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991.
Differential absorption spectra of RbAg4I5 have been measured in the exciton absorption region of AgI within the temperature range 27–250 °C. In the same temperature
range, the temperature behavior of the heat capacity of RbAg4I5, Rb2AgI3, and KAg4I5 have been obtained by differential scanning calorimetry. An analysis of the results suggests that, in AgI microcrystals less
than r
cr in size, the upper boundary for stability of the low-temperature β modification is higher by several tens of degrees.
Fiz. Tverd. Tela (St. Petersburg) 40, 852–854 (May 1998) 相似文献
992.
V. A. Zherebtsov 《Technical Physics》1998,43(7):818-823
It is shown that plasma-chemical processes involving ionized and excited particles can make the main contribution to the pumping
of energy into vibrations of carbon monoxide molecules. It is noted that the use of helium as a buffer gas in the active laser
medium is not optimal. The employment of argon instead of helium permits a 1.5-fold increase in the efficiency of the pumping
of energy into carbon monoxide molecules and an order-of-magnitude decrease in the threshold energy for pumping the active
medium.
Zh. Tekh. Fiz. 68, 80–85 (July 1998) 相似文献
993.
The problems of choosing the optimal mathematical model for a prescribed range of parameters of a pulsed action are discussed.
A preliminary analysis performed by similarity and dimensional-analysis methods using interpolation equations of state of
the matter shows that the complete system of equations of gasdynamics can be simplified by dropping individual terms which
are not important in a given parameter range. The results of an analysis are presented in the form of nomograms, which also
make it possible to identify the class of fast and energy-intensive gasdynamic processes more accurately than at an intuitive
level.
Zh. Tekh. Fiz. 68, 44–47 (May 1998) 相似文献
994.
S. O. Romanovskii A. V. Sel’kin I. G. Stamov N. A. Feoktistov 《Physics of the Solid State》1998,40(5):814-815
A study is made of the effect of electric fields on the exciton states of β-ZnP2 crystals (T=77 K) in structures with Schottky barriers formed by depositing semitransparent electrically-conducting InSnO2 films on the crystal surface. The observed changes in the exciton optical reflection spectra when an electrical potential
is applied to a barrier are explained by the shift and broadening of the exciton level caused by the Stark effect. The experimental
data are compared with calculations based on a theory of exciton optical reflection from planar spatially nonuniform structures.
Fiz. Tverd. Tela (St. Petersburg) 40, 884–886 (May 1998) 相似文献
995.
996.
A. V. Belousov V. A. Kovarskii 《Journal of Experimental and Theoretical Physics》1998,87(6):1053-1057
We examine nonradiative transitions in molecules with allowance for the effect of a classical polar exterior medium on tunneling
charge transport. The approach allows for the vibrational frequencies of a molecule in the electron transition. In the case
of slow fluctuations, the theory predicts a low-temperature (non-Arrhenius) increase in the tunneling nonradiative transition
rate, and the results agree qualitatively with the experimental data. When the fluctuations of the exterior medium are rapid,
at certain values of the molecular parameters the tunneling decay rate is found to decrease with increasing temperature because
the conditions needed for resonant tunneling are violated.
Zh. éksp. Teor. Fiz. 114, 1944–1953 (December 1998) 相似文献
997.
H. Hommel A. Touhami A. Halli A. P. LeGrand 《Journal of Polymer Science.Polymer Physics》1995,33(16):2189-2198
EPR spectroscopy of labeled poly(ethylene oxide) (PEO) grafted on silica has been used to characterize the conformation and local dynamics of the chains. Grafted molecules of MW 2000 with grafting ratios of 0.045, 0.057, 0.126, and 0.42 molecules/nm2 were in contact with benzene. The mobility of the label was compared with that observed for solution of PEO from very diluted to highly concentrated and even bulk PEO. Thus, the concentration inside the grafted layer could be evaluated and also the thickness, which evolves rather linearly with the grafting ratio. © 1995 John Wiley & Sons, Inc. 相似文献
998.
The solvent extraction of cobalt(II), nickel(II) and copper(II) using 2,4-pent-dione (Hacac) and 4-phenyl-2, 4-but-dione (Hbzac)
is carried out by varying the reagent concentration and pH of the aqueous phase. Each of these metals is quantitatively separated
(≈ 98%) from their binary mixtures with monovalent (Ag), divalent (Mn, Zn, Cd, Hg, Mg, Sn, Pb) and trivalent (Cr, Fe) metals.
The extraction constants are calculated from the metal distribution data using linear regression analysis. The extracted species
is MA2 in each case. A most significant result is separation of copper(II) from iron(III) which otherwise interferes when extracted
from the acidic medium. 相似文献
999.
The twisting power of chiral probes in nematics is interpreted in terms of a shape model, in which the surface elements of the solute molecules tend to align with the local director. The theoretical treatment is based on a previous approach, suitable for relating order parameters in nematics to molecular shape, and leads to the definition of a molecular pseudo-tensor whose orientational average determines the pitch and handedness of the helical macrostructures. Results of numerical calculations performed for distorted biphenyl and binaphthyl molecules are in agreement with the experimental results. 相似文献
1000.
The orientational ordering of several liquid crystals containing a difluorosubstituted phenyl ring has been studied through the use of C-13 NMR. The fluorinated phenyl ring of these liquid crystals have Cs symmetry, so three order parameters are required to completely describe the ordering of this ring. All three of these order parameters have been calculated from carbon-fluorine dipolar coupling constants obtained from the carbon-fluorine splittings in the C-13 NMR spectra. Because of the complexity of the fluorine-coupled spectra, variable angle spinning (VAS) was used to resolve the carbon-fluorine splittings. In order to study the orientational ordering over wide ranges of temperature, we have developed an empirical correlation between the order parameter and the value of a carbon-fluorine dipolar coupling constant. This enabled us to study the change in the order parameter with temperature. The results of applying this method to several structurally similar liquid crystals containing the same type of difluorinated phenyl ring are presented. A comparison is made to a similar mono-fluorinated liquid crystal. 相似文献