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901.
Nadica Ivošević DeNardis Vera Žutić Vesna Svetličić Ruža Frkanec Jelka Tomašić 《Electroanalysis》2007,19(23):2444-2450
Amperometry of oxygen reduction at the dropping mercury electrode (DME) was applied for in situ characterization of liposome suspensions in terms of concentration, level of polydispersity and potential range of adhesion. Liposomes prepared from egg‐phosphatidylchloline/cholesterol/dicetylphosphate in the molar ratio of 7 : 5 : 1 were suspended in phosphate‐buffered saline (PBS). Adhesion signals of single liposomes in air‐saturated suspensions were detected in the broad potential range (from ?100 to ?1200 mV vs. 0.1 M Ag/AgCl reference electrode) as transient enhacements of oxygen reduction. Measured concentration range in air‐saturated suspensions was 106–108 liposomes/L. 相似文献
902.
B. Ponsard J. Hiltunen P. Penttilla H. Vera Ruiz A. L. Beets S. Mirzadeh F. F. Knapp Jr. 《Journal of Radioanalytical and Nuclear Chemistry》2003,257(1):169-174
The rapidly increasing therapeutic applications of 188Re in nuclear medicine, oncology and interventional cardiology require routine production of large, multi-Curie levels of the 188W parent. The capability and effective coordination of back-up production sites is important to insure that high level 188W/188Re generators are continually available. We have coordinated 188W production at the High Flux Isotope Reactor (HFIR - Oak Ridge, US) with production at the BR2 Reactor (Mol, Belgium) characterized by peak thermal neutron fluxes of 2.51·015 (HFIR) and 1·1015 (BR2) neutrons/cm2·sec, respectively. The long 69-day physical half-life permits receipt of 188W from BR2 within 0.25 T
1/2's, even after the 12-day post irradiation cooling required for 187W decay (T
1/2 = 24 hours). Since 188W production by double neutron capture of enriched 186W is a function of the square of the thermal neutron flux, HFIR production (4-5 Ci 188W/g 186W/cycle) is higher than at the BR2 (1.0-1.1 Ci/g 186W/cycle). However, the specific activity (SA) of BR2-produced 188W is still about 0.8-0.9 Ci/g after processing at ORNL following shipment from Belgium. This SA is sufficiently high to permit fabrication of 1 Ci generators suitable for clinical use, since simple post elution concentration of the saline bolus (30-50 ml) obtained from the generator can provide samples with high specific volume (1 ml volume). The time periods from reactor push in Mol and completion of processing, fabrication and shipment of generators from Oak Ridge have been 19-21 days. Six campaigns have been successfully completed since 1998, with processed levels of 188W in Oak Ridge from 8-26 Curies/campaign. 188W has been provided to MAP Medical technologies Oy (Tikkakoski, Finland) for fabrication and distribution of generators for use at IAEA-supported research projects in developing countries. We have thus established and demonstrated an effective collaboration between the Studiecentrum voor Kernenergie-Centre d'Etude de l'Energie Nucléaire (SCK·CEN) and ORNL for back-up production of 188W. This collaboration continues to be especially helpful during periods when interruption of HFIR operation is necessary for maintenance and upgrades. 相似文献
903.
By reaction of (C5H5)2Ti(μ-S2)2C6H10 3 with S2Cl2 7,8,9,10,11,12-hexathiaspiro-[5.6]dodecane 4 is prepared (yield 51%) and characterized by UV, IR, Raman, mass, and NMR spectra (1H, 13C). The seven-membered CS6 ring undergoes pseudorotation in solution. With S7Cl2 the complex 3 yields 7,8,9,10,11,12,13,14,15,16,17-undecathiaspiro[5.11]heptadecane 5 (yield 23%). The yellow, monoclinic crystals of 5 consist of spirocyclic C6H10S11 molecules with the C6 ring in a chair-conformation while the CS11 ring is of the same conformation as cyclododecasulfur S12. UV, IR, Raman, mass and NMR-spectra of 5 are reported. A mixture of dichlorosulfanes SnCl2 (n = 1 -8) reacts with 3 to give the homologous series C6H10Sm which was characterized by reversed-phase HPLC for m = 5 – 14. 相似文献
904.
Vera Zeidan 《Applied Mathematics and Optimization》1984,11(1):97-109
We are concerned with developing sufficiency criteria for the generalized problem of Bolza, where the Hamiltonian is neither concave-convex nor differentiable. The core of the approach is the modified Hamilton-Jacobi inequality which leads to a new type of sufficient conditions. This latter is then used to derive new first order and known second order sufficient conditions.The publication of this report has been made possible due to a grant of the Fonds FCAC for the help and support of research. 相似文献
905.
Marcio José Tiera Gerson Rodrigues dos Santos Vera A. de Oliveira Tiera Neide Aparecida Blaz Vieira Elisabete Frolini Rodrigo C. da Silva Watson Loh 《Colloid and polymer science》2005,283(6):662-670
A series of N-isopropylacrylamide (NIPAM)-acrylic acid–ethyl methacrylate terpolymers with varied monomer compositions was prepared by radical polymerization. The solution behavior of these polymers was studied in dilute aqueous solution using spectrophotometry, fluorescence spectroscopy and high-sensitivity differential scanning calorimetry. The results obtained revealed that the lower critical solution temperatures depend strongly on the copolymer composition, solution pH and ionic strength. At a high pH, the ionization of acrylic acid (AA) units leads to an increase in solution cloud points (Tc). Solutions of polymers containing 10% or less of AA display a constant Tc for pH above 5.5, with 15% there is a continuous increase in Tc with pH and, for higher AA contents, no clouding was observed within the studied temperature range. Fluorescence probe studies were conducted by following the I 1/I 3 ratio of pyrene vibronic bands and the emission of anilinonaphtalene sulfonic acid, sodium salt (ANS), both approaches revealing the existence of hydrophobic domains for polymers with higher ethyl methacrylate content at temperatures lower than Tc, suggesting some extent of aggregation and/or a coil-to-globule transition. Scanning calorimetry measurements showed an endothermic transition at temperatures agreeing with the previously detected cloud points. Moreover, the transition curves became broader and with a smaller transition enthalpy, as both the AA content and the solution pH were increased. These broader transitions were interpreted to be the result of a wider molecular distribution upon polymer ionization, hence, displaying varied solution properties. The decrease in transition enthalpy was rationalized as a consequence of reminiscent hydration of NIPAM units, even after phase separation, owing to the presence of electric charges along the polymer chain. 相似文献
906.
Letf(n) (resp.g(n)) be the largestm such that there is a digraph (resp. a spanning weakly connected digraph) onn-vertices andm edges which is a subgraph of every tournament onn-vertices. We prove that $$n\log _2 n - c_1 n \geqq f(n) \geqq g(n) \geqq n\log _2 n - c_2 n\log \log n.$$ 相似文献
907.
The potential energy surfaces for the fragmentation of the radical anions of p-nitrochlorobenzene and p- and m-chloroacetophenones were explored using first principle methods. The behavior of these compounds, stabilized by pi acceptors, is compared to that shown by the unsubstituted halobenzenes (PhX, X = F, Cl, Br, I). The presence of pi and sigma radical anions was inspected as well as the intramolecular electron transfer (intra-ET) from the pi to the sigma surface, responsible for the dissociation of these intermediates. The profiles obtained with the B3LYP functional in the gas phase and in the presence of a polar solvent are in agreement with the spectroscopic evidence and with the experimentally observed reactivity of the compounds under study. The stability of the radical anion of p-nitrochlorobenzene and the adiabatic and endothermic nature of its dissociation are explained. The order of the rate constants for dissociation m-chloroacetophenone < p-chloroacetophenone is interpreted on the basis of the differences in the adiabatic character of the intra-ET of both isomers which is ascribed to the nodal properties of their SOMOs. In the halobenzene family, the electronic factors responsible for the intra-ET are analyzed. The stabilization of the sigma surface exerted by the different halogens and its effect on the rate constants for dissociation are explained. 相似文献
908.
Adriana Chilin Giovanni Marzaro Samuele Zanatta Vera Barbieri Giovanni Pastorini Paolo Manzini Adriano Guiotto 《Tetrahedron》2006,62(52):12351-12356
A new synthetic pathway to quinazolines is described. This new method uses hexamethylenetetramine in TFA and potassium ferricyanide in aqueous ethanolic KOH, starting from simple N-protected anilines. The method affords substituted quinazolines with high selectivities and good yields, reducing reaction-time and work-up operations. 相似文献
909.
Vera I. Maslennikova Tatyana Yu. Sotova Konstantin A. Lyssenko Sergei O. Adamson Wolf D. Habicher 《Tetrahedron》2007,63(19):4162-4171
The phosphorylation of 2,2′,7,7′-tetrahydroxydinaphthylmethane was studied and the influence of molecule pre-organization on the regioselectivity of functionalization was investigated. The reactions of 2,2′,7,7′-tetrahydroxydinaphthylmethane with phosphorous amides containing 1-3 amide bonds gave oligophosphorylated derivatives differing in the number and the nature of phosphorus fragments and in the size of phosphorus rings: tetraphosphorus macrocycles containing one 24-membered and two eight-membered phosphorus rings, triphosphorus compounds containing a phosphocine ring and two acyclic phosphorus fragments, and tetraphosphorylated derivatives with four phosphorus groups in the molecule. The possibility of controlling the regioselectivity of phosphorylation by using reagents differing in the number and activity of P-N bonds was demonstrated. 相似文献
910.
This work proposes a new equation of state (EOS) based on molecular theory for the prediction of thermodynamic properties of real fluids. The new EOS uses a novel repulsive term, which gives the correct hard sphere close packed limit and yields accurate values for hard sphere and hard chain virial coefficients. The pressure obtained from this repulsive term is corrected by a combination of van der Waals and Dieterici potentials. No empirical temperature functionality of the parameters has been introduced at this stage. The novel EOS predicts the experimental volumetric data of different compounds and their mixtures better than the successful EOS of Peng and Robinson. The prediction of vapor pressures is only slightly less accurate than the results obtained with the Peng-Robinson equation that is designed for these purposes. The theoretically based parameters of the new EOS make its predictions more reliable than those obtained from purely empirical forms. 相似文献