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91.
采用水提-醇沉法从贯众中提取多糖,脱脂、去蛋白,经冷冻干燥后得到粗多糖。通过比色法研究其体外清除羟基自由基能力。贯众多糖具有较好的清除.OH的能力,且其清除能力与多糖浓度有明显的量效关系。清除50%羟基自由基所需要的多糖浓度为3.9m g/mL。 相似文献
92.
Takayuki Yamamoto Kenichi Kato Daiki Shimizu Takayuki Tanaka Atsuhiro Osuka 《化学:亚洲杂志》2019,14(22):4031-4034
Stable meta‐ and para‐phenylene bridged porphyrin meso‐oxy radical dimers and their NiII and ZnII complexes were synthesized. All the dimers exhibited optical and electrochemical properties similar to the corresponding porphyrin meso‐oxy radical monomers, indicating small electronic interaction between the two spins. Intramolecular spin‐spin interaction through the π‐spacer was determined to be J/kB=?15.9 K for m‐phenylene bridged ZnII porphyrin dimer. The observed weak antiferromagnetic interaction has been attributed to less effective conjugation between the porphyrin radical and linking π‐spacer due to large dihedral angle. In the case of ZnII complexes, both para‐ and meta‐phenylene bridged dimers formed 1D‐chain in solutions and in the solid states through Zn‐O coordination. 相似文献
93.
Time-resolved Fourier transform emission spectroscopy of AΠ-XΣ infrared transition of the CN radical
The A2Π-X2Σ+Δv = −3 bands of the 12C14N radical have been observed by time-resolved Fourier transform spectroscopy in the 1850-3100 cm−1 region with a wavenumber resolution of 0.025 cm−1. The radical was produced in a pulsed positive column discharge in a cyanogene and helium mixture. Seven bands of v = 0-3, 1-4, 2-5, 3-6, 4-7, 5-8, and 6-9 were analyzed to give the molecular constants of each state by least-squares fitting of 801 lines. The pulsed discharge was found to be efficient for production of CN in the excited A2Π state. The vibrational excitation temperature was determined to be 6680 ± 835 K and 6757 ± 534 K for the A2Π and X2Σ+ states, respectively. The population of the A2Π was found to be 4% of that of the X2Σ+ state in the time after turning off the discharge. 相似文献
94.
Shigekazu Ito Manabu Kikuchi Masaaki Yoshifuji 《Journal of organometallic chemistry》2007,692(13):2761-2767
A kinetically stabilized phosphaalkyne bearing a bulky Mes∗ (2,4,6-tri-t-butylphenyl) group is useful compound to prepare an enormous number of highly stable 1,3-diphosphacyclobutane-2,4-diyls through reactions with a lithium reagent and an electrophile. By utilizing this synthetic protocol, we prepared several non-symmetrical 1,3-diphosphacyclobutane-2,4-diyls in which the substituents on the phosphorus are different. Furthermore, we succeeded in preparation and characterization of novel air-tolerant symmetrical 2,4-bis(2,4,6-tri-t-butylphenyl)-1,3-diphosphacyclobutane-2,4-diyls bearing the identical alkyl substituents on the phosphorus atoms. Structures and properties of the 1,3-diphosphacyclobutane-2,4-diyls indicate characters as singlet ground-state carbon centered biradicals. In addition to those biradicals, we succeeded in preparation and isolation of a novel P-heterocyclic air-stable neutral radical as well as a P-heterocyclic cation radical. 相似文献
95.
ArnaudPierre Schaffner Kandhasamy Sarkunam Philippe Renaud 《Helvetica chimica acta》2006,89(10):2450-2461
A tandem radical process involving conjugate addition to an activated alkene followed by allylation is reported. B‐Alkylcatecholboranes, easily available via hydroboration of the corresponding alkenes, were used to generate the initial radicals. These radicals add efficiently to electrophilic alkenes such as phenyl vinyl sulfone, N‐phenylmaleimide, and dialkyl fumarate. In the last step of this one‐pot process, the radical adducts react with the allylic sulfones. The whole process can be considered as a unique and selective coupling of three different alkenes. 相似文献
96.
Plácido García Maximiliano Burgos Paci Thorsten Berends 《Journal of fluorine chemistry》2005,126(6):984-990
The synthesis of the new compound, bis(trifluoromethyl)dicarbonate, CF3OC(O)OC(O)OCF3, is carried out by reduction of bis(trifluoromethyl)trioxidicarbonate with excess of CO at 0 °C. The product is characterized by IR, Raman, 13C and 19F NMR spectroscopy and its properties are compared with those of the other members of the series CF3OC(O)OxC(O)OCF3, x = 0-3. Single crystals are grown at −25 °C and the X-ray diffraction analysis shows the packing of syn-syn rotamers exhibiting C2 symmetry. DFT calculations predict this rotamer as the most stable one and also structural and vibrational data are predicted reasonably well. 相似文献
97.
Eric Léonel Michael Lejaye Sylvain Oudeyer Jean Paul Paugam Jean-Yves Nédélec 《Tetrahedron letters》2004,45(12):2635-2638
The activation of CBr4 and CCl4 by a bimetallic iron/copper couple in acetonitrile is a new, inexpensive, nontoxic and efficient procedure for gem-dibromo- and gem-dichloromethylenation of nucleophilic alkenes. This new route to gem-dihalocyclopropanes involves dihalocarbene species. 相似文献
98.
The 4‐exo cyclizations of two types of carbamoyl radicals onto O‐alkyloxime acceptor groups were studied as potential routes to 3‐amino‐substituted azetidinones and hence to penicillins. A general synthetic route to ‘benzaldehyde oxime oxalate amides’ (= 2‐[(benzylideneamino)oxy]‐2‐oxoacetamides; see, e.g., 10c ) of 2‐{[(benzyloxy)imino]methyl}‐substituted thiazolidine‐4‐carboxylic acid methyl esters 9 was developed (Scheme 3). It was shown by EPR spectroscopy that these compounds underwent sensitized photodissociation to the corresponding carbamoyl radicals but that these did not ring close. An analogous open‐chain precursor, benzaldehyde O‐(benzylaminoacetaldehyde‐O‐benzyloxalyl)oxime, 15 , lacking the 5‐membered thiazolidine ring, was shown by EPR spectroscopy to release the corresponding carbamoyl radical (Scheme 4). The latter underwent 4‐exo cyclization onto its C?NOBn bond in non‐H‐atom donor solvents. The rate constant for this cyclization was determined by the steady‐state EPR method. Spectroscopic evidence indicated that the reverse ring‐opening process was slower than cyclization. 相似文献
99.
Ewa Kornacka Izabela Legocka Gra?yna Przybytniak Jaros?aw Sad?o 《Polymer Degradation and Stability》2006,91(9):2182-2188
The effect of ionizing radiation on poly(siloxaneurethaneureas), comprising the soft phase of poly(dimethylsiloxane) chains and hard urethane segments, was examined by electron paramagnetic resonance (EPR) spectroscopy and gas chromatography (GC). It was found that radical processes in the investigated polymers were determined predominantly by polysiloxane segments. Dehydrogenation proceeded mainly in the terminal groups of dimethylsiloxane sequences, forming methylene radicals, whereas abstraction of methyl group dominated in inner fragments of the polysiloxane chain. However, upon irradiation no change in glass transition temperature of polysiloxane segments was detected by DSC. 相似文献
100.
Ohashi N Fujitake M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(14):3277-3284
Spectroscopic results on the radicals HCSi, CCO, and FeC obtained by studying in detail energy level structures using 0.8 microm diode laser system are reported. Of these radicals, the CCO radical was investigated mainly using Fabry-Perot type diode lasers with inconvenient mode gaps in the early stage of our near-infrared diode laser spectroscopic study of free radicals, and on the other hand, the FeC and HCSi radicals were studied using an external cavity diode laser. For the FeC radical, which is an interesting radical composed of an iron atom having 3d electrons, information on spin-orbit interaction between the triplet electronic ground state and a low-lying singlet electronic excited state is reported somewhat in detail. For the HCSi and CCO radicals, spectral particularities produced by a Renner-Teller interaction and a spin-orbit interaction are described for their high-resolution spectroscopic interest. 相似文献