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991.
P. C. do Nascimento Denise Bohrer A. L. B. Rohlfes Leandro M. de Carvalho Adrain Ramirez 《Analytical and bioanalytical chemistry》2001,370(1):92-96
A method has been developed for the chromatographic determination of methanethiol (MT) and ethanethiol (ET) as contaminants in amino acid parenteral nutrition (PN) solutions. The clean-up of the samples before chromatographic analysis was investigated by solid-phase extraction (SPE) on pre-columns filled with polyethylene powder (PE), aluminium oxide (AlOx), silica (SiOx), or polyurethane foam (PUF) as adsorbents. The thiols were more efficiently separated from the matrices by SPE on PUF pre-columns. Simultaneous derivatization and elution with DTNB (5,5′-dithiobis(2-nitrobenzoic acid)) enabled further discrimination between MT and ET by reversed-phase HPLC with spectrophotometric detection. The retention times for the derivatized MT and ET species were 12.5 and 23.0 min, respectively. Recoveries from spiked PN samples were calculated to be approximately 90%, and the MT and ET content of commercial PN solutions was determined using the methodology described. Detection limits of 15 and 10 μg L–1 were calculated for MT and ET, respectively. 相似文献
992.
M. Jos Alves M. Alice Carvalho M. Fernanda J. R. P. Proena Brian L. Booth Robin G. Pritchard 《Journal of heterocyclic chemistry》1999,36(1):193-199
Formation of 5-amino-3,4-di[(N,N-dimethylarnino)methylidenearnino]-2H-2-iminopyrroles 3 from the reaction of (Z)-N1-(2-amino-1,2-dicyanovinyl)-N2-substituted-formamidines 1 with dimethylformamide diethyl acetal has been shown to occur by initial formation of (Z)-N1-{l,2-dicyano-2-[N,N-dimethylamino)methylideneamino]vinyl}formamidines 8 (isolated), followed by base catalysed cyclisation and imi dazole ring opening by dimethyl amine. The kinetic product of the ring opening reaction is the 2,5-diimino2,5-dihydropyrrole derivatives 11, which have been isolated and characterized spectroscopically and by a single crystal X-ray analysis on the R = Ph derivative. In solution at room temperature the N-aryl derivatives undergo a rapid Dimroth rearrangement to give the thermodynamic ally more stable isomer 3 , but compound 11 (R = Me) is much more stable in solution. 相似文献
993.
Zanin Gisella M. Santana Cesar C. Bon Elba P. S. Giordano Raquel C. L. de Moraes Flávio F. Andrietta Silvio R. Neto Carlos Coelho De Carvalho Macedo Isaias C. Lahr Fo. Djalma Ramos Luiz P. Fontana José D. 《Applied biochemistry and biotechnology》2000,84(1-9):1147-1161
Brazil is the largest producer of bioethanol, and sugarcane is the main raw material. Bioethanol, is produced by both batch
and continuous processes, and in some cases, flocculating yeast is use. This article analyzes the Bracilian Ethanol Program.
for the 1996–1997 havest, Brazil produced 14.16 billion L of ethanol and 13.8 million metrict of sugar, from 286 million metrict
of sugarcane. These products were produced by 328 industries inactivity, with 101 autonomousethanol plants producing only
ethanol, and 227 sugar mills producing sugar and ethanol. The sugar-ethanol market reaches about 7.5 billion US$/yr, accounting
for direct and indirect revenues. 相似文献
994.
Ana M. Cardoso Cristina M. F. Barros A. J. Ferrer Correia J. M. Cardoso A. Cortez F. Carvalho L. Baldaia 《Journal of the American Society for Mass Spectrometry》1997,8(4):365-370
The identification of testosterone, pregnelonone, and 17α-hydroxyprogesterone by tandem mass spectrometry and of progesterone by sequential product ion scanning in the shrimp gonads of Penaeus japonicus is described. The identification of these substances in biological samples is usually done by gas chromatography-mass spectrometry and involves several liquid chromotographic purification steps followed by derivatization. The utilization of tandem mass spectrometry in this analysis has simplified considerably the sample pretreatment and provided a very simple method of screening these substances in complex mixtures. 相似文献
995.
996.
Marília Vilela Salvador Flvio Vinícius Crizstomo Kock Isabella Laporte Santos Jean Fausto Carvalho Paulino Calo Panhoca de Almeida Rodrigo Henrique dos Santos Garcia Luciana Lasry Benchimol-Reis Luiz Alberto Colnago Antonio Gilberto Ferreira 《Molecules (Basel, Switzerland)》2022,27(7)
The use of UV-C cool white light on bean (Phaseolus vulgaris L.) seeds significantly increases the biochemical seed coat post-harvest darkening process, whilst preserving seed germination. The aim of this work consists in monitoring the effect caused by the incidence of UV-C light on different bean genotypes using NMR spectroscopy. The genotype samples named IAC Alvorada; TAA Dama; BRS Estilo and BRS Pérola from the Agronomic Institute (IAC; Campinas; SP; Brazil) were evaluated. The following two methodologies were used: a prolonged darkening, in which the grain is placed in a room at a controlled temperature (298 K) and humidity for 90 days, simulating the supermarket shelf; an accelerated darkening, where the grains are exposed to UV-C light (254 nm) for 96 h. The experiments were performed using the following innovative time-domain (TD) NMR approaches: the RK-ROSE pulse sequence; one- and two-dimensional high resolution (HR) NMR experiments (1H; 1H-1H COSY and 1H-13C HSQC); chemometrics tools, such as PLS-DA and heat plots. The results suggest that the observed darkening occurs on the tegument after prolonged (90 days) and accelerated (96 h) conditions. In addition, the results indicate that phenylalanine is the relevant metabolite within this context, being able to participate in the chemical reactions accounted for by the darkening processes. Additionally, it is possible to confirm that a UV-C lamp accelerates oxidative enzymatic reactions and that the NMR methods used were a trustworthy approach to monitor and understand the darkening in bean seeds at metabolite level. 相似文献
997.
Andr M. Marques Alexandre Siqueira da Rocha Queiroz Elsie F. Guimares Ana Carolina Mafud Paulo de Sousa Carvalho Yvonne Primerano Mascarenhas Thais da Silva Barenco Pmella Dourila N. Souza David William Provance Jos Hamilton M. do Nascimento Cristiano G. Ponte Maria Auxiliadora C. Kaplan Davyson de Lima Moreira Maria Raquel Figueiredo 《Molecules (Basel, Switzerland)》2022,27(4)
The Piper species are a recognized botanical source of a broad structural diversity of lignans and its derivatives. For the first time, Piper tectoniifolium Kunth is presented as a promising natural source of the bioactive (−)-grandisin. Phytochemical analyses of extracts from its leaves, branches and inflorescences showed the presence of the target compound in large amounts, with leaf extracts found to contain up to 52.78% in its composition. A new HPLC-DAD-UV method was developed and validated to be selective for the identification of (−)-grandisin being sensitive, linear, precise, exact, robust and with a recovery above 90%. The absolute configuration of the molecule was determined by X-ray diffraction. Despite the identification of several enantiomers in plant extracts, the major isolated substance was characterized to be the (−)-grandisin enantiomer. In vascular reactivity tests, it was shown that the grandisin purified from botanical extracts presented an endothelium-dependent vasorelaxant effect with an IC50 of 9.8 ± 1.22 μM and around 80% relaxation at 30 μM. These results suggest that P. tectoniifolium has the potential to serve as a renewable source of grandisin on a large scale and the potential to serve as template for development of new drugs for vascular diseases with emphasis on disorders related to endothelial disfunction. 相似文献
998.
Juarez Vicente Leandro Pereira Cappato Verônica Maria de Araújo Calado Mario Geraldo de Carvalho Edwin Elard Garcia-Rojas 《Journal of Thermal Analysis and Calorimetry》2018,131(3):2093-2104
The oxidative stability of edible oils is an important feature to know due the undesirable changes that can occur in the storage. In this way, the oxidative induction time (OIT) value is an indicative to prevent this effect. The objectives of this study were to evaluate the omega-3 content and kinetic parameters of Sacha Inchi oil (SIO) and capsules that are formed with biopolymers, in addition, there were analyzed with differential scanning calorimetry (DSC) and proton nuclear magnetic resonance (1H NMR). The SIO and capsules, formed using an emulsion, were analyzed with DSC in an oxygen atmosphere to determine the OIT value in isothermal conditions at 100, 120 and 150 °C. The kinetic parameters (activation energy, pre-exponential factor and z value) of SIO were obtained, and the stability time was predicted at different temperatures. The 1H NMR spectra enabled us to assess the identification and percentage relative before and after the isothermal DSC oxidation of omega-3 concentration and formation of their oxidized compounds. (E-E)-2,4-Alkadienals were the primary oxidized compound and is strongly correlated with the decrease in omega-3 content. Isothermal DSC is a useful to determine the OIT (min) and kinetic parameters to predict the stability oxidation in different edible oils and thus prevent the inadequate consumption of edible oils oxidized. 相似文献
999.
Paulo Vieira Margarida Q. Miranda Dr. Igor Marques Dr. Sílvia Carvalho Dr. Li-Jun Chen Dr. Ethan N. W. Howe Carl Zhen Claudia Y. Leung Dr. Michael J. Spooner Bárbara Morgado Prof. Odete A. B. da Cruz e Silva Prof. Cristina Moiteiro Prof. Philip A. Gale Prof. Vítor Félix 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(4):888-899
The anion-binding and transport properties of an extensive library of thiophene-based molecules are reported. Seventeen bis-urea positional isomers, with different binding conformations and lipophilicities, have been synthesized by appending α- or β-thiophene or α-, β-, or γ-benzo[b]thiophene moieties to an ortho-phenylenediamine central core, yielding six subsets of positional isomers. Through 1H NMR, X-ray crystallography, molecular modelling, and anion efflux studies, it is demonstrated that the most active transporters adopt a pre-organized binding conformation capable of promoting the recognition of chloride, using urea and C−H binding groups in a cooperative fashion. Additional large unilamellar vesicle-based assays, carried out under electroneutral and electrogenic conditions, together with N-methyl-d -glucamine chloride assays, have indicated that anion efflux occurs mainly through an H+/Cl− symport mechanism. On the other hand, the most efficient anion transporter displays cytotoxicity against tumor cell lines, while having no effects on a cystic fibrosis cell line. 相似文献
1000.
Raquel Costa Daniela Azevedo Pedro Barata Raquel Soares Luís F. Guido Daniel O. Carvalho 《Molecules (Basel, Switzerland)》2021,26(7)
The Euterpe oleracea fruit (açaí) is a promising source of polyphenols with health-promoting properties. To our knowledge, few studies have focused on the influence of açaí phytochemicals on angiogenesis, with a significant impact on cancer. This study aimed at investigating the phytochemical profile of a purple açaí hydroethanolic extract (AHE) obtained from a commercial dietary powder supplement by high-performance liquid chromatography coupled to diode array detection and electrospray ionization mass spectrometry, and evaluate its in vitro effects on distinct angiogenic steps during vessel growth and on oxidative markers in human microvascular endothelial cells (HMEC-1). The phenolic profile of AHE revealed the presence of significant levels of anthocyanins, mainly cyanidin-3-O-rutinoside, and other flavonoids with promising health effects. The in vitro studies demonstrated that AHE exerts antiangiogenic activity with no cytotoxic effect. The AHE was able to decrease HMEC-1 migration and invasion potential, as well as to inhibit the formation of capillary-like structures. Additionally, AHE increased antioxidant defenses by upregulating superoxide dismutase and catalase enzymatic activities, accompanied by a reduction in the production of reactive oxygen species. These data bring new insights into the potential application of angiogenic inhibitors present in AHE on the development of novel therapeutic approaches for angiogenesis-dependent diseases. 相似文献