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1.
The feasibility of electrosynthesis of coenzyme Q10 (1) by electrooxidation of tetramethoxy precursor (2) has been investigated at carbon, Pt and BDD anodes in a divided cell. The process strongly depends on the applied potential, anode material and water content of the solvent. At carbon anodes in CH3CN/CH2Cl2 + 0.15 M Bu4NBF4 at proper operative conditions high faradic efficiency (>60%) and excellent selectivity (95–97%) of the target product were obtained.  相似文献   
2.
A simple template-directed wet chemistry route based on traditional thermal decomposition technique has been developed for the preparation of high-density, ordered ZnO nanowire arrays. The fabrication was performed at relative low temperature without involving complex procedures, sophisticated equipment and rigorous experiment conditions, thereby providing a straightforward and mild method to produce metal/metal oxide ordered nanostructures. The nanowire array system was evaluated by SEM, XRD, TEM and PL. A stable luminescence at 425 nm was present.  相似文献   
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4.
Let R be a ring, M be a R-bimodule and m, n be two fixed nonnegative integers with m + n = 0. An additive mapping δ from R into M is called an(m, n)-Jordan derivation if(m +n)δ(A~2) = 2 mAδ(A) + 2nδ(A)A for every A in R. In this paper, we prove that every(m, n)-Jordan derivation with m = n from a C*-algebra into its Banach bimodule is zero. An additive mappingδ from R into M is called a(m, n)-Jordan derivable mapping at W in R if(m + n)δ(AB + BA) =2mδ(A)B + 2 mδ(B)A + 2 nAδ(B) + 2 nBδ(A) for each A and B in R with AB = BA = W. We prove that if M is a unital A-bimodule with a left(right) separating set generated algebraically by all idempotents in A, then every(m, n)-Jordan derivable mapping at zero from A into M is identical with zero. We also show that if A and B are two unital algebras, M is a faithful unital(A, B)-bimodule and U = [A M N B] is a generalized matrix algebra, then every(m, n)-Jordan derivable mapping at zero from U into itself is equal to zero.  相似文献   
5.
菜籽油在加工及贮藏过程中,易受氧气、温度、光照等因素的影响,产生氧化酸败现象。为准确判断油脂氧化程度,实现不同氧化模式下菜籽油品质的快速判别,采用三维同步荧光光谱技术结合平行因子分析法及BP神经网络法建立菜籽油氧化状态的智能评价模型。以冷榨菜籽油为原料,将样品分别置于常温、Schaal烘箱、高温模式中氧化处理,期间采集菜籽油的三维同步荧光光谱数据及理化指标,当理化指标超出国标限定范围时,停止采集数据。结果表明,菜籽油中荧光物质在不同氧化模式中的演变规律呈显著差异,氧化温度对菜籽油荧光光谱有明显影响。常温氧化350 d与第1 d相比,菜籽油的特征荧光峰位置无变化,仅在激发波长Ex为620和660 nm附近荧光峰强度发生微弱变化;Schaal烘箱氧化26 d后,在激发波长Ex为620和660 nm附近荧光峰强度显著减弱,且在激发波长Ex为350~450 nm之间有新的荧光峰生成;高温氧化48 h后,Ex为620和660 nm处荧光峰消失,在Ex为400~550 nm处产生显著荧光峰,相对Schaal烘箱氧化,荧光波长发生一定程度红移,这是由于高温氧化过程中油脂氧化生成的物质稳定性较差引起的。利用平行因子分析法对三维同步荧光光谱数据进行分解获取有效的二维荧光光谱数据,当组分数为6,Δλ=60 nm时激发波长的载荷值最大,不同样品间差异最显著。选定Δλ=60 nm波段的二维荧光光谱数据用于智能评价,作为BP神经网络模型的输入值,以极性组分作为模型输出值,分别对菜籽油三种氧化模式数据建模训练。实验结果表明,三种氧化模式对应的训练集、验证集、测试集模型相关系数r均能达到0.9以上,其中常温氧化模式中验证集及测试集模型的相关系数r为1,输出值与目标值较接近,模型的预测效果较好;综合三种氧化模式数据建模,对应训练集、验证集、测试集模型的相关系数分别为0.999,0.913和0.988,均方误差均较小,说明该模型能准确判断菜籽油的不同氧化状态。因此,三维同步荧光光谱技术结合平行因子分析法、BP神经网络法建立快速检测模型能实现菜籽油不同氧化状态的判别,为菜籽油的氧化程度的评价提供新方法,同时为其他食用油的品质评价提供参考。  相似文献   
6.
In this paper, an experiment is proposed to select longitudinal ultrasonic waves as the physical agent in the detection of tensile stress states. The delay time in the back-wall echo travel presents a relation with the strain usually considered in tensile tests. From an algebraic manipulation procedure, this time interval is the fundamental quantity in the proposed method. The theoretical development initiates from the sound velocity in the unstressed state and employs a perturbative method to quantify the changes in the time-of-flight due to both the dimension modifications and the acoustoelastic effect. In addition to Armco iron and rail steel, this study applies its mathematical model to metal-matrix composites of aluminium and SiC particles at different temperatures. The scheme requires one transducer to perform the corresponding measurements to evaluate if a metallic material is under tensile stress.  相似文献   
7.
This paper proposes a damage detection method with two phases, namely, localization and quantification, for beam structures subjected to moving load and successfully validates it via a laboratory experiment. Firstly, the discrete wavelet transform (DWT) is applied to decompose the displacement response change induced by a moving vehicle and locate potential structural damages. Then adaptive-scale wavelet finite element model (WFEM) updating is employed to estimate the damage severity in the identified damage regions in a progressive fashion. The elemental scales of WFEM are adaptively changed according to not only the moving vehicle position but also the progressively identified damage regions. Such a method can effectively minimize the number of modeling degree-of-freedoms (DOFs) and updating parameters during optimization. The feasibility and effectiveness of the proposed method is examined through a laboratory experiment with different damage scenarios. The results indicate the proposed method can achieve good consistency between structural modeling, damage scenarios, and load conditions, as well as an optimal tradeoff between damage detection accuracy and efficiency.  相似文献   
8.
The optical rectification (OR) in the two-dimensional electron–hole system is investigated theoretically. An analytical expression formula of the OR coefficient is obtained via the framework of compact density matrix approach and the iterative method. The results show that the OR coefficient depends strongly on the system׳s size and the relaxation time. A more obvious OR coefficient should be found by adjusting an appropriate choice of the system parameters.  相似文献   
9.
A new type of phase-shifting interferometer was presented by rotating an azo-polymer film with photo-induced optical anisotropy in the light path of orthogonal polarization interferometry. By changing the angle of the optical axis of the azo-polymer film, four phase-shifted fringe patterns were obtained, from which phase difference between orthogonal polarized light could be calculated. The polarization states and the formation of the interferograms were analyzed theoretically using Jones matrix calculations and the experimental verification of the proposed method was also given. This method has a simple optical configuration which utilizes commercially available polarization devices and anisotropic azo-polymer film of low cost. The phase-shifting interferometer also demonstrates a new application of azo-polymer film.  相似文献   
10.
采用水热法在温和的条件下合成了具有规则外形的六方棱柱状NaNdF4纳米棒。X射线衍射(XRD)分析表明:产物为纯六方相NaNdF4,场发射扫描电镜(SEM)分析表明产物形貌为棱柱状纳米棒,长约为550nm,棒的端部呈规则六边形,边长约为85nm。高分辨透射电子显微镜(HRTEM)和选区电子衍射(SD)显示所得样品为良好的单晶。NaNdF4晶体的生长动力学过程表明:螯合剂(EDTA-Na2)与稀土金属离子间的螯合作用受pH值影响,导致成核速度变化,进而影响NaNdF4纳米晶的最终尺寸和形貌。室温下的NaNdF4纳米棒的发光峰位于红外光范围(λ=892,1058,和1342nm),其最强发射峰位于1058nm,对应于Nd3+4F3/24I11/2f-f跃迁。  相似文献   
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