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991.
M. Sanderova K. Sandera O. Spengler K. Zablinsky G. d'Orazi F. Massa H. Riehm M. Martaire J. A. Ambler S. Byall G. G. Kindt A. Wolf A. Chaudun H. Claassen R. Pajetta D. Lever V. Harlay E. Schapiro A. Jolles Elisabeth Rosenblüh-Robozund G. Vavrinecz R. A. Stageman D. T. Englis H. R. Kraybill W. J. Youden J. T. Sullivan P. Bobkow M. Rupnowskaja G. Reif Th. v. Fellenberg P. Demont 《Analytical and bioanalytical chemistry》1938,114(7-8):292-310
992.
993.
Summary
Lithium carbonate was titrated after dissolution in a glacial acetic acid/carbon tetrachloride mixture with 0.05 N perchloric acid in glacial acetic acid in the presence of gentian violet indicator. In the case of lithium nitrate the nitrate was firts reduced with ascorbic acid and the lithium titrated in an acetic anhydride/glacial acetic acid medium with the same measuring solution and indicator. The lithium content of lithium ferrites and lithium-nickel-zinc ferrites was measured after the extraction of iron and nickel by means of methyl-isobutyl ketone in a glacial acetic acid/carbon tetrachloride solution in the presence of tropeoline OO/methylene blue indicator mixture.
Volumetrische Bestimmung von Lithium in Lithiumcarbonat und -nitrat sowie in Lithiumferriten in nichtwärigem Medium
Zusammenfassung Lithiumcarbonat wird nach Auflösung in Eisessig/Tetrachlorkohlenstoff mit 0,05 N Perchlorsäure in Eisessig titriert, wobei Gentianaviolett als Indicator dient. Bei der Analyse von Lithiumnitrat wird zunächst das Nitrat mit Ascorbinsäure reduziert und dann die Titration mit Perchlorsäure gegen Gentianaviolett durchgeführt. Im Falle von Lithium- und Lithium-Nickel-Zink-Ferriten werden Eisen und Nickel durch Extraktion mit Isobutylmethylketon abgetrennt und anschließend wird mit Perchlorsäure in Eisessig/Tetrachlorkohlenstoff gegen ein Indicatorgemisch aus Tropäolin OO und Methylenblau titriert. Die Fehler liegen bei ± 0,5% für Carbonat und Nitrat und 0,5–1% für Ferrite.相似文献
994.
Enzymes may be used to develop an environmentally friendly alternative to the conventional polluting technologies in textile
finishing. The action of the unlabeled and fluorescent labeled proteolytic enzymes subtilisin and trypsin on wool was examined.
Scanning electron micrographs and a diffusion study, based on fluorescence microscopy, localized the enzymatic attack on the
fiber. A kinetic study was carried out by monitoring the amino acid content of the treatment liquor.
Enzymatic action is not confined to the fiber surface. To limit attack to the surface and reduce wool damage new treatment
methods such as enzyme immobilization onto a solid carrier must be investigated. 相似文献
995.
Winkler Elisabeth Foidl Nikolaus Gübitz Georg M. Staubmann Ruth Steiner Walter 《Applied biochemistry and biotechnology》1997,(1):449-456
Jatropha curcas is a tropical plant widely distributed in arid areas. The seeds contain about 55% of oil, which is mainly used for the production
of soap as a fuel and after transesterification as biodiesel. Various methods for recovering of oil from the seeds, including
extraction with organic solvents and water, have been investigated. Compared to hexane extraction (98%) the oil extraction
using water only yielded 38% of the total oil content of the seeds. Using several cell wall degrading enzymes during aqueous
extraction a maximum yield of 86% was obtained. The influence of cellulolytic, hemicellulolytic enzymes, as well as proteases
was studied. The experiments were carried out at different pH-values and temperatures to find out the optimum for oil recovering
using enzymes. , Surprisingly, the best results (86%) were obtained using an alkaline protease. Combinations of proteases
with hemicellulases and/or cellulases did not further increase the extraction yield. The enzyme-supported aqueous extraction
offers a nontoxic alternative to common extraction methods using organic solvents with reasonable yields. 相似文献
996.
Johann Schinnerl Elisabeth Kaltenegger Thomas Pacher Srunya Vajrodaya Otmar Hofer Harald Greger 《Monatshefte für Chemie / Chemical Monthly》2005,136(9):1671-1680
Summary. Three new pyrroloazepine type alkaloids, stichoneurines A and B and 6-hydroxycroomine were isolated from the lipophilic root extracts of Stichoneuron caudatum and Stemona tuberosa collected in Thailand together with the already known croomine, tuberostemonine, and tuberostemonine A. The structures were elucidated by spectroscopic methods including H/H-COSY, HMQC, and HMBC. Information on the relative stereochemistries and conformational behaviour was obtained by analysis of the NOESY spectra. The formation of pyrroloazepine alkaloids in the genus Stichoneuron is reported for the first time and supports its affiliation to the family Stemonaceae. The occurrence of two different types of alkaloids, of the tuberostemonine and croomine series, in different geographical provenances of Stemona tuberosa is of special chemosystematic interest and may contribute to a more natural species delimitation within that complex group. 相似文献
997.
Hans‐Dietrich Stachel Elisabeth Immerz‐Winkler Hermann Poschenrieder Andreas Windt Wolfgang Weigand Norbert Drescher Ralf Wünsch 《Helvetica chimica acta》2003,86(7):2471-2480
The title compounds were prepared starting from the dihydropyrrolones 4 – 6 . Nucleophilic displacement and ring closure yielded the 1H‐pyrrolo[3,2‐c]isothiazol‐5(4H)‐ones 8 and 10 . The fused systems formed salts with strong acids and electrophiles ( 15, 16 ), as well as with bases. Oxidation led either to S(2)‐oxides ( 18a, 20a ) or to the corresponding bicyclic sultams ( 18b, 20b ), depending on the reaction conditions. The sulfinamide 18a was also obtained from the known 1,2‐dithiolopyrrolone S‐oxide 21 by a ring‐opening/ring‐closure reaction sequence. O‐Methylation of 8 furnished the ‘azafulvene' 17 . The oxidative addition of [Pt(η2‐C2H4)L2] ( 24a : L=Ph3P, 24b : L=1/2 dppf, 24c : L=1/2 (R,R)‐diop) to 18a and 20a led to the cis‐amido‐sulfenato Pt complexes 25 and 26a – c , respectively. 相似文献
998.
Jürgens B Irran E Senker J Kroll P Müller H Schnick W 《Journal of the American Chemical Society》2003,125(34):10288-10300
Single-phase melem (2,5,8-triamino-tri-s-triazine) C(6)N(7)(NH(2))(3) was obtained as a crystalline powder by thermal treatment of different less condensed C-N-H compounds (e.g., melamine C(3)N(3)(NH(2))(3), dicyandiamide H(4)C(2)N(4), ammonium dicyanamide NH(4)[N(CN)(2)], or cyanamide H(2)CN(2), respectively) at temperatures up to 450 degrees C in sealed glass ampules. The crystal structure was determined ab initio by X-ray powder diffractometry (Cu K alpha(1): P2(1)/c (No. 14), a = 739.92(1) pm, b = 865.28(3) pm, c = 1338.16(4) pm, beta = 99.912(2) degrees, and Z = 4). In the solid, melem consists of nearly planar C(6)N(7)(NH(2))(3) molecules which are arranged into parallel layers with an interplanar distance of 327 pm. Detailed (13)C and (15)N MAS NMR investigations were performed. The presence of the triamino form instead of other possible tautomers was confirmed by a CPPI (cross-polarization combined with polarization inversion) experiment. Furthermore, the compound was characterized using mass spectrometry, vibrational (IR, Raman), and photoluminescence spectroscopy. The structural and vibrational properties of molecular melem were theoretically studied on both the B3LYP and the MP2 level. A structural optimization in the extended state was performed employing density functional methods utilizing LDA and GGA. A good agreement was found between the observed and calculated structural parameters and also for the vibrational frequencies of melem. According to temperature-dependent X-ray powder diffractometry investigations above 560 degrees C, melem transforms into a graphite-like C-N material. 相似文献
999.
Peroxidase-modified electrodes: Fundamentals and application 总被引:10,自引:0,他引:10
Tautgirdas Ruzgas Elisabeth Csregi Jenny Emnus Lo Gorton Gyrgy Marko-Varga 《Analytica chimica acta》1996,330(2-3):123-138
Peroxidase-modified amperometric electrodes have been widely studied and developed, not only because of hydrogen- and organic peroxides are important analytes but also because of the key role of hydrogen peroxide detection in coupled enzyme systems, in which hydrogen peroxide is formed as the product of the enzymatic reaction. Many important analytes, such as, aromatic amines, phenolic compounds, glucose, lactate, neurotransmitters, etc. could be monitored by using bi- or multi-enzyme electrodes. In this review the heterogeneous electron transfer properties of peroxidases are discussed as a basis for the analytical application of the peroxidase-modified amperometric electrodes, and examples are given for various peroxidase electrode designs and their application. 相似文献
1000.
Patrick Seta Elisabeth Bienvenue Bertrand D'Epenoux Louis Tenebre Michel Momenteau 《Photochemistry and photobiology》1987,45(1):137-143
Abstract— When spread on an oxidizing aqueous subphase, an amphipathic basket handle zinc porphyrin (P) monolayer gives rise to a photoinduced Volta potential change. This surface photopotential is interpreted on the basis of an interfacial electron transfer in the interphase; upon light excitation, electrons are transferred from the chromophores in the monolayer to electron acceptors diffusing from the subphase. A kinetic model for charge separation and stabilization is proposed to account for the influences of the electron acceptor concentration, the pH of the subphase and the light intensity. 相似文献