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141.
Abstract Raman phonon spectra of 9, 10-dinitroanthracene have been recorded in the pressure range 0-6GPa. No phase transition is detected up to the maximum pressure studied. Quasi Harmonic Lattice Dynamics calculations, based on an atom-atom potential previously modeled on homologous 9,10-disubstituted anthracenes, have been performed. The optimized potential was used to calculate the equilibrium geometry and the lattice phonon frequencies as a function of pressure. The calculated structure at ambient conditions closely resembles the experimental one. The calculated phonon frequencies show a good agreement with the experimental values at all pressures measured. 相似文献
142.
Several experimental techniques are used to study the short range order, the dynamics and the glass transition in AgIAg2B2O3 compounds. Addition of Ag2O to B2O3, up to [Ag2O]/[B2O3] ?0.5 modifies the borate network by creating a BO4 unit for each silver added. Addition of AgI decreases the glass transition temperature (Tg) but has only minor effects on the short range structure of the borate network. Silver iodide is partially accomodated in the interstices of the glass network. The relationship among a tentative structural picture, the ion transport phenomena and the low temperature dynamics are discussed.An investigation of the dynamics in the AgI·Ag2O·2B2O3 glass near and above Tg is presented. With NMR techniques, we monitor the onset of tumbling of the borate units and the dynamical effects of crystallization and/or aging of the glass. Hysteresis effects in the ionic conductivity (σ) temperature dependence and the non-Arrhenian behavior of σT near Tg are interpreted in terms of structural modifications occurring at elevated temperatures in the glass. 相似文献
143.
Bizzarri M Cavaliere C Foglia P Guarino C Samperi R Laganà A 《Analytical and bioanalytical chemistry》2008,391(5):1969-1976
A label-free absolute quantitation method based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry
(MALDI-TOF MS) has been developed. This methodology was applied to mouse heart in order to quantify cardiac troponin T (cTnT),
which is considered to be a sensitive marker of heart damage. The cTnT was extracted, isolated by reversed-phase high-performance
liquid chromatography, digested, and analyzed by MALDI-TOF MS. The MS-based quantitation was performed using matrix-matched
calibration curves (due to a matrix effect) of two synthetic peptides, one cTnT-specific peptide and one internal standard
peptide, respectively. Recoveries at three spiking levels ranged from 87–96%, with relative standard deviations of below 10%.
The method detection limit and the method quantitation limit, expressed as the amount of cTnT for the amount of total sarcomeric
protein extract, were 0.03 mg g−1 and 0.15 mg g−1, respectively. This method appears to be accurate and generally suitable for improving absolute protein quantitation. 相似文献
144.
Maria R. di Nunzio Dr. Pier L. Gentili Dr. Aldo Romani Dr. Gianna Favaro Prof. 《Chemphyschem》2008,9(5):768-775
The photochromic and thermochromic behavior of four commercially available Reversacol dyes are presented. The compounds studied belong to the class of spirooxazines and naphthopyrans, which are typically thermoreversible photochromic molecules. On stimulation with UV light, these compounds become colored and exhibit spectra which extend over the whole visible region. Increasing the temperature causes spontaneous coloration (thermochromism). Herein, absorption and fluorescence spectra, molar absorption coefficients of the colorless and colored forms, fluorescence and photochemical quantum yields, and kinetic parameters of thermal bleaching (rate constant, frequency factor, and activation energy) are determined in acetonitrile solution. The thermal ground‐state reaction is exhaustively described in terms of thermodynamic parameters (equilibrium constant, free energy, enthalpy, and entropy). Temperature effects on photochemical and thermal colorabilities are evaluated. The results indicate that the two spirooxazines are good photochromes below room temperature, whereas they are efficient thermochromic compounds above room temperature. Naphthopyrans are better photochromes but worse thermochromic compounds than spirooxazines. 相似文献
145.
Giovanni Felici Sokol Ndreca Aldo Procacci Benedetto Scoppola 《Annals of Operations Research》2016,243(1-2):229-243
A matrix M∈Rn×n is said to be a column sufficient matrix if the solution set of LCP(M,q) is convex for every q∈Rn. In a recent article, Qin et al. (Optim. Lett. 3:265–276, 2009) studied the concept of column sufficiency property in Euclidean Jordan algebras. In this paper, we make a further study of this concept and prove numerous results relating column sufficiency with the Z and Lypaunov-like properties. We also study this property for some special linear transformations. 相似文献
146.
Favaro G di Nunzio MR Gentili PL Romani A Becker RS 《The journal of physical chemistry. A》2007,111(27):5948-5953
The widely investigated photobehaviors of 9-bromo and 9,10-di-bromoanthracenes have been revisited here to clarify the competition among different relaxation paths of their lowest two electronic excited states. The results obtained show that these two molecules exhibit a parallel photobehavior, which depends on the excited electronic and vibronic transition, the medium viscosity, and the temperature. The first electronic state of either of these does not exhibit photochemistry in fluid solution or rigid matrices (80 K). The fluorescence emission occurs with a very low quantum yield (approximately 10(-2)) at room temperature but with a very high quantum yield (0.9 to approximately 1) at 80 K. When exciting in the second electronic transition, the fluorescence intensity is lower than when exciting in S1 at both room temperature and low temperature due to competition with the observed photocleavage of the C-Br bond. The reaction yield decreases as the temperature decreases and depends on the viscosity of the solvent; the higher the viscosity, the lower the observed yield of photochemistry. Temperature and viscosity effects are a consequence of the fact that the radicals produced by C-Br bond breakage cannot escape from the solvent cage and, moreover, quickly recombine within the cage giving the appearance that no photochemistry occurred. The presence of photochemistry in S(2) and its absence in S(1) is principally due to the fact that S(2) has a pi,sigma* character in the C-Br bond, whereas the S(1) state has its origin from a pi,pi* delocalized configuration. 相似文献
147.
A systematic computational investigation on protonated and nonprotonated boron-containing zeolites (boralites), performed by using different periodic density functional theory approximations, is presented. Both minimum energy structures and finite temperature behavior of model boron sodalites were analyzed. All of the adopted computational schemes agree in predicting an acid site composed of a silanol Si-OH group loosely linked to a planar BO(3) structure in the protonated system and a BO(4) tetrahedral site in the sodium-containing zeolite. Calculated structural and vibrational properties are in line with experimental data. Comparisons of the protonated boralite site with Al and Ga zeolitic acid sites are discussed as well. Results indicate that this class of mild acid catalysts is characterized by significant framework flexibility and pronounced thermal effects due to the loosely bound acid site. 相似文献
148.
Nanni P Parisi D Roda G Casale M Belluzzi A Roda E Mayer L Roda A 《Rapid communications in mass spectrometry : RCM》2007,21(24):4142-4148
The identification of new biomarkers or a disease-related protein fingerprint for inflammatory bowel diseases (IBDs) represents a major task in the diagnosis, prognosis and pharmacological therapy. To address these issues, a simple and rapid analytical proteomic method for serum protein profiling based on selective beads-based solid-phase bulk extraction, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and chemometric data analysis was developed. Serum proteins from healthy subjects (22) and patients with Crohn's disease (15) and ulcerative colitis (26) were selectively extracted according to reversed-phase (C18), strong anion-exchange (SAX) and metal ion affinity (IDA-Cu(II)) principles. This approach allowed enrichment of serum proteins/peptides due to the high interaction surface between analytes and the solid phase and high recovery due to the elution step performed directly on the MALDI-target plate. The MALDI-TOF MS serum protein profiles were acquired and, after a data pre-processing step, analyzed by linear discriminant analysis (LDA), a chemometric classification technique, in order to classify serum samples among healthy subjects and patients with inflammatory bowel diseases (IBDs). Since the high number of variables in the MALDI spectra (more than 16000 m/z values) prevents the use of LDA, the variables were reduced to 10-20 by features selection, thus allowing the evaluation of a pattern of m/z values with high discriminant power. Serum protein profiles obtained by reversed-phase extraction and the selection of 20 m/z values gave the best overall prediction ability (96.9%). The recognition of these m/z values may allow the identification of protein biomarkers involved in IBDs. 相似文献
149.
Abstract Consider an interstellar cloud that occupies the region
, bounded by the known surface
, and assume that the scattering cross section σs and the total cross section σ are also known. Then, we prove that it is possible to identify the source q=q(x,t) that produces UV-photons inside the cloud, provided that the UV-photon distribution function arriving at a location
, far from the cloud, is measured at times
,
, ...,
.
Keywords: Photon transport, Semigroups and linear evolution equations, Inverse problems
Mathematics Subject Classification (2000): 82A25, 82C70, 34K29, 65M32 相似文献
150.