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81.
Darwin P. R. Kint Antxon Martínez de Ilarduya Abdelilah Alla Sebastin Muoz‐Guerra 《Journal of polymer science. Part A, Polymer chemistry》2003,41(1):124-134
Poly(ethylene terephthalate‐co‐isophthalate‐co‐5‐tert‐butylisophthalate) (PETItBI) terpolymers were investigated with reference to poly(ethylene terephthalate) (PET) homopolymer and poly(ethylene terephthalate‐co‐isophthalate) (PETI) copolymers. Three series of PETItBI terpolyesters, characterized by terephthalate contents of 90, 80, and 60 mol %, respectively, with different isophthalate/5‐tert‐butylisophthalate molar ratios, were prepared from ethylene glycol and mixtures of dimethyl terephthalate, dimethyl isophthalate, and 5‐tert‐butylisophthalic acid. The composition of the terpolymers and the composition of the feed agreed. All terpolymers had a random microstructure and number‐average molecular weights ranging from 10,000 to 20,000. The PETItBI terpolyesters displayed a higher glass‐transition temperature and a lower melting temperature than the PETI copolymers having the same content of terephthalic units. Thermal stability appeared essentially unchanged upon the incorporation of the 5‐tert‐butylisophthalic units. The PETItBIs were crystalline for terephthalate contents higher than 80 mol %, and they crystallized at lower rates than PETI. The crystal structure of the crystalline terpolymers was the same as that of PET with the 1,3‐phenylene units being excluded from the crystalline phase. Incorporation of isophthalate comonomers barely affected the tensile modulus and strength of PET, but the brittleness of the terpolymers decreased for higher contents in 5‐tert‐butylisophthalic units. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 124–134, 2003 相似文献
82.
Francisca Zamora Khalid Hakkou Abdelilah Alla Jos L. Espartero Sebastin Muoz‐Guerra Juan A. Galbis 《Journal of polymer science. Part A, Polymer chemistry》2005,43(24):6394-6410
The synthesis and characterization of new aromatic homo‐ and copolyesters based on l‐arabinitol and xylitol are described. These polymers were obtained by polycondensation reaction of the 2,3,4‐tri‐O‐methyl‐l‐arabinitol or 2,3,4‐tri‐O‐methyl‐xylitol, or their mixtures with ethylene glycol, with terephthaloyl chloride or isophthaloyl chloride in o‐dichlorobenzene or in the melt phase from the corresponding methyl phthalates. All the polymers were characterized by GPC, IR, and NMR. Their Mw values ranged between 11,500 and 46,500, with polydispersities from 1.5 to 2.3. They were found to be soluble in chloroform, but insoluble in water. In contrast with the homopolymers completely made with EG, they showed a significant hygroscopicity. DSC and TGA studies showed that the melting temperature of polyethylene terephthalate is depressed by the presence of pentitol units, whereas the thermal stability is kept above 350 °C. Only copolyesters containing 10% or less of pentitol units showed melting and produced X‐ray diffraction patterns characteristic of crystalline material. d‐Arabinitol‐based homopolyesters appeared to be more crystalline than those derived from xylitol and also presented a higher thermal stability. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6394–6410, 2005 相似文献
83.
84.
This paper analyzes the effect on the optimal value of a given linear semi-infinite programming problem of the kind of perturbations which more frequently arise in practical applications: those which affect the objective function and the right-hand-side coefficients of the constraints. In particular, we give formulae which express the exact value of a perturbed problem as a linear function of the perturbation. 相似文献
85.
Giuseppe Mensitieri Domenico Larobina Gaetano Guerra Vincenzo Venditto Maurizio Fermeglia Sabrina Pricl 《Journal of Polymer Science.Polymer Physics》2008,46(1):8-15
The transport of chloroform in films of atactic polystyrene and of semicrystalline syndiotactic polystyrene in its nanoporous form (δ‐form) has been investigated by gravimetric analysis. Experimental tests have been performed at 35, 49, and 56 °C and at several vapor pressures ranging from 0.5 to 100 Torr. Nonequilibrium lattice fluid prediction of the amorphous sorption behavior was used to enucleate the sorption contribution of the crystalline nanoporous phase from semicrystalline samples. Sorption behavior of the crystalline phase has been interpreted on the basis of Langmuir equation. Moreover, the chloroform sorption at low activities in the crystalline nanoporous phase has been predicted by using Grand Canonical Monte Carlo molecular simulations. Isosteric heats of sorption were also experimentally evaluated for the crystalline phase, and compared with the corresponding prediction of molecular simulation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 8–15, 2008 相似文献
86.
A. Del Guerra A. Giazotto M.A. Giorgi A. Stefanini D.R. Botterill D.W. Braden P.R. Norton 《Physics letters. [Part B]》1973,45(4):409-410
The azimuthal angle dependence of the process ep → enπ+ has been measured by detecting the electron and neutron in coincidence. Data are presented for momentum transfers (?k2) between 0.08 and 0.32 and at energies close to threshold. Fixed-t dispersion relation models give predictionsin good qualitative agreement with the data. 相似文献
87.
Gian Fabrizio De Angelis Diego De Falco Francesco Guerra 《Physics letters. [Part B]》1977,68(3):255-257
We consider Wilson's lattice approximation to scalar Quantum Electrodynamics. We establish correlation inequalities of Griffiths-Kelly-Sherman type and a rigorous transfer matrix formalism, from which existence and non triviality of the infinite volume limit follow. 相似文献
88.
89.
A. L. S. Angelis J. Antos M. Beaulieu H. Beker G. Briskin J. Bystricky M. -G. Catanesi P. Cerello S. Dagan G. Dellacasa M. Diehl S. Di Liberto B. Dolgoshein M. Esten C. W. Fabjan A. Gaidot M. Gallio P. Giubellino U. Goerlach C. Guerra L. -A. Hamel S. Konovalov I. Kralik G. London F. Martelli J. -P. Martin M. Masera M. -A. Mazzoni F. Meddi M. -T. Muciaccia S. Muraviev A. Nomerotsky Y. Oren J. -P. Pansart G. Poulard L. Ramello L. Riccati G. Rosa L. Sandor M. Sarris E. Scomparin A. Shmeleva S. Simone S. Smirnov P. Taras J. Urban E. Vercellin 《The European Physical Journal C - Particles and Fields》1998,5(1):63-75
Results are presented on and production in p–W and S–W interactions at 200 GeV/c/nucleon measured via the dimuon decay in a large kinematic region. The data are normalized to
the charged particle multiplicity in the same rapidity interval. They have been collected using the HELIOS/3 muon spectrometer
at the CERN SPS. The ratio , where is the relevant resonance branching fraction, increases between proton and sulphur projectiles, and is somewhat enhanced going from peripheral to central
S–W interactions. This results from an increase in the number of produced 's per charged particle. The ratio is measured in different intervals of p and rapidity. It is not clearly dependent on p, but is larger at higher rapidities. production, likewise normalized to charged multiplicity, is significantly lower in S–W compared to p–W interactions.
Received: 27 October 1997 / Revised version: 5 March 1998 / Published online: 13 July 1998 相似文献
90.
Giuseppe Distefano Maurizio Guerra Francesco Paolo Colonna Derek Jones Giovanni Consiglio Domenico Spinelli 《Chemical physics》1982,72(3):267-279
The shake-up satellites present in the O1s and N1s energy regions of the XPS spectra of the planar 4-N-piperidyl-nitrobenzene (1) and 2-N-piperidyl-5-nitrothiophen (3), and of the sterically hindered 2-N-piperidyl-nitrobenzene (2), 2-N-piperidyl-3-nitrothiophen (4) and 3-N-piperidyl-2-nitrothiophen (5) and, for comparison, of 2-bromo-3-nitrothiophen (6) have been analyzed with the help of CNDO/S CI calculations. The spectra of the planar derivatives closely resemble these of the related compounds previously analysed, the main satellites deriving from the transition between the highest occupied molecular orbital (HOMO, localized at the donor-ring moiety) towards the lowest unoccupied one (LUMO, localized at the nitro group). Calculations indicate that in the ortho derivatives new relaxation processes are allowed upon N1s/NO2 ionization. In 2, where the angle of rotation θ is closer to 90° than 60°, the NR 2 lone-pair orbital relaxes through space towards the core-ionized N/NO2 atom. In 4 and 5, where 45° ? θ ? 60°, both through-ring and through-space relaxations are present. The assignment of the main N1s/NO2 line in 1 is discussed. 相似文献