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71.
Motivated by experiments on single-headed kinesin KIF1A, we develop a model of intracellular transport by interacting molecular motors. It captures explicitly not only the effects of adenosine triphosphate hydrolysis, but also the ratchet mechanism which drives individual motors. Our model accounts for the experimentally observed single-molecule properties in the low-density limit and also predicts a phase diagram that shows the influence of hydrolysis and Langmuir kinetics on the collective spatiotemporal organization of the motors. Finally, we provide experimental evidence for the existence of domain walls in our in vitro experiment with fluorescently labeled KIF1A. 相似文献
72.
73.
Wen J Chowdhury P Fulton DB Datta A Das K Andreotti AH Petrich JW 《Photochemistry and photobiology》2003,77(1):5-9
Nuclear magnetic resonance measurements indicate that hypericin exists in the same "normal" tautomeric form irrespective of whether the solvent is dimethyl sulfoxide or tetrahydrofuran. This result is discussed in the context of previous experimental and theoretical work. It is concluded that solvent perturbations cannot induce tautomerization in hypericin. 相似文献
74.
We derive a relationship between the bandwidth and active length and a figure of merit for velocity- and near-velocity-matched lithium niobate traveling-wave electro-optic modulators. The figure of merit is given by the bandwidth per unit drive voltage squared and is independent of the length of the device. Alternatively, this figure of merit can be described by its inverse, which is proportional to the device's switching energy. 相似文献
75.
76.
Residual stress can adversely affect the mechanical, electronic, optical and magnetic properties of thin films. This work describes a simple stress measurement instrument based on the bending beam method together with a sensitive non-contact fibre optical displacement sensor. The fibre optical displacement sensor is interfaced to a computer and a Labview programme enables film stress to be determined from changes in the radius of curvature of the film-substrate system. The stress measurement instrument was tested for two different kinds of thin film, hard amorphous carbon nitride (CN) and soft copper (Cu) films on silicon substrates deposited by RF magnetron sputtering. Residual stress developed in 500 nm thick CN thin films deposited at substrate temperatures in the range 50-550 °C was examined and it was found that stress in CN films decreased from 0.83 to 0.44 GPa compressive with increase of substrate temperature. Residual stress was found to be tensile (121 MPa) for Cu films of thickness 1500 nm deposited at room temperature. 相似文献
77.
Paramita Saha Chowdhury 《Journal of luminescence》2007,124(2):327-332
Here, we have examined the role of capping agent on the optical properties of CdS nanoparticles by steady-state and time-resolved photoluminescence (PL) spectroscopy. The estimated particles sizes are 3.45, 2.5 and 2.39 nm for uncapped, capped with silica (SiO2) and thiosalicylic acid (TSA), respectively. The absorption and emission spectra show a clear blue shift to shorter wavelengths in presence of TSA- and SiO2-capped nanoparticles. It is found that the average decay time 〈τ〉 are 6.24, 4.54 and 2.84 ns for uncapped, capped with SiO2 and TSA nanoparticles, respectively. Our analysis suggests that the hole or the electron is trapped on thiol molecule of TSA or hydroxyl group of SiO2, then radiative recombination of the electron and hole is delayed, resulting in strong quenching of PL efficiency. 相似文献
78.
Fei Su William Hwang Arindam Mukherjee Krishnendu Chakrabarty 《Journal of Electronic Testing》2007,23(2-3):219-233
Microfluidics-based biochips are soon expected to revolutionize biosensing, clinical diagnostics and drug discovery. Robust off-line and on-line test techniques are required to ensure system dependability as these biochips are deployed for safety-critical applications. Due to the underlying mixed-technology and mixed-energy domains, biochips exhibit unique failure mechanisms and defects. We first relate some realistic defects to fault models and observable errors. We next set up an experiment to evaluate the manifestations of electrode-short faults. Motivated by the experimental results, we present a testing and diagnosis methodology to detect catastrophic faults and locate faulty regions. The proposed method is evaluated using a biochip performing real-life multiplexed bioassays. 相似文献
79.
A pore-scale analysis of nonaqueous phase liquid (NAPL) blob dissolution and mobilization in porous media was presented. Dissolution
kinetics of residual NAPLs in an otherwise water-saturated porous medium was investigated by conducting micromodel experiments.
Changes in residual NAPL volume were measured from recorded video images to calculate the mass transfer coefficient, K and the lumped mass transfer rate coefficient, k. The morphological characteristics of the blobs such as specific and intrinsic area were found to be independent of water
flow rate except at NAPL saturations below 2%. Dissolution process was also investigated by separating the mass transfer into
zones of mobile and immobile water. The fractions of total residual NAPL perimeters in contact with mobile water and immobile
water were measured and their relationship to the mass transfer coefficient was discussed. In general, residual NAPLs are
removed by dissolution and mobilization. Although these two mechanisms were studied individually by others, their simultaneous
occurrence was not considered. Therefore, in this study, mobilization of dissolving NAPL blobs was investigated by an analysis
of the forces acting on a trapped NAPL blob. A dimensional analysis was performed to quantify the residual blob mobilization
in terms of dimensionless Capillary number (Ca
I). If Ca
I is equal to or greater than the trapping number defined as , then blob mobilization is expected. 相似文献
80.
We have calculated the phonon and periodon dispersion relations in IV–VI semi-conducting bulk PbTe and SnTe and their superlattice
structure. The model used here is a one-dimensional lattice which includes harmonic interactions up to second neighbours as
well as on-site nonlinear electron-ion interactions at the anion site. We calculate the phonon and periodon dispersion relations
in bulk and PbTe-SnTe superlattice for the transverse optic and acoustic modes using the transfer matrix method. Our analysis
has predicted correct nature of the folding of acoustic and confinement of optical phonons at various frequency intervals
corresponding to pass and stop bands of the superlattices. 相似文献