全文获取类型
收费全文 | 2199篇 |
免费 | 7篇 |
国内免费 | 8篇 |
专业分类
化学 | 818篇 |
晶体学 | 19篇 |
力学 | 159篇 |
数学 | 268篇 |
物理学 | 950篇 |
出版年
2017年 | 11篇 |
2016年 | 18篇 |
2015年 | 16篇 |
2014年 | 15篇 |
2013年 | 86篇 |
2012年 | 40篇 |
2011年 | 59篇 |
2010年 | 38篇 |
2009年 | 50篇 |
2008年 | 61篇 |
2007年 | 71篇 |
2006年 | 61篇 |
2005年 | 62篇 |
2004年 | 76篇 |
2003年 | 74篇 |
2002年 | 83篇 |
2001年 | 57篇 |
2000年 | 60篇 |
1999年 | 54篇 |
1998年 | 39篇 |
1997年 | 37篇 |
1996年 | 35篇 |
1995年 | 36篇 |
1994年 | 31篇 |
1993年 | 33篇 |
1992年 | 31篇 |
1991年 | 30篇 |
1990年 | 36篇 |
1989年 | 33篇 |
1988年 | 29篇 |
1987年 | 55篇 |
1986年 | 36篇 |
1985年 | 48篇 |
1984年 | 46篇 |
1983年 | 37篇 |
1982年 | 48篇 |
1981年 | 39篇 |
1980年 | 37篇 |
1979年 | 35篇 |
1978年 | 30篇 |
1977年 | 30篇 |
1976年 | 26篇 |
1975年 | 22篇 |
1974年 | 18篇 |
1973年 | 30篇 |
1972年 | 14篇 |
1937年 | 12篇 |
1934年 | 10篇 |
1933年 | 10篇 |
1932年 | 9篇 |
排序方式: 共有2214条查询结果,搜索用时 15 毫秒
71.
Oxygen K-edge x-ray absorption spectra were studied on the electrochromic amorphous thin film a-WO3 in the comparison with crystalline oxides having variable electronic (d0, d1, d2) and atomic structure: monoclinic m-WO3 (insulator - d0), cubic Na0.6WO3 (metal - d1), cubic ReO3 (metal - d1), layered-type hexagonal h-WO3, WO3H2O and with intercalated HxReO3 (metal - d2), HxWO3 oxides having a metal-isulating transition. The changes in the XANES range 10–15 eV above the absorption edge are interpreted
based on the known band-structure calculations. The high-energy features are related to the multiple-scattering processes
(EXAFS) on the nearest atoms. The intensity of the feature at 550–560 eV is attributed for the first time to the value of
the metal-oxygen-metal bond angle.
Paper presented at the 5th Euroconference on Solid State Ionics, Benalmádena, Spain, Sept. 13–20, 1998. 相似文献
72.
A tunable diode lase in the 4.7 μm region has been used to perform measurements of pressure-broadening in infrared lines of CO(v = 1 ←0) perturbed by H2 and He at liquid nitrogen and room temperatures. For the COH2 system the experimental results are compared to previous double resonance data and to ab-initio quantum calculations. The COHe data make a confrontation of the two available potential energy surfaces feasible. 相似文献
73.
Ph. Gavillet C. Dionisi A. Gurtu R.J. Hemingway M.J. Losty J.C. Marin M. Mazzucato L. Montanet E. Pagiola R. Blokzijl B. Jongejans J.C. Kluyver G.G.G. Massaro J.J. Engelen J.S.M. Vergeest M. Zralek B. Foster P. Grossmann J. Wells 《Physics letters. [Part B]》1978,78(1):158-161
The backward production of the B(1235) meson is studied in the reaction K?p→Σ?π+ω. This reaction is observed in the final state Σ?π+π+π?π0. A π+ω mass enhancement is visible in the region of the B meson for events with small |u|K? →Σ?) squared four-momentum transfer. The properties of the enhancement agree with those of the B meson. The cross section for K?p→Σ?B+ at incident K? momentum is (3.2 ± 0.5) μb. The backward production of the B meson is compared with similar baryon exchange productions of the A1 and C(Q1) axial vector mesons observed in the same experiment. 相似文献
74.
A. Valentin A. Henry Ph. Cardinet M.F. Le Moal Da-Wun Chen K. Narahari Rao 《Journal of Molecular Spectroscopy》1978,70(1):9-17
The wavenumbers of the vibration rotation band lines of 14N16O are reported for the , and subbands of the 1-0 transition in the infrared. The full set of spectroscopic constants for this band has been determined by direct approach using the analysis of Zare, Schmeltekopf, Harrop, and Albritton. In addition to the band origin ν0 and the B, D, H constants for the lower and upper vibrational levels, the following spin-orbit coupling constants have been derived: and (in cm?1). Apparent centrifugal corrections to these constants have been determined and the values obtained for them are and . Λ-Type doubling constants evaluated by using both grating and tunable laser data are also reported. 相似文献
75.
A simple polarimetric method for the study of metals is discussed. Modulation is obtained by means of a rotating retardation plate and information is extracted from the phase of the signal. Polarizer and analyser have fixed positions, and the system requires no optical compensator and no calibration. Systematic error due to polariser-analyser reference settings is eliminated. Also scanning of the wavelengths is possible. 相似文献
76.
Ph. Cahuzac J. L. LeGouët P. E. Toschek R. Vetter 《Applied physics. B, Lasers and optics》1979,20(1):83-88
Laser induced nonlinear absorption profiles in a three-level system have been recorded to study the effect of elastic collisions
upon optical coherences. In our particular system, the signal is due to a pure double-quantum term, where we have separated
the effect of phase-interrupting collisions from the effect of velocity-changing collisions. Experimental results show that
the effect of velocity-changing collisions is very small, and that broadening of the signal is due to phase-interrupting collisions
mainly. We are able to determine the increase of the decay rate of the coherent superposition (the “coherence”) of two levels
of same parity [Dγ
13/dp=(6.5±1) MHz/Torr] and an upper limit for the mean velocity change (ũ≲5m/s). 相似文献
77.
The gap Δ between the top of the d↑ band and the Fermi level is deduced from optical measurements on a nickel single crystal and found to be ≈50 meV, in agreement with previous estimates. The interpretation of the optical spectrum also suggests that the spin-splitting ΔEd ? 0.40 eV and that a spin- splitting still exists at temperatures higher than TC. 相似文献
78.
Two experimental arrangements of an optical frequency up-converter using GaSe are described. Two wavelength regions have been covered by series of monochromatique rays (one ranging from 3.25 μ to 3.85 μ, the other one from 0.954 μ to 0.968 μ). 相似文献
79.
We present a time-resolved experimental study of ionization by superelastic collisions in excited strontium vapor. Using short duration laser pulses for resonant excitation, we clearly observe that a delay time is necessary to reach runaway collisional ionization after the end of laser excitation. 相似文献
80.
J.J. Dekkers G.Ph. Hoornweg K.J. Terpstra C. Maclean N.H. Velthorst 《Chemical physics》1978,34(2):253-260
Phosphorescence polarisation measurements are reported for a number of planar aromatic compounds in stretched polyethylene. The phosphorescence is to about 80% polarised perpendicular to the molecular plane. In the in-plane intensity second order Herzberg-Teller coupling terms may be at least competitive with three-center ππ spin-orbit integrals, in agreement with suggestions of Friedrich, Metz and Dörr. 相似文献