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61.
土壤中养分元素作为植物生命物质的来源具有重要作用。四川乌蒙山区土地质量地球化学调查评价显示,麻城乡、摩尼镇以较一等和二等土地为主。表层土壤中有效铁、铜、锌、硫的含量丰富和很丰富占比超过80%,有效钼和锰的含量丰富和很丰富占比超过50%。部分地区磷、有机质、氧化钙、硼较为缺乏,需要根据区域元素缺乏种类,分布范围,有针对性地补施相应的肥料。  相似文献   
62.
Visual aspect and aroma are among the most important features of fruit that determine consumer preferences. Electronic nose and spectroscopic techniques have shown positive results in evaluating some basic analytical parameters of fruit and global features such as the cultivar.In this paper, we illustrate and discuss a study aimed at evaluating the improvement derived by the fusion of visible spectra and electronic nose data. These experiments were performed on a population of yellow peaches belonging to two cultivars. Each sample was measured by visible optical spectroscopy and by electronic nose. In addition, a number of reference parameters were also measured by conventional destructive methodologies.Collected data were analysed individually and then fused together in order to classify the two cultivars and to estimate the reference parameters. Data fusion was performed building the outer product matrix for each measurement. The set of matrices was then successively unfolded and analysed by conventional chemometrics tools.Results were improved using outer products, for instance in classification average percentage errors of 25, 10, and 7 for electronic nose, spectra, and outer product, respectively was achieved. Regression analysis provides the evidence of a substantial orthogonal appearance of the datasets, which offer former hidden information on fruit classification.  相似文献   
63.
In this paper, the effects of grain orientation on preferred abnormal grain growth in HCP-polycrystalline thin films have been analysed with respect to strain energy. The calculated results showed that Chkl, the average values of the orientation factor, decreased with increase of 1 for the same h and k and increased with increase of h or/and k for constant 1. Where (hkl) denoted a particular grain orientation, that is, the grains with (hkl) planes oriented parallel to the film surface. This is preannounced that, considering the strain energy solely, the grains with higher 1 and lower h and k should be favorable in HCP-polycrystalline thin films on rigid substrates after annealing.  相似文献   
64.
研究了XMg O·YMg(OH)2对水中氟离子的吸附性能,考察了吸附时间、吸附剂用量、含氟水p H值、温度、含氟水初始浓度等因素对吸附的影响。实验结果表明,在较宽的p H(3.4~8.4)值和水温(22~51℃)范围内,XMg O·YMg(OH)2对水中氟离子具有极强的吸附能力,室温下0.4g XMg O·YMg(OH)2可将100m L浓度为30mg F-1·L-1含氟水处理为符合含氟标准的饮用水。氟离子在XMg O·YMg(OH)2上的吸附速率较大,30min内基本达到吸附平衡,吸附平衡符合Langmuir方程,在50min内达到饱和吸附,室温下饱和吸附量为13.46mg·g-1。净化水呈微碱性,含有5.68~15.07mg·L-1Mg2+,有益于人体健康。吸附饱和后的XMg O·YMg(OH)2经焙烧再生,除氟率可达81%。  相似文献   
65.
    
Low angle grain boundaries, also referred to as domain walls, is one of the major structural defects in c‐axis physical vapor transport (PVT) grown hexagonal Silicon Carbide. To investigate the nature of the low angle boundaries, polarized optical microscope was used. The low angle boundary gives bright stress birefringence images under polarizing optical microscope. Periodic extinction of the stress birefringence images occurs when the (0001)‐face SiC is rotated under polarizing optical microscope. The micro‐structure of the low angle boundary is proposed. Using dislocation elastic theory, it is theoretically confirmed that the domains consist of uniform pure edge dislocations with Burgers vectors perpendicular to the dislocation arrays. The simulation results coincide with the experimental observations.  相似文献   
66.
    
A multi‐scale model is used to simulate columnar dendritic growth in TIG (tungsten inert‐gas) weld molten pool of Al‐Cu alloy. The grain morphologies at the edge of the weld pool are studied. The simulated results indicate that the average primary dendrite spacing changes during the solidification process in the weld pool because of the complicated thermal field, solute diffusion field and competitive growth. And it is shown that the secondary dendrite arms grow insufficiently in the space between dendrite trunks if the primary dendrite spacing is small. And the phenomenon has been explained by analyzing the influence of the solute accumulation on the constitutional undercooling and undercooling gradient when there are two different opposite solute diffusion fields. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
67.
    
In the present work, investigations on the microstructure of a commercial purity 1100 aluminum that had been subjected to moderate to strong deformation (strains of 1 to 4) by equal channel angular pressing (ECAP) were carried out using X‐ray diffraction (XRD) and scanning electron microcopy (SEM). A significant grain refinement and development of heterogeneous microstructure after ECAP were observed. High precision XRD and SEM investigations provided useful results on the dissolution of coherent iron rich precipitates, previously formed in the aluminium matrix, by ECAP deformation process. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
68.
    
The magnetic and transport properties of polycrystalline YBa2 (Cu1‐xMx)3 O7‐δ (M = B and Mn) superconductor was investigated. Samples of YBa2(Cu1‐xBx)3O7‐δ doped with several concentrations of boron B(x = 0.05 and 0.1) were investigated using magnetization measurements. A YBa2(Cu1‐xMnx)3O7‐δ sample doped with Mn with concentration of x = 0.02 was investigated using current‐voltage (I‐V) measurements. Our results on the YBa2(Cu1‐xBx)3O7‐δ samples reveal a considerable increase in the hysterisis width of the magnetization, M versus the applied magnetic field H with increasing boron concentration. The lower critical field was also found to be enhanced by boron doping. The critical current density, Jc was found to be significantly enhanced in the Mn‐doped sample. The enhancement of Jc was found to be more significant at the lower temperatures for all applied magnetic fields used (0 Oe, 300 Oe, and 500 Oe). Thus, chemical doping is suggested to enhance the vortex pinning forces in the YBCO samples. From the resistivity (R‐T) measurements, chemical doping of the samples was found to have no significant effect on the critical temperature, Tc. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
69.
    
Progress in experimental methods of serial sectioning and orientation determination opens new opportunities to study inter‐crystalline boundaries in polycrystalline materials. In particular, macroscopic boundary parameters can now be measured automatically. With sufficiently large data sets, statistical analysis of interfaces between crystals is possible. The most basic and interesting issue is to find out the probability of occurrence of various boundaries in a given material. In order to define a boundary density function, a model of uniformity is needed. A number of such models can be conceived. It is proposed to use those derived from an assumed metric structure of the interface manifold. Some basic metrics on the manifold are explicitly given, and a number of notions and constructs needed for a strict definition of the boundary density function are considered. In particular, the crucial issue of the impact of symmetries is examined. The treatments of homo‐ and hetero‐phase boundaries differ in some respects, and approaches applicable to each of these two cases are described. In order to make the abstract matter of the paper more accessible, a concrete boundary parameterization is used and some examples are given.  相似文献   
70.
    
By orienting a crystal grain with its diffraction vector along the sample rotation axis, it is possible to use powerful tomographic and topographic imaging techniques to reconstruct the three‐dimensional grain shape inside a polycrystalline sample. The acquisition and reconstruction can be performed from projection images with the detector positioned either in the diffracted‐beam or in the direct‐beam position. In the first case, the projection data consist of a series of integrated, monochromatic beam X‐ray diffraction topographs of the grain under investigation. In the second case, the corresponding diffraction contrast in the transmitted beam may be interpreted as an additional contribution to the X‐ray attenuation coefficient of the material. This latter variant is restricted to grains with small orientation spread but offers the possibility to characterize simultaneously the three‐dimensional grain shape and the absorption microstructure of the surrounding sample material. The contrast mechanism is sensitive to local strain fields and can, in certain cases, reveal details of the grain microstructure, such as the presence of second‐phase inclusions. The methodology is successfully demonstrated on an aluminium polycrystal, with a resulting three‐dimensional mapping accuracy better than 7 µm. The possibilities and limitations of the technique are listed and its performance relative to other three‐dimensional mapping techniques is discussed.  相似文献   
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