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681.
Yue Zhang Natsumi Watanabe Yuuko Miyawaki Yutaka Mune Kenta Fujii Yasuhiro Umebayashi Shin-ichi Ishiguro 《Journal of solution chemistry》2005,34(12):1429-1443
Aprotic N,N-dimethylpropionamide (DMPA) and N,N,N′,N′-tetramethylurea (TMU) are both strong donor solvents and coordinate to metal ions through the carbonyl oxygen atom. These
solvents show a different conformational aspect in the bulk phase, i.e., DMPA exists as either a planar cis or a nonplanar staggered conformer, while TMU exists in a single planar cis conformer. It has been established that the manganese(II) ion is solvated by five molecules in both solvents. Interestingly,
although the planar cis conformer of DMPA is more favorable than the nonplanar staggered one in the bulk phase, the reverse is the case in the coordination
sphere of the metal ion, i.e., a conformational change occurs upon solvation. To reveal the thermodynamic aspect of this conformational change, the complexation
of Mn(II) with bromide ions in DMPA and TMU has been studied by titration calorimetry at 298 K. It was found that the Mn(II)
ion forms mono-, di- and tri-bromo complexes in both solvents, and their formation constants, enthalpies and entropies were
obtained. The Δ H∘1 value for MnBr+ strongly depends on the solvent, i.e., it is positive (19.4 kJ-mol−1) in DMPA and negative (−8.7 kJ-mol−1) in TMU, whereas the Δ H^∘2 and Δ H∘3 values for the stepwise formation of MnBr2 and MnBr3− are both small and negative. The enthalpy of transfer ΔtH∘ from DMPA to TMU, which is evaluated on the basis of the extrathermodynamic TATB assumption, is 25.5 kJ-mol−1 for Mn2+ and −3.6 kJ-mol−1 for MnBr+. These values indicate that the difference between the formation enthalpy of MnBr+ in the two solvents, Δ H^∘1 (DMPA) – Δ H∘1 (TMU), is mainly ascribed to the value of ΔtH∘(Mn2+). It is found that the metal ion is also five-coordinated in the monobromo complex, MnBr(DMPA)4+ . The enthalpy for the conformational change of DMPA from its planar cis to the nonplanar staggered form is evaluated to be −11 and −5.5 kJ-mol−1 for Mn(DMPA)52 + and MnBr(DMPA)4+, respectively. Note that these values are significantly smaller than the corresponding value (5.0 kJ-mol−1) in the bulk phase. We thus conclude that, although steric hindrance among solvent molecules is reduced by replacing one
DMPA of Mn(DMPA)52 + with the relatively small bromide ion, DMPA molecules are still sterically hindered in the MnBr(DMPA)4+ complex. 相似文献
682.
Hagiwara H Hamano K Nozawa M Hoshi T Suzuki T Kido F 《The Journal of organic chemistry》2005,70(6):2250-2255
[reaction: see text] The neo-trans-clerodane natural product, (-)-methyl barbascoate 1, has been synthesized for the first time starting from the known ketone 6 derived from (R)-(-)-Wieland-Miescher ketone analogue 5. 相似文献
683.
Miyuki Hagiwara Hiroshi Mitsui Sueo Machi Tsutomu Kagiya 《Journal of polymer science. Part A, Polymer chemistry》1968,6(3):603-608
The usefulness of liquid carbon dioxide as a solvent for polymerization of ethylene was studied. The effect of liquid carbon dioxide on the polymerization was investigated under conditions of the pressure of 400 kg./cm.2 over the temperature range 20–45°C. by using γ-radiation and AIBN as initiators. The infrared spectrum of the polymers showed that carbon dioxide had little effect on the polymer structure. The polymers contained no combined carbon dioxide and only small amounts of vinylidene unsaturation. The methyl content of the polymers was 0.5–4.0 CH3/1000C. The polymer yield and molecular weight were found to be decreased by the addition of carbon dioxide in both polymerization by γ-radiation and AIBN. The number of polymer molecules formed per unit time increased with the content of carbon dioxide in the γ-ray polymerization, and was constant in the case of AIBN. The advantages of the use of liquid carbon dioxide as a solvent in this polymerization were also considered from the viewpoints of the continuous process, the separation of polymer, the stability of carbon dioxide to radiation, and commercial applications. 相似文献
684.
Watanabe K Suzuki Y Aoki K Sakakura A Suenaga K Kigoshi H 《The Journal of organic chemistry》2004,69(23):7802-7808
The construction of strained carbon skeletons by ring-closing olefin metathesis (RCM) was investigated. With well-designed diene 4, RCM was found to be applicable to the formation of a highly strained inside-outside bicyclo[4.4.1]undecane skeleton of ingenol, a bioactive diterpenoid, and formal total synthesis of optically active ingenol (1) was achieved. The key features of this synthesis are construction of an A-ring by spirocyclization of the ketone with an allylic chloride unit, 26, and ring closure of a B-ring by olefin metathesis. Starting from Funk's keto ester 6, the key intermediate aldehyde 9 in Winkler's total synthesis was synthesized in eight steps in 12.5% overall yield. This strategy of direct cyclization of a strained inside-outside skeleton provided the first easy access to optically active ingenol. 相似文献
685.
An overview of recent structural studies on alkylimidazolium-based salts containing fluoroanions is presented. Alkylimidazolium cations have been most extensively used for syntheses of ionic liquids (room temperature molten salts) because they usually exhibit low melting points, low viscosities and high conductivities. This review mainly focuses on structures of alkylimidazolium-based salts combined with a fluorocomplex anion ((FH)nF−, BF4−, PF6−, AsF6−, SbF6−, NbF6−, TaF6−), N(SO2CF3)2− (TFSI−) and OSO2CF3−. The first part describes crystal structures of these salts and the second part describes computational, spectroscopic and diffraction studies on their liquid structures. Related studies on ionic liquids of non-alkylimidazolium cation and non-fluoroanion are also briefly summarized. 相似文献
686.
Fujio Suganuma Hiroshi Mitsui Sueo Machi Miyki Hagiwara Tsutomu Kagiya 《Journal of polymer science. Part A, Polymer chemistry》1968,6(11):3127-3137
The gamma-radiation-induced polymerization of ethylene in the presence of 13–30 ml of tert-butyl alcohol was carried out under a pressure of 120–400 kg/cm2 at a dose rate of 1 × 103 to 2.5 × 104 rad/hr at 30°C with a 100 ml reactor. The polymerization rate and the molecular weight of the polymer increased with reaction time and pressure and decreased with amount of tert-butyl alcohol. The polymer yield increased almost proportionally with the dose rate, while the molecular weight was almost independent of it. These results were graphically evaluated, and the rate constants of initiation, propagation, and termination for various conditions were determined. No transfer was observed. On the basis of these results the role of tert-butyl alcohol in the polymerization is discussed. 相似文献
687.
Miyuki Hagiwara Takeshi Miura Tsutomu Kagiya 《Journal of polymer science. Part A, Polymer chemistry》1969,7(2):513-523
The γ-ray-induced copolymerization of ethylene and vinyl chloride with the use of liquid carbon dioxide as a solvent was studied under a total pressure of 400 kg/cm2, with a dose rate of 2.5 × 104 rad/hr at 30°C. A rubberlike, sticky polymer is obtained when the molar concentration of vinyl chloride is less than 30% in the monomer mixture, and the polymer is a white powder at higher concentrations of vinyl chloride. Infrared, x-ray, and differential thermal analyses confirm that the polymerization products are noncrystalline, true random copolymers. The rate of copolymerization decreases markedly when a small amount of vinyl chloride is added to ethylene monomer. In the range of vinyl chloride concentration higher than 5%, however, the rate and the molecular weight of copolymer increase with increasing concentration of vinyl chloride. It has been concluded from kinetic considerations based on these results that the rate of initiation increases proportionally with the concentration of vinyl chloride. Further, the growing chain radicals are shown to be deactivated by the cross-termination reaction between the radicals with terminal unit of ethylene and vinyl chloride, and no transfer reaction occurs. 相似文献
688.
689.
690.
Kenta Itahashi Satoshi Itoh Nobuhisa Fukunishi Hans Geissel Ryugo S. Hayano Satoru Hirenzaki Masahiko Iwasaki Paul Kienle Rie Kimura Karl Lindberg Chiara Nociforo Hiroaki Ohnishi Shinji Okada Naoya Ono Haruhiko Outa Masaharu Sato Ken Suzuki Takatoshi Suzuki Hideyuki Tatsuno Per–Erik Tegnér Masanori Wakasugi Helmut Weick Junko Yamagata–Sekihara Toshimitsu Yamazaki Yasushige Yano Irina Zartova 《Hyperfine Interactions》2009,193(1-3):27-31
We are preparing for a high resolution spectroscopy of the 1s and 2s pionic states of 121Sn in the 122Sn(d,3He) reaction at the incident deuteron energy of ~500 MeV. The measurement will provide accurate information on the strong interaction between the pion and the nucleus, which leads to quantitative determination of the magnitude of the quark condensate at the normal nuclear density. 相似文献