全文获取类型
收费全文 | 2326篇 |
免费 | 295篇 |
国内免费 | 461篇 |
学科分类
数理化 | 3082篇 |
出版年
2024年 | 10篇 |
2023年 | 38篇 |
2022年 | 67篇 |
2021年 | 54篇 |
2020年 | 119篇 |
2019年 | 115篇 |
2018年 | 107篇 |
2017年 | 108篇 |
2016年 | 107篇 |
2015年 | 94篇 |
2014年 | 86篇 |
2013年 | 142篇 |
2012年 | 156篇 |
2011年 | 153篇 |
2010年 | 109篇 |
2009年 | 161篇 |
2008年 | 156篇 |
2007年 | 191篇 |
2006年 | 142篇 |
2005年 | 99篇 |
2004年 | 95篇 |
2003年 | 91篇 |
2002年 | 108篇 |
2001年 | 90篇 |
2000年 | 80篇 |
1999年 | 57篇 |
1998年 | 62篇 |
1997年 | 53篇 |
1996年 | 47篇 |
1995年 | 50篇 |
1994年 | 25篇 |
1993年 | 16篇 |
1992年 | 19篇 |
1991年 | 16篇 |
1990年 | 13篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 5篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 1篇 |
排序方式: 共有3082条查询结果,搜索用时 15 毫秒
61.
62.
Hui Xu Dr. Shengbo Zhang Xinyuan Zhang Min Xu Dr. Miaomiao Han Prof. Li Rong Zheng Prof. Yunxia Zhang Prof. Guozhong Wang Prof. Haimin Zhang Prof. Huijun Zhao 《Angewandte Chemie (International ed. in English)》2023,62(52):e202314414
The integration of highly active single atoms (SAs) and atom clusters (ACs) into an electrocatalyst is critically important for high-efficiency two-electron oxygen reduction reaction (2e− ORR) to hydrogen peroxide (H2O2). Here we report a tandem impregnation-pyrolysis-etching strategy to fabricate the oxygen-coordinated Fe SAs and ACs anchored on bacterial cellulose-derived carbon (BCC) (FeSAs/ACs-BCC). As the electrocatalyst, FeSAs/ACs-BCC exhibits superior electrocatalytic activity and selectivity toward 2e− ORR, affording an onset potential of 0.78 V (vs. RHE) and a high H2O2 selectivity of 96.5 % in 0.1 M KOH. In a flow cell reactor, the FeSAs/ACs-BCC also achieves high-efficiency H2O2 production with a yield rate of 12.51±0.18 mol gcat−1 h−1 and a faradaic efficiency of 89.4 %±1.3 % at 150 mA cm−2. Additionally, the feasibility of coupling the produced H2O2 and electro-Fenton process for the valorization of ethylene glycol was explored in detail. The theoretical calculations uncover that the oxygen-coordinated Fe SAs effectively regulate the electronic structure of Fe ACs which are the 2e− ORR active sites, resulting in the optimal binding strength of *OOH intermediate for high-efficiency H2O2 production. 相似文献
63.
Fe3+-TiO2/SiO2光催化降解罗丹明B的研究 总被引:25,自引:0,他引:25
以硅胶为载体,采用溶胶-凝胶法制备了不同掺杂量的Fe3+-TiO2/SiO2光催化剂,并采用SEM,Raman和DRS等手段对其进行了分析和表征.以氙灯为光源,通过对可溶性染料罗丹明B的降解反应,考察了Fe3+-TiO2/SiO2催化剂的光催化活性,探讨了光催化反应中溶液pH值和起始浓度对催化反应的影响. 相似文献
64.
65.
Mateusz Kuczyski Mateusz uba Tomasz Mikoajczyk Bogusaw Pieroyski Agnieszka Jasiecka-Mikoajczyk Lech Smoczyski Piotr Soowiej Pawe Wojtacha 《Molecules (Basel, Switzerland)》2021,26(15)
Traditional wastewater purification processes are based on a combination of physical, chemical, and biological methods; however, typical electrochemical techniques for removing pollutants require large amounts of electrical energy. In this study, we report on a process of wastewater purification, through continuous anodic dissolution of iron anode for aerated Cu/Fe galvanic cell in synthetic Na2SO4 wastewater solution. Electrochemical experiments were conducted by means of a laboratory size electrolyzer, where electrocoagulation along with electrooxidation phenomena were examined for wastewater containing Acid Mixture dye. The above was visualized through the employment of electrochemical (cyclic voltammetry and ac impedance spectroscopy techniques) along with instrumental spectroscopy analyses. 相似文献
66.
The quenching of the fluorescence of three anthropogenic fulvic acids (FA) provoked by Cu(II) (pH 6.0), Fe(III) (pH 4.0) and UO22+ (pH 3.5), was analyzed by a non-linear method and by Stern-Volmer plots. The FA samples were extracted from composted sewage sludges (csFA), composted municipal wastes (mwFA) and composted livestock wastes (lsFA). Synchronous-scan fluorescence (SyF) spectra were collected as a function of metal ion concentration. Spectral data were treated by a self-modeling mixture analysis method (SIMPLISMA) to detect the SyF spectral band with the strongest quenching and to calculate the corresponding quenching profile. The analysis of these profiles by a non-linear method allowed the estimation of conditional stability constants (K) and of the percentage of non-complexing fluorophores. The same quantitative information was obtained by the modified Stern-Volmer equation taking into account the existence of fluorophores that do not participate in the complexation. Good agreement was found between the results of the two procedures. The log K calculated by the non-linear method were (standard deviation in parenthesis): csFA, Cu(II), 4.22 (5); Fe(III), 5.0 (1); UO22+, 5.2 (2); mwFA, Cu(II), 4.21 (3); Fe(III), 5.6 (2); UO22+, 4.7 (3); lsFA, Cu(II), 4.51 (8); Fe(III), 5.5 (2); UO22+, 3.6 (2). 相似文献
67.
《Surface and interface analysis : SIA》2005,37(5):495-498
The oxidation of iron (Fe) by water (D2O) vapour at low pressures and room temperature was investigated using time‐of‐flight (ToF) SIMS. The results supported those found previously using XPS and the QUASES? program in that a duplex oxide structure was found containing a thin outer surface hydroxide (Fe(OD)2) layer over an inner oxide (FeO) layer. The extraordinary depth resolution of the ToF‐SIMS profiles assisted in identifying the two phases; this resolution was achieved by compensation for surface roughness. A substantial concentration of deuterium was found in the subsurface oxide layer. This observation confirmed previous assessments that the formation of FeO was from the reaction of Fe(OD)2 with outward‐diffusing Fe, leaving deuterium as a reaction product. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
68.
采用静电自组装方法,分两步合成Fe(OH)3/GO前驱体(GO:氧化石墨烯),再通过水热反应和600°C高纯氮气气氛下煅烧,获得了Fe3O4/石墨烯复合材料.通过X射线衍射(XRD)、扫描电镜(SEM)、高分辨透射电镜(HRTEM)、拉曼(Raman)光谱等多种分析,发现该复合材料具有三维多孔石墨烯网络结构.把合成的这种Fe3O4/石墨烯复合材料作为锂离子电池负极材料,电化学测试结果表明其具有优良的电化学性能:首次放电容量为1390 mAh·g-1,50次循环后容量为819 mAh·g-1.通过对比实验表明,三维石墨烯网络结构的形成对复合材料的电化学循环稳定性起着关键作用. 相似文献
69.
首先通过传统的多元醇方法合成了表面光滑的银纳米线,然后利用Fe(NO3)3作为刻蚀剂在室温条件下对合成的银纳米线进行刻蚀得到了具有波纹状表面的银纳米线. 通过扫描电镜(SEM)分析表明:银纳米线的表面粗糙程度随着刻蚀剂量的增加而增加,但过量的刻蚀剂又会导致纳米线的断裂甚至形成球状颗粒;当刻蚀剂的量为100 μL时,获得了波纹状表面的银纳米线. 对结晶紫(CV)的表面增强拉曼光谱(SERS)结果表明,这种波纹状银纳米线的拉曼信号强度比表面光滑的银纳米线提高了约5倍,其检测限可低至10-10 mol/L. 此外,这种优势还可以延伸到敏感性检测10-9 mol/L的对巯基吡啶(4-Mpy)分子,可以作为一种普适、有效的SERS活性基底. 相似文献
70.
Nurul Hidayah Abdullah Kamyar Shameli Ezzat Chan Abdullah Luqman Chuah Abdullah 《中国化学快报》2017,28(7):1590-1596
A facile and green synthetic approach for fabrication of starch-stabilized magnetite nanoparticles was implemented at moderate temperature. This synthesis involved the use of iron salts, potato starch,sodium hydroxide and deionized water as iron precursors, stabilizer, reducing agent and solvent respectively. The nanoparticles(NPs) were characterized by UV-vis, PXRD, HR-TEM, FESEM, EDX, VSM and FT-IR spectroscopy. The ultrasonic assisted co-precipitation technique provides well formation of highly distributed starch/Fe_3O_4-NPs. Based on UV–vis analysis, the sample showed the characteristic of surface plasmon resonance in the presence of Fe_3O_4-NPs. The PXRD pattern depicted the characteristic of the cubic lattice structure of Fe_3O_4-NPs. HR-TEM analysis showed the good dispersion of NPs with a mean diameter and standard deviation of 10.68 4.207 nm. The d spacing measured from the lattice images were found to be around 0.30 nm and 0.52 nm attributed to the Fe3O4 and starch, respectively. FESEM analysis confirmed the formation of spherical starch/Fe_3O_4-NPs with the emission of elements of C, O and Fe by EDX analysis. The magnetic properties illustrated by VSM analysis indicated that the as synthesized sample has a saturation magnetization and coercivity of 5.30 emu/g and 22.898 G respectively.Additionally, the FTIR analysis confirmed the binding of starch with Fe_3O_4-NPs. This method was cost effective, facile and eco-friendly alternative for preparation of NPs. 相似文献