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101.
M. Kando S. Masuda A. Zhidkov A. Yamazaki H. Kotaki S. Kondo T. Homma S. Kanazawa K. Nakajima L. -M. Chen J. Ma Y. Hayashi M. Mori H. Kiriyama Y. Akahane N. Inoue H. Ueda Y. Nakai K. Tsuji Y. Yamamoto J. Koga T. Hosokai K. Kinoshita A. Maekawa M. Uesaka S. V. Bulanov T. Zh. Esirkepov M. Yamagiwa T. Kimura K. Yamakawa T. Tajima 《Laser Physics》2006,16(4):576-580
We present the results of electron generation experiments conducted at the Advanced Photon Research Center, Japan Atomic Energy Research Institute, using 23-fs relativistically intense 20-TW tightly focused laser pulses with underdense plasma. We observed electron energies up to 40 MeV characterized by a two-temperature Maxwell distribution. With the help of particle-in-cell simulations, we found that these are due to different plasma wave-breaking processes. A charge of 5 nC/shot was obtained at a small solid angle, which corresponds to high peak current generation. 相似文献
102.
Masamitsu Shirai Haruyuki Ishida Makoto Tanaka 《Journal of Polymer Science.Polymer Physics》1988,26(10):2075-2091
The polymers which have glyme units as alkali cation binding sites and photodimerizable cinnamoyl units were prepared by the radical polymerization of corresponding monomers. The alkali cation binding ability and selectivity of the polymers, which were studied by a method of picrate salts extraction, were strongly dependent on the length of glyme chains. When irradiated with ultraviolet light, the cinnamoyl groups caused dimerization in dilute solutions. Although the photodimerization of the polymers with relatively short glyme chains enhanced their cation binding ability, the photodimerization of the polymers bearing long glyme chains reduced their cation binding ability. The use of alkali metal cations as templates emphasized the effect of photodimerization on the cation binding properties. The effect of alkali metal cations on the quantum yields of the photodimerization of the polymers showed that two or more benzodiglyme units took part in the binding of one cation. The polymers bearing benzodiglymes, crown ethers, and cinnamoyl moieties were also prepared by the radical copolymerization of the corresponding monomers. It was found that the crown ether units of the copolymers predominantly participated in the cation binding. The photodimerization of the copolymers with suitable alkali metal cations as templates strongly enhanced their cation binding ability. 相似文献
103.
Hirofumi Maekawa 《Tetrahedron letters》2004,45(20):3869-3872
Mg-promoted reduction of a mixture of aromatic ketones (or imines) and aliphatic carbonyl compounds in N,N-dimethylformamide (DMF) brought about unique mixed pinacol type of cross coupling to give unsymmetrical vicinal diols (or amino alcohols) or α-hydroxyketones in good to moderate yields. The reaction may be initiated by electron transfer from magnesium metal to an aromatic carbonyl compound possessing a less negative reduction potential. The difference of reduction potential between aromatic ketones (or imines) and aliphatic carbonyl compounds was found to be one of the important key factors in this selective cross coupling. 相似文献
104.
By the reaction of α-methylaldehydes with trimethylsilylethylidenetriarylphosphoranes the introduction of vinyl group is effected in highly Cram-selective manner. 相似文献
105.
106.
107.
Megumu Munakata Jing Han Atsuhiro Nabei Takayoshi Kuroda-Sowa Masahiko Maekawa Yusaku Suenaga Nozomu Gunjima 《Polyhedron》2006,25(18):3519-3525
Two novel Cu(II) complexes with 1,2-bis(2′-methyl-5′-(2″-pyridyl)-3′-thienyl)perfluorocyclopentene (BM-2-PTP) or its closed-form (closed-BM-2-PTP) were synthesized and characterized by X-ray crystallographic analysis. Both complexes are tetra-coordinated to two N atoms from distinct ligands and two Cl atoms from anions, forming 1-D polymeric structures. [Cu(BM-2-PTP)Cl2] (1) showed typical spectral changes as analogous Ag(I) complexes with the same ligand upon appropriate light stimulus. However, closed-BM-2-PTP displayed different photocyclization from its open-ring form upon irradiation with UV light, indicating the photogenerated closed form turned into two kinds of closed-ring isomers. Furthermore, [Cu(closed-BM-2-PTP)Cl2] (2) was revealed to contain two conformers by X-ray crystallographic analysis and displayed similarities in photocyclization to its free ligand. The distinct absorptions of the UV spectrum were attributed to the coexistence of two conformers in complex 2, both of which showed effective photoreactivities in the crystalline phase. The photochromic mechanism of complex 2 is tentatively concluded as two conformers displaying independent photoreactions. 相似文献
108.
Fujimoto H Pinak M Nemoto T O'Neill P Kume E Saito K Maekawa H 《Journal of computational chemistry》2005,26(8):788-798
Clustered DNA damage sites induced by ionizing radiation have been suggested to have serious consequences to organisms, such as cancer, due to their reduced probability to be repaired by the enzymatic repair machinery of the cell. Although experimental results have revealed that clustered DNA damage sites effectively retard the efficient function of repair enzymes, it remains unclear as to what particular factors influence this retardation. In this study, approaches based on molecular dynamics (MD) simulation have been applied to examine conformational changes and energetic properties of DNA molecules containing clustered damage sites consisting of two lesioned sites, namely 7,8-dihydro-8-oxoguanine (8-oxoG) and apurinic/apyrimidinic (AP) site, located within a few base pairs of each other. After 1 ns of MD simulation, one of the six DNA molecules containing a clustered damage site develops specific characteristic features: sharp bending at the lesioned site and weakening or complete loss of electrostatic interaction energy between 8-oxoG and bases located on the complementary strand. From these results it is suggested that these changes would make it difficult for the repair enzyme to bind to the lesions within the clustered damage site and thereby result in a reduction of its repair capacity. 相似文献
109.
110.
Goto M Yamamoto Y Sumimoto M Tsuruda N Kurosaki H 《Chemical & pharmaceutical bulletin》2003,51(10):1157-1162
Square-planar complexes with the formula [Pt(L(2))(L(1))](X)(2) x nH(2)O, where L(1) is S-2-aminomethylpyrrolidine (S-pyrda) or 2-aminomethylpiperidine (pipda) and L(2) is diammine (X=Cl), cyclobutane-1,1-dicarboxylato (cbdca) (X=none), 2,2'-bipyridine (bpy) (X=NO(3)), or 1,10-phenanthroline (phen) (X=Cl), were prepared and the nature of the coordination of L(1) was examined by (1)H-NMR spectroscopy and X-ray crystallography. These 2-aminomethylazacycloalkane derivatives form five-membered chelate rings condensed with an azacycloalkane ring in cis- or trans-configurations. The (1)H-NMR spectrum of complexes with S-pyrda as L(1) were consistent with cis-condensed rings in an S(N) conformation with any of L(2) group. However, (1)H-NMR spectra of the complexes with pipda as L(1) indicated trans-fused successive rings for the diammine and cbdca as L(2), but spectra for bpy and phen as L(2) were consistent with a conformation having cis-fused successive rings. X-Ray crystallography data for the two complexes with pipda as L(1) and cbdca (1) and bpy (2) as L(2) confirms the different coordination behavior in the solid state. 相似文献