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981.
Structural properties of silver nanoparticle agglomerates based on transmission electron microscopy: relationship to particle mobility analysis 总被引:1,自引:1,他引:0
Weon Gyu Shin Jing Wang Michael Mertler Bernd Sachweh Heinz Fissan David Y. H. Pui 《Journal of nanoparticle research》2009,11(1):163-173
In this work, the structural properties of silver nanoparticle agglomerates generated using condensation and evaporation method
in an electric tube furnace followed by a coagulation process are analyzed using Transmission Electron Microscopy (TEM). Agglomerates
with mobility diameters of 80, 120, and 150 nm are sampled using the electrostatic method and then imaged by TEM. The primary
particle diameter of silver agglomerates was 13.8 nm with a standard deviation of 2.5 nm. We obtained the relationship between
the projected area equivalent diameter (d
pa) and the mobility diameter (d
m), i.e., d
pa = 0.92 ± 0.03 d
m for particles from 80 to 150 nm. We obtained fractal dimensions of silver agglomerates using three different methods: (1)
D
f = 1.84 ± 0.03, 1.75 ± 0.06, and 1.74 ± 0.03 for d
m = 80, 120, and 150 nm, respectively from projected TEM images using a box counting algorithm; (2) fractal dimension (D
fL) = 1.47 based on maximum projected length from projected TEM images using an empirical equation proposed by Koylu et al.
(1995) Combust Flame 100:621–633; and (3) mass fractal-like dimension (D
fm) = 1.71 theoretically derived from the mobility analysis proposed by Lall and Friedlander (2006) J Aerosol Sci 37:260–271.
We also compared the number of primary particles in agglomerate and found that the number of primary particles obtained from
the projected surface area using an empirical equation proposed by Koylu et al. (1995) Combust Flame 100:621–633 is larger
than that from using the relationship, d
pa = 0.92 ± 0.03 d
m or from using the mobility analysis. 相似文献
982.
Influence of a two-dimensional electron gas on current-voltage characteristics of Al<sub>0.3</sub>Ga<sub>0.7</sub> N/GaN high electron mobility transistors 下载免费PDF全文
The J-V characteristics of AltGa1 tN/GaN high electron mobility transistors(HEMTs) are investigated and simulated using the self-consistent solution of the Schro¨dinger and Poisson equations for a two-dimensional electron gas(2DEG) in a triangular potential well with the Al mole fraction t = 0.3 as an example.Using a simple analytical model,the electronic drift velocity in a 2DEG channel is obtained.It is found that the current density through the 2DEG channel is on the order of 1013 A/m2 within a very narrow region(about 5 nm).For a current density of 7 × 1013 A/m2 passing through the 2DEG channel with a 2DEG density of above 1.2 × 1017 m-2 under a drain voltage Vds = 1.5 V at room temperature,the barrier thickness Lb should be more than 10 nm and the gate bias must be higher than 2 V. 相似文献
983.
Se-Koo Kang Min-Hwan Jeon Jong-Yoon Park Hyoung-Cheol Lee Byung-Jae Park Je-Kwan Yeon Geun-Young Yeom 《Journal of Crystal Growth》2010,312(14):2145-2149
Low temperature (<80 °C) neutral beam deposition (LTNBD) was investigated as a new approach to the fabrication and development of nano-crystalline silicon (nc-Si), which has better properties than that of amorphous silicon (α-Si). The difference between LTNBD and conventional PECVD is that the film formation energy of the nc-Si in LTNBD is supplied by controlled neutral beam energies at a low temperature rather than by heating. Especially, in this study, the characteristics of the nc-Si thin film were investigated by adding 10% of an inert gas such as Ne, Ar or Xe to SiH4/H2. Increasing the beam energy resulted in an increase in the deposition rate, but the crystallinity was decreased, due to the increased damage to the substrate. However, the addition of a higher mass inert gas to the gas mixture at a fixed beam energy resulted not only in a higher deposition rate but also in a higher crystallization volume fraction. The high resolution transmission electron microscopy image showed that the grown film is composed of about 10 nm-size grains. 相似文献
984.
985.
S.V. Melkonyan 《Physica B: Condensed Matter》2012,407(24):4804-4809
The problem of electron mobility variance is discussed. It is established that in equilibrium semiconductors the mobility variance is infinite. It is revealed that the cause of the mobility variance infinity is the threshold of phonon emission. The electron–phonon interaction theory in the presence of an electric field is developed. A new mechanism of electron scattering, called electron–phonon field-induced tunnel (FIT) scattering, is observed. The effect of the electron–phonon FIT scattering is explained in terms of penetration of the electron wave function into the semiconductor band gap in the presence of an electric field. New and more general expressions for the electron–non-polar optical phonon scattering probability and relaxation time are obtained. The results show that FIT transitions have principle meaning for the mobility fluctuation theory: mobility variance becomes finite. 相似文献
986.
Effects of concentration and annealing on the performance of regioregular poly(3-hexylthiophene) field-effect transistors 下载免费PDF全文
This paper investigates the effects of concentration on the
crystalline structure, the morphology, and the charge carrier
mobility of regioregular poly(3-hexylthiophene) (RR-P3HT)
field-effect transistors (FETs). The RR-P3HT FETs with RR-P3HT as an
active layer with different concentrations of RR-P3HT solution from
0.5~wt% to 2~wt% are prepared. The results indicate that the
performance of RR-P3HT FETs improves drastically with the increase
of RR-P3HT weight percentages in chloroform solution due to the
formation of more microcrystalline lamellae and bigger nanoscale
islands. It finds that the field-effect mobility of RR-P3HT FET with
2~wt% can reach 5.78× 10^-3~cm2/Vs which is higher
by a factor of 13 than that with 0.5~wt%. Further, an appropriate
thermal annealing is adopted to improve the performance of RR-P3HT
FETs. The field-effect mobility of RR-P3HT FETs increases
drastically to 0.09~cm2/Vs by thermal annealing at
150~℃, and the value of on/off current ratio can reach
10^4. 相似文献
987.
We calculate accurate interatomic potentials for the interaction of a singly charged silicon cation with a rare gas atom of helium, neon or argon. We employ the RCCSD(T) method, and basis sets of quadruple-ζ and quintuple-ζ quality; each point is counterpoise-corrected and extrapolated to the basis set limit. We consider the lowest electronic state of the silicon atomic cation, Si+(2P), and calculate the interatomic potentials for the terms that arise from this: 2Π and 2Σ+. We additionally calculate the interatomic potentials for the respective spin-orbit levels, and examine the effect on the spectroscopic parameters; we also derive effective ionic radii for C+ and Si+. Finally, we employ each set of potentials to calculate transport coefficients, and compare these to available data for Si+ in He. 相似文献
988.
N. A. Davidenko S. L. Studzinskii L. S. Tonkopieva A. A. Ishchenko N. G. Spitsina A. S. Lobach 《Theoretical and Experimental Chemistry》2007,43(6):385-388
The photoconductivity and photodielectrical properties of films of an aromatic polyimide with the addition of cationic and
anionic polymethyne dyestuffs have been studied. The sensitization of the photoeffect of the dyes with different ionicity
in polyimide films with donor and acceptor units develops the possibility of photogeneration of holes and electrons from dyestuff
molecules and internal bipolar conductivity of the polyimide.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 6, pp. 354–357, November–December, 2007. 相似文献
989.
J Xu K Mahajan W Xue JO Winter M Zborowski JJ Chalmers 《Journal of magnetism and magnetic materials》2012,324(24):4189-4199
Single particle magnetization and size measurements of micron and nano sized, magnetic particles were made using a previously described device referred to as Cell Tracking Velocimetry, CTV. Three types of commercially available, and commonly used, magnetic particles were studied in this report. While the CTV instrument provides individual particles measurements, the average magnetization and size measurements were found to have reasonable agreements with reported values from instruments which measure bulk values. In addition, the CTV instrument, using electromagnets, can also determine magnetization curves, which also proved to have reasonable agreement with other published studies. Given that magnetic separation and analysis technology is dependent on the quality of the magnetic particles used, studies such as this one using CTV provide not only average data, but also provides information with respect to the distribution of the properties such as magnetization and size. For example, the spread of the data in magnetic and settling velocities were found to be predominately due to the size distribution of the analyzed particles. 相似文献
990.
We propose an efficient finite difference scheme for solving the Cahn–Hilliard equation with a variable mobility in complex domains. Our method employs a type of unconditionally gradient stable splitting discretization. We also extend the scheme to compute the Cahn–Hilliard equation in arbitrarily shaped domains. We prove the mass conservation property of the proposed discrete scheme for complex domains. The resulting discretized equations are solved using a multigrid method. Numerical simulations are presented to demonstrate that the proposed scheme can deal with complex geometries robustly. Furthermore, the multigrid efficiency is retained even if the embedded domain is present. 相似文献