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981.
Dr. Cheng‐Hsiu Chang Larry S. Lico Dr. Teng‐Yi Huang Dr. Shu‐Yi Lin Dr. Chi‐Liang Chang Prof. Dr. Susan D. Arco Prof. Dr. Shang‐Cheng Hung 《Angewandte Chemie (International ed. in English)》2014,53(37):9876-9879
Fondaparinux, a synthetic pentasaccharide based on the heparin antithrombin‐binding domain, is an approved clinical anticoagulant. Although it is a better and safer alternative to pharmaceutical heparins in many cases, its high cost, which results from the difficult and tedious synthesis, is a deterrent for its widespread use. The chemical synthesis of fondaparinux was achieved in an efficient and concise manner from commercially available D ‐glucosamine, diacetone α‐D ‐glucose, and penta‐O‐acetyl‐D ‐glucose. The method involves suitably functionalized building blocks that are readily accessible and employs shared intermediates and a series of one‐pot reactions that considerably reduce the synthetic effort and improve the yield. 相似文献
982.
Set-Valued and Variational Analysis - In this paper, we study bornological generalized differential properties of sets with nonsmooth boundaries, nonsmooth functions, and set-valued mappings in... 相似文献
983.
Emily C. Heider Khang Trieu Victor M. Diaz Karin Y. Chumbimuni-Torres Andres D. Campiglia Steven J. Duranceau 《Mikrochimica acta》2013,180(11-12):1013-1020
The modification of electrodes with gold nanoparticles results in an increased electrode surface area, enhanced mass transport, and improved catalytic properties. We have extended this approach to indium tin oxide (ITO) electrodes to obtain optically transparent gold nanorod-modified electrodes which display enhanced electrochemical capabilities and have the additional advantage of showing a tunable surface plasmon resonance. The procedures for attaining high surface coverage (15 gold nanorods per square µm) of such electrodes were optimized, and the potential-dependent surface plasmon resonance was studied under controlled electrical potential. In an exemplary sensor application, we demonstrate the detection of mercury via potential-dependent formation of an Au-Hg amalgam.
Immobilization of gold nanorods on optically transparent ITO electrodes provides tunable surface plasmon resonance detection coupled with electrochemical potential control. These novel sensors are applied to the detection and quantification of mercury with a combined SPR-electrochemical technique 相似文献
984.
Rodrigo Lopes F. de Oliveira Jorge H. Pedrobom Amauri A. Menegário Roberto N. Domingos Delcy A. Py Júnior Chang Hung Kiang 《Analytica chimica acta》2013
Acid mine drainage (AMD) is a serious environmental problem that creates acidic solution with high Mn concentrations. The speciation of residual Mn from AMD after an active treatment involving the addition of a neutralizing agent can reliably evaluate the treatment efficiency and provide knowledge of the Mn species being inputted into the environment. The aim of this study was to evaluate the in situ lability and speciation of Mn using the diffusive gradients in thin films (DGT) technique with treated drainage water from a uranium mine (TAMD). DGT devices with different binding phases (Chelex-100 and P81 and DE81membranes) were used to perform the in situ speciation of Mn. 相似文献
985.
Hsiu‐Li Su Yi‐Ping Lee Huan‐Yi Hung Cheng‐Yu Lee Wen‐Sheng Chung You‐Zung Hsieh 《中国化学会会志》2013,60(1):113-119
In nonaqueous capillary electrophoresis (NACE), an organic solvent is used in place of an aqueous medium as the background solution to improve the solubility and selectivity for hydrophobic analytes. In this study, we employed NACE with UV detection for the analysis of eight calix[4]arenes. We examined the influence of several parameters—the buffer composition, the nonaqueous solvent‘s composition and proportion, and the concentration of the electrolyte of the nonaqueous buffer—on the efficiency of the electrophoretic separation. The separation was achieved through the analyte's different effective mobility via different degrees of deprotonation on the phenolic OH groups of the calix[4]arene. This deprotonation can further affect the analyte's ability to form a complex with the metal ion. The optimized background electrolyte (BGE), comprising a mixture of N‐methylformamide/acetonitrile (30:70, v/v) and 100 mM AcOH/20 mM NH4OAc, provided rapid (<11 min) separation of the calix[4]arenes with good resolution. The relative standard deviations of the migration times for the eight analytes were all less than 1%. Within the calibration concentration range, the coefficients of determination (R2) were all greater than 0.9914. Thus, the present study demonstrated NACE can provide adequate separation for the analysis of calix[4]arenes. 相似文献
986.
The direct synthesis of secondary amines from the corresponding primary amines by alkylation has been widely used. The major drawback, however, consists of polyalkylation. Several procedures exist for the solution of the problem. Some of the early methods involve reduction3, or alkylative hydrolysis4 of Schiff base. Other methods include acid hydrolysis of alkylated formanilides prepared from primary aromatic amine and trialkyl orthoformate5, or acid hydrolysis of N-alkylated phosphinamides6, or zinc cleavage of N-alkylated phenacylsulfonamides7, or reductive deprotection of N-alkylated trifluoromethanesulfonamides7. This latter method is analogous to the Gabriel synthesis of 相似文献
987.
Jean-Paul Silvestre Nguyen Quy Dao et Pascale Salvini 《Phosphorus, sulfur, and silicon and the related elements》2013,188(4):771-779
The organic complex salt [H 3 N--CH 2 --CH 2 --NH 3 ][C(CH 3 )(OH)(PO 3 H 2 )(PO 3 H)] 2 is obtained by reaction between the hydroxyethylidenebisphosphonic acid (HEBP) and the ethylenediamine (EDA) in aqueous medium. This compound, the first where the cation is an organic base, crystallizes with the monoclinic space group P2 1 / c (n°;14) and a = 6.867(1) Å, b = 11.665(2) Å, c = 10.977(2) Å, g = 101.85(4)°;, V = 861.2(2) Å 3 , Z = 2. The cohesion of the crystal structure is assumed exclusively by a dense network of hydrogen bonds between two HEDP m and between one HEDP m and one EDA 2+ . 相似文献
988.
Dr. Günter Klatt Dr. Rong Xu Dr. Markus Pernpointner Lise Molinari Tran Quang Hung Prof. Dr. A. Stephen K. Hashmi Prof. Dr. Horst Köppel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(12):3954-3961
The β‐H‐elimination in the (IPr)AuEt complex and its microscopic reverse, the insertion of ethene into (IPr)AuH, were investigated in a combined experimental and computational study. Our DFT‐D3 calculations predict free‐energy barriers of 49.7 and 36.4 kcal mol?1 for the elimination and insertion process, respectively, which permit an estimation of the rate constants for these reactions according to classical transition‐state theory. The elimination/insertion pathway is found to involve a high‐energy ethene hydride species and is not significantly affected by continuum solvent effects. The high barriers found in the theoretical study were then confirmed experimentally by measuring decomposition temperatures for several different (IPr)AuI‐alkyl complexes which, with a slow decomposition at 180 °C, are significantly higher than those of other transition‐metal alkyl complexes. In addition, at the same temperature, the decomposition of (IPr)AuPh and (IPr)AuMe, both of which cannot undergo β‐H‐elimination, indicates that the pathway for the observed decomposition at 180 °C is not a β‐H‐elimination. According to the calculations, the latter should not occur at temperatures below 200 °C. The microscopic reverse of the β‐H‐elimination, the insertion of ethene into the (IPr)AuH could neither be observed at pressures up to 8 bar at RT nor at 1 bar at 80 °C. The same is true for the strain‐activated norbornene. 相似文献
989.
Ning Huang Ka Hung Lee Yan Yue Xiaoyi Xu Stefan Irle Qiuhong Jiang Donglin Jiang 《Angewandte Chemie (International ed. in English)》2020,59(38):16587-16593
Transformation of carbon dioxide to high value‐added chemicals becomes a significant challenge for clean energy studies. Here a stable and conductive covalent organic framework was developed for electrocatalytic carbon dioxide reduction to carbon monoxide in aqueous solution. The cobalt(II) phthalocyanine catalysts are topologically connected via robust phenazine linkage into a two‐dimensional tetragonal framework that is stable under boiling water, acid, or base conditions. The 2D lattice enables full π conjugation along x and y directions as well as π conduction along the z axis across the π columns. With these structural features, the electrocatalytic framework exhibits a faradaic efficiency of 96 %, an exceptional turnover number up to 320 000, and a long‐term turnover frequency of 11 412 hour?1, which is a 32‐fold improvement over molecular catalyst. The combination of catalytic activity, selectivity, efficiency, and durability is desirable for clean energy production. 相似文献