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31.
Nicola Armaroli Gianluca Accorsi JohnN. Clifford Jean‐Franois Eckert Jean‐Franois Nierengarten 《化学:亚洲杂志》2006,1(4):564-574
Oligophenylenevinylene (OPV)‐terminated phenylenevinylene dendrons G1 – G4 with one, two, four, and eight “side‐arms”, respectively, were prepared and attached to C60 by a 1,3‐dipolar cycloaddition of azomethine ylides generated in situ from dendritic aldehydes and N‐methylglycine. The relative electronic absorption of the OPV moiety increases progressively along the fullerodendrimer family C60G1 – C60G4 , reaching a 99:1 ratio for C60G4 (antenna effect). UV/Vis and near‐IR luminescence and transient absorption spectroscopy was used to elucidate photoinduced energy and electron transfer in C60G1 – C60G4 as a function of OPV moiety size and solvent polarity (toluene, dichloromethane, benzonitrile), taking into account the fact that the free‐energy change for electron transfer is the same along the series owing to the invariability of the donor–acceptor couple. Regardless of solvent, all the fullerodendrimers exhibit ultrafast OPV→C60 singlet energy transfer. In CH2Cl2, the OPV→C60 electron transfer from the lowest fullerene singlet level (1C60*) is slightly exergonic (ΔGCS≈0.07 eV), but is observed, to an increasing extent, only in the largest systems C60G2 – C60G4 with lower activation barriers for electron transfer. This effect has been related to a decrease of the reorganization energy upon enlargement of the molecular architecture. Structural factors are also at the origin of an unprecedented OPV→C60 electron transfer observed for C60G3 and C60G4 in apolar toluene, whereas in benzonitrile, electron transfer occurs in all cases. Monitoring of the lowest fullerene triplet state by sensitized singlet oxygen luminescence and transient absorption spectroscopy shows that this level is populated through intersystem crossing and is not involved in photoinduced electron transfer. 相似文献
32.
J.C. Hardy G.C. Ball W.G. Davies J.S. Forster H. Schmeing E.T.H. Clifford 《Nuclear Physics A》1981,357(2):356-364
The Q-value for the 129Xe(3He, d)130Cs reaction is measured to be +5 ± 20 keV. By combining this result with the known neutron separation energy of 130Xe, we derive the total decay energy of 130Cs130Xe to beQEC = 2974 ± 20 keV. This value agrees well with two previous positron end-point measurements but disagrees with the corresponding value derived from the 1977 atomic mass evaluation. This has significance in testing the accuracy of the calculated ratio for 130Cs decay. The mass excess of 130Cs is derived to be ?86908 ± 14 keV. An excited state in 130Cs. was also identified at 121 ± 15 keV with J < 3 and positive parity. The Q-value for 136Xe(3He, d)137Cs was measured to be 1918 ± 12 keV. 相似文献
33.
A theoretical and experimental treatment of axial dispersion in coiled tubes is presented. The dispersion, δ, is related to the theoretical plate height divided by four times the radius of the tube (H/4r). This parameter, when plotted against the product of the Reynolds number and the Schmidt number (ReSc), accurately predicts maxima in dispersion curves. Variations in the boundary layer thickness and the velocity profile cause the dispersion to pass through a maximum at a constant value of log (De2Sc1·14) equal to 6.13 for unretained solutes (De is the Dean number). A new measure of dispersion is proposed; the reduced dispersion, ? = 256/(Re0.667Sc), is derived from the experimental behavior of dispersion at values of log (De2Sc1·14) smaller than 6.13. The logarithm of ? is found to be approximately zero for 2.2 < log (De2Sc1·14) < 6.1 and to decrease linearly with log (De2Sc1·14) at higher values. Experiments with four solutes that have a wide range of molecular diffusivities are reported. Results agree with theory. 相似文献
34.
Generalised diffusion processes are discussed using the theory of stochastic processes and several elementary results are proved for the survival probability of a pair of particles with an arbitrary potential. The reaction probability conditioned on reaction ultimately occurring is considered and its backward equation is determined. In the case of the Coulomb potential the probability is shown analytically to be identical in both the attractive and repulsive cases for a given absolute value of rc. The utility of this result in numerical solutions of the Debye—Smoluchowski equation is discussed. 相似文献
35.
Octavio Surez-Iglesias Ignacio Medina Consuelo Pizarro Julio L. Bueno 《Fluid Phase Equilibria》2007,260(2):279-286
The Taylor–Aris chromatographic technique was employed for the determination of diffusion coefficients of 2-fluoroanisole, 2-bromoanisole, allylbenzene and 1,3-divinylbenzene at infinite dilution in supercritical carbon dioxide from 313.16 to 333.16 K and pressures between 15 and 35 MPa. As expected, the diffusivities rise when temperature increases and pressure decreases. Numerous predictive equations are compared with experimental data: Lai–Tan, Liu–Ruckenstein cluster formula, Woerlee, Hippler–Schubert–Troe, Catchpole–King, Eaton–Akgerman, He, He–Yu, Liu–Silva–Macedo, Funazukuri and coworkers, Dariva–Coelho–Oliveira, Zhu–Lu–Zhou–Wang–Shi and the Liu–Ruckenstein RHS formula. The equations of He, He–Yu and Catchpole–King are the best of all, but cannot be used in the whole range of temperatures and solvent densities. 相似文献
36.
The bis[1-(9-anthracene)phosphirane]dithiolatoplatinum(II) complexes, Pt[1-(9-anthracene)phosphirane](2)(dithiolate), where dithiolate = 1,1-dimethoxycarbonyl-ethylene-2,2-dithiolate (dmdt) (2), 1,1-diethoxycarbonyl-ethylene-2,2-dithiolate (dedt) (3), 1-ethoxycarbonyl-1-cyano-ethylene-2, 2-dithiolate (ecdt) (4), and 1,1-dicyano-ethylene-2,2-dithiolate (dcdt) (5), were prepared from cis-dichlorobis[1-(9-anthracene)phosphirane]platinum(II) (1). Complexes 3 and 5 were characterized by X-ray crystallography and were found to have vastly different crystal and molecular structures. The crystal and molecular structure of 3 is dominated by intramolecular pi-stacking between the anthracene rings of the cis-bis(anthracene)phosphiranes with a ring...ring separation of 3.48(6) A. The molecular structure of 5 does not exhibit an intramolecular interaction between the anthracene rings. Instead, the crystal structure of 5shows significant intermolecular pi-stacking between the anthracene rings of the phosphirane ligands of adjacent molecules packed in the crystal lattice. The intermolecular stacking interaction results in a ring...ring separation of 3.33(4) A. Complexes 2-5 were found to emit at 530 nm at low temperatures in the solid state. Complex 5 emits strongly in fluid THF or benzene solution at 430 nm. 相似文献
37.
Richard Gilardi Clifford George Jerome Karle Philip E. Eaton Allison M. Fisher 《Journal of heterocyclic chemistry》1993,30(5):1385-1388
Exploration of the reactions of the 9-azahomocubane system led to derivatives of two small-ring systems containing aza-bridging atoms, 5-azatetracyclo[4.2.0.03,8.04,7]octane and 9-azatetracyclo[4.3.0.02,5.04,7]nonane. The structures were characterized by X-ray diffraction analyses. There are no prior X-ray structural reports on these systems. 相似文献
38.
Gerard de Leeuw John S. Field Raymond J. Haines Beth McCulloch Elsie Meintjies Christiaan Monberg Gillian M. Olivier Praveen Ramdial Clifford N. Sampson Beate Sigwarth Nick D. Steen Kandasamy G. Moodley 《Journal of organometallic chemistry》1984,275(1):99-111
Reaction of [Fe2(CO)9] with a half molar amount of R2PYPR2 (Y = CH2, R = Ph, Me, OMe or OPri; Y = N(Et), R = OPh, OMe or OCH2; Y = N(Me), R = OPri or OEt) leads to the ready formation of a product which on irradiation with ultraviolet light rapidly decarbonylates to the heptacarbonyl derivative [Fe2(μ-CO)(CO)6{μ-R2PYPR2}]. Treatment of the latter with a slight excess of the appropriate ligand results, under photochemical conditions, in the formation of the dinuclear pentacarbonyl complex [Fe2(μ-CO)(C))4{μ-R2PYPR2}2] but under thermal conditions in the formation of the mononuclear species [Fe(CO)3{R2PYPR2}]. Reaction of [Ru3(CO)12] with an equimolar amount of (RO)2PN(R′)P(OR)2 (R′ = Me, R = Pri or Et; R′ = Et, R = Ph or Me) under either thermal or photochemical conditions produces [Ru3(CO)10{μ-(RO)2PN(OR)2}] which reacts further with excess (RO)2PN(R′)P(OR)2 on irradiation with ultraviolet light to afford the dinuclear compound [Ru2(μ-CO)(CO4{μ-(RO)2PN(R′)P(OR)2}2]. The molecular structure of [Ru2(μ-CO)(CO)4{μ-(MeO)2PN(Et)P(OMe)2}2], which has been determined by X-ray crystallography, is described. 相似文献
39.
The fluorescence decay of the tertiary aliphatic animes trimethylamine (TMA), triethylamine (TEA) and tri-n-propylamine (TPA) in the vapour phase excited between 260 and 215 nm has been shown to consist of a single, wavelength-dependent, component when the first excited state is uniquely excited, but two components when the first and second excited states are simultaneously excited. This dual exponentiality persists at pressures as low as 10 mTorr, and it is argued that the two-component decay does not arise from collisional vibrational relaxation. 相似文献
40.