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71.
Lidiane Pinto Correia Elisana Afonso de Moura Hallisson Meneses Pires Rui Oliveira Macêdo 《Journal of Thermal Analysis and Calorimetry》2011,106(2):459-461
Water is a fundamental element of life. Its multiple uses are indispensable for a wide spectrum of human activities. This
study aims to characterize water from different salinities obtained in the Cariri region of Paraíba, Brazil. The samples were
analyzed using the DSC-coupled to the Peltier system (DSC-Cooling) and physical–chemical water tests performed employing reactive
kits, using the Spectroquant Merck? specific for each test. The calorimetric curves showed crystallization phase transitions with different characteristics in
peak format and crystallization temperatures between the samples of different salinities. The calorimetric data obtained in
the process of crystallization of water is directly correlated to the physico-chemical parameters of conductivity and total
dissolved solids, showing that the analytical technology DSC-cooling/heating is suitable for characterization of different
salinities water. 相似文献
72.
Paolo Dapporto Paola Paoli Carla Bazzicalupi Andrea Bencini Nicoletta Nardi Barbara Valtancoli 《Supramolecular chemistry》2013,25(3):195-200
Abstract In preceding works, which have dealt with the synthesis and characterisation of a series of macrobicyclic compounds with five donor atoms, the unusually high basicity constants of these polyaminic cage-like molecules have been ascribed to the inclusion of the proton inside the macrobicyclic cavity which results in a very efficient hydrogen-bond network. The present paper, based on previously reported X-ray crystal structures regarding five-atoms bridging units and on molecular modelling studies shows that the disposition of the five donor atoms in the monoprotonated species is related to the protonation site. Precisely, if the protonation occurs on a bridge-head nitrogen the resulting geometry of the donors is a trigonal bipyramid, whereas it is square pyramidal when the proton is bound to a nitrogen belonging to a macrobicyclic chain. For what concerns the geometrical array of the donor atoms in the free amines, the favoured array seems to be the trigonal bipyramidal. 相似文献
73.
Latifa Latrous Jeanine Tortajada Violette Haldys Emmanuelle Léon Catarina Correia Jean‐Yves Salpin 《Journal of mass spectrometry : JMS》2013,48(7):795-806
Gas‐phase interactions of organotins with glycine have been studied by combining mass spectrometry experiments and quantum calculations. Positive‐ion electrospray spectra show that the interaction of di‐ and tri‐organotins with glycine results in the formation of [(R)2Sn(Gly)‐H]+and [(R)3Sn(Gly)]+ ions, respectively. Di‐organotin complexes appear much more reactive than those involving tri‐organotins. (MS/MS) spectra of the [(R)3Sn(Gly)]+ ions are indeed simple and only show elimination of intact glycine, generating the [(R)3Sn]+ carbocation. On the other hand, MS/MS spectra of [(R)2Sn(Gly)‐H]+complexes are characterized by numerous fragmentation processes. Six of them, associated with elimination of H2O, CO, H2O + CO and formation of [(R)2SnOH]+ (?57 u),[(R)2SnNH2]+( ?58 u) and [(R)2SnH]+ (?73 u), are systematically observed. Use of labeled glycines notably concludes that the hydrogen atoms eliminated in water and H2O + CO are labile hydrogens. A similar conclusion can be made for hydrogens of [(R2)SnOH]+and [(R2)SnNH2]+ions. Interestingly, formation [(R)2SnH]+ ions is characterized by a migration of one the α hydrogen of glycine onto the metallic center. Finally, several dissociation routes are observed and are characteristic of a given organic substituent. Calculations indicated that the interaction between organotins and glycine is mostly electrostatic. For [(R)2Sn(Gly)‐H]+complexes, a preferable bidentate interaction of the type η2‐O,NH2 is observed, similar to that encountered for other metal ions. [(R)3Sn]+ ions strongly stabilize the zwitterionic form of glycine, which is practically degenerate with respect to neutral glycine. In addition, the interconversion between both forms is almost barrierless. Suitable mechanisms are proposed in order to account for the most relevant fragmentation processes. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
74.
Francesca Bettazzi Ezat Hamid-Asl Carla Lucia Esposito Cristina Quintavalle Nello Formisano Serena Laschi Silvia Catuogno Margherita Iaboni Giovanna Marrazza Marco Mascini Laura Cerchia Vittorio De Franciscis Gerolama Condorelli Ilaria Palchetti 《Analytical and bioanalytical chemistry》2013,405(2-3):1025-1034
MicroRNAs (miRNAs, miRs) are naturally occurring small RNAs (approximately 22 nucleotides in length) that have critical functions in a variety of biological processes, including tumorigenesis. They are an important target for detection technology for future medical diagnostics. In this paper we report an electrochemical method for miRNA detection based on paramagnetic beads and enzyme amplification. In particular, miR 222 was chosen as model sequence, because of its involvement in brain, lung, and liver cancers. The proposed bioassay is based on biotinylated DNA capture probes immobilized on streptavidin-coated paramagnetic beads. Total RNA was extracted from the cell sample, enriched for small RNA, biotinylated, and then hybridized with the capture probe on the beads. The beads were then incubated with streptavidin–alkaline phosphatase and exposed to the appropriate enzymatic substrate. The product of the enzymatic reaction was electrochemically monitored. The assay was finally tested with a compact microfluidic device which enables multiplexed analysis of eight different samples with a detection limit of 7 pmol L?1 and RSD?=?15 %. RNA samples from non-small-cell lung cancer and glioblastoma cell lines were also analyzed. 相似文献
75.
Dr. Annalisa Mancini Dr. M. Carla Aragoni Dr. Neil Bricklebank Dr. Carlo Castellano Prof. Francesco Demartin Prof. Francesco Isaia Prof. Vito Lippolis Dr. Anna Pintus Dr. Massimiliano Arca 《化学:亚洲杂志》2013,8(3):639-647
The reactions of 4,5,6,7‐tetrathiocino‐[1,2‐b:3,4‐b′]‐1,3,8,10‐tetrasubstituted‐diimidazolyl‐2,9‐dithiones (R2,R′2‐todit; 1 : R=R′=Et; 2 : R=R′=Ph; 3 : R=Et, R′=Ph) with Br2 exclusively afforded 1:1 and 1:2 “T‐shaped” adducts, as established by FT‐Raman spectroscopy and single‐crystal X‐ray diffraction in the case of complex 1? 2 Br2. On the other hand, the reactions of compounds 1 – 3 with molecular I2 provided charge‐transfer (CT) “spoke” adducts, among which the solvated species 3? 2 I2 ? (1?x)I2 ? x CH2Cl2 (x=0.94) and ( 3 )2 ? 7 I2 ? x CH2Cl2, (x=0.66) were structurally characterized. The nature of all of the reaction products was elucidated based on elemental analysis and FT‐Raman spectroscopy and supported by theoretical calculations at the DFT level. 相似文献
76.
(2Z,1S)-1,3-diphenyl-2-propenol (3) is obtained from the chiral 5,6-dihydro-1,4-dithiin 1b in two steps and 60% enantiomeric excess. Combining our previously reported stereoselective double bond formation and this 1,4 asymmetric induction introduces a new route to chiral allylic alcohols with cis geometry from simple aldehydes and methyl ketones. 相似文献
77.
Dr. Alessandro Barge Marina Caporaso Prof. Giancarlo Cravotto Dr. Katia Martina Dr. Paolo Tosco Prof. Silvio Aime Dr. Carla Carrera Dr. Eliana Gianolio Dr. Giorgio Pariani Dr. Davide Corpillo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(36):12086-12092
We report the synthesis and characterization of a water‐soluble, star‐shaped macromolecular platform consisting of eight β‐cyclodextrin (β‐CD) units anchored to the narrower rim of a γ‐CD core through bis(triazolyl)alkyl spacers. The efficient synthetic protocol is based on the microwave (MW)‐promoted Cu‐catalyzed 1,3‐dipolar cycloaddition of CD monoazides to CD monoacetylenes. The ligand‐hosting capability of the construct has been assessed by relaxometric titration and nuclear magnetic relaxation dispersion (NMRD) profiling, which showed it to be good, and this was supported by molecular dynamics simulations. To demonstrate the feasibility of obtaining supramolecular structures with high hosting ability, we designed a dimeric platform, formed by joining two nonamers through the γ‐CD cores through a bis(lithocholic acid) linker. With a view to the potential biological applications, cytotoxicity and extent of binding to human serum albumin were assessed. The properties of this dendrimeric multicarrier make it suitable for pharmaceutical and diagnostic purposes, ranging from targeted drug delivery to molecular imaging. 相似文献
78.
Carla Sirtori Ana Agüera Irene Carra José A. Sanchéz Pérez 《Analytical and bioanalytical chemistry》2014,406(11):2549-2558
This work allowed the identification of major transformation products (TPs) of acetamiprid (ACTM) during Fenton process. Acetamiprid is a chloronicotinoid insecticide widely used around the world for its characteristics (high insecticidal activity, good systemic properties, suitable field stability, etc.). The degradation of the parent molecule and the identification of the main TPs were evaluated in different water matrices (demineralized water and real agro-food industrial wastewater). TPs of acetamiprid generated by Fenton experiments were monitored and identified by liquid chromatography quadrupole time-of-flight tandem mass spectrometry (LC–QTOF–MS/MS). Up to 14 TPs were characterized based on the accurate mass of the molecular ion and fragment ions obtained in both full-scan and MS/MS modes. Most of them were eliminated after 75 min of treatment time in demineralized water. However, in real agro-food industrial wastewater, most of them were eliminated at 90 min of treatment time, demonstrating the influence of the matrix composition on the studied compound degradation. 相似文献
79.
Poly(lactic acid) (PLA) is a biodegradable polymer that has a variety of applications, one of which is as biomaterial in surgery or as functional layers on implants, due to its compatibility with living tissue. This paper reports the possibilities of quantification of poly(lactic acid) (PLA) in a polymer matrix such as poly(methyl methacrylate) (PMMA) by micro Raman spectroscopy (MRS). Blends of amorphous poly(DL‐lactic acid) with poly(methyl methacrylate) were prepared by the procedure of dissolution/precipitation. Thermal properties of the blends such as the glass transition temperature (Tg) were characterized by differential scanning calorimetry (DSC). The PLA/PMMA blends exhibited only a single glass transition region, indicating that this system is miscible. The PLA/PMMA system obeys the Gordon–Taylor equation (Tg versus PLA content). Various concentration ratios of PLA blends were prepared to use as a basis for quantitative analysis by MRS. Intensities of the characteristic bands at 813 cm−1 (νCOC of PMMA) and 873 cm−1 (νC―COO of PLA) were used for the calculation. The calibration graph showed a good linear correlation with an R2 value of 0.9985. On the basis of the calibration curve obtained, the determined content of several PLA/PMMA blends was in good agreement when compared with nominal contents. The limit of detection (LOD) and quantification (LOQ) were calculated by the calibration data set as signal‐to‐noise method. The relative standard deviation of this method was lower than 10% and the accuracy better than 4%. This study demonstrated that Raman spectroscopy provides an alternative non destructive method for quantitative analysis of PLA in a PMMA matrix. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
80.
Paola Taddei Carla Boga Gabriele Micheletti Barbara Ballarin 《Journal of Raman spectroscopy : JRS》2015,46(1):100-108
Raman and IR spectroscopy were used to investigate the changes induced in yak hair keratin by the straightening treatment based on glyoxylic acid. The amino acidic residues that appeared involved in the reaction with glyoxylic acid were serine and lysine; the involvement of the latter was deduced by the spectroscopic detection of iminic species, resulting from the reaction between the aminic group of lysine and the carbonyl group of glyoxylic acid. The reaction with glyoxylic acid induced conformational rearrangements that mainly involved the fibre bulk rather than the cuticle. Changes in the average tyrosine environment and its hydrogen‐bonding state were detected: at increasing glyoxylic acid incorporation, the tyrosine residues appeared more exposed, probably because of H‐bond interactions with the COOH group. The distribution of the disulfide bridge conformation was also affected, although no cleavage of the S–S bond was detected, in agreement with the shiny and healthy appearance of the fibres. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献