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101.
S.C. Ng 《European Polymer Journal》1982,18(10):917-919
A kinetic study of the aqueous polymerisation of methacrylamide initiated by hydrogen peroxide has shown that the polymerisation proceeds in two stages. The rate of polymerisation up to about 16% conversion is represented by the equation Within this period, the hydrogen peroxide is completely consumed and a hydroperoxide of methacrylamide is formed. Subsequently this hydroperoxide initiates polymerisation. 相似文献
102.
Simon G. Bott Ulrich Kynast Jerry L. Atwood 《Journal of inclusion phenomena and macrocyclic chemistry》1986,4(3):241-246
18-crown-6 reacts with TiCl3 in CH2Cl2 to form a complex in which the crown ether functions as a tridentate ligand. Addition of moist hexane affords a molecular complex in which the crown ether functions as a bidentate ligand. A water molecule is bonded directly to the titanium atom and is further hydrogen bonded to three of the oxygen atoms of the crown. The deep blue crystals of the CH2Cl2 adduct belong to the monoclinic space groupP21/n witha=13.481(8),b=8.021(5),c=21.425(9) Å, =97.32(5)°, and
calc = 1.51 g cm–3 forZ=4. Refinement led to a conventionalR value of 0.040 based on 873 observed reflections. The Ti–O bond distances for the crown oxygen atoms are 2.123(8) and 2.154(9) Å, while the oxygen atom of the water molecule is bonded at 2.072(8) Å. The octahedral coordination sphere of the titanium atom is completed by the three chlorine atoms at distances of 2.340(5), 2.352(4), and 2.373(4) Å.
Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82034 (10 pages). 相似文献
103.
Miller CR Vogel R Surawski PP Jack KS Corrie SR Trau M 《Langmuir : the ACS journal of surfaces and colloids》2005,21(21):9733-9740
Thiol-functionalized organosilica microspheres were synthesized via a two-step process: (1) acid-catalyzed hydrolysis and condensation of 3-mercaptopropyltrimethoxysilane (MPTMS), followed by (2) base-catalyzed condensation, which led to the rapid formation of emulsion droplets with a narrow size distribution. These droplets continued to condense to form solid microspheres. Solution (29)Si NMR and optical microscopy were applied to study the mechanism of this novel synthetic route. Solid-state (29)Si NMR, SEM, zeta potential titration, and Coulter counter measurements were used to study the bulk and surface properties and to determine the particle size distributions of the final microspheres. Compared to conventional St?ber silica particles, these microspheres were shown to have a lower degree of cross-linking (average degree of condensation, r = 1.25), a larger average size (up to 6 microm), and a higher isoelectric point (pH = 4.4). Confocal microscopy of dye-labeled microspheres showed an even distribution of dye molecules throughout the interior, characteristic of a readily accessible and permeable organosilica network. These findings have implications for the production of functionalized solid supports for use in catalysis and biological applications, such as optically encoded carriers for combinatorial synthesis. 相似文献
104.
Simon S. Jones Colin B. Reese Samson Sibanda Aiko Ubasawa 《Tetrahedron letters》1981,22(47):4755-4758
The protection of uracil and 2--acyl guanine residues with 4--phenyl [or 4--(2,4-dimethylphenyl)] and 6--(2-nitrophenyl) groups as in [or ] and , respectively, is described. These -aryl protecting groups, which appear to withstand the usual conditions of oligonucleotide synthesis, may readily be removed by treatment with 2-nitrobenzaldoximate ions. 相似文献
105.
Pennington DA Coles SJ Hursthouse MB Bochmann M Lancaster SJ 《Chemical communications (Cambridge, England)》2005,(25):3150-3152
The mono(salicylaldiminato) complexes Ti{3-tBu-2-(O)C6H3CH=N(R)}Cl3(THF)(where R = C6H5, C6F5) react with the metallated pyrrolylaldiminato ligand, K[2-(C6H5NCH)C4H3N], to afford the first examples of hybrid salicylaldiminato-ligated octahedral titanium complexes; the pre-catalysts give from very high to extremely high ethene polymerisation productivities when activated with MAO. 相似文献
106.
M. Ştefănescu M. Stoia O. Ştefănescu A. Popa M. Simon C. Ionescu 《Journal of Thermal Analysis and Calorimetry》2007,88(1):19-26
Hybrid organic-inorganic materials,
silica – polyols (ethylene-glycol – EG; 1,2 propane diol –
1,2PG; 1,3 propane diol – 1,3PG and glycerol – GL), were prepared
by a sol-gel process starting from tetraethylorthosilicate (TEOS) and polyols,
in acid catalysis. The resulting materials were studied by thermal analysis
(in air and nitrogen), FTIR and solid state 29Si-NMR
spectroscopy. These techniques evidenced the presence of polyols in the silica
matrix both hydrogen bounded and chemically bounded in the silica network.
The thermal analysis proves to be the most appropriate technique to evidence
the organic chains linked in the matrix network and to follow the thermal
evolution of the gels to the SiO2 matrix. 相似文献
107.
Bolei Yan Simon W. Lewis Paul J. Worsfold J.Steven Lancaster Anthony Gachanja 《Analytica chimica acta》1991
An overview of liquid phase chemiluminescence (CL) processes is presented and the potential for CL detection in liquid chromatography (LC) is discussed, with particular reference to the luminol and peroxyoxalate reactions. Post column ion displacement from a solid phase reagent [a cation exchange resin in the copper(II) form] followed by catalysis of the luminol reaction is used for the quantification of mixtures of weak acids after separation by ion-exclusion chromatography. Polyaromatic hydrocarbons (PAHs) released during the combustion of biomass fuels are separated by reversed-phase chromatography and quantified by their sensitizing effect on the peroxyoxalate reaction. This procedure is also used for the determination of carboxylic acids in non-aqueous media after selective pre-column derivatization with a fluorescent label (9-anthracenemethanol). 相似文献
108.
Simon J. Pridmore 《Tetrahedron letters》2007,48(29):5115-5120
Various 1,2,5-substituted pyrroles have been synthesised from 1,4-alkynediols using a ruthenium catalysed isomerisation to give the corresponding 1,4-dicarbonyl compounds, which undergo in situ cyclisation to pyrroles in the presence of amine. 相似文献
109.
Jeffrey C. Evans Simon K. Jackson Christopher C. Rowlands Martin D. Barratt 《Tetrahedron》1985,41(22):5191-5194
Under acid conditions aqueous solutions of chloramine-T form nitrogen-centred radicals via loss of the chlorine atom. The nitrogen radicals produced have been studied by ESR spectroscopy using the spintrapping method. Adducts of the spin trap phenyl-t-butyl nitrone are oxidized by chloramine-T in acid media to give a paramagnetic product in which the unpaired electron interacts with two inequivalent nitrogen atoms. The spin trap 5,5-dimethyl-2-pyrrolidine-1 -oxide is oxidized rapidly to 5,5-dimethyl-2-pyrrolidone-1-oxyl by chloramine-T under acid onditions. The water soluble trap α-4-pyridyl-1-oxide-N-t-butyl nitrone forms a stable nitroxide adduct with a nitrogen radical of chloramine-T in acid solution. Identical results were obtained with chloramine-B (sodium salt of N-chlorobenzene sulfonamide), indicating the involvement of the N-chloramine group in radical formation. 相似文献
110.
Summary A simple and rapid systematic optimization scheme was described for the micellar electrokinetic chromatographic separation of a group of flavonoids. The scheme employed an interpretative optimization approach to predict the optimum conditions for the separation of a group of flavonoids by micellar electrokinetic chromatography. By performing a set of nine pre-planned experiments conducted over the maximum working range for the system, global optimum separation conditions could be determined. To validate the optimization procedure, additional experiments were performed using the optimum experimental conditions derived from the optimization scheme. The results showed that satisfactory separation of all the peaks could be obtained. In addition, the application of the method in micropreparative micellar electrokinetic chromatography of the flavonoids was demonstrated. 相似文献