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181.
Raif Kurtaran Cengiz Arici Kaan C. Emregül Diner Ülkü Orhan Atakol Mustafa Tatekin 《无机化学与普通化学杂志》2003,629(9):1617-1621
A homo‐dinuclear NiII complex was prepared from 2, 6‐bis(3, 5‐dimethylpyrazolyl)pyridine (Me4‐bpp) and azide ions in nonaqueous media. It was characterized by single crystal X‐ray structural analysis, IR spectroscopy, and elemental analysis. In addition, the electrochemical properties of the compound were determined with cyclic voltammetry in DMF. The title compound crystallizes in the P21/n monoclinic space group, with unit cell parameters a = 8.978(1), b = 12.459(1), c = 17.764(1) Å, ß =100.603(3)°, V = 1953.0(3) Å3, Z = 2. The Ni2+ ion has a distorted octahedral environment involving three nitrogen atoms of the Me4‐bpp ligand, two nitrogen atoms from the bridged azide group, and one nitrogen atom from the terminal azide group. The Ni···Ni distance is 3.273(5) Å. 相似文献
182.
On the Criteria of Instability for Electrochemical Systems 总被引:7,自引:0,他引:7
Both cyclic-voltammetry-based and impedance-based experimental criteria that have been developed recently for the oscillatory electrochemical systems are critically appraised with two typical categories of oscillators.Consistent conclusions can be drawn by the two criteria for the category of oscillators that involve the coupling of charge transfer mainly with surface steps(e.g.ad-and desorption)such as in the electrooxidation of C1 organic molecules.Whereas,impedance-based criterion is not applicable to the category of oscillators that involve the coupling of charge transfer mainly with mass transfer(e.g.diffusion and convection) such as in the Fe(CN)6^3- reduction accompanying periodic hydrogen evolution.The reason is that the negative impedance cannot include the feedback information of convection mass transfer induced by the hydrogen evolution.However,both positive and negative nonlinear feedbacks,i.e., the diffusion-limited depletion and convection-enhanced replenishment of the Fe(CN)6^3- surface concentration,that coexist between the bistability,i.e.,Fe(CN)6^3- reduction with and without hydrogen evolution at lower and higher potential sides respectively,are all reflected in the crossed cyclic voltammogram(CCV).It can be concluded that the voltammetry-based criterion(in time domain)is more intuitive,less time-consuming and has a wider range of applications than the impedancebased one (in frequency domain). 相似文献
183.
0引言为解决目前日益严重的汽车尾气排放对城市空气造成污染问题,作为绿色能源的锂离子电池已成为动力电池的首选对象。国际上,高容量、大功率锂离子电池早于1995年已开始研制。1996年,我国天津电源研究所也进行了大容量锂离子蓄电池及电池组的探索[1]。目前,锂离子电池的正极材料是制约其大规模推广应用的关键。现研究的正极材料主要包括具有层状结构的LiCoO2,LiN iO2和LiM nO2及具有尖晶石结构的LiM n2O4等。其中LiC oO2作为目前唯一已经商业化的正极材料具有理论容量高、可循环性能好等优点,但因Co资源的相对缺乏导致其价格高昂。… 相似文献
184.
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186.
有限群G的子群H称为G的BNA子群,若对任意的x∈G有H^(x)=H或x∈.若有限群G的所有素数阶和4阶循环子群都是G的BNA子群,则称G为CBNA群.本文主要刻画CBNA群的结构,并且给出所有真子群都是CBNA群的完全分类. 相似文献
187.
K. U. Kirst F. Kremer T. Pakula J. Hollingshurst 《Colloid and polymer science》1994,272(11):1420-1429
Dielectric spectroscopy (10–1 Hz to 107 Hz) has been employed to study the molecular dynamics of a series of cyclic and linear polydimethylsiloxanes (PDMS) of various molecular weights ranging from 300 to 10 000 g/mol in the temperature range above the glass transition (from 130 K to 190 K). The observed -relaxation depends strongly on both molecular weight and structure of the samples. For linear PDMS oligomers, the -relaxation shifts towards lower temperatures with decreasing molecular weight in good accordance with the Fox-Flory-model. Cyclic PDMS reveals a qualitatively different molecular weight dependence: for a given temperature the -relaxation time increases with decreasing ring length, but has a maximum for small oligomers (degree of polymerizationn6). The shape of relaxation curves and, with it, the relaxation time distribution is independent from length and architecture of the chains The observed experimental findings are in qualitative agreement with dynamic Monte-Carlo simulations.Dedicated to Prof. E.W. Fischer on the occasion of his 65th birthday Fast macht' das WLF ihn krank, jetzt raucht er wieder, Gott sei Dank! (frei nach Wilhelm Busch) 相似文献
188.
L. A. Shundrin I. G. Irtegova A. D. Rogachev V. A. Reznikov 《Russian Chemical Bulletin》2005,54(5):1178-1184
The electrochemical reduction of 3,3′-bi(2-R-5,5-dimethyl-4-oxopyrrolinylidene) 1,1′-dioxides (R = CF3, Me, Ph, But), which are cyclic dinitrons with conjugated C=C bond, in acetonitrile is an EE process producing stable radical anions and
dianions, whereas the electrochemical oxidation is an EEC (R = Me, Ph) or EE process (R = But) with formation of radical cations (except for the case of R = CF3) and dications (R = But) stable under standard conditions. Radical cations of the dioxides with R = Me, Ph, and But and radical anions of the whole series of the compounds studied, including R = CF3, were characterized by ESR spectroscopy combined with electrochemical measurements and quantum-chemical calculations. The
electrochemical behavior of the But-substituted dinitron is unique: the EE processes in the region of negative and positive potentials with formation of the
dianion, radical anion, radical cation, and dication stable at T = 298 K were observed for the first time within one cycle of potential sweep in the CV curve measured in MeCN.
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Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1148–1154, May, 2005. 相似文献
189.
在金属和石墨基底电极上用恒电位沉积法制备出普鲁士蓝(PB)薄膜,研究了影响膜生长的多种因素;观察到PB膜的电化学活性。用红外光谱及电子能谱对膜的化学组成作了分析,结果表明,最初制备的膜为不溶性PB:Fe_4[Fe(CN)_6]_3,在含K~+的电解质溶液中经电化学反应后膜部分转变为可溶性PB:KFeFe(CN)_6,由此确定了PB膜的电化学反应式。 相似文献
190.
Rigol C Olea-Azar C Mendizábal F Otero L Gambino D González M Cerecetto H 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(13-14):2933-2938
Cyclic voltammetry and electron spin resonance (ESR) techniques were used in the investigation of several potential antiprotozoal thiosemicarbazones nitrofurane derivatives. A self-protonation process involving the protonation of the nitro group due to the presence of an acidic proton in the thiosemicarbazone moiety was observed in the first step of a CEE(rev) reduction mechanism of these derivatives. ESR spectra of the free radicals obtained by electrolytic reduction were characterized and analyzed. AM1 methodology was used to obtain the optimized geometries and UB3LYP calculations were performed to obtain the theoretical hyperfine coupling constants. The theoretical study exhibited an unusual assignment of the spin densities showing a free radical centered in the thiosemicarbazone moiety rather than the nitro which are in agreement with the experimental hyperfine pattern. 相似文献