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991.
Freitas LS Von Mühlen C Bortoluzzi JH Zini CA Fortuny M Dariva C Coutinho RC Santos AF Caramão EB 《Journal of chromatography. A》2009,1216(14):2860-2865
In this work the higher peak capacity and resolution of comprehensive two-dimensional gas chromatography (GCxGC) has been successfully applied, for the first time, to tentatively identify several polar organic compounds of organic extracts of aqueous phases resulting from microwave demulsification process of water-in-crude oil emulsions. Results have shown that higher temperatures and longer exposure time to microwave irradiation produced water phases with a wider variety of polar organic compounds. The microwave process showed to be suitable for the extraction of several polar compounds classes of petroleum. The proposed microwave extraction method and GCxGC identification of polar compounds of petroleum samples are of practical interest for the petrochemical industry due to corrosion and related problems associated with these polar compounds in refinery equipments. The GCxGC/time-of-flight MS technique shows to be very important in the total separation of different classes of compounds and allows the identification of many compounds in these classes. 相似文献
992.
Determination of organic and inorganic mercury species in water and sediment samples by HPLC on-line coupled with ICP-MS 总被引:2,自引:0,他引:2
José Soares dos Santos Miguel de la Guárdia Maria Lúcia Pires dos Santos 《Talanta》2009,80(1):207-3009
This paper describes a preconcentration method for Hg2+ and MeHg+ in water samples using sodium diethyldithiocarbamate immobilized in polyurethane foam (PU-NaDDC) and an extraction method for several mercury species in sediment samples, including MeHg+, EtHg+ and PhHg+, which is simple, rapid, and uses a single organic solvent. Separation and measurement were done by high-performance liquid chromatography on-line with inductively coupled plasma mass spectrometry (HPLC/ICP-MS). Initially, the test of recovery was applied using procedures compatible with HPLC. Under the optimum extraction conditions, recoveries of 96.7, 96.3 and 97.3% were obtained for MeHg+, EtHg+, and PhHg+, respectively, from n = 4 spiked sediment samples. This study also demonstrates that the combination of solid-phase extraction on PU-NaDDC with HPLC separation and ICP-MS detection is an effective preconcentration procedure for simultaneous measurement of Hg2+ and MeHg+ at ultra-trace levels in water samples. The application of the proposed procedure to the determination of mercury species in drinking water sample was investigated. The proposed method clearly gave satisfactory average recoveries between 93.7 and 101.5%. 相似文献
993.
Characterization of polyphosphoesters by fourier transform ion cyclotron resonance mass spectrometry
Malgorzata A. Kaczorowska Helen J. Cooper 《Journal of the American Society for Mass Spectrometry》2009,20(12):2238-2247
FT-ICR mass spectrometry, together with collision-induced dissociation and electron capture dissociation, has been used to
characterize the polyphosphoester poly[1,4-bis(hydroxyethyl)terephthalate-alt-ethyloxyphosphate] and its degradation products. Three degradation pathways were elucidated: hydrolysis of the phosphate-[1,4-bis(hydroxyethyl)terephthalate]
bonds; hydrolysis of the phosphate-ethoxy bonds; and hydrolysis of the ethyl-terephthalate bonds. The dominant degradation
reactions were those that involved the phosphate groups. This work constitutes the first application of mass spectrometry
to the characterization of polyphosphoesters and demonstrates the suitability of high mass accuracy FT-ICR mass spectrometry,
with CID and ECD, for the structural analysis of polyphosphoesters and their degradation products. 相似文献
994.
Victor A. Mikhailov Helen J. Cooper 《Journal of the American Society for Mass Spectrometry》2009,20(5):763-771
Here, we show that to perform activated ion electron capture dissociation (AI-ECD) in a Fourier transform ion cyclotron resonance
(FT-ICR) mass spectrometer equipped with a CO2 laser, it is necessary to synchronize both infrared irradiation and electron capture dissociation with ion magnetron motion.
This requirement is essential for instruments in which the infrared laser is angled off-axis, such as the Thermo Finnigan
LTQ FT. Generally, the electron irradiation time required for proteins is much shorter (ms) than that required for peptides
(tens of ms), and the modulation of ECD, AI ECD, and infrared multiphoton dissociation (IRMPD) with ion magnetron motion is
more pronounced. We have optimized AI ECD for ubiquitin, cytochrome c, and myoglobin; however the results can be extended to other proteins. We demonstrate that pre-ECD and post-ECD activation
are physically different and display different kinetics. We also demonstrate how, by use of appropriate AI ECD time sequences
and normalization, the kinetics of protein gas-phase refolding can be deconvoluted from the diffusion of the ion cloud and
measured on the time scale longer than the period of ion magnetron motion. 相似文献
995.
M. A. V. Ribeiro da Silva Ana Filipa L. O. M. Santos 《Journal of Thermal Analysis and Calorimetry》2009,95(2):333-344
The present work is part of a broader research program on the energetics of formation of heterocycles, aiming the study of
the enthalpic effects of the introduction of different substituents into heterocycles. In this work we present the results
of the thermochemical research on sulphur heterocycles of the type substituted thiophenes with different kind of substituents,
mainly alkyl, ester, acetyl, carboxamide, acetamide, carbonitrile and carboxaldehyde.
The standard (p
o=0.1 MPa) molar enthalpies of formation, in the condensed phase, at T=298.15 K, of a large number of substituted thiophenes, were derived from their standard massic energies of combustion, measured
by rotating-bomb combustion calorimetry, while the standard molar enthalpies of vaporization or sublimation of those compounds
were obtained either by high temperature Calvet Microcalorimetry, or by the temperature dependence of their vapour pressures
determined by the Knudsen effusion technique. The standard molar enthalpies of formation, of the studied sulphur heterocycles
in the gaseous phase, were then derived. The results are interpreted in terms of structural contributions to the energetics
of the substituted thiophenes, the internal consistency of the results is discussed and, whenever appropriate and possible,
empirical correlations are suggested for the estimation of standard molar enthalpies of formation, at T=298.15 K, of substituted thiophenes. A Table of enthalpic increments for different group substituents in positions 2 or 3
of the thiophene ring has been established. 相似文献
996.
A. L. M. de Oliveira J. M. Ferreira Márcia R. S. Silva Soraia C. de Souza F. T. G. Vieira E. Longo A. G. Souza Iêda M. G. Santos 《Journal of Thermal Analysis and Calorimetry》2009,97(1):167-172
NiWO4 and ZnWO4 were synthesized by the polymeric precursor method at low temperatures with zinc or nickel carbonate as secondary phase.
The materials were characterized by thermal analysis (TG/DTA), infrared spectroscopy, UV–Vis spectroscopy and X-ray diffraction.
NiWO4 was crystalline after calcination at 350 °C/12 h while ZnWO4 only crystallized after calcination at 400 °C for 2 h. Thermal decomposition of the powder precursor of NiWO4 heat treated for 12 h had one exothermic transition, while the precursor heat treated for 24 h had one more step between
600 and 800 °C with a small mass gain. Powder precursor of ZnWO4 presented three exothermic transitions, with peak temperatures and mass losses higher than NiWO4 has indicating that nickel made carbon elimination easier. 相似文献
997.
998.
Hao Wang Dr. Shutao Wang Dr. Helen Su Dr. Kuan‐Ju Chen Amanda Lee Armijo Wei‐Yu Lin Dr. Yanju Wang Dr. Jing Sun Dr. Ken‐ichiro Kamei Dr. Johannes Czernin Prof. Caius G. Radu Prof. Hsian‐Rong Tseng Prof. 《Angewandte Chemie (International ed. in English)》2009,48(24):4344-4348
A supramolecular approach has been developed for the preparation of supramolecular nanoparticles (SNPs) with variable sizes (30–450 nm) from three different molecular building blocks using a cyclodextrin/adamantane recognition system. Positron emission tomography (PET) was employed to study the biodistribution and lymph node drainage of the SNPs in mice. The sizes of the SNPs affect their in vivo characteristics (see picture).
999.
1000.
Nikolaos Raikos Georgios Theodoridis Efi Alexiadou Helen Gika Helena Argiriadou Heleni Parlapani Heleni Tsoukali 《Journal of separation science》2009,32(7):1018-1026
The determination of widely used anaesthetic and analgesic drugs in biological fluids is of major clinical importance. Typical methods used for sample preparation employ liquid–liquid extraction protocols which are complex, costly, not handy and not amenable to automation. In the present communication, we report the development of a methodology that employs headspace solid‐phase microextraction (HS‐SPME) for the determination of four anaesthetic (lidocaine, midazolam, diazepam and ketamine) and three analgesic drugs (fentanyl, remifentanyl and codeine) in human urine. Important parameters controlling SPME were studied: selection of SPME fibre, type and amount of salt added, preheating and extraction time, extraction temperature, sample volume and desorption time. GC with nitrogen phosphorus detection (GC‐NPD) facilitates sensitive and selective detection of the anaesthetics. The developed method renders an efficient tool for the precise and sensitive determination of the anaesthetics and analgesics in human urine (RSDs ranged from 7.7 to 12.6%, whereas LODs ranged from 0.01 to 1.5 ng/mL). The method was applied to the determination of the anaesthetics and analgesics in human urine from patients that had undergone coronary by‐pass surgery operations. The proposed protocol can function as an attractive alternative for clinical acute intoxications and medico‐legal cases. 相似文献