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111.
112.
Kinetic study of the reactions of diphenyldiazomethane with various electron acceptors were made in six aromatic solvents. Log k were correlated with the solvent basicity parameter, Dπ, and the regression slopes were found to be a function of electron affinities. 相似文献
113.
Haruyasu Asahara Takuya Koizumi Eiko Mochizuki Takumi Oshima 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(3):o136-o138
The crystal structures of the two thermally equilibrated conformational isomers of the epoxide 1′,5′‐dimethylspiro[10,11‐dihydro‐5H‐dibenzo[a,d]cycloheptene‐5,8′‐4′‐oxatricyclo[5.1.0.03,5]octane]‐2′,6′‐dione, C23H20O3, have been determined by X‐ray diffraction. In the tricyclic dione skeleton, the oxirane and cyclopropane rings adopt an anti structure with respect to the conjunct quinone frame. The spiro‐linked 10,11‐dihydro‐5H‐dibenzo[a,d]cycloheptene ring of the major isomer has a fairly twisted boat form, folding opposite to the adjoining cyclopropane methyl substituent, whereas the seven‐membered ring of the minor isomer has an almost ideal twist–boat form, inversely folding to the side of the relevant methyl group. The conformational structures of these isomers have been compared with those of the corresponding isomers of the unepoxidized homobenzoquinone. 相似文献
114.
115.
[graph: see text] We describe the synthesis of new environmentally sensitive fluorescence probes to elucidate DNA structures. DNA oligonucleotides containing fluorophore dan (6-(dimethylamino)-2-acylnaphthalene)-modified dC or dG were able to monitor the microenvironmental changes in both the major and minor grooves of DNA with a B- to A-DNA conformational transition and RNA hybridization. 相似文献
116.
Only supercritical carbon dioxide (scCO2) as a reactant and a solvent, and catalytic amount of base (DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), DBN (1,5-diazabicyclo[4.3.0]non-5-ene), Dabco® (1,4-diazabicyclo[2.2.2]octane), and triethylamine) afforded 1H-quinazoline-2,4-diones in good to excellent yields from 2-aminobenzonitriles. 6,7-Dimethoxy-1H-quinazoline-2,4-dione, which is a key intermediate of medicines (Prazosin, Bunazosin, and Doxazosin) was synthesized successfully in a 97% yield, using 0.1 equiv of DBU under scCO2 (10 MPa) at 80 °C. 相似文献
117.
Shinji Kosaka Takumi Fujiwara Takayuki Komatsu 《Journal of solid state chemistry》2005,178(6):2067-2076
The ternary BaO-TiO2-B2O3 glasses containing a large amount of TiO2 (20-40 mol%) are prepared, and their optical basicities (Λ), the formation, structural features and second-order optical nonlinearities of BaTi(BO3)2 and Ba3Ti3O6(BO3)2 crystals are examined to develop new nonlinear optical materials. It is found that the glasses with high TiO2 contents of 30-40 mol% show large optical basicities of Λ=0.81-0.87, suggesting the high polarizabity of TiOn polyhedra (n=4-6) in the glasses. BaTi(BO3)2 and Ba3Ti3O6(BO3)2 crystals are found to be formed as main crystalline phases in the glasses. It is found that BaTi(BO3)2 crystals tend to orient at the surface of crystallized glasses. The new XRD pattern for the Ba3Ti3O6(BO3)2 phase is proposed through Rietvelt analysis. The second harmonic intensities of crystallized glasses were found to be 0.8 times as large as α-quartz powders, i.e., I2ω(sample)/I2ω(α-quartz)=0.8, for the sample with BaTi(BO3)2 crystals and to be I2ω(sample)/I2ω(α-quartz)=68 for the sample with Ba3Ti3O6(BO3)2 crystals. The Raman scattering spectra for these two crystalline phases are measured for the first time and their structural features are discussed. 相似文献
118.
119.
Uota M Arakawa H Kitamura N Yoshimura T Tanaka J Kijima T 《Langmuir : the ACS journal of surfaces and colloids》2005,21(10):4724-4728
A new surfactant-mediated approach was developed to synthesize hydroxyapatite (HAp) nanoparticles with high surface areas by calcination of their precursors encapsulated with calcium stearate using mixed surfactant-containing reaction mixtures. Acidic aqueous solution of calcium phosphate was mixed with both or either nonaoxyethylene dodecyl ether (C12EO9) and polyoxyethylene(20) sorbitan monostearate (Tween 60) and then was treated with aqueous ammonium at 25 degrees C. The C12EO9-based single surfactant system yielded an aggregate of platy HAp nanoparticles 20-40 nm in size, whereas the Tween 60-based single and mixed systems led to lath-shaped HAp nanoparticles 2-8 nm wide and encapsulated with calcium stearate. On calcination at 500 degrees C, the stearate-encapsulated HAp nanoparticles in the latter two systems were deorganized into high surface area HAp nanoparticles. Particularly, the HAp nanoparticles in the mixed system exhibited a specific surface area as high as 364 m2 g(-1) that is roughly 3 times larger than 160 m2 g(-1) for those in the single system. The significantly high surface area for the former is attributed to much less adhesion of decapsulated HAp nanoparticles, which originated from the particle-separating effect of the C12EO9 molecules adsorbed on the outer surface of the stearate-encapsulated HAp nanoparticles to inhibit their agglomeration or interfacial coordination. The present results demonstrate that the mixed use of two different surfactants as a source of encapsulating and templating agent and a particle-separating agent is specifically effective for the synthesis of high surface area HAp nanoparticles. 相似文献
120.
Takafumi Shido Takumi Okazaki Masaru Ichikawa 《Journal of molecular catalysis. A, Chemical》1997,120(1-3):33-45
Structure and catalytic activity of Ir4(CO)12 bound to tris-(hydroxymethyl)phosphine (THP) grafted silica (THP/SiO2) was investigated by means of EXAFS, FT-IR and kinetic studies. It was found that Ir4(CO)12 was uniformly attached on THP/SiO2 by substitution of CO by THP (Ir4/THP/SiO2). The tetra-iridium carbonyl cluster framework was remained during the substitution of THP ligands and two THP ligands coordinated to the iridium carbonyl clusters to form Ir4(CO)10(THP/SiO2)2. species. When Ir4/THP/SiO2 was evacuated at 373 K, bridge CO was desorbed and Debye-Waller factor of Ir---Ir contribution derived from EXAFS analysis was increased which suggested that the cluster framework was distorted by the evacuation at 373 K. The resulting sample evacuated at 373 K was an active catalyst for hydroformylation of ethene and partial oxidation of propene, while the Ir4/THP/SiO2 without evacuation exhibited poor catalytic activities. The propene oxidation reaction proceed on the Ir4/THP/SiO2 evacuated at 323–353 K under subatmospheric pressures to give acetone as a product in high selectivity. The ethene hydroformylation proceed on the evacuated Ir4/THP/SiO2 at lower temperatures compared with other conventional iridium catalysts. EXAFS characterization and kinetic studies suggested that the catalytic activities were associated with the structural distortion of the iridium cluster framework due to surface attachment by the bidentate phosphine substitution. 相似文献