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81.
82.
The branching ratio, the photoemission intensity ratio of two spin-orbit-split components, has been applied for the first time as a means for obtaining a photoelectron holographic image. Angle-resolved photoemission from a monolayer of Bi adsorbed on Si(111) shows fine-structure oscillations in the branching ratio of the Bi 5d core level due to diffraction effects. These oscillations as a function of photon energy are recorded for a number of emission angles. Three-dimensional holographic inversion of the data yields an atomic image which shows that the Bi adatoms are arranged in a trimer structure. 相似文献
83.
强场作用下二能级原子双光子过程中辐射场的压缩效应 总被引:4,自引:2,他引:2
本文采用数值计算方法研究了强场作用下二能级原子双光子过程中辐射场的压缩效应.结果表明:辐射场主要处于压缩态,并周期性地出现短时的非压缩效应,随着值的不断增大,场与原子的非线性耦合越来越强,压缩的最大深度不断加深. 相似文献
84.
Sunil Kumar 《Pramana》1985,25(3):291-309
The theory of the coherent, two-photon resonant interaction of a monochromatic field with N atoms is given. It is seen that
the dynamics of the atom-field system can be completely determined when the field is “strong”. Two specific examples are given:
(i) two-photon absorption by atoms in ground state, and (ii) stimulated two-photon emission by fully excited atoms, assuming
a coherent field in both cases. In case (ii), the field shows photon-antibunching after the decay of half of the atoms. The
merits of our approach are shown by comparing with other treatments. Our results can also be applied to certain degenerate
four-wave mixing processes which are described by a similar Hamiltonian. 相似文献
85.
将三阶微扰理论应用于单晶GaAs半导体,结合与实际相接近的能带结构,得到了GaAs中三光子吸收系数的解析式表达式,在考虑了激发电子的逃逸过程的情况下,进而推导了负电子亲和势GaAs光电阴极中三光子光电发射的发射系数的解析表达式.两表达式得到的理论数值分别与用ns量级脉宽、2.06μm波长的激光测得的GaAs中三光子吸收系数和GaAs(Cs,O)光电阴极中三光子发射系数的实验值相比较,吻合较好. 相似文献
86.
We have investigated the third-order nonlinear optical parameters of Bischalcones embedded in DMF solution and in solid PMMA matrix, by Z-scan technique using nanosecond laser pulse trains at 532 nm. Z-scan results reveal that the Bischalcones exhibits negative nonlinear refractive index as high as 10−11 esu. The molecular two-photon absorption cross-section of Bischalcones were of the order 10−46 cm4 s/photon, which is nearly two orders of magnitude larger than that of Rhodamine 6G which is 10−48 - 10−50 cm4 s/photon. We found that, the two-photon absorption (TPA) is the dominating nonlinear process leading to nonlinear absorption in both the cases in solution and as well as in solid medium. Based on TPA process, the Bischalcones exhibit good optical power limiting of nanosecond laser pulses at the input wavelength. The nonlinear optical parameters found to increase on enhancing the strength of the electron donor groups indicating the dependence and importance of electron donor/acceptor units on third-order nonlinear optical susceptibility χ(3). 相似文献
87.
In the present work, a Michelson interferometer was combined with a two-photon excitation microscope to perform two-focus
Fluorescence Correlation Spectroscopy. This simple and original approach allows us to tune the distance between the two excitation
volumes and determine absolute diffusion constants. The technique was validated on different model systems that demonstrate
the sensitivity of the approach. 相似文献
88.
Takashi Fujikawa Hiroko Arai Rie Suzuki Hiroshi Shinotsuka Lszl Kvr Nobuo Ueno 《Journal of Electron Spectroscopy and Related Phenomena》2008,162(3):146-157
Recoil effects of photoelectrons excited by high-energy X-rays are studied beyond the simplest approximation where elastic scatterings of photoelectrons are completely neglected (single-site approximation). At first we have shown that the simple free atom energy shift is accurately obtained within the harmonic and the single-site approximations. Beyond the single-site approximation, this simple formula does not work, but still simple classically acceptable formula can be used to explain the recoil energy shift. Illustrative numerical calculations show that the energy shifts caused by the photoelectron diffraction amounts to 5–8 meV for graphite-like carbon and about 100 meV for LiI6 cluster at ?k=5–7 keV, and show oscillations as functions of the photoelectron energy. Furthermore we discuss the recoil effects in photoemission from extended levels by use of the tight-binding approach. Our approach naturally provides not only Debye–Waller factors but also the recoil factors. In addition to the phonon excitation, we also study the recoil effects associated with plasmon losses where intrinsic and extrinsic processes can interfere each other. Only the latter can contribute to the recoil energy shift. 相似文献
89.
J.F. Sánchez-Royo J. Pellicer-Porres S.J. Gilliland A. Chevy 《Surface science》2007,601(18):3778-3783
The electronic properties of InSe/M (M Pd, Au) interfaces have been studied by X-ray photoemission measurements. For the InSe/Pd interface, it has been found that Pd atoms diffuse into the InSe lattice at early stages of Pd coverage, acting as acceptor centers. As the Pd coverage increases, a Pd-InSe reaction determines the electronic behaviour of the interface. However, for Pd coverages higher than 1 ML, the barrier formation tends to be controlled by an emerging bulklike Pd overlayer. Despite the atomic structure of this system is far from that expected for an ideal Schottky one, the final electronic barrier value is close to that expected for an abrupt InSe/Pd Schottky interface. On the contrary, the InSe/Au system appeared to behave as a quasi-ideal abrupt Schottky interface. Annealing processes performed at temperatures higher than 600 K alter this scheme, as revealed by X-ray absorption spectroscopy measurements, enhancing diffusion of Au atoms into InSe. In any case, the electronic barrier results to be determined by the Au overlayer formed. 相似文献
90.
《Physics and Chemistry of Liquids》2012,50(4):507-519
Abstract A new dye Trans-4-[p-(N-hydroxyethyl-N-ethyiamino)styryl]-N-methylpyridinium p-toluene sulfonate (HEASPS) was synthesized, and the two-photon absorption (TPA), TPA-induced frequency up-conversion emission, and two-photon pumped (TPP) frequency up-converted lasing properties of this new dye were experimentally studied. This new dye has a moderate TPA cross-section of\sigma2 = 4.7 × 10?48 cm4 .s/photon at 1064nm, but exhibits a high lasing efficiency. The net conversion efficiency from the absorbed 1064 nm pump pulse energy to the 626 nm up-converted lasing energy is 18.2% at the pump energy level of 1.9 mJ. 相似文献