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91.
Sergey G. Arkhipov Denis A. Rychkov Alexey M. Pugachev Elena V. Boldyreva 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(7):584-592
Crystals of maleates of three amino acids with hydrophobic side chains [L‐leucenium hydrogen maleate, C6H14NO2+·C4H3O4−, (I), L‐isoleucenium hydrogen maleate hemihydrate, C6H14NO2+·C4H3O4−·0.5H2O, (II), and L‐norvalinium hydrogen maleate–L‐norvaline (1/1), C5H11NO2+·C4H3O4−·C5H12NO2, (III)], were obtained. The new structures contain C22(12) chains, or variants thereof, that are a common feature in the crystal structures of amino acid maleates. The L‐leucenium salt is remarkable due to a large number of symmetrically non‐equivalent units (Z′ = 3). The L‐isoleucenium salt is a hydrate despite the fact that L‐isoleucine is a nonpolar hydrophobic amino acid (previously known amino acid maleates formed hydrates only with lysine and histidine, which are polar and hydrophilic). The L‐norvalinium salt provides the first example where the dimeric cation L‐Nva...L‐NvaH+ was observed. All three compounds have layered noncentrosymmetric structures. Preliminary tests have shown the presence of the second harmonic generation (SGH) effect for all three compounds. 相似文献
92.
Effect of intercalating agents on structure and properties of dimer acid‐based polyamide modified by in situ doping of Na‐montmorillonite
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Xiaohui Wang 《先进技术聚合物》2017,28(8):1030-1037
Under the condition of 0.4% (mass), the effects of intercalating agents on conglomeration structure and thermal and mechanical properties of dimer acid‐based polyamide (DAPA) were investigated. The results show that layer‐stripped Na‐montmorillonite (MMT) with octadecyl trimethyl ammonium chloride caused a sharp decrease of content of the γ crystal phase in DAPA, thus bringing out decrease in mechanical properties and increase in IZOD notched impact strength while a sharp increase of content with the γ crystal phase in DAPA modified by Na‐MMT with dioctadecyl dimethyl ammonium chloride. Thus, it brought out a large increase in mechanical properties and a limited increase in IZOD notched impact strength. The decomposition reaction processes of DAPA modified by Na‐MMT and Na‐MMT with octadecyl trimethyl ammonium chloride were one step ranging from 410 to 500°C, respectively. The thermal decomposition reaction processes of DAPA modified by Na‐MMT with dioctadecyl dimethyl ammonium chloride were two steps. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
93.
《Acta Crystallographica. Section C, Structural Chemistry》2017,73(9):754-759
We report the synthesis and characterization of a novel 4‐(dimethylamino)pyridinium‐substituted η3‐cycloheptatrienide–Pd complex which is free of halide ligands. Diacetonitrile{η3‐[4‐(dimethylamino)pyridinium‐1‐yl]cycloheptatrienido}palladium(II) bis(tetrafluoroborate), [Pd(C2H3N)2(C14H16N2)](BF4)2, was prepared by the exchange of two bromide ligands for noncoordinating anions, which results in the empty coordination sites being occupied by acetonitrile ligands. As described previously, exchange of only one bromide leads to a dimeric complex, di‐μ‐bromido‐bis({η3‐[4‐(dimethylamino)pyridinium‐1‐yl]cycloheptatrienido}palladium(II)) bis(tetrafluoroborate) acetonitrile disolvate, [Pd2Br2(C14H16N2)2](BF4)2·2CH3CN, with bridging bromide ligands, and the crystal structure of this compound is also reported here. The structures of the cycloheptatrienide ligands of both complexes are analogous to the dibromide derivative, showing the allyl bond in the β‐position with respect to the pyridinium substituent. This indicates that, unlike a previous interpretation, the main reason for the formation of the β‐isomer cannot be internal hydrogen bonding between the cationic substituents and bromide ligands. 相似文献
94.
《Acta Crystallographica. Section C, Structural Chemistry》2017,73(9):660-666
Nitrogen‐centered urazole radicals exist in equilibrium with tetrazane dimers in solution. The equilibrium established typically favors the free‐radical form. However, 1‐arylurazole radicals bearing substituents at the ortho position favor the dimeric form. We were able to determine the structure of one of the dimers (substituted at both ortho positions with methyl groups), namely 1,2‐(2,4‐dimethylphenyl)‐2‐[2‐(2,4‐dimethylphenyl)‐4‐methyl‐3,5‐dioxo‐1,2,4‐triazolidin‐1‐yl]‐4‐methyl‐1,2,4‐triazolidine‐3,5‐dione, C24H28N6O4, via X‐ray crystallography. The experimentally determined structure agreed well with the computationally obtained geometry at the B3LYP/6‐311G(d,p) level of theory. The preferred syn conformation of these 1‐arylurazole dimers results in the two aromatic rings being proximate and nearly parallel, which leads to some interesting shielding effects of certain signals in the 1H NMR spectrum. Armed with this information, we were able to decipher the more complicated 1H NMR spectrum obtained from a dimer that was monosubstituted at the ortho position with a methyl group. 相似文献
95.
《Acta Crystallographica. Section C, Structural Chemistry》2017,73(12):1131-1136
A monomeric PdII complex bearing a mixed carbocyclic/N‐heterocyclic carbene ligand and two bromides was reacted with an excess of elemental iodine, which resulted in the surprising removal of one bromide ligand and dimerization of the mixed‐carbene complex to form di‐μ‐bromido‐bis{[1‐(cyclohepta‐2,4,6‐trien‐2‐yl‐1‐ylidene‐κC 1)‐3‐(2,6‐diisopropylphenyl)imidazol‐2‐ylidene]palladium(II)} bis(pentaiodide) dichloromethane monosolvate, [Pd2Br2(C22H24N2)2](I5)2·CH2Cl2. The dimeric complex features a slightly distorted square‐planar core of two PdII centres bridged by two bromide ligands, which lie in the same plane as the seven‐ and five‐membered rings of the bidentate carbene ligand. The counter‐ions in the single crystal were found to be pentaiodide monoanions featuring their typical V‐shape, whereas for the bulk material, a mixture of Br/I interhalides is proposed. 相似文献
96.
97.
N. S. Mosyagin A. N. Petrov A. V. Titov 《International journal of quantum chemistry》2011,111(14):3793-3798
The dissociation energy, equilibrium internuclear distance, and spectroscopic constants for the 1Σ ground state of the Yb2 molecule are calculated. The relativistic effects are introduced through generalized relativistic effective core potentials with very high precision. The scalar relativistic coupled cluster method particularly well suited for closed‐shell van der Waals systems is used for the correlation treatment. Extensive generalized correlation basis sets were constructed and used. The relatively small corrections for high‐order cluster amplitudes and spin—orbit interactions are taken into account using smaller basis sets and the spin—orbit density functional theory. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
98.
Noriyuki Yonezawa Toshio Kanoe Kazuhiko Saigo Masaki Hasegawa 《Journal of polymer science. Part A, Polymer chemistry》1993,31(3):667-673
Two new types of polyamides having anti head-to-tail hydroxycinnamic acid dimer component in the main chain were synthesized. Their thermal degradation behavior was investigated by TG-DSC analysis in comparison with those of their model compounds and the polyamides derived from anti head-to-head coumarin dimer. The key reactions in the thermal degradation were clarified to be lactonization and cyclic imide formation. The polyamide, derived from 4-hydroxycinnamic acid dimer and hexamethylenediamine, showed good heat stability. © 1993 John Wiley & Sons, Inc. 相似文献
99.
100.
1,3-二甲基尿嘧啶二聚体的飞行时间质谱裂解规律研究 总被引:1,自引:0,他引:1
采用不同进样方式、不同电子轰击能量和不同反应气压力测定了1,3 二甲基尿嘧啶二聚体(DMUD) 的4个立体异构体A、B、C、D的化学电离(CI)和电子轰击电离(EI)飞行时间质谱.不同方式所测得的CI谱结 果一致,4个异构体出现了强度不同的准分子离子峰(m/z=281),由此推断它们结构之间的相对稳定性次序为: B(trans syn)>D(cis syn)>A(trans anti)>C(cis anti).这一结论被低能量(25eV)电子轰击的EI谱所证实, 并且与合成产物的比例相吻合.EI谱用任何方式测谱均不出现分子离子峰(m/z=280),而出现其单体离子(m/z =140)且为基峰。给出了DMUD的飞行时间质谱裂解途径,同时对CI谱的裂解碎片进行了细致的讨论. 相似文献