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71.
我们对酮肟中间体及肟醚类拟除虫菊酯进行了分析。经核磁共振证明,酮肟中间体在生成肟醚南反应过程中其立体构型木发生变化。目前分离酮肟立体异构物的工作报道较少。我们通过薄层色谱对不同取代的具有活性的几种酮肟异构体的分离进行了探讨。 1 实验部分 相似文献
72.
本文首次利用高温高压方法合成了双稀土氧化物LaEuO3、PrEuO3、NdEuO3和SmEuO3。此外,还合成了CeEuO3.5。X射线衍射分析表明LaEuO3属A型(六方)结构,PrEuO3、NdEuO3和SmEuO3属B型(单斜)结构,CeEuO3.5属F型(萤石)结构。室温下用151Eu的21.6 eV γ射线测量了它们的Mossbauer谱,观察到了151Eu同质异能移位和四极劈裂强烈地依赖于Eu离子配位体体积而呈线性关系。超精细相互作用的这种体积效应,主要原因是由于Eu离子5s壳层的重叠畸变所引起。 相似文献
73.
A Mössbauer study of systems Co x Mn3?x?y Fe y O4 and Ni x Mn3?x?y Fe y O4 for values ofx=0·1, 0·5, 1·0 andy ranging from 0·1 to 2·0 in steps of 0·2 have been made. At room temperature samples fory values ranging in between 0·1 to 0·5 exhibit paramagnetic behaviour while all spectra for values ofy between 0·6 to 0·8 show relaxation effects. Well-defined hyperfine Zeeman spectra are observed for all the samples withy>0·8 and resolved in two sextets corresponding to octahedral and tetrahedral site symmetries and a central doublet probably due to the presence of super-paramagnetic particles in the system. The hyperfine field at57Fe nucleus reduces with decreasing iron cobalt and nickel concentration. These observations have been explained in terms of site preference of cations and exchange interactions. 相似文献
74.
Terminal phosphino groups of [Re2(CO)9(η1-P-P)] (P-P = diphosphines) are activated towards oxidation by Me3NO. The respective reactions of Me3NO with [Re2(CO)9{η1-P(o-anisyl)2(CH2)3PPh2}], [Re2(CO)9{η1-PPh2(CH2)3P(o-anisyl)2}] and [Re2(CO)9(η1-trans-PPh2CHCHPPh2)] were studied to investigate the mechanism of this oxidation. The results are consistent with an intramolecular pathway involving a cyclic intermediate, without exchange of the coordinated and terminal phosphino groups. A mechanism which involves an interaction of the terminal phosphino group with a carbonyl ligand is proposed. In sharp contrast to eq-[Re2(CO)9(η1-P-P)] (P-P = Ph2P(CH2)nPPh2, n = 1-6), eq-[Re2(CO)9(η1-trans-PPh2CHCHPPh2)] appears to be indefinitely stable towards equatorial → axial isomerization at room temperature, thus, allowing its crystal structure to be determined. 相似文献
75.
76.
Abstract A pair of CuII coordination isomers [Cu(pmt)2] · 4H2O (1) and {[Cu(pmt)2] · 2H2O}
n
(2) [Hpmt = 2-(2-pyridylmethylamino) ethanesulfonic acid] have been prepared by reaction of the same proportion CuCl2 · 2H2O and Hpmt but with different experimental methods in water–methanol mixed solution, and were characterized by X-ray diffraction,
elemental analysis, IR spectrum. X-ray analysis indicates that complex (1) is a mononuclear complex in which two deprotonated pmt ligands coordinate in a facial tridentate arrangement about the CuII atom. While complex (2) is a coordination polymer, in which four N atoms of pmt ligands coordinate to one CuII atom but its sulfonate O atoms bond to adjacent CuII atom. Thus 12-membered rings (–Cu–N–C–C–S–O–)2 are obtained between two neighbouring CuII atoms and they connect one another to form this new polymer. Crystal data: [Cu(pmt)2] · 4H2O (1), Mr = 566.10, monoclinic, P2
1/c, a = 9.1950(8) ?, b = 11.5093(10) ?, c = 11.2304(10) ?, β = 105.5550(10)°, Z = 2, V = 1144.96(17) ?3, R
1
= 0.0407, wR
2
= 0.1242 [I > 2σ (I)]; {[Cu(pmt)2] · 2H2O}
n
(2), Mr = 530.07, triclinic, P-1, a = 7.6165(19) ?, b = 8.806(2) ?, c = 9.592(4) ?, α = 104.933(4)°, β = 106.732(4)°, γ = 109.503(3)°, Z = 1, V = 534.2(3) ?3, R
1 = 0.0470, wR
2 = 0.1082 [I > 2σ(I)].
Index Abstract A pair of CuII coordination isomers [Cu(pmt)2] · 4H2O (1) and {[Cu(pmt)2] · 2H2O}
n
(2) [Hpmt = 2-(2-pyridylmethylamino) ethanesulfonic acid] have been prepared by reaction of the same proportion CuCl2 · 2H2O and Hpmt but with different experimental methods in water–methanol mixed solution.
相似文献
77.
Erzsbet Varga Gbor Benkovics Andrs Darcsi Bianka Vrnai Tams Sohajda Milo Malanga Szabolcs Bni 《Electrophoresis》2019,40(21):2789-2798
The chiral separation ability of the full library of methylated‐β‐cyclodextrins towards pharmacologically significant racemic drugs including basic compounds was studied by chiral CE. The syntheses of all the methylated, single isomer β‐cyclodextrins were revised and optimized and the aqueous solubility of the derivatives was unambiguously established. The three most relevant commercially available methylated isomeric mixtures were also included in the screening, so a total of ten various methylated CDs were investigated. The effects of the selector concentration on the enantiorecognition properties at acidic pH were investigated. Among the dimethylated β‐cyclodextrins, the heptakis (2,6‐di‐O‐methyl)‐β‐cyclodextrin isomer (2,6‐DIMEB) resulted to be the most versatile chiral selector. Terbutaline was selected as a model compound for the in‐depth investigation of host‐guest enantiodiscrimination ability. The association constants between the two terbutaline enantiomers and 2,6‐DIMEB were determined in order to support that the enantioseparation is driven by differences is host‐guest binding. The migration order of the enantiomers was confirmed by performing spiking experiments with the pure enantiomers. 1D and 2D NMR spectroscopy was applied to the 2,3‐, and 2,6‐DIMEB/terbutaline systems to rationalize at molecular level the different enantioseparation ability of the dimethylated β‐cyclodextrin selectors. 相似文献
78.
79.
Kyung Min Lee Brandon M. Lynch Paul Luchette Timothy J. White 《Journal of polymer science. Part A, Polymer chemistry》2014,52(6):876-882
The photomechanical response and photochemistry of a conventional, unsubstituted azobenzene‐functionalized liquid crystalline polymer network (azo‐LCN) is contrasted to that of an analogous material prepared with meta‐fluorinated azobenzene chromophores. The polydomain azo‐LCN materials exhibit nearly identical thermomechanical and optical properties. Photomechanical characterization indicates that the fluorination of the azobenzene chromophore reduces the deflection of cantilevers composed of the materials by 50%, which spectroscopic analysis reveals is due to a reduction in the ability of this material to isomerize and potentially reorient. This work is further confirmation that the underlying photochemistry of azobenzene is a primary contributor to the generation of photomechanical work in these materials. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 876–882 相似文献
80.
Hongyu Jiang Hanzhou Jiang Guofei Chen Xingzhong Fang 《Journal of polymer science. Part A, Polymer chemistry》2021,59(13):1434-1445
Two isomers of commercial 4,4′-(4,4′-isopropylidenediphenoxy) bis(phthalic anhydride) (4,4′-BPADA), that is, 3,4′-(4,4′-isopropylidenediphenoxy) bis(phthalic anhydride) (3,4′-BPADA) and 3,3′-(4,4′-isopropylidenediphenoxy) bis(phthalic anhydride) (3,3′-BPADA), were synthesized through aromatic nucleophilic substitution from nitrophthalonitrile and bisphenol A. 3,4′-BPADA was first synthesized from two intermediates, that is, 3-(4-[4-hydroxyphenylisopropylidene] phenoxy) phthalonitrile (3-BPADN) and 3,4′-(4,4′-isopropylidenediphenoxy) bis(phthalonitrile) (3,4′-BPATN). The corresponding three series of polyetherimides (PEIs) were prepared with two representative aromatic diamines (4,4′-oxydianiline and m-phenylenediamine (m-PDA)) via two-step procedure and chemical imidization. Isomeric polyimides showed Tgs from 206 to 256°C in nitrogen and Td5%s from 488 to 511°C in argon, good mechanical properties (tensile moduli of 2.3–3.3 GPa, tensile strengths of 70–96 MPa, and elongations at break of 3.2%–5.1%), and good solubility. With the introduction of 3-substituted phthalimide unit, PEIs displayed higher Tg values, lower strengths and elongations, better solubility and larger d-spacings. The rheological properties of thermoplastic polyimide resins based on the BPADA isomers were investigated, which showed that polyetherimide PEI-3b derived from 3,3′-BPADA and m-PDA had the lowest melt viscosity among the isomers, indicating that the melt processibility had been greatly improved. 相似文献