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621.
Bathini Madhusree S. Tanabe Ayaka Amaha ?ztürk Ryo Tatsukawa Nobuyuki Miyazaki Emin ?zdamar Orhan Aral Osman Samsun Bayram ?ztürk 《Fresenius' Journal of Analytical Chemistry》1997,359(3):244-248
Concentrations of butyltin compounds (BTs) were determined in harbour porpoise (Phocoena phocoena) collected from the Turkish coastal waters of the Black Sea. Total butyltin compounds (∑ BTs) in the liver were in the range
of 89–219 ng/g on a wet weight basis. The dibutyltin (DBT) residues were higher than those of tributyltin (TBT), suggesting
the degradation of TBT to DBT in the liver and the metabolic capacity comparable to other marine mammals. Any sex difference
and age-dependent accumulation of BTs residues were not found in harbour porpoises, but residue levels increased until maturity
and then remained constant. When compared with other marine mammals, the present results indicate that the Black Sea is also
contaminated with butyltin compounds, but to a lesser degree than coastal waters of developed nations. The biomagnification
factor in harbour porpoises was 0.8, which was comparable with pinnipeds and lower than cetaceans.
Received: 23 December 1996 / Revised: 15 April 1997 / Accepted: 16 April 1997 相似文献
622.
The photochemistry of the complexes [Ni(Etxn)2(N-N)] [Etxn=ethylxanthate,N-N=2,2-bipyridine(bpy), 4,4-dimethyl-2,2-bipyridine (4,4-Me-bpy), 1,10-phenanthroline (phen) or 2,2-bipyrimidine (bpym)] has been investigated. These complexes were not light sensitive in most solvents such as acetonitrile. Upon irradiation of chloroform solutions of these complexes, a photoredox reaction occurred giving the parent Ni(Etxan)2. It is suggested that the reactive excited state is of the charge-transfer-to-solvent (CTTS) type. The energy of this state depends on the redox potentials of the solvent. When CHCl3 as solvent was replaced by the stronger oxidant CCl4, the photoactive wavelength region was shifted to the red. It was blue shifted when the weaker oxidant CH2Cl2 was used. From quantum yield measurements it is concluded that the photostability of the studied complexes decreases in the following order:bpym>phen>bpy>4,4-Me-bpy.
Photooxidation von Bis(ethylxanthato)nickel(II) mit aromatischen Stickstoffheterocyclen enthaltenden Liganden in Chloroform
Zusammenfassung Es wurde die Photochemie der Komplexe [Ni(Etxn)2(N-N) [Etxn=Ethylxanthat,N-N=2,2-Bipyridin (bpy), 4,4-Dimethyl-2,2-bipyridin (4,4-Me-bpy), 1,10-Phenanthrolin (phen) oder 2,2-bipyrimidin (bpym)] untersucht. Diese Komplexe waren in den meisten Lösungsmitteln wie etwa Acetonitril nicht lichtsensitiv. Bei Bestrahlung von Chloroformlösungen der Komplexe trat jedoch eine Photoreaktion auf, die zum Stammkomplex Ni(Etxn)2 führte. Es wird vorgeschlagen, für den reaktiven angeregten Zustand einen Charge-Transfer-zu-Lösungsmittel (CTTS)-Typ anzunehmen. Die Energie dieses Zustands hängt vom Redoxpotential des Lösungsmittels ab. Bei Ersatz von CHCl3 als Lösungsmittel durch das stärkere Oxidans CCl4 wurde die photoaktive Wellenlänge nach Rot verschoben. Eine Blauverschiebung ergab sich hingegen, wenn das schwächere Oxidans CH2Cl2 verwendet wurde. Aus Messungen der Quantenausbeuten ergab sich die folgende Ordnung nach abnehmender Photostabilität der untersuchten Komplexe:bpym>phen>bpy>4,4-Me-bpy.相似文献
623.
624.
The reaction of 3,3-diphenylindan-1,2-dione with trimethyl phosphite in dry benzene at room temperature for about 15 h led
to the formation of a mixture containing dimethyl (3,3-diphenyl-2-methoxy-1-indenyl)phosphate and dimethyl (3,3-diphenyl-1H-2-oxo-1-indanyl)phosphate, whereas with triisopropyl phosphite, diisopropyl (3,3-diphenyl-2-isopropoxy-1-indenyl)phosphate
is the only product. Treatment of the dione with dialkyl phosphites under different experimental conditions gave dialkyl (3,3-diphenyl-1-hydroxy-2-oxo-1-indanyl)phosphates.
Reaction mechanisms are presented which account for the experimental results. Structural assignments of the new compounds
are based on the spectroscopic evidences and two examples were elucidated by X-ray crystallography. 相似文献
625.
Kekulé indices and conjugated circuits are computed for 36 Kekulé structures, together with two VB quantities associated with the corresponding factor graphs (previously called submolecules). These latter quantitites are nonadjacent numbers of Hosoya and the reciprocal of the connectivity indices of Randi?. It was found that the index of Hosoya successfully orders a set of Kekulé structures belonging to the same hydrocarbon in a parallel order as their Kekulé indices and branching indices. This substantiates the relation between VB and MO theories. A code is derived by summing contributions of nonadjacent numbers in all Kekulé stuctures of a hydrocarbon. The order of the resulting codes is found to be identical to the order of the molecular properties (resonance energies, π-energies, and eigenvalues) of the hydrocarbons. 相似文献
626.
Analysis of diffusion-controlled adsorption and surface tension in one-dimensional planar coordinates with a finite diffusion length and a nonlinear isotherm, such as the Langmuir or Frumkin isotherm, requires numerical solution of the governing equations. This paper presents three numerical methods for solving this problem. First, the often-used integral (I) method with the trapezoidal rule approximation is improved by implementing a technique for error estimation and choosing time-step sizes adaptively. Next, an improved finite difference (FD) method and a new finite element (FE) method are developed. Both methods incorporate (a). an algorithm for generating spatially stretched grids and (b). a predictor-corrector method with adaptive time integration. The analytical solution of the problem for a linear dynamic isotherm (Henry isotherm) is used to validate the numerical solutions. Solutions for the Langmuir and Frumkin isotherms obtained using the I, FD, and FE methods are compared with regard to accuracy and efficiency. The results show that to attain the same accuracy, the FE method is the most efficient of the three methods used. 相似文献
627.
M. Z. Duz Y. Tonbul A. Baysal O. Akba A. Saydut C. Hamamci 《Journal of Thermal Analysis and Calorimetry》2005,81(2):395-398
Summary The relationship between particle size and chemical composition of Hazro coal (origin: SE Anatolia, Turkey) has been examined by elemental analysis and by thermogravimetric pyrolysis. The chemical composition of the coal was determined by grinding sample particles physically and separating according to their size in mm by sieving. Particle size distribution of the coal and chemical composition of these fractions were given. The coal has been non-isothermally pyrolyzed in a thermogravimetric analyzer to determine the kinetic factors. Thermal gravimetric (TG/DTG) experiments were performed from ambient temperature to 800°C under a nitrogen atmosphere at heating rate 10 K min-1 with five different particle size ranges. Kinetic parameters of the samples were determined using a Coats and Redfern kinetic model, assuming a first-order reaction. Depending on the particle size of the coal samples, the mean activation energy values varied between 49.1 and 84.6 kJ mol-1. The results discussed indicate that activation energies increase as the particle size decreases. 相似文献
628.
Osman Tiryaki 《Accreditation and quality assurance》2006,11(10):514-513
Method validation is an important requirement in the practice of pesticide residue analysis and is the process of verifying that a method is fit for its purpose. To make a correct decision on the validity of the method, the following method performance parameters have to be taken into consideration: scope, specificity, limit of detection, limit of quantification, linear range, accuracy, precision, repeatability, reproducibility, recovery, ruggedness and robustness. The goal of this study was to validate previously adapted thin-layer chromatographic methods for the pesticide residue analysis in grain. Confirmation of validation parameters for some compounds was also performed by gas chromatographic analysis. 相似文献
629.
A Λ-type three-level atomic system in the electromagnetically induced transparency (EIT) configuration interacting with a broadband squeezed vacuum (SV) bath is studied with quantum interference (QI) between decay channels taken into account. We formulate two sufficient critical conditions for the medium to be dispersionless or absorptionless. Computational results for the dispersion and absorption spectra show that presence of both QI and SV offers more avenues to manipulate the group velocity of probe pulse for its variation from sub-luminal to super-luminal regimes. The relative phase between the two external fields is found to act as a control knob of the atomic medium. 相似文献
630.
K. I. Osman S. S. Hassan A. Joshi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(1):119-130
The effects of spontaneously generated coherence (SGC) and phases of
optical fields on the phenomenon of electromagnetically induced
transparency (EIT) are investigated in a four-level inverted-Y
system and in a five-level K-type system under various parametric
conditions in order to demonstrate controllability of the EIT,
dispersion properties, and group velocity in such systems. Non-zero
second-order susceptibility in both systems is due to the SGC
effect. The experimental viability of the model in semiconductor
quantum well systems is also discussed. 相似文献