全文获取类型
收费全文 | 2236篇 |
免费 | 214篇 |
国内免费 | 5篇 |
专业分类
化学 | 1981篇 |
晶体学 | 20篇 |
力学 | 38篇 |
数学 | 141篇 |
物理学 | 275篇 |
出版年
2023年 | 16篇 |
2022年 | 12篇 |
2021年 | 40篇 |
2020年 | 46篇 |
2019年 | 60篇 |
2018年 | 37篇 |
2017年 | 31篇 |
2016年 | 95篇 |
2015年 | 107篇 |
2014年 | 110篇 |
2013年 | 183篇 |
2012年 | 146篇 |
2011年 | 181篇 |
2010年 | 143篇 |
2009年 | 111篇 |
2008年 | 137篇 |
2007年 | 123篇 |
2006年 | 111篇 |
2005年 | 89篇 |
2004年 | 78篇 |
2003年 | 85篇 |
2002年 | 78篇 |
2001年 | 47篇 |
2000年 | 40篇 |
1999年 | 16篇 |
1998年 | 13篇 |
1997年 | 9篇 |
1996年 | 18篇 |
1995年 | 17篇 |
1994年 | 12篇 |
1993年 | 11篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1987年 | 7篇 |
1985年 | 10篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 14篇 |
1981年 | 14篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 14篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1975年 | 10篇 |
1974年 | 8篇 |
1958年 | 7篇 |
1957年 | 6篇 |
排序方式: 共有2455条查询结果,搜索用时 125 毫秒
151.
Frontispiece: NMR Fingerprints of the Drug‐like Natural‐Product Space Identify Iotrochotazine A: A Chemical Probe to Study Parkinson’s Disease 下载免费PDF全文
152.
Kinetic Modeling of α‐Hydrogen Abstractions from Unsaturated and Saturated Oxygenate Compounds by Carbon‐Centered Radicals 下载免费PDF全文
Paschalis D. Paraskevas Dr. Maarten K. Sabbe Prof. Marie‐Françoise Reyniers Prof. Dr. Nikos Papayannakos Prof. Dr. Guy B. Marin 《Chemphyschem》2014,15(9):1849-1866
Hydrogen abstractions are important elementary reactions in a variety of reacting media at high temperatures in which oxygenates and hydrocarbon radicals are present. Accurate kinetic data are obtained from CBS‐QB3 ab initio (AI) calculations by using conventional transition‐state theory within the high‐pressure limit, including corrections for hindered rotation and tunneling. From the obtained results, a group‐additive (GA) model is developed that allows the Arrhenius parameters and rate coefficients for abstraction of the α‐hydrogen from a wide range of oxygenate compounds to be predicted at temperatures ranging from 300 to 1500 K. From a training set of 60 hydrogen abstractions from oxygenates by carbon‐centered radicals, 15 GA values (ΔGAVos) are obtained for both the forward and reverse reactions. Among them, four ΔGAVos refer to primary contributions, and the remaining 11 ΔGAVos refer to secondary ones. The accuracy of the model is further improved by introducing seven corrections for cross‐resonance stabilization of the transition state from an additional set of 43 reactions. The determined ΔGAVos are validated upon a test set of AI data for 17 reactions. The mean absolute deviation of the pre‐exponential factors (log A) and activation energies (Ea) for the forward reaction at 300 K are 0.238 log(m3 mol?1 s?1) and 1.5 kJ mol?1, respectively, whereas the mean factor of deviation <ρ> between the GA‐predicted and the AI‐calculated rate coefficients is 1.6. In comparison with a compilation of 33 experimental rate coefficients, the <ρ> between the GA‐predicted values and these experimental values is only 2.2. Hence, the constructed GA model can be reliably used in the prediction of the kinetics of α‐hydrogen‐abstraction reactions between a broad range of oxygenates and oxygenate radicals. 相似文献
153.
Fumaric acid was reacted with the binary superacidic systems HF/SbF5 and HF/AsF5. The O,O'-diprotonated [C4H6O4]2+([MF6]–)2 (M = As, Sb) and the O-monoprotonated [C4H5O4]+[MF6]– (M = As, Sb) species are formed depending on the stoichiometric ratio of the Lewis acid to fumaric acid. The colorless salts were characterized by low-temperature vibrational spectroscopy. In case of the hexafluoridoantimonates single-crystal X-ray structure analyses were carried out. The [C4H6O4]2+([SbF6]–)2 crystallizes in the monoclinic space group C2/c with four formula units per unit cell and [C4H5O4]+[SbF6]– crystallizes in the triclinic space group P1 with one formula unit per unit cell. The protonation of fumaric acid does not cause a notable change of the C=C bond length. The experimental data are discussed together with quantum chemical calculations of the cations [C4H6O4 · 4 HF]2+ and [C4H6O4 · 2 H2CO · 2 HF]2+. 相似文献
154.
Dr. Viktor Pfeifer Marie Certiat Dr. Donia Bouzouita Dr. Alberto Palazzolo Sébastien Garcia-Argote Elodie Marcon David-Alexandre Buisson Dr. Philippe Lesot Prof. Laurent Maron Dr. Bruno Chaudret Dr. Simon Tricard Dr. Iker del Rosal Prof. Romuald Poteau Dr. Sophie Feuillastre Dr. Grégory Pieters 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(22):4988-4996
Ruthenium nanocatalysis can provide effective deuteration and tritiation of oxazole, imidazole, triazole and carbazole substructures in complex molecules using D2 or T2 gas as isotopic sources. Depending on the substructure considered, this approach does not only represent a significant step forward in practice, with notably higher isotope uptakes, a broader substrate scope and a higher solvent applicability compared to existing procedures, but also the unique way to label important heterocycles using hydrogen isotope exchange. In terms of applications, the high incorporation of deuterium atoms, allows the synthesis of internal standards for LC-MS quantification. Moreover, the efficacy of the catalyst permits, even under subatmospheric pressure of T2 gas, the preparation of complex radiolabeled drugs owning high molar activities. From a fundamental point of view, a detailed DFT-based mechanistic study identifying undisclosed key intermediates, allowed a deeper understanding of C−H (and N−H) activation processes occurring at the surface of metallic nanoclusters. 相似文献
155.
Maa Mavri Katja Spiess Mette Marie Rosenkilde Catrin Sian Rutland Milka Vrecl Valentina Kubale 《Molecules (Basel, Switzerland)》2020,25(23)
Endocytosis is a fundamental process involved in trafficking of various extracellular and transmembrane molecules from the cell surface to its interior. This enables cells to communicate and respond to external environments, maintain cellular homeostasis, and transduce signals. G protein-coupled receptors (GPCRs) constitute a family of receptors with seven transmembrane alpha-helical domains (7TM receptors) expressed at the cell surface, where they regulate physiological and pathological cellular processes. Several herpesviruses encode receptors (vGPCRs) which benefits the virus by avoiding host immune surveillance, supporting viral dissemination, and thereby establishing widespread and lifelong infection, processes where receptor signaling and/or endocytosis seem central. vGPCRs are rising as potential drug targets as exemplified by the cytomegalovirus-encoded receptor US28, where its constitutive internalization has been exploited for selective drug delivery in virus infected cells. Therefore, studying GPCR trafficking is of great importance. This review provides an overview of the current knowledge of endocytic and cell localization properties of vGPCRs and methodological approaches used for studying receptor internalization. Using such novel approaches, we show constitutive internalization of the BILF1 receptor from human and porcine γ-1 herpesviruses and present motifs from the eukaryotic linear motif (ELM) resources with importance for vGPCR endocytosis. 相似文献
156.
Jean‐Franois Ayme Sbastien Dhers Jean‐Marie Lehn 《Angewandte Chemie (International ed. in English)》2020,59(30):12484-12492
Three imine‐based metal complexes, having no overlap in terms of their compositions, have been simultaneously generated from the self‐sorting of a constitutional dynamic library (CDL) containing three amines, three aldehydes, and three metal salts. The hierarchical ordering of the stability of the three metal complexes assembled and the leveraging of the antagonistic and agonistic relationships existing between the constituents within the constitutional dynamic network corresponding to the CDL were pivotal in achieving the sorting. Examination of the process by NMR spectroscopy showed that the self‐sorting of the FeII and ZnII complexes depended on an interplay between the thermodynamic driving forces and a kinetic trap involved in their assembly. These results also exemplify the concept of “simplexity”—the fact that the output of a self‐assembling system may be simplified by increasing its initial compositional complexity—as the two complexes could self‐sort only in the presence of the third pair of organic components, those of the CuI complex. 相似文献
157.
Victor de Seauve Marie‐Anglique Languille Mathieu Kociak Stphanie Belin James Ablett Christine Andraud Odile Stphan Jean‐Pascal Rueff Emiliano Fonda Bertrand Lavdrine 《Angewandte Chemie (International ed. in English)》2020,59(23):9113-9119
The first colour photographs were created by a process introduced by Edmond Becquerel in 1848. The nature of these photochromatic images colours motivated a debate between scientists during the XIXth century, which is still not settled. We present the results of chemical analysis (EDX, HAXPES and EXAFS) and morphology studies (SEM, STEM) aiming at explaining the optical properties of the photochromatic images (UV‐visible spectroscopy and low loss EELS). We rule out the two hypotheses (pigment and interferences) that have prevailed since 1848, respectively based on variations in the oxidation degree of the compound forming the sensitized layer and periodically spaced photolytic silver planes. A study of the silver nanoparticles dispersions contained in the coloured layers showed specific localizations and sizes distributions of the nanoparticles for each colour. These results allow us to formulate a plasmonic hypothesis on the origin of the photochromatic images colours. 相似文献
158.
Dborah De Masi Juan M. Asensio Pier‐Francesco Fazzini Lise‐Marie Lacroix Bruno Chaudret 《Angewandte Chemie (International ed. in English)》2020,59(15):6187-6191
Induction heating of magnetic nanoparticles (NPs) is a method to activate heterogeneous catalytic reactions. It requires nano‐objects displaying high heating power and excellent catalytic activity. Here, using a surface engineering approach, bimetallic NPs are used for magnetically induced CO2 methanation, acting both as heating agent and catalyst. The organometallic synthesis of Fe30Ni70 NPs displaying high heating powers at low magnetic field amplitudes is described. The NPs are active but only slightly selective for CH4 after deposition on SiRAlOx owing to an iron‐rich shell (25 mL min?1, 25 mT, 300 kHz, conversion 71 %, methane selectivity 65 %). Proper surface engineering consisting of depositing a thin Ni layer leads to Fe30Ni70@Ni NPs displaying a very high activity for CO2 hydrogenation and a full selectivity. A quantitative yield in methane is obtained at low magnetic field and mild conditions (25 mL min?1, 19 mT, 300 kHz, conversion 100 %, methane selectivity 100 %). 相似文献
159.
Rene F. Roller Ankita Malik Maria A. Carillo Monika Garg Antonella Rella Marie‐Kristin Raulf Bernd Lepenies Peter H. Seeberger Daniel Varn Silva 《Angewandte Chemie (International ed. in English)》2020,59(29):12035-12040
Glypiation is a common posttranslational modification of eukaryotic proteins involving the attachment of a glycosylphosphatidylinositol (GPI) glycolipid. GPIs contain a conserved phosphoglycan that is modified in a cell‐ and tissue‐specific manner. GPI complexity suggests roles in biological processes and effects on the attached protein, but the difficulties to get homogeneous material have hindered studies. We disclose a one‐pot intein‐mediated ligation (OPL) to obtain GPI‐anchored proteins. The strategy enables the glypiation of folded and denatured proteins with a natural linkage to the glycolipid. Using the strategy, glypiated eGFP, Thy1, and the Plasmodium berghei protein MSP119 were prepared. Glypiation did not alter the structure of eGFP and MSP119 proteins in solution, but it induced a strong pro‐inflammatory response in vitro. The strategy provides access to glypiated proteins to elucidate the activity of this modification and for use as vaccine candidates against parasitic infections. 相似文献
160.
Liu Song Yang Huang Marie‐Jia Gou Jacques Crommen Zhengjin Jiang Yifan Feng 《Journal of separation science》2020,43(13):2728-2736
Biogenic amines have been reported in many foods such as fish, meat, and soy sauce. The consumption of foods containing high concentrations of biogenic amines has been associated with health hazards. In this study, a green and efficient method using supercritical fluid chromatography coupled with single quadrupole mass spectrometry was developed for determination of biogenic amines in soy sauce. The chromatographic and mass spectrometry conditions were systematically optimized in terms of selectivity and peak shape. Nine biogenic amines were well separated within 25 min on a Cosmosil 5HP column using 5% (v/v) water and 0.2% (v/v) ammonia solution in methanol as mobile phase additives at a backpressure of 120 bar and temperature of 40°C. The established method was fully validated regarding the linearity, sensitivity, precision, and accuracy. The limits of detection and limits of quantification ranged from 0.03 to 10.50 μg/mL and 0.10 to 23.1 μg/mL, respectively. The relative standard deviations for intra‐ and interday precisions were all lower than 9.36% and the recoveries ranged from 75.82 to 99.63% and 80.10 to 99.89% for two levels of standards spiked in soy sauce, respectively. Finally, the established method was successfully applied to the quantitative analysis of biogenic amines in soy sauce. 相似文献