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961.
Alfredo Camparini Fabio Ponticelli Piero Tedeschi 《Journal of heterocyclic chemistry》1985,22(6):1561-1565
A synthetic pathway to 3-methylisoxazolo[4,5-d]pyridazine and some of its derivatives is described. Uv irratiation of 4,7-dimethoxy (XVII) and 7-chloro-4-hydrazino-3-methylisoxazolo[4,5-d]pyridazine (IX) shows that both intramolecular rearrangements and solvent involving reactions can occur. 相似文献
962.
Angeli Mary PA Dhanuskodi S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(7):1473-1481
The EPR spectra of Cu2+ ion in L-Arginine phosphate monohydrate (LAP) at X-band frequencies at room temperature reveal the presence of two magnetically inequivalent interstitial Cu2+ sites in the lattice. The principal values of the g- and A-tensors indicate rhombic symmetry around the Cu2+ ion. From the direction cosines of the principal values of the g- and A- tensors, the orientations of the sites in the lattice have been identified. The bonding parameters were evaluated and the ground state wave function of Cu2+ ion was constructed. The ground state is found to be an admixture of [x2 - y2> and [3z2 - r2> orbitals. The optical absorption studies show four bands centered at 9803, 10753, 15748 and 16666 cm(-1) confirming the rhombic symmetry around the Cu2+ ion. Using the observed bands the crystal field parameters have been evaluated. 相似文献
963.
László Jánosi László Kollár Piero Macchi Angelo Sironi 《Transition Metal Chemistry》2007,32(6):746-752
Pt(diphosphine)X(aryl) complexes [diphosphine = 1,3-bis(diphenylphosphino)propane (dppp), 2,4-bis(diphenylphos phino)pentane (bdpp); aryl = phenyl, 2-thiophenyl; X = Cl, I] have been reacted with ethyl diazoacetate in chloroform.
It has been revealed by in␣situ n.m.r. studies that the starting compounds insert the carbene, formed from ethyl diazoacetate, into the Pt–aryl group resulting
in Pt(diphosphine)X{CH(aryl)COOC2H5}. Depending on the reaction conditions (reaction time, ratio of the reactants) and the ligands various side-reactions have
been observed: (i) the formation of Pt(diphosphine)X2 in chloroform, (ii) the insertion of the :CHCOOC2H5 fragment into the Pt–halide bond of the dihalogeno complexes Pt(diphosphine)X2 resulting in the exclusive formation of Pt(diphosphine)X(CHXCOOC2H5). Diastereoselective insertion reactions have been observed in the presence of (S,S)-bdpp as diphosphine. The Pt{(S,S)-bdpp)}I(Ph) complex has been characterized by X-ray crystallography. 相似文献
964.
Liu Y Chen SH Berti D Baglioni P Alatas A Sinn H Alp E Said A 《The Journal of chemical physics》2005,123(21):214909
The phonon propagation and damping along the axial direction of films of aligned 40 wt % calf-thymus DNA rods are studied by inelastic x-ray scattering (IXS). The IXS spectra are analyzed with the generalized three effective eigenmode theory, from which we extract the dynamic structure factor S(Q,E) as a function of transferred energy E=variant Planck's over 2piomega, and the magnitude of the transferred wave vector Q. S(Q,E) of a DNA sample typically consists of three peaks, one central Rayleigh scattering peak, and two symmetric Stokes and anti-Stokes Brillouin side peaks. By analyzing the Brillouin peaks, the phonon excitation energy and damping can be extracted at different Q values from about 4 to 30 nm(-1). A high-frequency sound speed is obtained from the initial slope of the linear portion of the dispersion relation below Q=4 nm(-1). The high-frequency sound speed obtained in this Q range is 3100 ms, which is about twice faster than the ultrasound speed of 1800 ms, measured by Brillouin light scattering at Q approximately 0.01 nm(-1) at the similar hydration level. Our observations provide further evidence of the strong coupling between the internal dynamics of a DNA molecule and the dynamics of the solvent. The effect on damping and propagation of phonons along the axial direction of DNA rods due to divalent and trivalent counterions has been studied. It is found that the added multivalent counterions introduce stronger phonon damping. The phonons at the range between approximately 12.5 and approximately 22.5 nm(-1) are overdamped by the added counterions according to our model analyses. The intermediate scattering function is extracted and it shows a clear two-step relaxation with the fast relaxation time ranging from 0.1 to 4 ps. 相似文献
965.
Piero Zanello Renato Seeber Arnaldo Cinquantini Bruno Crociani 《Transition Metal Chemistry》1980,5(1):226-229
Summary The electrochemical behaviour of neutral platinum(II) and palladium(II) isocyanide complexes has been investigated in an aprotic medium at platinum and mercury electrodes. Platinum(II) derivatives are reduced to platinum(0) species, Palladium(II) compounds give rise to palladium(0) species at room temperature, while at 0° it is possible to obtain palladium(I) compounds. 相似文献
966.
A. Di Piero A. Di Piero M. A. Bacchi M. A. Bacchi E. A. N. Fernandes E. A. N. Fernandes 《Journal of Radioanalytical and Nuclear Chemistry》2006,269(2):447-450
Summary The k0-method in INAA has been used at CENA/USP Brazil for analyzing geological and biological materials. With the acquisition of
a well-type detector, it was realized that the true-coincidence effects, originally corrected by semi-empirical procedures
with the in-house k0-software (Quantu-INAA), would affect the accuracy of results. Thus, new coincidence correction algorithms were developed,
based on a theoretical equation for obtaining the correction factors. Validation of the algorithms was performed by analysis
of plant certified reference materials. 相似文献
967.
Solans-Monfort X Sodupe M Branchadell V Sauer J Orlando R Ugliengo P 《The journal of physical chemistry. B》2005,109(8):3539-3545
The adsorption of NH(3) and H(2)O in acidic chabazite has been studied with the B3LYP method within the cluster approach (5T, 48T clusters) and the periodic approach adopting a Si/Al = 11/1 chabazite and a basis set of polarized double-zeta quality. The 5T cluster has been treated fully ab initio at the B3LYP level whereas the 48T cluster has been treated with the ONIOM2 scheme using B3LYP as the high level of theory and the MNDO, AM1, and HF/3-21G methods as low levels of theory. Periodic calculations show that the adsorption of NH(3) in acidic chabazite takes place through an ion pair (NH(4)(+)-CHA(-)) structure, the computed adsorption energy being -32 kcal/mol. The adsorption of H(2)O leads to a hydrogen bonded (H(2)O-HCHA) complex with the computed adsorption energy of -20 kcal/mol. All ONIOM combinations provide similar structures to those obtained with periodic calculations. Adsorption energies, however, are sensitive to the low level used, especially for NH(3). The ONIOM B3LYP:HF/3-21G method is the one that provides more satisfactory results. Present results show that, for larger zeolites, the ONIOM scheme can be successfully applied while drastically reducing the cost of a fully ab initio treatment. 相似文献
968.
Several supramolecular architectures generated by guanosine derivatives are described. The research started from the fortuitous observation of a lyotropic behavior exhibited by a guanylic nucleotide in water. This observation stimulated extensive research on several natural and lipophilic guanosine derivatives which self-assemble in different architectures (discs, ribbons, helices...), according to their structure and environment. These ordered structures can be used as scaffolds for photo- or electro-active moieties and for the fabrication of molecular electronic devices. 相似文献
969.
Fumagalli A Ulivieri P Costa M Crispu O Della Pergola R Fabrizi de Biani F Laschi F Zanello P Macchi P Sironi A 《Inorganic chemistry》2004,43(6):2125-2131
The redox aptitude of the dinitrido anion [Co10N2(CO)19]4- has been tested from both chemical and electrochemical points of view, together with its reactivity toward CO that induces disproportionation. In any case, through a remarkable overlapping of intermediate steps, the new anion [Co11N2(CO)21]3- (4) is eventually obtained. A detailed study of the pathways to 4 allowed the identification of three labile intermediates by their characteristic IR spectra as well as their electrochemical and paramagnetic properties. The unprecedented structure of trianion 4 has been studied in details in two different crystalline salts. 相似文献
970.
Dell'Anna MM Gallo V Mastrorilli P Nobile CF Romanazzi G Suranna GP 《Chemical communications (Cambridge, England)》2002,(5):434-435
The ionic liquid [bmim][BF4] (1-n-butyl-3-methylimidazolium tetrafluoroborate) was used as innovative solvent for a recyclable catalytic system active in metal promoted Michael additions employing Ni(acac)2 as catalyst. 相似文献