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721.
Experimental liquid—liquid equilibrium data are reported for the systems acetonitrile—acetone—cyclohexane at 318.15 K and acetonitrile—methyl acetate—cyclohexane at 313.15 K. Two modified forms of the NRTL equation proposed by Renon are presented by substituting local surface fractions for local mole fractions and further by including Guggenheim's combinatorial entropy for athermal mixtures whose molecules differ in size and shape. The resultant equations involve three adjustable parameters and are extended to multicomponent systems without adding ternary (or higher) parameters. Calculated results of vapor—liquid and liquid—liquid equilibria for typical binary and ternary mixtures are presented. 相似文献
722.
Tokio Yamabe Tatsuhiro Aoyagi Shinichi Nagata Hideki Sakai Kenichi Fukui 《Chemical physics letters》1974,28(2):182-185
The electronic structure of H3S+ is examined by ab initio MO calculations (STO 3G) and is compared with those of other XH3 type molecules. The barrier to pyramidal inversion and the proton affinity of H2S are calculated to be 34.8 and 225.05 kcal/mol respectively. Computations are made with respect to a model A3S+ which is employed to discuss the barrier to pyramidal inversion of H3S+, where A corresponds to an electromagnetive substituent or an electron donating one. 相似文献
723.
The absolute cross section for photodissociation of Ar2N 2 + was measured as a function of wavelength in the 470–550 nm range. A structureless broad band was observed; the cross section has a maximum of ~ 210 × 10?18 cm2 at ~ 500 nm. The measurement of the photofragment time-of-flight spectrum shows that(1) N 2 + , Ar+ and Ar 2 + are produced in the photodissociation of Ar2N 2 + in the wavelength range studied, and that(2) the observed visible absorption band is ascribable to a parallel-type transition of Ar2N 2 + , which possibly retains a linear geometry. 相似文献
724.
Motoyama Y Koga Y Kobayashi K Aoki K Nishiyama H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(13):2968-2975
The rhodium complex prepared in situ by simply mixing [[RhCl(c-octene)2]2] and [(Phebox)SnMe3] (1) (Phebox = 2,6-bis(oxazolinyl)phenyl) was found to serve as an efficient catalyst for the asymmetric Michael addition of alpha-cyanopropionates (4) to acrolein under mild and neutral conditions. In the present catalytic system, both the temperature of catalyst preparation and the order of the addition of the substrates were very important for the catalytic efficiency and enantioselectivity. Detailed mechanistic studies of this catalytic system revealed that the [(Phebox)RhIII(SnMe3)Cl] complex (9), generated by oxidative addition of [[RhCl(c-octene)2]2] to 1, is an active catalyst and the turnover number (TON) of the present actual catalyst existing in a reaction mixture is greater than 10,000. The obtained (R) stereochemistry of the Michael adducts 5 can be explained by N-bonded enol intermediates C', which are formed by enolization of 4 bound to the Lewis acidic rhodium complex 9. We also found that the active catalyst 9 gradually decomposed in the presence of the remaining [[RhCl(c-octene)2]2] in the reaction mixture to form the catalytically nonactive [(Phebox)RhCl2] fragment A, whose structure was characterized by an X-ray crystallographic study after converting to the tBuNC complex 10. 相似文献
725.
Mitsuru Yoshioka Teruji Tsuji Shoichiro Uyeo Sadao Yamamoto Tsutomu Aoki Yasuhiro Nishitani Sachio Mori Hisao Satoh Yoshinori Hamada Hiroyuki Ishitobi Wataru Nagata 《Tetrahedron letters》1980,21(4):351-354
Stereocontrolled and industrially feasible synthesis of a new antibiotic and related derivatives, which is characterized by using all the carbon atoms of the penicillin skeleton, is described. 相似文献
726.
Recently various models for spatially chaotic structures have been proposed. We study the diffraction patterns produced by plane chaotic waves incident on one-dimensional chaotic point scatterers. The spacing between the scatterers and the dynamics of the incident wave are given by a logistic map or standard map. We find a sharp diffraction peak when the incident dynamics is produced by the same map as the structure of the spatial configuration. The diffraction pattern is symmetric about the incident direction only if the map dynamics is invertible. Diffraction patterns with chaotic incident waves have a large signal-to-noise ratio and are well suited for pattern identification. We discuss possible applications to the scattering of microwaves from aperiodic structures. (c) 1997 American Institute of Physics. 相似文献
727.
S. Nagata S. Yasuzuka Y. Kato T. Hagino N. Matsumoto N. Kijima S. Ebisu 《Czechoslovak Journal of Physics》1996,46(5):2425-2426
A new thiospinel CuIr2S4 exhibits a metal-insulator (M-I) transition at 226 K, while CuRh2S4 shows a superconducting transition at 4.70 K. We present a systematic study of electrical and magnetic properties of Cu(Ir1?x Rh x )2S4. TheM-I transition of CuIr2S4 is accompanied by a structural phase transition from tetragonal symmetry in insulating phase to cubic symmetry in high temperature metallic phase. With increasing Rh contentx, the sharpM-I transition shifts to lower temperature forx≦0.10. The samples show semiconductive behavior for 0.10≦0.30 between 4.2 and 300 K, and recover the metallic state forx≧0.50. The superconducting transition may occur for very close tox=1.00. Magnetic susceptibility shows the jump at theM-I transition temperature and the variation ofx leads to a systematic change of the magnetic susceptibilities, which is consistent with the electrical characteristic feature. 相似文献
728.
Izumi H. Asahi K. Ueno H. Okuno H. Sato H. Nagata K. Hori Y. Adachi M. Aoi N. Yoshida A. Liu G. Fukunishi N. Ishihara M. 《Hyperfine Interactions》1996,97(1):509-517
The experimental study of nuclear moments of several neutron-rich nuclei, using the phenomenon of ejectile spin polarization in the projectile fragmentation reaction, is reported. The spin-polarized fragments14B and15B were produced in the fragmentation of18O projectiles on a Nb target at 64.7 MeV/u. They were implanted into a Mg single crystal, and the quadrupole momentsQ were determined by the-NMR method. The results, ¦Q(14B)¦ =29.84 ±0.75 mb and ¦Q(15B)¦=38.01 ±1.08 mb, are compared with theoretical models. Shell model calculations in a 0 model space, using effective charges commonly accepted in this mass region, predict values about 40% larger than the experimentalQ(15B). Agreement is obtained when a much smaller effective charge for neutrons is employed. The method was also applied to the measurement of the magnetic moments of17N and17B. The result reveals an important contribution of configurations with excess neutrons coupled to formJ
=2+. 相似文献
729.
730.