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171.
A theoretical study was conducted on the size dependence of the blocking temperature Tb of a system of interacting core/shell nanoparticles. A method for estimating the blocking temperature of interacting core/shell nanoparticles is presented, which allows Tb to be calculated more precisely than using the “Neel relation”. It was shown that with an increase in the intensity of the magnetostatic interaction (concentration of nanoparticles), the blocking temperature increases, while the growth of the external magnetic field leads to the opposite effect. Moreover, the Tb of large nanoparticles changes more significantly. Comparing different approaches, we identify a precise method for determining the blocking temperature from ZFC and FC magnetization curves. 相似文献
172.
Functionally graded piezoelectric cantilever beam under load 总被引:3,自引:0,他引:3
Summary In the present paper, the problem of a functionally graded piezoelectric cantilever beam subjected to different loadings is studied. The piezoelectric beam is characterized by continuously graded properties for one elastic parameter and the material density. A pair of stress and induction functions in the form of polynomials is proposed and determined. Based on these functions, a set of analytical solutions for the beam subjected to different loadings is obtained. As particular cases, series of solutions for some canonical problems can be directly obtained from the solutions of the present paper, such as for the problems of a piezoelectric cantilever beam with constant body force or without body forces, etc.This research work is supported by the National Natural Science Foundation of China (50272003). Support was also given by the Teaching and Research Award Fund for Outstanding Young Teachers in Higher Education Institutions of MOE, P.R.C. 相似文献
173.
A simplified optimal control method is presented for controlling or suppressing homoclinic bifurcations of general nonlinear oscillators with one degree-of-freedom. The simplification is based on the addition of an adjustable parameter and a superharmonic excitation in the force term. By solving an optimization problem for the optimal amplitude coefficients of the harmonic and superharmonic excitations to be used as the controlled parameters, the force term as the controller can be designed. By doing so, the control gain and small optimal amplitude coefficients can be obtained at lowest cost. As the adjustable parameter decreases, a gain of some amplitude coefficient ratio is increased to the highest degree, which means that the region where homoclinic intersection does not occur will be enlarged as much as possible, leading to the best possible control performance. Finally, it is shown that the theoretical analysis is in agreement with the numerical simulations on several concerned issues including the identification of the stable and unstable manifolds and the basins of attraction. 相似文献
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Linping Mu Zhiqun He Prof. Xiangfei Kong Guanbao Hui Min Xu Chunjun Liang Dr. Xiping Jing Dr. Andrzej Danel Dr. Ewa Kulig Dr. 《Chemphyschem》2010,11(12):2623-2629
Pyrazolo[3,4‐b]quinoline derivatives are reported to be highly efficient organic fluorescent materials suitable for applications in light‐emitting devices. Although their fluorescence remains stable in organic solvents or in aqueous solution even in the presence of H2O, halide salts (LiCl), alkali (NaOH) and weak acid (acetic acid), it suffers an efficient quenching process in the presence of protic acid (HCl) in aqueous or ethanolic solution. This quenching process is accompanied by a change in the UV spectrum, but it is reversible and can be fully recovered. Both steady‐state and transient fluorescence spectra of 1‐phenyl‐3,4‐dimethyl‐1H‐pyrazolo‐[3,4‐b]quinoline (PAQ5) during quenching are measured and analyzed. It is found that a combined dynamic and static quenching mechanism is responsible for the quenching processes. The ground‐state proton‐transfer complex [PAQ5 ??? H+] is responsible for static quenching. It changes linearly with proton concentration [H+] with a bimolecular association constant KS=1.95 M ?1 controlled by the equilibrium dissociation of HCl in ethanol. A dynamic quenching constant KD=22.4 M ?1 is obtained by fitting to the Stern–Volmer equation, with a bimolecular dynamic quenching rate constant kd=1.03×109 s?1 M ?1 under ambient conditions. A change in electron distribution is simulated and explains the experiment results. 相似文献
177.
Se96Sn4 chalcogenide glass was prepared by melt quenching technique and exposed, at room temperature, to different doses of 4, 8, 12, 24 and 33 kGy of high-energy 60Co gamma irradiation. Differential scanning calorimeter (DSC) was used under non-isothermal condition to determine the glass transition temperature Tg, onset Tc and peak Tp temperatures of crystallization, of un-irradiated and γ-irradiated samples, at four different heating rates. The variation of Tg with heating rates was utilized to calculate the glass transition activation energy Et for un-irradiated and γ-irradiated glass, using the methods suggested by Kissinger and Moynihan. Based on the obtained values of the characteristic temperatures Tg, Tc and Tp, thermal stability was monitored through the calculation of the S parameter and the crystallization rate factor 〈Kp〉 for irradiated and un-irradiated glass. Results reveal that, as γ-dose increases Tg increases up to 12 kGy then decreases at higher doses but remains more than that of un-irradiated glass. Meanwhile, both Et and 〈Kp〉 attain their minimum values at the same dose of 12 kGy and the glass is thermally stable at this particular dose. 相似文献
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均匀分布参数的无偏估计及其分布 总被引:1,自引:0,他引:1
讨论了均匀分布未知参数无偏估计量的分布密度,利用无偏估计量构造出一些新的样本函数,并且利用给出的样本函数推导出了未知参数的置信区间.所得到结果改善了现有的估计,易于计算. 相似文献