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11.
R. Winkler J. Wilhelm M. Capitelli C. Gorse 《Plasma Chemistry and Plasma Processing》1992,12(1):71-87
Calculations of the electron energy distribution and of relevant macroscopic quantities of collision-dominated, weakly ionized plasmas under rf field action have been performed with increasing degrees of ionization, and the impact of the electron-electron interaction on these quantities was determined. The investigations were performed for the gas plasmas in CO and H2 as representatives of molecular plasmas The energy distribution and macroscopic quantities are obtained by solving the nonstationary Bolizmann equation for a given rf field and degree of ionization taking into accoung and additional Fokker-Planck term besides the collision integrals for the elastic and the main inelastic collision processes. In these molecular plasmas a remarkable impact of the electron-electron interaction connected with increasing Maxwellization is observed for degrees of ionization greater than 10. 相似文献
12.
M. Capitelli R. Celiberto C. Gorse R. Winkler J. Wilhelm 《Plasma Chemistry and Plasma Processing》1988,8(2):175-188
Electron energy distribution functions (EEDF) and related properties in the bulk region of the rf CO plasma at the reduced rf field frequency /p0=×107 sec–1 torr–1 have been calculated by solving the time-dependent spatially homogeneous Boltzmann equation in the presence of second-kind collisions and have been interpreted on a microphysical basis. The results show that second-kind collisions (vibrational and electronic) strongly affect the temporal evolution of EEDF, of the mean energy, and of the mean collision frequencies for vibrational and electronic excitation processes, as well as for ionization. In particular, second-kind collisions in the CO rf bulk plasma strongly decrease the modulation of the mean ionization frequency during its periodical alteration in the rf field. Furthermore, the effect of second-kind collisions on an approximate determination of the time-averaged EEDF in the rf bulk plasma using the so-called effective-field appriximation has been estimated. 相似文献
13.
Sergey Y. Savinov Hwaung Lee Hyung Keun Song Byung-Ki Na 《Plasma Chemistry and Plasma Processing》2003,23(1):159-173
An experimental study of plasmachemical reaction involving CH4 and N2 molecules in rf discharge was studied in order to know the effect of vibrational excitation of N2 molecules. When the relative nitrogen concentration was greater than 0.8, the main product of CH4 decomposition was HCN, and the rate of methane decomposition at this condition was faster than that one in pure methane. These results could be confirmed through the mass spectroscopic method. The reason for these results is the vibrational energy of N2 excited by rf discharge. The chain reaction mechanisms of producing HCN by vibrational excitation of N2 were examined closely through numerical simulation. The rate-controlling step was the dissociation reaction of excited nitrogen molecule to the atomic nitrogen, so the process of HCN synthesis was limited by the value of reaction constant, kN. 相似文献
14.
The decomposition of N2O in a 13.56-MHz parallel-plate system was studied usingin situ Fourier transform infrared (FTIR) spectroscopy. Areas of two infrared absorption bands of N2O recorded at 8 cm–1 resolution were used to estimate relative gas-phase dissociation as a function of rf power and flow rate at 500 mT. Flow rate was found to strongly affect band areas over the range of powers investigated (10–90 W). The effect of rf power on band areas diminished above 40 W, probably due to poor plasma confinement. Distortion of the band shapes by the plasma permitted rotational temperatures to be estimated. Rotational temperature increased essentially linearly with power at constant flow rate, reaching 450 K at 80 W, but was independent of flow rate at constant power. Rotational temperatures were also found to depend on the temperature of the electrodes, which were heated by plasma exposure. No infrared-active product species were observed even under batch conditions where all N2O was irreversibly dissociated. This lack of detectable products and a 50% pressure rise observed in a batch study suggest that N2 and O2 are the primary stable discharge products. 相似文献
15.
A combination of energy filtered transmission electron microscopic (EF-TEM) procedures is proposed for the non-perturbing physico-chemical characterization of submicron mineral and organic colloids in aquatic systems. Synthetic hematite microparticles and xanthan polysaccharides were used as well-characterized model colloids in order to determine the optimum EF-TEM analysis conditions. In this paper, it is demonstrated that (i) our model colloids are morphologically representative of naturally occurring mineral/organic associations, (ii) EF-TEM allows the detection of fine xanthan ultrastructures without artefacts of conventional staining methods and (iii) submicron hematite particles can be specifically visualized and spectrometrically measured by EF-TEM within a hematite/xanthan mixture. This EF-TEM procedure appears to be appropriate for the characterization of real aquatic samples. 相似文献
16.
Quadrupole mass spectrometry has been employed to characterize the ionic species in the discharges of pure CH4, CH4/H2, and CH4/Ar systems. For pure methane, the major positive ions in the discharge at low pressure (e.g., 0.15 torr) are CH
3
+
, C2H
3
+
, CH
2
+
, C2H
2
+
, CH
4
+
, C2H
4
+
, and C2H
5
+
at high pressure (e.g., 0.5 torr) the major ions are CH
3
+
, C2H
3
+
, C2H
5
+
, C3H
3
+
, C H3H
7
+
, C4H
7
+
, C5H
7
+
, C6H
5
+
, and C7H
7
+
. The relative abundances of C1 ions decrease with increasing pressure, whereas those of higher-order ions increase with pressure. For 5% CH4 + 95% H2 mixture, in addition to those sampling from the pure methane plasma at the lower pressure, H
n
+
ions have also been detected. For 5% CH4 +95% Ar mixture, the principal ions are CH
3
+
, CH
2
+
, CH+, CH
5
+
, Ar+, and ArH+; the ions containing more than two carbon atoms are negligible. In these discharges, the CH
3
+
and C2H
3
+
are the most important positive ions in C1 and C2 ions, respectively. The ions detected are believed to come from the sheath between the electrode and the luminous plasma, and have high kinetic energy. An ion-molecule reaction mechanism is proposed which can well explain the observed main features of ionic products.Died June 1, 1991. 相似文献
17.
Serially coupled capillary columns supercritical fluid chromatography with midpoint pressure control
Two capillary columns of different polarities were coupled in series by means of a coupling restrictor. The pressure of the first column and the midpoint pressure (between the coupling restrictor and the second column) were controlled independently of each other using two pumps. The selectivity of this separation system was highly dependent on the pressure difference and could be continuously changed between those of two columns. The pressure difference could be changed even in course of separation for fine tuning of the selectivity. Several examples were shown to demonstrate the utility of this method. 相似文献
18.
Structural tuning of coordination polymers by 4-connecting metal node and secondary building process
Due to variation in ligand's conformation, metal node's connecting geometry, and secondary building process by anions, bat-like, dumbell-like, diamondoid, or pillar-layer topologies are achieved. 相似文献
19.
Ytterbium, erbium, aluminum tri-doped zinc oxide crystal was synthesized, which can turn color from red to green up-conversion luminescence through adjusting aluminum content. When the aluminum concentration reached 4?mol%, the color of up-conversion emission first turn from red to green. Meanwhile, the ratio of red to green emission reduced from 25.32 to 0.26, and the coordinates of chromaticity coordinate calculation changes from (0.5749, 0.3378) to (0.2190, 0.7169) with aluminum concentration range from 0 to 4?mol%. The up-conversion emission peaks at 521, 542, and 660?nm of sample originate from the transitions of 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2 of erbium ions, respectively. X-ray diffraction patterns perform the better crystallization degree with increasing aluminum concentration. The scanning electron microscopy images show the porous and lamellar structures with different aluminum concentrations. A convenient but effective design to obtain ytterbium, erbium, aluminum tri-doped zinc oxide up-conversion luminescence is reported, which can turn color from red to green. 相似文献
20.