得到的纳米氧化镁粒度分布均匀,平均粒径为15nm。并对固液法生成纳米氧化镁的机理进行了初步探讨。  相似文献   
97.
Platinum nanoparticles (n-Pt), over-grafted with 2-thiophenecarbonyl chloride are assembled on gold electrodes, by the Langmuir Blodgett (LB) technique using behenic acid (BHA) as promoting agent. These layers are electrochemically active without any preliminary activation. The [Fe(CN)6]3−/4− redox couple was used as electrochemical probe. This paper reports on the influence of the number of deposited LB layers, and the n-Pt density on the electrochemical response. n-Pt density was modified by the change of the “BHA/n-Pt” ratio. Cyclic voltammograms of “[Fe(CN)6]3−/4−” were observed whatever the coating conditions. As soon as the first layer was deposited the electrochemical response was associated to the n-Pt coverage, its response slightly increased up to a steady state for five or seven layers. As expected, the increase of the Pt density favored the increase of the current density. XPS analysis performed before and after electrochemical cycling showed that 4-mercaptoaniline capped platinum nanoparticles, and their over grafting were chemically and electrochemically stable. Analysis of influence of the number or the n-Pt density of the layers showed that the electrochemically active part of LB electrodes was provided by the last layer plus a part of the underlying one.  相似文献   
98.
Zinc oxide (ZnO) nanoparticles assembled in one dimension to give rod‐shaped morphology were synthesized. The effect of these ZnO nanoparticles (average particle size ~ 50 nm) as the curing agent for carboxylated nitrile rubber was studied with special attention to cure characteristics, mechanical properties, dynamic mechanical properties, and swelling. These results were compared with those of the conventional rubber grade ZnO. The study confirmed that the ZnO nanoparticles gave a better state of cure and higher maximum torque with a marginal decrease in optimum cure time and scorch time. The mechanical properties also showed an improvement. There was an increase in tensile strength by ~ 120%, elongation at break by ~ 20%, and modulus at 300% elongation by ~ 30% for the vulcanizate cured with ZnO nanoparticles, as compared with the one containing rubber grade ZnO. Dynamic mechanical analysis revealed that the vulcanizates exhibited two transitions—one occurring at lower temperature due to the Tg of the polymer, while the second at higher temperature corresponding to the hard phase arising due to the ionic structures. The second transition showed a peak broadening because of an increase in the points of interaction of ZnO nanoparticles with the matrix. The tan δ peak showed a shift towards higher Tg in the case of ZnO nanoparticle‐cured vulcanizate, indicating higher crosslinking density. This was further confirmed by volume fraction of rubber in the swollen gel and infrared spectroscopic studies. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007  相似文献   
99.
熊杰  廖其龙  宁海霞 《精细化工》2007,24(10):952-955,960
用NiSO4.6H2O为原料,N2H4.H2O为还原剂,十二烷基磺酸钠(SDS)为表面活性剂,用NaOH调节反应pH,合成了纳米Ni粉。采用XRD、SEM及FTIR等分析测试方法对所制得的粉体进行了表征。研究结果表明:在反应温度为80℃,反应时间10~25 min,Ni2+浓度为0.75 mol/L,pH=11,n(N2H4)∶n(Ni2+)=(2~3)∶1时,能得到平均粒径75~200 nm的球形纳米Ni粉。  相似文献   
100.
中和法和水热法制备粉体是目前常用的制备超细粉体材料的方法。通过对这两种方法进行制备铁氧体粉末的对比实验研究发现,中和法和水热法制得的粉体在性能上存在一些差异。水热法制得的粉体比中和法制得的粉体具有更好的分散性能、更窄、更细小的粒径范围和更大的比表面积。  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