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971.
G. Volland G. Kölblin P. Tschöpel und G. Tölg 《Fresenius' Journal of Analytical Chemistry》1977,284(1):1-12
Zusammenfassung Es wird versucht, an Hand ausgewählter Elemente (Fe, Co, Ni, Ag und Cd) schwerwiegende systematische Fehler bei der Bestimmung durch flammenlose Atomabsorptionsspektrometrie aufzuzeigen und deren Ursache zu diskutieren. Neben den Parametern des Temperaturprogramms und des Schutzgasstroms ist die Art und Struktur des Graphits, sowie dessen Reaktivität von entscheidendem Einfluß auf Empfindlichkeit und Nachweisvermögen des Verfahrens. Depressionen bei der Verwendung stark saurer Analysenlösungen werden bestätigt und es wird versucht, diese im Zusammenhang mit der Reaktivität von Graphit zu erklären.An einem vereinfachten Modell wird der Einfluß organischer Lösungsmittel bzw. organischer Lösungen von Komplexbildnern wie Dithizon, NH4-DDTC und APDC auf die Atomisierung untersucht. Es wird diskutiert, ob die dabei registrierten Depressionen Verluste sind, die durch die Bildung flüchtiger metallorganischer Verbindungen bereits bei Temperaturen ab 500° C entstehen. Besonders schwerwiegend sind diese Verlustreaktionen bei Anwesenheit halogenierter Kohlenwasserstoffe, wie an Hand der Reaktionen von Fe, Cd, Co, Ni und Ag mit Chloroform gezeigt werden kann.
Some sources of systematic errors in the determination of elements in the ng- and pg-range by atomic absorption spectrometry with flameless excitation in the graphite oven
With selected elements (Fe, Co, Ni, Ag and Cd), the serious systematic errors inherent in flameless atomic absorption spectrometry are demonstrated and their origins are discussed. Besides the parameters of the temperature program and the inert gas stream, the type and structure of the graphite, as well as its reactivity have a decisive influence on the sensitivities and limits of detection of the technique. Depression of the signal is observed with the use of strongly acid solutions and it has been attempted to explain this in connection with the reactivity of the graphite.The influence of organic solvents and organic solutions of complexes with dithizone, NH4-DDTC and APDC on the atomization have been investigated with simplified examples. It can be presumed that the resulting depression of the signal is due to losses by the formation of volatile metal-organic compounds at temperatures above 500° C. Particularly large are the losses in the presence of hydrocarbon halides as can be demonstrated by the reaction of Fe, Cd, Co, Ni, and Ag with chloroform.相似文献
972.
K. O. Hiller B. Masloch und H. J. Möckel 《Fresenius' Journal of Analytical Chemistry》1977,283(2):109-113
Zusammenfassung Alkyldisulfide, Alkylbenzole und Alkylbromide wurden an einer chemisch gebundenen Kohlenwasserstoffphase (MicroPak-CH) mit Wasser-Methanol-Gemischen unterschiedlicher Zusammensetzung chromatographiert. In den entsprechenden Lösungsmittelgemischen wurden die SÄttigungslöslichkeiten der Probenkomponenten bestimmt. Man fand, da\ die SelektivitÄt innerhalb einer homologen Reihe durch die Löslichkeit der Glieder in der mobilen Phase bestimmt ist. Dabei lie\ sich der chromatographische KapazitÄtsfaktor mit guter Genauigkeit als k = b · (1/csat)2/3 darstellen. log k und log c
sat hÄngen linear von der C-Zahl ab.
Relation between solubility and capacity factor in the reverse-phase-bonded-phase chromatography of alkylbenzenes, alkylbromides and alkyldisulphides
Alkyldisulphides, alkylbenzenes and alkylbromides were chromatographed on a hydrocarbon type bonded stationary phase (MicroPak-CH) using water-methanol-mixtures of various composition as mobile phase. The solubility of the sample components was determined in the respective mobile phases. It was found that the selectivity within a homologous series is determined by the solubility in the mobile phase. The capacity factor can be expressed as k = b · (1/csat)2/3. Log k and log c sat depend linearly on the carbon number.相似文献
973.
Thermal and thermo-oxidative degradation of polyethylene and polypropylene is discussed. The products of thermal and thermo-oxidative degradation are analysed using a GC-MS after previous adsorption in a column containing a sorbent of styrene divinyl benzene copolymer type. Aldehydes are the products mostly resulting from the thermo-oxidation of polyethylene and methyl ketones are those resulting from the thermo-oxidation of polypropylene.
Analyse der thermischen Oxidationsprodukte von Polypropylen und Polyäthylen durch Gas-Chromatographie/ Massenspektrometrie
Zusammenfassung Der thermische und thermisch-oxidative Abbau von Polyäthylen und Polypropylen wird diskutiert. Die Abbauprodukte wurden mit Hilfe der GC-MS nach vorhergehender Adsorption an einer Säule aus Styrol-Divinylbenzol-Copolymer analysiert. Die thermischen Oxidationsprodukte des Polyäthylens sind meistens Aldehyde, die des Polypropylens Methylketone.相似文献
974.
The Diels-Alder reaction of enantiomerically pure (E)-γ-keto-α,β-unsaturated p-tolylsulphoxides 3 with cyclopentadiene give four easily separable diastereomers. The effect of several Lewis acids on the reaction was studied, finding a high endo selectivity with respect to the carbonyl group and moderate π-diastereoselectivity using BF3·Et2O as catalyst. The reactivity of compounds 3 as well as their endo selectivity are both higher than those observed for the corresponding (E)-3-sulfinylacrylates. 相似文献
975.
F. Schaller W. Schwarz H.-D. Hausen K. W. Klinkhammer J. Weidlein 《无机化学与普通化学杂志》1997,623(9):1455-1466
Base-free Tris(trimethylsilyl)methyl Derivatives of Lithium, Aluminium, Gallium, and Indium Base-free LiR* (R*=-C(SiMe3)3) has been prepared from R*Cl and Li-metal in toluene at 85?90°C and used to synthesize the metallanes R*MMe2 with M = Al, Ga and In, respectively. The NMR (1H, 13C, 29Si) and the vibrational spectra of these trisyl compounds have been discussed. AlCl3 and LiR*(ratio 1 : 1) forms the metallate metallate Li[R*AlCl3]. The triclinic unit cell (space group P1 ) consists of a centrosymmetric assoziate, formed by four Li[R*AlCl3]- units with Al? Cl…?Li bridges, two pairs of Li-atoms differing in their chlorine-coordination and two disordered toluene molecules, inserted in the crystal lattice (R1wR2 =0,0444/0,1072). The reaction of GaCl3 with LiR* (I :1) gives the unusual sesquichloride (R*Ga(Cl1,33)Me0,67)3 in moderate yield. The X-ray structure determination shows a Ga3Cl3-skeleton with chairconformation and disordered, terminal gallium ligands (R1/wR2= 0,0646/0,2270). 相似文献
976.
Electrospray ionization mass spectrometry was applied to the study of the amines IQ, Trp-P-1, Trp-P-2, PhIP and AC and the co-mutagens harman and norharman. The results obtained on a triple quadrupole mass spectrometer equipped with a pneumatically assisted electrospray source are reported. The chromatographic conditions were optimized with a reversed-phase column (1 mm I.D.) using acetonitrile-5 mM ammonium acetate (pH 6.7) (50:50) as the mobile phase at a flow-rate of 50 μl min−1. Different parameters influencing the mass spectra were investigated. For these compounds [M + H]+ in the positive-ion mode and also some fragments produced through collisionally activated decomposition in the interface were observed. Detection limits of 5.4–44 pg were obtained for standard solutions of these amines. Analysis of a meat extract was performed by HPLC-MS using single-ion monitoring after a solid-phase extraction clean-up. 相似文献
977.
N. Z. Tugusheva L. M. Alekseeva A. S. Shashkov V. G. Granik 《Russian Chemical Bulletin》2006,55(8):1470-1474
The reactions of 3-cyano-3(5)-formyl-2-oxo-4-(phenylamino)-1,2-dihydropyridines with CH acids were studied. The previously
unknown fused 2-pyridone derivatives containing the 4-aminopyridine fragment were synthesized by the Knoevenagel reaction.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1416-1420, August, 2006. 相似文献
978.
Yunyu Yi Ronald Neufeld Selim Kermasha 《Journal of Sol-Gel Science and Technology》2006,38(3):251-259
Entrapment of membrane proteins is a challenging task compared to that involving soluble proteins. Chlorophyllase, a membrane
protein, was successfully entrapped in tetramethoxysilane-derived sol-gel. Pre-gel sol typically consists of an aqueous suspension
of chlorophyllase, precursors including tetramethoxysilane and/or methytrimethoxysilane, and sodium fluoride as catalyst.
To obtain a highly active entrapped enzyme preparation, the effects of various immobilization parameters, including the chemical
compositions of pre-gel sol (water/silane ratio, precursor type and proportions, enzyme loading, sodium fluoride concentration),
and sol-gel process parameters (aging and drying time and approach) have been investigated. Chlorophyllase demonstrated the
highest activity in gel derived from a pre-gel sol with water/silane ratio of 30 and enzyme loading of 0.257 mgprotein/ggel, and showed moderately lower activity in organically modified sol-gel than that in hydrophilic sol-gel. The effects of water/silane
ratio and precursor combinations on the activity of entrapped chlorophyllase were also studied by examining the pore morphology
of gel via nitrogen adsorption-desorption. Longer aging time leads to an entrapped chlorophyllase preparation with higher
activity. Chlorophyllase preparation demonstrated negligible activity after air-drying for 12 h while lyophilized chlorophyllase
preparation demonstrated 8, 4 and 4 times higher activity than air-dried, vacuum-dried and solvent-dried preparations. Chlorophyllase
demonstrated 30% higher activity in the improved sol-gel protocol than that from a non-optimized sol-gel protocol developed
in a previous study. 相似文献
979.
Summary The effects of concentration, separation and spectral similarity as factors influencing the accuracy of iterative target testing
factor analysis (ITT-FA) are investigated for three component systems by the application of analysis of variance (ANOVAR).
ANOVAR is applied over a range of peak separations to map the changing effects of the three factors with increasing overlap.
Two error responses were measured and analysed, (a) Relative cluster error (RCE) a measure of the error over all peaks in
a cluster and (b) Relative peak error (RPE) the error of an individual peak. Multicomponent analysis (MCA) a method requiringa priori spectral information, is used as a referee method for ITT-FA. 相似文献
980.
Günter Eichberger Herfried Griengl Willibald Paar 《Monatshefte für Chemie / Chemical Monthly》1986,117(4):545-551
Reaction of 3-methyl-1,3-oxazolidine with phthalic anhydride in chloroform leads to ring opening and higher oligomers2 are formed. These are cleaved by addition of protic solvents and 2-methylaminoethyl hydrogenphthalate3 a is obtained. Other 1,3-oxazolidines and succinic anhydride behave similarly.
Herrn Prof. Dr. Dr. h. c.Karl Kratzl mit den besten Wünschen zum 70. Geburtstag gewidmet. 相似文献