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951.
Selective introducing of aryl and amino groups: reaction of benzanthrone and organometallic reagents
Rui Umeda Teruaki Namba Tomohiro Yoshimura Masamichi Nakatsukasa Yutaka Nishiyama 《Tetrahedron》2013,69(5):1526-1531
The reaction of benzanthrone and aryl magnesium bromides produced 6-aryl-substituted benzanthrones in moderate to good yields. Similarly, 6-alkylaminobenzanthrones were selectively prepared by the reaction of benzanthrone and lithium alkylamides. In contrast, for the lithium arylamides, the arylamino groups were selectively introduced at the 4-position of the benzanthrone. 相似文献
952.
Masahiko Suzuki Yukio Yamamoto Masahiro Irie Koichiro Hayashi 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(8):1607-1622
Photopolymerization of styrene in the presence of pyromellitic dianhydride, an electron acceptor which forms a charge-transfer complex with the monomer, was studied. Polymerization was initiated by illumination with a light of wavelength longer than 350 nm, where only the charge-transfer absorption band exists. It was found that the reaction involves cationic and radical polymerizations and that the reaction course strongly depends on polarity of the system. It was also suggested by the dependence of the rate of polymerization on light intensity and temperature that the cationic polymerization consists of free ion and ion-pair polymerizations. These results were compared with those of the photoinduced cationic polymerization of α-methylstyrene, which has previously been studied. 相似文献
953.
Radiation-induced polymerization of acrylonitrile-urea canal complexes formed in frozen ethylene glycol or tert-butyl alcohol media was investigated. Formation of canal complexes in the frozen state was prolonged. The initial rate of polymerization was enhanced in the frozen state. The degree of polymerization of polymers obtained is found to show no depression at high conversions and is higher in the frozen state, suggesting stabilization of canal complexes by the frozen medium. 相似文献
954.
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957.
Masafumi Takesue Hiromichi Hayashi Richard L. Smith 《Progress in Crystal Growth and Characterization of Materials》2009,55(3-4):98-124
Thermal and chemical methods for producing zinc silicate, Zn2SiO4 phosphor on industrial and laboratory scales are reviewed. Zinc silicate has a promising future in advanced materials as a highly versatile luminescent material due to the wide range of multi-colors that can be obtained from various guest ions. Candidates for future industrial methods of producing zinc silicate are critically reviewed from the point of view of phase formation and compared with the conventional solid-state reaction. Conventional methods require calcination at temperatures higher than 1000 °C and long reaction times to form Zn2SiO4 phase and these processes limit particle shape and size. Sol–gel methods are performed in a solvent at ambient pressure, while hydrothermal and solvothermal methods tend use high temperatures and high pressures, and especially supercritical water methods tend use conditions higher than 400 °C and 25 MPa. Hydrothermal and sol–gel literature shows that crystallization of Zn2SiO4 requires at least temperatures of around 100 °C. Of all the growth methods, supercritical water is able to bring about phase formation in the shortest reaction time. Vapor methods are performed with a gas phase as the reaction medium. Vapor and sol–gel methods require post-calcination for crystallization and have the advantage of providing characteristic particles such as uniform shapes, spherical particles, or nano-sized particles by varying the experimental conditions; they may be combined with the other crystallization routes in the future. 相似文献
958.
Makoto Hayashi 《Mathematica Slovaca》2009,59(4):505-515
In this paper, the non-existence of limit cycles of a Liénard system ẋ = y−F(x), ẏ = −g(x) is discussed. By using the transformation y = z+ϕ(x) to the system, the new system has two special isoclines. We call the curves Vertical isocline or Horizontal isocline, respectively.
It shall be shown that the existence of these isoclines play an important role in the non-existence of limit cycles of the
system. The results are applied to many examples, and the known results are improved in certain cases.
The results were announced at Annual Meeting of Mathematical Society of Japan on September 19 of 2005. Also they were published
at the Poster Competition of ICM(Madrid) on August 22–30 of 2006. 相似文献
959.
We present a general scheme for finding or creating a metastable vacuum in supersymmetric theories. By using the formalism, we show that there is a parameter region where a metastable vacuum exists in the Wess–Zumino model coupled to messenger fields. This model serves as a perturbative renormalizable model of direct gauge mediation. 相似文献
960.
Hitoshi Shirase Yurie Miura Yutaka Fukuda 《Monatshefte für Chemie / Chemical Monthly》2009,36(8):807-814