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661.
Heterobimetallic alkoxides of Cu(II) of the types [Cu{η4-Ti2(OEt)9}Cl] (1) and [Cu{η3-Ti2(OR)9}2] [R = Pri
(2), R = Et(3)] have been prepared for the first time by the reactions of CuCl2 · xROH with KTi2(OR)9 in 1:1 and 1:2 molar ratios, respectively, in benzene medium. The chloro(nonaalkoxo dititanato)copper(II) complexes undergo
chloride replacement reactions by a variety of monodentate alkoxo (−OPri, −OEt) and chelating [Al(OPri)
4
−
, Al(OEt)
4
−
, Nb(OPri)
6
−
, Zr2(OPri)
9
−
, Sn2(OPri)
9
−
, and Sn2(OEt)
9
−
] ligands to form interesting hetero(bi-and tri-)metallic complexes. Alcoholysis (with methyl alcohol and tert-butyl alcohol) and hydrolytic [with Ba(OH)2 · 8H2O powder] reactions of a few typical compounds have also been investigated. All of these have been characterized by elemental
analyses, molecular weight determinations, spectral (i.r. and visible) and magnetic studies. On attempted volatilization under
reduced pressure these complexes liberated titanium alkoxides as a volatile component leaving nonvolatile residues. 相似文献
662.
Y. K. Agrawal 《Mikrochimica acta》1976,66(5-6):595-601
Summary A method for rapid extraction and spectrophotometric determination of cerium (IV) is described. The cerium-N-p-tolylbenzo-hydroxamic acid complex is extracted into chloroform at the pH 8.4 to 9.8. Maximum absorbance occurs between 460 and 470 nm. The values are reproducible at 465 nm and Beer's law is obeyed at this wavelength over the range of 0.03–40, per ml of the cerium(VI). The molar absorptivity of the cerium-p-TBHA complex is 4.6×103 l · mole–1 · cm–2 at 465. An attempt has been made to determine the cerium in sea water.
Zusammenfassung Eine Methode zur schnellen Extraktion und spektrophotometrischen Bestimmung von Cer(IV) wurde beschrieben. Der Cer-Komplex mit N-p-Tolylbenzohydroxamsäure wird bei pH 8,4–9,8 mit Chloroform extrahiert. Das Absorptionsmaximum liegt zwischen 460 und 470 nm. Bei 465 nm sind die Ablesungen reproduzierbar und wird das Beersche Gesetz zwischen 0,03 und 40g Cer/ml erfüllt. Die molare Extinktion des genannten Komplexes beträgt bei 465 nm 4,6 · 103 l · mol–1 · cm–2. Es wurde versucht, den Cergehalt von Meerwasser zu bestimmen.相似文献
663.
K. G. Varshney A. Agrawal S. C. Mojumdar 《Journal of Thermal Analysis and Calorimetry》2007,90(3):731-734
Both temperatures, T
C, (T
C —Curie temperature) and heat of the phase transition: ferroelectric-paraelectric, ΔH, in the BaxSr1−xTiO3 materials have been studied by means of the microcalorimetric method. The determined parameters were verified by either temperature
dependence of the dielectric permittivity (Curie-Weiss law) or thermodynamic method. The effect of strontium content on T
C has been discussed. It was found that microcalorimetry is useful tool studying phase transition phenomena in ferroelectric
perovskites. 相似文献
664.
Amita Agrawal Nidhi Sharma Som K. Mishra Prem D. Sharma 《Transition Metal Chemistry》1992,17(6):547-551
The second order kinetics of uric acid oxidation by hexacyanoferrate(III) in acetate buffers were studied by estimating oxidant
colorimetrically at 420 nm. Two moles of organic acid react with one mole of the oxidant and oxidation products are alloxan
and urea.
TMC 2661 相似文献
665.
TiO2−SiO2 fibres with 0, 5, 10 and 20 volume % SiO2 have been prepared by drawing from a gel followed by sintering at different temperatures. Nearly one meter long fibres can
be drawn easily in conditions of about 50% relative humidity. Addition of SiO2 inhibits the crystallisation of TiO2 and also the anatase → rutile transformation and improves the strength of the fibres. While the pure TiO2 fibres are brittle, those with 5, 10 and 20 volume % SiO2 are flexible and strong. Tensile strength values as high as 3 GPa have been achieved in the 10 volume % SiO2−TiO2 fibres. Fibres heated above 900°C are brittle. The shape of the cross section of the fibres is found to depend on their diameters. 相似文献
666.
Line strengthsS for the dipole allowed transitions within then=2 complex of the carbon isoelectronic sequence have been fitted in the formZ
2
S=A+B/(Z–C), whereZ is the nuclear charge of a particular ion. The constantsA,B andC are determined by using a non-linear least square method. The data forS is taken from the configuration interaction calculations which included internal, semi-internal and all external type correlations for ions in the rangeZ=8–26. It is shown that the values ofA obtained from the fit for all the transitions are in excellent accord with the ab-initio values obtained in the hydrogenic limitZ provided near degeneracy effects are included. 相似文献
667.
668.
Spatiotemporal shaping of terahertz pulses 总被引:1,自引:0,他引:1
We report temporal shaping of few-cycle terahertz pulses, using a slit in a conductive screen as a high-pass filter. The filter's cutoff frequency was tuned by changing the width of the slit; the slope of the cutoff transition was altered by changing the thickness of the screen. We measured the transmission function of the filters, using large-aperture photoconducting antennas to create and detect the incident and transmitted electric field. Our experimental results were in excellent agreement with the performed finite-difference time-domain simulations of the propagation of the pulse through the slit. When the screen thickness was greater than the slit width, the filter was well modeled by a short, planar waveguide. Using a simple transfer function, we accurately describe the sharp cutoff and dispersion of such a filter. 相似文献
669.
670.