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91.
Comparison of the activation time effects and the internal energy distributions for the CID,PQD and HCD excitation modes 下载免费PDF全文
Farid Ichou Adrian Schwarzenberg Denis Lesage Sandra Alves Christophe Junot Xavier Machuron‐Mandard Jean‐Claude Tabet 《Journal of mass spectrometry : JMS》2014,49(6):498-508
Reproducibility among different types of excitation modes is a major bottleneck in the field of tandem mass spectrometry library development in metabolomics. In this study, we specifically evaluated the influence of collision voltage and activation time parameters on tandem mass spectrometry spectra for various excitation modes [collision‐induced dissociation (CID), pulsed Q dissociation (PQD) and higher‐energy collision dissociation (HCD)] of Orbitrap‐based instruments. For this purpose, internal energy deposition was probed using an approach based on Rice–Rampserger–Kassel–Marcus modeling with three thermometer compounds of different degree of freedom (69, 228 and 420) and a thermal model. This model treats consecutively the activation and decomposition steps, and the survival precursor ion populations are characterized by truncated Maxwell–Boltzmann internal energy distributions. This study demonstrates that the activation time has a significant impact on MS/MS spectra using the CID and PQD modes. The proposed model seems suitable to describe the multiple collision regime in the PQD and HCD modes. Linear relationships between mean internal energy and collision voltage are shown for the latter modes and the three thermometer molecules. These results suggest that a calibration based on the collision voltage should provide reproducible for PQD, HCD to be compared with CID in tandem in space instruments. However, an important signal loss is observed in PQD excitation mode whatever the mass of the studied compounds, which may affect not only parent ions but also fragment ions depending on the fragmentation parameters. A calibration approach for the CID mode based on the variation of activation time parameter is more appropriate than one based on collision voltage. In fact, the activation time parameter in CID induces a modification of the collisional regime and thus helps control the orientation of the fragmentation pathways (competitive or consecutive dissociations). Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
92.
Maha Chaieb Héla Habli Leila Mejrissi Brahim Oujia Florent Xavier Gadéa 《International journal of quantum chemistry》2014,114(11):731-747
A wide adiabatic study is performed for NaRb molecule, involving 151Σ+ electronic states including the ionic state Na?Rb+, as well as 143Σ+, 1–91,3Π, and 1–51,3Δ states. This investigation is performed using an ab initio approach which involves the effective core potential, the core polarization potential with l‐dependent cut‐off functions. The NaRb system has been treated as a two‐electron system and the full valence configuration interaction is easily achieved. The spectroscopic constants Re, De, Te, ωe, ωexe, Be, and D0 for all these states are derived. We have also computed the vibrational levels as well their spacing for different values of J. In addition, permanent and transition dipole moments are determined and analyzed. The Dunham coefficients have been used to perform experimental spacing to compare directly with our results. The present calculations on NaRb extend previous theoretical works to numerous electronic excited states in the various symmetries. © 2014 Wiley Periodicals, Inc. 相似文献
93.
A Computational and Experimental Approach Linking Disorder,High‐Pressure Behavior,and Mechanical Properties in UiO Frameworks 下载免费PDF全文
Claire L. Hobday Ross J. Marshall Colin F. Murphie Jorge Sotelo Tom Richards Dr. David R. Allan Prof. Tina Düren Dr. François‐Xavier Coudert Dr. Ross S. Forgan Dr. Carole A. Morrison Dr. Stephen A. Moggach Dr. Thomas D. Bennett 《Angewandte Chemie (International ed. in English)》2016,55(7):2401-2405
Whilst many metal–organic frameworks possess the chemical stability needed to be used as functional materials, they often lack the physical strength required for industrial applications. Herein, we have investigated the mechanical properties of two UiO‐topology Zr‐MOFs, the planar UiO‐67 ([Zr6O4(OH)4(bpdc)6], bpdc: 4,4′‐biphenyl dicarboxylate) and UiO‐abdc ([Zr6O4(OH)4(abdc)6], abdc: 4,4′‐azobenzene dicarboxylate) by single‐crystal nanoindentation, high‐pressure X‐ray diffraction, density functional theory calculations, and first‐principles molecular dynamics. On increasing pressure, both UiO‐67 and UiO‐abdc were found to be incompressible when filled with methanol molecules within a diamond anvil cell. Stabilization in both cases is attributed to dynamical linker disorder. The diazo‐linker of UiO‐abdc possesses local site disorder, which, in conjunction with its longer nature, also decreases the capacity of the framework to compress and stabilizes it against direct compression, compared to UiO‐67, characterized by a large elastic modulus. The use of non‐linear linkers in the synthesis of UiO‐MOFs therefore creates MOFs that have more rigid mechanical properties over a larger pressure range. 相似文献
94.
Three alternative syntheses of 1,3,5,7-tetraiodotricyclo[3.3.0.03,7]octane are described. Reaction of this tetraiodide with sodium amalgam in the presence of dienes or with molten sodium in boiling 1,4-dioxane in the absence of trapping agents led to very complex mixtures of products, presumably due to competitive 1,2- and 1,3-deiodination reactions. 相似文献
95.
Victoria E. Campbell Xavier de Hatten Dr. Nicolas Delsuc Dr. Brice Kauffmann Dr. Ivan Huc Dr. Jonathan R. Nitschke Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(25):6138-6142
Systemic change : A system of transformations between helical structures was observed to be governed by interactions mediated by the electronic effects of substituents, entropic effects, the conformational preferences of organic building blocks, and the coordinative preferences of the metal ion. All of these effects were important, but all must be considered together to allow the prediction of the product observed (see scheme).
96.
Asensio González Xavier Solans Elies Molins 《Journal of organometallic chemistry》2008,693(12):2119-2131
The synthesis and characterization of pyrazole derivatives of general formula [C6H4-4-R-1-{(3,5-Me2-C3N2)-CH2-(η5-C5H4)Fe(η5-C5H5)}] [R = OMe (1a) or H (1b)] with a ferrocenylmethyl substituent are described.The study of the reactivity of compounds 1 with palladium(II) acetate has allowed the isolation of complexes (μ-AcO)2[Pd{κ2-C,N-C6H3-4-R-1-[(3,5-Me2-C3N2)-CH2-(η5-C5H4)Fe(η5-C5H5)]}]2 (2) [R = OMe (2a) or H (2b)] that contain a bidentate [C(sp2, phenyl), N]− ligand and a central “Pd(μ-AcO)2Pd” unit.Furthermore, treatment of 2 with LiCl produced complexes (μ-Cl)2[Pd{κ2-C,N-C6H3-4-R-1-[(3,5-Me2-C3N2)-CH2-(η5-C5H4)Fe(η5-C5H5)]}]2 (3) [R = OMe (3a) or H (3b)] that arise from the replacement of the acetato ligands by the Cl−.Compounds 2 and 3 also react with PPh3 giving the monomeric complexes [Pd{κ2-C,N-C6H3-4-R-1-[(3,5-Me2-C3N2)-CH2-(η5-C5H4)Fe(η5-C5H5)]}X(PPh3)] {X− = AcO− and R = OMe (5a) or H (5b) or X− = Cl− and R = OMe (6a) or H (6b)}, where the phosphine is in a cis-arrangement to the metallated carbon atom. Treatment of 3 with thallium(I) acetylacetonate produced [Pd{κ2-C,N-C6H3-4-R-1-[(3,5-Me2-C3N2)-CH2-(η5-C5H4)Fe(η5-C5H5)]}(acac)] (7) [R = OMe (7a) or H (7b)]. Electrochemical studies of the free ligands and the cyclopalladated complexes are also reported. The dimeric complexes 3 also react with MeO2C-CC-CO2Me (in a 1:4 molar ratio) giving [Pd{(MeO2C-CC-CO2Me)2C6H3-4-R-1-[(3,5-Me2-C3N2)-CH2-(η5-C5H4)Fe(η5-C5H5)]}Cl] (8) [R = OMe (8a) or H (8b)], which arise from the bis(insertion) of the alkyne into the σ{Pd-C(sp2, phenyl)} bond of 3. 相似文献
97.
Stability of silanols and grafted alkylsilane monolayers on plasma-activated mica surfaces 总被引:1,自引:0,他引:1
Liberelle B Banquy X Giasson S 《Langmuir : the ACS journal of surfaces and colloids》2008,24(7):3280-3288
We investigated the effect of physical and chemical modifications of mica surfaces induced by water vapor-based plasma treatments on the stability of silanols and grafted alkylsilane monolayers. The plasma-activated substrates were characterized using XPS, TOF-SIMS, and contact angle measurements. They revealed a large surface coverage of silanol groups (Si-OH) and a loss of aluminum atoms compared to freshly cleaved mica surfaces. The stability of plasma-induced silanol groups was investigated by contact angle measurements using ethylene glycol as a probe liquid. The Si-OH surface coverage decreased rapidly under vacuum or thermal treatment to give rise to hydrophobic dehydrated surfaces. The stability of end-grafted monofunctionalized n-alkylsilanes was investigated in different solvents and at different pH using water contact angle measurements. The degrafting of alkylsilanes from the activated mica was promoted in acidic aqueous solutions. This detachment was associated with the hydrolysis of covalent bonds between the alkylsilanes and the mica surface. The monolayer stability was enhanced by increasing the length of the alkyl chains that probably act as a hydrophobic protective layer against hydrolysis reactions. Stable alkylsilane monolayers in water with pH greater than 5.5 were obtained on mica surfaces activated at low plasma pressure. We attributed this stability to the loss of surface Al atoms induced by the plasma treatment. 相似文献
98.
99.
100.
Adrian M. Tomuta Xavier Fernández‐Francos Francesc Ferrando Xavier Ramis Àngels Serra 《先进技术聚合物》2013,24(11):962-970
A hyperbranched aromatic polyester (HBPOH) has been synthesized, and poly(ε‐caprolactone) arms have been grown on some of its end hydroxyl groups (HBPCL). These modifiers have been used in cationic diglycidyl ether of bisphenol A formulations cured with ytterbium triflate as cationic initiator. The effect of HBPOH and HBPCL on the curing kinetics has been studied using differential scanning calorimetry (DSC). The obtained materials have been characterized by dynamomechanical analysis, DSC, thermogravimetric analysis and mechanical tests. The modifiers are incorporated into the thermosetting network because of the participation of the end hydroxyl groups in the cationic curing of epoxides by the activated monomer mechanism. Homogeneous thermosets have been obtained with a remarkable increase in impact strength without sacrificing elastic modulus or hardness. A compromise between the rigid structure of the aromatic hyperbranched core and the flexibilizing effect of the poly(ε‐caprolactone) arms is believed to be responsible for the overall thermal and mechanical properties of the materials. The use of these polymeric modifiers increases the thermal stability of the resulting materials because of the low degradability of the aromatic ester groups in the hyperbranched core and the incorporation of the modifier into the network structure. However, the presence of such ester groups makes them reworkable by hydrolysis or alcoholysis in an alkaline medium, thus opening a way for recovery of valuable substrates. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献