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71.
An adaptive tracking design strategy based on quantized state feedback is developed for uncertain nonholonomic mobile robots with unknown wheel slippage effects. All state variables and control torques are assumed to be quantized by the state and input quantizers, respectively, in a network control environment. Thus, the quantized state feedback information is only available for the tracking control design. An approximation-based adaptive controller using quantized states is recursively designed to ensure the robust adaptive tracking against unknown wheel slippage effects where the quantized-states-based adaptive mechanism is derived to compensate for unknown wheel slippage effects, system nonlinearities, and quantization errors. The boundedness of the quantization errors and estimated parameters in the closed-loop system is analyzed by presenting some theoretical lemmas. Based on these lemmas, we prove the uniform ultimate boundedness of closed-loop signals and the convergence of the trajectory tracking error in the presence of wheel slippage effects. Simulations verify the effectiveness of the resulting tracking scheme. 相似文献
72.
Explosive synchronization in a mobile network in the presence of a positive feedback mechanism
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Synchronization is a process that describes the coherent dynamics of a large ensemble of interacting units.The study of explosive synchronization transition attracts considerable attention.Here,I report the explosive transition within the framework of a mobile network,while each oscillator is controlled by global-order parameters of the system.Using numerical simulation,I find that the explosive synchronization(ES)transition behavior can be controlled by simply adjusting the fraction of controlled oscillators.The influences of some parameters on explosive synchronization are studied.Moreover,due to the presence of the positive feedback mechanism,I prevent the occurrence of the synchronization of continuous-phase transition and make phase transition of the system a first-order phase transition accompanied by a hysteresis loop. 相似文献
73.
74.
G. Saravanan G. Jyothi Y. Suresh A. Annerao M. Ramakrishna M. Yogeshwar Reddy B. Ravibabu 《Chromatographia》2008,67(1-2):173-177
Levetiracetam is used in combination with other medications to treat certain types of seizures in people with epilepsy. Levetiracetam
is in a class of medications called anticonvulsants and it works by decreasing abnormal excitement in the brain. A chromatographic
separation was achieved on a YMC pack ODS AQ, 250 mm × 4.6 mm, 5 μm column using diluted phosphoric acid and acetonitrile
in the ratio 85:15 v/v. Forced degradation studies were performed on the levetiracetam drug substance. The drug substance was degraded to Imp-B
during acid and base hydrolysis. When the stress samples were assayed, the mass balance was matching. The sample solution
and mobile phase was found to be stable up to 48 h at 25 °C. The developed method was validated with respect to linearity,
accuracy, precision and robustness. 相似文献
75.
针对非连续路段下的轨迹跟踪问题,设计了基于观测型的预测控制器。首先建立了移动机器人的运动学模型,根据机器人的运动学模型得出了其位姿误差微分方程;然后在轨迹跟踪问题的基础上,设计了系统的观测模型,通过将预测控制器与系统的观测模型结合,设计了观测型预测控制器;最后再MATLAB环境下,利用本文所设计的控制器对移动机器人在非连续路段下的轨迹跟踪问题进行仿真,并将仿真结果与PID控制器控制的仿真结果进行对比,由仿真结果可以看出,本文所设计的控制器具有很好的鲁棒性、快速性及稳定性,可适用于移动机器人的轨迹跟踪的研究。 相似文献
76.
Touchscreen glasses of mobile phones are sensitive to ionizing radiation and have the potential of usage as an emergency dosimeter for retrospective dosimetry for the purpose of triage after a radiological accident or attack. In this study the TL glow curves and dosimetric properties of touchscreen glasses were studied in detail, such as intrinsic background dose, dose response, reproducibility, optical stability and long-term stability of the TL signal.Preliminary results are additionally presented to minimize the intrinsic background dose by mechanically removing the surface layer of the glass samples. Additionally chemical element analyses of the touchscreen glass samples were carried out to investigate the difference between glass samples which show a TL signal and samples which show neither an intrinsic zero dose signal nor a radiation induced TL signal.An irradiation trial using glass samples stored in the dark demonstrated a successful dose recovery. However, when applying a realistic, external light exposure scenario, dose underestimation was observed, even though samples were pre-bleached prior to measurement. More investigations have to be carried out in the future to solve the challenge of the low optical stability of the TL signal, if touchscreen glasses are to be used as a reliable emergency dosimeter. 相似文献
77.
78.
T. C. Uzomah 《Journal of polymer science. Part A, Polymer chemistry》2000,38(1):43-50
The solubility equation derived from the thermodynamics of mobile order theory was used (1) to predict the solubility of three solid n‐alkanes—octadecane, dotriacontane, and hexatriacontane—in nonassociated and self‐associated liquids at 25 °C and (2) to predict the increased solubility in particular solvents with increasing temperatures. The evolution of the predicted solubility rested on the relative importance of the different terms contributing to the solubility. Generally, the fluidization of the solute presented a reluctance to the solubility. In nonassociated liquids, the balance of placing the entropy correction and the change in the nonspecific cohesion forces played up, whereas in the hydrogen‐bonded liquids, the solubility was determined by the hydrophobic effect. The effect of increasing the temperature of the dissolution of the solute was a reduction in the negative fluidization and nonspecific cohesion forces, which resulted in increased solubility. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 43–50, 2000 相似文献
79.
In this study, size and shape controlled biogenic synthesis of gold nanoparticles and their antibacterial activity against food borne bacterial pathogens were investigated. Synthesis of gold nanoparticles was carried out using two medicinally important plants Cucurbita pepo and Malva crispa and the size and shape of the nanoparticles were controlled by altering various parameters in the reaction medium. Results obtained from UV–Vis, FE-SEM, EDS and HR-TEM analyses supported the nanoparticles formation. FT-IR analysis confirmed the presence of biomolecules in the plant leaves extracts responsible for reducing and capping agents. Interestingly, the plant extract synthesized gold nanoparticles showed effective inhibition zone against Gram-positive and Gram-negative pathogens. The minimum inhibitory concentration (MIC) of synthesized gold nanoparticles at 400 μg/ml concentration showed effective inhibitory activity against Escherichia coli and Listeria monocytogenes. Conductivity of the medium continuously increased during the nanoparticles treatment with food borne bacterial pathogens resulting in indirect indication of the disruption of bacterial cell membranes. In addition, mode of interactions of gold nanoparticles against food borne bacterial pathogens was demonstrated using Bio-TEM analysis which is clear evident for the disruption of bacterial cell membranes. 相似文献
80.
结合吖啶基C60吡咯烷单加成衍生物的分离,具体介绍了柱色谱分离法的原理、固定相和流动相的选择、分离操作的过程及样品的后处理,便于大家能更具体地认识这种物质分离的方法。 相似文献