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171.
MP Bhatt P Sista J Hao N Hundt MC Biewer MC Stefan 《Langmuir : the ACS journal of surfaces and colloids》2012,28(35):12762-12770
The influence of the solvent and annealing temperature on the field-effect mobilities and morphologies of poly(3-hexylthiophene)-b-poly(γ-benzyl-l-glutamate) (P3HT-b-PBLG) rod-rod diblock copolymer has been investigated. Thin film X-ray diffraction studies show peaks originating from both P3HT and PBLG indicating that the crystalline nature of both the blocks is conserved after the formation of the block copolymer. It has been observed that the field-effect mobilities of the diblock copolymer are independent of the annealing temperatures for thin films deposited from both 1,2,4-trichlorobenzene and chloroform solvents. The correlation between the field-effect mobility and morphology indicates that the P3HT block self-assembles at the surface SiO(2) dielectric. 相似文献
172.
Savarese M Aliberti A De Santo I Battista E Causa F Netti PA Rega N 《The journal of physical chemistry. A》2012,116(28):7491-7497
Although lifetimes and quantum yields of widely used fluorophores are often largely characterized, a systematic approach providing a rationale of their photophysical behavior on a quantitative basis is still a challenging goal. Here we combine methods rooted in the time-dependent density functional theory and fluorescence lifetime imaging microscopy to accurately determine and analyze fluorescence signatures (lifetime, quantum yield, and band peaks) of several commonly used rhodamine and pyronin dyes. We show that the radiative lifetime of rhodamines can be correlated to the charge transfer from the phenyl toward the xanthene moiety occurring upon the S(0) ← S(1) de-excitation, and to the xanthene/phenyl relative orientation assumed in the S(1) minimum structure, which in turn is variable upon the amino and the phenyl substituents. These findings encourage the synergy of experiment and theory as unique tool to design finely tuned fluorescent probes, such those conceived for modern optical sensors. 相似文献
173.
Emad Yousif Emaad Bakir Jumat Salimon Nadia Salih 《Journal of Saudi Chemical Society》2012,16(3):279-285
The photostabilization of poly(methyl methacrylate) (PMMA) films by Schiff bases of 2,5-dimercapto-1,3,4-thiadiazole compounds was investigated. The PMMA films containing concentration of complexes 0.5% by weight were produced by the casting method from chloroform solvent. The photostabilization activities of these compounds were determined by monitoring the hydroxyl index with irradiation time. The changes in viscosity average molecular weight of PMMA with irradiation time were also tracked (using benzene as a solvent). The quantum yield of the chain scission (Φcs) of these complexes in PMMA films was evaluated and found to range between 4.19 × 10?5 and 8.75 × 10?5. Results obtained showed that the rate of photostabilization of PMMA in the presence of the additive followed the trend:[1] > [2] > [3] > [4] > [5].According to the experimental results obtained, several mechanisms were suggested depending on the structure of the additive. Among them, UV absorption, peroxide decomposer, and radical scavenger for photostabilizer mechanisms were suggested. 相似文献
174.
Ihssan Meskini Maria Daoudi Abdelali Kerbal Brahim Bennani Javed Sheikh Ali Parvez Loic Toupet Taibi Ben Hadda 《Journal of Saudi Chemical Society》2012,16(2):161-173
An efficient and facile method for the synthesis of novel structurally diverse β-amino dicarbonyl compounds is described by exploring the aza-Michael addition reaction in an aqueous medium as a key step. Thereby, 2-(aryl-disubstituted-amino-1-yl-methyl)-malonic acid diethyl esters were achieved in a good to excellent yields. These products were easily isolated with enough purity just by using simple recrystallization. The crystals of the compounds (17) and (24) have been obtained and studied by X-ray crystallographic analyses. 相似文献
175.
Nadia E. A. El-Gamel M. F. Hawash M. A. Fahmey 《Journal of Thermal Analysis and Calorimetry》2012,108(1):253-262
Ciprofloxacin (CPF, C17H18FN3O3) drug is used in the treatment of some bacterial infectious diseases. The drug was investigated using thermal analysis (TA)
measurements (TG/DTG) and electron impact mass spectral (EI-MS) fragmentation at 70 eV techniques. Furthermore, the drug was
characterized and investigated by other spectroscopic tools as IR, UV–Vis, 1H-, and 13C-NMR. Semi-empirical MO calculation using PM3 procedure has been carried out on neutral molecule and positively charged species.
The calculations included, bond length, bond order, bond strain, partial charge distribution, ionization energy, and heat
of formation (ΔH
f). The PM3 procedure provides a basis for fine distinction among sites of initial bond cleavage, which is crucial to the rationalization
of subsequent fragmentation of the molecule. The mass spectra and thermal analysis fragmentation pathways were proposed and
compared to each other to select the most suitable scheme representing the correct fragmentation of this drug. From EI-MS,
the main primary cleavage site of the charged molecule is that due to C–COOH bond cleavage with H-rearrangement to skeleton
and CO2 loss which can further decompose by piperazine loss. Thermal analysis of the neutral form of the drug reveals the high response
of the drug to the temperature variation with very fast rate. Thermal decomposition has carried out in several sequential
steps in the temperature range 40–650 °C. The initial thermal decomposition is similar to that obtained by mass spectrometric
fragmentation (C–COOH fragment) but differ in that a rearrangement occurs by OH and CO loss. Therefore, comparison between
MS and TA helps in selection the proper pathway representing the fragmentation of this drug. This comparison successfully
confirmed by MO calculation. Finally, the effect of fluorine atom on the stability of the drug was discussed. 相似文献
176.
Nadia Mayoufi Didier Dalmazzone Walter Fürst Leila Elghoul Adel Seguatni Anthony Delahaye Laurence Fournaison 《Journal of Thermal Analysis and Calorimetry》2012,109(1):481-486
The phase behaviour of the system water?Ctri-n-butylmethylammonium chloride (TBMAC)?CCO2 was investigated by pressure-controlled differential scanning calorimetry in the range 0?C10?mol% TBMAC in water and at CO2 pressures ranging from 0 to 1.5?MPa. In the absence of CO2, an incongruent melting hydrate, which estimated composition corresponds to TBMAC·30H2O, crystallizes at temperatures below ?13.6?°C and forms with ice a peritectic phase at approximately 3.9?mol% TBMAC. In the presence of CO2 at pressures as low as 0.5?MPa, curves evidenced the presence of an additional phase exhibiting congruent melting at temperatures that are strongly pressure dependent and significantly higher than those of hydrates obtained without CO2. This new phase, whose enthalpy of dissociation and CO2 content increase slightly with CO2 pressure, was identified as a mixed semi-clathrate hydrate of TBMAC and CO2 of general formula: (TBMAC?+?xCO2)·30H2O. 相似文献
177.
Biologically active N-benzoyl-4-(N-maleimido)-phenylhydrazide (BMPH) was synthesized and its structure was confirmed by elemental analysis and various spectral tools. It was examined as a thermal stabilizer and co-stabilizer for rigid poly (vinyl chloride) at 180 °C in air. Blending BMPH with reference samples in different ratios greatly lengthens the thermal stability value and improves the extent of discoloration of PVC. TGA confirmed the improved stability of PVC in presence of the investigated organic stabilizer. GPC measurements were done to investigate the changes occurred in the molecular masses of the degraded samples of blank PVC and PVC in presence of the novel stabilizer. BMPH showed good antimicrobial activity towards two kinds of bacteria and two kinds of fungi. 相似文献
178.
Karol Ciepluch Nadia Katir Abdelkrim El Kadib Monika Weber Anne-Marie Caminade Mostapha Bousmina Jean Pierre Majoral Maria Bryszewska 《Journal of luminescence》2012,132(6):1553-1563
This work deals with photo-physical and structural interactions between viologen phosphorus dendrimers and human serum albumin (HSA). Viologens are derivatives of 4,4′-bipyridinium salts. Aiming to rationalize the parameters governing such interactions eight types of these polycationic dendrimers in which the generation, the number of charges, the nature of the core and of the terminal groups vary from one to another, were designed and used. The influence of viologen-based dendrimers' on human serum albumin has been investigated. The photo-physical interactions of the two systems have been monitored by fluorescence quenching of free l-tryptophan and of HSA tryptophan residue. Additionally, using circular dichroism (CD) the effect of dendrimers on the secondary structure of albumin was measured. The obtained results show that viologen dendrimers interact with human serum albumin quenching its fluorescence either by collisional (dynamic) way or by forming complexes in a ground state (static quenching). In some cases the quenching is accompanied by changes of the secondary structure of HSA. 相似文献
179.
Arumuganathan T Volpe M Harum B Wurm D Belaj F Mösch-Zanetti NC 《Inorganic chemistry》2012,51(1):150-156
The preparation and oxygen-atom-transfer (OAT) reactivity of oxoimido complexes [MoO(N-t-Bu)(t-Bu(2)-4-Rpz)(2)] [where R = H (1), Br (2), and Me (3); t-Bu(2)pz = 3,5-di-tert-butylpyrazolate] are reported. The reaction of the potassium salt of the respective pyrazolate ligands and the molybdenum oxoimido precursor, [MoO(N-t-Bu)Cl(2)(dme)] (dme = dimethoxyethane), in toluene afforded complexes 1-3 in good yields. The complexes were fully characterized by (1)H and (13)C NMR and IR spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray crystallography. The solid-state structures reveal that, in each case, the molybdenum center is coordinated by one oxo, one N-t-Bu group, and two sterically demanding pyrazolate ligands via their two adjacent nitrogen atoms in an η(2) fashion. Coordination around the metal center is severely distorted from octahedral and might be seen as closely approaching a distorted trigonal-prismatic geometry, which is relevant to the active site of dimethyl sulfoxide reductase in its oxidized form. The potential utility of all of the complexes 1-3 for OAT reactivity toward PMe(3) at room temperature is examined, and plausible mechanistic pathways are explored by density functional theory calculations. Furthermore, the complexes reported here open a new and convenient entry into mixed oxoimidomolybdenum complexes. 相似文献
180.
Nadia T. Zakharova Michael I. Mishchenko 《Journal of Quantitative Spectroscopy & Radiative Transfer》2001,70(4-6):465-471
We use the T-matrix method to compute the scattering matrix for randomly oriented circular ice cylinders with diameter-to-length ratios 1 and 20 and surface-equivalent-sphere size parameters up to 12. We show that wavelength-sized, sharp-edged ice plates with extreme diameter-to-length ratios possess the same scattering properties as smooth platelike spheroids: their phase functions are similar to those of surface-equivalent compact particles, whereas all other elements of the scattering matrix are typical of Rayleigh scattering. 相似文献