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91.
The electron states in Ge and Si under uniaxial stress in the (100) direction are computed with the pseudopotential method. The theoretical results are compared with optical measurements of the indirect absorption edge in Si and Ge under uniaxial stress and with the polarization dependence and the splittings of donor levels. 相似文献
92.
A PVC-based sensor for La3+ ions based on N-[hexahydrocyclopentapyrol-2((1H)yl)amino]carbonyl]-4-methyl benzene sulfonamide (gliclazide) as a novel carrier was prepared. The electrode exhibits a Nernstian response for La3+ over a wide concentration range (1.0×10−1-1.0×10−6 M) with a slope of 20.1 mV per decade. The limit of detection is 8.0×10−7 M. The sensor has a very short response time (<15 s) and a useful working pH range of 4.0-8.0. The proposed membrane sensor shows excellent discriminating ability towards La3+ ions with regard to several alkali, alkaline earth, transition and heavy metal ions. The electrode was successfully applied for determination of La3+ in binary mixtures. 相似文献
93.
The present work concerns the realisation of an equipment suitable for the choice of surfactants to be employed in the remediation of polluted soils by soil washing processes. The experimental activity has been focused to verify the surfactants efficiency in electrokinetic processes applied in low porosity soils, polluted with used vehicle oil. The equipment consents to estimate low electroosmotic permeabilities, electrical current and to analyse the electrolytic solutions. The concentration of the chemical species reached in both anodic and cathodic cells allows a more accurate evaluation of the ion mobility through the soil. The apparatus realised has been shown to be a useful instrument capable of providing directions for the choice of surfactants in electrokinetic soil remediation. The choice of an anionic surfactant for the oil removal has shown promising result. 相似文献
94.
Tahereh PoursaberiMorteza Hosseini Massoud TaghizadehHooshang Pirelahi Mojtaba ShamsipurMohammad Reza Ganjali 《Microchemical Journal》2002,72(1):77-83
A highly selective electrode for iodide ion based on a thiopyrilium derivative as an excellent ionophore is described. At pH 5.5-8.0, the electrode responds to iodide ion in a linear range from 1.0×10−1 to 8.0×10−7 M with a slope of 60.2 mV per decade, and a detection limit of 2.0×10−7 M. Selectivity coefficients determined with the match potential method (MPM) indicate that the interference from inorganic and organic anions is very small. The proposed sensor shows a fast response time of approximately 15 s. It was applied as an indicator electrode in titration of iodide with Ag+. 相似文献
95.
Afshin Rajabi Khorrami Tahereh Hashempur Ali Mahmoudi Ali Reza Karimi 《Microchemical Journal》2006,84(1-2):75-79
A highly sensitive and accurate method for preconcentration and determination of ultra trace amounts of cobalt and nickel ions in water samples is proposed. The preconcentration is achieved using C18-silica extraction disks modified with 5-(6-methoxy-2-benzothiazoleazo)-8-aminoquinoline (MBTAQ). The retained ions on the prepared solid phase was eluted with 10 ml of 0.01 M nitric acid and measured by inductively coupled plasma-optical emission spectrometry (ICP-OES). The influence of the type and amount of eluent used, pH, sample and eluent flow rates, amount of MBTAQ and the effect of other ions on extraction efficiency were investigated. The limits of detection of the method were 0.08 and 0.06 μg l− 1 for cobalt and nickel, respectively, and provide an enrichment factor of 100. The results obtained on 10 successive extractions and elution cycles revealed relative standard deviations of 1.5 and 1.0% for cobalt and nickel, respectively. The proposed method has been applied to the determination of ultra trace amounts of cobalt and nickel ions in natural and synthetic water samples with satisfactory results. 相似文献
96.
Marzieh Sadeghi Mohsen Irandoust Fatemeh Khorshidi Mostafa Feyzi Fataneh Jafari Tahereh Shojaeimehr Mojtaba Shamsipur 《Journal of the Iranian Chemical Society》2016,13(7):1175-1188
The application of newly synthesized Fe3O4/TiO2–SiO2 that is modified with zinc (FTSZ) as a sorbent, for the removal of arsenic from contaminated water has been investigated in the present study. SEM, FTIR, XRD, BET, Zeta potential sizer (ξ) analyses are used to determine the sorbent characterization. The effect of the operational parameters such as initial pH, initial concentration, and the contact time were studied. In addition, the equilibrium behavior of FTSZ in As(III) removal was investigated in the temperature range of 20–40 °C. The results showed that the equilibrium data were fitted well with Langmuir than Freundlich isotherm model. The maximum monolayer adsorption capacity estimated by Langmuir isotherm was 24.010 mg g?1. Thermodynamic parameters, ?H°, ?S° and ?G° were also calculated from graphical interpretation of the experimental data. Standard heats of sorption (?H°) were found to be endothermic and ?S° values were calculated to be positive for the sorption of As(III) onto the adsorbent. 相似文献
97.
N. N. B. Mohammad A. Arsad A. R. Rahmat N. S. Abdullah Sani M. E. Ali Mohsin 《Polymer Science Series A》2016,58(2):177-185
Polylactic acid (PLA) was toughened by 5–20 wt % of natural rubber (NR). Two different compatibilizers maleated PLA (PLA-g-MA) and maleated NR (NR-g-MA) were used as coupling agent. The blends were prepared using twin screw extruder at varying levels of NR. Mechanical, thermal and morphological analyses were carried out to study the effect of compatibilizer on PLA/NR blends compatibility. 相似文献
98.
采用共沉淀法制备了高比表面积的MnxCo3−xO4球形催化剂,研究了NH3选择性催化还原NOx性能。Mn-Co金属氧化物具有尖晶石结构,随着Co含量的增加,晶体结构由四方相转变为立方相。高浓度的表面活性氧物种和变价元素的强有效电子转移(Co3+ + Mn3+ ↔ Co2+ + Mn4+)有利于提高MnxCo3−xO4 (x = 1.0、1.5、2.0)尖晶型石催化剂的氧化还原能力,催化剂表面的Mn富集作用形成了氧缺陷结构和丰富的表面活性位点,进一步促进SCR脱硝反应,呈现出优异的催化性能。Cotet(CoMn)octO4晶体结构中,Mn离子(Mn3+和Mn4+,以三价锰为主)和部分Co离子被配置到八面体中心,这些物种作为活性位点存在着较强的电子转移交互作用,该构型对促进低温脱硝活性和保护活性位点耐受SO2毒害具有重要的意义。Mn-Co尖晶石表面的NH3-SCR脱硝反应过程主要遵循Eley-Rideal反应机理,即吸附态NH3与气态NO (或NO2)的反应路径。随着反应温度的增加,反应生成的NH4NO3中间体很可能转化为NH4NO2物种,进而分解为N2,提高了催化剂的氮气选择性。 相似文献
99.
Chassaing S Sani Souna Sido A Alix A Kumarraja M Pale P Sommer J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(22):6713-6721
For the first time, copper(I)-exchanged zeolites were developed as catalysts in organic synthesis. These solid materials proved to be versatile and efficient heterogeneous, ligand-free catalytic systems for the Huisgen [3+2] cycloaddition. These cheap and easy-to-prepare catalysts exhibited a wide scope and compatibility with functional groups. They are very simple to use, easy to remove (by filtration), and are recyclable (up to three times without loss of activity). Investigations with deuterated alkynes and deuterated zeolites proved that this Cu(I)-zeolite-catalyzed "click" reaction exhibited a mechanism different from that reported for the Meldal-Sharpless version. 相似文献
100.
Tahereh Hashempur Mohammad Kazem Rofouei Afshin Rajabi Khorrami 《Microchemical Journal》2008,89(2):131-136
A highly sensitive and accurate method for preconcentration and determination of ultra trace amounts of inorganic mercury and organomercury compounds in different water samples is proposed. The preconcentration is achieved using octadecyl silica (C18) extraction disks modified with 1,3-bis(2-cyanobenzene)triazene (CBT). The retained analytes as their triazenide complexes on the solid phase was eluted with 10 ml acetonitrile and measured by reversed-phase high-performance liquid chromatography (RP-HPLC). Type and amount of eluent, pH, amount of CBT, flow rates of sample solution and eluent have been optimized in order to obtain quantitative recovery of the analytes. The effect of interfering ions, such as Cu2+, Mn2+, Fe2+, Al3+, Zn2+, Cd2+, Ca2+, Mg2+, Ba2+, Pb2+, K+ and Na+ usually present in water samples on the recovery of the analytes has also been investigated. The enrichment factor of 100 was obtained for all mercury species and the analytical detection limits of phenylmercury, methylmercury and Hg2+ were found as 0.8, 1.0 and 1.3 ng l− 1, respectively. Stability of mercury species after extraction on the modified disks was studied and the results showed that complexes collected on the disks were stable for at least 5 days. The proposed method has been applied to the quantitative determination of mercury species in natural and synthetic water samples with recoveries more than 90%. 相似文献