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81.
Numerical Simulation Studies of the Long-term Evolution of a CO<Subscript>2</Subscript> Plume in a Saline Aquifer with a Sloping Caprock 总被引:1,自引:0,他引:1
We have used the TOUGH2-MP/ECO2N code to perform numerical simulation studies of the long-term behavior of CO2 stored in an aquifer with a sloping caprock. This problem is of great practical interest, and is very challenging due to
the importance of multi-scale processes. We find that the mechanism of plume advance is different from what is seen in a forced
immiscible displacement, such as gas injection into a water-saturated medium. Instead of pushing the water forward, the plume
advances because the vertical pressure gradients within the plume are smaller than hydrostatic, causing the groundwater column
to collapse ahead of the plume tip. Increased resistance to vertical flow of aqueous phase in anisotropic media leads to reduced
speed of up-dip plume advancement. Vertical equilibrium models that ignore effects of vertical flow will overpredict the speed
of plume advancement. The CO2 plume becomes thinner as it advances, but the speed of advancement remains constant over the entire simulation period of
up to 400 years, with migration distances of more than 80 km. Our simulations include dissolution of CO2 into the aqueous phase and associated density increase, and molecular diffusion. However, no convection develops in the aqueous
phase because it is suppressed by the relatively coarse (sub-) horizontal gridding required in a regional-scale model. A first
crude sub-grid-scale model was developed to represent convective enhancement of CO2 dissolution. This process is found to greatly reduce the thickness of the CO2 plume, but, for the parameters used in our simulations, does not affect the speed of plume advancement. 相似文献
82.
Karsten Krohn Ishtiaq Ahmed Dietmar Gehle Mohammed Al Sahli 《Journal of carbohydrate chemistry》2013,32(2):64-77
Chiral building blocks for macrolides and related natural products are obtained from 1,6-anhydrosugars by conversion of the bicyclic acetals 2 or 12 into the open chain chiral 1,3-dithianes 6 and 13. Branched precursors can be obtained by opening of the ?erný epoxide 1 with the 1,3-dithiane anion to yield 7, followed by ring opening with 1,3-propanedithiol to the bis-1,3-dithiane 8. 相似文献
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The purpose of this note is to exhibit some simple and basic constructions for smooth compact transformation groups, and some of their most immediate applications to geometry. 相似文献
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Alexandria N. Bone Chelsea N. Widener Duncan H. Moseley Zhiming Liu Zhengguang Lu Dr. Yongqiang Cheng Dr. Luke L. Daemen Dr. Mykhaylo Ozerov Prof. Joshua Telser Prof. Komalavalli Thirunavukkuarasu Dr. Dmitry Smirnov Samuel M. Greer Prof. Stephen Hill Dr. J. Krzystek Dr. Karsten Holldack Azar Aliabadi Dr. Alexander Schnegg Prof. Kim R. Dunbar Prof. Zi-Ling Xue 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(43):11110-11125
Large separation of magnetic levels and slow relaxation in metal complexes are desirable properties of single-molecule magnets (SMMs). Spin-phonon coupling (interactions of magnetic levels with phonons) is ubiquitous, leading to magnetic relaxation and loss of memory in SMMs and quantum coherence in qubits. Direct observation of magnetic transitions and spin-phonon coupling in molecules is challenging. We have found that far-IR magnetic spectra (FIRMS) of Co(PPh3)2X2 ( Co-X ; X=Cl, Br, I) reveal rarely observed spin-phonon coupling as avoided crossings between magnetic and u-symmetry phonon transitions. Inelastic neutron scattering (INS) gives phonon spectra. Calculations using VASP and phonopy programs gave phonon symmetries and movies. Magnetic transitions among zero-field split (ZFS) levels of the S=3/2 electronic ground state were probed by INS, high-frequency and -field EPR (HFEPR), FIRMS, and frequency-domain FT terahertz EPR (FD-FT THz-EPR), giving magnetic excitation spectra and determining ZFS parameters (D, E) and g values. Ligand-field theory (LFT) was used to analyze earlier electronic absorption spectra and give calculated ZFS parameters matching those from the experiments. DFT calculations also gave spin densities in Co-X , showing that the larger Co(II) spin density in a molecule, the larger its ZFS magnitude. The current work reveals dynamics of magnetic and phonon excitations in SMMs. Studies of such couplings in the future would help to understand how spin-phonon coupling may lead to magnetic relaxation and develop guidance to control such coupling. 相似文献
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Ohne Zusammenfassung 相似文献
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Replacing the backbone amide function by a heterocyclic bioisostere, [3+2] azide-alkyne cycloaddition has been applied for the construction of biologically relevant peptidomimetics. Starting from aminoalkynoates, triazole formation was accomplished by addition of hydrazoic acid. NMR studies displayed that the newly developed 4,5-triazolopeptides, which incorporate a biomimetic triazole NH-function as polar constraint element, showed a substantially higher tendency to form a cis-prolyl-geometry than a comparable native peptide sequence. 相似文献