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11.
Jianming Lai Jijun Zhang Linjun Wang Jiahua Min Wenqi Wu Min Shen Wei Liang 《Crystal Research and Technology》2015,50(11):817-822
In this paper, the CdMnTe crystals were grown by the Travelling Heater Method (THM) and the Vertical Bridgman (VB) method, respectively. The crystal properties, including the Mn axial distribution, impurity concentrations, resistivity, Hall effects and energy response spectra, were characterized and compared. The results shown that the CdMnTe crystal grown by the THM had more uniform Mn distribution and lower impurity concentrations compared to the crystal grown by VB method. The resistivity of CdMnTe grown by THM was (1.5 ∼ 8) × 1010 Ω.cm, while the resistivity of CdMnTe grown by VB was 107∼108 Ω.cm. The In dopant distributed uniformly throughout the crystal ingot grown by THM with the doping concentration of 0.6–0.7 ppm, while the In dopant concentration throughout the crystal grown by VB method is in the range of 1.31–2.4 ppm. Hall measurements revealed that the conductivity of the THM grown crystal was weak n‐type conductivity and the VB grown crystal was p‐type conductivity. A planar CdMnTe detector from the THM grown crystal showed a resolution of 8% of the 241Am radiation at 59.5 keV peak, however, no energy response was revealed with the CdMnTe detector by the VB method. The results demonstrate that CdMnTe crystal grown by THM have better crystal quality and detector properties compared to that by VB method. 相似文献
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R. D. Davies 《Journal of separation science》1981,4(6):270-275
This contribution comprises two parts, the one covering some variables in the dry-packing of columns for liquid chromatography, the other the use of an automatic dry-packer in liquid chromatography. A high-pressure stainless steel column was dry-packed using a 20-44 μm size, irrregularly shaped, silica gel support. It was found that, when support was added in discrete amounts, lateral tapping produced a column of higher efficiency (HETP = 0.69 mm) than was the case for vertical tapping (HETP = 1.37 mm). Simultaneous vertical and lateral tapping produced an intermediate result. Bulk filling of the column followed by tapping was inferior to adding support in discrete amounts. An apparatus constructed to perform the vertical and lateral tapping operations automatically confirmed the above conclusions. It was concluded that commercially available dry-packing apparatus do not offer the best action for packing an efficient column since they involve predominantly vertical tapping. 相似文献
14.
James J. Sheng 《Transport in Porous Media》2009,77(3):507-527
To determine the permeabilities from a vertical interference test, earlier investigators proposed correlations or type curves
based on point source solutions or partially penetrated well solutions. However, it is impossible for these correlations or
type curves to cover all possible scenarios in the real world. In more recent years, people use regression analysis to simultaneously
match the pressure responses at the source interval and the observation point. With regression analysis, we face the problem
of non-unique solutions. Sometimes, estimated permeability could be outside a reasonable range when analyzing noisy data from
real tests. In this paper, a new technique is presented to estimate horizontal and vertical permeabilities from the time-delayed
response in a wireline vertical interference test. In a vertical test, a pressure drawdown test period is followed by a pressure
buildup test period. Because of the delay in response, the pressure at the observation probe continues to drop for some time
while the pressure at the source interval is being built up. The maximum pressure drop at the observation probe with regard
to the maximum pressure drop in the source interval is time-delayed. Using this time delay and the maximum pressure drop at
the observation probe, vertical and horizontal permeabilities can be estimated. A novel numerical scheme is used. The new
technique is compared with the previous methods, and it shows its superiority in accuracy. In addition, it can be used in
different test configurations. Application issues in real testing conditions are discussed. Finally, two field tests are analyzed
using this technique, while an earlier effort to analyze the tests using a conventional method was not successful due to poor
data quality. 相似文献
15.
Yu-Qing Fang 《European Polymer Journal》2010,46(5):1163-1167
A series of polyimides (PIs) were copolymerized from 4-dodecyloxy-biphenyl-3′,5′-diaminobenzoate (DBPDA), 3,3′-dimethyl-4,4′-methylene-dianiline (DMMDA) and 4,4′-oxydi(phthalic anhydride) (ODPA) via one-step method. The PIs possessed excellent solubility in polar aprotic solvents and easily formed thin flexible films by solution casting. The glass-transition temperatures (Tgs) of the PIs were in the range of 219-242 °C and thermal decomposition temperatures in nitrogen occurred above 350 °C. The resultant PI films exhibited high transparency at wavelengths greater than 400 nm and induced excellent uniform vertical alignment of liquid crystal (LC). Even after the rubbing process, the pretilt angles of LC were still above 89°. The PI seems to be a prospective material for alignment layers in flexible displays. 相似文献
16.
S. Shahab Naghavi Thomas Gruhn Gerhard H. Fecher Katerina Medjanik Sergej A. Nepijko Ralph Rieger Klaus Müllen 《Journal of Molecular Spectroscopy》2011,265(2):95-1319
Functionalized polycyclic aromatic hydrocarbons (PAHs) are an interesting class of molecules in which the electronic state of the graphene-like hydrocarbon part is tuned by the functional group. Searching for new types of donor and acceptor molecules, a set of new PAHs has recently been investigated experimentally using ultraviolet photoelectron spectroscopy (UPS). In this work, the electronic structure of the PAHs is studied theoretically with the help of B3LYP hybrid density functionals. Using the ΔSCF method, electron binding energies have been determined which affirm, specify and complement the UPS data. Symmetry properties of molecular orbitals are analyzed for a categorization and an estimate of the related signal strength. While σ-like orbitals are difficult to detect in UPS spectra of condensed film, calculation provides a detailed insight into the hidden parts of the electronic structure of donor and acceptor molecules. In addition, a diffuse basis set (6-311++G**) was used to calculate electron affinity and LUMO eigenvalues. The calculated electron affinity (EA) provides a classification of the donor/acceptor properties of the studied molecules. Coronene-hexaone shows a high EA, comparable to TCNQ, which is a well-known classical acceptor. Calculated HOMO-LUMO gaps using the related eigenvalues have a good agreement with the experimental lowest excitation energies. TD-DFT also accurately predicts the measured optical gap. 相似文献
17.
We investigate theoretically the dynamics of three low-order transverse modes in a small-area vertical cavity surface emitting laser. We demonstrate the spontaneous breaking of axial symmetry of the transverse field distribution in such a device. In particular, we show that if the linewidth enhancement factor is sufficiently large dynamical regimes with broken axial symmetry can exist up to very high diffusion coefficients ~ 10 μm2/ns. 相似文献
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20.
Dmitry A. Bratsun Alexej V. Zyuzgin Gennady F. Putin 《International Journal of Heat and Fluid Flow》2003,24(6):835-852
We study both experimentally and numerically the convective flow in a tall vertical slot with differently heated walls. The flow is investigated for the fluid with the Prandtl number Pr=26, which is large enough to ensure the traveling waves as primary instability and small enough to prevent boundary layer convection. The flow evolution is determined on the base of the visual observations, power spectra and amplitude analysis. In the numerical simulations of two- and three-dimensional flows, we accept an assumption of an infinite fluid layer. The satisfactory agreement with experiment is observed, and the sequence of convection states is discovered. It starts with a plane-parallel flow as primary solution, which becomes unstable to two counter-propagating waves. It is followed by a tertiary three-dimensional flow in the form of wavy traveling waves. As the Grashof number is increased even further, a chaotically oscillating cellular pattern consisting of the pieces of broken waves arises. The formation of a structure in the form of the vertical rolls chaotically modulated along axes concludes this complicated picture. 相似文献