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921.
《Surface and interface analysis : SIA》2005,37(9):737-742
A novel method that allows the determination of the electrical potential of a polymer surface has been applied for polypropylene film treated by N2 + H2 cold plasma. The plasma treatment results in formation on the film surface of NH2 groups, which then gets transformed to NH3+ in contact with an electrolyte and leads to the formation of an electrical double layer. The method consists of theoretical calculation of electrical model potential, using the measurement of the electrical capacitance of the film in contact with an electrolyte by dielectric spectroscopy. Comparison with the results obtained by theoretical model shows similar dependencies of the electrical potential as a function of amino‐groups density and electrolyte concentration, but systematic differences of absolute values are observed. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
922.
In this article, we present a Python‐based library of high quality semi‐global potential energy surfaces for 50 polyatomic molecules with up to six atoms. We anticipate that these surfaces will find widespread application in the testing of new potential energy surface construction algorithms and nuclear ro‐vibrational structure theories. To this end, we provide the ability to generate the energy derivatives required for Taylor series expansions to sixth order about any point on the potential energy surface in a range of common coordinate systems, including curvilinear internal, Cartesian, and normal mode coordinates. The PyPES package, along with FORTRAN, C, MATLAB and Mathematica wrappers, is available at http://sourceforge.net/projects/pypes-lib . © 2015 Wiley Periodicals, Inc. 相似文献
923.
Yoshihiro Sugi 《中国化学会会志》2010,57(1):1-13
Steric interaction of reagents with zeolites was studied in isopropylation, sec‐butylation, and tert‐butylation of naphthalene (NP) over several large‐pore zeolites to elucidate the mechanism of selective catalysis. Selectivities for dialkylnaphthalene (DAN) isomers were influenced by the type of zeolite and bulkiness of alkylating agent. Selective formation of β,β‐ and 2,6‐diisopropylnaphthalene (DIPN) occurred only over H‐mordenite (MOR) in the isopropylation of NP using propene; bulky transition states of α,α‐ and α,β‐DIPN are excluded because of steric restriction by the channels, resulting in selective formation of β,β‐ and 2,6‐DIPN. However, low selectivities for β,β‐ and 2,6‐DIPN were observed over the zeolites, SSZ‐24 (AFI), SSZ‐55 (ATS), and SSZ‐42 (IFR) with 12‐membered‐ring (12‐MR) pore entrances of one‐dimensional channels, CIT‐5 (CFI), UTD‐1 (DON), and SSZ‐53 (SFH) with 14‐membered‐ring (14‐MR) pore entrances of one‐dimensional channels, and Y‐zeolite (FAU), zeolite β (BEA), and CIT‐1 (CON) with 12‐MR pore entrances of three‐dimensional channels, because their channels are too large for the exclusion of bulky isomers. Catalysis over these zeolites occurs under kinetic and/or thermodynamic control, resulting in predominant formation of α,α‐ and α,β‐DIPN at lower temperatures and an increase of the stable isomer β,β‐DIPN at higher temperatures. The selectivities for β,β‐ and 2,6‐DAN were enhanced with the increase in bulkiness of alkylating agents: 1‐butene for sec‐butylation and 2‐methylpropene for tert‐butylation. In particular, β,β‐di‐tert‐butylnaphthalene (DTBN) was selectively formed in the tert‐butylation. The selectivities for β,β‐ and 2,6‐DAN were enhanced even in large channels: the transition states of the least bulky isomers only fit the channels because other bulky isomers are excluded by steric restriction of the channels. However, tert‐butylation over FAU, BEA, and CON had selectivities for 2,6‐DTBN of around 50–60%, although selectivities for β,β‐DTBN were almost 100% selectivity; these zeolites can hardly recognize the differences between 2,6‐ and 2,7‐DTBN. The results indicate that the fitting of the least bulky isomers to zeolite channels, leading to the exclusion of other bulky isomers, is essential for highly shape‐selective catalysis. 相似文献
924.
S. Cordier F. Dorson F. Grasset Y. Molard B. Fabre H. Haneda T. Sasaki M. Mortier S. Ababou-Girard C. Perrin 《Journal of Cluster Science》2009,20(1):9-21
In this contribution, we present a review of our recent works about the design of phosphor nanoparticles and materials based
on [Mo6X14]2− cluster units (X = Cl, Br, I) as well as the functionalization of monocrystalline Si(111) surfaces by Mo6 clusters. Our purpose was to use the specific properties of cluster units found in inorganic solids for the design of new
nanomaterials with potential applications in nanotechnologies (e.g. phosphor dyes for bio labelling, light emitting diodes,
redox active molecular junctions…) using soft chemistry techniques. Phosphor Cs2Mo6X14@SiO2 nanoparticles emitting in 550–900 nm upon photo-excitation were synthesised using a ‘water in oil’ microemulsion technique.
They exhibit a regular shape (~45 nm) and are based on [Mo6X14]2− cluster units and Cs+ counter cations embedded in a silica matrix. ((n–C4H9)4N)2Mo6Br14@ZnO colloids and nanopowders are based on the association of ZnO crystalline nano-particles with Mo6 cluster units adsorbed on their surface. They exhibit a large emission window in the visible region that can be tuned by
modulation of the excitation wave length in order to selectively obtain the emission of either clusters units or ZnO nanocrystals
or of both entities. Functionalized surfaces were obtained by the attachment of cluster units on a Si(111) surface through
pyridine end capped organic chains using a multi-step procedure. Modified surfaces were characterized by X-ray photoemission
spectroscopy (XPS), atomic force microscopy (AFM), IR and electrochemical analysis. The surface coverage can be modulated
by the controlled introduction of inert organic chains among pyridine end-capped ones before the cluster anchoring step. 相似文献
925.
The electrochemical processes at the interface between solid fluorine-conducting electrolyte LaF3(Eu2+ 0.8 mol %) and silver or bismuth electrodes in the two-electrode cell with nonpolarizable reference electrode are studied using the galvanostatic method. The anodic galvanostatic transients of LaF3: Eu2+/Ag and LaF3: Eu2+/Bi interfaces are linearized on the log(η ? ηmax), vs. t coordinates, i.e. the rate of LaF3|MF n |M electrode formation is limited by slow surface diffusion of metal adions. The initial portions of cathodic galvanostatic transients in the range of solid-electrolyte lanthanum reduction are approximated by the linear dependence of η on log(1 ? √t/τ). The plots of logI vs. 1/η are linear both for the lanthanum reduction and for silver and bismuth oxidation involving mobile fluoride ion of solid electrolyte, which is typical for two-dimensional growth of new phase. 相似文献
926.
J. Agrisuelas J. J. García-Jareño D. Gimenez-Romero F. Negrete F. Vicente 《Journal of Solid State Electrochemistry》2009,13(10):1599-1603
Electrochemical techniques are applied to estimate the fractal dimension value of electroactive surface structures. However,
the fractal dimension value is an abstract concept, which sometimes is hard to understand. Herein, this abstract concept is
used to calculate the fractional content of the nickel/graphite–polypropylene hybrid composite material, putting into practice
this concept in the study of composite materials. 相似文献
927.
The self-motion of a benzoquinone (BQ) disk on NADPH was investigated as the coupling of an autonomous motor and an enzyme reaction. In the absence of the enzyme reaction, features of motion changed depending on the concentration of NADPH, that is, continuous motion→ intermittent oscillatory motion→ no motion. When the reverse reaction from NADP(+) to NADPH was introduced into the system with the addition of an enzyme reaction, continuous motion changed to intermittent oscillatory motion with small amplitude. The mechanism of this mode change is discussed in relation to the surface tension as a driving force and the time course of UV spectra as a window to the progress of the reaction. Characteristic features of the mode change were qualitatively reproduced by a numerical calculation. 相似文献
928.
Schwizer D Patton JT Cutting B Smieško M Wagner B Kato A Weckerle C Binder FP Rabbani S Schwardt O Magnani JL Ernst B 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(5):1342-1351
A new class of N-acetyl-D-glucosamine (GlcNAc) mimics for E-selectin antagonists was designed and synthesized. The mimic consists of a cyclohexane ring substituted with alkyl substituents adjacent to the linking position of the fucose moiety. Incorporation into E-selectin antagonists led to the test compounds 8 and the 2'-benzoylated analogues 21, which exhibit affinities in the low micromolar range. By using saturation transfer difference (STD)-NMR it could be shown that the increase in affinity does not result from an additional hydrophobic contact of the alkyl substituent with the target protein E-selectin, but rather from a steric effect stabilizing the antagonist in its bioactive conformation. The loss of affinity found for antagonists 10 and 35 containing a methyl substituent in a remote position (and therefore unable to support to the stabilization of the core) further supports this hypothesis. Finally, when a GlcNAc mimetic containing two methyl substituents (52 and 53) was used, in which one methyl was positioned adjacent to the fucose linking position and the other was in a remote position, the affinity was regained. 相似文献
929.
Cooper R Bartels C Kandratsenka A Rahinov I Shenvi N Golibrzuch K Li Z Auerbach DJ Tully JC Wodtke AM 《Angewandte Chemie (International ed. in English)》2012,51(20):4954-4958
Surface phenomena: measurements of absolute probabilities are reported for the vibrational excitation of NO(v=0→1,2) molecules scattered from a Au(111) surface. These measurements were quantitatively compared to calculations based on ab?initio theoretical approaches to electronically nonadiabatic molecule-surface interactions. Good agreement was found between theory and experiment (see picture; T(s) =surface temperature, P=excitation probability, and E=incidence energy of translation). 相似文献
930.