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161.
Isborn C Hrovat DA Borden WT Mayer JM Carpenter BK 《Journal of the American Chemical Society》2005,127(16):5794-5795
High-level electronic structure calculations have been used to study the factors contributing to the barriers to degenerate hydrogen-atom transfer (HAT) reactions. Understanding of these reactions is a prerequisite to the development of any more general theory of HAT reactions, and yet, the existing models for such reactions perform quite poorly when applied to even simple self-exchanges. The reasons behind these failures are elucidated in the present work. They include a near cancellation of bond-strength effects between reactant and transition state, as well as a strong dependence of the geometry of the transition state on the nature of the heavy atoms. 相似文献
162.
Organic crystals absorb hydrogen gas under mild conditions 总被引:2,自引:0,他引:2
Thallapally PK Lloyd GO Wirsig TB Bredenkamp MW Atwood JL Barbour LJ 《Chemical communications (Cambridge, England)》2005,(42):5272-5274
We have studied the hydrogen sorption on three well-known organic hosts that possess vacant lattice voids large enough to accommodate H2 molecules. 相似文献
163.
The development of a novel route for the synthesis of a new class of compounds is described. The first tripodal, tris-indole amines are prepared by straightforward routes. 相似文献
164.
165.
Clive E. Barnes John M. Brown Alan D. Fackerell Trevor J. Sears 《Journal of Molecular Spectroscopy》1982,92(2):485-496
Lines in the ν3 (“antisymmetric” stretch) fundamental of the NCO radical in the state were studied by CO laser magnetic resonance. The observations were assigned to P and R lines in the vibration-rotation band and lead to a precise determination of the vibrational interval and the anharmonic correction to the rotational constant: ν3 = 1920.60645(19) cm?1, α3 = 0.003338(21) cm?1. A single transition in the hot band (011)-(010), was detected. This observation is used to determine the origin of the hot band as 1907.11892(20) cm?1, i.e., the anharmonicity parameter x23 = ?13.48753(28) cm?1. 相似文献
166.
John R. Jones Trevor S. Walters 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1967,18(6):774-781
Résumé On fait une analyse de l'écoulement laminaire de liquides newtoniens dans des tuyaux cylindriques tournant autor d'un axe perpendiculaire à l'axe du tuyau, l'écoulement étant celui induit par un gradient de pression constant. On donne des calculs explicites dans les cas du luyau circulaire et du tuyau rectangulaire. 相似文献
167.
The diffusion coefficient for Fe in Y from Mössbauer experiments is several orders of magnitude lower than from bulk diffusion measurements. This can be explained by a combination substitution-interstitial diffusion mechanism. 相似文献
168.
An acid-catalysed rearrangement of the THP-ether of homoallylic alcohol gives ready access to an 0-protected derivative of 4-hydroxytetrahydropyran and thence by two further steps to provide a short and highly stereoselective route to the title spiroketal. 相似文献
169.
Crosslinks are introduced by γ irradiation into 1,2-polybutadiene while strained in uniaxial extension near Tg with stretch ratio λ0, thereby trapping a proportion of the entanglements originally present. The stress at any subsequent strain λ is accurately given by the sum σN + σx, where σN is the stress contributed by a trapped entanglement network with λ = 1 as reference and a Mooney–Rivlin stress-strain relation, and σx is that contributed by a crosslink network with λ = λ0 as reference and neo-Hookean stress-strain relation. The birefringence is accurately given as δn = ?NσN + ?xσx, where the ?'s are the respective stress-optical coefficients. From measurements at λ = λ0 where σx = 0, ?N can be determined separately. For polymer with 88% 1,2 microstructure, ?N and ?x are nearly equal and independent of irradiation dose, though strongly dependent on temperature. For polymer with (95–96)% 1,2, ?N and ?x are different (even opposite in sign) and dependent on dose. This behavior is associated with a side reaction of cyclization by the γ irradiation, which is inhibited by the 1,4 moiety in the polymer with lesser 1,2 content. It is responsible for residual birefringence in the state of ease (λ = λs) where σN = –σx and the stress is zero. 相似文献
170.
Trevor R. Griffiths S. V. J. Lakshman A. Varada Rajulu 《Journal of chemical crystallography》1984,14(6):559-564
The optical absorption spectrum of the octahedral moiety CoCl4(H2O)2 in single crystal [(CH3)3NH]CoCl3·2H2O has been studied at room and liquidair temperatures. The observed ambient bands at 6800, 16,300, and 19,000 cm–1 have been assigned, respectively, to the transitions4
T
1(F) 4
T
2(F),4
A
2(F), and4
T
1 (P). The crystal field parameters evaluated areD
q
=B=850 cm–1, andC=4.63B. At liquid-air temperatures the4
T
1(P) band is seen to split into the expected four components
7,
8,
8, and
6, due to spin-orbit coupling, and the coupling coefficient was computed to be 525 cm–1. 相似文献