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61.
Marie‐Claire Giel Christopher J. Smedley Emily R. R. Mackie Taijie Guo Jiajia Dong Tatiana P. Soares da Costa John E. Moses 《Angewandte Chemie (International ed. in English)》2020,59(3):1181-1186
The boom in growth of 1,4‐disubstituted triazole products, in particular, since the early 2000’s, can be largely attributed to the birth of click chemistry and the discovery of the CuI‐catalyzed azide–alkyne cycloaddition (CuAAC). Yet the synthesis of relatively simple, albeit important, 1‐substituted‐1,2,3‐triazoles has been surprisingly more challenging. Reported here is a straightforward and scalable click‐inspired protocol for the synthesis of 1‐substituted‐1,2,3‐triazoles from organic azides and the bench stable acetylene surrogate ethenesulfonyl fluoride (ESF). The new transformation tolerates a wide selection of substrates and proceeds smoothly under metal‐free conditions to give the products in excellent yield. Under controlled acidic conditions, the 1‐substituted‐1,2,3‐triazole products undergo a Michael addition reaction with a second equivalent of ESF to give the unprecedented 1‐substituted triazolium sulfonyl fluoride salts. 相似文献
62.
Yueqiang Cao Hao Zhang Shufang Ji Zhijun Sui Zheng Jiang Dingsheng Wang Francisco Zaera Xinggui Zhou Xuezhi Duan Yadong Li 《Angewandte Chemie (International ed. in English)》2020,59(28):11647-11652
Atomic regulation of metal catalysts has emerged as an intriguing yet challenging strategy to boost product selectivity. Here, we report a density functional theory‐guided atomic design strategy for the fabrication of a NiGa intermetallic catalyst with completely isolated Ni sites to optimize acetylene semi‐hydrogenation processes. Such Ni sites show not only preferential acetylene π‐adsorption, but also enhanced ethylene desorption. The characteristics of the Ni sites are confirmed by multiple characterization techniques, including aberration‐corrected high‐resolution scanning transmission electron microscopy and X‐ray absorption spectrometry measurements. The superior performance is also confirmed experimentally against a Ni5Ga3 intermetallic catalyst with partially isolated Ni sites and against a Ni catalyst with multi‐atomic ensemble Ni sites. Accordingly, the NiGa intermetallic catalyst with the completely isolated Ni sites shows significantly enhanced selectivity to ethylene and suppressed coke formation. 相似文献
63.
64.
Dr. Yong-Zhi Li Gang-Ding Wang Hong-Yun Yang Prof. Lei Hou Prof. Yao-Yu Wang Prof. Zhonghua Zhu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(69):16402-16407
To develop efficient adsorbent materials for storage and separation of C2H2, an unprecedented supercage MOF, [Me2NH2]⋅[Zn3(ALP)(TDC)2.5]⋅3.5DMF⋅2 H2O ( 1 ) was constructed through medicinal molecule allopurinol (ALP) and S-containing 2,5-thiophenedicarboxylic acid (H2TDC). 1 contains a novel linear trinuclear cluster that is composed by ALP and carboxylates and forms a final uncommon 5-connected yfy topological framework. The framework possesses three types of interlinked cages decorated by rich functional sites, and reveals not only high adsorption capacity for C2H2 but also excellent selective separation for C2H2/CO2 and C2H2/CH4 at 298 K. Dynamic breakthrough experiments on C2H2/CO2 (1:1) mixture and C2H2/CH4 (1:1) mixture also demonstrated the potential of the material to separate C2H2 from CO2 or CH4 mixtures. Molecular simulations were also studied to identify the different CO2- and C2H2- binding sites in 1 , such as carboxylate groups, S atoms and carbonyl groups. 相似文献
65.
Formation of Acetylene in the Reaction of Methane with Iron Carbide Cluster Anions FeC3− under High‐Temperature Conditions 下载免费PDF全文
Dr. Hai‐Fang Li Li‐Xue Jiang Dr. Yan‐Xia Zhao Dr. Qing‐Yu Liu Ting Zhang Prof. Dr. Sheng‐Gui He 《Angewandte Chemie (International ed. in English)》2018,57(10):2662-2666
The underlying mechanism for non‐oxidative methane aromatization remains controversial owing to the lack of experimental evidence for the formation of the first C?C bond. For the first time, the elementary reaction of methane with atomic clusters (FeC3?) under high‐temperature conditions to produce C?C coupling products has been characterized by mass spectrometry. With the elevation of temperature from 300 K to 610 K, the production of acetylene, the important intermediate proposed in a monofunctional mechanism of methane aromatization, was significantly enhanced, which can be well‐rationalized by quantum chemistry calculations. This study narrows the gap between gas‐phase and condensed‐phase studies on methane conversion and suggests that the monofunctional mechanism probably operates in non‐oxidative methane aromatization. 相似文献
66.
Lilu?Zhang Abdul?Waheed Richard?A.?JonesEmail author Vincent?M.?Lynch 《Journal of chemical crystallography》2005,35(9):673-677
The crystal structure of the bis-amido complex of Ti(IV) (η5-C5H5)2Ti(NH(2,4-(C
CSiMe3)2C6H3))2 is reported. This complex was prepared in 52% yield from the reaction of (η5-C5H5)2TiCl2 with two equivalents of LiNH(2,4-(C
CSiMe3)2C6H3) (prepared in situ in THF at −78∘C). The substituted aniline H2N(2,4-(C
CSiMe3)2C6H3) was prepared in 70% yield from the reaction of 2,4-dibromoaniline with Me3SiC
CH using conventional Pd/Cu coupling methodology. The molecular structure of (η5-C5H5)2Ti(NH(2,4-(C
CSiMe3)2C6H3))2 (monoclinic, space group C2/c, Z = 4, a = 29.7523(5) Å, b = 9.5339(2) Å, c = 15.8864(3) Å, β = 93.022(1)∘ features a titanium (IV) center with a distorted tetrahedral geometry which lies on a crystallographic twofold axis. The amido units are arranged so that steric interactions are minimized. The Ti– N distance is 2.016(2) Å. 相似文献
67.
Harald Brand Peter Mayer Dr. Axel Schulz Prof. Dr. Thomas Soller Alexander Villinger 《化学:亚洲杂志》2008,3(6):1050-1058
In a new synthetic approach phenylcyanamide (Hpca) was synthesized by methylation of phenylthiourea followed by a basic work‐up. All products along the synthetic route have been fully characterized by means of NMR, IR, and X‐ray studies. The first structural report of neutral mixed crystals of phenylcyanamide containing monomeric and trimeric Hpca is presented. Examination of these intriguing mixed crystals revealed the formation of distinct layers of monomeric and trimeric Hpca. These layers are interconnected by weak hydrogen bonds. The trimer represents triphenylisomelamine, which readily isomerizes to the triphenylmelamine in the melt, in accord with computations at the B3LYP level, indicating an exothermic process (ΔH=?49.4 kcal mol?1). Pure trimeric Hpca (triphenylisomelamine) was obtained either by recrystallization of the mixed crystals from boiling water or by trimerization of monomeric Hpca in isopropanol for 12 h under reflux conditions. For comparison tritylcyanamide (Htca) and potassium phenylcyanamide as an [18]crown‐6 complex [K([18]crown‐6)pca] have been synthesized, and the solid‐state structures were determined using X‐ray diffraction techniques. The thermal behavior was studied by thermo‐analytical experiments. In agreement with the experimental results, computations predict an exothermic cyclotrimerization process for Hpca (ΔH=?41.3 kcal mol?1). 相似文献
68.
69.
S. A. Mitchenko T. V. Krasnyakova I. V. Zhikharev 《Theoretical and Experimental Chemistry》2008,44(5):316-319
We report the catalysis of the hydrochlorination of acetylene on the surface of dry K2PdCl4 subjected to prior mechanical activation in an atmosphere of acetylene or propylene. The stereochemistry of the reaction
corresponds to trans addition of the halogen and hydrogen atoms to the C-C triple bond. The hydrogen halide is the source
of the halogen atom in the reaction product. The mechanical activation of K2PdCl4, in contrast to the case of K2PtCl4, is also capable of activating the C-C double bond: propylene is hydrochlorinated under similar conditions to isopropyl chloride.
Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 5, pp. 306–309, September–October, 2008. 相似文献
70.
为了提高Cu/USY催化剂在乙炔氢氯化反应中的催化活性,设计并成功制备了一系列离子液体修饰的分子筛负载的铜基催化剂(Cu@TPPB/USY).当铜和TPPB的百分含量均为15时,在反应温度为160℃,乙炔气体空速为120 h-1,氯化氢与乙炔的摩尔比为1.25:1的条件下,催化剂的乙炔转化率提升了1.17倍,氯乙烯选择性一直保持在98%以上.结合催化剂的傅里叶红外(FT-IR)、 N2物理吸脱附(BET)、热重分析(TG)、 X射线光电子能谱(XPS)、透射电镜(TEM)、 X射线衍射(XRD)、氢气程序升温还原(H2-TPR)和等离子体发射光谱(ICP-OES)的表征,认为TPPB的修饰不仅可以促进催化剂中Cu物种的分散,抑制其还原和流失,还能减少催化剂表面积碳、增强Cu活性物种与载体间的相互作用力,有效地提高Cu/USY催化剂的催化活性. 相似文献