全文获取类型
收费全文 | 3014篇 |
免费 | 108篇 |
国内免费 | 18篇 |
专业分类
化学 | 2050篇 |
晶体学 | 20篇 |
力学 | 55篇 |
数学 | 523篇 |
物理学 | 492篇 |
出版年
2023年 | 24篇 |
2022年 | 64篇 |
2021年 | 83篇 |
2020年 | 78篇 |
2019年 | 61篇 |
2018年 | 53篇 |
2017年 | 59篇 |
2016年 | 113篇 |
2015年 | 106篇 |
2014年 | 106篇 |
2013年 | 238篇 |
2012年 | 232篇 |
2011年 | 258篇 |
2010年 | 139篇 |
2009年 | 126篇 |
2008年 | 171篇 |
2007年 | 200篇 |
2006年 | 177篇 |
2005年 | 131篇 |
2004年 | 113篇 |
2003年 | 90篇 |
2002年 | 92篇 |
2001年 | 36篇 |
2000年 | 32篇 |
1999年 | 40篇 |
1998年 | 23篇 |
1997年 | 16篇 |
1996年 | 25篇 |
1995年 | 25篇 |
1994年 | 15篇 |
1993年 | 19篇 |
1992年 | 21篇 |
1991年 | 19篇 |
1990年 | 10篇 |
1989年 | 18篇 |
1988年 | 5篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 21篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1974年 | 7篇 |
1973年 | 4篇 |
1972年 | 2篇 |
排序方式: 共有3140条查询结果,搜索用时 15 毫秒
81.
82.
Picciochi R Canongia Lopes JN Diogo HP Minas da Piedade ME 《The journal of physical chemistry. A》2008,112(41):10429-10434
The standard molar enthalpy of sublimation of monoclinic cyclopentadienyltricarbonylmanganese, Mn(eta (5)-C 5H 5)(CO) 3, at 298.15 K, was determined as Delta sub H m (o)[Mn(eta (5)-C 5H 5)(CO) 3] = 75.97 +/- 0.37 kJ x mol (-1) from Knudsen effusion and Calvet-drop microcalorimetry measurements, thus considerably improving the very large inaccuracy (>10 kJ x mol (-1)) of the published data. The obtained value was used to assess the extension of the OPLS-based all-atom force field we previously developed for iron metallocenes to manganese organometallic compounds. The modified force field was able to reproduce the volumetric properties (density and unit-cell volume) of crystalline Mn(eta (5)-C 5H 5)(CO) 3 with a deviation of 0.6% and the experimentally determined enthalpy of sublimation with an accuracy of 1 kJ x mol (-1). The interaction (epsilon) and atomic-diameter (sigma) parameters of the Lennard-Jones (12-6) potential function used to calculate dispersion contributions within the framework of the force field were found to be transferable from iron to manganese. 相似文献
83.
Experimental data of excess molar enthalpy of binary mixtures of acetonitrile + diethylamine or S-butylamine mixtures as a function of composition at 288.15, 293.15, 298.15 and 303.15 K at atmospheric pressure have been used to calculate excess partial molar enthalpy and partial molar enthalpy of each component as a function of composition as well as partial molar enthalpy properties at infinite dilution. The Flory and Prigogine–Flory–Patterson (PFP) theories were applied to correlate the data. The results of the calculations as well as the influence of temperature and isomers chain on the partial molar enthalpy properties are discussed. 相似文献
84.
85.
Sayra L. Orozco Erick R. Bandala Camilo A. Arancibia-Bulnes Benito Serrano Raúl Surez-Parra Isaias Hernndez-Prez 《Journal of photochemistry and photobiology. A, Chemistry》2008,198(2-3):144-149
The effect of chloride, sulfate and nitrate anions on the color removal of water containing the azo-dye reactive blue 69 (RB69) in acidic solution, by using photo-assisted Fenton process with Fe(II)/H2O2 and Fe(III)/H2O2 systems was investigated. Experiments were conducted in a batch reactor irradiated during 5 h with a domestic 15 W lamp with emission in the visible spectra. Experimental results showed color disappearance in the first 5 min of reaction in the photo-assisted process for all of the different salts, greatly enhancing the reaction rate with respect to the corresponding systems under dark conditions. The exception of the general trend was the Fe2(SO4)3/H2O2/UV system, where the decolorization process is slower probably because the oxidative species generated by rupture of Fe(III)–peroxo complexes are less reactive. Total organic matter depletion and mineralization of the effluent were also tested during the experimental runs by means of total organic carbon (TOC) showing that, for most of the photo-assisted experiments high mineralization was reached after 3 h of reaction. 相似文献
86.
Ricardo L. Mancera Michalis Chalaris Jannis Samios 《Journal of Molecular Liquids》2004,110(1-3):147-153
We have carried out a molecular dynamics study of dimethyl sulfoxide (DMSO) in water at 298 K at two different densities by simulating two different concentrations: 0.055 and 0.19 mole fraction. We have found an enhancement in the structure of water, an effect that becomes more pronounced as the concentration of DMSO increases. At both concentrations there is a well-defined hydration structure around the oxygen atom of DMSO, which is able to establish strong hydrogen bonds with surrounding water molecules. An increase in the concentration of DMSO depletes the solution of bulk water molecules, reducing the number of hydrogen bonds that water can have in the immediate vicinity of DMSO but increasing the strength of the hydrogen bonds made between the oxygen atom of DMSO and water. There is clear evidence of ‘hydrophobic’ hydration around the methyl groups of DMSO, which is enhanced as the concentration of DMSO increases. 相似文献
87.
Ricardo E. Rivas Ignacio López-GarcíaManuel Hernández-Córdoba 《Spectrochimica Acta Part B: Atomic Spectroscopy》2009
A new procedure for the determination of inorganic arsenic (III,V) and antimony (III,V) in water samples by dispersive liquid–liquid micro extraction separation and electrothermal atomic absorption spectrometry (ETAAS) is presented. At pH 1, As(III) and Sb(III) are complexed with ammonium pyrrolidine dithiocarbamate and extracted into the fine droplets formed when mixing carbon tetrachloride (extraction solvent), methanol (disperser solvent) and the sample solution. After extraction, the phases are separated by centrifugation, and As(III) and Sb(III) are determined in the organic phase. As(V) and Sb(V) remain in the aqueous layer. Total inorganic As and Sb are determined after the reduction of the pentavalent forms with sodium thiosulphate. As(V) and Sb(V) are calculated by difference. The detection limits are 0.01 and 0.05 µg L− 1 for As(III) and Sb(III), respectively, with an enrichment factor of 115. The relative standard deviation is in the 2.9–4.5% range. The procedure has been applied to the speciation of inorganic As and Sb in bottled, tap and sea water samples with satisfactory results. 相似文献
88.
89.
Vergara J Barberá J Serrano JL Ros MB Sebastián N de la Fuente R López DO Fernández G Sánchez L Martín N 《Angewandte Chemie (International ed. in English)》2011,50(52):12523-12528
What a core-ker! By the appropriate combination of promesogenic bent-core structures and the C(60) unit, lamellar polar liquid-crystal phases were induced. The supramolecular organization of the functional fullerene-based assemblies, the temperature range of the soft phase, the stabilization of the mesophase-like order at room temperature, and the molecular switching under an electric field can be tuned, depending on the molecular structure. 相似文献
90.
Oracio Serrano 《Journal of organometallic chemistry》2011,696(10):2217-2219
The nickel (0) compound Ni(COD)(GaAr′)2 (Ar′ = C6H3-2,6-(C6H3-2,6-i-Pr2)2), 1, was synthesized by the reaction of Ni(COD)2 (COD = 1,5-cyclooctadiene) with (GaAr′)2. Compound 1 reacted with ethylene at 25 °C and at 1 atm pressure to give the bimetallic cluster [Ni2(GaAr′)2(η1:η1-μ2-C2H4)], 2, through the incorporation of one molecule of ethylene and displacement of COD. The structure of 2 featured an unusual Ni2Ga2C2 core bicyclic structure in which the C2H4 moiety bridges the Ga···Ga edge of a Ga2Ni2 tetrahedron. The galliums each carry an η1-bonded Ar′ substituent which complexes the nickel atom by an η6-π interaction with one of its flanking Ar’ rings. 相似文献