全文获取类型
收费全文 | 3920篇 |
免费 | 177篇 |
国内免费 | 15篇 |
专业分类
化学 | 2607篇 |
晶体学 | 41篇 |
力学 | 63篇 |
综合类 | 1篇 |
数学 | 440篇 |
物理学 | 960篇 |
出版年
2023年 | 42篇 |
2022年 | 127篇 |
2021年 | 113篇 |
2020年 | 101篇 |
2019年 | 116篇 |
2018年 | 89篇 |
2017年 | 97篇 |
2016年 | 161篇 |
2015年 | 119篇 |
2014年 | 125篇 |
2013年 | 229篇 |
2012年 | 254篇 |
2011年 | 315篇 |
2010年 | 193篇 |
2009年 | 201篇 |
2008年 | 278篇 |
2007年 | 249篇 |
2006年 | 205篇 |
2005年 | 180篇 |
2004年 | 169篇 |
2003年 | 115篇 |
2002年 | 89篇 |
2001年 | 63篇 |
2000年 | 72篇 |
1999年 | 47篇 |
1998年 | 28篇 |
1997年 | 29篇 |
1996年 | 32篇 |
1995年 | 30篇 |
1994年 | 23篇 |
1993年 | 29篇 |
1992年 | 32篇 |
1991年 | 13篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 13篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1972年 | 4篇 |
1968年 | 3篇 |
排序方式: 共有4112条查询结果,搜索用时 16 毫秒
971.
972.
Dr. Fábio M. F. Santos Zoe Domínguez João P. L. Fernandes Dr. Cátia Parente Carvalho Dr. Daniel Collado Prof. Dr. Ezequiel Pérez-Inestrosa Maria V. Pinto Dr. Adelaide Fernandes Dr. Jesús F. Arteaga Dr. Uwe Pischel Dr. Pedro M. P. Gois 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(62):14064-14069
Boronic acid-derived salicylidenehydrazone complex (BASHY) dyes with a polymethine backbone were designed to yield efficient red-emitting and two-photon absorbing fluorophores that can be used as markers for astrocytes. The dyes are chemically stable in aqueous solution and do not undergo photodecomposition. Their photophysical properties can be electronically fine-tuned and thereby adapted to potentially different imaging situations and requirements. 相似文献
973.
Jos Luis Malvar Juan Luis Santos Julia Martín Irene Aparicio Esteban Alonso 《Molecules (Basel, Switzerland)》2020,25(22)
The release of pharmaceutically active compounds to the soils through the application of sewage sludge and the irrigation with wastewater, or even with surface water, is constant. The adsorption of these compounds onto the soil is one of the key factors affecting their fate in the environment and their potential environmental risks. In this work, the adsorption of carbamazepine (CBZ) and its metabolites, 3-hydroxy-carbamazepine (3OH-CBZ), carbamazepine-10,11-dihydro-10,11-epoxide (EP-CBZ), and 10,11-dihydro-10-hydroxycarbamazepine (10OH-CBZ), in three Mediterranean soils was evaluated using single-solute and four-solute experiments. The highest adsorptions were measured for 3OH-CBZ, followed by CBZ, EP-CBZ, and 10OH-CBZ, in that order. A high influence of the physicochemical characteristics of the compounds, pH, and soil characteristics in the adsorption of the studied compounds was observed and corroborated by the statistical analysis of the results. Moreover, a good fit was observed in the three isotherm models evaluated (linear, Freundlich, and Langmuir) in single-solute experiments (R2 > 0.90). However, a decrease of the measured adsorptions and a worse fit to the isotherm models were observed in the case of multiple-solute experiments. This could be mainly due to the competition established between the studied compounds for the active sites of the soils. 相似文献
974.
975.
Lemos Paulo Vitor França Barbosa Leandro Santos Ramos Ingrid Graça Coelho Rodrigo Estevam Druzian Janice Izabel 《Journal of Thermal Analysis and Calorimetry》2018,131(3):2555-2567
Journal of Thermal Analysis and Calorimetry - The thermal features of potato, banana, corn and cassava starches were correlated with structural properties. These starches were characterized by SEM,... 相似文献
976.
Marieta L.C. Passos Paula C.A.G. Pinto João L.M. Santos M. Lúcia M.F.S. Saraiva André R.T.S. Araujo 《Analytica chimica acta》2015
Nanoparticles (NPs) exhibit a number of distinctive and entrancing properties that explain their ever increasing application in analytical chemistry, mainly as chemosensors, signaling tags, catalysts, analytical signal enhancers, reactive species generators, analyte recognition and scavenging/separation entities. 相似文献
977.
Correia Lidiane P. Procópio José V. V. Santana Cleildo P. Pinto Márcia F. Moura Elisana A. Santos Ana F. O. Macêdo Rui O. 《Journal of Thermal Analysis and Calorimetry》2015,122(1):207-214
Journal of Thermal Analysis and Calorimetry - The aim of this study was to evaluate the physical quality of Tabebuia caraiba (Mart.) Bur. powder, separately in three batches of different particle... 相似文献
978.
Eurico J. S. Cabrita António G. O. Santos Carlos A. M. Afonso 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1)
Abstract The imide-amide rearrangement of cyclic phosphorirnidates 1 leads to the formation of phosphoramidates 3, either thermally (> 180°C) or by the action of a Lewis acid (BF3 OEt2, 60°C)1. In an attempt to develop a synthetic pathway to β aminoalcohols based on this rearrangement, we have thoroughly studied the influence of the structure of the reactants on the Lewis acid catalysed rearrangement. This study brought some insight into the mechanism of this particular reaction, namely the identification of a new polymeric structure 2. not yet described, which is converted into 3 by thermolysis2. The formation of 2 at rt was followed by 3 P NMR. In the case of R′? Ph, the reactivity observed for R2N was: i-Pr2N > Pyrrolidine > n-Bu2N For R2=i-Pr2, the observed R′ group effect was: Bn > 4-NO2Bn > Ph. No reaction was observed for R′ ? Ts, n-Oct. In the case of the groups R′ ? Bn and R2=i Pr2 the Lewis acid effect was also studied: BF3OEt2, BF3MeOr-Bu, Sc(OTf)3 or CITi(Oi-Pr)3 or Me2SnCl2. 相似文献
979.
Molecular recognition of guanosine and 2-acetylaminofluorene-modified guanosine. A comparative study
M. Amélia Santos Teresa Ferreira M. Alexandra Esteves Michael G. Drew Frederick A. Beland M. Matilde Marques 《Supramolecular chemistry》2013,25(4):243-253
Abstract The ability of an abiotic receptor, 7-acetylamino-2-methyl–1,8-naphthyridine, to bind to guanosine was analysed by a combination of NMR determinations and molecular modeling studies. The results indicate that this receptor simulates the base-pairing properties of cytidine in its Watson-Crick interaction with guanosine. Binding of the same receptor to N-(guanosin-8-yl)-2-acetylaminofluorene, the guanosine adduct containing the carcinogen 2-acetylaminofluorene, was found to occur in a similar manner. The calculated binding energies show that the molecular recognition of the adduct is lower than that of the unmodified guanosine. The theoretical studies suggest that the predominance of an abnormal low energy syn conformation for the adduct is the main structural feature accounting for the observed decrease of the host-guest interaction. 相似文献
980.