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991.
用低杂波鉴相器对相位测量系统各通道经进行了相位校准,得到了各通道的相位电压关系曲线,并进行了线性拟合,线性拟合误差小于3°;推导出了相位电压关系表达式,与校准得到的相位电压曲线相比平均误差小于0.7°。该系统已成功用于HL-2A 装置低杂波实验,对4 支速调管的输出相位进行了测量,并得到了放电过程中相位随阴极高压波动的曲线,得出了阴极电压波动2.2%引起相位波动13.8°的结论。 相似文献
992.
993.
Sampling strong tracking nonlinear unscented Kalman filter and its application in eye tracking
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The unscented Kalman filter is a developed well-known method for nonlinear motion estimation and tracking. However, the standard unscented Kalman filter has the inherent drawbacks, such as numerical instability and much more time spent on calculation in practical applications. In this paper, we present a novel sampling strong tracking nonlinear unscented Kalman filter, aiming to overcome the difficulty in nonlinear eye tracking. In the above proposed filter, the simplified unscented transform sampling strategy with n+2 sigma points leads to the computational efficiency, and suboptimal fading factor of strong tracking filtering is introduced to improve robustness and accuracy of eye tracking. Compared with the related unscented Kalman filter for eye tracking, the proposed filter has potential advantages in robustness, convergence speed, and tracking accuracy. The final experimental results show the validity of our method for eye tracking under realistic conditions. 相似文献
994.
We introduce the potential-decomposition strategy (PDS), which can be used in Markov chain Monte Carlo sampling algorithms. PDS can be designed to make particles move in a modified potential that favors diffusion in phase space, then, by rejecting some trial samples, the target distributions can be sampled in an unbiased manner. Furthermore, if the accepted trial samples are insufficient, they can be recycled as initial states to form more unbiasedsamples. This strategy can greatly improve efficiency when the original potential has multiple metastable states separated by large barriers. We apply PDS to the 2d Ising model and a double-well potential model with a large barrier, demonstrating in these two representative examples that convergence is accelerated by orders of magnitude. 相似文献
995.
996.
A. Alsaad A. Ahmad 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(1):65-77
Theoretical results are presented regarding the incorporation of Scandium into wurtzite GaN and InN binaries. The electric,
optical and piezoelectric properties of the resulting ScGaN and ScInN systems are reported by using first-principles Local-density
approximation (LDA) within density functional theory (DFT), Berry phase approach within modern theory of polarization and
phonon calculations within the density functional perturbation theory. Our results predict the existence of breaking-symmetry
structural phase transition in ordered Sc0.5Ga0.5N and Sc0.5In0.5N alloys when subjected to a compressive or tensile strain. Moreover, our results demonstrate the existence of symmetry preserving pressure-induced isostructural phase transitions
in ordered ScGaN and ScInN systems for different Sc concentrations. It has been shown that the existence of isostructural
phase transitions leads to dramatic changes in optical, acoustic, and piezoelectric properties of ordered ScGaN and ScInN
systems under high pressure. In particular, this study demonstrates that the existence of first-order isostructural phase
transitions in Sc1Ga1N2 at a critical hydrostatic pressure of 12.3 GPa leads to a huge enhancement of piezoelectricity (i.e., the e
33 piezoelectric coefficient adopts a huge value as large as 13 C/m2). In addition, It has been shown that ordered Sc0.5Ga0.5N and Sc0.5In0.5N alloys exhibit tremendous piezoelectric response, associated with a breaking-symmetry phase transition from nonpolar P63/mcc(D6h) space group to a polar P63
mc(C6v) structure, at fixed Ga, In and Sc compositions, as a function of the in-plane compressive and tensile strains. We also reveal
the reason behind, and consequences of, these unusual properties associated with the strain-induced and pressure-induced structural
phase transitions in the novel ScGaN and ScInN ordered structures. 相似文献
997.
998.
Gledhill JM Joshua Wand A 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2008,195(2):169-178
Sparse sampling offers tremendous potential for overcoming the time limitations imposed by traditional Cartesian sampling of indirectly detected dimensions of multidimensional NMR data. Unfortunately, several otherwise appealing implementations are accompanied by spectral artifacts that have the potential to contaminate the spectrum with false peak intensity. In radial sampling of linked time evolution periods, the artifacts are easily identified and removed from the spectrum if a sufficient set of radial sampling angles is employed. Robust implementation of the radial sampling approach therefore requires optimization of the set of radial sampling angles collected. Here we describe several methods for such optimization. The approaches described take advantage of various aspects of the general simultaneous multidimensional Fourier transform in the analysis of multidimensional NMR data. Radially sampled data are primarily contaminated by ridges extending from authentic peaks. Numerical methods are described that definitively identify artifactual intensity and the optimal set of sampling angles necessary to eliminate it under a variety of scenarios. The algorithms are tested with both simulated and experimentally obtained triple resonance data. 相似文献
999.
1000.
顶空采样-毛细管气相色谱法分析格列美脲原料药中的溶剂残留 总被引:4,自引:0,他引:4
建立了顶空采样-毛细管气相色谱检测格列美脲原料药中溶剂残留的分析方法。对产自国内8个生产厂家的格列美脲样品中有机溶剂的残留状况进行了系统评价,结合药品生产工艺信息,确定了丙酮、乙酸乙酯、甲醇、异丙醇、乙醇、氯仿、甲苯、1,4-二氧六环、吡啶、氯苯、乙醚、二氯甲烷、正己烷和苯等14种有机溶剂为残留检测对象。根据被测组分在色谱柱上的保留性质将其分为两类,以实现基线分离。用Supelco-Wax极性色谱柱,以乙腈为内标物,分离检测了丙酮、乙酸乙酯、甲醇、异丙醇、乙醇、氯仿、甲苯、1,4-二氧六环、吡啶和氯苯的残留量;用Supelco OVI-G43弱极性色谱柱,以丁酮为内标,分离检测了乙醚、二氯甲烷、正己烷和苯的残留量。14种残留组分在各自的浓度范围内呈良好的线性关系(r=0.99167~0.99997,n=8),最低检出限范围为0.2~13.5 μg/g;14种残留组分检测的日间重复性(以相对标准偏差(RSD)计)为0.6%~9.2%(n=3),3种加标浓度的平均添加回收率为86.3%~104.1%(RSD为0.2%~5.3%,n=16)。实验结果表明,该方法简单、灵敏、可靠,适用于格列美脲中残留溶剂的分析确证。 相似文献