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991.
8,5'-Aminimino bridging in the guanosine series using 5'-O-tosyl (1) and 5'-O-mesyl derivatives (2) of 2',3'-O-isopropylidene-8-bromoguanosine (5) and hydrazine gave N3,5'-cyclized product 3 and the N5,5'-cyclonucleoside of 4-carboxyhydrazido-5-amino-2-bromoimidazole 4. To exclude the N3,5'-cyclization through ionization in the base moiety, a N2-dimethylaminomethylidene-N1-methoxymethylene derivative 7 was synthesized from 5 through the N2-protected compound 6. 7 was converted into the N2-dimethylaminomethy analogue 8, which with hydrazine yielded first the N2-deprotected form of 8 (9). 8 or 9 with hydrazine under forcing conditions gave an 8,5'-aminimino-N1-methox derivative 10. Oxidation of 10 with sodium metaperiodate or sodium nitrite yielded 8,5'-imino-N1-methoxymethyleneguanosine (11a) and 8,5'-imino-N1-methoxymethylenexanthosine derivative 11b, respectively. 11a was deprotected to 8,5'-imino-N1-methoxymethyleneguanosine 12. 相似文献
992.
Treatment of 1-trimethylsilyl-7,7-dihalobicyclo[4.1.0]heptanes with silver tri-fluoroacetate in an alcoholic solvent such as methanol or ethanol at 0–60 °C gives moderate to good yields of 1-trimethylsilylbicyclo[4.1.0]heptan-7-one dialkyl acetal compounds, which result from the substitution of halogens on the cyclopropane ring. 相似文献
993.
Takeo Araki Takanobu Aoyagi Norikadzu Ueyama Tadashi Aoyama Hisaya Tani 《Journal of polymer science. Part A, Polymer chemistry》1973,11(4):699-712
Equimolar reaction of Et2AlOLi and Et2AlCl gave Et2AlOAlEt2. The catalyst behavior for polymerization of acetaldehyde, propylene oxide, and epichlorohydrin was compared with that of the AlEt3–H2O (1:0.5) catalyst system. The thermal disproportionation product of Et2AlOAlEt2 derived from Et2AlOLi–Et2AlCl had the structure, ? (EtAlO)n? , and it showed catalyst behavior quite similar to that of the product obtained by the same treatment of AlEt3–H2O (1:0.5). These ethylaluminum oxides can be regarded as species predominating in AlEt3–H2O (1:0.5) and AlEt3–H2O (1:1), respectively. Stereospecific or high molecular weight polymerizations of these species were investigated. 相似文献
994.
Normal-phase liquid chromatographic separation using polymeric synthetic adsorbents was investigated. The retention behavior of dialkyl phthalates under a hexane-isopropanol eluent system revealed that both polystyrenic and polymethacrylic adsorbents can be used for normal-phase liquid chromatography, and that the polymethacrylic adsorbent has stronger retentivity than the polystyrenic adsorbent. Applicability of these synthetic adsorbents, especially the polymethacrylic adsorbents, was verified by the separation of polyunsaturated fatty acids, schizandrin in Schisandra chinensis fruit, tocopherols and tocotrienols in vegetable oils using a 10-microm adsorbent packed into an HPLC column. Furthermore, the separation was expanded to preparative scale by using polymethacrylic adsorbents with 17- and 31-microm fine grade particle sizes. The effect of loading volume on the retention or separation was also examined, and separation was maintained up to the loading of several grams per liter adsorbent. These results demonstrate that commercially available synthetic adsorbents possess considerable performance as normal-phase chromatographic media for more precise purification of bioactive compounds. including pharmaceuticals and nutraceuticals with scale-up possibilities. 相似文献
995.
Mitsunori Honda Takahito Mita Toshiaki Nishizawa Toru Sano Masahito Segi Tadashi Nakajima 《Tetrahedron letters》2006,47(32):5751-5754
Treatment of 1-silylcyclopropylmethanols with TsOH in methanol gives different homoallyl ethers depending upon the configuration of substituents on cyclopropane ring and the kinds of substituents on carbinyl carbon. Especially, the reaction of cyclopropylmethanols having no substituents on the same side with silyl group on cyclopropane ring proceeds to give the corresponding E-homoallyl ethers with high stereoselectivity. The following protiodesilylation of resulting homoallyl ethers proceeds with retention of configuration. 相似文献
996.
Tadashi Mizoguchi Shun Sakamoto Yasushi Koyama Kenji Ogura Fuyuhiko Inagaki 《Photochemistry and photobiology》1998,67(2):239-248
997.
A simple and efficient method has been developed for the synthesis of 2-aminothiazoles and N-allylthioureas from commercially available materials in one pot by using a supported reagents system, KSCN/SiO2-RNH3OAc/Al2O3, in which α-halo ketone reacts first KSCN/SiO2 and the product, α-thiocyanatoketone, reacts with RNH3OAc/Al2O3 to give the final product, 2-aminothiazoles, in good yield and allyl bromide reacts with KSCN/SiO2 and the product, allyl isothiocyanate, reacts with RNH3OAc/Al2O3 to give N-allylthiourea. 相似文献
998.
Tadashi Kawai Yasue Shida Hirohisa Yoshida Jiro Abe Tomokazu Iyoda 《Journal of molecular catalysis. A, Chemical》2002,190(1-2):33-43
Metathesis of 2-vinyl aromatic heterocycles such as furan and thiophene has been investigated in the presence of a ruthenium-based Grubbs catalyst from a synthetic standpoint. The self-metathesis of 2-vinyl aromatic heterocycles was not successful. However, the cross-metathesis of these aromatic heterocycles with 1-octene occurred efficiently, but the selectivity of cross-metathesis product was very low, below 50%. The origin of the low selectivity of heterodimer formation was elucidated through metallacyclobutane intermediate mechanism, observations of carbenes by in situ 1H NMR, and the reaction products. The effect of oxygen on the reaction behavior was also examined. Furthermore, the data obtained on the Grubbs catalyst were compared with those on a molybdenum-based Schrock catalyst. 相似文献
999.
Tetsuo Yamasaki Eiji Kawaminami Fumi Uchimura Yoshinari Okamoto Tadashi Okawara Mitsuru Furukawa 《Journal of heterocyclic chemistry》1992,29(4):825-829
Novel tricyclic ring systems, irmdazo[3,4-d]pyridazino[4,5-b][1,4]thiazines 3 , imidazo[2,1-b]pyridazino[4,5-e][1,3,4]thiadiazines 15 and 18 were prepared by the reaction of 5-amino-4-chloropyridazin-3(2H)-ones 1 and 5(4)-(1-methylhydrazino)-4(5)-chloropyridazin-3(2H)-ones 13 (16) with isothiocyanates 2 and 7 . 相似文献
1000.
The optically active 1,3,5---triol was synthesized starting from ()-(-)-malic acid with complete stereoselection, based on the stereoselective reduction of cyclic β-keto acetal and successive transthioacetalization. 相似文献