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871.
Hisao Yoshida 《Catalysis Surveys from Asia》2005,9(1):1-9
Various photocatalytic reactions have been developed in recent years. Among them, non-oxidative reactions by silica-based quantum photocatalysts are quite unique. Pure silica materials, especially mesoporous silica evacuated at high temperature, were found to promote olefin metathesis upon photoirradiation at room temperature. A kind of surface defect on silica was generated through dehydroxylation at high temperature before the photoreaction, which can be photoexcited to form the first surface intermediate. On the other hand, non-oxidative direct methane coupling was revealed to proceed on silica materials and silica-based quantum photocatalysts. Also in these cases, evacuation at high temperature was required for the activation of catalyst before the reaction. The active sites and feature of silica-based quantum photocatalysts for these non-oxidative reaction systems are summarized and discussed.*To whom correspondence should be addressed.
E-mail: h-yoshida@esi.nagoya-u.ac.jp 相似文献
872.
A summary is presented of the results obtained on metal complexes of carbohydrates (aldoses, ketoses and mono-, di- and polysaccharides) and their derivatives (aldonic and alduronic acids, polyalcohols, amino sugars, and amino acid sugar adducts). The structural parameters (coordination number, bond distance, and Debye–Waller factor) measured by extended X-ray absorption fine structure (EXAFS) spectroscopy obtained earlier on transition metals [Cu(II), Fe(III), Ni(II), Zn(II), Co(II), Ag(I), Mn in different oxidation states and organotin(IV)] complexes are discussed. In addition we report here the preparation of Bu2Sn(IV)2+ complexes of rutin {3-[6-O-(6-deoxy--L-mannopyranosyl)-(-D-glucopyranosyl)oxy]-2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-4H-1-benzopyran-4-one} and quercetin (containing {O,O} donor atoms) in ligand to metal ratios of 1:1 and 1:2. The analytical data revealed the formation of well-defined complexes. The local structures of the complexes were determined by an EXAFS method. It was found that the Sn–O bond distances in the first coordination sphere are closed the values found in Et2Sn(IV) complexes with nonprotected carbohydrates. 相似文献
873.
Kazuyuki Nakai Joji Sonoda Masayuki Yoshida Masako Hakuman Hiromitsu Naono 《Adsorption》2007,13(3-4):351-356
The high resolution adsorption isotherms of N2 (77.4 K) and Ar (87.3 K) have been measured for two nonporous silicas with different silanol contents (3.3 and 0.35 OH/nm2) and for two MFI zeolite with different Al contents (Si/Al=12.5 and 500). Silanol groups and Al sites (acid sites) gives
the significant effect on the N2 isotherms at submonolayer, but the Ar isotherms are independent of silanols and Al sites. The Ar isotherms, therefore, are
preferable in calculation of microporosity of zeolites. The N2 and Ar isotherms for MFI zeolite (Si/Al=500) have been measured at temperatures of 77–94 K, from which the differential adsorption
energies of N2 and Ar are calculated. The interaction of N2 with channel surface of MFI zeolite is greater than that of Ar in the range of α
s
=0.1–0.7. The hystereses are detected for the N2 isotherm in p/p
o=0.1–0.3 at 77.4 K and for the Ar isotherm in p/p
o=3×10−4–2×10−3 at 87.3 K. However, it is difficult to explain the hysteresis phenomenon using differential adsorption energy. 相似文献
874.
Toshiaki Morimoto Nobuhiro Obara Iku Yoshida Kiyoshi Tanaka Toshiyuki Kan 《Tetrahedron letters》2007,48(17):3093-3095
New axially chiral P,O,N-type ligands bearing both a diphenylphosphino group and 2-(dialkylamino)ethyloxy (or 2-pyridylmethyloxy) groups were designed and prepared along with P,O,O-type ligands by employing an easily available chiral component, (R)-2-hydroxy-2′-diphenylphosphinyl-1,1′-binaphthyl. Among the ligands the simplest P,O,N-type one bearing a 2-(dimethylamino)ethyloxy group was found to be the most efficient in copper-catalyzed enantioselective conjugate addition of diethylzinc to a cyclic enone, 2-cyclohexen-1-one, providing high enantioselectivity up to 99% ee. 相似文献
875.
A new symmetric porphyrin, 7,8,17,18-tetraethyl-3,13-dimethylporphyrin-2, 12-dipropionic acid and its derivatives were synthesized by the a,c-biladiene route. Condensation of the dipropionic acid with diamine, [H2N(CH2)nNH2, n= 6,7,8,9,10,12, and14], afforded the corresponding cyclophane porphyrins. The bridged groups were characterized by the 1H-NMR spectra of their zinc complexes. The spin state of the Fe(III) complexes of the cyclophane porphyrins was investigated by changing the size of the bridged chain or size of axial ligand. The cyclophane-porphyrinato (III) perchlorate complexes in a mixture of MeOH and CHCl3, with 4-benzylpyridine provide a model for methemoproteins. Steric constraint between an axial ligand and the bridge group, [-CH2CH2CONH(CH2)nNHCOCH2CH2]at the bridged face determines the ratio of the penta- and hexa-coordinated ferric complexes. The rate of O-binding to the Co(II) cyclophane porphyrins is mar present result indicates that removal of a solvent molecule or sixth axial ligand from the near proximity of the Co(II) complex increases the rate of O- binding. 相似文献
876.
The purpose of our research is to obtain an understanding of the binding mechanism and its correlations in terms of chemical structure and the potentiactive drug activity. The interaction of 5-fluorouracil (5-fluorouracil is used as an anticancer drug) with sodium poly-,L-glutamate in aqueous solution was studied with a spectral method and viscosity measurement. From the binding data, the molar change in enthalpy, entropy and the number of binding sites on the polymer were calculated. It is very interesting that the value ofH0 of the binding of 5-fluorouracil with sodium poly-,L-glutamate is smaller than that of 5-trifluoromethyluracil (although 5-trifluoromethyluracil is not used as an anticancer drug, the compound has a similar structure to 5-fluorouracil). 相似文献
877.
Morita M Koga T Otsuka H Takahara A 《Langmuir : the ACS journal of surfaces and colloids》2005,21(3):911-918
Micropatterned fluoroalkylsilane monolayer surfaces with liquidphilic/liquidphobic area (line width 1-20 microm) were prepared with few defects by vacuum ultraviolet (VUV) photolithography. The anisotropic wetting of a macroscopic droplet with a 0.5-5 mm diameter on the micropatterned surfaces was investigated. The strong anisotropy of the contact angle and the sliding angle and droplet distortion for fluoroalkylsilane/silanol patterned surfaces was attributed to the difference in the energy barrier of wetting between parallel and orthogonal lines. The wetting anisotropy decreased with decreases in the liquidphilic area. Fluoroalkylsilane/alkylsilane patterned surfaces with small differences in the surface free energies of the components showed anisotropic wetting only for the low-surface-tension liquids. 相似文献
878.
Sadahito Aoshima Hideshi Onishi Masamichi Kamiya Kenji Shachi Eiichi Kobayashi 《Journal of polymer science. Part A, Polymer chemistry》1994,32(5):879-887
In the living cationic polymerization of isobutyl vinyl ether (IBVE) by the CH3CH (OiBu) OCOCH3 ( 1 )/EtAlCl2 initiating system in the presence of the added base in hexane at +40°C, the stability of the initiating system 1 /EtAlCl2, which form initiating species CH3CH⊕ (OiBu) derived from 1 , was investigated. In the presence of the Lewis base such as ethyl acetate or 1,4-dioxane, the active species was stable for 300 min even at +40°C in the absence of IBVE, and the living polymers were quantitatively obtained by adding IBVE. However, the active species was partly consumed by side reactions during the standing time for 60 min in the presence of a less basic additive such as ethyl benzoate, and about 50% of the active species was deactivated in the presence of methyl chloroacetate. Consequently, in the case of a less basic additive such as methyl chloroacetate (which was effective for the fast living polymerization), it can be seen that the careful selection of polymerization conditions was required. The living polymerization rate was dependent on the second order of EtAlCl2 concentration. EtAlCl2 induced the cleavage of 1 into CH3CH⊕ (OiBu) and EtAl?Cl2(OCOCH3), and the reactivity of CH3CH⊕ (OiBu) and propagating carbocation may be controlled by EtAl?Cl2(OCOCH3) with the aid of other EtAlCl2. Et1.5AlCl1.5 exists as a bimetallic complex of EtAlCl2 and Et2AlCl, and it is expected that the polymers having a bimodal molecular weight distribution will be obtained due to two kinds of counteranions coming from EtAlCl2 and Et2AlCl. However, in the cationic polymerization of IBVE by 1 /Et1.5AlCl1.5 in the presence of ethyl acetate, the living polymer exhibiting a unimodal and very narrow molecular weight distribution was obtained. Thereby, it was suggested that the counteranions, EtAl?Cl2(OCOCH3) and Et2Al?Cl(OCOCH3), exchange rapidly with each other. © 1994 John Wiley & Sons, Inc. 相似文献
879.
Resorcinarene 1b forms a hexameric assembly in water-saturated CDCl(3) that encapsulates one tetraalkylammonium salt (2(+)Br(-)). The remaining space is occupied by coencapsulated solvent molecules. A maximum of three and minimum of one CHCl(3) molecule were found inside of capsules with tetrapropyl- and tetraheptylammonium bromide, respectively. The encapsulation of the salt is endothermic and entropically favored by the liberation of the solvent molecules. The stabilities of the encapsulation complexes and the rates of guest exchange decrease for larger cations. The higher activation barriers for in/out exchange of the larger guests suggest tight conformational restraints in the transition state. It is likely that complete dissociation of one resorcinarene molecule is necessary for the exchange of the alkylammonium salts. 相似文献
880.
Y. Tabata H. Kobayashi M. Washio Y. Yoshida N. Hayashi S. Tagawa 《Journal of Radioanalytical and Nuclear Chemistry》1986,101(2):163-169
A new picosecond pulse radiolysis Twin LINAC System has been constructed recently at Nuclear Engineering Research Laboratory at the University of Tokyo. The time resolution of the system is 20 ps and the system has a versatile capability for pulse radiolysis study. The outline of the facility is introduced. Some research carried out using the facility is presented. The examples are radiolysis of CCl4 and n-C21H44. 相似文献