全文获取类型
收费全文 | 2127篇 |
免费 | 125篇 |
国内免费 | 7篇 |
专业分类
化学 | 1810篇 |
晶体学 | 13篇 |
力学 | 28篇 |
数学 | 228篇 |
物理学 | 180篇 |
出版年
2023年 | 31篇 |
2022年 | 50篇 |
2021年 | 84篇 |
2020年 | 93篇 |
2019年 | 67篇 |
2018年 | 35篇 |
2017年 | 42篇 |
2016年 | 84篇 |
2015年 | 92篇 |
2014年 | 86篇 |
2013年 | 123篇 |
2012年 | 161篇 |
2011年 | 199篇 |
2010年 | 111篇 |
2009年 | 90篇 |
2008年 | 141篇 |
2007年 | 118篇 |
2006年 | 105篇 |
2005年 | 86篇 |
2004年 | 80篇 |
2003年 | 56篇 |
2002年 | 41篇 |
2001年 | 17篇 |
2000年 | 11篇 |
1999年 | 12篇 |
1998年 | 10篇 |
1997年 | 7篇 |
1996年 | 15篇 |
1995年 | 6篇 |
1994年 | 11篇 |
1993年 | 14篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1982年 | 18篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 11篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 14篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 9篇 |
1930年 | 3篇 |
排序方式: 共有2259条查询结果,搜索用时 125 毫秒
981.
Julia N. Blyzniuk Michail A. Semenov Anna Victorovna Shestopalova 《Structural chemistry》2016,27(1):77-89
We report results of the Monte Carlo simulations of systems containing heterodimers of biological active ligands and water molecules. The study was designed to identify the possible formation of intermolecular hydrogen bonds in such systems in order to investigate the molecular mechanisms of hetero-association of aromatic ligands in aqueous solution. The geometry optimization and the calculation of the atomic charges of free ligands were carried out at DFT/B3LYP level of theory. Monte Carlo simulations with Metropolis algorithm were used to determine the low energy conformations of heterodimers in water clusters. The analysis of the Monte Carlo simulation results allows us to describe in detail the hydration properties of all investigated heterodimers and to determine the intermolecular hydrogen bonds between the functional donor–acceptor groups for some of hetero-associates under investigation. In the case of heterodimers without intermolecular hydrogen bonds, the additional stabilization of these hetero-complexes can be explained by the formation the water bridges between donor and acceptor groups of the ligands. 相似文献
982.
983.
Julia I. Schweizer Dr. Markus G. Scheibel Dr. Martin Diefenbach Felix Neumeyer Dr. Christian Würtele Dr. Natalia Kulminskaya Dr. Rasmus Linser Prof. Dr. Norbert Auner Prof. Dr. Sven Schneider Prof. Dr. Max C. Holthausen 《Angewandte Chemie (International ed. in English)》2016,55(5):1782-1786
An experimental and theoretical study of the base‐stabilized disilene 1 is reported, which forms at low temperatures in the disproportionation reaction of Si2Cl6 or neo‐Si5Cl12 with equimolar amounts of NMe2Et. Single‐crystal X‐ray diffraction and quantum‐chemical bonding analysis disclose an unprecedented structure in silicon chemistry featuring a dative Si→Si single bond between two silylene moieties, Me2EtN→SiCl2→Si(SiCl3)2. The central ambiphilic SiCl2 group is linked by dative bonds to the amine donor and the bis(trichlorosilyl)silylene acceptor, which leads to push–pull stabilization. Based on experimental and theoretical examinations a formation mechanism is presented that involves an autocatalytic reaction of the intermediately formed anion Si(SiCl3)3? with neo‐Si5Cl12 to yield 1 . 相似文献
984.
Yohei Nishidate Irina Khmyrova Julia Kholopova Evgeny Polushkin Bogdan Shevchenko Sergei Shapoval 《Optical Review》2016,23(5):798-805
Numerical model and procedure are developed to study the output optical performance of light-emitting diode (LED) in which injected current is spatially modulated by mesh-like top metal electrode. The mesh strips have rectangular crossection as in realistic LEDs. The finite element method is applied to obtain three-dimensional distributions of electric potential which are incorporated in the equations for total output power. The numerical procedure is applied to evaluate LED’s total output optical power at different geometric parameters of the electrode: the mesh pitch, the width, and the height of the top mesh-like electrodes. Modeling results demonstrate the effect of mesh pitch variation on the output optical power. In particular, at a certain value of the mesh pitch maximum total output optical power is revealed. The presented approach can be used in the optimization of the LEDs with designed metal electrodes. 相似文献
985.
Dr. Nikolaos Kaplaneris Alejandro Puet Felix Kallert Julia Pöhlmann Prof. Dr. Lutz Ackermann 《Angewandte Chemie (International ed. in English)》2023,62(9):e202216661
Bioorthogonal late-stage diversification of structurally complex peptides bears enormous potential for drug discovery and molecular imaging, among other applications. Herein, we report on a palladium-catalyzed C−H arylation of tryptophan-containing peptides with readily accessible and modular arylthianthrenium salts. Under exceedingly mild reaction conditions, the late-stage diversification of structurally complex peptides was accomplished. The tunability and ease of preparation of arylthianthrenium salts allowed the expedient stitching of tryptophan-containing peptides with drug, natural product, and peptidic scaffolds by forging sterically congested biaryl linkages. The robustness of the palladium catalysis regime was reflected by the full tolerance of a plethora of sensitive and coordinating functional groups. Hence, our manifold enabled efficient access to highly decorated, labelled, conjugated, and ligated linear and cyclic peptides. 相似文献
986.
Patricia Gomez de Santos Alejandro González-Benjumea Angela Fernandez-Garcia Carmen Aranda Yinqi Wu Andrada But Patricia Molina-Espeja Diana M. Maté David Gonzalez-Perez Wuyuan Zhang Jan Kiebist Prof. Katrin Scheibner Prof. Martin Hofrichter Katarzyna Świderek Prof. Vicent Moliner Prof. Julia Sanz-Aparicio Prof. Frank Hollmann Prof. Ana Gutiérrez Prof. Miguel Alcalde 《Angewandte Chemie (International ed. in English)》2023,62(9):e202217372
The hydroxylation of fatty acids is an appealing reaction in synthetic chemistry, although the lack of selective catalysts hampers its industrial implementation. In this study, we have engineered a highly regioselective fungal peroxygenase for the ω-1 hydroxylation of fatty acids with quenched stepwise over-oxidation. One single mutation near the Phe catalytic tripod narrowed the heme cavity, promoting a dramatic shift toward subterminal hydroxylation with a drop in the over-oxidation activity. While crystallographic soaking experiments and molecular dynamic simulations shed light on this unique oxidation pattern, the selective biocatalyst was produced by Pichia pastoris at 0.4 g L−1 in a fed-batch bioreactor and used in the preparative synthesis of 1.4 g of (ω-1)-hydroxytetradecanoic acid with 95 % regioselectivity and 83 % ee for the S enantiomer. 相似文献
987.
Ulrike Wirth Julia Erl Saphia Azzam Dr. Carina Höring Dr. Michael Skiba Ritu Singh Kathrin Hochmuth PD Dr. Max Keller Prof. Dr. Joachim Wegener Prof. Dr. Burkhard König 《Angewandte Chemie (International ed. in English)》2023,62(21):e202215547
G protein-coupled cell surface receptors (GPCR) trigger complex intracellular signaling cascades upon agonist binding. Classic pharmacological assays provide information about binding affinities, activation or blockade at different stages of the signaling cascade, but real time dynamics and reversibility of these processes remain often disguised. We show that combining photochromic NPY receptor ligands, which can be toggled in their receptor activation ability by irradiation with light of different wavelengths, with whole cell label-free impedance assays allows observing the cell response to receptor activation and its reversibility over time. The concept demonstrated on NPY receptors may be well applicable to many other GPCRs providing a deeper insight into the time course of intracellular signaling processes. 相似文献
988.
Simon de Graaff Marcel Eilers Julia Buschermöhle Nina Bengen Dr. Anna Dierks Dr. Marc Schmidtmann Dr. Manfred Manßen Prof. Dr. Rüdiger Beckhaus 《欧洲无机化学杂志》2023,26(5):e202200637
Bis(η5:η1-(di-para-tolyl)pentafulvene)niobium chloride ( 1 ) reacts with methyl lithium via salt metathesis to the methylated bis(pentafulvene)niobium complex 2 , and with lithium 2,6-diisopropylanilide addition and subsequent N−H bond activation to the imido mono(pentafulvene)niobium complex 3 . Avoiding the competing protonation of the chloride, bis(pentafulvene)niobium complex 2 reacts with primary aromatic and aliphatic amines to form terminal niobocene imido complexes, and with water to form the analog terminal oxo complex. Secondary methyl amines undergo a simultaneous N−H and C−H activation to form niobaaziridines under mild conditions. In contrast to other reported examples, 3 can be employed to investigate the uncontested reactivity of mono(pentafulvene)niobium complexes. Reaction with 4-tert-butylphenol selectively yields a niobocene phenolate complex. Unprecedented for mono(pentafulvene)niobium complexes, treating 3 with multiple-bond-containing substrates (nitriles, isocyanates) smoothly results the insertion into the Nb-Cexo σ-bond, forming the corresponding alkylidene amido and imidato complexes. 相似文献
989.
Hoan Minh Dinh Dr. Yu-Tao He Dr. Robert R. Fayzullin Dr. Serhii Vasylevskyi Dr. Eugene Khaskin Prof. Julia R. Khusnutdinova 《欧洲无机化学杂志》2023,26(32):e202300460
We report the synthesis of cyclometalated monoaryl MnIII fluoro complexes using bis(trifluoromethyl)zinc reagent, Zn(CF3)2(DMPU)2, under mild conditions via a reaction pathway that involves initial transmetalation followed by α-fluorine elimination. The formation of difluorocarbene in these reactions was detected by trapping experiments. Such facile difluorocarbene generation from MnIII results in moderate enhancement of difluoropropanation and difluoropropenation of alkenes and alkynes using Zn(CF3)2(DMPU)2 at lower temperature (20–60 °C) and short reaction time, suggesting potential application of manganese(III) perfluoroalkyl complexes as reactive species for carbene transfer reactivity. 相似文献
990.
Dr. Mohammed Mostafa Adnan Arpenik Kroyan Chaman Srivastava Dr. Sotirios Grammatikos Dr. Julia Glaum Dr. Marit-Helen Glomm Ese Dr. Sondre Kvalvåg Schnell Dr. Mari-Ann Einarsrud 《Chemphyschem》2023,24(11):e202200443
Improvements in the thermomechanical properties of epoxy upon inclusion of well-dispersed SiO2 nanoparticles have been demonstrated both experimentally and through molecular dynamics simulations. The SiO2 was represented by two different dispersion models: dispersed individual molecules and as spherical nanoparticles. The calculated thermodynamic and thermomechanical properties were consistent with experimental results. Radial distribution functions highlight the interactions of different parts of the polymer chains with the SiO2 between 3 and 5 nm into the epoxy, depending on the particle size. The findings from both models were verified against experimental results, such as the glass transition temperature and tensile elastic mechanical properties, and proved suitable for predicting thermomechanical and physicochemical properties of epoxy-SiO2 nanocomposites. 相似文献