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51.
52.
It is widely accepted that liquid water structure is comprised of two closely interweaved components; i.e. tetrahedral (low density) and hexagonal (high density) structures. The relative amount of these components is temperature and pressure dependent. We propose an order parameter, based on the radial distribution function, that quantifies the relative structural composition at any defined temperature and pressure, thus establishing the crossover point in structural dominance. At 300 K this point lies close to 2 kbar, pressure at which water looses most of its ‘anomalous’ properties. 相似文献
53.
S McCarthy 《Magnetic resonance imaging》1986,4(1):59-66
Magnetic resonance imaging of the female pelvis permits visualization of soft tissue structure previously unseen with other radiological techniques. The internal architecture of the corpus uterus, cervix and vagina are directly visualized in any plane. Furthermore, the hormonal environment of the female can be indirectly determined via assessment of the MR appearance of the uterus. Similarly, the complex changes which occur during pregnancy, such as cervical effacement and the relationship of internal os, fetal part and placenta, are easily documented. MR pelvimetry enables fast, safe depiction of the birth canal. Finally, the demonstrated fetal anatomy may prove particularly useful in the evaluation of intrauterine growth retardation and anomalies indeterminate by ultrasound. 相似文献
54.
Steven G. Krantz John E. McCarthy Harold R. Parks 《Journal of Mathematical Analysis and Applications》2006,316(1):87-109
We study the centroid of a simplex in space. Primary attention is paid to the relationships among the centroids of the different k-skeletons of a simplex in n-dimensional space. We prove that the 0-dimensional skeleton and the n-dimensional skeleton always have the same centroid. The centroids of the other skeleta are generically different (as we prove), but there are remarkable instances where they coincide in pairs. They never coincide in triples for regular pyramids. 相似文献
55.
Hughes MS McCarthy JE Marsh JN Arbeit JM Neumann RG Fuhrhop RW Wallace KD Znidersic DR Maurizi BN Baldwin SL Lanza GM Wickline SA 《The Journal of the Acoustical Society of America》2007,121(6):3542-3557
Qualitative and quantitative properties of the finite part, H(f), of the Shannon entropy of a continuous waveform f(t) in the continuum limit are derived in order to illuminate its use for waveform characterization. Simple upper and lower bounds on H(f), based on features of f(t), are defined. Quantitative criteria for a priori estimation of the average-case variation of H(f) and log E(f), where E(f) is the signal energy of f(t) are also derived. These provide relative sensitivity estimates that could be used to prospectively choose optimal imaging strategies in real-time ultrasonic imaging machines, where system bandwidth is often pushed to its limits. To demonstrate the utility of these sensitivity relations for this application, a study designed to assess the feasibility of identification of angiogenic neovasculature targeted with perfluorocarbon nanoparticles that specifically bind to alpha(v)beta3-integrin expression in tumors was performed. The outcome of this study agrees with the prospective sensitivity estimates that were used for the two receivers. Moreover, these data demonstrate the ability of entropy-based signal receivers when used in conjunction with targeted nanoparticles to elucidate the presence of alpha(v)beta3 integrins in primordial neovasculature, particularly in acoustically unfavorable environments. 相似文献
56.
B.A. Goeckner D.R. Helmich T.A. McCarthy J.M. Arinez T.E. Peard J.E. Peters M.Q. Brewster R.O. Buckius 《Experimental Thermal and Fluid Science》1992,5(6):848-860
Experiments were conducted using porous ceramic inserts to enhance the radiative heat transfer from natural gas flames in a straight-through radiant tube burner. The performance of the radiant tube burner with partially stabilized zirconia and silicon carbide inserts is compared to a baseline case of no inserts at three levels of combustion air preheat. Spectral intensities, temperatures within the radiant tube burner, tube wall temperatures, and exhaust temperatures were measured to determine the effectiveness of the enhanced heat transfer due to the inserts. Exhaust emission constituents were also measured to determine the effect that the inserts have on exhaust products. NOx emissions are reduced by up to 30% with the inserts. The silicon carbide inserts have higher spectral intensities and total radiative energy transfer than partially stabilized zirconia inserts. Both inserts have enhanced radiant heat transfer compared to the no-insert configuration, with the radiative enhancement due to inserts as great as five times that of the no-insert configuration. The net result is increased tube wall temperatures and decreased exhaust temperatures with the ceramic inserts. 相似文献
57.
One-dimensional pulse propagation in composite materials modelled as interpenetrating solid continua
Matthew F. McCarthy 《Wave Motion》1982,4(3):221-242
Modulated simple wave theory is used to study the propagation of one dimensional, finite amplitude, high frequency pulses in composites which are modelled as interpenetrating solid continua with two identifiable constituents. The equations which govern the propagation of high frequency pulses are derived and their properties are studied in detail. Particular attention is paid to small amplitude high frequency pulses and results for pulses propagating into composites of a rather general nature are presented. The special results which hold for pulses which propagate into uniform regions are discussed in detail. The influence of the structure of the composite on pulse propagation is also assessed by examining pulse propagation in a number of different types of composite. 相似文献
58.
59.
McCarthy A 《Chemistry & biology》2011,18(8):937-938
60.
Coordinative immobilization of functionalized tetraphenylethylene within rigid porous metal-organic frameworks (MOFs) turns on fluorescence in the typically non-emissive tetraphenylethylene core. The matrix coordination-induced emission effect (MCIE) is complementary to aggregation-induced emission. Despite the large interchromophore distances imposed by coordination to metal ions, a carboxylate analogue of tetraphenylethylene anchored by Zn(2+) and Cd(2+) ions inside MOFs shows fluorescence lifetimes in line with those of close-packed molecular aggregates. Turn-on fluorescence by coordinative ligation in a porous matrix is a powerful approach that may lead to new materials made from chromophores with molecular rotors. The potential utility of MCIE toward building new sensing materials is demonstrated by tuning the fluorescence response of the porous MOFs as a function of adsorbed small analytes. 相似文献