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561.
Gangfeng Cai Morton H. Litt 《Journal of polymer science. Part A, Polymer chemistry》1992,30(4):659-669
Two series of random copolymers of 10-(pentamethyl disiloxanyl) decyl oxazoline ( Si ) with undecyl ( U ) (four copolymer compositions) and nonyl ( N ) (eight copolymer compositions) oxazolines over the whole composition range, with a total degree of polymerization of about 100, were studied by DSC and wide angle X-ray diffraction. All the polymers are crystalline. For the N/Si copolymers, the melting points, normalized ΔH and ΔS of fusion are almost constant in a broad range of copolymer composition from 10 to 65 mol % of Si . The rationale for this behavior is that the copolymers crystallize two dimensionally, with the crystalline polymethylene plates separated by the bulky flexible pentamethyl disiloxanyl ( P ) groups. In this range, increasing Si only increases the distance between the plates. With more than 65 mol % Si , the bulky P groups interfere with the packing of the alkyl chains and change the crystallization behavior; the polymers show disordered packing as demonstrated by their X-ray patterns and extremely low ΔH. In the U/Si copolymers, since the undecyl side chain has one more carbon than the decyl group to which the P group is attached, the P groups interfere much more strongly with the packing of the side chains than in the N/Si polymers. The copolymer melting points uniformly decrease as the concentration of Si increases. The plateau on the plot of normalized ΔH versus polymer composition is only from 10 to 50 mol % of Si . The average long spacings of the annealed polymers increase linearly from 24 Å ( N/Si polymers) or 28 Å ( U/Si polymers) to 34.1 Å with the increase of Si up to 50%. With more than 50% Si , the polymers have an identical lamellar thicknesses of 34 Å, within the experimental error. Copolymers with less than 75 mol % of Si can crystallize from hexadecane solutions forming gels down to polymer concentrations of 2-3 wt %. The long spacings of the gels are almost identical with those of the pure crystalline polymers and independent of the polymer/solvent ratios. When hexamethyl disiloxane is added to the solutions, it can intercalate and the resulting crystalline gels have long spacings larger than those found in the absence of siloxane. 相似文献
562.
N-2,4-Dinitrobenzenesulfenylbenzimidazoles exhibit substantial barriers to torsion about the sulfur-nitrogen bond ( 19 kcal/mole). 相似文献
563.
Morton E. Gurtin Paolo Podio-Guidugli 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1992,43(1):181-190
Force and moment balance laws are derived for structured continua. The approach consists in the use of two hypotheses: the availability of a microscope, mathematized by the introduction of a scale parameter; the existence of total and fine power expenses and the invariance of the corresponding power functionals in the limit 0+.
Sommario Vengono dedotte leggi di bilancio delle forze e dei momenti per continui con struttura. L'approccio consiste nell'uso di due ipotesi: la disponibilità di un microscopio, resa matematicamente tramite l'introduzione di un parametro di scala; l'esistenza di forme della potenza spesa totale e fine, e l'invarianza di queste forme per 0+.相似文献
564.
A cell-vertex finite volume approximation of elliptic convection-dominated diffusion equations is considered in two dimensions. The scheme is shown to be stable and second-order convergent in a mesh-dependent -norm.
565.
Morton A. Golub Mark L. Rosenberg 《Journal of polymer science. Part A, Polymer chemistry》1980,18(8):2543-2560
A study was made of the microstructural changes that occur in ultraviolet irradiation under vacuum of thin films of 1,2-poly(cis-1,4-hexadiene) (CHD), 1,2-poly(trans-1,4-hexadiene) (THD), 1,2-poly(trans-1,3-pentadiene) (TPD), equibinary (1,2,-1,4) polybutadiene (EB), and equibinary (3,4-1,4) polyisoprene (EI). These polymers—all containing pendant double bonds—undergo important photoinduced loss of unsaturation, presumably through cyclization of the double bonds, by analogy to the previously reported photocyclization of 1,2-polybutadiene (VB) and 3,4-polyisoprene (VI)films. For the equibinary polymers, which contain internal as well as external (or pendant) double bonds, the loss of unsaturation is considered to involve photocyclization of 1,2-1,4 and 1,2-1,2 dyads in EB and of 3,4-1,4 and 3,4-3,4 dyads in EI. Accompanying thecyclization process in CHD, THD, and TPD is a direct photochemical cis-trans isomerization of ? CH?CH? double bonds analogous to that originally noted for 1,4-polybutadiene. The photorearrangements in the above polymers with pendant double bonds were compared to the corresponding thermally induced rearrangements reported previoulsy;for VB and VI, in particular, the thermal, photo-and radiation-induced cycli-zations were found to be very similar, possibly having a common nonradical, nonionic mechanism involving excited double bonds. 相似文献
566.
The relative rates of plasma homo- and Copolymerizations of ethylene, vinyl fluoride, vinylidene fluoride, trifluoroethylene and tetrafluoroethylene (VF
x
, x = 0–4, respectively) were determined in an rf, capacitively coupled, tubular reactor with external electrodes using identical plasma parameters. The deposition rates for VF
x
(x = 1–3) and 20 different monomer blends, when plotted versus the F/C ratios of the monomers or monomer blends, followed a concave-downward curve situated above the straight-line joining the rates for VF0 and VF4. The deposition rates for VF
m
/VF
n
blends (m = 3 or 4; n = 0–2) likewise yielded concave-downward curves situated above the straight lines joining the rates for the respective monomers; the rates for VF
m
/VF
n
blends (m = 0 or 1; n = 1 or 2) yielded concave-upward curves situated below the straight lines joining the rates for the respective monomers; while the rates for VF3/VF4 blends fell along the straight line joining the rates for VF3 and VF4. The mechanisms for plasma (co) polymerizations of VF
x
monomers responsible for the wide range of relative deposition rates remain to be elucidated. 相似文献
567.
Y. Amimoto R.N. Haszeldine M. Maruta W.D. Morton R. Rowland 《Journal of fluorine chemistry》1980,16(6):552
Routes to perflouroallyl chloride, CF2:CF.CF2Cl, and to -and -1-chloro-hexafluoro-2-trifluoromethyl(but-2-ene), (CF2Cl)(CF3)C:CF.CF3 are reported, and their susceptibility to attack by nucleophiles discussed; the allylic chlorine atoms in these olefins are the controlling factor in determining the products obtained.The conversion of 3-chloropentafluoropropene into a series of perfluoroallyl derivatives of general formula R.CF2.CF:CF2 [R = (CF3)3C-, CF3O-, C6F5-, l-, MeO-, etc.] is described, and the further chemistry of 3-chloropentafluoropropene and its derivatives outlined.Water reacts rapidly with (CF2Cl)(CF3)C:CF.CF3 to give CF2:C(CF3).CFCl.CF3 or CF3.CO.CH2.CF3. Methanol affords CF2:C(CF3).CFOMe.CF3 and (MeOCF2)(CF3)C:CF.CF3 as initial products, with subsequent secondary products such as CF3.CFOMe.CH(CF3).CF2OMe, (CF3)(MeO)C:C(CF3).CF3OMe, MeO.CF:C(CF3).CFOMe.CF3, (CF3)(MeO)CF.CH(CF3).CO2Me, and (CF3)(MeO)C:C(CF3).CO2Me. The influence of allylic chlorine and of reaction time on the formation of these products, and mechanistic pathways for their formation are considered. 相似文献
568.
Summary Reaction loops may be used in a gas Chromatographic system to help determine the chemical structure of compounds. Loops that retain or detain compounds with a certain functional group subtract these compounds and thereby indicate the presence of the functional group in unknown compounds. The performance of loops in subtracting alcohols, acids, aldehydes, ketones, epoxides, and a variety of other compounds was studied to amplify the usefulness of this technique. A simplified version of carbon-skeleton chromatography was also shown to be useful for analysis of polar or high molecular weight compounds (C12 or higher).
Zusammenfassung Reaktionsschleifen können sich in gaschromatographischen Geräten für die Ermittlung der chemischen Struktur von Verbindungen als nützlich erweisen. In diesen Schleifen werden Verbindungen mit einer bestimmten funktionellen Gruppe zurückgehalten, deren Vorhandensein in unbekannten Verbindungen damit indiziert wird. Die Wirkungsweise solcher Schleifen bei der Entfernung von Alkoholen, Säuren, Aldehyden, Ketonen, Epoxiden und verschiedenen anderen Verbindungen wurde studiert, um die Brauchbarkeit dieser Methodik zu erweitern. Eine einfachere Form der Kohlenwasserstoff-Chromatographie hat sich gleichfalls als wertvoll für die Analyse polarer oder Verbindungen mit hohem Molekulargewicht (C12 oder höher) erwiesen.相似文献
569.
Starting from a bisprotected ferrocene-1,2,3-triscarbaldehyde, Ohira-alkynylation and Pd-catalyzed protection of the free alkyne with 4-iodotoluene leads to a ferrocene in which one Cp-ring is 1,2,3-substituted by two acetal rings (1,2-position) and an internal alkyne. Metalation of the ferrocene nucleus with sec-BuLi, workup with DMF and reduction with LiAlH4 leads to a 1,2,3,4-tetrasubstituted ferrocene carrying a hydroxymethyl group. The acetal groups are removed by para-toluenesulfonic acid and the aldehyde groups are converted into arylalkynes. A second metalation followed by workup with DMF furnishes a 1,2,3,4,5-pentasubstituted ferrocenecarbaldehyde. The aldehyde is transformed into an alkyne by the Ohira method and converted to an internal alkyne by Pd-catalyzed reaction with 4-iodotoluene. The sequence gives a 1,2,3,4,5-pentasubstituted ferrocene derivative with four alkyne groups and one hydroxymethyl group. Airless Marko oxidation of the alcohol is followed by another Ohira alkynylation. Pd-catalyzed arylation finishes the reaction sequence to give the symmetrical 1,2,3,4,5-pentakis(4′-tolylethynyl)ferrocene, the first pentaethynylferrocene derivative. A second, similar route was explored that furnished 1,2,3,4,5-pentakis(4′-butylphenylethynyl)ferrocene and its butadiyne-bridged dimer. 相似文献
570.
E. Söderbäck K. Masaki O. Hirabayashi G. S. Forbes J. H. Faull A. Hemingway E. L. Arnow C. Morton W. Hiltner N. J. King H. Moser E. Raub W. Stein C. del Fresno E. Mairlot M. Abribar P. Rumpf M. Auméras J. Marcon W. A. Kargin M. I. Ussanowitsch O. Stelling 《Analytical and bioanalytical chemistry》1934,97(5-6):195-199