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971.
Dr. Monika Srebro Dr. Emmanuel Anger Barry Moore II Dr. Nicolas Vanthuyne Prof. Christian Roussel Prof. Régis Réau Prof. Jochen Autschbach Dr. Jeanne Crassous 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(47):17100-17115
The properties of mono‐ and bis‐Ru–vinyl[6]helicene complexes ( 2 a and 2 b , respectively), recently synthesized by using molecular engineering of helicenes based on the grafting of lateral organometallic substituents on the π‐helical backbone through a vinyl bridge, are presented. These helicene derivatives are thoroughly characterized, with special attention given to their chiroptical properties and redox switching activity. The UV/Vis and electronic circular dichroism (ECD) spectra of P and M enantiopure species, both in the neutral and oxidized states ([ 2 a ] . +, [ 2 b ] . +, and [ 2 b ]2+), are analyzed with the aid of quantum‐chemical calculations. The extended π‐conjugation facilitated by the vinyl moiety, clearly visible in the electronic structures of 2 a , b , introduces new active bands in the ECD spectra that consequently lead to a significant increase in optical rotation of Ru–vinylhelicenes compared with the organic precursors. The vibrational circular dichroism (VCD) spectra were measured and calculated for both the organic and organometallic species and constitute the first examples of VCD for metal‐based helicene derivatives. Finally, the redox‐triggered chiroptical switching activity of 2 a , b is examined in detail by using ECD spectroscopy. The modifications of the ECD spectra in the UV/Vis and NIR region are well reproduced and rationalized by calculations. 相似文献
972.
Modeling of Structural,Energetic, and Dynamic Properties of Few‐Atom Silver Clusters Embedded in Polynucleotide Strands by Using Molecular Dynamics 下载免费PDF全文
Dr. Nicolas Staelens Dr. Laurence Leherte Prof. Benoît Champagne Prof. Daniel P. Vercauteren 《Chemphyschem》2015,16(2):360-369
This work concerns the study of the structural, energetic, and dynamic properties of fluorescent systems composed of silver clusters stabilized by polynucleotide strands. To do so, classical interaction potentials relative to silver, neutral and cationic, were introduced in the AMBER force field. Molecular dynamics simulations allowed analysis of the nature and force of the interactions between the various parts of the nucleic oligomers and the silver clusters. Conformational analyses were necessary to explore the flexibility of the supramolecular assemblies, specifically by radial distribution functions and Ramachandran‐type maps. 相似文献
973.
Understanding J‐Modulation during Spatial Encoding for Sensitivity‐Optimized Ultrafast NMR Spectroscopy 下载免费PDF全文
Boris Gouilleux Laetitia Rouger Benoît Charrier Dr. Ilya Kuprov Prof. Serge Akoka Dr. Jean‐Nicolas Dumez Dr. Patrick Giraudeau 《Chemphyschem》2015,16(14):3093-3100
Ultrafast (UF) NMR spectroscopy is an approach that yields 2D spectra in a single scan. This methodology has become a powerful analytical tool that is used in a large array of applications. However, UF NMR spectroscopy still suffers from an intrinsic low sensitivity, and from the need to compromise between sensitivity, spectral width, and resolution. In particular, the modulation of signal intensities by the spin–spin J‐coupling interaction (J‐modulation) impacts significantly on the intensities of the spectral peaks. This effect can lead to large sensitivity losses and even to missing spectral peaks, depending on the nature of the spin system. Herein, a general simulation package (Spinach) is used to describe J‐modulation effects in UF experiments. The results from simulations match with experimental data and the results of product operator calculations. Several methods are proposed to optimize the sensitivity in UF COSY spectra. The potential and drawbacks of the different strategies are also discussed. These approaches provide a way to adjust the sensitivity of UF experiments for a large range of applications. 相似文献
974.
Single‐Scan Multidimensional NMR Analysis of Mixtures at Sub‐Millimolar Concentrations by using SABRE Hyperpolarization 下载免费PDF全文
Dr. Valeria Daniele Dr. François‐Xavier Legrand Dr. Patrick Berthault Dr. Jean‐Nicolas Dumez Dr. Gaspard Huber 《Chemphyschem》2015,16(16):3413-3417
Signal amplification by reversible exchange (SABRE) is a promising method to increase the sensitivity of nuclear magnetic resonance (NMR) experiments. However, SABRE‐enhanced 1H NMR signals are short lived, and SABRE is often used to record 1D NMR spectra only. When the sample of interest is a complex mixture, this results in severe overlaps for 1H spectra. In addition, the use of a co‐substrate, whose signals may obscure the 1H spectra, is currently the most efficient way to lower the detection limit of SABRE experiments. Here, we describe an approach to obtain clean, SABRE‐hyperpolarized 2D 1H NMR spectra of mixtures of small molecules at sub‐millimolar concentrations in a single scan. The method relies on the use of para‐hydrogen together with a deuterated co‐substrate for hyperpolarization and ultrafast 2D NMR for acquisition. It is applicable to all substrates that can be polarized with SABRE. 相似文献
975.
Straightforward Synthesis of 5‐Bromopenta‐2,4‐diynenitrile and Its Reactivity Towards Terminal Alkynes: A Direct Access to Diene and Benzofulvene Scaffolds 下载免费PDF全文
Dr. Nicolas Kerisit Dr. Loïc Toupet Dr. Jean‐Claude Guillemin Dr. Yann Trolez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(16):6042-6047
The high‐yielding synthesis of 5‐bromopenta‐2,4‐diynenitrile (BrC5N) was achieved for the first time. Its reactivity with triisopropylsilylacetylene and triisopropylsilylbutadiyne in the presence of copper and palladium as co‐catalysts and diisopropylamine was evaluated. It revealed an unprecedented cascade reaction leading to a diene in one case and to a benzofulvene in the other case, with a unique structure. Both of them were characterized by X‐ray crystallography, among other techniques. The mechanism of the reaction leading to the diene was investigated experimentally. Theoretical calculations at the DFT level suggest that the mechanism leading to the benzofulvene relies on a hexa‐dehydro Diels–Alder (HDDA)‐type of mechanism. This work constitutes an example of an unanticipated reactivity leading to an important increase of chemical complexity. 相似文献
976.
Pyridyl‐Functionalised 3H‐1,2,3,4‐Triazaphospholes: Synthesis,Coordination Chemistry and Photophysical Properties of Low‐Coordinate Phosphorus Compounds 下载免费PDF全文
Julian A. W. Sklorz Santina Hoof Nadine Rades Dr. Nicolas De Rycke László Könczöl Dr. Dénes Szieberth Manuela Weber Dr. Jelena Wiecko Prof. Dr. László Nyulászi Prof. Dr. Muriel Hissler Prof. Dr. Christian Müller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(31):11096-11109
Novel conjugated, pyridyl‐functionalised triazaphospholes with either tBu or SiMe3 substituents at the 5‐position of the N3PC heterocycle have been prepared by a [3+2] cycloaddition reaction and compared with structurally related, triazole‐based systems. Photoexcitation of the 2‐pyridyl‐substituted triazaphosphole gives rise to a significant fluorescence emission with a quantum yield of up to 12 %. In contrast, the all‐nitrogen triazole analogue shows no emission at all. DFT calculations indicate that the 2‐pyridyl substituted systems have a more rigid and planar structure than their 3‐ and 4‐pyridyl isomers. Time‐dependent (TD) DFT calculations show that only the 2‐pyridyl‐substituted triazaphosphole exhibits similar planar geometry, with matching conformational arrangements in the lowest energy excited state and the ground state; this helps to explain the enhanced emission intensity. The chelating P,N‐hybrid ligand forms a ReI complex of the type [(N^N)Re(CO)3Br] through the coordination of nitrogen atom N2 to the metal centre rather than through the phosphorus donor. Both structural and spectroscopic data indicate substantial π‐accepting character of the triazaphosphole, which is again in contrast to that of the all‐nitrogen‐containing triazoles. The synthesis and photophysical properties of a new class of phosphorus‐containing extended π systems are described. 相似文献
977.
Epitope mapping of 7S cashew antigen in complex with antibody by solution‐phase H/D exchange monitored by FT‐ICR mass spectrometry 下载免费PDF全文
Xiaoyan Guan Kyle A. Noble Yeqing Tao Kenneth H. Roux Shridhar K. Sathe Nicolas L. Young Alan G. Marshall 《Journal of mass spectrometry : JMS》2015,50(6):812-819
The potential epitope of a recombinant food allergen protein, cashew Ana o 1, reactive to monoclonal antibody, mAb 2G4, has been mapped by solution‐phase amide backbone H/D exchange (HDX) monitored by Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR MS). Purified mAb 2G4 was incubated with recombinant Ana o 1 (rAna o 1) to form antigen:monoclonal antibody (Ag:mAb) complexes. Complexed and uncomplexed (free) rAna o 1 were then subjected to HDX‐MS analysis. Five regions protected from H/D exchange upon mAb binding are identified as potential conformational epitope‐contributing segments. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
978.
Ultrasensitive Direct Quantification of Nucleobase Modifications in DNA by Surface‐Enhanced Raman Scattering: The Case of Cytosine 下载免费PDF全文
Judit Morla‐Folch Dr. Hai‐nan Xie Patricia Gisbert‐Quilis Dr. Sara Gómez‐de Pedro Dr. Nicolas Pazos‐Perez Prof. Dr. Ramon A. Alvarez‐Puebla Dr. Luca Guerrini 《Angewandte Chemie (International ed. in English)》2015,54(46):13650-13654
Recognition of chemical modifications in canonical nucleobases of nucleic acids is of key importance since such modified variants act as different genetic encoders, introducing variability in the biological information contained in DNA. Herein, we demonstrate the feasibility of direct SERS in combination with chemometrics and microfluidics for the identification and relative quantification of 4 different cytosine modifications in both single‐ and double‐stranded DNA. The minute amount of DNA required per measurement, in the sub‐nanogram regime, removes the necessity of pre‐amplification or enrichment steps (which are also potential sources of artificial DNA damages). These findings show great potentials for the development of fast, low‐cost and high‐throughput screening analytical devices capable of detecting known and unknown modifications in nucleic acids (DNA and RNA) opening new windows of activity in several fields such as biology, medicine and forensic sciences. 相似文献
979.
A benzophenone‐naphthalimide derivative as versatile photoinitiator of polymerization under near UV and visible lights 下载免费PDF全文
Jing Zhang Nicolas Zivic Frédéric Dumur Pu Xiao Bernadette Graff Didier Gigmes Jean Pierre Fouassier Jacques Lalevée 《Journal of polymer science. Part A, Polymer chemistry》2015,53(3):445-451
A benzophenone‐naphthalimide derivative (BPND) bearing tertiary amine groups has been developed as a high‐performance photoinitiator in combination with 2,4,6‐tris(trichloromethyl)‐1,3,5‐triazine or an iodonium salt for both the free radical polymerization (FRP) of acrylates and the cationic polymerization (CP) of epoxides upon exposure to near UV and visible LEDs (385–470 nm). BPND can even produce radicals without any added hydrogen donor. The photochemical mechanisms are studied by molecular orbital calculations, steady state photolysis, electron spin resonance spin trapping, fluorescence, cyclic voltammetry and laser flash photolysis techniques. These novel BPND based photoinitiating systems exhibit an efficiency higher than that of the well‐known camphorquinone‐based systems (FRP and CP) or comparable to that of bis(2,4,6‐trimethylbenzoyl)‐phenylphosphineoxide (FRP at λ ≤ 455 nm). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 445–451 相似文献
980.
Photophysics of Acetophenone Interacting with DNA: Why the Road to Photosensitization is Open 下载免费PDF全文
Miquel Huix‐Rotllant Elise Dumont Nicolas Ferré Antonio Monari 《Photochemistry and photobiology》2015,91(2):323-330
Deoxyribonucleic acid photosensitization, i.e. the photoinduced electron‐ or energy‐transfer of chromophores interacting with DNA, is a crucial phenomenon that triggers important DNA lesions such as pyrimidine dimerization, even upon absorption of relatively low‐energy radiation. Oxidative lesions may also be produced via the photoinduced production of reactive oxygen species. Aromatic ketones, and acetophenone in particular, are well known for their sensitization effects. In this contribution we model the structural and dynamical properties of the acetophenone/DNA aggregates as well as their spectroscopic and photophysical properties using high‐level hybrid quantum mechanics/molecular mechanics methods. We show that the key steps of the photochemistry of acetophenone in gas phase are conserved in the macromolecular environment and thus an ultrafast singlet–triplet conversion of acetophenone is expected prior to the transfer to DNA. 相似文献