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101.
Vapour–liquid equilibria and densities for the ternary system chloroform + tetrahydrofuran + cyclohexane and for the binary mixtures containing chloroform have been determined at 298.15 K. Vapour–liquid equilibrium data have been collected by head-space gas-chromatographic analysis of the vapour phase directly withdrawn from an equilibration apparatus. Density measurements have been carried out by means of a vibrating tube densimeter. Molar excess Gibbs energies GE and volumes VE, as well as activity coefficients and apparent molar volumes of the components, have been obtained from the measured quantities and discussed. The binary chloroform + tetrahydrofuran displays negative deviations from ideality, while chloroform + cyclohexane positive deviations, for both volume and Gibbs energy. The GE's and VE's for the ternary system are positive in the region rich in cyclohexane while negative in the region rich in chloroform + tetrahydrofuran. This indicates that hydrogen bonding between chloroform and tetrahydrofuran molecules produces negative values of GE and VE and strongly influences the behaviour of the ternary system. 相似文献
102.
Roman Gumeniuk Dr. Miriam Schmitt Walter Schnelle Ulrich Burkhardt Helge Rosner Andreas Leithe‐Jasper 《无机化学与普通化学杂志》2010,636(6):954-961
Two new intermetallic alkaline‐earth palladium borides, SrPd4B and BaPd4B were synthesised and their physical properties were investigated. The crystal structure of SrPd4B was solved from powder X‐ray diffraction data: new structure type, space group Pnma, a = 6.0014(1) Å, b = 5.5041(1) Å, c = 11.8723(2) Å, RI = 0.065, RP = 0.093. BaPd4B is isostructural with a = 6.0883(1) Å, b = 5.6066(1) Å, c = 12.0050(2) Å, RI = 0.062, RP = 0.097. The relationship of this structure type with the series of derivatives of the CaCu5 type is discussed. Calculated electronic band structures for palladium, Pd3B, SrPd5, SrPd4B and SrPd3B are compared. The role of boron and strontium for the electronic properties is discussed in detail. SrPd4B shows metallic behaviour with a DOS(EF) ≈? 1.7 eV–1 · f.u.–1 at the Fermi level. Magnetic properties, electrical resistivity and specific heat capacity measurements reveal that the two compounds are diamagnetic metallic conductors with low electronic density of states, in agreement, with the electronic structure calculations. 相似文献
103.
Physical properties of NdPd2Ge2 and NdAg2Ge2, crystallizing with the tetragonal ThCr2Si2-type crystal structure, were investigated by means of magnetic, calorimetric, electrical transport as well as by neutron diffraction measurements. The specific heat studies and neutron diffraction measurements were performed down to 0.30 K and 0.47 K, respectively. Both compounds exhibit antiferromagnetic ordering below TN equal to 1.5 K for NdPd2Ge2 and 1.8 K for NdAg2Ge2. Neutron diffraction data for the latter germanide indicate antiferromagnetic collinear structure described by the propagation vector k=(0.5, 0, 0.5). The Nd magnetic moments equal to 2.24(5) μB at 0.47 K are aligned along the a-axis and have the +− sequence within the crystal unit cell. For NdPd2Ge2 only very small Bragg peaks of magnetic origin were observed in the neutron diffraction patterns measured below TN, thus hampering determination of the magnetic structure. Both compounds exhibit metallic-like electrical conduction. From the specific heat data the crystal electric field (CEF) levels schemes were determined. Difference between the overall CEF splitting in the two compounds is correlated with their structural parameters. 相似文献
104.
The crystal structure of the Zr1−xYxNiSn half-Heusler solid solutions is synthesized and their crystal structure is determined. Electrical resistivity and thermoelectric Seebeck coefficient are measured in the 80-380 K temperature range, whereas magnetic susceptibility is measured at 290 K. It is established that substitution of Zr host atoms by Y in the ZrNiSn intermetallic semiconductor is equivalent to doping by acceptor impurities. Self-consistent ab initio calculations, based on the full potential local orbital (FPLO) minimum basis method, are performed to investigate the electronic and thermoelectric properties of these alloys. Spin polarized within the framework of the coherent potential approximation (CPA) are included. 相似文献
105.
基于并行电法的重阳木根系空间分布探测试验研究 总被引:1,自引:0,他引:1
《科学技术与工程》2017,17(10)
探测树木根系的空间分布,对了解树木的生长及移栽等具有重要的作用。利用并行电法技术进行树木根系三维空间分布特征探测试验,通过在重阳木周边7.5 m×9.5 m范围内布置观测系统进行数据采集,对采集到的数据进行多测线联合反演得到三维电阻率图像。结果表明:探测范围内的根系分布呈现出南测密集,北侧稀少的特征;探测区域根系根径范围主要分布在200~300 mm;深度为0.46 m位置处根系量最大且根系生物量最多;重阳木根系下方土壤中含水充足,结果图呈现了根系与地下环境间的相互关系。该成果在研究树木根系空间分布范围及特征方面具有良好的应用前景。 相似文献
106.
相山铀矿田为我国主要铀矿资源基地之一。对相山火山盆地主要地质单元的密度、磁化率、电阻率、极化率与波速物性进行了测试分析,测试样本覆盖地质单元包括鹅湖岭组一段、鹅湖岭组二段、沙洲单元、打鼓顶组一段、打鼓顶组二段、青白口系等。对测试数据采用3倍均方差法剔除异常值后进行数据统计,得到了常见值、平均值、变化范围等参数,结果表明变质岩与火山岩之间存在良好的物性界面,为深部找矿物探方法的开展提供了物性基础。通过逆质量磁化率(密度/磁化率)与密度交会分析,可较为明显的将物性交会区域划分为四个区,分别对应4类填图单元。该研究全面认识了相山火山盆地主要地质体的物性特征,对在该区开展重磁联合反演提供了新的思路,对该区深部探矿很有意义。 相似文献
107.
Airflow resistivity is a physical parameter which characterizes porous and fibrous sound absorbent materials. It is well-known that such property allows the evaluation of the acoustic behaviour of sound absorbent materials in various fields of application, including automotive noise mitigation, architectural acoustics and building acoustics. In structure-borne sound insulation, airflow resistivity is essential for the evaluation of the dynamic stiffness of porous and fibrous resilient insulating materials used as underlay in floating floors.However, an inconsistency between the dynamic stiffness and the airflow resistivity test conditions can be recognized. In order to evaluate dynamic stiffness of a resilient material, a static load of about 2 kPa is applied, while in airflow resistivity determination this condition is not explicitly required. As a result, the density of analyzed material, in dynamic stiffness and airflow measurements, is different. Since these two quantities are correlated, it is necessary to measure materials under the same conditions of applied static load.In this work the effects of static load (or density after compression) in airflow resistivity determination of various porous and fibrous resilient materials are investigated, and the consequent influence on dynamic stiffness is discussed. A simply empirical relation between density and airflow resistivity is also put forth.The main focus of this paper is to propose an harmonization among requirements of the Standards in order to prevent significant errors in dynamic stiffness determination and incorrect evaluations of the acoustic behaviour. 相似文献
108.
Javed Ahmad Muhammad Ehsan MazharMuhammad Qadeer Awan Muhammad Naeem Ashiq 《Physica B: Condensed Matter》2011,406(18):3484-3488
Potassium substituted nanosized magnesium aluminates having a nominal composition Mg1−xKxAl2O4 where x=0.0, 0.25, 0.5, 0.75, 1.0 have been synthesized by the chemical co-precipitation method. The samples have been characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), and dc electrical resistivity measurements. The XRD results reveal that the samples are spinel single phase cubic close packed crystalline materials. The calculated crystallite size ranges between 6 and 8 nm. The behaviour of the lattice constant seems to deviate from the Vegard's law. While X-ray density clearly increases, the bulk density and consequently, the percentage porosity do not exhibit a significant change on increasing the K+ content. The SEM micrographs suggest homogeneous distribution of the nanocrystallites in the samples. The dc electrical resistivity exhibits a typical semiconducting behaviour. Substitution of a Mg2+ ion by a K+ ion provides an extra hole to the system, which forms small polaron. Thermally activated hopping of these small polarons is believed to be the conduction mechanism in the Mg1−xKxAl2O4. The activation energy of hopping of small polarons has been calculated and found K+ ions content dependent. 相似文献
109.
Densities and viscosities of glycine and l-valine have been measured at 308.15 and 318.15 K in aqueous tripotassium citrate solutions ranging from 0.2 to 0.8 mol kg− 1 of tripotassium citrate. The viscosity data have been analyzed by Jones-Dole equation. The activation parameters of viscous flow have been obtained to throw light on the mechanism of viscous flow. The values of apparent molar volume, partial molar volume at infinite dilution and relative viscosities of each amino acid in various aqueous tripotassium citrate solutions have been evaluated from the density and viscosity data. The partial molar volumes of transfer from water to aqueous tripotassium citrate solution at infinite dilution have also been calculated. Transfer volume data have been used to calculate the pair and triplet interactions. The results have been discussed in terms of solute-solute and solute-solvent interactions and the structural changes of the solutes in solutions. 相似文献
110.
Takeshi Yoshizako Akihiko WadaKoji Uchida Shinji HaraMikio Igawa Hajime KitagakiStephan E. Maier 《Magnetic resonance imaging》2011,29(1):106-110