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81.
Sonia Milln Victor Snchez Luz Alicia Fucugauchi Yasuo Ito Yoneho Tabata 《Journal of Polymer Science.Polymer Physics》1992,30(1):1-9
The positron lifetime measurement technique was applied to analyze the structural changes occurring in solid-state polymerization of acrylamide and trioxane. Positronium (Ps) parameters, τ2 and I2, which show a marked change as a function of the γ-ray irradiation dose, signaled the presence of three clearly defined stages in the polymerization process: initiation, propagation, and saturation. The initial increase in τ2, may very well be the result of efficient trapping of Ps in vacancies created around the polymer nuclei. The complicated behavior of I2 may be explained as a chemical reaction between Ps precursors and the radiolysis products of this polymerization process. 相似文献
82.
González-Sánchez L Gómez-Carrasco S Aguado A Paniagua M Hernández ML Alvariño JM Roncero O 《The Journal of chemical physics》2004,121(1):309-320
In this work a simulation of the OHF(-) photodetachment spectrum is performed in a three-dimensional potential energy surface recently developed for OHF((3)A(")). The ground (2)A(') state potential of the anion is calculated in three dimensions based on accurate ab initio calculations and the reaction dynamics is studied using a wave packet method. The calculated spectrum shows a sequence of bands associated to vibrational HF(v) up to v=3. Each band is formed by a continuous spectrum and resonant structures. These resonances are associated to the OH-F channel well of the (3)A(") PES, in which fragmentation occurs through vibrational predissociation. Above the OH(v=0) threshold a new resonant pattern appears corresponding to heavy-light-heavy resonances. Special attention is paid to the assignment of these resonances because they mediate the reaction dynamics in the OH+F collision at low kinetic energies. The sequence of bands is in rather good agreement with that appearing in the experimental spectrum, especially at higher electron kinetic energies. At low kinetic energies, however, some other electronic states may contribute. The resonance structures might be washed out by the rotational average and the relatively low energy resolution of the experiment. 相似文献
83.
Blay G Cardona L Collado AM García B Morcillo V Pedro JR 《The Journal of organic chemistry》2004,69(21):7294-7302
The synthesis of the spirovetivane sesquiterpenes (+)-anhydro-beta-rotunol and all the diastereomers of 6,11-spirovetivadiene in enantiomerically pure form has been achieved starting from santonin. The key step is the silicon-guided acid-promoted rearrangement of a 1-trimethylsilyl-4,5-epoxyeudesmane prepared from santonin in several steps involving lactone reductive opening, conjugate addition of TMSLi-CuCN, deoxygenation of a carbonyl group, and epoxidation. Rearrangement of the epoxide gave a spiro[4,5]decanediol which was used as a synthetic intermediate. From this compound, (+)-anhydro-beta-rotunol was prepared after elimination of the primary hydroxyl group in the side chain, followed by allylic oxidation at C8 and elimination of the tertiary hydroxyl group in the cyclohexane ring. On the other hand, elimination of the hydroxyl group in the side chain and reduction of the hydroxyl in the cyclohexane ring gave (-)-premnaspirodiene and (-)-hinesene. The synthesis of the rest of the diastereomers for these compounds required formal inversion of the C5 spiro carbon. The synthesis of these compounds showed that the structure of (-)-agarospirene isolated from Scapania sp. was erroneously assigned, and it has been corrected to be identical to that of (-)-hinesene. 相似文献
84.
85.
M. Luz Godino-Salido Rafael López-Garzón Paloma Arranz-Mascarós M. Dolores Gutiérrez-Valero Antonio Santiago-Medina Javier García-Martín 《Polyhedron》2009,28(17):3781-3787
The retention of Co2+, Ni2+ and Cu2+ metal ions from aqueous solution, on a functionalized hybrid material obtained by the anchorage of N-(4-amino-1,6-dihydro-1-methyl-5-nitroso-6-oxopyrimidin-2-yl)-N′-[bis(2-aminoethyl)] ethylenediamine ligand on a low-functionalized activated carbon, at pH 4.5 has been studied. The adsorption isotherms fit the Langmuir equation and the calculated maximum adsorption capacities were compared to those obtained by using the un-functionalized activated carbon as well as to other analogous hybrid materials as adsorbent of the same metal ions. These studies were carried out by rationalizing the resulting adsorption data regarding the stability constant values of the complexes formed by the three metal ions with the free tri-amine function of the ligand. The results demonstrate that the adsorption capacities of the activated carbon–ligand hybrid material towards the three metal-ions studied correlated with the stabilities of the tri-amine-metal-ion bonds formed during the adsorption processes. 相似文献
86.
Silveira PC da Silva LA Tromm PT Scheffer Dda L de Souza CT Pinho RA 《Ultrasonics》2012,52(5):650-654
Introduction
The aim of the study was to evaluate the effects of TPU together with DMSO on oxidative stress parameters after eccentric exercise.Methods
Thirty and six animals were divided in control; eccentric exercise (EE); EE + saline gel 0.9%; EE + TPU 0.8 W/cm2; EE + DMSO gel; EE + TPU + DMSO gel and submitted to one 90-min downhill run (1.0 km h−1). TPU was used 2, 12, 24, 46 h after exercise session and 48 h after the animals were killed and the gastrocnemius muscles were surgically removed. Production of superoxide anion, creatine kinase (CK) levels, lipoperoxidation, carbonylation, and antioxidants enzymes were analyzed.Results
Showed that TPU and gel-DMSO improved muscle healing. Moreover, superoxide anion production, TBARS level and protein carbonyls levels, superoxide dismutase and catalase activity were all decreased in the group TPU plus gel-DMSO.Discussion
Our results show that DMSO is effective in the reduction of the muscular lesion and in the oxidative stress after eccentric exercise only when used with TPU. 相似文献87.
Simultaneous Determination of Caffeine,Ibuprofen, and Paracetamol by Flow‐injection Analysis with Multiple‐pulse Amperometric Detection on Boron‐doped Diamond Electrode 下载免费PDF全文
Sandro C. Chaves Priscila N. C. Aguiar Lívia M. F. C. Torres Eric S. Gil Rita C. S. Luz Flávio S. Damos Rodrigo A. A. Munoz Eduardo M. Richter Wallans T. P. dos Santos 《Electroanalysis》2015,27(12):2785-2791
This work presents a simple, fast and low‐cost method for the simultaneous determination of three drugs by flow‐injection analysis with multiple‐pulse amperometric (MPA) detection using a wall‐jet flow cell with a boron‐doped diamond electrode. The amperometric determination of caffeine (CF), ibuprofen (IB) and paracetamol (PC) was performed by the application of a four‐potential waveform using the MPA technique. PC is oxidized at E1 (1.20 V/70 ms) and thus selectively detected; PC and CF are oxidized at E2 (1.49 V/40 ms); PC, CF and IB are oxidized at E3 (1.70 V/70 ms); and E4 (1.80 V/100 ms) is applied for electrode cleaning. The subtraction of currents obtained at the different potentials did not provide accurate determinations of CF and IB, thus it was required to investigate correction factors to determine CF and IB without the interference from PC and CF using the respective amperometric signals obtained at E2 and E3. The proposed method was successfully applied for the determination of three drugs in pharmaceutical samples with low generation of residues and a high analytical frequency (150 h?1) in comparison with HPLC‐DAD method. 相似文献
88.
M.Luz Gallego Mercedes Cano JosA. Campo JosV. Heras Elena Pinilla M.Rosario Torres 《Helvetica chimica acta》2005,88(9):2433-2440
The structures of [Pd(η3‐C3H5)(HpzR2)2](BF4) (HpzR2=Hpzbp2=3,5‐bis(4‐butoxyphenyl)‐1H‐pyrazole, 1 ; HpzR2=HpzNO2=3,5‐dimethyl‐4‐nitro‐1H‐pyrazole=Hdmnpz, 2 ) and [Ag(HpzR2)2](A) (HpzR2=Hpzbp2, A= , 3 ; HpzR2=HpzNO2, A= , 4 ) were comparatively analyzed to determine the factors responsible for polymeric assemblies. In all cases, the H‐bonding interactions between the pyrazole moieties and the appropriate counterion and, in particular, the orientation of the NH groups of the pyrazole ligands are determinant of one‐dimensional polymeric arrays. In this context, the new compound [Ag(HpzNO2)2](NO3) ( 5 ) was synthesized and its structure analyzed by X‐ray diffraction (Fig. 4). The HpzNO2 serves as N‐monodentate ligand, which coordinates to the AgI center through its pyrazole N‐atom giving rise to an almost linear N Ag N geometry. The planar NO counterion bridges two adjacent AgI centers to form a one‐dimensional zigzag‐shaped chain which is also supported by the presence of N H⋅⋅⋅O bonds between the pyrazole NH group of adjacent cationic entities and the remaining O‐atom of the bridging NO (Fig. 5). The chains are further extended to a two‐dimensional layer‐like structure through additional Ag⋅⋅⋅O interactions involving the NO2 substituents at the pyrazole ligands (Fig. 6). 相似文献
89.
Carrillo LD Krishnamoorthy L Mahal LK 《Journal of the American Chemical Society》2006,128(46):14768-14769
beta-O-N-Acetyl-d-glucosamine (O-GlcNAc) is a dynamic carbohydrate modification that is involved in cell signaling and has been implicated in a variety of disease states, including Alzheimer's and type-II diabetes. Despite the importance of this modification, little is known about the spatial and temporal localization of O-GlcNAc during signaling. This is due to the lack of methods for the study of O-GlcNAc in living cell systems. Herein we report the first genetically encoded FRET-based sensor for the detection of O-GlcNAc dynamics in live mammalian cells. 相似文献
90.
Miguel Espinosa Prof. Dr. Gonzalo Blay Prof. Dr. Luz Cardona Prof. Dr. José R. Pedro 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(44):14861-14866
The asymmetric conjugate addition of malonate esters to α,β‐unsaturated N‐sulfonyl imines is catalyzed by PyBOX/La(OTf)3 complexes in the presence of 4 Å MS. The reaction gives the corresponding E enamines bearing a stereogenic center at the allylic position with good yields and enantiomeric ratios up to 97:3. This reaction provides a synthetic entry to chiral δ‐aminoesters and piperidones. 相似文献