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61.
Evdokimov IN Efimov YO Losev AP Novikov MA 《Langmuir : the ACS journal of surfaces and colloids》2008,24(14):7124-7131
Emulsions of water in as-recovered native crude oils of diverse geographical origin evidently possess some common morphological features. At low volume fractions varphi of water, the viscosity behavior of emulsions is governed by the presence of flocculated clusters of water droplets, whereas characteristic tight gels, composed of visually monodisperse small droplets, are responsible for the viscosity anomaly at varphi approximately 0.4-0.5. Once formed, small-droplet gel domains apparently retain their structural integrity at higher varphi, incorporating/stabilizing new portions of water as larger-sized droplets. The maximum hold-up of disperse water evidently is the close-packing limit of varphi approximately 0.74. At higher water contents (up to varphi approximately 0.83), no inversion to O/W morphology takes place, but additional water emerges as a separate phase. The onset of stratified flow (W/O emulsion gel + free water) is the cause of the observed viscosity decrease, contrary to the conventional interpretation of the viscosity maximum as a reliable indicator of the emulsion inversion point. 相似文献
62.
Dr. Michael S. Klenov Alexey A. Guskov Dr. Oleg V. Anikin Prof. Dr. Aleksandr M. Churakov Dr. Yurii A. Strelenko Dr. Ivan V. Fedyanin Dr. Konstantin A. Lyssenko Prof. Dr. Vladimir A. Tartakovsky 《Angewandte Chemie (International ed. in English)》2016,55(38):11472-11475
This study presents the first synthesis and characterization of a new high energy compound [1,2,3,4]tetrazino[5,6‐e][1,2,3,4]tetrazine 1,3,6,8‐tetraoxide (TTTO). It was synthesized in ten steps from 2,2‐bis(tert‐butyl‐NNO‐azoxy)acetonitrile. The synthetic strategy was based on the sequential closure of two 1,2,3,4‐tetrazine 1,3‐dioxide rings by the generation of oxodiazonium ions and their intramolecular coupling with tert‐butyl‐NNO‐azoxy groups. The TTTO structure was confirmed by single‐crystal X‐ray. 相似文献
63.
Back Cover: Synthesis of Tetrazino‐tetrazine 1,3,6,8‐Tetraoxide (TTTO) (Angew. Chem. Int. Ed. 38/2016) 下载免费PDF全文
64.
Sergei P. Ivonin Svetlana D. Kopteva Viktor N. Serdyuk Andrei A. Tolmachev Aleksandr M. Pinchuk 《Heteroatom Chemistry》2001,12(7):652-657
This study covers phosphorylation of heterocyclic analogues of N‐methyldiphenylamine with phosphorus tribromide in pyridine solution. The reaction is found to proceed regioselectively in accordance with the orienting effect of the amino group. Mono and bis‐phosphorylated derivatives of the heterocycles have been isolated and characterized. It is pointed out that the heterocyclic systems under study exhibit reduced reactivity in electrophilic phosphorylation as compared to N‐methyldiphenylamine. The results of calculations by the PM3 method are reported for the starting molecules and their σ‐complexes. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:652–657, 2001 相似文献
65.
Viktor A. Tafeenko Olga V. Kaukova Rene Peschar Aleksandr V. Petrov Leonid A. Aslanov 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(10):m421-m423
The crystal structure of the title potassium salt, K+·C8HN4O2−, of the organic anion 3‐cyano‐4‐(dicyanomethylene)‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olate shows that the dicyanomethylene moiety is able to accept an electron in the same way as does tetracyanoethylene, to yield the novel product. The organic anion is nearly planar, with deviations caused by steric crowding among the exocyclic cyano groups. The K+ cations lie within tricapped trigonal prisms that stack to form channels. The three‐dimensional structure is completed by the formation of hydrogen‐bonded chains by the anions. 相似文献
66.
Chang-Sung Lim Aleksandr Aleksandrovsky Maxim Molokeev Aleksandr Oreshonkov Victor Atuchin 《Molecules (Basel, Switzerland)》2021,26(23)
A set of new triple molybdates, LixNa1-xCaGd0.5(MoO4)3:Ho3+0.05/Yb3+0.45, was successfully manufactured by the microwave-accompanied sol–gel-based process (MAS). Yellow molybdate phosphors LixNa1-xCaGd0.5(MoO4)3:Ho3+0.05/Yb3+0.45 with variation of the LixNa1-x (x = 0, 0.05, 0.1, 0.2, 0.3) ratio under constant doping amounts of Ho3+ = 0.05 and Yb3+ = 0.45 were obtained, and the effect of Li+ on their spectroscopic features was investigated. The crystal structures of LixNa1-xCaGd0.5(MoO4)3:Ho3+0.05/Yb3+0.45 (x = 0, 0.05, 0.1, 0.2, 0.3) at room temperature were determined in space group I41/a by Rietveld analysis. Pure NaCaGd0.5Ho0.05Yb0.45(MoO4)3 has a scheelite-type structure with cell parameters a = 5.2077 (2) and c = 11.3657 (5) Å, V = 308.24 (3) Å3, Z = 4. In Li-doped samples, big cation sites are occupied by a mixture of (Li,Na,Gd,Ho,Yb) ions, and this provides a linear cell volume decrease with increasing Li doping level. The evaluated upconversion (UC) behavior and Raman spectroscopic results of the phosphors are discussed in detail. Under excitation at 980 nm, the phosphors provide yellow color emission based on the 5S2/5F4 → 5I8 green emission and the 5F5 → 5I8 red emission. The incorporated Li+ ions gave rise to local symmetry distortion (LSD) around the cations in the substituted crystalline structure by the Ho3+ and Yb3+ ions, and they further affected the UC transition probabilities in triple molybdates LixNa1-xCaGd0.5(MoO4)3:Ho3+0.05/Yb3+0.45. The complex UC intensity dependence on the Li content is explained by the specificity of unit cell distortion in a disordered large ion system within the scheelite crystal structure. The Raman spectra of LixNa1-xCaGd0.5(MoO4)3 doped with Ho3+ and Yb3+ ions were totally superimposed with the luminescence signal of Ho3+ ions in the range of Mo–O stretching vibrations, and increasing the Li+ content resulted in a change in the Ho3+ multiplet intensity. The individual chromaticity points (ICP) for the LiNaCaGd(MoO4)3:Ho3+,Yb3+ phosphors correspond to the equal-energy point in the standard CIE (Commission Internationale de L’Eclairage) coordinates. 相似文献
67.
68.
Cycloelimination of Imidazolidin‐2‐ylidene N‐Heterocyclic Carbenes: Mechanism and Insights into the Synthesis of Stable “NHC‐CDI” Amidinates 下载免费PDF全文
Aleksandr V. Zhukhovitskiy Julie Geng Prof. Dr. Jeremiah A. Johnson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(15):5685-5688
We report the discovery that 1,3‐bis(aryl)imidazolidin‐2‐ylidenes, one of the most widely studied classes of N‐heterocyclic carbenes (NHCs), undergo quantitative conversion to zwitterionic “NHC‐CDI” amidinates upon heating to ≈100 °C in solution. The mechanism of this novel NHC decomposition process is studied in detail. These studies enabled the rational synthesis of a new class of bench stable amidinates from a panel of NHCs and carbodiimides. We expect these constructs to find utility in a variety of applications. 相似文献
69.
Aleksandr I. Chumakov Ilya Sergeev Jean‐Philippe Celse Rudolf Rüffer Marc Lesourd Lin Zhang Manuel Sánchez del Río 《Journal of synchrotron radiation》2014,21(2):315-324
The performance of a cryogenically cooled double‐crystal silicon monochromator was studied under high‐heat‐load conditions with total absorbed powers and power densities ranging from 8 to 780 W and from 8 to 240 W mm?2, respectively. When the temperature of the first crystal is maintained close to the temperature of zero thermal expansion of silicon, the monochromator shows nearly ideal performance with a thermal slope error of 0.6 µrad. By tuning the size of the first slit, the regime of the ideal performance can be maintained over a wide range of heat loads, i.e. from power densities of 110 W mm?2 (at total absorbed power of 510 W) to 240 W mm?2 (at total absorbed power of 240 W). 相似文献