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991.
M. N. Tripathi C. M. Bhandari 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(4):503-508
Tailoring thermoelectric materials for specific designs and applications has
been gaining momentum during past three decades. Initially confined to
conventional (bulk) framework an entirely new scenario emerged with
inclusion of low-dimensional structures in the scheme of things. The paper
examines the effect of size reduction on phonon and electron properties in
two-dimensional (quantum well) structures with an aim to maximize
thermoelectric performance. The formulation has been applied to
silicon-germanium quantum wells with well width ranging from 50–500 ?
aimed at finding best alloy combination for thermoelectric applications. 相似文献
992.
Calibo glasses of Sm3+ with and without BaO have been synthesized and the optical properties (like absorption and photoluminescence) analyzed in terms of Judd–Ofelt theory. The fluorescence yield of Sm3+ enhances with BaO, and is optimum at 10% BaO. The effect of temperature on the energy transfer probability in (Sm3+:Eu3+) codoped glass has been reported and it can be inferred that the combination may serve as a temperature sensor. PACS 42.70.Ce 相似文献
993.
Harsh Kumar Meenu Singla Rajeev Jindal 《Monatshefte für Chemie / Chemical Monthly》2014,145(4):565-575
994.
Aditi Chakrabarty S. Mohapatra R. M. Tripathi V. D. Puranik H. S. Kushwaha 《Accreditation and quality assurance》2010,15(2):119-123
Quality assurance and quality control are necessary to ascertain the output of any instrument with a certain level of confidence
and maintain the measurement process in a state of statistical control. Data generated by three laser fluorimeters, used for
analysing mass concentration of total uranium in liquid samples, were used in the present study. Erroneous data values, called
outliers, were detected by Dixon test, Discordance outlier test, Rosner outlier test and Box plot. The distribution fitted
to the data, was tested by Kolmogorov–Smirnov test, Chi-square test and Shapiro–Wilks test. From Shewart Control Charts it
was concluded that the instruments were not in statistical control and an instrumental problem existed. The instrumental problem
was solved and the instruments were subjected to quality control exercise again. Statistical parameters of the data from the
detectors were compared before and after servicing. The improvement of the quality of detector output was evident. 相似文献
995.
Liquid crystal elastomers exhibit several interesting phenomena like elastic response, shape memory effect and mechanical actuation triggered by external stimuli and have got much importance among all types of actuated materials. In the present study, we synthesised nematic liquid crystal elastomers (NLCEs) by using Finkelmann procedure. The chemical structure of elastomers is confirmed by Fourier transform infrared spectroscopy. The dielectric response of NLCEs and the monomer used in its synthesis has been studied in the frequency range 20 Hz to 1 MHz. The effect of bias on dielectric response of NLCE and its comparison with its liquid crystal analogue is also reported. 相似文献
996.
In this paper, we study the boundedness and the compactness of composition operators on Orlicz–Lorentz spaces.
相似文献
997.
Hashim Farooq Denis Courtier‐Murias Ronald Soong Hussain Masoom Werner Maas Michael Fey Rajeev Kumar Martine Monette Henry Stronks Myrna J. Simpson André J. Simpson 《Magnetic resonance in chemistry : MRC》2013,51(3):129-135
A method is presented that combines Carr–Purcell–Meiboom–Gill (CPMG) during acquisition with either selective or nonselective excitation to produce a considerable intensity enhancement and a simultaneous loss in chemical shift information. A range of parameters can theoretically be optimized very rapidly on the basis of the signal from the entire sample (hard excitation) or spectral subregion (soft excitation) and should prove useful for biological, environmental, and polymer samples that often exhibit highly dispersed and broad spectral profiles. To demonstrate the concept, we focus on the application of our method to T1 determination, specifically for the slowest relaxing components in a sample, which ultimately determines the optimal recycle delay in quantitative NMR. The traditional inversion recovery (IR) pulse program is combined with a CPMG sequence during acquisition. The slowest relaxing components are selected with a shaped pulse, and then, low‐power CPMG echoes are applied during acquisition with intervals shorter than chemical shift evolution (RCPMG) thus producing a single peak with an SNR commensurate with the sum of the signal integrals in the selected region. A traditional 13C IR experiment is compared with the selective 13C IR‐RCPMG sequence and yields the same T1 values for samples of lysozyme and riverine dissolved organic matter within error. For lysozyme, the RCPMG approach is ~70 times faster, and in the case of dissolved organic matter is over 600 times faster. This approach can be adapted for the optimization of a host of parameters where chemical shift information is not necessary, such as cross‐polarization/mixing times and pulse lengths. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
998.
We show that for organic semiconductors, it is sufficient to have a doped/undoped homojunction to obtain a near ideal diode with exponential dependence of current density (J) on voltage (V), though the physics is very different from the ideal Shockley equations for conventional p–n junction. Unlike Shockley diodes, the slope of the semi-log plot in this regime is independent of temperature, and is related to the broadening parameters of Gaussian density of states (DOS). We show that physics of transport in the regime is controlled by alignment through local DOS and tunneling across the interface. The mechanism sets in beyond a newly identified threshold voltage (Vth) which decreases linearly with temperature and corresponds to offset in energy of localized DOS at the interface at which overlap begins to occur. The temperature dependence of all other significant features is shown to be consistent with localized Gaussian density of states model of disordered solids. 相似文献
999.
Graft copolymerization of ethylmethacrylate (EMA) onto soy protein concentrate (SPC) was carried-out using ascorbic acid/potassium persulphate as redox initiator under microwave radiations. Different reaction parameters like reaction time, solvent amount, initiator ratio, pH and monomer concentration were optimized to get maximum graft yield (78.8%). The graft copolymer formed was characterized by FTIR, XRD, SEM, TGA, DTA and DTG techniques. Graft copolymer showed higher moisture resistance along with increased chemical and thermal stability. TGA, DTA and DTG studies could reveal the distinctive features of graft copolymerization of EMA onto S-S linkages of soy protein concentrate under the influence of microwave irradiations in addition to grafting at peptide linkages, which were further supported by FT-IR studies. 相似文献
1000.
U. N. Tripathi A. Siddiqui Mohd. Safi Nitya Sharma Neetu Srivastava 《Phosphorus, sulfur, and silicon and the related elements》2013,188(9):1993-2001
Dichlorotitanium(IV) trithiophosphates of the type TiCl2[(RO)P(S)S2] (where R = Me, Et, Prn, Pri, Bun, Bus, Bui, Ami, Ph and cyclohexyl) have been synthesized for the first time by the reaction of titanium tetrachloride with potassium trithiophosphates in a 1:1 molar ratio in anhydrous benzene. Sol-gel chemistry of these titanium(IV) compounds has been studied in dry benzene by treatment with hydrogen sulfide gas. These newly synthesized derivatives have been characterized by elemental analysis (C, H, S, Cl, and Ti), molecular weight measurement, and spectral [IR and multinuclear NMR (1H, 13C, and 31P)] studies. The bonding mode of trithiophosphate ligands and tentative structure around titanium(IV) are discussed. 相似文献