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41.
Mikio Hori Tadashi Kataoka Hiroshi Shimizu Eiji Imai Yukiharu Matsumoto Iwao Miura 《Tetrahedron letters》1981,22(13):1259-1262
The novel ring transformation reactions were found in the reactions of 1,3,7,9-tetra-alkyl-8,9-dihydroxanthines and acetylenic compounds. The reaction of the dihydroxanthine with DMAD gave a propellane type compound and with methyl propiolate afforded the similar type compound and a pyrimido[4,5-b]diazepine derivative. The mechanism of these reactions was also discussed. 相似文献
42.
A simple method is presented for measuring the heat of mixing and the heat of vaporization of volatile liquids at temperatures below their boiling point. It consists in introducing liquids by a microsyringe into a nearly closed cell of the DSC. The relative standard deviation for 4 to 5 runs is ca. 5% for heat of mixing and ca. 2% for heat of vaporization. 相似文献
43.
The reaction of glycine with NBD-F (4-fluoro-7-nitrobenzo-2-oxa-1,3-diazole) is investigated to establish conditions that provide a high formation rate of NBD-glycine and a low hydrolysis rate of the reagent. The reaction rate increases with higher temperature, larger contents of organic solvent and a sodium borate buffer. The use of borate buffer decreases ther ate of hydrolysis of the reagent. For low-molecular-weight amines, condition for a suitable liquid chromatographic postcolumn reactor include a high content of acetonitrile and 0.1 M sodium borate (pH 8.0–8.5). For proteins, separated by molecular-exclusion chromatography, water is needed for sensitive reactions. Suitable postcolumn reactor conditions include borate buffer (pH 7.9) containing 0.1 M potassium chloride, a 0.02% (w/v) NBD-F solution in acetonitrile with reaction at 50°C for about 45 s. The detection limits for human serum albumin, β-lactoglobulin and myoglobin are 6.6 pmol, 8.4 pmol and 11 pmol, respectively. 相似文献
44.
Takanori Sugimoto 《Tetrahedron letters》2004,45(2):335-338
Circadian rhythmic plant leaf movement, called nyctinasty, is controlled by a time-course change in the internal concentration of the leaf-movement factor in the plant body. We report that specific binding protein (210 and 180 kDa) for a leaf-movement factor, potassium lespedezate, is contained in the plasma membrane of the plant motor cell. These proteins would be potential receptors for leaf-movement factor to control the leaf movement. 相似文献
45.
46.
Murakami M Usui I Hasegawa M Matsuda T 《Journal of the American Chemical Society》2005,127(5):1366-1367
Cyclobutene, having a pinacolatoboryl group at the 3-position, was prepared by the reaction of trimethyl borate with a cyclobutenyl anion, which was generated by reductive lithiation of 3-(phenylselenyl)cyclobutene. Its thermal ring-opening reaction provided (Z)-1-borylbuta-1,3-diene selectively despite the arising steric congestion. The contrasteric behavior was accounted for by assuming an electron-accepting interaction of the vacant boron p orbital with the distorted breaking sigma orbital in the inward transition state. 相似文献
47.
Toshihiro Otsuki Masa-Aki Kakimoto Yoshio Imai 《Journal of polymer science. Part A, Polymer chemistry》1989,27(5):1775-1780
Wholly aromatic random copolyamides of high molecular weights were prepared by the high-temperature solution polycondensation of an aromatic diisocyanate, 4,4′-methylenedi(phenyl isocyanate) or 2,4-tolylene diisocyanate, with a mixture of isophthalic acid and 4,4′-oxydibenzoic acid. Glass transition temperatures of the polyamides and copolyamides were between 229 and 273°C; this depended on the combination of diisocyanates and dicarboxylic acids used. These aromatic copolyamides showed better solubility in various organic solvents and reduced crystallinity, compared to the corresponding homopolyamides. The copolyamides prepared from 2,4-tolylene diisocyanate had greater solubility and higher glass transition temperatures than those obtained from 4,4′-methylenedi(phenyl isocyanate). 相似文献
48.
We have found a novel type of morphological chiral tuning on inorganic helical crystals through stereochemical recognition of organic molecules. Helical forms consisting of twisted twins emerged from triclinic crystals under diffusion-limited conditions. The proportion of the right- and left-handed helices was precisely tuned with the addition of a specified amount of chiral molecules, such as d- and l-glutamic acids. The chiral molecules recognized the enantiomeric surface of the triclinic crystal and then changed the growth behavior of the helical morphology. As a result, the microscopic chiral information, at a molecular level, was amplified into the macroscopic helices consisting of inorganic achiral components. 相似文献
49.
Mitsuru Ueda Masami Takahashi Yoshio Imai Charles U. Pittman 《Journal of polymer science. Part A, Polymer chemistry》1982,20(10):2819-2828
The kinetics of α-methylene-γ-butyrolactone (α-MBL) homopolymerization was investigated in N,N-dimethylformamide (DMF) with azobis(isobutyronitrile) as initiator. The rate of polymerization (Rp) was expresed by Rp = k[AIBN]0.54[α-MBL]1.1 and the overall activation energy was calculated as 76.1 kJ/mol. Kinetic constants for α-MBL polymerization were obtained as follows: kp/kt1/2 = 0.161 L1/2 mol?1/2·s?1/2; 2fkd = 2.18 × 10?5 s?1. The relative reactivity ratios of α-MBL(M2) copolymerization with styrene (r1 = 0.14, r2 = 0.87) were obtained. Applying the Q–e scheme led to Q = 2.2 and e = 0.65. These Q and e values for α-MBL are higher than those for MMA 相似文献
50.
Enantio-uracil dinucleotide 5, which consists of two l-uridylic acids and one pyrophosphate, was synthesized for the first time in our laboratory. Benzolyated l-uridine was prepared by a stereoselective glycosylation of silylated uracil with l-1-O-acetyl-2,3,5-tri-O-benzoylribose (l-ABR 7). After deprotection, l-uridine 9 was converted to P1,P4-di(l-uridine 5′-) tetraphosphate tetrasodium salt (l-UP4U 5) by treatment of l-UMP morpholidate 10c with triethylammonium pyrophosphate (TEA-PPi 11b). Spectral data of synthesized l-UP4U 5 are given in the references. All spectral data were identical with those of UP4U 3 except the specific rotation, which showed a positive value compared to UP4U 3 having a negative value. Furthermore, the separation by chiral column chromatography was investigated. 相似文献