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121.
Pierluigi Contucci Sandro Graffi Joel L. Lebowitz 《Journal of statistical physics》2007,126(4-5):729-729
122.
In this paper, we prove the existence and uniqueness of the solution to the one-dimensional initial-boundary value problem resulting from the Frémond thermomechanical model of structural phase transitions in shape memory materials. In this model, the free energy is assumed to depend on temperature, macroscopic deformation and phase fractions. The resulting equilibrium equations are the balance laws of (linear) momentum and energy, coupled with an evolution variational inequality for the phase fractions. Fourth-order regularizing terms in the quasi-stationary momentum balance equation are not necessary, and, as far as we know for the first time, all the non-linear terms of the energy balance equation are taken into account. 相似文献
123.
Nonsymmetric designs, with , admitting a solvable flag‐transitive automorphism group of affine type not contained in are classified. 相似文献
124.
Giuliana Gervasio Domenica Marabello Claudia Barolo Pierluigi Quagliotto Guido Viscardi 《Journal of heterocyclic chemistry》2003,40(1):129-133
The X‐ray analyses of some neutral and cationic derivatives of 2‐(4‐methylpyridin‐2‐yl)‐1H‐benzimida‐zole are reported and the structural data tentatively correlated to relative UV‐visible properties. A rotation of the γ‐picoline ring with respect to the benzimidazole moiety may be responsible of the spectral behavior. 相似文献
125.
Caramella P Quadrelli P Toma L Romano S Khuong KS Northrop B Houk KN 《The Journal of organic chemistry》2005,70(8):2994-3008
The three potential energy surfaces of the trans-trans, cis-trans, and cis-cis divinyltetramethylene diradicals have been located with DFT calculations at the BPW91/6-311+G levels. The three surfaces account well for the experimental results reported for the thermolysis of optically active trans-1,2-divinylcyclobutane and optically active and deuterated 4-vinylcyclohexene. The surfaces account also for the outcome of the dimerization of butadiene and the thermolysis of cis,cis-1,5-cyclooctadiene. The three diradical intermediates are connected to the cyclization and dissociation products through conformations that are explored fully here. 相似文献
126.
Monica Panigati Pierluigi Mercandelli Giuseppe D’Alfonso Angelo Sironi 《Journal of organometallic chemistry》2005,690(8):2044-2051
The addition of one equivalent of dimethylamine (DMA) to the 44 valence-electron triangular cluster anion [Re3(μ3-H)(μ-H)3(CO)9]− (1) affords the novel unsaturated derivative [Re3(μ-H)4(CO)9(DMA)]− (2, 46 valence electrons) which contains a dimethylamine molecule terminally coordinated to a cluster vertex. Theoretical calculations (DFT) reveal that in the more stable conformation the dimethylamine NH proton is directed towards the hydride bridging the opposite cluster edge in syn position, the close proximity of the ligands bound to the cluster surface allowing the formation of an unconventional N-H ? (μ-H)Re2 hydrogen bond. The presence of this conformation in the solid state has been proven by an X-ray structural analysis of crystalline [PPh4]2. Spectroscopic evidences (IR and NMR) indicate that the dihydrogen bond is maintained also in solution and, by the evaluation of the proton spin-lattice relaxation rates at variable temperature, a good estimate of the H ? H distance in solution has been determined. 相似文献
127.
Remelli M Donatoni M Guerrini R Janicka A Pretegiani P Kozłowski H 《Dalton transactions (Cambridge, England : 2003)》2005,(17):2876-2885
Prion diseases are characterized by a structural modification of the regular prion protein (PrP(C)) to its isoform, termed PrP(Sc)(scrapie). Such a modification involves the secondary and tertiary structure of the protein; the amino acidic sequence remains unchanged. PrP(Sc) is almost insoluble in non-denaturing solvents, resistant to proteases and it loses its redox activity. PrP(C) is able to bind copper and other metal ions: these complexes have been suggested to play an important role in the protein refolding leading to PrP(Sc). It is well-known that at least one relatively strong copper-binding site is located in the PrP(92--126) domain, where two His residues (96 and 111) are present. However, in the same domain, other amino acidic residues bear potentially donating atoms, i.e. Met, Asn and Lys residues. In order to shed light on the role of the side chains of such potentially tridentate amino acids on copper complexation, the polypeptide Ac-KTNMKHMA-NH(2), corresponding to the PrP(106--113) fragment, and some synthetic analogues have been investigated as ligands for the copper ion, by means of both thermodynamic and spectroscopic techniques. The pivotal role of imidazolic side chain of His in "anchoring" the metal ion has been confirmed. On the other hand, no clue was found on the participation of sulfur atom of Met or side amino-group of Lys residues to copper complex-formation. 相似文献
128.
129.
Vittorio Frosini Pierluigi Magagnini Enzo Butta Mario Baccaredda 《Colloid and polymer science》1966,213(1-2):115-120
Summary The dynamic mechanical properties at acoustic and low-ultrasonic frequencies (6–60 kHz) have been determined in polycyclopentylmethacrylate
(PCPMA), polycyclohexylmethacrylate (PCHMA), polycyclohepthylmethacrylate (PCHpMA), polycyclooctylmethacrylate (PCOcMA), polycyclohexylacrylate
(PCHA), polyvinylhexahydrobenzoate (PVHHBz), polyvinylcyclohexylether (PVCHE) and polyvinylcyclohexane (PVCH) Measurements
were carried out by an electrostatic method (flexural vibrations) over the temperature range 60 °K to room temperature.
All polymers, except for polyvinylcyclohexane, exhibit a γ-relaxation, connected with internal motion of the cycloalkyl ring, whose activation parameters depend exclusively on the
nature of the ring.
PVCHMA, PVCHA, PVHHBz, PVCHE and PVCH exhibit a further secondary relaxation effect (δ-process) at lower temperature, whose position on the temperature scale, strength (peak height) and activation parameters
depend on the nature of the units to which the cyclohexyl ring is attached. The δ-process is attributed to some complex motion of the whole cyclohexyl ring, involving oscillatory rotation of the same around
simple bonds which link it to the backbone chain. Contrarily to the δ-process of the phenyl side group containing polymers, the δ-process of the polymers here examined seems to be more sensibly dependent on intramolecuar effects.
Zusammenfassung Es wurden die dynamischen Eigenschaften im akustischen und im Bereich langsamer Ultraschallfrequenzen (6–60 kHz) untersucht für Polycyclopentylmethacrylat (PCPMA), Polycyclohexylmethacrylat (PCHMA), Polycycloheptylmethacrylat (PCHpMA), Polycyclooctylmethacrylat (PCOcMA), Polycyclohexylacrylat (PCHA), Polyvinylhexahydrobenzoat (PVHHBz) Polyvinylcyclohexyl?ther (PVCHE) und Polyvinylcyclohexan (PVCH). Die Untersuchungen wurden mit einer elektrostatischen Methode (Biegeschwingung) über den Temperaturbereich von 60 °K bis Raumtemperatur durchgeführt. Alle Polymeren, au?er Polyvinylcyclohexanen, zeigen eine γ-Relaxation verbunden mit internen Bewegungen des Cycloalkylrings, deren Aktivierungsparameter wesentlich von der Natur des Rings abh?ngen. PVCHMA, PVCHA, PVHHBz, PVCHE und PVCH zeigen einen weiteren sekund?ren Relaxationseffekt (δ-Proze?) bei tieferen Temperaturen, dessen Lage in der Temperaturskala, St?rke (Peakh?he) und Aktivierungsparameter von der Natur der Einheiten abh?ngen, an welchen der Cyclohexylring h?ngt. Der δ- Proze? wird irgendeiner komplexen Bewegung des ganzen Cyclohexylrings zugeschrieben, eingeschlossen oszillatorische Rotation desselben um die Einfachbindung, die ihn mit der Hauptkette verbindet. Anders als der δ-Proze? der Phenylseitengruppen enthaltenden Polymerenketten scheint der hier untersuchte δ-Proze? emfindlicher von intramolekularen Effekten abzuh?ngen.相似文献
130.
Melucci D Zattoni A Casolari S Reggiani M Sanz R Reschiglian P Torsi G 《Annali di chimica》2004,94(3):197-206
Membraneless hyperlayer flow field-flow fractionation (Hyp FIFFF) has shown improved performance with respect to Hyp FIFFF with membrane. The conditions for high recovery and recovery independent of sample loading in membraneless Hyp FIFFF have been previously determined. The effect of sample loading should be also investigated in order to optimize the form of the peaks for real samples. The effect of sample loading on peak retention parameters is of prime importance in applications such as the conversion of peaks into particle size distributions. In this paper, a systematic experimental work is performed in order to study the effect of sample loading on retention parameters. A procedure to regenerate the frit operating as accumulation wall is described. High reproducibility is obtained with low system conditioning time. 相似文献