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301.
Nb2O5/Co2O3加入量对(Ba,Sr)TiO3基电容器陶瓷介电性能的影响 总被引:1,自引:0,他引:1
研究了Nb2O5/Co2O3加入量[质量分数,Nb/Co(摩尔比)=0.8]不同对(Ba,Sr)TiO3(Barium strontiumtitanate,BST)铁电电容器陶瓷介电性能的影响,得到不同Nb2O5/Co2O3加入量与BST陶瓷性能的关系。借助扫描电镜(SEM)和X射线衍射仪(XRD)研究不同Nb2O5/Co2O3加入量对BST陶瓷显微结构和物相的影响,探讨了Nb2O5/Co2O3加入量对BST陶瓷性能影响机理。结果表明:当Nb2O5/Co2O3加入量为1.0%时,可得到满足Y5V特性、介电常数为3934、介质损耗为2.6%综合性能好的BST陶瓷。Nb2O5/Co2O3加入量对BST陶瓷性能的影响是通过细晶化、压抑展宽居里峰、改善介电常数温度特性、减少介电常数、形成杂相、形成“晶核-晶壳”结构等进行。 相似文献
302.
通过超低温实验直接测量了制备的全铌Josephson结的电压源驱动RCSJ模型的I-V特性曲线。建立了Josephson结在电路仿真软件EWB中的模型,极大的方便了Josephson结及相关电路的仿真研究。利用这一新模型对Josephson结的基本特性进行了较为系统的研究,包括RSJ模型和RCSJ模型的直流驱动I-V特性曲线。 相似文献
303.
V. V. Polubinskii Y. A. Titov N. M. Belyavina V. Ya. Markiv M. S. Slobodyanik V. V. Chumak O. I. Nakonechna 《ChemInform》2014,45(19):no-no
Single phase Ba5KNb5O18 (I) is prepared by solid state reaction of Ba5Nb4O15 and KNbO3 (1370 K, 2 h), while Sr6Nb4SnO18 (II) results from calcination of the coprecipitated metal hydroxycarbonates (1570 K, 2 h). 相似文献
304.
We performed density functional theory calculations using niobium (Nb) as a model system of a conventional superconductor, to correlate the distortion of twin defects with the electron–phonon coupling properties. Calculations using different settings of the Nb elementary cell (relaxed, distorted, super cell with zig‐zag twin defect) showed that only by including real structure elements into the setting, the Eliashberg spectral function representing the electron–phonon coupling properties was derived convincingly. Based on these density functional theory calculations of the electron–phonon cou‐ pling properties of Nb, we suggest a model for a combined superconducting/charge density wave ground state which uses a lattice distortion induced into the crystal by two‐dimensional defects as modulated background potential of the charge density wave phase. The coexistence of both phases is hereby necessary for a fine‐tuning of the Fermi surface within the small local domain of the defect to match the wavelength of the lattice distortion and the Fermi wavelength by pairing fermions to bosons. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
305.
Prof. Carl Redshaw Mark Walton Dr. Lucy Clowes Dr. David L. Hughes Dr. Anna‐Marie Fuller Dr. Yimin Chao Dr. Alex Walton Dr. Victor Sumerin Dr. Pertti Elo Dr. Igor Soshnikov Dr. Weizhen Zhao Prof. Wen‐Hua Sun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(27):8884-8899
The reactions of MCl5 or MOCl3 with imidazole‐based pro‐ligand L1H, 3,5‐tBu2‐2‐OH‐C6H2‐(4,5‐Ph2‐1H‐)imidazole, or oxazole‐based ligand L2H, 3,5‐tBu2‐2‐OH‐C6H2(1H‐phenanthro[9,10‐d])oxazole, following work‐up, afforded octahedral complexes [MX(L1, 2)], where MX=NbCl4 (L1, 1 a ; L2, 2 a ), [NbOCl2(NCMe)] (L1, 1 b ; L2, 2 b ), TaCl4 (L1, 1 c ; L2, 2 c ), or [TaOCl2(NCMe)] (L1, 1 d ). The treatment of α‐diimine ligand L3, (2,6‐iPr2C6H3N?CH)2, with [MCl4(thf)2] (M=Nb, Ta) afforded [MCl4(L3)] (M=Nb, 3 a ; Ta, 3 b ). The reaction of [MCl3(dme)] (dme=1,2‐dimethoxyethane; M=Nb, Ta) with bis(imino)pyridine ligand L4, 2,6‐[2,6‐iPr2C6H3N?(Me)C]2C5H3N, afforded known complexes of the type [MCl3(L4)] (M=Nb, 4 a ; Ta, 4 b ), whereas the reaction of 2‐acetyl‐6‐iminopyridine ligand L5, 2‐[2,6‐iPr2C6H3N?(Me)C]‐6‐Ac‐C5H3N, with the niobium precursor afforded the coupled product [({2‐Ac‐6‐(2,6‐iPr2C6H3N?(Me)C)C5H3N}NbOCl2)2] ( 5 ). The reaction of MCl5 with Schiff‐base pro‐ligands L6H–L10H, 3,5‐(R1)2‐2‐OH‐C6H2CH?N(2‐OR2‐C6H4), (L6H: R1=tBu, R2=Ph; L7H: R1=tBu, R2=Me; L8H: R1=Cl, R2=Ph; L9H: R1=Cl, R2=Me; L10H: R1=Cl, R2=CF3) afforded [MCl4(L6–10)] complexes (M=Nb, 6 a – 10 a ; M=Ta, 6 b – 9 b ). In the case of compound 8 b , the corresponding zwitterion was also synthesised, namely [Ta?Cl5(L8H)+] ? MeCN ( 8 c ). Unexpectedly, the reaction of L7H with TaCl5 at reflux in toluene led to the removal of the methyl group and the formation of trichloride 7 c [TaCl3(L7‐Me)]; conducting the reaction at room temperature led to the formation of the expected methoxy compound ( 7 b ). Upon activation with methylaluminoxane (MAO), these complexes displayed poor activities for the homogeneous polymerisation of ethylene. However, the use of chloroalkylaluminium reagents, such as dimethylaluminium chloride (DMAC) and methylaluminium dichloride (MADC), as co‐catalysts in the presence of the reactivator ethyl trichloroacetate (ETA) generated thermally stable catalysts with, in the case of niobium, catalytic activities that were two orders of magnitude higher than those previously observed. The effects of steric hindrance and electronic configuration on the polymerisation activity of these tantalum and niobium pre‐catalysts were investigated. Spectroscopic studies (1H NMR, 13C NMR and 1H? 1H and 1H? 13C correlations) on the reactions of compounds 4 a / 4 b with either MAO(50) or AlMe3/[CPh3]+[B(C6F5)4]? were consistent with the formation of a diamagnetic cation of the form [L4AlMe2]+ (MAO(50) is the product of the vacuum distillation of commercial MAO at +50 °C and contains only 1 mol % of Al in the form of free AlMe3). In the presence of MAO, this cationic aluminium complex was not capable of initiating the ROMP (ring opening metathesis polymerisation) of norbornene, whereas the 4 a / 4 b systems with MAO(50) were active. A parallel pressure reactor (PPR)‐based homogeneous polymerisation screening by using pre‐catalysts 1 b , 1 c , 2 a , 3 a and 6 a , in combination with MAO, revealed only moderate‐to‐good activities for the homo‐polymerisation of ethylene and the co‐polymerisation of ethylene/1‐hexene. The molecular structures are reported for complexes 1 a – 1 c , 2 b , 5 , 6 a , 6 b, 7 a, 8 a and 8 c . 相似文献
306.
Tomoyuki Kitano Dr. Tetsuya Shishido Dr. Kentaro Teramura Prof. Dr. Tsunehiro Tanaka 《Chemphyschem》2013,14(11):2560-2569
Thermally stable Brønsted acid sites were generated on alumina‐supported niobium oxide (Nb2O5/Al2O3) by calcination at high temperatures, such as 1123 K. The results of structural characterization by using Fourier‐transform infrared (FTIR) spectroscopy, TEM, scanning transmission electron microscopy (STEM), and energy‐dispersive X‐ray (EDX) analysis indicated that the Nb2O5 monolayer domains were highly dispersed over alumina at low Nb2O5 loadings, such as 5 wt %, and no Brønsted acid sites were presents. The coverage of Nb2O5 monolayer domains over Al2O3 increased with increasing Nb2O5 loading and almost‐full coverage was obtained at a loading of 16 wt %. A sharp increase in the number of hydroxy groups, which acted as Brønsted acid sites, was observed at this loading level. The relationship between the acidic properties and the structure of the material suggested that the bridging hydroxy groups (Nb? O(H)? Nb), which were formed at the boundaries between the domains of the Nb2O5 monolayer, acted as thermally stable Brønsted acid sites. 相似文献
307.
Large grain niobium has the potential of simplifying the production sequence and consequently reducing the cost of the superconducting RF cavities for ILC. To investigate the feasibility of fabrication and the possibility to achieve high gradient by large grain cavities, two 1.3GHz cavities were made of China large grain niobium and a series of vertical tests were carried out following several different
surfaces treatment procedures. Two cavities have both reached the high
gradient of more than 43MV/m repeatedly and the maximum accelerating field of 47.9MV/m has been achieved by China large grain niobium. This paper introduces the features of the fabrication and surface treatments on the large grain cavities and presents the preliminary results of the research. 相似文献
308.
Melquizedeque B. Alves Vianney O. Santos jr. Valerio C. D. Soares Paulo A. Z. Suarez Joel C. Rubim 《Journal of Raman spectroscopy : JRS》2008,39(10):1388-1395
Anionic species formed in mixtures of 1‐n‐butyl‐3‐methylimidazolium chloride (BMICl) with different amounts of niobium pentachloride (NbCl5) or zinc dichloride (ZnCl2) were investigated by Raman spectroscopy. In the BMICl and NbCl5 ionic mixtures the presence of the anion NbCl6− was detected for all compositions (molar fraction, X) and a mixture of this anion and the neutral Nb2Cl10 in acid ones. Two different anions were observed for basic mixtures of BMICl and ZnCl2: ZnCl42−(0 < X < 0.35) and Zn2Cl62−(X > 0.3), whereas for acidic ones three species were detected: Zn2Cl62−(X < 0.7), Zn3Cl82−(X > 0.7) and Zn4Cl102−(X > 0.7). It has also been observed that in both cases, the formation of larger anions causes a shift of the C H stretching modes to higher wavenumbers as the result of a decrease in the hydrogen bond between Cl and the hydrogens from the cation. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
309.
铁电薄膜由于其优异物理性能,而被广泛应用于微电子、光电子、微机电领域。在铁电薄膜理论研究方面,热力学理论可以有效地预测铁电薄膜的相结构、极化特性和机电性能等,且已在(001)取向铁电薄膜的研究中取得了较好的应用,而对于(111)取向铁电薄膜的研究报道非常少。因此,本文通过对序参量坐标转换的方法,构建了(111)取向薄膜的热力学势能函数及其机电性能计算方法。基于此,研究了(111)取向0.7PMN-0.3PT铁电薄膜的相结构及其机电性能。研究结果表明,(111)取向0.7PMN-0.3PT铁电薄膜的相结构主要存在沿晶轴方向三个极化可互换的对称相:顺电相PE、菱方相R和单斜相MA(或MB)。在应变和外电场的调控下,(111)取向0.7PMN-0.3PT薄膜展现出优良的机电性能,在R和MA相变点处,介电常数ε11、ε22、ε33和面外压电系数d33取得了极大值。在外电场E3分别为0、50 kV/cm、100 kV/cm和200 kV/cm时,面外介电常数ε33的峰值分别为4 382、2 646、2 102和1 600,面外压电系数d33的峰值分别为303.8 pm/V、241.9 pm/V、219.7 pm/V和195.1 pm/V。应变和外电场能够较好地调控薄膜的机电耦合性能,可为优异机电耦合性能的器件制备提供参考。 相似文献
310.
高频红外吸收法测定钽粉、铌粉和碳化钽中的碳 总被引:2,自引:0,他引:2
用HCS-140型高频红外碳硫分析仪测定钽粉、铌粉、碳化钽中的碳,进行了助熔剂、称样量、氧气流量试验,在不需测硫的情况下,采用铜和钨作助熔剂、称样量为0.5g、氧气流量为2L/min时,测定结果满足分析要求。 相似文献