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41.
42.
马氏定律与哈勃定律的辨析 总被引:2,自引:2,他引:0
本文从理论,实验上论证了“马氏(红移)定律”,同时指出所谓“退行速度Vr”或“星系红移”与“星系间的距离”无必须的关系,从这个意义上来说,哈勃定律是错误的。 相似文献
43.
Dongmei Guo 《Optics Communications》2011,284(24):5766-5769
A new, to the best of our knowledge, signal processing method based on quadrature demodulation technique is presented for laser diode self-mixing interferometry(LDSMI) displacement sensor. Phase modulation of the laser beam is obtained by an electro-optic modulator (EOM) in the external cavity. Detection of the target's displacement can be easily achieved by sampling the interference signal at those times which satisfied certain conditions. The major advantage of the technique is that it does not involve any complicated calculation and insensitive to the sampling error. Experimental results show that the proposed method can effectively improve the displacement measurement resolution of the laser diode self-mixing displacement sensor to a few nanometers. 相似文献
44.
N.M.P. Pinto O. Frazo J.M. Baptista J.L. Santos 《Optics and Lasers in Engineering》2006,44(8):771-778
A quasi-distributed displacement sensor for structural monitoring using an optical time domain reflectometer is demonstrated. Four displacement sensing heads are placed along a standard single mode optical fibre in several locations with different intervals. Their configurations introduce power loss through the decrease of their fibre loop radius when displacement is applied. The decrease of the light intensity with displacement variation is reported. Losses of 9 dB for a 120 mm displacement with a sensitivity of 0.027 dB/mm are reported. The quasi-distributed configuration is able to address sensors with 1 m distance resolution between them. 相似文献
45.
基于悬臂梁结构的光纤光栅位移传感研究 总被引:25,自引:4,他引:21
本文提出了一种基于光纤光栅和悬臂梁结构的新型位移传感方案,并给出了实验结果。本传感系统结构简单,测量范围大(大于20mm),线性好(0.9991),抗电磁干扰,信噪比高,并可实现在线监测。 相似文献
46.
Most chromatographic processes involve separation of two or more species, so development of a simple, accurate multicomponent chromatographic model can be valuable for improving process efficiency and yield. We consider the case of breakthrough chromatography, which has been considered in great depth for single-component modeling but to a much more limited degree for multicomponent breakthrough. We use the shrinking core model, which provides a reasonable approximation of particle uptake for proteins under strong binding conditions. Analytical column solutions for single-component systems are extended here to predict binary breakthrough chromatographic behavior for conditions under which the external transport resistance is negligible. Analytical results for the location and profile of displacement effects and expected breakthrough curves are derived for limiting cases. More generally, straightforward numerical results have also been obtained through simultaneous solution of a set of simple ordinary differential equations. Exploration of the model parameter space yields results consistent with theoretical expectations. Additionally, both analytical and numerical predictions compare favorably with experimental column breakthrough data for lysozyme-cytochrome c mixtures on the strong cation exchanger SP Sepharose FF. Especially significant is the ability of the model to predict experimentally observed displacement profiles of the more weakly adsorbed species (in this case cytochrome c). The ability to model displacement behavior using simple analytical and numerical techniques is a significant improvement over current methods. 相似文献
47.
A nanogold-quenched fluorescence duplex probe has been developed for lighting up homogenous hybridization assays. This novel
probe is constructed from two strands of different lengths, and labeled by nanogold and a fluorophore at the long-strand 5′-end
and the short-strand 3′-end, respectively. The two tags are in close contact, resulting in complete quenching of the probe
fluorescence. If perfectly complemented to the nanogold-labeled strand, a long target oligonucleotide would displace the short
fluorophore-labeled strand, and as a result, restore the fluorescence. By using nanogold in the probe, an extremely high quenching
efficiency (99.1%) and removal of free fluorophore-labeled strand is achieved. The signal-to-noise ratio and the detection
limit (50 pmol L−1) of homogenous assays are therefore improved significantly, in comparison with similar probes using organic acceptors. Moreover,
the probe has a great inhibition effect on hybridization to a mismatched oligonucleotide. This effect provides the assay with
a high specificity, and particularly the assay has great potential in applications for discriminating variations in sequences.
The assay sensitivity could be markedly enhanced by using fluorescent materials in the signal strand that are brighter and
not quenched by nucleobases. 相似文献
48.
The present paper concentrates on structure and micro-mechanical properties of the helium-implanted layer on titanium treated by plasma-based ion implantation with a pulsed voltage of −30 kV and doses of 3, 6, 9 and 12 × 1017 ions/cm2, respectively. X-ray photoelectron spectroscopy and transmission electron microscopy are employed to characterize the structure of the implanted layer. The hardnesses at different depths of the layer were measured by nano-indentation. We found that helium ion implantation into titanium leads to the formation of bubbles with a diameter from a few to more than 10 nm and the bubble size increases with the increase of dose. The primary existing form of Ti is amorphous in the implanted layer. Helium implantation also enhances the ingress of O, C and N and stimulates the formations of TiO2, Ti2O3, TiO, TiC and TiN in the near surface layer. And the amount of the ingressed oxygen is obviously higher than those of nitrogen and carbon due to its higher activity. At the near surface layer, the hardnesses of all implanted samples increases remarkably comparing with untreated one and the maximum hardness has an increase by a factor of up to 3.7. For the samples implanted with higher doses of 6, 9 and 12 × 1017 He/cm2, the local displacement bursts are clearly found in the load-displacement curves. For the samples implanted with a lower dose of 3 × 1017 He/cm2, there is no obvious displacement burst found. Furthermore, the burst width increases with the increase of the dose. 相似文献
49.
When the side of a beverage can or the domed lid of a jar is pushed inward, all or part of the structure may suddenly snap into an inverted configuration. The velocity of the pushing motion affects this instability. Most previous analyses of snap-through have considered force control (increasing the pushing force, e.g., a weight). Snap-through under dynamic, unilateral displacement control is investigated here, with the indentor moving at constant velocity (as in a universal testing machine) until snap-through occurs. Shallow elastic arches with immovable pinned ends are analyzed. Attention is focused on the critical height of the indentor at which snap-through is initiated. The effects of the indentor velocity, indentor location along the span, initial arch height, and damping magnitude are investigated. In addition, experiments are conducted on shallow buckled beams, which behave similarly to arches. Usually, the higher the indentor velocity, the further the indentor must move before snap-through occurs. 相似文献
50.
Abstract Molecular dynamics simulations of low-energy atomic recoils have been carried out for α-Ti (HCP) with a view to investigating the displacement threshold energy, Ed, in detail. These have been undertaken at 0 K and 100 K, using a many-body interatomic potential modified to reflect the dominant two-body interaction at short range. This is the first systematic study of atomic displacement events in the HCP structure using such a potential. The mechanisms of these threshold events have been investigated and the strong orientation dependence of the threshold energy has been interpreted in terms of the HCP crystal structure. Also, a correlation has been found between the magnitude of the threshold displacement energy and the maximum number of atoms temporarily displaced into interstitial positions during a cascade. 相似文献