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951.
N.F. Santos J.C. Hadler Neto P.J. Iunes S. Guedes S.R. Paulo 《Radiation measurements》2005,39(6):661-664
A device to determine the detection efficiency of CR-39 for alpha particles is presented. A beehive collimator restricted the angle of incidence of alpha particles on a CR-39 sheet, such that the total number of alpha emitters could be determined. This makes it possible to obtain the critical angle of incidence, ΘC, and the maximum angle of incidence resulting in round (diameter ratio <1.100) etch pits, Θmax. In this work, these angles were determined for incidence energies around 7.5 MeV (more specifically 6.1 and 8.8 MeV). 相似文献
952.
Prof. Dr. Norberto Garcia‐Cairasco Prof. Dr. Miguel Moyses‐Neto Flavio Del Vecchio José A. C. Oliveira Francisco L. dos Santos Dr. Olagide W. Castro Dr. Gabriel M. Arisi Prof. Dr. Márcio Dantas Dr. Ruither O. G. Carolino Prof. Dr. Joaquim Coutinho‐Netto Dr. Andre L. A. Dagostin Dr. Marcelo C. A. Rodrigues Prof. Dr. Ricardo M. Leão Dr. Samir A. P. Quintiliano Prof. Dr. Luiz F. Silva Jr. Prof. Dr. Leonardo Gobbo‐Neto Prof. Dr. Norberto P. Lopes 《Angewandte Chemie (International ed. in English)》2013,52(49):13067-13070
953.
Gilberto Maia Fernando C. Maschion Sônia T. Tanimoto Katri Vaik Uno Mäeorg Kaido Tammeveski 《Journal of Solid State Electrochemistry》2007,11(10):1411-1420
The electrochemical reduction of oxygen on glassy carbon (GC) electrodes modified with anthraquinones was studied using cyclic
voltammetry (CV) and the rotating disk electrode (RDE) technique. Two methods were used in surface modification. The first
method comprised immersion of the polished or anodically pretreated GC electrode in a solution containing 9,10-anthraquinone-2-carboxylic
acid (AQ-2-COOH) or its anion (AQ-2-COO−) in dimethylsulfoxide (DMSO) or 9,10-anthraquinone-2-ethanoic acid (AQ-2-CH2COOH) or its anion (AQ-2-CH2COO−) in N,N-dimethylformamide (DMF). Alternatively, the surface of the GC disk was modified by anodic oxidation of AQ-2-COOH or AQ-2-COO− in DMSO or AQ-2-CH2COOH in DMSO or DMF or AQ-2-CH2COO− in DMF. The modified electrodes showed electrocatalytic activity toward oxygen reduction in 0.1 M acetate buffer pH (4.8),
0.1 M phosphate buffer (pH 8) and 0.1 M NaOH. Atomic force microscopy (AFM) examination of the modified electrodes was carried
out and the differences in surface morphology of various modifications were in evidence. 相似文献
954.
Several symmetric N-acyl-N,alpha,alpha-trialkyl glycine amides were synthesised by the Ugi-Passerini four-component reaction and subjected to selective cleavage with trifluoroacetic acid. In almost all cases it was possible to obtain the corresponding N-acyl-N,alpha,alpha-trialkyl and N-acyl-alpha,alpha-dialkyl glycines in fair to good yields directly from the reaction adducts. With some of the bulkier compounds our results show that the selectivity of cleavage is concentration dependent with respect to the acid, which suggests kinetically controlled processes. The isolation of a stable oxazolone as the product of some of the reactions seems to confirm that amide cleavage involves in all cases formation of an oxazolone-type derivative. 相似文献
955.
Hermano Frid Neto 《Bulletin of the Brazilian Mathematical Society》1988,19(1):39-59
In this paper we prove an uniqueness and stability theorem for the solutions of Cauchy problem for the systems $$\frac{\partial }{{\partial t}}u + \sum\limits_{i = 1}^n { \frac{\partial }{{\partial x_i }} } f^i (x,t,u) = g(x,t,u),$$ whereu is a vector function (u 1 (x, t),..., u r (x, t)),f i =(a 1 i (x, t, u),..., a r i (x, t, u)), i=1,...,n, g=(g 1 (x, t, u),...,g r (x, t, u),i G ? n and t≥0. We use the concept of entropy solution introduced by Kruskov and improved by Lax, Dafermos and others autors. We assume that the Jacobian matricesf u i are symmetric and the Hessian(a j i ) uu (i=1,...,n; j=1,...,r) are positive. We obtain uniqueness and stability inL loc 2 within the class of those entropy solutions which satisfy $$\frac{{u_j (---,x_i ,---,t)---u_j (---,y_i ,---,t)}}{{x_i - y_i }} \geqslant - K(t),$$ (i=1,...,n; j=1,...,r) for (?,x i ,?,t), (?,y i ,?,t) on a compact setD ? ? n x (0, ∞) and a functionK(t)∈L loc 1 ([0, ∞)) depending onD. Here we denote by (?,x i ,?,t) and (?,y i ,?,t) two points whose coordinates only differ in thei-th space variable. At the end we relax the hypotheses of symmetry and convexity on the system and give a theorem of uniqueness and stability for entropy solutions which are locally Lipschitz continuous on a strip ? n x [0,T]. 相似文献
956.
Brenno A. DaSilveira Neto Gunter Ebeling Valentim E.U. Costa Jairton Dupont 《Tetrahedron》2005,61(46):10975-10982
The reaction of 4,7-dibromo-2,1,3-benzothiadiazole with arylboronic acids (phenyl, 1-naphthyl, 4-methoxyphenyl, 4-chlorophenyl and 4-trifluoromethylphenyl) in the presence of catalytic amounts of a NCP-pincer palladacycle affords photoluminescent π-extended 4,7-diaryl-2,1,3-benzothiadiazoles 4a-e in high yields. These 4,7-diaryl-2,1,3-benzothiadiazoles exhibit high fluorescent quantum yields, high electron affinities and adequate band gap values for testing as OLEDs. The 4,7-bis-naphthyl-2,1,3-benzothiadiazole 4b presents two different lifetimes (bi-exponential decay) due to the presence of two atropisomers. The Sonogashira coupling reaction of 4,7-diethynyl-2,1,3-benzothiadiazole 6 with the corresponding halo-aryl compounds (iodobenzene, 1-bromonaphthalene, 4-iodoanisole, 4-bromo-N,N-dimethylaniline and 2-bromopyridine) afforded the photoluminescent π-extended 4,7-bis-alkynylaryl-2,1,3-benzothiadiazoles 7a-e, also in high yields. These 4,7-diethynyl-2,1,3-benzothiadiazoles also present high fluorescent quantum yields, high electron affinities and adequate band gap values for testing as OLEDs. The 4,7-disubstituted-2,1,3-benzothiadiazoles 4a-e and 7a-e exhibit different electrochemical behavior. The presence of two ethynyl spacers in 2,1,3-benzothiadiazoles 7a-e shifts the reduction potentials to less cathodic values and also results in two well-defined and distinct reduction processes. 相似文献
957.
Castro SL Neto OD Santos SR Medeiros EP Lima RA Martins VL Araújo MC Josué CC Korn M 《Journal of AOAC International》2005,88(4):1064-1068
A flow-injection biamperometric method for determination of pantoprazole (PTZ) in pharmaceutical tablets is reported for the first time. The reversible redox couples Fe3+/Fe2+, Fe(CN)6(3-)/Fe(CN)6(4-), Ce4+/Ce3+, VO3(-)NO2+, and I2/I- were tested as indicating redox systems for biamperometric determination of PTZ in a flow-injection assembly with optimized flow parameters. The best results were obtained using V03(-)NO2+, which showed to be a selective and sensitive biamperometric indicating system for PTZ even in the presence of excipients and antioxidants that typically are found in drugs. The analytical graph was linear (r = 0.99945) in the range from 10 to 100 mg/L using 25 mmol/L VO3(-) as the reagent and water as the carrier stream and applying 100 mV between the 2 platinum wire electrodes. The limits of detection and quantitation were 200 and 667 microg/L, respectively, with a sensibility of calibration of 22.6 mV/mg/L. The proposed method was successfully applied to determine PTZ in commercial pharmaceutical tablets with a mean relative error of 1.60% (n = 5) and mean relative standard deviation of 3.10%. Recoveries close to 100% showed good agreement between the expected amount of PTZ in tablets (40 mg) and the results found by the application of the proposed method and demonstrated that the formulations used in the tablet compositions do not interfere in the PTZ analysis. The system had good stability, with a relative standard deviation of 3.80% for 9 sequential injections of a 60 mg/L PTZ solution. A sampling rate of about 100 samples/h was obtained. 相似文献
958.
Gomes Constantino M da Silva Filho LC Neto AC Gomes Heleno VC da Silva GV Callegari Lopes JL 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(1-2):171-176
A detailed NMR analysis with total assignment of (1)H and (13)C NMR data for the endo and the exo adducts, obtained by Diels-Alder reaction between 2-cyclohexenone and cyclopentadiene, is described. The unequivocal assignment of the endo and exo structures was performed by (1)H and (13)C NMR. These assignments were supported by theoretical chemical shift calculations at GIAO/HF level using 6-311 + g(2d, p) from optimized structures at the B3LYP/6-31g(d) level. 相似文献
959.
A. A. M. Lira D. M. A. Nanclares A. Federman Neto J. M. Marchetti 《Journal of Thermal Analysis and Calorimetry》2007,87(3):899-903
Chitosan microparticles were prepared with
the purpose of incorporating all-trans
retinoic acid (ATRA). Morphology, drug content, release behavior and the interaction
between chitosan and ATRA were investigated. Chitosan microparticles presented
irregular and rough surface and drug content of 47±3%. The results
of DSC and IR spectroscopy demonstrated interaction between drug and polymer
resulting from retinoate or retinoamide formation. The drug release study
showed that approximately 90% of drug was not released from microparticles
until the end of experiment (48 h). That release behavior was probably due
to the strong drug–polymer interaction and the more compact network
of microparticles formed. 相似文献
960.
Ferrara Maria Antonieta Bon Elba P. S. Neto Julio Silva Araujo 《Applied biochemistry and biotechnology》2002,98(1-9):289-300
The possibility of using two by-products of the sugar cane industry, molasses and bagasse steam explosion liquor (SEL), for
lignin peroxidase (LiP) production by Phanerochaete chrysosporium was investigated. For comparison, the fungus was initially cultivated in synthetic media containing either glucose, sucrose,
xylose, or xylan as sole carbon sources. The effect of veratryl alcohol (VA) was also investigated in relation to the enzyme
activity levels. Results showed that sucrose was not metabolized by this fungus, which precluded the use of molasses as a
carbon source. Glucose, xylose, and xylan promoted equivalent cell growth. Enzyme levels in the absence of VA were lower than
28 UI/L and in the presence of VA reached 109 IU/L with glucose and 85 IU/L with xylose or xylan. SEL was adequate for P. chrysosporium LiP production as LiP activity reached 90 IU/L. When VA was added to this medium, enzyme concentration increased to 155 IU/L. 相似文献