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61.
Recent morphological studies have demonstrated a laminar (sheet) organization of ventricular myofibers. Multiaxial measurements
of orthotropic myocardial constitutive properties have not been reported, but regional distributions of three-dimensional
diastolic and systolic strains relative to fiber and sheet axes have recently been measured in the dog heart by Takayama et
al. [30]. A three-dimensional finite-deformation, finite element model was used to investigate the effects of material orthotropy
on regional mechanics in the canine left ventricular wall at end-diastole and end-systole. The prolate spheroidal model incorporated
measured transmural distributions of fiber and sheet angles at the base and apex. Compared with transverse isotropy, the orthotropic
model of passive myocardial properties yielded improved agreement with measured end-diastolic strains when: (1) normal stiffness
transverse to the muscle fibers was increased tangent to the sheets and decreased normal to them; (2) shear coefficients were
increased within sheet planes and decreased transverse to them. For end-systole, orthotropic passive properties had little
effect, but three-dimensional systolic shear strain distributions were more accurately predicted by a model in which significant
active systolic stresses were developed in directions transverse to the mean fiber axis as well as axial to them. Thus the
ventricular laminar architecture may give rise to anisotropic material properties transverse to the fibers with greater resting
stiffness within than between myocardial laminae. There is also evidence that intact ventricular muscle develops significant
transverse stress during systole, though it remains to be seen if active stress is also orthotropic with respect to the laminar
architecture.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
62.
Ashraf RS Kronemeijer AJ James DI Sirringhaus H McCulloch I 《Chemical communications (Cambridge, England)》2012,48(33):3939-3941
A novel thiophene substituted isoindigo and its copolymer with benzothiadiazole have been synthesized. The polymer with low lying LUMO energy levels exhibits excellent ambipolar behavior in field effect transistors with both hole and electron mobilities recorded over 0.1 cm(2) V(-1) s(-1). 相似文献
63.
Synthesis and morphology of asymmetric,alkyne-functionalised pentacene and 2-fluoroanthradithiophene
Craig M.S. Combe David T. James Jessica Wade Andrew J.P. White Ji-Seon Kim Iain McCulloch 《Tetrahedron letters》2013
The performance of 6,13-(bis-triisopropylsilylethynyl)pentacene (TIPS-pentacene) and 1,1′-difluoro-5,11-(bis-triethylsilyl)acetylene-anthra[2,3-b:6,7-b′]dithiophene (TES-FADT) is highly dependent on the morphology enforced by their alkyl groups, with only triisopropylsilylethynyl and triethylsilylethynyl producing viable transistor devices, respectively. Asymmetric triisopropylsilylacetylene- and triethylsilylacetylene-functionalised pentacene and 2-fluoroanthradithiophene were synthesised to study the effects a small change to the solubilising groups has on the thin film morphology. 相似文献
64.
Kasztelan C Trotzky S Chen YA Bloch I McCulloch IP Schollwöck U Orso G 《Physical review letters》2011,106(15):155302
We simulate numerically the dynamics of strongly correlated bosons in a two-leg ladder subject to a time-dependent energy bias between the two chains. When all atoms are initially in the leg with higher energy, we find a drastic reduction of the interchain particle transfer for slow linear sweeps, in quantitative agreement with recent experiments. This effect is preceded by a rapid broadening of the quasimomentum distribution of atoms, signaling the presence of a bath of low-energy excitations in the chains. We further investigate the scenario of quantum quenches to fixed values of the energy bias. We find that for a large enough density the momentum distribution relaxes to that of an equilibrium thermal state with the same energy. 相似文献
65.
66.
DR. E. W. J. Mitchell 《Contemporary Physics》2013,54(3):217-222
The accurate measurement of the thermal conductivity of metals still poses considerable experimental difficulty. The reasons for this, and the main ways in which the problem has been approached, are summarized. A detailed examination of the development in technique and methods of measurement shows that while most of the steady-state methods introduced over 50 years ago are still being improved, the emphasis in the last few years has been on the development of methods which give more rapid results, particularly at high temperatures. 相似文献
67.
Chad R. Snyder R. Joseph Kline Dean M. DeLongchamp Ryan C. Nieuwendaal Lee J. Richter Martin Heeney Iain McCulloch 《Journal of Polymer Science.Polymer Physics》2015,53(23):1641-1653
Semiconducting polymers form a variety of phases and mesophases that respond differently to postdeposition solvent or thermal treatments. Here it is shown that classification of these materials into their appropriate mesophases can be a useful tool to optimize their thermal postdeposition treatments. Calorimetry is used to quantify differences between materials having similar molecular structures, using a well‐established framework based on the kinetics and thermodynamics of phase changes. By way of example, this classification scheme is used to identify differences in three polymers, poly(3‐hexylthiophene‐2,5‐diyl) and two isomeric bithiophene–thienothiophene copolymers. It is demonstrated that poly(3‐hexylthiophene) is a “normal” polymer crystal and that the two bithiophene–thienothiophene copolymers have liquid crystalline phases. The different phase structure is notable in light of the molecular similarity of the three polymers and has an impact on the thermal postprocessing conditions that maximize field effect charge carrier mobility in thin film transistor devices. Strong superheating effects are demonstrated for the two bithiophene–thienothiophene copolymers and the impact on annealing is demonstrated using grazing incidence X‐ray diffraction. Some suggestions are also put forth for what post‐processing should be employed for each class of polymer. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1641–1653 相似文献
68.
Michael A. Quilliam P. Greig Sim Archibald W. McCulloch A. Gavin McInnes 《International journal of environmental analytical chemistry》2013,93(3):139-154
Abstract A recent outbreak of poisoning resulting from the consumption of cultured blue mussels (Mytilus edulis L.) from a localized area in Eastern Canada has been attributed to the presence of domoic acid (1), a relatively rare neurotoxic amino acid, previously found only in some algae of the family Rhodomelaceae. Studies on aqueous extracts of shellfish tissue indicated that the toxin and several of its isomers could be separated (and isolated in sufficient amounts for subsequent structural identification) by reversed-phase high-performance liquid chromatography (HPLC) with ultraviolet (UV) diode array detection (DAD). Aqueous acetonitrile containing 0.1% v/v trifluoroacetic acid was used as mobile phase. As the retention time and characteristic UV absorption spectrum of 1 (λmax = 242 nm) permit unequivocal identification, the HPLC-DAD procedure was refined with a microbore column to provide a rapid (5 min), sensitive (0.3 ng detection limit) and reproducible assay method for the determination of 1 in shellfish tissue. Extraction was accomplished by boiling homogenized shellfish tissue for 5 min with distilled water. Extracts were taken through an octadecylsilica solid phase extraction clean-up prior to HPLC. This method has been applied to a variety of shellfish and phytoplankton samples. BRIEF Reversed-phase HPLC with ultraviolet diode array detection was used to analyze shellfish tissue and phytoplankton extracts for domoic acid. A rapid (5 min) and sensitive (0.3 ng detection limit) assay is presented. 相似文献
69.
70.