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921.
Brandon Lindley Eddie Lee Howell Breannan D. Smith Gregory J. Rubinstein M. Gregory Forest Sorin M. Mitran David B. Hill Richard Superfine 《ournal of non Newtonian Fluid Mechanics》2009,156(1-2):112-120
We revisit a classical topic: response functions of viscoelastic layers in large amplitude oscillatory shear. Motivated by questions concerning protective biological layers, we focus on boundary stresses in a parallel plate geometry with imposed oscillatory strain or stress. These features are gleaned from resolution and analysis of coupled standing waves of deformation and stress. We identify a robust non-monotone variation in boundary stress signals with respect to all experimental controls: viscoelastic moduli of the layer, layer thickness, and driving frequency. This structure of peaks and valleys in boundary values of shear and normal stress indicates redundant mechanisms for stress communication (by tuning to the peaks) and stress filtering (by tuning to the valleys). In this paper, we first restrict to a single-mode non-linear Maxwell model for the viscoelastic layer, where analysis renders a transparent explanation of the phenomena. We then consider a Giesekus constitutive model of the layer, where analysis is supplanted by numerical simulations of coupled non-linear partial differential equations. Parametric studies of wall stress values from standing waves confirm persistence of the Maxwell model phenomena. The analysis and simulations rely on and extend our recent studies of shear waves in a micro parallel plate rheometer [S.M. Mitran, M.G. Forest, L. Yao, B. Lindley, D. Hill, Extenstions of the Ferry shear wave model for active linear and nonlinear microrheology, J. Non-Newtonian Fluid Mech. 154 (2008) 120–135; D.B. Hill, B. Lindley, M.G. Forest, S.M. Mitran, R. Superfine, Experimental and modeling protocols from a micro-parallel plate rheometer, UNC Preprint, 2008]. 相似文献
922.
Julie A. Leary Matthew R. Schenauer Raluca Stefanescu Armann Andaya Brandon T. Ruotolo Carol V. Robinson Konstantinos Thalassinos James H. Scrivens Masaaki Sokabe John W. B. Hershey 《Journal of the American Society for Mass Spectrometry》2009,20(9):1699-1706
The methodology developed in the research presented herein makes use of chaotropic solvents to gently dissociate subunits
from an intact macromolecular complex and subsequently allows for the measurement of collision cross section (CCS) for both
the recombinant (R-eIF3k) and solvent dissociated form of the subunit (S-eIF3k). In this particular case, the k subunit from
the eukaryotic initiation factor 3 (eIF3) was investigated in detail. Experimental and theoretical CCS values show both the
recombinant and solvent disrupted forms of the protein to be essentially the same. The ultimate goal of the project is to
structurally characterize all the binding partners of eIF3, determine which subunits interact directly, and investigate how
subunits may change conformation when they form complexes with other proteins. Research presented herein is the first report
showing retention of solution conformation of a protein as evidenced by CCS measurements of both recombinant and solvent disrupted
versions of the same protein. 相似文献
923.
Flow transition in dual bell nozzles 总被引:2,自引:1,他引:1
The dual bell nozzle is a concept of altitude adaptive nozzles. The flow adapts to the altitude by separation at the wall
inflection at low altitude, and full flowing at high altitude. To understand the phenomenology of the flow by the transition
from sea-level mode to high altitude mode, a series of tests have been made at the cold flow test bench P6.2 at DLR Lampoldshausen.
A dual bell nozzle have been successively shorten and driven in the same conditions for each length. Hence it was possible
to observe the flow in the vicinity of the wall inflection using Schlieren optics. Furthermore this study yields the influence
of the length ratio between basis and extension on the transition conditions.
相似文献
相似文献
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925.
926.
927.
Marc Harris Kenneth Houser Johanna Scarino Scott Wallace Brandon Arndt Amy Smith Gary Romberger Allix Sanders 《Journal of inclusion phenomena and macrocyclic chemistry》2008,60(1-2):153-161
Two novel ethylene oxide-bridged bipyridine oligomers were synthesized that contain host pockets with four (1) or six (2) oxygen donor atoms and a pyridyl nitrogen donor. The alkali picrate extracting ability and selectivity of these free ligands
was investigated using a liquid–liquid dichloromethane–water extraction study. Both open-chain oligomer frameworks display
unexpectedly high extraction efficiency (EE) values for specific guest ions (EE = 57% Na+ extracted by 1, and EE = 39% Cs+ extracted by 2). These extraction values are comparable to macrocyclic analogues and their ion selectivities follow the ‘same-fit’ concept
that has been extensively reported for fixed pocket systems. The shorter chain oligomer (1) binds ions in the series (Na+ > K+ > Cs+), while the larger oligomer (2) binds ions in the reverse order (Cs+ > K+ > Na+). Formation of the host–guest ligand–ion complexes were verified by 1H NMR spectroscopy and MALDI-TOF mass spectrometry experiments. A Job’s plot analysis based on UV spectral data also supported
the 1:1 (oligomer to ion) complexation observed in the MALDI mass spectra. 相似文献
928.
929.
930.
We investigate when it is possible to globally diagonalize an Einstein metric of cohomogeneity-one under the action of a compact connected Lie group G with isotropy subgroup K. Restricting our attention to the non-monotypic case in which cohomogeneity-one metrics are not automatically diagonalizable, we make use of a subset of the ODEs of the Einstein condition to globally diagonalize the Einstein metric in certain cases. The program we use is inspired by a result well-known to relativists which states that Einstein metrics must be diagonalizable in the Bianchi IX case. We present a full classification of all the cohomogeneity-one metrics on which this method can be used. 相似文献