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801.
Falk Lissner Karl Krmer Thomas Schleid Gerd Meyer Zhiwei Hu Günter Kaindl 《无机化学与普通化学杂志》1994,620(3):444-450
The Chlorides Na3xM2–xCl6 (M = La? Sm) and NaM2Cl6 (M = Nd, Sm): Derivatives of the UCl3-Type of Structure. Synthesis, Crystal Structure and X-Ray Absorption Spectroscopy (XANES) Single crystals of the derivatives of the UCl3-type structure Na3xM2–xCl6 (M = La/x = 0.364(4); Ce/0.349(5); Pr/0.318(8); Nd/0.305(5); Sm/0.246(4)) and NaSm2Cl6 were grown by different methods generally under reducing conditions. They are addition [Na(Sm2)Cl6] and addition/substitution variants [Na2x(NaxM2–x)Cl6] of the UCl3 structure type [□(U2)Cl6]. X-Ray Absorption Spectroscopy (XANES) at the LIII edge characterizes NaSm2Cl6 and NaNd2Cl6 as mixed-valence compounds with valences of +2 and +3 in statistical distribution (approximately 1:1) for Sm and Nd, respectively. 相似文献
802.
A generalized cutting-plane algorithm designed to solve problems of the form min{f(x) :x X andg(x,y) 0 for ally Y} is described. Convergence is established in the general case (f,g continuous,X andY compact). Constraint dropping is allowed in a special case [f,g(·,y) convex functions,X a convex set]. Applications are made to a variety of max-min problems. Computational considerations are discussed.Dr. Falk's research was supported by the Air Force Office of Scientific Research, Air Force Systems Command, USAF, under AFOSR Contract No. 73–2504. 相似文献
803.
804.
Clarkson PJ Poole DJ Ryu CK Sharifi VN Swithenbank J Waarlo HJ Ardelt D Falk H 《Analytical and bioanalytical chemistry》2003,377(1):39-47
A system capable of continuously measuring a range of metallic elements in the effluent gas from incinerators and other similar industrial processes, and providing on-line results has been developed. With a state-of-the-art mobile laboratory measurements were taken from a UK municipal solid waste incinerator. The detection system used was an ICP-OES, with a modified torch to allow the introduction of flue gas directly into the plasma. Metals that were investigated were Ni, Hg, V, Al, Na, Ca, Cu, Sn, Pb, Sb, As, Cd and Tl, with limits of detection in the range 0.0004 mg m–3 to 0.1 mg m–3 being calculated. Emission measurements produced data that showed that the MSWI plants emission were significantly lower than the emission limits specified in EC 2000/76/EC. 相似文献
805.
F. Falk 《Colloid and polymer science》1980,258(2):142-147
Summary For the polyethylene crystal, a local, non-linear, static theory of elasticity is established. This theory takes into account the complete microstructure of the material. Within the framework of differential geometry, dislocations and disclinations are introduced. Non-linear, local constitutive equations are established and the equations of elastic equilibrium are derived. The theory may be applied to calculate the deformations and the stress of defects in the polyethylene crystal.
With 3 figures 相似文献
Zusammenfassung Für den Polyäthylenkristall wird eine lokale, nichtlineare, statische Elastizitätstheorie entwickelt, welche die volle Mikrostruktur des Materials berücksichtigt. Mit differentialgeometrischen Methoden werden Versetzungen und Disklinationen eingeführt und die nichtlinearen Gleichgewichtsbedingungen werden abgeleitet. Die Theorie kann zur Berechnung der Deformationen und Spannungen von Defekten im Polyäthylenkristall herangezogen werden.
With 3 figures 相似文献
806.
Summary Depending on the reaction conditions,peri-hydroxy substituted anthraquinones like 1,8-dihydroxyanthraquinone and 1,4-dihydroxyanthraquinone could be derivatized with ammonia, propylamine, isopropylamine, and a lysine derivative to yield a variety of imino and amino substitution and addition products. However, hypericin resisted such derivatization under a variety of reaction conditions. Therefore, the hypothesis that hypericin is bound to its apoprotein in photopigmentsvia a Schiff base to the -amino group of a lysine residue or a terminal amino group seems to be rather unlikely.
Zur Frage der kovalenten Bindung in Hypericin-Chromoproteiden: Schiff-Basenbildung?
Zusammenfassung Abhängig von den Reaktionsbedingungen gabenperi-hydroxylsubstituierte Anthrachinone, wie 1,8-Dihydroxyanthrachinon oder 1,4-Dihydroxyanthrachinon, mit Propylamin, Isopropylamin und einem Lysinderivat eine Reihe von Imino- und Amino-Substitutionsprodukten oder Addukten. Allerdings widerstand Hypericin unter Variation der Reaktionsbedingungen einer solchen Derivatisierung. Deshalb ist die Hypothese, daß Hypericin in seinen Photopigmenten über eine Schiffsche Base mit der -Aminogruppe eines Lysinrestes oder mit einer terminalen Aminogruppe verknüpft ist, eher unwahrscheinlich.相似文献
807.
Summary. It was found that the hypericinate salts of (R)-1-phenylethylamine and (S)-1-(1-naphthyl)-ethylamine display a small chiroptical signal of the same sign only at high concentrations in an apolar solvent.
No further indications of a chiral discrimination between the helical conformers of hypericinate could be found in these cases.
However, upon esterification of the 3-hydroxyl group of hypericin with (1S)-camphanic chloride, the two diastereomers were found in an 1:1 ratio equilibrating rather fast at temperatures above 30°C
with one diastereomer in excess. From the temperature dependence of the equilibrium positions (measured by means of CD and
1H NMR), a ΔG
0 value of 5.8±0.5 kJ·mol−1 was derived. Accordingly, the chiral discrimination of the (M)-configured enantiomer of the helix by the (S)-configured auxiliary occurred at an intermediate level. From the temperature dependence of the equilibration kinetics an
activation energy of E
a = 70±0.5 kJ·mol−1 was derived, which thus defines the upper limit of the helix inversion of hypericin and hypericinate. This value is by about
10 kJ·mol−1 lower than the recently estimated limit.
Corresponding author. E-mail: heinz.falk@jku.at
Received March 22, 2002; accepted April 3, 2002 相似文献
808.
Tris(triphenylphosphine)gold(I)-pentafluorosilicate(IV) ([Au{P(C6H5)3}3][SiF5]) was prepared and the structure was determined by single crystal x-ray diffraction. The complex crystallizes in the triclinic space group P1 (No. 2). The lattice constants are a = 14.634(2) Å, b = 17.180(2) Å, c = 22.212(3) Å, α = 86.48(1)°, β = 78.95(1)°, γ = 83.99(1)°. Number of molecules per cell: Z = 4. The gold atoms are coordinated to three triphenylphosphine ligands to form the trigonal planar cation [Au{P(C6H5)3}3]+. Separated from the cation is the [SiF5]? anion which is regular trigonal bipyramidal coordinated. No interactions between the fluorine atoms and the gold atoms were observed. 相似文献
809.
Karoline Fendler Beate Hager Heinz Falk 《Monatshefte für Chemie / Chemical Monthly》2007,138(9):859-862
Summary. Two model compounds for the tryptophane variant of the green fluorescent protein chromophore containing a 3-indolyl and 2-pyrrolyl
moiety were prepared. For the first one the (Z)-diastereomer was found to be more stable than the (E)-diastereomer by 5.7 kJ mol−1. It could be photo-diastereomerized and its thermal equilibration was studied, whereas the second one underwent photo-destruction.
From an Arrhenius plot an activation barrier for the (E) to (Z) diastereomerization of 85.6 kJ mol−1 could be determined. Thus, it could be demonstrated that in contrast to the corresponding phenyl derivative studied recently
the tyrosine- and tryptophane-derived chromophores of the green fluorescent protein are amenable to fast thermal diastereomerization,
which is of fundamental importance for the fluorescence and photoswitching processes in the corresponding proteins. 相似文献
810.
On the Chemistry of the Resveratrol Diastereomers 总被引:5,自引:0,他引:5
Summary. The (E)- and (Z)-diastereomers of resveratrol were investigated with respect to their photochemical and thermal diastereomerization reactions.
The free enthalpy difference between the two diastereomers was estimated to be in the order of common stilbenes, with the
(E)-diastereomer more stable by about 11–14 kJ mol−1. The Arrhenius activation barrier of about 280 kJ mol−1 was found to be quite high and implies that thermal equilibration cannot account for the (Z)-diastereomer found in nature. A preparative access to the (Z)-diastereomer by photodiastereomerization is described. The 1H and 13C NMR spectra of the two diastereomers were assigned and their absorption spectra and fluorescence quantum yields of the neutral
and monodeprotonated species were determined.
Corresponding author. E-mail: heinz.falk@jku.at
Received October 15, 2002; accepted November 7, 2002
Published online February 20, 2003 相似文献