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991.
Kazuo Hara Yukio Imanishi Toshinobu Higashimura Mikiharu Kamachi 《Journal of polymer science. Part A, Polymer chemistry》1971,9(10):2933-2948
1-Vinylcyclohexene (VCH), which has one of the double bonds in the ring and the other outside the ring, was synthesized and polymerized by cationic catalysts. The reactivity of VCH was very large in the polymerizations catalyzed by boron trifluoride etherate (BF3OEt2) and stannic chloride–trichloroacetic acid complex. Similar to other cyclic dienes, the polymerization of VCH was a nonstationary reaction having a very fast initiation step. The polymerization proceeded by either a 1,2- or a 1,4-propagation mode in which vinyl group was always involved. Particularly when BF3OEt2 was used as a catalyst, an intramolecular proton or an intramolecular hydride ion transfer reaction took place, resulting in the formation of methyl groups in the polymer. The degree of polymerization of polymer formed was about 10. This indicates the preponderance of monomer transfer reaction. To investigate the reason for the high reactivity of cyclic dienes, cationic copolymerizations of VCH and 3-methyl-cis/trans-1,3-pentadiene (cis/trans-MPD) was carried out. The relative reactivity of monomers decreased in the order VCH > trans-MPD > cis-MPD. On the other hand, the resonance stabilization of monomers decreased in the order VCH > trans-MPD > cis-MPD. Therefore, it could be considered that the monomer reactivity is mainly determined by the stability of carbonium ion intermediate. The relative stability of carbonium ion must be VCH > trans-MPD > cis-MPD. Thus the influence of the conformation of ion on its stability was clearly demonstrated. 相似文献
992.
Kazuo Soga Yoshiji Takano Shigeo Go Tominaga Keii 《Journal of polymer science. Part A, Polymer chemistry》1967,5(11):2815-2823
The influence of SeOCl2 on the polymerization of propylene by TiCl3–Al(C2H5)3, and the temperature dependence of the stereospecificity of the catalyst, TiCl3–Al(C2H5)3, have been investigated. SeOCl2 decreases the rate of polymerization and increase the stereospecificity of the catalyst, which could be explained on the basis of a decrease of the concentration of Al(C2H5)3 accompanied by a reaction between Al(C2H5)3 and SeOCl2. On the other hand, the stereospecificity of the catalyst, TiCl3–Al(C2H5)3, increases gradually with a decrease in polymerization temperature from 40 to 0°C. From these results, we conclude that SeOCl2 exerts no essential influence on the polymerization of propylene by TiCl3–Al(C2H5)3, and that the stereospecificity of the catalyst is attributed mainly to the reducing ability of the organometallic compound. 相似文献
993.
Motokazu Uemura Kazuhiko Take Kazuo Isobe Tatsuya Minami Yuji Hayashi 《Tetrahedron》1985,41(24):5771-5778
(3-Methoxybenzylalcohol)chromium tricarbonyl (10) and (7-methoxy-1-tetralol)chromium tricarbonyl (12) are selectively lithiated at the 4- and 6-positions, respectively, by treatment with n-BuLi-TMEDA. Since the directed lithiation of the corresponding chromium free arenes normally proceeds at the 2-and 8-positions, complementarily substituted arenes can be prepared by using the chromium tricarbonyl complexes. The difierent position of lithiation is explained by the relative configuration of the chromium tricarbonyl group in the (arene)Cr(CO)3 and electrostatic factors. Some anthraquinones, 31,36,42, and 7-hydroxycalamenenes, 43, have been synthesized through the stereo- and regioselective introduction of substituents by means of(η6-arene)chromium tricarbonyl complexes. 相似文献
994.
Orii T Okada Y Takeuchi K Ichihashi M Kondow T 《The Journal of chemical physics》2004,121(19):9406-9416
An incorporation of ND(3) into protonated ammonia cluster ions NH(4)(+)(NH(3))(n-1) (n=3-9), together with a dissociation of the cluster ions, was observed in the collision of the cluster with ND(3) at collision energies ranging from 0.04 to 1.4 eV in the center-of-mass frame. The branching fractions of the cluster ion species produced in the reactions were obtained as a function of the collision energy. The branching fractions of the incorporation products were successfully explained in terms of the Rice-Ramsperger-Kassel (RRK) theory at collision energies lower than the binding energy of the cluster ion. In addition, the internal energy distributions of the parent cluster ions were determined, and found to be in good agreement with those predicted using the evaporative ensemble model. In incorporations at collision energies lower than the binding energy of the cluster ion, all of the collision energy was transferred to the internal energy of the cluster ions; subsequently, an evaporation of ammonia molecules occurred in an equilibrium process after a complete energy redistribution in the clusters. In contrast, at collision energies higher than the binding energy of the cluster ion, a release of an ammonia molecule from the incorporation products occurred in a nonequilibrium process. The transition from the complex mode to the direct mode in the incorporation was observed at collision energies approximately equal to the binding energy. On the other hand, the collision energy dependence of the cross sections for the dissociation and for a nonreactive collision were estimated by a RRK simulation in which the collision energy transfer was interpreted by using the classical hard-sphere collision model. A relationship between reactivity and reaction modes in the collision of NH(4)(+)(NH(3))(4) with ND(3) is discussed via a comparison of the experimental results with the RRK simulation. 相似文献
995.
Kazuo Sugiyama Tadao Nakaya Minoru Imoto 《Journal of polymer science. Part A, Polymer chemistry》1971,9(9):2689-2702
The polymerization of acrylonitrile (AN) initiated by the system of tetramethyl tetrazene (TMT) and bromoacetic acid (BA) in dimethylformamide (DMF) was studied. The TMT–BA system could initiate the polymerization of AN more easily than TMT alone. The polymerization was confirmed to proceed through a radical mechanism. The initial rate of polymerization Rp was expressed by the equation: Rp = [TMT]0.62-[BA]0.5[AN]1.5. The overall activation energy for the polymerization was estimated as 9.4 kcal/mole. In the absence of monomer, the reaction of TMT with BA in DMF was also studied kinetically by measuring the evolution of nitrogen gas. The reaction was first-order in TMT and first-order in BA; the rate data at 49°C were k2 = 9.1 × 10?2l./mole-sec., ΔH? = 17.0 kcal/mole, and ΔS? = ? 6.6 eu. In addition, the treatment of TMT with BA in benzene led to the formation of tetramethylhydrazine radical cation, which was identified by its ESR spectrum. On the other hand, the relatively strong interaction between TMT and DMF was observed by absorption spectrophotometry. 相似文献
996.
Kazuo Soga Kazuya Uenishi Sakuji Ikeda 《Journal of polymer science. Part A, Polymer chemistry》1979,17(2):415-423
The homopolymerization of propylene oxide was first conducted at 80°C in the absence of any solvent by using various metal salts of acetic acid and it was found that Mg(OAc)2, Cr(OAc)3, Mn(OAc)2, Co(OAc)2, Ni(OAc)2, Zn(OAc)2, and Sn(OAc)2 were effective for the polymerization. The copolymerization of propylene oxide and carbon dioxide was next examined by using these effective metal salts of acetic acid as catalysts. Most of these were effective also for the copolymerization. The nature of the polymer obtained was strongly dependent on the catalyst used. Co(OAc)2 and Zn(OAc)2 gave an alternate copolymer of propylene oxide and carbon dioxide, Mg(OAc)2, Cr(OAc)3, and Ni(OAc)2 gave a random copolymer, while Sn(OAc)2 gave a homopolymer of propylene oxide. Then the copolymerization of propylene oxide and carbon dioxide was kinetically investigated in some detail by using Co(OAc)2 as a catalyst. On the basis of the results obtained, a plausible mechanism was proposed for both the homopolymerization of propylene oxide and copolymerization of propylene oxide and carbon dioxide. 相似文献
997.
Porntida Yampayont Masaru Iizuka Kazuo Ito Tipaporn Limpaseni 《Journal of inclusion phenomena and macrocyclic chemistry》2006,56(1-2):203-207
A Cyclodextrin (CDs) producing bacteria was isolated from waste of starch factory in Thailand and identified as Bacillus circulans by biochemical characterization and Paenibacillus sp. by 16S rRNA. The Paenibacillus grew and produced cyclodextrin glycosyltransferase (CGTase) at temperature range 37–45 °C. The optimum culturing conditions for highest CD-forming activity were pH 10.0 and 40 °C for 72 h in Horikoshi broth containing 0.5% soluble starch. The CGTase was partially purified by starch absorption, with 64% recovery and purification fold of 27. The optimum temperatures for dextrinizing and CD-forming activity were 70 and 50–55 °C. At the optimum temperature, the optimum pH for dextrinizing activity was 6.0, while CD-forming activity was 7.0. When the enzyme was incubated for 1 h at different temperatures, CD-forming activity retained its full activity up to 70 °C while dextrinizing activity dropped to 60%. Cyclodextrin products analyzed by HPLC was α:β=1:1, temperature of reaction mixture can affect the yield of CDs. 相似文献
998.
Control of life cycle of mouse adipogenic 3T3-L1 cells by dietary lipids and metabolic factors 总被引:2,自引:0,他引:2
Nishimura K Hatano Y Setoyama T Tsumagari H Miyashita K Lu S Jisaka M Nagaya T Yokota K 《Applied biochemistry and biotechnology》2004,118(1-3):97-114
Adipocytes function not only as in the storage and mobilization of lipids but also as endocrine cells by secreting tumor necrosis
factor-α (TNF-α), free fatty acids, and other cytokines. To study the effects of dietary lipids and metabolic factors on the
control of the life cycle of adipocytes, we utilized mouse 3T3-L1 preadipocytes that could be induced to differentiate into
adipocytes. To evaluate the role of endogenous prostaglandins (PGs) in the adipogenic changes, we examined the effect of specific
inhibitors of cyclooxygenase (COX). SC-560, a specific COX-1 inhibitor, suppressed adipogenesis dose dependently, suggesting
a role of constitutive COX-1 in the endogenous synthesis of PGs, including PGJ2 derivatives formed by mature adipocytes with the ability to promote adipogenesis. NS-398, a COX-2 inhibitor, had little influence
on the maturation processes. Both COX inhibitors were effective in stimulating apoptosis of preadipocytes induced by TNF-α,
indicating that both PGE2 and PGF2α produced by preadipocytes through the action of both COX isoforms serve as survival factors. However, the effect of both
inhibitors was negligible for the proliferation of preadipocytes. Moreover, conjugated linolenic acid from bitter gourd at
lower concentrations that was without effects by itself synergistically stimulated TNF-α-induced apoptosis. Therefore, dietary
lipid factors are capable of controlling the life cycle of adipocytes together with metabolic factors. 相似文献
999.
Tokuo Itoh Kazuo Ono Tomokazu Sugawara Yoshihisa Mizuno 《Journal of heterocyclic chemistry》1982,19(3):513-517
Reactions of some imidazo[4,5-b]pyridine 4-oxides with phosphoryl chloride are described. Treatment of N-1-substituted imidazo[4,5-b]pyridine 4-oxides with phosphoryl chloride led to the predominant formation of 7-chloro derivatives. This feature was successfully applied to the preparation of a chloroimidazo[4,5-b]pyridine nucleoside, which served as an important precursor of 1-deazaadenosine. 相似文献
1000.
This study was carried out to investigate the antioxidant activity of propofol (2,6-diisopropylphenol) and its related compounds, butylated hydroxyanisole (BHA), 2,6-dimethylphenol, 2,6-di-t-butylphenol, and their dimeric compounds. The degree of antioxidant activity was evaluated based on the degree of peroxidation induced with Fe-ascorbic acid in egg phosphatidylcholine through the determination of thiobarbituric acid-reactive substances (TBARS) formed during peroxidation. Their antioxidant activities were in the order of dipropofol>di(2,6-di-t-butylphenol)>diBHA>di(2,6-dimethylphenol). Dipropofol, a dimeric compound of propofol, showed the highest antioxidant activities. Dimeric compounds had higher activities than monomeric compounds, and the 1,1-diphenyl-p-picryhydrazyl-trapping ability of dimeric compounds was also greater than those of monomeric compounds (4-10-fold). These results suggest that dimeric phenols may increase their antioxidant activities along with increments in the conjugation system and play a inhibitory role in the propagation of free radical chain reactions. 相似文献