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41.
42.
K. S. Viswanathan G. S. Dwarakanath V. V. Shanbhag 《Proceedings Mathematical Sciences》1971,74(3):115-132
The structure of strong shock waves in monatomic gases is studied using the Fokker-Planck model to represent the particle collisions and the Mott-Smith distribution to describe the distribution function within the shock front. The differential equation governing the variation of the density within the shock is derived by using the variational principle. The thickness of the shock front is evaluated numerically for various monatomic gases for Mach numbers varying from 2 to 20, and besides, the variation of the shock thickness with viscosity is also studied for different gases. Several parameters of physical interest within the shock, such as density, temperature and mean velocity of flow are evaluated numerically and detailed curves showing their variation within the shock are presented for different Mach numbers. It is found that the temperature rises very steeply, reaches a maximum within a distance less than half the thickness of the shock and then diminishes slowly to attain its asymptotic downstream values. The variation of the mean velocity is slow for weak shocks, but for higher Mach numbers, the mean velocity diminishes steeply and reaches the downstream values within half the thickness of the shock. 相似文献
43.
Hexagonal Se shows no indication of a transformation to a metallic, superconducting phase up to 160 kbar. Amorphous Se transforms at about 130 kbar to an unstable metallic, superconducting state which anneals slowly at room temperature toward a non-metallic, non-superconducting phase. Monoclinic Se behaves much like amorphous Se. X-ray diffraction indicates that all samples are in the hexagonal phase after release of pressure. 相似文献
44.
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46.
Sankar J Rath H PrabhuRaja V Chandrashekar TK Vittal JJ 《The Journal of organic chemistry》2004,69(15):5135-5138
Three new methods for syntheses of modified oxa corroles bearing one meso free carbon in reasonably good yields are reported. The formation of the meso carbon bridge and the direct pyrrole-pyrrole linkage occur in a single step by a simple condensation and coupling with TFA as a catalyst with appropriate precursors. The reactions are optimized with different conditions by varying the meso substituents, acid catalyst concentration, and the nature of the solvent to afford corroles in good yields. 相似文献
47.
Bimetallic Co–Ni/TiO<Subscript>2</Subscript> catalysts for selective hydrogenation of cinnamaldehyde
Saranya Ashokkumar Vivekanandan Ganesan Krishnamurthy K. Ramaswamy Viswanathan Balasubramanian 《Research on Chemical Intermediates》2018,44(11):6703-6720
Bimetallic Co–Ni catalysts in the composition range Co(1?x)Nix with x?=?0.0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8 and 1.0, with total metal loading of 15% w/w and supported on TiO2-P25, have been prepared by chemical reduction of the metal acetates by glucose in aqueous alkaline medium and characterized by XRD, TEM, TPR, XPS and H2-TPD techniques. Selective hydrogenation of cinnamaldhyde (CAL) to hydrocinnamaldehyde (HCAL), cinnamyl alcohol (COL) and hydrocinnamyl alcohol (HCOL) has been investigated at 20 bar pressure, in the temperature range 120–140 °C. Co/Ni crystallite sizes in the range 6.0?±?1 nm are observed by TEM. TPR and XPS results indicate the formation of nanoscale Co–Ni alloys, which tend to weaken M–H bond strength, as revealed by H2-TPD measurements. Ni/TiO2 displays very high conversion of CAL (86.9%) with high selectivity (78.7%) towards HCAL formation at 140 °C. Co/TiO2, on the other hand, exhibits relatively lower CAL conversion (55%) and higher selectivity (61.3%) for COL formation at the same temperature. However, bi-metallic Co–Ni catalysts in the composition range x?=?0.3–0.6 display very high conversion (>?98%) due to alloy formation and weakening of M–H bonds. Bimetallic Co0.7Ni0.3 catalyst displays high conversion of CAL (98.1%) and high selectivity (82.9%) towards HCOL. Overall CAL hydrogenation activity at 140 °C, when expressed as TOF, displays a maximum value at the composition Co0.5Ni0.5. Activity and selectivity patterns have been rationalized based on the reaction pathways observed on the catalysts and the influence of Co–Ni alloy formation and M–H bond strength. Thus, a synergetic effect, originating from an appropriate composition of base metal catalysts and reaction conditions, could result in hydrogenation activity comparable with noble metal based catalysts. 相似文献
48.
Venkatraman S Anand VG PrabhuRaja V Rath H Sankar J Chandrashekar TK Teng W Senge KR 《Chemical communications (Cambridge, England)》2002,(16):1660-1661
First successful syntheses and structural characterization of new core modified meso aryl azuliporphyrins by a simple [3 + 1] methodology are reported. 相似文献
49.
Paramasivam Manisankar Subramanian Viswanathan Halliah Gurumallesh Prabu 《International journal of environmental analytical chemistry》2013,93(5):389-397
Electrochemical studies of direct orange 8 were carried out with a bare glassy carbon electrode (GCE) and a polypyrrole-coated GCE in aqueous acetonitrile medium using voltammetric techniques. One reversible couple around 0.3?V due to the redox reaction of the phenol group, one reduction peak around ?0.4?V due to reduction of the azo group and one oxidation peak around 1.0?V due to oxidation of the amino group were observed. Chronocoulometric studies revealed dye adsorption on the GCE. A square-wave stripping method was developed for the determination of the dye at pH 13.0, and a linear calibration equation obtained. The reproducibility in the measurement of peak currents was confirmed from the RSD value 2.8% at 0.001?mg?mL?1 concentration. A comparison of the stripping voltammetric method with the UV-Vis spectrophotometric method was made. The determination limits are wider and the RSD value is lower in the stripping voltammetric method. The concentration of the dye present in dye effluent was determined using this method. 相似文献
50.
Silija Padikkaparambil Zahira Yaakob Binitha N. Narayanan Resmi Ramakrishnan Suraja Viswanathan 《Journal of Sol-Gel Science and Technology》2012,63(1):108-115
In the present study, a novel method for the silver nanoparticle incorporation into TiO2 sol is reported which provides efficient dispersion of inserted metal in the calcined gel. Glucose mediated metal nanoparticle synthesis eliminates the additional steps for the introduction of dopant over the support. Ag nanoparticle acts as competent trapping centers preventing the recombination of electron?Chole pairs. Thus, in spite of the low UV intensity present in the sunlight, considerable enhancement in the catalytic efficiency was observed for the degradation of dye pollutants over nanosilver loaded TiO2. Transmission electron microscopic images display the well isolated nanoparticles of silver having uniform dimensions of less than 5?nm over the best system, 2?wt% nanosilver loaded TiO2, which is accountable for its effectiveness as a photocatalyst. Anatase is found to be the photocatalytic active phase, as evident from the X-ray diffraction studies. 相似文献