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991.
Taís Vanessa Gabbay Alves Eraldo José Madureira Tavares Fauze Ahmad Aouada Charles Alberto Brito Negrão Marcos Enê Chaves Oliveira Anivaldo Pereira Duarte Júnior Carlos Emmerson Ferreira da Costa José Otávio Carréra Silva Júnior Roseane Maria Ribeiro Costa 《Journal of Thermal Analysis and Calorimetry》2011,106(3):717-724
This paper reports the thermal characterization of polyacrylamide-co-methylcellulose hydrogels and the constituent monomers (acrylamide and methylcellulose). Polymeric materials can be used
to produce hydrogels, which can be natural, synthetic, or a mixture. The hydrogels described here were obtained by free radical
polymerization, in the presence of N,N′-methylene-bis-acrylamide as a cross-linker agent. Four acrylamide concentrations were used for the synthesis of hydrogels:
3.6, 7.2, 14.7, and 21.7% (w/v). The materials so obtained were analyzed by TG, DTG, DSC, and FT-IR. The TG curves of acrylamide
and methylcellulose showed three mass loss events. In DSC curves, the acrylamide exhibited one melting peak at 84.5 °C, and
methylcellulose indicated one exothermic event. Nevertheless, acrylamide was considered more stable than methylcellulose.
The TG curves of the hydrogels exhibited three mass loss events, and on the DSC curves, three endothermic events were observed.
It was verified that the different acrylamide proportions influenced the thermic behavior of hydrogels, and that the authors
considered the 7.2% hydrogel a promising drug carrier system. The absorption bands were well defined, confirming the presence
of the functional groups in the samples. 相似文献
992.
Eliane S. C. Temba Aluísio S. Reis Júnior Ângela Maria Amaral Roberto P. G. Monteiro 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(3):631-635
A methodology for the determination of 90Sr in low- and intermediate-level radioactive wastes from nuclear power plants is presented in this work. It is a part of
a methodology developed for the sequential radiochemical separation of radionuclides difficult-to-measure directly by gamma
spectrometry in these radioactive wastes. The separation procedure was carried out using precipitation and extraction chromatography
with Sr Resin, from Eichrom and the 90Sr was measured by liquid scintillation counting (LSC). Optimum conditions for the pretreatment, separation and LSC measurements
were determined using simulated samples, which were prepared using standard solutions and carriers. The procedure showed to
be rapid and achieved a good chemical yield, in the range 60–90%, and a detection limit of 6.0 × 10−4 Bq g−1. The method was also tested by participation in a national intercomparison program, with aqueous samples, with good agreement
of results. 相似文献
993.
In this research,a lucunary Keggin structure,[PMo2W9O39]7- was selected as an efficient homogenous catalyst for degradation of an azo dye(direct blue 71) and a simple method was developed for degradation of DB71.The method is based on the oxidation of azo dye in the presence of a lucunary Keggin form of polyoxometalates,K7[PMo2W9O39]? 19H2O,as a homogenous catalyst at room temperature.The reaction is monitored spectrophotometrically by measuring the absorbance of dye atλ=585 nm.Some parameters including concentration of catalyst,concentration of H2O2,pH and reaction time were investigated and optimized. Results show that K7[PMo2W9O39]? 19H2O is more efficient in the presence of hydrogen peroxide.Degradation of dye in the presence of the catalyst and H2O2 could lead to the disappearance approximately 65%of dye after 60 min.But degradation for the same experiment performed in the absence of catalyst or in the absence of H2O2 was 22%or 5%respectively.Approximately 87% azo dyes has been eliminated after 90 min in the presence of catalyst,H2O2 and optimize conditions(0.6 g/L of K7[PMo2- W9O39H9H2O,0.08 mol/L hydrogen peroxide and room temperature). 相似文献
994.
Ana T.P.C. GomesAnna C. Cunha Maria do Rosário M. DominguesMaria G.P.M.S. Neves Augusto C. ToméArtur M.S. Silva Fernanda da C. SantosMaria C.B.V. Souza Vitor F. FerreiraJosé A.S. Cavaleiro 《Tetrahedron》2011,67(38):7336-7342
New porphyrin/4-quinolone conjugates were synthesized from the Suzuki-Miyaura coupling reaction of a β-borylated porphyrin with bromo-4-quinolones containing N-ethyl and N-d-ribofuranosyl substituents. The use of electrospray ionization tandem mass spectrometry showed important information about the fragmentation pathways of the new compounds. It was possible to distinguish between those compounds with the porphyrin moiety linked at the 6-position of the quinolone unit from their 7-substituted isomers. The new compounds showed to be good singlet oxygen generators. 相似文献
995.
996.
Donzello MP De Mori G Viola E Ercolani C Bodo E Mannina L Capitani D Rizzoli C Gontrani L Aquilanti G Kadish KM D'Angelo P 《Inorganic chemistry》2011,50(23):12116-12125
The solid state and solution structure of 2,3-dicyano-5,6-di(2-thienyl)-1,4-pyrazine, [(CN)(2)Th(2)Pyz], and its Pd(II) derivative, [(CN)(2)Th(2)Pyz(PdCl(2))(2)]·H(2)O, formed by reaction of [(CN)(2)Th(2)Pyz] with [(C(6)H(5)CN)(2)PdCl(2)] were characterized by X-ray, UV-visible, (1)H and (13)C NMR, and extended X-ray absorption fine structure (EXAFS) spectral measurements. The X-ray crystal structure of [(CN)(2)Th(2)Pyz] shows the presence of one thienyl ring positioned orthogonal to the rest of the molecule, with the two vicinal thienyl rings lying orthogonal to each other in a rare arrangement. NMR studies of [(CN)(2)Th(2)Pyz] in the solid state and in solutions of dimethylformamide or dimethyl sulfoxide confirm a nonequivalence of the thienyl rings in the solid state and also in solution. EXAFS results indicate that two distinct Pd(II) coordination sites are formed at the di(2-thienyl)pyrazino moiety of [(CN)(2)Th(2)Pyz(PdCl(2))(2)]·H(2)O, with identical Pd-N(pyz) (2.03(3) ?) and Pd-Cl (2.36(3) ?) bond lengths but with different Pd-S1 (2.25(4) ?) and Pd-S2 (3.21(5) ?) bond distances in an overall asymmetric molecular framework. Density functional theory (DFT) and time-dependent DFT (TDDFT) theoretical studies also provide information about the structure and spectral behavior of the precursor and its metalated Pd(II) derivative. (1)H/(13)C NMR and UV-visible spectral measurements were also carried out on two heteropentametallic porphyrazine macrocycles which were prepared by a reaction of PdCl(2) with [Th(8)TPyzPzM] where Th(8)TPyzPz = tetrakis-2,3-[5,6-di-(2-thienyl)-pyrazino]porphyrazinato dianion and M = Mg(II)(H(2)O) or Zn(II). Spectroscopic data on the newly synthesized [(PdCl(2))(4)Th(8)TPyzPzM] compounds suggest that the binding of PdCl(2) involves coordination sites of the type S(2(th))PdCl(2) with the two thienyl rings of each di(2-thienyl)pyrazino fragment bound to Pd(II) in an equivalent manner ("th-th" coordination). This is similar to what was found for the corresponding octapyridinated analogues ("py-py" coordination). 相似文献
997.
Kharitonov Yu. V. Shul’ts E. E. Shakirov M. M. Tolstikov G. A. 《Russian Journal of Organic Chemistry》2011,47(4):602-605
The reaction of phlomisoic acid methyl ester with styrene, catalyzed by Pd(OAc)2, in the presence of Cu(OAc)2 and 1,4-benzoquinone in a mixture of propionic acid with diethyl ether gave the corresponding 15,16-distyryl derivative and
only traces of 15- and 16-monosubstituted furanolabdanoids. Oxidative coupling of the title compound with methyl acrylate
under analogous conditions afforded a mixture of 15-mono-, 16-mono-, and 15,16-dialkenylation products whose ratio changed
during the process. The reaction was stereoselective, and the exocyclic double bond in the products had exclusively E configuration. 相似文献
998.
Tolstikov A. G. Savchenko R. G. Nedopekin D. V. Afon’kina S. R. Lukina E. S. Odinokov V. N. 《Russian Chemical Bulletin》2011,60(1):160-167
A three-component condensation of aromatic amine, aldehyde, and cyclopentadiene with subsequent N-trifluoroacetylation leads to 4- and 4,8-substituted N-trifluoroacetyl-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinolines. Ozonation of the double bond in the latter produced the corresponding isomeric stable ozonides having (1R*,4S*,5aR*,6S*,11bR*)-configuration and differing in inversion at the carboxamide nitrogen atom. 相似文献
999.
A. N. Krasovskii I. V. Vasil’eva S. V. Myakin N. A. Osmolovskaya S. V. Borisova 《High Energy Chemistry》2011,45(5):390-396
The structure, relaxation, and surface properties of cellulose triacetate (CTA) fibers and films modified by electron-beam
irradiation in the absorbed dose range of D = 0−1000 kGy have been studied. The relation of the glass transition and melting temperatures of the irradiated CTA samples
with the local density and the fractal dimensionality of the macrochain has been revealed. It has been shown that the radiation-chemical
processes associated with the rupture of acetal bonds and the hydrolysis of CTA acetate groups predetermine the change in
the structural and relaxation characteristics of the irradiated samples, as well as a nonmonotonic form of the dependence
of the density and the surface energy of the films upon the absorbed dose near the threshold value of D = 75 kGy. 相似文献
1000.
M. G. Voronkov é. A. Zel’bst V. S. Fundamenskii V. A. Bruskov A. A. Kashaev A. S. Soldatenko Yu. I. Bolgova O. M. Trofimova 《Journal of Structural Chemistry》2011,52(4):828-830
The crystal and molecular structure of a 1-(1-silatranylmethyl)-3,5-dimethylpyrazole complex with zinc dichloride (I) is determined by XRD. The coordination polyhedron of the zinc atom is a tetrahedron formed by two covalent Zn-Cl bonds and
coordination Zn ← N and Zn ← O bonds. Compound I is the first example of how an endocyclic oxygen atom of the silatranyl fragment participates in the coordination of the
metal atom with the formation of a six-membered heterocycle. 相似文献