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981.
S. C. Huang H. L. Chang K. W. Su A. Li S. C. Liu Y. F. Chen K. F. Huang 《Applied physics. B, Lasers and optics》2009,94(3):483-487
An AlGaInAs quantum-well structure grown on a Fe-doped InP transparent substrate is developed to be a gain medium in a high-peak-power
nanosecond laser at 1570 nm. Using an actively Q-witched 1064 nm laser to pump the gain chip, an average output power of 135 mW
is generated at a pulse repetition rate of 30 kHz and an average pump power of 1.25 W. At a pulse repetition rate of 20 kHz,
the peak output power is up to 290 W at a peak pump power of 2.3 kW. 相似文献
982.
983.
To address two challenging problems in infrared target tracking, target appearance changes and unpre- dictable abrupt motions, a novel particle filtering based tracking algorithm is introduced. In this method, a novel saliency model is proposed to distinguish the salient target from background, and the eigenspace model is invoked to adapt target appearance changes. To account for the abrupt motions efficiently, a two- step sampling method is proposed to combine the two observation models. The proposed tracking method is demonstrated through two real infrared image sequences, which include the changes of luminance and size, and the drastic abrupt motions of the target. 相似文献
984.
985.
Rotational viscosity of a liquid crystal mixture: a fully atomistic molecular dynamics study 下载免费PDF全文
Fully atomistic molecular dynamics (MD) simulations at 293, 303 and
313~K have been performed for the four-component liquid crystal
mixture, E7, using the software package Material Studio. Order
parameters and orientational time correlation functions (TCFs) were
calculated from MD trajectories. The rotational viscosity
coefficients (RVCs) of the mixture were calculated using the
Nemtsov--Zakharov and Fialkowski methods based on
statistical-mechanical approaches. Temperature dependences of RVC
and density were discussed in detail. Reasonable agreement between
the simulated and experimental values was found. 相似文献
986.
We report that two-photon absorption (TPA) properties of semiconductor CdSe-core CdS/ZnS-multishell quantum dots (QDs) in
toluene under excitation of femtosecond laser at 800 nm. The results show efficient TPA process and large TPA cross section
of three types of size QDs, which is 1900, 5710, and 16060 GM (1 GM = 10−50 cm4 s photon−1), respectively. TPA cross section dramatically increases with increased core size, showing a strong size-dependence effect.
Furthermore, two-photon excitation (TPE) fluorescence intensity not only depends on TPA capacity, but also relies on improved
quantum yield resulting from passivation of QD surface by different coated monolayers (MLs). These facts in combination with
the narrow fluorescence bandwidth make these QDs as promising probes for multicolor two-photon microscopy. 相似文献
987.
Influence of annealing temperature on microstructure and optical properties of sol-gel derived tungsten oxide films 总被引:1,自引:0,他引:1
Tungsten oxide (WO3) thin films have been extensively studied for their interesting physical properties and a variety of potential applications in electrochromic devices. In order to explore the possibility of using these in electrochromic devices, a preliminary and thorough study of the optical properties of the host materials is an important step. Based on this, the influence of annealing temperature on the structural, surface morphological, optical and electrochromic properties has been investigated in the present work. The host material, WO3 films, has been prepared from an ethanolic acetylated peroxotungstic acid sol containing 5 wt.% oxalic acid dehydrate (OAD) by sol-gel technique. The monoclinic structure and textured nature change of the films with the temperature increasing have been investigated by X-ray diffraction analysis. The surface morphology evolution of the films has been characterized by SEM. The shift in absorption edge towards the higher wavelength region observed from optical studies may be due to the electron scattering effects and the optical band filling effect that reveals the crystallization of the film. The amorphous film shows better optical modulation (ΔT = 76.9% at λ = 610 nm), fast color-bleach kinetics (tc ∼ 4 s and tb ∼ 9 s) and good reversibility (Qb/Qc = 90%), thereby rendering it suitable for smart window applications. 相似文献
988.
18Ni-maraging steel has been entirely nanocrystallized by a series of processes including solution treatment, hot-rolling deformation, cold-drawn deformation and direct electric heating. The plasma nitriding of nanocrystallized 18Ni-maraging steel was carried out at 410 °C for 3 h and 6 h in a mixture gas of 20% N2 + 80% H2 with a pressure of 400 Pa. The surface phase constructions and nitrogen concentration profile in surface layer were analyzed using an X-ray diffractometer (XRD) and the glow discharge spectrometry (GDS), respectively. The results show that an about 2 μm thick compound layer (mono-phase γ′-Fe4N) can be produced on the top of the surface layer of nanocrystallized 18Ni-maraging steel plasma nitrided at 410 °C for 6 h. The measured hardness value of the nitrided surface is 11.6 GPa. More importantly, the γ′-Fe4N phase has better plasticity, i.e., its plastic deformation energy calculated from the load-displacement curve obtained by nano-indentation tester is close to that of nanocrystallized 18Ni-maraging steel. Additionally, the mechanical properties of γ′-Fe4N phase were also characterized by first-principles calculations. The calculated results indicate that the hardness value and the ratio of bulk to shear modulus (B/G) of the γ′-Fe4N phase are 10.15 GPa and 3.12 (>1.75), respectively. This demonstrates that the γ′-Fe4N phase has higher hardness and better ductility. 相似文献
989.
Rongrong Zhang Ahmed Yousif Ghazal Yuzhu Liu Yan Zhang Bifeng Tang 《Optics Communications》2009,282(11):2169-6193
The photodissociation dynamics of iodocyclohexane (C6H11I) at 266 and 277 nm has been investigated by ion velocity imaging technique. The velocity distributions, angular distributions and relative quantum yields are obtained for I (2P3/2) (denoted I) and I (2P1/2) (denoted I*) fragments. The energy partitioning shows that about 70% of the available energy goes into the internal excitation of the photofragments for both dissociation channels. From the angular distributions, we found the value of the anisotropy parameter β for I* at the corresponding excitation wavelength was less than that for I. Based on the measured angular distributions and relative quantum yields, the relative fractions of each excited state to the products are determined. The curve crossing probabilities between the 3Q0 and 1Q1 states are determined 0.503 at 266 nm and 0.443 at 277 nm. 相似文献
990.
Differential phase shift quantum key distribution scheme has been improved by introducing a passive path selection structure at the transmitter including two polarization controllers used to mark the photon pulses and a polarizing beam splitter to distinguish these pulses so that can make different time delay at the receiver. Theoretical analysis indicates that a free-space-based differential phase shift quantum key distribution system with this proposed improvement will have high efficiency with the utilization ratio of photons reaching 100% under ideal condition. 相似文献