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251.
Sekine M Kadokura M Satoh T Seio K Wada T Fischer U Sumpter V Lührmann R 《The Journal of organic chemistry》1996,61(13):4412-4422
The 5'-terminal TMG-capped triribonucleotide, m(3)(2,2,7)G(5)(')pppAmpUmpA, has been synthesized by condensation of an appropriately protected triribonucleotide derivative of ppAmpUmpA with a new TMG-capping reagent. During this total synthesis, it was found that the regioselective 2'-O-methylation of 3',5'-O-(1,1,3,3-tetraisopropyldisiloxane-1,3-diyl)-N-(4-monomethoxytrityl)adenosine was achieved by use of MeI/Ag(2)O without affecting the base moiety. A new route to 2-N,2-N-dimethylguanosine from guanosine via a three-step reaction has also been developed by reductive methylation using paraformaldehyde and sodium cyanoborohydride. These key intermediates were used as starting materials for the construction of a fully protected derivative of pAmpUmpA and a TMG-capping reagent of Im-pm(3)(2,2,7)G. The target TMG-capped tetramer, m(3)(2,2,7)G(5)(')pppAmpUmpA, was synthesized by condensation of a partially protected triribonucleotide 5'-terminal diphosphate species, ppA(MMTr)mpUmpA, with Im-pm(3)(2,2,7)G followed by treatment with 80% acetic acid. The structure of m(3)(2,2,7)G(5)(')pppAmpUmpA was characterized by (1)H and (31)P NMR spectroscopy as well as enzymatic assay using snake venom phosphodiesterase, calf intestinal phosphatase, and nuclease P1. 相似文献
252.
This paper deals with the synthesis of m32,2,7G5′pppAmpUmpApd(CpTpTpApCpCpT), a 5′-TMG-capped RNA-DNA chimeric oligonucleotide, which is expected to be conveyed to the nucleus by snurportin 1, a nuclear-transport protein. This 5′-TMG-capped RNA-DNA chimeric molecule was synthesized by the enzymatic condensation of m32,2,7G5′pppAmpUmpA with A5′ppd(CpTpTpApCpCpT) in the presence of RNA ligase. An inherent serious side reaction was disclosed in the 5′-adenylation of d(CpTpTpApCpCpT) on the solid support, but the use of an active ester intermediate as the pA donor gave an improved result. 相似文献
253.
Mikiharu Kamachi Kohji Tanaka Yoko Kuwae 《Journal of polymer science. Part A, Polymer chemistry》1986,24(5):925-929
ESR studies on the radical polymerization of vinyl ethers were performed from ?50°C to room temperature using di-tert-butylperoxide as a photoinitiator. Well resolved ESR spectra were assigned to propagating radicals of vinyl ethers. Their hyperfine splitting constants due to α-proton were about 16 G, being smaller than those of ethyl acrylate and vinyl acetate. The smaller constants is ascribed to a deviation of the propagating radicals from sp2 hybrid structure. The reason why high polymers are not obtained from vinyl ethers by radical polymerization is discussed on the basis of information from the ESR studies. 相似文献
254.
Yoshio Iwakura Yohji Imai Kohji Yagi 《Journal of polymer science. Part A, Polymer chemistry》1968,6(4):801-807
Grafting of methyl methacrylate onto poly(6-methacryloyl-D -galactose) was very rapid, and the increase in weight reached about 1500% after 2–3 min. The maximum number of branches of the graft copolymers obtained was about 50. In the closest position two adjacent grafted branches were separated from each other by about 45–50 units of 6-methacryloyl-D -galactose on the average. Susceptibility of the various polymers containing sugar residues to grafting was compared, and the importance of the hemiacetal group in the grafting was revealed. Solubility of the backbone polymer in water was also important for rapid grafting by the ceric ion method. 相似文献
255.
Kenichi Miyata Ryuji Tamamushi Haruhiko Taguchi Kohji Seio Mitsuo Sekine 《Tetrahedron letters》2004,45(51):9365-9368
Modified oligodeoxynucleotides incorporating 4-N-(N-arylcarbamoyl)-dC derivatives 1a-c were synthesized. The 1H NMR spectra of 1a-c suggest that the carbamoyl group forms an intramolecular hydrogen bond with the cytosine ring nitrogen atom so that formation of a Watson-Crick base pair with the complementary guanine base is inhibited. The hybridization properties of oligodeoxynucleotides containing 1a-c were investigated by use of Tm analysis. The hybridization properties of 4-N-(N-phenylcarbamoyl)-dC (1a) were similar to those of 4-N-(N-alkylcarbamoyl)-dC derivatives reported previously. In sharp contrast to 1a, it turned out that 4-N-(N-napht-1-yl) and (N-quionol-5-yl)-dC (1b,c) have a unique property as a universal base. 相似文献
256.
Tsuneo Okubo Hisanori Ishiki Hiroshi Kimura Megumi Chiyoda Kohji Yoshinaga 《Colloid and polymer science》2002,280(5):446-453
Rigidity (G) of colloidal crystals in organic solvents of acetonitrile and nitrobenzene has been measured by reflection spectroscopy
in sedimentation equilibrium. The colloidal spheres used are the silica spheres (136 nm in diameter) modified on their surfaces
with polymers, poly(maleic anhydride-co-styrene) [P(MA-ST)], poly(methyl methacrylate) (PMMA), or polystyrene (PST). Log G increases linearly with the slope of unity as log N (number density of colloidal spheres) increases. The mean values of the b-factor, which is the fluctuation parameter in crystal lattices and should be smaller than 0.1 according to the Lindeman's
rule, are 0.045±0.003, 0.039±0.007, and 0.038±0.003 for P(MA-ST)/SiO2, PMMA/SiO2, and PST/SiO2, respectively. These values are larger than that of colloidal crystals of mother silica spheres in the deionized aqueous
suspension, 0.028. These results support the important role of the excluded volume effects
from the polymer layers formed around the silica surfaces. However, contribution of the excluded volume effects from the electrical double layers formed around the spheres in the organic solvents is also effective in the colloidal crystallization.
Electronic Publication 相似文献
257.
[reaction: see text] A new route to N-unprotected deoxynucleoside 3'-phosphoramidite building blocks by use of highly selective N-deacylation of commercially available N-acylated deoxynucleoside 3'-phosphoramidites is described. These compounds could be readily converted to other types of N-protected species by facile N-acylations with acylating reagents. 相似文献
258.
Kohji Hasunuma Kazuhiko Furukawa Kanako Funadera Mamoru Kubota Masakatsu Watanabe 《Photochemistry and photobiology》1987,46(4):531-535
Binding of GTP-binding proteins with [35 S]GTP7S in the extract containing membrane components of Lemna paucicostata 441 was inhibited by red or far red light by 20 to 25%, but blue light showed no or little effect. The plant used for the preparation of the extract was subjected to single darkness for 8 h, as both red and far red light inhibit flowering. The extract treated with 1% Lubrol was fractionated by gel filtration. Four species of GTP-binding proteins, GL1, GL2, GL3 and GL4 were detected with Km values 3, 7, 80 and 4 n M , respectively. GL1, GL2 and GL3 were ADP-ribosylated by pertussis toxin. The extract activated by [35 S]GTP-γS in darkness, under red light or under far red light was treated with 1% Lubrol and subsequent gel filtration of the extracts made it possible to detect GTP-binding protein with a small molecular weight only in an extract labeled in darkness. The reduction in the molecular weight of GTP-binding protein from the larger molecule associated with the binding of [35 S]GTPγS was confirmed by rechromatography of the larger molecule activated by [35 S]GTPγS in darkness. The binding of GL2 and/or GL3 with [35 S]GTPγS was suggested to be inhibited by red or far red light. 相似文献
259.
Takumi Taninaka Hideaki Uemura Kohji Iwamoto Yuji Minoura 《Journal of polymer science. Part A, Polymer chemistry》1978,16(7):1549-1561
Effects of pentavalent phosphorus compounds on the radical polymerization of methyl methacrylate (MMA) and styrene (St) were studied. Phosphorus oxychloride (Cl3P?O) and phenyl-phosphonic dichloride (C6H5Cl2P?O) were used. Polymerization was carried out in benzene at 50°C by the standard solution method, α,α′-azobisisobutyronitrile (AIBN) being used as the initiator. In the polymerization of MMA, both phosphorus compounds increased the rate of polymerization. NMR spectral data suggested that this increasing effect was due to the complex formation between each phosphorus compound and MMA monomer. In the case of polymerization of St, NMR data also indicated the formation of a complex between the phosphorus compound and St monomer. Both phosphorus compounds showed an increasing effect for the rate of polymerization. Though these increasing effects could be explained by the complex formation, the polymerization of St in the presence of Cl3P?O was especially found to be due to the cationic polymerization initiated simultaneously by Cl3P?O in addition to the radical polymerization. These phosphorus compounds acted as chain-transfer agents in both polymerization systems. The parameters (Qtr,etr) which indicate the reactivity of a chain-transfer agent were calculated from the observed values of chain-transfer constant for both polymerization systems. 相似文献
260.
Kohji Yanagawa 《Proceedings of the American Mathematical Society》1999,127(2):377-383
Let be a monomial ideal of . Bayer-Peeva-Sturmfels studied a subcomplex of the Taylor resolution, defined by a simplicial complex . They proved that if is generic (i.e., no variable appears with the same non-zero exponent in two distinct monomials which are minimal generators), then is the minimal free resolution of , where is the Scarf complex of . In this paper, we prove the following: for a generic (in the above sense) monomial ideal and each integer , there is an embedded prime of . Thus a generic monomial ideal with no embedded primes is Cohen-Macaulay (in this case, is shellable). We also study a non-generic monomial ideal whose minimal free resolution is for some . In particular, we prove that if all associated primes of have the same height, then is Cohen-Macaulay and is pure and strongly connected.