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排序方式: 共有331条查询结果,搜索用时 15 毫秒
1.
2.
A novel diselenide was synthesized in good yield via only four steps from phenol, and was employed as the catalyst for the Baeyer-Villiger oxidation with 30% H2O2 to obtain lactones in good yields. 相似文献
3.
Yoshiki Chujo Kenji Kohno Noriyuki Usami Yuya Yamashita 《Journal of polymer science. Part A, Polymer chemistry》1989,27(6):1883-1890
Amphiphilic block copolymers, i.e., poly(methyl methacrylate)-b-poly(2-dimethylethylammoniumethyl methacrylate), were synthesized by the reaction between two prepolymers. Carboxyl-terminated poly(methyl methacrylate) and hydroxyl-terminated poly(2-dimethylaminoethyl methacrylate) were prepared by radical polymerization of the corresponding monomers in the presence of thioglycolic acid and 2-mercaptoethanol as a chain transfer agent, respectively. Two condensation methods, i.e., DCC and the acid chloride method, were used for the reactions of these prepolymers. The subsequent quarternization produced the amphiphilic block copolymers. Surface property of poly(methyl methacrylate) films containing this amphiphilic block copolymer was examined by measuring contact angles for water. The addition of only 0.5 wt% of the block copolymer was sufficient to make poly(methyl methacrylate) surfaces hydrophilic. The block copolymer formed a polymeric micelle in acetone–water mixed solvent. 相似文献
4.
A solid material consisting of dimethyl glyoxime (DMG), acenaphthenequinone dioxime (ANDO) or DMG-ANDO on naphthalene provides a very convenient, rapid and economical method for the preconcentration of palladium in synthetic samples. Pd-DMG, Pd-ANDO and Pd-DMG-ANDO are quantitatively retained on naphthalene in the column in the pH ranges 2.2–4.4, 1.8–5.6 and 1.7–6.8, respectively. The solid mixture consisting of the metal complex together with naphthalene is stripped from the column with 5 ml of dimethylformamide (DMF)-n-butylamine and the absorbance is measured at 247.6 nm with an atomic absorption spectrometer. Calibration graphs are linear over the palladium concentration range 5–25 μg per 5 ml of the final solution for all the three complexes. Ten replicate determinations of a sample solution containing 10 μg of palladium gave mean absorbances of 0.180, 0.225 and 0.230 with relative standard deviations of 1.8, 1.7 and 1.6% using the reagents DMg, ANDO and DMG-ANDO, respectively. The sensitivity of the method is better than the direct atomic absorption spectrometric determination of palladium. It is highest in case of the mixed ligands, i.e., DMG-ANDO (0.038 μg ml?1 for 1% absorption). The method can be applied to the trace determination of palladium in complex materials. 相似文献
5.
Kazuhiro Watanabe Noboru Akino Tetsuo Aoyagi Noboru Ebisawa Yukio Fujiwara Atsusi Honda Takashi Inoue Takao Itoh Mikito Kawai Minoru Kazawa Junichi Koizumi Masaaki Kuriyama Kenji Miyamoto Naoki Miyamoto Kazuhiko Mogaki Yoshihiro Ohara Tokumichi Ohga Yoshikazu Okumura Hiroshi Oohara Katsumi Ohshima Fujio Satoh Kazuhiko Shimizu Syunji Takahashi Hirotsugu Usami Katsutomi Usui Masahiro Yamamoto Takeshi Yamazaki 《Radiation Physics and Chemistry》1997,49(6):631-639
A negative-ion-based neutral beam injector (N-NBI) has been constructed for JT-60U. The N-NBI is designed to inject 500 keV, 10 MW neutral beams using two ion sources, each producing a 500 keV, 22 A D− ion beam. In the preliminary experiment using one ion source, a D− ion beam of 13.5 A has been successfully accelerated with an energy of 400 keV (5.4 MW) for 0.12 s at an operating pressure of 0.22 Pa. This is the highest D− beam current and power in the world. Co-extracted electron current was effectively suppressed to the ratio of Ie/ID− < 1. The highest energy beam of 460 keV, 2.4 A, 0.44 s has also been obtained. To realize 1 MeV class NBI system for ITER (International Thermonuclear Experimental Reactor), demonstration of ampere class negative ion beam acceleration up to 1 MeV is an important mile stone. To achieve the mile stone, a prototype accelerator and a 1 MV, 1 A test facility called MeV Test Facility (MTF) were constructed. Up to now, an H− ion beam was accelerated up to the energy of 805 keV with an acceleration drain current of 150 mA for 1 s in a five stage electrostatic multi-aperture accelerator. 相似文献
6.
F. Hirayama M. Usami K. Kimura K. Uekama 《Journal of inclusion phenomena and macrocyclic chemistry》1996,25(1-3):165-168
Chloramphenicol palmitate (CPP) was converted to an amorphous complex when spray-dried with 2-hydroxypropyl--cyclodextrin (HP--CyD), and no crystallization of CPP was observed for at least 2 months under the storage condition of 50°C and 50% relative humidity. The dissolution rate of CPP/HP--CyD complex in aqueous HCO-60 solution was much faster than CPP polymorphs (complex > metastable forms (B and subB) > stable form (A)), which was reflected in thein-vivo absorption behavior of CPP following oral administration in dogs. 相似文献
7.
Peroxotungstate immobilized on ionic liquid-modified silica as a heterogeneous epoxidation catalyst with hydrogen peroxide 总被引:6,自引:0,他引:6
Yamaguchi K Yoshida C Uchida S Mizuno N 《Journal of the American Chemical Society》2005,127(2):530-531
Peroxotungstate immobilized on ionic liquid-modified SiO2 is capable of heterogeneously epoxidizing a wide range of olefins with the maintenance of the catalytic activity of homogeneous analogue. The epoxidation was immediately stopped by the removal of the catalyst, and no tungsten species could be found in the filtrate after the removal of the catalyst. These results can rule out any contribution to the observed catalysis from the tungsten species that leached into the reaction solution, and the observed catalysis is truly heterogeneous in nature. Furthermore, the catalyst was reusable without the loss of the catalytic performance. 相似文献
8.
Noritaka Ohtani Makoto Nakaya Kenji Shirahata Tsuyoshi Yamashita 《Journal of polymer science. Part A, Polymer chemistry》1994,32(14):2677-2686
Polystyrene-based crosslinked cationic ionomers containing ammonium or phosphonium chlorides (AxRCI and PxBuCI) were reacted with decyl methanesulfonate. The kinetic data were correlated with the swelling behavior of the ionomers and the solution viscosity of the corresponding linear ionomers. The reactivity of the ionomers was independent of the particle size of the ionomer beads, indicating no diffusion control of the reaction. The solvent and the ion content of the ionomers greatly affect the reactivity. In nonpolar solvents with a low acceptor number, AN, such as toluene, the aggregation of ionic groups with an increasing ion content reduces the reactivity. A solvent with a high value of AN, such as chloroform, led a very low reactivity independent of the ion content. Aprotic polar solvent, such as acetonitrila, promoted the dissociation of the ionic groups and furnished a relatively high reactivity independent of the ion content. Several catalytic substitution reactions were carried out under liquid-solid-solid triphase conditions. The kinetic results were accounted for in terms of slow nucleophile transport and fast chemical reaction within the ionomer particles. © 1994 John Wiley & Sons, Inc. 相似文献
9.
Ion-pair formation constants (KMLA mol−1 dm3) of Na+– and K+–18-crown-6 ether (18C6) complexes with MnO4− in water (w) were determined potentiometrically at 25 °C. Simultaneously, extraction constants (Kex mol−2 dm6) of the permanganates with 18C6 from w into 1,2-dichloroethane at 25 °C were obtained from the spectrophotometric determination of distribution ratios of the permanganates. These Kex values were divided into KMLA and other three component equilibrium constants and thereby extraction-selectivity and -ability were discussed in comparison with corresponding metal picrate–18C6 extraction systems reported before. 相似文献
10.
Kanae Hayashi Noritaka Kotani 《Journal of polymer science. Part A, Polymer chemistry》1980,18(1):191-202
Bulk polymerization of α-methylstyrene was carried out in a wide dose rate range, 7.6–256 rad/sec by γ rays and 8.5 × 103–2.1 × 105 rad/sec by electron beams. At high dose rate by electron beams, cationic polymerization took place along with formation of oligomeric product of DP n = ~4. At low dose rate by γ rays, radical polymerization was found to occur in water-saturated monomer. The cationic polymerization at high dose rate proceeds with essentially the same mechanism as was already known in γ-ray polymerization of dry monomers. Relatively low reaction rate of the cationic polymerization compared with that of styrene is explained with the fact that the propagation of α-methylstyrene is much more easily inhibited by a slight amount of water. 相似文献