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41.
Synthesen von Heterocyclen, 85. Mitt.: Über die α-Acyllactonumlagerung von 5-Benzoyl-dehydracetsäure
Zusammenfassung Die vonButt undElvidge aufgefundenen Isomeren, 4-Hydroxy-5-acetyl-6-phenyl-pyron-(2) (1) und 4-Hydroxy-5-ben-zoyl-6-methyl-pyron-(2) (2), ergeben bei der Umsetzung mit POCl3 und Eisessig 5-Benzoyl-dehydracetsäure (3). Im Gegensatz zur Dehydracetsäure2 reagiert 5-Benzoyl-dehydracetsäure (3) in alkohol. HCl zum 2,6-Dimethyl-3-äthoxycarbonyl-5-benzoyl-pyron-(4) (6). Die Struktur dieser Verbindung wird auf chemischem und physikalischem Wege abgeleitet.Mit wäßr. HCl läßt sich3 in 2,6-Dimethyl-5-benzoyl-pyron-(4) (5) umwandeln.
The isomeric compounds1 4-hydroxy-5-acetyl-6-phenyl-pyron-2 (1) and 4-hydroxy-5-benzoyl-6-methyl-pyron-2 (2) yield 5-benzoyl-dehydroacetic acid (3) if with glacial acetic acid and POCl3. In contrast to dehydroacetic acid2 5-benzoyl-dehydroacetic acid (3) reacts in ethanolic HCl to 2,6-dimethyl-3-carbethoxy-5-benzoyl-pyron-(4) (6).However, with aquenous HCl3 is converted to 2.6-dimethyl-5-benzoyl-pyron-(4) (5).相似文献
42.
Metallcarbonyl-Synthesen,XIV. Neuartige Vanadium-, Niob- und Tantal-Komplexe mit Wasserstoff-Brücken
Wolfgang A. Herrmann Helmut Biersack Barbara Balbach Peter Wülknitz Manfred L. Ziegler 《欧洲无机化学杂志》1984,117(1):79-94
Syntheses of Metal Carbonyls, XIV. Novel Vanadium, Niobium, and Tantalum Complexes Having Hydrido Bridges The novel homo- and heterodinuclear organometallic μ-hydrido compounds 3a – c of vanadium, niobium, and tantalum have been synthesized by light-induced reactions of the hydridoniobium complex (η5-C5H5)2NbH3 ( 1 ) with the half-sandwich complexes (η5-C5H5)M(CO)4 ( 2a : M = V; 2b : M = Nb; 2c : M = Ta). These compounds have the general composition LxM – H – Nb(CO)(η5-C5H5)2. The formation of the M – H – Nb moieties is a dark-reaction preceded by two photoreactions that are independent from each other elimination of CO from 2a – c and elimination of H2 from 1 , with the extruded carbon monoxide being transfered to the (η5-C5H5)2NbH fragment; subsequent fixation of the species (η5-C5H5)2Nb(CO)H thus generated to the photogragments (η5-C5H5)M(CO)3 results in donor stabilization of these latter groups. The structural architecture of the derivatives 3a und b was established by X-Ray diffraction. The hydrogen bridges are to be considered as three-center two-electron functions that are responsible for a serious lengthening of the otherwise by at least 40 pm shorter metal-to-metal distances amounting to 371.3 pm in 3a and 373.3 pm in 3b (mean values). 相似文献
43.
Klaus Ziegler 《Zeitschrift für Physik B Condensed Matter》1981,43(3):275-280
A chain of interacting vectors (, ) withn components subject to the hyperbolic conditions 2–2=1 is considered. The interaction possesses a global non-compactO(1, n–1)/O(1)×O(n–1) symmetry. Symmetries of this kind are known from the study of disordered electronic systems. The non-compactness of the symmetry group causes divergencies such that a symmetry breaking term is necessary. Asymptotic behaviour of the expectation values and long-ranged correlation functions are calculated for a small symmetry breaking field.Supported in part by the Deutsche Forschungsgemeinschaft through the Sonderforschungsbereich 123 at the University of Heidelberg 相似文献
44.
An overview is given on recent advances of density functional theory (DFT) as applied to the calculation of nuclear magnetic
resonance (NMR) chemical shifts and electron spin resonance (ESR) g-tensors. This is a new research area that has seen tremendous progress and success recently; we try to present some of these
developments. DFT accounts for correlation effects efficiently. Therefore, it is the only first-principle method that can
handle NMR calculations on large systems like transition-metal complexes. Relativistic effects become important for heavier
element compounds; here we show how they can be accounted for. The ESR g-tensor is related conceptually to the NMR shielding, and results of g-tensor calculations are presented. DFT has been very successful in its application to magnetic properties, for metal complexes
in particular. However, there are still certain shortcomings and limitations, e.g., in the exchange-correlation functional,
that are discussed as well.
Received: 24 October 1997 / Accepted: 19 December 1997 相似文献
45.
The electronic structures of MnO?4, MnO2?4, MnO3?4, CrO2?4, CrO3?4, VO3?4, RuO4, RuO?4, RuO2?4, TcO?4 and MoO2?4 have been investigated using the Hartree-Fock-Slater Discrete Variational Method. The calculated ordering of the valence orbitals of all the comlexes is: t1, 4t2, 3a1, 1c, 3t2, with t1 the orbital of highest energy. The calculated single transition energies are in good agreement with experimental values and indicate the uniform assignment: t1 → 2e(v1), 4t2 → 2e(v2). t1 → 5t2(v3), and 4t2 → 5t2(v4). A/D values, calculated from the theory of magnetic circular dichroism (MDC) also support this assignment.Population analyses reveal that all complexes, whether d0, d1 or d2, have d-orbital populations close to those of the corresponding M2+ ions in which two electrons have been removed from the (n + 1)s orbital of M. This is also true of the excited states, such as t1 → 2e and 4t2 → 2e, where a transfer of charge from the ligands to the metal has previously been assumed. It is shown that, instead of a transfer of charge from ligands to metal, electronic excitation consists of a rearrangement of electron density both at the ligands and at the metal. 相似文献
46.
We report the first high-frequency and -field electron paramagnetic resonance (HFEPR) study of a Mn(III) N-confused porphyrin (NCP) complex (NCP is also known as inverted porphyrin or 2-aza-21-carbaporphyrin). We have found a striking variation in the electronic properties of the S = 2 Mn(III) ion coordinated by NCP compared to other Mn(III) porphyrinoid complexes. Thus, inversion of a single pyrrole ring greatly changes the equatorial ligand field exerted and leads to large magnitudes of both the axial and rhombic zero-field splitting [respectively, D = -3.084(3) cm(-1), E = -0.608(3) cm(-1)], which are unprecedented in other Mn(III) porphyrinoids. 相似文献
47.
Wolfgang A. Herrmann Ricardo Serrano Adolf Schäfer Ulrich Küsthardt Manfred L. Ziegler Ernst Guggolz 《Journal of organometallic chemistry》1984,272(1):55-71
Short-wavelength photolysis of tricarbonyl(η5-pentamethylcyclopentadienyl)rhenium (1) (λ < 300 nm, quartz-glass) in tetrahydrofuran yields under partial or complete decarbonylation three novel organorhenium compounds, with the relative yields depending upon the irradiation time. Formed by exhaustive oxidative decarbonylation, the complex trioxo(η5-pentamethylcyclopentadienyl)rhenium(VII) (5) represents the first example of the new class of oxo half-sandwich complexes. The derivatives (μ-O)[(η5-C5Me5)Re(CO)2]2 (2; Me = CH3) and (η5-C5Me5)2Re2(CO)2O2 (3; Me = CH3) containing both oxo and carbonyl ligands are formed from 1 at shorter irradiation times. Both compounds are isolable intermediates along the mechanistically not yet fully established sequence 1 → → 5 as they are degraded to 5 under CO2 elimination in the presence of air and/or light. The mixed oxo carbonyl complex 2 has been characterized by means of single-crystal X-ray diffraction techniques (triclinic, space group P-Ci1; a 907.4(2), b 1040.2(3), c 1414.3(4) pm; α 79.99(2), β 88.42(2), γ 66.18(2)°; Riso = 0.068, Raniso = 0.037, Rw = 0.031). The molecular structure centres around an isosceles Re2O triangle whose metal centres exhibit a strongly distorted square-pyramidal geometry; the metal-metal distance recorded at 281.7(1) pm is in agreement with a single bond by the EAN rule. The centrically coordinated, planar five-membered ring ligands are parallel to each other (interplanar angle 2°) and occupy trans-positions with respect to the central Re2O geometry. 相似文献
48.
Zusammenfassung Beim Verschmelzen von Isatosäureanhydrid (1) mit Thioamiden bilden sich 2-substit.-4(3H)-Chinazolinone (3a-h).
Syntheses of heterocycles, CXXIV.: Reaction of isatoic anhydride with thioamides and amides
The reaction of isatoic anhydride with thioamides yields 2-substituted 4(3H)-quinazolinones (3a-h).相似文献
49.
Zusammenfassung Ketoximäther reagieren mit monosubstituierten Malonsäurechloriden zu Derivaten des 1-Alkoxy-4-hydroxy-2-pyridons, mit Malonsäurediäthylester hingegen zu solchen des 4-Hydroxy-2-pyridons.
Ketoxim O-alkyl ethers react with monosubstituted malonyl chlorides to give derivatives of 1-alkoxy-4-hydroxy-pyrid-2-ones. However, with ethyl malonates 4-hydroxy-pyrid-2-ones are obtained.相似文献
50.
E. Ziegler Th. Kappe H. G. Foraita L. F. Werner 《Monatshefte für Chemie / Chemical Monthly》1970,101(3):923-931
Zusammenfassung Die Darstellung von polymeren Indigofarbstoffen (PI) nach dem Verfahren vonZiegler undKappe
2, 3 wird beschrieben. Ausgehend von Benzidin (1 a) und Tolidin (1 b) erhält man so diePI
6 a bzw.6 b. In analoger Weise wird aus Tetrahydrochinoxalin (7), der N,N-überbrücktePI
12 gewonnen.
Aus den Dissertationen vonH. G. Foraita undL. F. Werner, Universität Graz, Januar bzw. Juni 1963. 相似文献
Syntheses of heterocycles, CXLVI: The synthesis of polymeric indigos with potential semiconductor properties
The synthesis of polymeric indigos (PI) according to the procedure ofZiegler andKappe 2, 3 is described. Starting with benzidine (1 a) or tolidine (1 b) thePI 6 a and6 b, resp., are obtained. In a similar way the N,N-bridgedPI 12 is synthesized from tetrahydroquinoxaline (7).
Aus den Dissertationen vonH. G. Foraita undL. F. Werner, Universität Graz, Januar bzw. Juni 1963. 相似文献