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991.
992.
By means of a new force sensor based on optical beam deflection (OBD), the mechanical effects of laser-matter interaction underwater at different incident laser energy are investigated in detail. The experimental results show that a target underwater is impacted in turn by laser-plasma ablation force and high-speed liquid-jet impulse induced by bubbles collapse in the vicinity of a solid boundary. Furthermore, the amplitudes of the two forces increase monotonously with laser energy. According to the ablation force detected by the experiment and the theoretical relationship between laser intensity and ablation pressure, the value of liquid-jet impact against a solid boundary can be easily obtained. In addition, based on the model of a collapsing bubble, some characteristic parameters, such as the liquid-jet impact velocity, the maximum bubble radius, the bubble energy can also be obtained at different laser energy, which are valuable in the corresponding research fields. 相似文献
993.
994.
High-resolution Fourier transform spectra of CH3OH have been investigated in the infrared region from 930 to 1450 cm−1 in order to map the torsion-rotation energy manifolds associated with the ν7 in-plane CH3 rock, the ν11 out-of-plane CH3 rock, and the ν6 OH bend. Upper-state term values have been determined from the assigned spectral subbands, and have been fitted to power-series expansions to obtain substate origins and effective B-values for the three modes. The substate origins have been grouped into related families according to systematic trends observed in the torsion-vibration energy map, but there are substantial differences from the traditional torsional patterns. There appears to be significant torsion-mediated spectral mixing, and a variety of “forbidden” torsional combination subbands with |Δυt|>1 have been observed, where υt denotes the torsional quantum number (equivalent to υ12). For example, coupling of the (υ6,υt)=(1,0) OH bend to nearby torsionally excited (υ7,υt)=(1,1) CH3-rock and (υ8,υt)=(1,1) CO-stretch states introduces (υ6,υt)=(1,0)←(0,1) subbands into the spectrum and makes the ν7+ν12−ν12 torsional hot band stronger than the ν7 fundamental. The results suggest a picture of strong coupling among the OH-bending, CH3-rocking, and CO-stretching modes that significantly modifies the traditional energy structure and raises interesting and provocative questions about the torsion-vibration identity of a number of the observed states. 相似文献
995.
D. B. Lu Y. L. Song Z. X. Yang H. R. Xu C. Wang Z. H. Gao 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,84(3):419-424
By using the first-principles calculations, the electronic properties are studied for the
F-terminated SiC nanoribbons (SiCNRs) with either zigzag edges (ZSiCNRs) or armchair edges
(ASiCNRs). The results show that the broader F-terminated ZSiCNRs are metallic and the
edge states appear at the Fermi level, while the F-terminated ASiCNRs are always
semiconductors independent of their width but the edge states do not appear due to the
Si-C dimer bonds at the edges. The charge density contours analyses shows that the Si-F
and Si-C bonds are all ionic bonds due to the much stronger electronegativities of the F
and C atoms than that of the Si atom. However, the C-F bonds display a typical non-polar
covalent bonding feature because of the electronegativity difference between the F and C
atoms of 1.5 is a much smaller than that of between the F and Si atoms of 2.2, as well as
the tighter bounded C 2s
22p
2
electrons with smaller orbital radius than the Si
3s
23p
2 electrons. For both the
F- and the H-terminated ZSiCNRs, the ground state is a ferromagnetic semiconductor. 相似文献
996.
The efficient oscillation of LiF:F2− color center laser pumped by a compact LD-pumped Nd:YVO4 acousto optically Q-switched laser with 30 kHz pulse repetition rate was demonstrated. The broadband oscillation with 75
μJ pulse energy and 37 kW peak power with the slope efficiency 20% was obtained. The average output power as high as 230 mW
was reached. The narrow line tunable from 1.10 to 1.29 μm laser radiation with 10% conversion efficiency in the maximum of
the tuning curve was achieved under pumping with 1.6 W average pump power. 相似文献
997.
Using the vertical evaporation technique we fabricated saturable absorbers by transferring the double-wall carbon nanotubes
(DWCNT) onto a hydrophilic quartz substrate. The fast recovery time and the saturation intensity of the absorber were measured
to be 228 fs and 130 μJ/cm2, respectively, at 1060 nm. The modulation depth of the absorber was about 3.7%. Passive mode-locked Nd:GdVO4 laser was demonstrated. The continuous wave mode-locked pulses pulse duration is 5.6 ps and the largest average output power
is 1.2 W at the pump power of 9.5 W. To the best of our knowledge, this is the first demonstration of high power continuous
wave mode locking laser with DWCNT absorber. 相似文献
998.
A novel sol-gel/laser-induced technique (SGLIT) has been developed to form nanocrystalline titanium dioxide (TiO2) based thin films with an improved antibacterial performance. TiO2 precursor films loaded with W+6 and Ag+2 ions (W–TiO2, Ag–TiO2) were prepared separately by sol-gel method and spin-coated on microscopic glass slides. As-dried films were subjected to
KrF excimer laser pulses at optimized parameters to generate mesoporous anatase and rutile phases at room temperature. The
anatase phase was obtained after irradiation with 10 laser pulses only at 75–85 mJ/cm2 fluence in W–TiO2 films. However, higher number of laser pulses and higher W+6 content favored the formation of rutile. Whereas Ag–TiO2 films exhibited anatase up to 200 laser pulses at the same fluence. The films were characterized by using XRD, FEG-SEM, TEM
and UV-Vis spectrophotometer to investigate the crystallographic structure, phase transformation, surface morphology, film
thickness and the optical properties. A crystallite size of approximately 20 nm was achieved from the anatase prepared by
SGLIT. The films exhibited an enhanced antibacterial function against E-Coli cells under the UV excitation. 相似文献
999.
Supercontinuum generation in the gain fiber in two-stage nanosecond pulse Er/Yb co-doped double-clad fiber amplifier had been
demonstrated for the first time to our knowledge instead of the conventional method in which nonlinear fiber was pumped by
lasers. The Er/Yb co-doped double-clad fiber acts as the gain media and nonlinear media. This route reduces the splice between
fiber laser and nonlinear fiber. The supercontinuum was achieved with spectrum range from 1530 nm to beyond 1700 nm at 6 W
output power covering the total C-band to U-band. From the analyzing of the spectra at different stages in the amplifiers,
it can be found that it is the modulation instability in the anomalous dispersion regime that initiates the supercontinuum
gereration. 相似文献
1000.
The microstructure, hardness and corrosion resistance of commercially pure Ti treated by low energy high current pulsed electron beam (LEHCPEB) have been investigated. The thin near-surface melted layer rapidly solidified into β and subsequently transformed into ultrafine α′ martensite. This has led to a drastic improvement of the corrosion properties and a significant increase (more than 60%) in hardness of the top surface. 相似文献