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981.
982.
Hiroki Wada Lili Cheng Ji Jiang Zhigan Jiang Jun Xie Tao Hu Hitesh Sanganee Tim Luker 《Tetrahedron letters》2012,53(14):1720-1724
2,4-Disubstituted-5-fluoropyrimidine is a biologically active molecular core seen in various anticancer agents such as 5-fluorouracil (5-FU). As part of a programme aimed at discovering kinase inhibitors, routes to two series of novel compounds (5-fluoropyrimidine-2-carboxamides and 5-fluoropyrimidine-4-carboxamides) were successfully executed. For the first series, regioselective substitution at the 4-position of the pyrimidine with an amine (HNR1R2) was achieved, followed by preparation of the amide at the 2-position. The route to the second series involved introduction of the methoxy protecting group at the 4-position, which allowed subsequent amine substitution to occur at the 2-position. The 4-amide substituent was finally introduced by direct conversion of the 4-methoxy into a 4-chloro group followed by transformation into an amide by palladium catalysis. 相似文献
983.
Akira Masuoka 《Proceedings of the American Mathematical Society》2001,129(11):3185-3192
To answer in the negative a conjecture of Kaplansky, four recent papers independently constructed four families of Hopf algebras of fixed finite dimension, each of which consisted of infinitely many isomorphism classes. We defend nevertheless the negated conjecture by proving that the Hopf algebras in each family are cocycle deformations of each other.
984.
Naoki Yasuda Shigeyuki Yamamoto Yuji Wada Shozo Yanagida 《Journal of polymer science. Part A, Polymer chemistry》2001,39(24):4196-4205
Photochemical reactions of aromatic azide groups were applied for a novel photosensitive silicone ladder polymer, that is, partially vinyl‐substituted polyphenylsilsesquioxane sensitized with aromatic bisazide compounds as a photocrosslinker. The photocrosslinking reaction in this system was investigated from the viewpoint of the efficiency of the photocrosslinker, that is, the ratio of the photocrosslinker consumed for crosslinking. The numbers of photodecomposed azide groups and crosslinks in the polymer were determined by Fourier transform infrared measurements. At a higher bisazide concentration, the predominant reaction of nitrenes formed as the intermediary radical by the photolysis of azide was a coupling reaction that could not contribute to the gelation of the polymer. The ratio of the bisazide compound consumed for crosslinking showed the highest value at its concentration of 3 wt % and decreased with the addition of a larger amount. The semiempirical molecular orbital calculations were applied to the theoretical analysis of the photoreaction of nitrenes using phenylnitrene as a model structure. The calculation results indicated that the coupling reaction of nitrenes should proceed more easily than the photocrosslinking reaction in N2 atmosphere, and the fact that the oxidation of nitrenes should proceed exclusively in the atmosphere including O2 agreed with the experimental results. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4196–4205, 2001 相似文献
985.
Photocatalytic Activity and Photo-Induced Wettability Conversion of TiO2 Thin Film Prepared by Sol-Gel Process on a Soda-Lime Glass 总被引:17,自引:0,他引:17
Watanabe Toshiya Fukayama Shigemichi Miyauchi Masahiro Fujishima Akira Hashimoto Kazuhito 《Journal of Sol-Gel Science and Technology》2000,19(1-3):71-76
We have developed the transparent photoactive TiO2 thin film coated on soda lime glass (SLG) by sol-gel process. Titanium dioxide thin films coated on SLG exhibit lower photocatalytic activity due to the thermal diffusion of Na ion from the SLG substrate. Thin SiO2 film precoating is very effective to prevent the thermal diffusion of Na ion. We have evaluated the photocatalytic decomposition of gaseous acetaldehyde and the photo-induced surface wettability of TiO2 films with and without SiO2 precoating layer. As expected, the TiO2 film on SiO2/SLG is more photoactive to decompose acetaldehyde than that on SLG. However, as for wettability conversion, there was little difference in the conversion rate between TiO2 film without SiO2, and TiO2 film with SiO2. Different dependence of Na ion diffusion on two kinds of photo-induced reaction on TiO2 is discussed based on the difference of the photo-induced reaction mechanism. 相似文献
986.
The reaction of N,C-protected peptides containing glycine residues with peracetic acid in the presence of a ruthenium catalyst gives -ketoamides derived from the oxidation at the C position of the glycine residues selectively. 相似文献
987.
Takumi Watanabe Yuji Tsunoda Akira Matsuo Kenji Sugiyama Akira Hirao 《Macromolecular Symposia》2006,240(1):23-30
A series of dendrimer-like star-branched poly(methyl methacrylate)s (PMMA)s of generations consisting of four branched segments at each junction have been successfully synthesized by developing an iterative methodology. It involves two reaction steps in each iterative reaction sequence, (a) a coupling reaction of the α-functionalized living anionic PMMA with four tert-butyldimethylsilyloxymethylphenyl (SMP) groups with benzy bromide (BnBr)-chain-functionalized PMMA and (b) a transformation of SMP group into BnBr functionality. By repeating the reaction sequence thrice, the above-mentioned dendrimer-like star-branched (PMMA)s of up to third-generation made up of 4, 20, and 84 PMMA segments and 16, 64, and 256 BnBr termini were synthesized by the first, second, and third iterative processes, respectively. The resulting polymers all were well-defined in branched architecture and precisely controlled in chain length. 相似文献
988.
In order to achieve the successive synthesis of star-branched polymers, we have developed a new iterative methodology which involves only three sets of the reactions in each iterative process: (a) a coupling reaction of a living anionic polymer with 1,1-bis(3-chloromethylphenyl)ethylene to prepare a DPE-chain-functionalized polymer, (b) an addition reaction of sec-BuLi to the DPE-chain-functionalized polymer, followed by treatment with 1-(4-(4-bromobutyl)phenyl)-1-phenylethylene to prepare a new DPE-chain-functionalized polymer whose DPE is separated by four methylene units from the main chain, and (c) a coupling reaction of 1,1-bis(3-chloromethylphenyl)ethylene with the polymer anion derived from the newly prepared DPE-chain-functionalized polymer and sec-BuLi. With this methodology, a series of well-defined 4-arm, 8-arm, and 16-arm regular star-branched polystyrenes as well as 4-arm A2B2, 8-arm A4B4, and 16-arm A8B8 asymmetric star-branched polymers comprising polystyrene and poly(α-methylstyrene) segments have been successively synthesized. 相似文献
989.
Toru Katsumata Masaharu Satoh Jun Wada Masashi Shiotsuki Fumio Sanda Toshio Masuda 《Macromolecular rapid communications》2006,27(15):1206-1211
Summary: 2,2,6,6‐Tetramethylpiperidine 1‐oxyl (TEMPO)‐containing N‐propargylamide HCCCH2NHCO‐4‐TEMPO ( 1 ), propargyl ester HCCCH2OCO‐4‐TEMPO ( 2 ), phenylacetylene derivative HCCC6H3‐3,4‐(CO2‐4‐TEMPO)2 ( 3 ), and norbornene diester monomers, NB‐2,3‐exo,exo‐(CH2OCO‐4‐TEMPO)2 ( 4 ), NB‐2,3‐endo,exo‐(COO‐4‐TEMPO)2 ( 5a ), NB‐2,3‐endo,endo‐(COO‐4‐TEMPO)2 ( 5b ) (NB = norbornene, TEMPO = 2,2,6,6‐tetramethyl‐1‐piperidinyloxyl) were synthesized and polymerized with rhodium and ruthenium catalysts. Monomers 2 , 5a , and 5b gave polymers with number‐average molecular weights of 47 000–185 000 in 59–100% yields, while 1 , 3 , and 4 gave polymers insoluble in common organic solvents in 88–100% yields. The capacities of cells fabricated with poly( 1 ), poly( 2 ), and poly( 3 ) were 67, 82, and 23 Ah · kg−1 based on the weight, respectively. The capacity of poly( 5a )‐based cell reached the theoretical value (109 Ah · kg−1) of the polymer.
990.
Hydrogen effects for propylene polymerization were investigated with ultra low TiCl3 loading MgCl2-supported catalysts in which the electric states of Ti species can be almost uniform. Hydrogen did not affect the catalyst activity, while the efficiency of hydrogen as a chain transfer agent was found to depend on the Ti content of the catalyst and the stereospecificity of the polymerization sites: Hydrogen was effective for isospecific sites independent of Ti contents, but inert for aspecific sites only at the extremely low Ti content. These results were explained within the island model, where isospecific sites may be located in the islands with other Ti species in their surroundings acting, as a steric hindrance for isospecific polymerization and as hydrogen dissociation sites after deactivation. Most of the aspecific sites should be isolated only at the extremely low Ti content. These isolated sites have no other Ti species in their surroundings, i.e. no hydrogen dissociation sites, and are inert to hydrogen. 相似文献