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981.
M. A. Capano S. Ryu M. R. Melloch J. A. Cooper Jr. M. R. Buss 《Journal of Electronic Materials》1998,27(4):370-376
The activation of ion-implanted B into 4H-SiC, and B, and Al into 6H-SiC is investigated. Complete activation of B implants
into 4H-SiC is achieved by annealing at 1750°C for 40 min in an Ar environment. Significant activation (>10%) is not achieved
unless the annealing temperature is 1600°C or greater. Sheet resistances of Al-implanted 6H-SiC annealed at 1800°C are 32.2
kΩ/□, indicating high activation of Al at this temperature. Annealing conditions which result in good acceptor activation
are shown to be damaging to the surface of either 4H- or 6H-SiC. Atomic force microscopy and Nomarski differential interference
contrast optical microscopy are applied to characterize the surfaces of these polytypes. Roughening of the surfaces is observed
following annealing in Ar, with measured roughnesses as large as 10.1 nm for B-implanted 4H-SiC annealed at 1700°C for 40
min. Based on data obtained from these techniques, a model is proposed to describe the roughening phenomenon. The premise
of the model is that SiC sublimation and mobile molecules enable the surface to reconfigure itself into an equilibrium form. 相似文献
982.
983.
Manfred Sager 《Monatshefte für Chemie / Chemical Monthly》1987,118(1):25-29
A rapid method for the determination of fluorine in various matrices of geochemical and environmental interest is described. After fusion with NaOH, the sample is dissolved by means of tiron (= pyrocatechol-3,5-disulfonic acid, disodium salt), which acts both as buffer substance and as superior masking agent for cations exhibiting strong complexes with fluoride, e.g. Al, Fe, Ti etc. The final determination is done by means of the fluoride sensitive electrode without further separation.The applicability of the method has been checked for various silicates, bauxite, phosphates, soils, coal and plant material. A detection limit of 10 µg/g can be achieved, which is sufficient in many cases. The overall precision is better than ±10%.Dedicated to Prof. Dr.K. L. Komarek on occasion of his 60th birthday. 相似文献
984.
I. E. Tyschenko L. Rebohle R. A. Yankov W. Skorupa A. Misiuk G. A. Kachurin 《Journal of luminescence》1998,80(1-4):229-233
We have studied the influence of the hydrostatic pressure during annealing on the intensity of the visible photoluminescence (PL) from thermally grown SiO2 films irradiated with Si+ ions. Post-implantation anneals have been carried out in an Ar ambient at temperatures Ta of 400°C and 450°C for 10 h and 1130°C for 5 h at hydrostatic pressures of 1 bar–15 kbar. It has been found that the intensity of the 360, 460 and 600 nm PL peaks increases with rising hydrostatic pressure during low-temperature annealing. The intensity of the short-wavelength PL under conditions of hydrostatic pressure continues to rise even at Ta=1130°C. Increasing Ta leads to a shift in the PL spectra towards the ultraviolet range. The results obtained have been interpreted in terms of enhanced, pressure-mediated formation of ≡Si–Si≡ centres and small Si clusters within metastable regions of the ion-implanted SiO2. 相似文献
985.
Summary A group of 17 β-carbolines was studied in HPLC and TLC systems in order to predict their partition coefficients (log P values).
On account of the basic or acid character of some of these compounds, an ion pairing system gave the best results. Both HPLC
and TLC data were comparable for log P prediction but severe pH conditions required the use of TLC plates. Retention data
are quantitatively related to lipophilicity (expressed as the Hansch constant) and polarity (as the inductive constant) of
the solute molecule. 相似文献
986.
由Nd:YAG激光器三倍频,输出波长为λ=355 nm(28 169 cm~(-1))的激光光解NO_2分子产生的氧原子,通过共振增强多光子电离(REMPI resonance enhanced multiphoto ionization)及飞行时间(TOF time of flight)质谱技术,获得了自旋-轨道精细能级分辨的氧原子O(2 p~3P_J~″=2,1,0)离子谱.氧离子信号强度与UV电离激光能量(λ≈226 nm)之间的关系能用三次方曲线很好拟合,它表明光解产物氧原子是通过(2+1)多光子吸收过程而被电离的.由离子信号得到的氧原子基态三个自旋-轨道支能级布居比f_1=I(~3P_1)/I(~3P_2)与fo=I(~3P_0)/I(~3P_2)分别为0.54±0.09和0.20±0.04,并且在不同的光解激光能量下其布居比保持不变.这一比值与统计分布计算的值为0.6和0.2一致(即统计分布~3P_2:~3P_1:~3P_0=1:0.6:0.2).这是由于样品(NO_2)在较低的压力下(1.33×10~(-4)Pa)和极短的光解-电离时间范围内(10~(-8)s),产物O(~3P_J~″)支能级间几乎不可能发生碰撞能量转移,因此,氧原子三个自旋-轨道角动量分裂能级布居O(~3P_J~″=2,1,0)是统计分布的. 相似文献
987.
本文运用有关离子注入的原理和射程分布损伤机理等理论,结合作者所在工厂的硅栅CMOS工艺中应用全离子注入技术的实验数据及实践经验,对注入工艺参量与器件工艺参数的相关性及注入质量的控制等进行了探讨;就注入过程中的若干影响因素,寻求到了有效的解决方法。此技术已用于作者所在厂的我厂门阵列产品的研制和生产中,取得了令人满意的结果。 相似文献
988.
We have shown that poly(para-phenylene) (PPP) can be obtained either n-type or p-type by ion implantation at low energy (E ≦ 50 keV); PPP is primarily an insulator pellet obtained from compacted powder synthetised by the Kovacic method. To compare with the chemical doping effect, we have studied the conductivity and thermopower of PPP samples after two successive ion implantations with Cs+ and I+. The experimental results show that we clearly obtain reversible doping only in the case of an initially I+-doped sample: the thermopower sign is changed after a Cs+ implantation with a fluence equal to 3 × 1014 ions cm?2. In the other case (Cs+ initial implantation) we observe the change in thermopower sign at higher fluence (2 × 1016 I+ ions cm?2). This last effect can be attributed to a metal transition induced by the accumulation of defects in the material because of too high implantation parameters (graphitisation). 相似文献
989.
990.
Optical properties of SnO2 thin films in the 4–60 eV energy range are determined by reflection electron energy loss spectroscopy. Bulk and surface electron loss functions, real and imaginary parts of the dielectric function, refraction index, extinction and absorption coefficients are obtained from the analysis of the electron energy loss spectra. Electronic transitions are identified through the interpretation of the optical data. The samples (250–500 nm thick) were produced by ion beam-induced chemical vapor deposition. It is found that the compacity of the SnO2 thin films affects their optical properties and therefore the relative intensity of the observed electronic transitions. The advantages of this method to determine optical properties of thin films are discussed. Inelastic mean free paths (6.2, 17 and 41 Å for electrons traveling in SnO2 with kinetic energies of 300, 800 and 2000 eV, respectively) are obtained from the corresponding inelastic electron scattering cross-sections. 相似文献