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71.
Nielsen's equation has been applied for cooling crystallization of KCl from watery solutions. In the calculations activities are used instead of concentrations, the temperature and concentration dependence of both the activity and diffusion coefficients are considered. It is found that A) the interfacial tension between the crystal and its saturated solution is < 2.5 erg/cm2, which is less by two orders of magnitude than that of between crystal and vacuum; B) homogeneous nucleation can take place even at very small supersaturations (ln S < < 0.01), which is unusual in precipitation. 相似文献
72.
73.
Björn Alriksson Ilona Sárvári Horváth Anders Sjöde Nils-Olof Nilvebrant Leif J. Jönsson 《Applied biochemistry and biotechnology》2005,124(1-3):911-922
When dilute-acid hydrolysates from spruce are fermented to produce ethanol, detoxification is required to make the hydrolysates
fermentable at reasonable rates. Treatment with alkali, usually by overliming, is one of the most efficient approaches. Several
nutrients, such as ammonium and phosphate, are added to the hydrolysates prior to fermentation. We investigated the use of
NH4OH for simultaneous detoxification and addition of nitrogen source. Treatment with NH4OH compared favorably with Ca(OH)2, Mg(OH)2, Ba(OH)2, and NaOH to improve fermentability using Saccharomyces cerevisiae. Analysis of monosaccharides, furan aldehydes, phenols, and aliphatic acids was performed after the different treatments.
The NH4OH treatments, performed at pH 10.0, resulted in a substantial decrease in the concentrations of furfural and hydroxymethylfurfural.
Under the conditions studied, NH4OH treatments gave better results than Ca(OH)2 treatments. The addition of an extra nitrogen source in the form of NH4Cl at pH 5.5 did not result in any improvement in fermentability that was comparable to NH4OH treatments at alkaline conditions. The addition of CaCl2 or NH4Cl at pH 5.5 after treatment with NH4OH or Ca(OH)2 resulted in poorer fermentability, and the negative effects were attributed to salt stress. The results strongly suggest
that the highly positive effects of NH4OH treatments are owing to chemical conversions rather than stimulation of the yeast cells by ammonium ions during the fermentation. 相似文献
74.
Tomasz Galica Julia Bkowicz Piotr Broda Ilona Turowska-Tyrk 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(7):593-599
Several conditions need to be fulfilled for a photochemical reaction to proceed in crystals. Some of these conditions, for example, geometrical conditions, depend on the particular type of photochemical reaction, but the rest are common for all reactions. The mutual directionality of two neighbouring molecules determines the kind of product obtained. The influence of temperature on the probability of a photochemical reaction occurring varies for different types of photochemical reaction and different compounds. High pressure imposed on crystals also has a big influence on the free space and the reaction cavity. The wavelength of the applied UV light is another factor which can initiate a reaction and sometimes determine the structure of a product. It is possible, to a certain degree, to control the packing of molecules in stacks by using fluoro substituents on benzene rings. The crystal and molecular structure of 2,6‐difluorocinnamic acid [systematic name: 3‐(2,6‐difluorophenyl)prop‐2‐enoic acid], C9H6F2O2, (I), was determined and analysed in terms of a photochemical [2 + 2] dimerization. The molecules are arranged in stacks along the a axis and the values of the intermolecular geometrical parameters indicate that they may undergo this photochemical reaction. The reaction was carried out in situ and the changes of the unit‐cell parameters during crystal irradiation by a UV beam were monitored. The values of the unit‐cell parameters change in a different manner, viz. cell length a after an initial increase starts to decrease, b after a decrease starts to increase, c increases and the unit‐cell volume V after a certain increase starts to decrease. The structure of a partially reacted crystal, i.e. containing both the reactant and the product, namely 2,6‐difluorocinnamic acid–3,4‐bis(2,6‐difluorophenyl)cyclobutane‐1,2‐dicarboxylic acid (0.858/0.071), 0.858C9H6F2O2·0.071C18H12F4O4, obtained in situ, is also presented. The powder of compound (I) was irradiated with UV light and afterwards crystallized [as 3,4‐bis(2,6‐difluorophenyl)cyclobutane‐1,2‐dicarboxylic acid toluene hemisolvate, C18H12F4O4·0.5C7H8] in a space group different from that of the crystal containing the in‐situ dimer. 相似文献
75.
Josef Kratochvíla Bedřich Friedecký Marek Budina Ilona Šperlingová 《Accreditation and quality assurance》2007,12(3-4):146-150
In this paper, the creation of a certified reference material for urinary creatinine is described. We used the Jaffe method
and HPLC method for establishment of the certified value. Homogeneity tests are also described. We obtained material with
sufficient homogeneity, stability, and with certified value (expanded uncertainty, k=2 for CI 95%) (7.77±0.27) mmol·L−1. This material was consequently used for the interlaboratory comparison (EQA Czech Republic for clinical chemistry). Twenty-nine
percent of the participants obtained measurement results within the interval of the certified value ± expanded uncertainty,
while 85% of the participants obtained values inside the interval of the certified value ± target measurement uncertainty.
Direct use of the certified reference materials for method evaluation in EQA programs means a significant advance for monitoring
and documentation traceability of results in routine measurements. 相似文献
76.
77.
Natural‐Antioxidant‐Inspired Benzo[b]selenophenes: Synthesis,Redox Properties,and Antiproliferative Activity 下载免费PDF全文
Edgars Paegle Dr. Ilona Domracheva Dr. Baiba Turovska Dr. Marina Petrova Dr. Iveta Kanepe‐Lapsa Anita Gulbe Dr. Edvards Liepinsh Dr. Pavel Arsenyan 《化学:亚洲杂志》2016,11(13):1929-1938
The cyclization of arylalkynes under selenobromination conditions, combined with an acid‐induced 3,2‐aryl shift, was elaborated as a general synthetic pathway for the preparation of polyhydroxy‐2‐ and ‐3‐arylbenzo[b]selenophenes from the same starting materials. The redox properties, free‐radical‐scavenging ability, and cytotoxicity against malignant cell lines (MCF‐7, MDA‐MB‐231, HepG2, and 4T1) of the synthesized compounds were explored, and the obtained results were used to consider the structure–activity relationships (SARs) in these compounds. Consequently, the structural features that were responsible for the highly potent peroxyl‐radical‐scavenging activity were established. 相似文献
78.
István Simonyi und Ilona Kékesy 《Fresenius' Journal of Analytical Chemistry》1966,215(3):187-190
Zusammenfassung Eine Methode zur Bestimmung aliphatischer und aromatischer Säurechloride wird beschrieben. Hierbei werden die Säurechloride mit acetonhaltiger Natriumjodidlösung quantitativ zu Natriumchlorid und Säurejodid umgesetzt. Das in Aceton unlösliche Natriumchlorid wird abfiltriert, in Wasser gelöst und nach Volhard bestimmt. Die üblichen Zersetzungsprodukte stören die Bestimmung nicht. Die Fehler liegen meist unter 1%.
Summary A method is recommended for the determination of aliphatic and aromatic acid chlorides. It consists in converting the acid chlorides to the iodides by sodium iodide in acetonic solution, filtering off the sodium chloride formed quantitatively by this reaction and insoluble in acetone, dissolving it in water and titrating by Volhard's method. The determination is not influenced by the usual decomposition products of acid chlorides. Errors are mostly smaller than 1%.相似文献
79.
1,5-Dihydropentalene (4) is formed as the main product on treatment of trans-1,2-bis(2,2-dibromocyclo-propyl)ethene 3 with methyllithium at −40°. In addition the reaction affords 1- and 2-propadienylcyclopentadienes (5a) and (5b), and trans-1,2,4,6,7-octapentaene (6), new C8H8 isomers. Diels-Alder adducts of 4, 5a and 5b were obt in the reaction with perfluorobut-2-yne. The formation of 1,5-dihydropentalene 4 is explained by a double ring expansion sequence involving consecutive carbene-carbene rearrangements with 1,3-carbon and subsequent 1,2-hydrogen shifts, supported by the reaction of double labelled (13C-depleted) 3. From readily available 3 at low temperatures formation and fusion of two 5-membered rings are achieved in one step. 相似文献
80.
Andreas Wirth Ilona Lange Dagmar Henschel Oliver Moers Armand Blaschette Peter G. Jones 《无机化学与普通化学杂志》1998,624(8):1308-1318
Polysulfonylamines. CII. New Coordination Compounds Derived from Triorganyltin(IV) Dimesylamides and Uncharged Ligands: Mononuclear and Polynuclear Complexes with Molecular or Ionic Crystal Structures The purpose of this report is to draw attention to the remarkable versatility of the dimesylamides R3SnA [A– = (MeSO2)2N–; R = Me ( 1 a ) or Ph ( 1 b )] as precursors for pentacoordinate triorganyltin(IV) complexes belonging to four distinct structural types. Representative complexes were prepared by treating 1 a or 1 b in the appropriate molar ratios with unidentate thiourea or urea-type ligands or with the bidentate ligand [Ph2P(O)CH2]2 (DPPOE). The following compounds were characterized by X-ray analysis: [Me3Sn(A)(thiourea)] ( 2 a ; monoclinic, space group P21/n), [Ph3Sn(A)(tetramethylthiourea)] ( 2 b ; monoclinic, P21, two independent formula units), [Me3Sn(1-methylurea)2]+ · A– ( 3 a ; monoclinic, P21/c), [Ph3Sn(1,1-dimethylurea)2]+ · A– ( 3 c ; triclinic, P1), [{Ph3Sn(A)}2(μ-dppoe)] ( 4 ; triclinic, P1), [Ph3Sn(μ-dppoe)]nn+ · n A– · n MeCN ( 5 ; monoclinic, P21/c). The lattices of 2 a , 2 b and 4 contain discrete uncharged formula units which are mononuclear for 2 a and 2 b or dinuclear for 4 , whereas 3 a , 3 c and 5 have ionic structures featuring mononuclear cations for 3 a and 3 c or an infinite linear-polymeric cation for 5 . In all the structures, the tin atoms adopt trigonal-bipyramidal geometries, the apical positions being occupied in 2 a and 2 b by the S atom of the thiourea and one O atom of A–, in 3 a and 3 c by the O atoms of two urea-type ligands, in 4 by an O atom of the bridging DPPOE molecule and one O atom of A–, and in 5 by two phosphoryl O atoms from different bridging DPPOE ligands. In the structures of 2 a , 3 a and 3 c , the (thio)urea NH functions are connected to A– via intermolecular or interionic N–H … O and N–H … N hydrogen bonds. Crystals of [{Me3Sn(bipyH+ … A–)}2(μ-bipy)]2+ · 2 A– ( 6 ; monoclinic, C2/c) formed adventitiously in a reaction mixture containing 1 a and 4,4′-bipyridine. The rod-like supramolecular cation of 6 (length ca. 4 nm) is built up from two Me3Sn+ units bridged through bipy and unidentally coordinated by a monoprotonated bipy (= bipyH+), resulting in a trigonal-bipyramidal geometry around tin (N atoms apical); each of the terminal bipyH+ ligands forms an +N–H … N– hydrogen bond with one A–. 相似文献