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991.
Giuliano Alagona Caterina Ghio Alessandro Giolitti Susanna Monti 《Theoretical chemistry accounts》1999,101(1-3):143-150
Several histidine-tryptophan complexes (either stacked or T-shaped), derived from the crystal structures available in the
Brookhaven Protein Data Bank, have been examined with molecular mechanics (MM), using the Tripos force field with Gasteiger-Hückel
charges, whose trend was found to be analogous to the AMBER or CHARMM ones. The MM results were compared to the ab initio
MP2 results, with and without counterpoise (CP) correction, previously obtained using extended basis sets on 5-methylimidazole
and indole as model systems. MM seems to underestimate the interaction energy between the two monomers when compared to the
uncorrected MP2 results, while the agreement is much better after including the CP correction at the MP2 level in all cases.
MM was thus used to qualitatively analyse the dependence of the stacking energy on the ring rotation at a variable distance
and ring centroid displacement for these systems, while keeping the rings in parallel planes. An analogous study was carried
out for a T-shaped adduct.
Received: 24 March 1998 / Accepted: 3 September 1998 / Published online: 1 February 1999 相似文献
992.
The present paper begins by deriving an instantaneous formulation for the backward-looking (reinforcement based learning) satisfaction balance model of Gray and Tallman (1984). This model is then used to generate interactional data from four simulated agents in a network interaction experiment. Because this initial model does not generate stable interaction structures in the network experiment, it is altered step by step in the direction of a forward-looking (agent with goals) model that has been shown to generate such stable interaction structures. The purpose of the modifications are to learn what aspects of the forward-looking model are needed to evolve a stable interaction structure, and to learn how these aspects may be incorporated into a model that remains essentially reinforcement based. 相似文献
993.
The contribution of solvation energy to guiding molecular recognition for six rigid protein‐peptide systems bad been evaluated by the variation in the number of the identified native‐like configurations and in the driving force of specific interaction resulting from the addition of the explicit solvation term in the force field function. The AMBER force field energy and the total energy including the force field energy and the WZS solvation energy were calculated for sampled configurations. The results obtained by the calculations of both force field and total energies were compared with each other. It suggests that the contribution of solvation energy is important to guiding the specific recognition of the systems in which the ligands possess larger hydrophobic or aromatic residues while the protein receptors provide the active surfaces with hydrophobic property. 相似文献
994.
Thestudiesofpolymersolutionpropertiesfromdilatetoconcentratedsolutionbyfluorescencetechniquehaveattractedmoreattentionsinrecentdecadesl'2.InordertoinvestigateintrachainandinterchainilltCractionsindilutesolutionregion,pyrenewasusedaslabelsattachedtopolystyrene,whichwasintenselyfluorescentwithalongfluorescentlifetime3.Inthepresentwork,thepolystyreneattachedwithpyrenylgroupshadanunfavourablestrUcturetothenearestneighborexcimerformationwiththepyrenylgroupsseparatedbymorethanthreeatomsalongthechain… 相似文献
995.
We study the one-loop effective potentials of the four-dimensional Lifshitz scalar field theory with the particular anisotropic scaling z=2, and the mass and the coupling constants renormalization are performed whereas the finite counterterm is just needed for the highest order of the coupling because of the mild UV divergence. Finally, we investigate whether the critical temperature for the symmetry breaking can exist or not in this approximation. 相似文献
996.
Régis Brugiere et Pierre Lucasson 《辐射效应与固体损伤》2013,168(1):55-57
The nature of the electron bombarded aluminium electrical recovery process has been studied by combining quenches with irradiations. Measured Frenkel pair formation rates per incident electrons as well as annealing kinetics emphasize the role of impurity interstitial trapping. 相似文献
997.
John P. Lehoczky 《The Journal of mathematical sociology》2013,37(2):139-157
A class of models called interactive Markov chains is studied in both discrete and continuous time. These models were introduced by Conlisk and serve as a rich class for sociological modeling, because they allow for interactions among individuals. In discrete time, it is proved that the Markovian processes converge to a deterministic process almost surely as the population size becomes infinite. More importantly, the normalized process is shown to be asymptotically normal with specified mean vector and covariance matrix. In continuous time, the chain is shown to converge weakly to a diffusion process with specified drift and scale terms. The distributional results will allow for the construction of a likelihood function from interactive Markov chain data, so these results will be important for questions of statistical inference. An example from manpower planning is given which indicates the use of this theory in constructing and evaluating control policies for certain social systems. 相似文献
998.
Geometry optimization was performed for the ground states of FeCO, Fe(CO)2, and Fe(CO)3 at various levels of ab initio calculations, and the bond lengths and dissociation energies obtained were in reasonable agreement
with experimental results. The nature of bonding was studied for these molecules using a complete-active-space self-consistent-field
method. From the Mulliken population analysis, it was found that the traditional donation and back donation mechanism is valid
for these molecules, including Fe(CO)3, which has a pyramidal structure.
Received: 27 September 1999 / Accepted: 13 January 2000 / Published online: 19 April 2000 相似文献
999.
1000.