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261.
The electrocatalytic oxidation of oxalate at several carbon based electrodes including basal plane (BPPG) and edge plane (EPPG) pyrolytic graphite and glassy carbon (GC) electrode, was studied. The electrodes were examined for the sensing of oxalate ions in aqueous solutions and all three electrodes showed a response to oxalate additions. The peak of oxalate oxidation at BPPG electrode appeared at lower potential, +1.13 V vs. SCE, than at EPPG (+1.20 V vs. SCE) and GC electrode (+1.44 V vs. SCE). Oxalate oxidation at BPPG electrode was studied in more details for response characteristics (potential and current), effects of pH, temporal characteristics of response potential and current. The results indicated that oxalate oxidation proceeds as two‐electron process at the BPPG electrode with a transfer coefficient β and a diffusion coefficient D evaluated to be 0.45 and 1.03 (±0.04)×10?5 cm2 s?1 respectively. The BPPG electrode was found to be suitable for oxalate determination in aqueous media showing linear response to oxalate concentration with a sensitivity of 0.039 AM?1 and a limit of detection of 0.7 μM. 相似文献
262.
263.
Control of the interparticle spacing in superparamagnetic iron oxide nanoparticle clusters by surface ligand engineering 下载免费PDF全文
Polymer-mediated self-assembly of superparamagnetic iron oxide(SPIO) nanoparticles allows modulation of the structure of SPIO nanocrystal cluster and their magnetic properties. In this study, dopamine-functionalized polyesters(DApolyester) were used to directly control the magnetic nanoparticle spacing and its effect on magnetic resonance relaxation properties of these clusters was investigated. Monodisperse SPIO nanocrystals with different surface coating materials(poly(ε-caprolactone), poly(lactic acid)) of different molecular weights containing dopamine(DA) structure(DA-PCL2k,DA-PCL1k, DA-PLA1k)) were prepared via ligand exchange reaction, and these nanocrystals were encapsulated inside amphiphilic polymer micelles to modulate the SPIO nanocrystal interparticle spacing. Small-angle x-ray scattering(SAXS)was applied to quantify the interparticle spacing of SPIO clusters. The results demonstrated that the tailored magnetic nanoparticle clusters featured controllable interparticle spacing providing directly by the different surface coating of SPIO nanocrystals. Systematic modulation of SPIO nanocrystal interparticle spacing can regulate the saturation magnetization(Ms) and T_2 relaxation of the aggregation, and lead to increased magnetic resonance(MR) relaxation properties with decreased interparticle spacing. 相似文献
264.
基于超小型P13XM015型TFT-LCD技术的小型星模拟器的工作原理,及其在工程应用中整个系统的设计、制造、加工、调试和检测技术,提出对星间间距采用软件修正以及先分别测量再组合修正的方法,对星等采用使用相适应的仪器星等的方法。采用模块化方法设计了小型星模拟器系统的光学系统准直物镜、模拟星库的编制、坐标转换、位置解算、系统控制软件等。在实验室实现了整个系统的组装,搭建了控制和测试平台,并给出了实验结果。实验结果表明:本系统的星库精度及星位置解算误差12,角分辨率误差23.43。 相似文献
265.
Basal plasma-catecholamine-level determination using HPLC-ED and different sample cleanup techniques
Summary Reversed phase HPLC with electrochemical detection was used for the determination of basal adrenaline, dopamine and noradrenaline
levels in human plasma. These compounds demonstrated good stability during different stages of collection and long-term storage.
Using a new electrochemical detector and improving mobile phase parameters, we obtained a detection limit of 2 pg per injection.
Good separation of dihydroxyphenylacetic acid was also attained, which is important in investigations with intensive care
patients.
Good accuracy and precision, demonstrated in the daily quality control measurements taken over a five month period, verified
the reliability of the chromatographic separation.
However, there was a decrease in the recovery of very low amounts of catecholamines, added to fresh frozen plasma that had
previously been made catecholamine-free. According to the widely-accepted extraction method of Anton and Sayre, it is argued
that the un-known affinity of catecholamines to acid-prepared aluminium oxide (in comparison to catecholamine —protein binding
constants) explains the low accuracy in measurement at very low plasma levels. We thus compared this sample preparation method
to recently published extraction procedures. 相似文献
266.
一前言 Legg和Jona等观测与计算了Fe{001}c(2×2)-S和Fe{001}-O表面的LEED谱,并发现衬底第一原子层间距几乎不变。Simmons等和Bruncker等观测了覆盖度θ=0.5L的Fe{001}c(2×2)-O表面的LEED图,但未获得其LEED谱。Legg等观测与计算了覆盖度θ=1L的Fe{001}(1×1)-O表面的LEED谱,并发现衬底第一原子层 相似文献
267.
We have proposed and discussed a design of arrayed waveguide grating (AWG) for the application of wavelength interrogation. The spectral responses of a silica-based 16 channel AWG with channel spacing 1.6 nm have been simulated when different receiver waveguide spacing are used. It was found that the 3-dB bandwidth is reduced about 50% as the receiver waveguide spacing increasing from 20 μm to 30 μm. The effect of bandwidth of the spectral response on wavelength resolution of AWG based interrogator has been estimated and discussed. 相似文献
268.
Schure MR 《Journal of chromatography. A》2011,1218(2):293-302
The box-counting or capacity dimension algorithm, known from the fractal mathematics literature, is used to measure the dimensionality D of chromatographic separation techniques for any number of dimensions. It is shown that D has limit properties that match Giddings' sample dimensionality s. D values are shown to be sensitive to the uniformity of peak spacing. A number of examples are given where D is calculated for various limits in one- and two-dimensional separations and for heart-cutting separations. The use of D as a quantitative measure of multidimensional orthogonality is suggested as D, due to the scale-free nature, is not dependent on the effective separation area. The connection to statistical peak overlap theory is discussed. 相似文献
269.
Tunable and switchable all-fiber comb filter using a PBS-based two-stage cascaded Mach-Zehnder interferometer 总被引:1,自引:0,他引:1
We propose and demonstrate a novel tunable and switchable all-fiber comb filter by employing a polarization beam splitter (PBS)-based two-stage cascaded Mach-Zehnder (M-Z) interferometer. The proposed comb filter consists of a rotatable polarizer, a fiber PBS, a non-3-dB coupler and a 3-dB coupler. By simply adjusting the polarization state of the input light, the dual-function of channel spacing tunable and wavelength switchable (interleaving) operations can be efficiently obtained. The theoretical analysis is verified by the experimental results. A comb filter with both the channel spacing tunable from 0.18 nm to 0.36 nm and the wavelength switchable functions is experimentally demonstrated. 相似文献
270.
The atomic arrangement and distribution of oxides (Cr2O3, NiCr2O4 and NiO) on the sprayed-NiCoCrAlY coating after oxidation are analyzed. The formation and the growth model of Ni-Cr oxide phases are discussed according to the matching relationship between atoms. The outline character and a scale of spinel NiCr2O4 are discussed. The results show that Cr atoms can form two close-packed arrangements in the crystal plane of Cr2O3 perpendicular to 〈0 0 1〉 orientation. The atomic spacing in the first arrangement corresponds to double that of Ni/Ni3Al in {1 1 1} crystal face. This suggests that Ni/Ni3Al is the substrate for Cr2O3 to grow along 〈0 0 1〉 direction. The lattice mismatch between Cr2O3 and Ni/Ni3Al is less than that of Al2O3, which indicates that Cr2O3 is easier to form than Al2O3 during the oxidation process. The atomic spacing in another close-packed arrangement of Cr2O3 perpendicular to 〈0 0 1〉 orientation is approximately equal to that of Ni or Cr in the plane of NiCr2O4 and NiO perpendicular to 〈1 1 1〉 orientation. So Cr2O3 can be the substrate for NiCr2O4 and NiO to grow in the 〈0 0 1〉 direction. NiCr2O4 and NiO can grow directly along the 〈1 1 1〉 orientation on each other. NiCr2O4 can grow outward in the planes of Cr2O3 perpendicular to 〈0 0 1〉 and grow inward along 〈1 1 1〉 orientation of NiO. 相似文献