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991.
Samuele Lilliu Tiziano Agostinelli Eric Verploegen Ellis Pires Mark Hampton Mohammed Al‐Hashimi Martin J. Heeney Michael F. Toney Jenny Nelson J. Emyr Macdonald 《Macromolecular rapid communications》2011,32(18):1454-1460
Grazing incidence X‐ray diffraction (GI‐XRD) is used to characterize the crystallographic dynamics of low molecular weight (LMW) and high molecular weight (HMW) poly(3‐hexylselenophene) (P3HS) films and blend films of P3HS with [6‐6‐]‐phenyl‐C61‐butyric acid methyl ester (PCBM) as a function of ‘step‐by‐step’ thermal annealing, from room temperature to 250 °C. The temperature‐dependent GIXRD data show how the melting point of P3HS crystallites is decreased by the presence of PCBM. P3HS crystallite domain sizes dramatically increase upon annealing to the P3HS melting temperature. The formation of well‐oriented HMW P3HS crystallites with the (100) plane parallel to the substrate (edge‐on orientation), when cooled from melt, are observed. We compare the behaviour of P3HS pure and blend films with that of poly(3‐hexyl)thiophene (P3HT) pure and PCBM blended films and suggest that the similar temperature dependent behaviour we observe may be a common to polythiophene and related polymers and their blends.
992.
Rodrigo Irani Medeiros Nelson Roberto Antoniosi Filho Maria Inês Gon?alves Leles 《Journal of Thermal Analysis and Calorimetry》2009,97(1):337-342
The objective of this work is the TG and DSC analysis of “Merla” samples as well as the separation and identification of organic
compounds by Ultra Fast GC method. The obtained results showed the grouping and the establishment of the degree of the sample’s similarity based in
the Euclidean Distance. The cluster was a useful tool to determine if the samples, confiscated from different users by police,
were manufactured in the same or different laboratories. Consequently one can conclude if in any city operates one or more
drug manufacturing laboratories. 相似文献
993.
Christian Piontek Dr. Petra Ring Olaf Harjes Christian Heinlein Stefano Mezzato Dr. Nelson Lombana Claudia Pöhner Markus Püttner Dr. Daniel Varón Silva Dr. Andreas Martin Dr. Franz Xaver Schmid Prof. Carlo Unverzagt Prof. 《Angewandte Chemie (International ed. in English)》2009,48(11):1936-1940
Seven in one blow : The efficient formation of mixed disulfides on the thiol‐rich fusion protein A followed by subsequent intein cleavage gave the fragment B with all seven cysteines protected against oxidation. The native chemical ligation of B with synthetic glycopeptide thioesters provides glycoproteins.
994.
Pilar Viñas Nelson Martínez-CastilloNatalia Campillo Manuel Hernández-Córdoba 《Journal of chromatography. A》2010,1217(42):6569-6577
Two procedures are proposed based on ultrasound-assisted emulsification and single-drop liquid–liquid microextraction for the sensitive determination of seven strobilurin and six oxazole fungicides in fruits and juice samples. Both miniaturized techniques are coupled to gas chromatography with mass spectrometry in the selected ion monitoring mode, GC–MS(SIM). The procedures use low density organic solvents, and several factors influencing the emulsification, extraction and collection efficiency are optimized. The detection limits obtained at a signal-to-noise ratio of 3 are below the MRLs set by the European Commission. Enrichment factors are between 140–1140 for the first technique used and 80–1600 for the latter. The recoveries obtained for spiked samples are satisfactory for all compounds. The methods are validated according to the Commission Decision 2002/657/EC. Different fruit and juices are analyzed by the proposed method and none of the samples contained fungicide residues above the detection limits. 相似文献
995.
Nelson A. Galiote Renato L.T. Parreira José M. Rosolen Fritz Huguenin 《Electrochemistry communications》2010,12(6):733-736
WO3/chitosan and WO3/chitosan/poly(ethylene oxide) (PEO) films were prepared by the layer-by-layer method. The presence of chitosan enabled PEO to be carried into the self-assembled structure, contributing to an increase in the Li+ diffusion rate. On the basis of the galvanostatic intermittent titration technique (GITT) and the quadratic logistic equation (QLE), a spectroelectrochemical method was used for determination of the “optical” diffusion coefficient (Dop), enabling analysis of the Li+ diffusion rate and, consequently, the coloration front rate in these host matrices. The Dop values within the WO3/chitosan/PEO film were significantly higher than those within the WO3/chitosan film, mainly for higher values of injected charge. The presence of PEO also ensured larger accessibility to the electroactive sites, in accordance with the method employed here. Hence, this spectroelectrochemical method allowed us to separate the contribution of the diffusion process from the number of accessible electroactive sites in the materials, thereby aiding a better understanding of the useful electrochemical and electrochromic properties of these films for use in electrochromic devices. 相似文献
996.
Steven C. Habicht Nelson R. Vinueza Penggao Duan Mingkun Fu Hilkka I. Kenttämaa 《Journal of the American Society for Mass Spectrometry》2010,21(4):559-563
We report here an automated method for the identification of N-oxide functional groups in drug metabolites by using the combination
of liquid chromatography/tandem mass spectrometry (LC/MS
n
) based on ion-molecule reactions and collision-activated dissociation (CAD). Data-dependent acquisition, which has been readily
utilized for metabolite characterization using CAD-based methods, is adapted for use with ion-molecule reaction-based tandem
mass spectrometry by careful choice of select experimental parameters. Two different experiments utilizing ion-molecule reactions
are demonstrated, data-dependent neutral gain MS3 and data-dependent neutral gain pseudo-MS3, both of which generate functional group selective mass spectral data in a single experiment and facilitate increased throughput
in structural elucidation of unknown mixture components. Initial results have been generated by using an LC/MS
n
method based on ion-molecule reactions developed earlier for the identification of the N-oxide functional group in pharmaceutical
samples, a notoriously difficult functional group to identify via CAD alone. Since commercial software and straightforward,
external instrument modification are used, these experiments are readily adaptable to the industrial pharmaceutical laboratory. 相似文献
997.
Sanders DP Fukushima K Coady DJ Nelson A Fujiwara M Yasumoto M Hedrick JL 《Journal of the American Chemical Society》2010,132(42):14724-14726
An improved two-step synthetic route to functionalized cyclic carbonate monomers that features a novel cyclic carbonate intermediate with an active pentafluorophenyl ester group (MTC-OPhF(5)) has been developed. The versatile pentafluorophenyl ester intermediate can be synthesized on the gram to kilogram scale in one high-yielding step and is easy to store and handle on the benchtop. The active pentafluorophenyl ester of MTC-OPhF(5) is amenable to further substitution with suitable nucleophiles such as alcohols and amines to generate functionalized cyclic carbonates in high yields. The substitution reaction is tolerant of a wide variety of functionalities, including various hydrophobic and hydrophilic groups, reactive functionalities (via thiol-ene click chemistry or alkyl halides), and protected acids, alcohols, thiols, and amines. In view of the ever-increasing need for biodegradable and biocompatible polymers, this new methodology provides a simple and versatile platform for the synthesis of new and innovative materials. 相似文献
998.
Since their discovery in 1997, iridium-catalysed asymmetric allylic substitutions have been developed into a broadly applicable tool for the synthesis of chiral building blocks via C-C and C-heteroatom bond formation. The remarkable generality of these reactions and the high levels of regio- and enantioselectivity that are usually obtained in favour of the branched products have been made possible by a thorough investigation of the catalyst system and its mode of action. Therefore, today the Ir-catalysed asymmetric allylic substitution is a powerful reaction in the organic chemist's repertoire and has been used extensively for several applications. This article aims to provide an overview of the development of iridium catalysts derived from an Ir salt and a chiral phosphoramidite and their application to the enantioselective synthesis of natural products and biologically relevant compounds. 相似文献
999.
1000.
During the "Standards Development and International Harmonization: AOAC INTERNATIONAL Mid-Year Meeting," on June 29, 2011, the method "Determination of vitamin B12 in infant formula and adult nutritionals using HPLC after purification on an immunoaffinity column" was recommended by an Expert Review Panel and adopted as AOAC Official First Action status. The method is applicable for the determination of vitamin B12 in milk-based infant formula. Vitamin B12 is extracted from the sample in sodium acetate buffer in the presence of potassium cyanide. After purification and concentration with an immunoaffinity column (IAC), vitamin B12 is determined by LC with UV detection (361 nm). Data supplied by CLF demonstrated linear response over a wide range of concentrations (1.4-39 microg/100 mL). The analytical range is 0.2-10 microg/100 g, depending on the capacity of the IACs (0.01-0.5 microg), the input weight, and dilutions. Recovery rates were assessed using National Institute of Standards and Technology SRM 1849, and determined to be 95.1%, with SD of 0.34 and CV of 9.0. Measurement uncertainty (UE) was 0.8 microg/100 g, which was calculated from the validation data. It is an expanded measurement uncertainty and was obtained through multiplication with a coverage factor k. LOQ values were reported as 0.10 microg/100 g. The performance characteristics of the method met the standard method performance requirements set forth by the AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals; thus, the method was determined to be appropriate for First Action status. 相似文献