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   1068篇
  免费   151篇
  国内免费   165篇
化学   950篇
晶体学   21篇
力学   22篇
综合类   38篇
数学   23篇
物理学   330篇
  2024年   3篇
  2023年   11篇
  2022年   57篇
  2021年   51篇
  2020年   51篇
  2019年   30篇
  2018年   39篇
  2017年   45篇
  2016年   52篇
  2015年   43篇
  2014年   64篇
  2013年   68篇
  2012年   79篇
  2011年   59篇
  2010年   58篇
  2009年   59篇
  2008年   62篇
  2007年   77篇
  2006年   63篇
  2005年   67篇
  2004年   49篇
  2003年   49篇
  2002年   38篇
  2001年   40篇
  2000年   33篇
  1999年   19篇
  1998年   17篇
  1997年   10篇
  1996年   12篇
  1995年   11篇
  1994年   7篇
  1993年   14篇
  1992年   7篇
  1991年   8篇
  1990年   8篇
  1989年   10篇
  1988年   5篇
  1987年   1篇
  1985年   1篇
  1984年   2篇
  1983年   1篇
  1982年   1篇
  1981年   2篇
  1959年   1篇
排序方式: 共有1384条查询结果,搜索用时 15 毫秒
211.
New lanthanide metal-organic framework(MOF) nano/microrods, [C4mim]Cl-Eu-MOF, [C8mim]Cl-Eu- MOF and [C12mim]Cl-Eu-MOF, were conveniently synthesized via an ionic liquid-assisted hydrothermal method and characterized by means of powder X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), thermogravimetric analysis(TG) and transmission electron microscopy(TEM). The obtained nano/microrods with low surface areas were efficient for the removal of Congo red(CR) from aqueous solutions. Under the optimum conditions, [C4mim]Cl-Eu-MOF with a specific surface area of 5.1 m2/g exhibited an ultrahigh adsorption capacity of 2606 mg/g toward CR. Notably, the adsorption efficiency of [C4mim]Cl-Eu-MOF for CR via nano/microscale stacking can be directly demonstrated by TEM. In-depth understanding of CR removal by [C4mim]Cl-Eu-MOF nano/microrods was also supported by FTIR, Raman spectroscopy and zeta potential analyses.  相似文献   
212.
Diketopyrrolo[3,4-c]pyrroles (DPP) are high-performance organic optoelectronic materials. They have applications in solar cells, fluorescent probes, bioimaging, photodynamic/photothermal therapy, and in many other areas. This article reports a convenient two-step synthesis of various DPP dyes from Pigment Red 254, an inexpensive commercial pigment. The synthesis includes a Suzuki–Miyaura cross-coupling reaction of a bis(4-chlorophenyl)DPP derivative with aryl and hetaryl boronic acids under mild reaction conditions. The new dyes show large Stokes shifts and high fluorescence quantum yields, important features for their potential use in technical and biological applications.  相似文献   
213.
文雯  王博  李璐  于军胜  蒋亚东 《物理学报》2009,58(11):8014-8020
研究了基于红色荧光染料3-(dicyanomethylene)-5, 5-dimethyl-1-(4-dimethylamino-styryl) cyclohexene(DCDDC)的白色有机电致发光器件的性能,分别制备了基于DCDDC超薄层和DCDDC掺杂主体材料的两种器件结构: 1)indium-tin oxide(ITO)/N, N′-diphenyl-N, N′-bis(1-naphthyl-pheny1)-1, 1′-biphenyl-4, 关键词: 有机电致发光器件 白色发光 红色荧光染料 掺杂  相似文献   
214.
吖啶红-SLS体系共振瑞利散射法测定蛋白质   总被引:7,自引:0,他引:7  
研究了吖啶红染料与蛋白质的结合反应。在十二烷基磺酸钠存在下及pH2.90的柠檬酸NaOH介质中,蛋白质与吖啶红形成复合物,使最大波长392nm的共振光散射光谱得到加强,根据其共振光散射的增强程度,可用于蛋白质的定量测定。十二烷基磺酸钠的加入,使灵敏度提高11倍,牛血清白蛋白、γ球蛋白的线性范围分别为0.03~0.7mg/L、0.05~1.3mg/L,检出限分别为6.4μg/L、10.8μg/L。用于人血清、牛奶、豆浆、尿液中总蛋白质的测定,结果与经典的考马斯亮蓝G 250法一致。  相似文献   
215.
以二醋酸纤维素做基质采用包埋法将刚果红固定, 制备成一种平均厚度为5μm的光化学pH敏感膜(CCM)。利用紫外可见光谱仪探讨了pH响应性能。结果表明, 该膜对pH在2. 50 ~4. 76范围内的变化呈线性响应,其热力学常数pKa为3. 61±0. 03,响应时间在10s以内,同时也考察了该膜的重现性、稳定性以及电解质对该膜的光吸收性质的影响。  相似文献   
216.
溶剂对光致变色材料-乙基红的光学特性影响   总被引:2,自引:0,他引:2  
陈宽  祁胜文  杨秀芹  许棠  张春平  田建国 《光子学报》2005,34(10):1485-1489
研究了溶剂性质对光致变色材料乙基红光学性质的影响.用吸收谱测定了乙基红染料在不同溶剂中的溶剂化位移.对相同浓度多种乙基红溶液进行了Z-scan测量,测量了不同乙基红溶液的光限幅效应,并讨论了其与溶剂之间的关系.随极性增加,吸收谱蓝移,可以通过选择不同溶剂,改变非线性材料的应用窗口.实验结果表明,在连续光照射下,乙基红溶液的非线性折射主要由热效应引起,非线性折射系数n2受溶剂的热学性质影响较大.此外,Z-scan结果中的非线性吸收为饱和吸收.至于光限幅效应,主要受热效应影响,但亦可由吸收谱预测出在某波长处的动态范围.得出的结论有助于偶氮染料作为非线性材料的应用.  相似文献   
217.
钒(Ⅴ)-茜素S-溴酸钠体系极谱络合吸附催化波的研究   总被引:4,自引:0,他引:4  
王月宣  李益恒  阮湘元 《分析化学》2004,32(9):1206-1208
在六次甲基四胺 HCl缓冲溶液 (pH 5 .5 )中 ,钒 (Ⅴ ) 茜素S 溴酸钠体系产生一灵敏的吸附平行催化波 ,峰电位在 -0 .64V(vs.SCE)。二次导数峰高与钒 (Ⅴ )浓度在 1 .0× 1 0 -9~ 2 .0× 1 0 -6mol/L范围内呈线性关系 ;检出限为 5 .0× 1 0 -10 mol/L。研究了电极反应机理 ,方法应用于水样中钒的测定 ,结果满意。  相似文献   
218.
Ru(bpy)32+聚电解质光致发光电致发光性质   总被引:1,自引:0,他引:1  
以Ru(bpy)3^2 作为发光材料研制聚合物电致发光器件,分别以水溶性聚乙烯基氯化铵(PAA)和聚苯乙烯基磺酸钠(PSSTS)作为母体材料,研究了聚阴阳离子对器件性质的影响。通过对器件结构、母体浓度、掺杂浓度进行优选,得到结构为ITO/PVK/Ru:PAA/LiF/Al的器件。这一器件开启电压为3.5V,效率为1.1lm/W。  相似文献   
219.
The redox dye Neutral red (NR), adsorbed and electropolymerized at a roughened gold electrode, has been studied by Raman spectroscopy at λex of 676.4 nm in an electrochemical cell. Spectral bands have been assigned based on density functional theory (DFT) calculations. The number and position of the bands, as well as their intensity depend on electrode potential, allowing one to discern different redox forms of NR or its polymer. The observed changes in band positions and intensities have been analyzed. Electrooxidation of hydroquinone and ascorbic acid at a gold electrode modified with adsorbed or electropolymerized layer of NR has been studied with in situ Raman spectroelectrochemical technique. During electrooxidation of solution species, NR layer contains both oxidized and reduced forms of this modifier. It has been shown that the relative content of a reduced form of NR at electrode surface increases with increasing concentration of any of oxidizable species used. It has been concluded that anodic oxidation of ascorbic acid or hydroquinone at NR or polyNR modified electrode proceeds within the modifier layer rather than at a modifier/electrolyte interface. In this respect, electrooxidation follows a redox mechanism.  相似文献   
220.
H. Chen  J. Zhao 《Adsorption》2009,15(4):381-389
The organo-attapulgite was prepared using hexadecyltrimethylammonium bromide (HTMAB) with equation equivalent ratio of HTMAB to CEC of attapulgite added and then used as adsorbent for the removal of Congo red (CR) anionic dye from aqueous solution. Adsorbent characterizations were investigated using infrared spectroscopy and X-ray diffraction. The effects of contact time, temperature, pH and initial dye concentration on organo-attapulgite adsorption for CR were investigated. The results show that the amount adsorbed of CR on the organo-attapulgite increase with increasing dye concentration, temperature, and by decreasing pH. The adsorption kinetics was studied with the pseudo-first-order, pseudo-second-order and intraparticle diffusion models, and the rate constants were evaluated. It was found that the adsorption mechanisms in the dye/organo-attapulgite system follow pseudo-second-order kinetics with a significant contribution of film diffusion. Equilibrium data fitted perfectly with Langmuir isotherm model compared to Freundlich isotherm model, and the maximum adsorption capacity was 189.39 mg g−1 for the adsorbent. Kinetic and desorption studies both suggest that chemisorption should be the major mode of CR removal by the organo-attapulgite. The results indicate that HTMAB-modified attapulgite could be employed as low-cost material for the removal of Congo red anionic dye from wastewater.  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