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81.
An algebraic model was derived for obtaining complex pressure swing adsorption (PSA) cycle schedules. This new approach involves
a priori specifying the cycle steps, their sequence and any constraints, and then solving a set of analytical equations. The solution
identifies all the cycle schedules for a given number of beds, the minimum number of beds required to operate the specified
cycle step sequence, the minimum number and location of idle steps to ensure alignment of coupled cycle steps, and a simple
screening technique to aid in identifying the best performing cycles that deserve further examination. The methodology was
tested successfully against 10, 12 and 16 bed PSA systems in the literature that all utilized the same 13 step cycle sequence
that has four pressure equalization steps. It completely resolved all the corresponding cycle schedules for these 13 step
multi-bed PSA systems with ease, and showed that the number of cycle schedules was hundreds to thousands of times greater
than the few ever reported in the literature for each one. Overall, this new methodology for complex PSA cycle scheduling
can be applied to any number of cycle steps, any corresponding cycle step sequence, and any number of constraints, with the
outcome being the complete set of cycle schedules for any number of beds greater than or equal to the minimum number it determines. 相似文献
82.
A rapid, easy, and simple spectrophotometric method was developed for the estimation of total alkaloids precipitated by Dragendorff's reagent (DR) in plant materials. It is based on the formation of yellow bismuth complex in nitric acid medium with thiourea. The yellow-colored complex formed obeys Lambert-Beer's law in the concentration range of 0.06-50 microg/mL with lambdamax at 435 nm. Using this method, the alkaloidal percentage of certain alkaloids (ajamalicine, papaverine, cinchonine, piperine, berberine) and some plant materials containing alkaloids (Berberis aristata, Solanum nigrum, and Piper longum) were determined. The method was compared with other methods. It can be used for routine analysis of commercial samples by industries dealing with herbal drugs for standardization of plant materials containing alkaloids and for alkaloid-containing pharmaceutical products. 相似文献
83.
Umesh N. Tripathi Ghanshyam Srivastava Ram C. Mehrotra 《Transition Metal Chemistry》1994,19(6):564-566
Summary Solids of the stoichiometric formulae [Fe{S2P(OPr-n)2}3] and [Fe{S2PO2G}3] (G = —CH2CMe2CH2—, CMe2–CMe2— or —CH2CH2CHMe—) are precipitated from the reactions of FeCl3 with ammonium dithiophosphates in water. Soluble complexes of the type [Fe{S2PO2G}2], formed by the reactions of FeCl2 with NH4[{S2PO2G}] in MeOH, can be extracted with benzene. Adducts of the types [Fe{S2PO2G}2L] and [Fe{S2PO2G}2(PPh3)2] are formed by the reaction of [Fe{S2PO2G}2] with L (L = 2,2-bipyridyl or 1,10-phenanthroline) and PPh3, respectively. All the compounds have been characterized by i.r. and u.v.-vis. spectroscopy and magnetic studies.This paper is dedicated to the late Dr. G. Srivastava, Associate Professor, Department of Chemistry, Rajasthan University, Jaipur. 相似文献
84.
Barium zirconyl oxalate hydrate (BZO) is prepared and characterised by chemical analysis and IR spectral studies. Thermal decomposition studies have been made using TG and DTA techniques. The decomposition has been found to proceed through four steps. The first step involves a two-stage dehydration (100–190°C, 190–260°C) and the second step the decomposition of oxalate (260–460°C). The third step involves the evolution of carbon monoxide present in the lattice and partial decomposition of carbonate. The fourth step involves the final stage decomposition of carbonate (760–920°C) giving barium zirconate as an end product. The identification of compounds at various stages has been done by IR spectra. The X-ray diffraction pattern of BZO confirms that it is a crystalline compound. 相似文献
85.
Sunil Ahire Ajay Chaudhari Milind Lokhande Suresh C. Mehrotra 《Journal of solution chemistry》1998,27(11):993-1008
Frequency spectra of the complex permittivity for pyridine–amide binary mixtures have been determined over the frequency range 10 MHz to 10 GHz, at 5, 15, 25, and 40°C, using the time–domain reflectometry method, for 11 compositions of each pyridine–amide system, e.g., formamide, N-methylformamide, and N,N-dimethylformamide. The relaxation in these systems can be described by a single relaxation time using the Debye model. The static dielectric constant, relaxation time, the corresponding excess dielectric properties, Kirkwood correlation factor, and molar activation energy of the mixtures have been determined. The excess permittivity is found to be positive in the amide-rich region and negative in the pyridine-rich region. The excess inverse relaxation time is negative, except in the pyridine-rich region. The static dielectric constants for the mixtures have been fitted with the modified Bruggeman model. The temperature-dependent relaxation times show the expected Arrhenius behavior. 相似文献
86.
Suman Mehrotra J. P. Barthwal A. K. Saxena K. P. Bhargava S. S. Parmar 《Journal of heterocyclic chemistry》1981,18(6):1157-1159
Twelve 6-substituted-2-(1′-mercaptoacetyl-3′-arylurea)-3-phenyl-4-quinazolones were synthesized by condensation of 6-substituted anthranilic acids and aryl isothiocyanates followed by reaction with chloroacetyl arylurea. These compounds were characterized by their sharp melting points and elemental analyses. All compounds were evaluated for their enzyme inhibitory activity. It was found that all substituted quinazolones at a final concentration of 2 × 10?4 M inhibited in vitro monoamine oxidase and succinate dehydrogenase activity of rat brain homogenates and the degree of inhibition ranged from 11–77% and 25–53%, respectively. 相似文献
87.
Using the picosecond time domain reflectometry method, dielectric relaxation measurements for 13 ethylene glycol (EG)-water mixtures have been studied from 0 to 40°C. The dielectric relaxations in the mixtures show a Debye-type behavior, whereas the relaxation in pure EG can be described by the Cole-Cole model. The static dielectric constant 0, the relaxation time and the dielectric constant at high frequency have also been determined at various temperatures. The dielectric relaxation data suggests that there is no tendency to form hydrogen bonds with the addition of water to EG unlike other alcoholic systems but this tendency becomes increasingly important with decreasing temperature. The activation energy decreases with increased water content in the mixture as expected. 相似文献
88.
Synthesis and physico-chemical studies of some polynuclear mixed carboxylate complexes of nickel(II)
B. P. Baranwal G. K. Parashar R. C. Mehrotra 《Monatshefte für Chemie / Chemical Monthly》1980,111(5):1203-1211
A number of polynuclear mixed carboxylates of nickel(II) with the general composition [Ni(OOCCH3)2–n
(OOCR)
n
]
x
(whereR=C13H27, C15H31, C17H35 and C21H43 andn=1 or 2) have been synthesized by the transacylation reactions of anhydrous nickel acetate with higher carboxylic acids in refluxing toluene. On recrystallization from benzene-alcohol mixtures, mono-alcoholate complexes, Ni(OOCCH3)2–n
(OOCR)
n
·ROH (whereR=CH3 and C2H5) have been isolated. All these derivatives have been characterized by the molecular weight determinations, infra-red and electronic reflectance spectra and magnetic susceptibility measurements.
Synthese und Eigenschaften einiger gemischter Carboxylat-Komplexe von Nickel(II)
Zusammenfassung Komplexe des Typs [Ni(OOCCH3)2–n (OOCR) n ] x (mitR=C13H27, C15H31, C17H35 und C21H43,n=1 oder 2) wurden aus wasserfreiem Nickelacetat mit höheren Carbonsäuren in siedendem Toluol erhalten. Bei der Kristallisation aus Benzol-Alkohol-Mischungen wurden Monoalkoholate Ni(OOCCH3)2–n (OOCR) n ·ROH (mitR=CH3 und C2H5) isoliert. Die Charakterisierung der Komplexe erfolgte mittels Molekulargewichtsbestimmung, Infrarot- und Elektronenspektren und der Messung der magnetischen Susceptibilität.相似文献
89.
Summary The kinetics of OsO4-catalysed oxidation of cyclopentanol, cyclohexanol and cyclooctanol by alkaline hexacyanoferrate(III) have been studied at low [OH–] so that the equilibrium between alcohol and alkoxide ion is not unduly shifted towards the latter. The reaction shows a first-order dependence in [OH–]. The order of the reaction with respect to cycloalcohol is fractional, indicating the formation of an intermediate complex with OsVIII since the order with respect to hexacyanoferrate(III) ion is zero. The order with respect to OsVIII may be expressed by the equation kobs=a+b[OsVIII]. The analysis of the rate data indicates a significant degree of complex formation between [OsO3(OH)3]– and ROH. It was found that the bimolecular rate constant k for the redox reaction between complex and OH–k1, the forward rate constant for the formation of alkoxide ion. The activation parameters of these rate constants are reported. 相似文献
90.
Five-, six-, and seven-coordinate volatile butyltin(IV) heterobimetallic derivatives, respectively of the types, [BuSn{(μ-OPri)2Al(OPri)2}Cl2] (1), [BuSn{(μ-OPri)2Al(OPri)2}2Cl] (2), and BuSn{(μ-OPri)2M(OPri)x − 2}3 (3:M = Al (x = 4); 4:M = Ga (x = 4); 5:M = Nb (x = 6)) have been synthesized by the reactions of BuSnCl3 with potassium tetraisopropoxoaluminate in 1:1, 1:2, and 1:3 molar ratios. Replacement reactions of chloride in (1) and (2) with appropriate alkoxometallate (tetraisopropoxoaluminate, tetraisopropoxogallate, or hexaisopropoxoniobate) ligands result in the formation of novel BuSn(IV) heterotri- and tetra-metallic derivatives. All of these derivatives have been characterized by elemental analyses, molecular weight measurements, and spectroscopic (IR, 1H, 27Al, and 119Sn NMR) studies. Based on these studies, plausible structures for the new derivatives involving bidentate ligation of the alkoxometallate ligands have been suggested. 相似文献