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91.
Silke C. Wenzel Holger Hoffmann Jidong Zhang Laurent Debussche Sabine Haag‐Richter Michael Kurz Frederico Nardi Peer Lukat Irene Kochems Heiko Tietgen Dietmar Schummer Jean‐Paul Nicolas Loreley Calvet Valerie Czepczor Patricia Vrignaud Agnes Mühlenweg Stefan Pelzer Rolf Müller Mark Brnstrup 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(51):15781-15785
92.
Investigating Asymptotic Suction Boundary Layers using a One-Dimensional Stochastic Turbulence Model
The one-dimensional turbulence model (ODT) is applied to study turbulent asymptotic suction boundary layers for a Reynolds number of Re = u∞/v0 = 333, where u∞ and v0 are the free stream and suction velocity, respectively. In here we will demonstrate that a large eddy suppression mechanism may reduce the influence of ODT model parameters, such as the viscous cut-off parameter Z. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
93.
Kuemin C Stutz R Spencer ND Wolf H 《Langmuir : the ACS journal of surfaces and colloids》2011,27(10):6305-6310
Capillary assembly was explored for the precise placement of 25 nm × 70 nm colloidal gold nanorods on prestructured poly(dimethylsiloxane) template surfaces. The concentration of nanorods and cationic surfactant cetyltrimethylammonium bromide (CTAB), the template wettability, and most critically the convective transport of the dispersed nanorods were tuned to study their effect on the resulting assembly yield. It is shown that gold nanorods can be placed into arrayed 120-nm diameter holes, achieving assembly yields as high as 95% when the local concentration of nanorods at the receding contact line is sufficiently high. Regular arrays of gold nanorods have several benefits over randomly deposited nanorod arrangements. Each assembled nanorod resides at a precisely defined location and can easily be found for subsequent characterization or direct utilization in a device. The former is illustrated by collecting scattering spectra from single nanorods and nanorod dimers, followed by subsequent SEM characterization without the need for intricate registration schemes. 相似文献
94.
Cole JJ Barry CR Knuesel RJ Wang X Jacobs HO 《Langmuir : the ACS journal of surfaces and colloids》2011,27(11):7321-7329
Contact electrification creates an invisible mark, overlooked and often undetected by conventional surface spectroscopic measurements. It impacts our daily lives macroscopically during electrostatic discharge and is equally relevant on the nanoscale in areas such as soft lithography, transfer, and printing. This report describes a new conceptual approach to studying and utilizing contact electrification beyond prior surface force apparatus and point-contact implementations. Instead of a single point contact, our process studies nanocontact electrification that occurs between multiple nanocontacts of different sizes and shapes that can be formed using flexible materials, in particular, surface-functionalized poly(dimethylsiloxane) (PDMS) stamps and other common dielectrics (PMMA, SU-8, PS, PAA, and SiO(2)). Upon the formation of conformal contacts and forced delamination, contacted regions become charged, which is directly observed using Kelvin probe force microscopy revealing images of charge with sub-100-nm lateral resolution. The experiments reveal chemically driven interfacial proton exchange as the dominant charging mechanism for the materials that have been investigated so far. The recorded levels of uncompensated charges approach the theoretical limit that is set by the dielectric breakdown strength of the air gap that forms as the surfaces are delaminated. The macroscopic presence of the charges is recorded using force-distance curve measurements involving a balance and a micromanipulator to control the distance between the delaminated objects. Coulomb attraction between the delaminated surfaces reaches 150 N/m(2). At such a magnitude, the force finds many applications. We demonstrate the utility of printed charges in the fields of (i) nanoxerography and (ii) nanotransfer printing whereby the smallest objects are ~10 nm in diameter and the largest objects are in the millimeter to centimeter range. The printed charges are also shown to affect the electronic properties of contacted surfaces. For example, in the case of a silicon-on-insulator field effect transistors are in contact with PDMS and subsequent delamination leads to threshold voltage shifts that exceed 500 mV. 相似文献
95.
Tietze LF Schmuck K Schuster HJ Müller M Schuberth I 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(6):1922-1929
Chemotherapy of malign tumors is usually associated with serious side effects as common anticancer drugs lack selectivity. An approach to deal with this problem is the antibody-directed enzyme prodrug therapy (ADEPT) and the prodrug monotherapy (PMT). Herein, the synthesis and biological evaluation of new glycosidic prodrugs suitable for both concepts are described. All prodrugs but one are stable in human serum and show QIC(50) values (IC(50) of prodrug/IC(50) of prodrug in the presence of the appropriate glycohydrolase) of up to 6500. This is the best value found so far for compounds interacting with DNA. 相似文献
96.
Leutbecher H Greiner G Amann R Stolz A Beifuss U Conrad J 《Organic & biomolecular chemistry》2011,9(8):2667-2673
Laccase-catalyzed oxidation of substituted catechols followed by reaction with 4-hydroxy-pyrone/-benzopyrone afforded substituted benzofuran regioisomers whose structures with only two aromatic protons in total prevent a rapid structural assignment. Based on the evaluation of (1)H-(13)C long-range coupling constants a rule of thumb could be deduced for an easy and unambiguous differentiation between the possible regioisomers formed. DFT frontier orbital calculations of the reactants offer an interesting tool to explain the regioselectivity of the key reaction. 相似文献
97.
In this survey recent results about q-analogues of some classical theorems in extremal set theory are collected. They are related to determining the chromatic number of the q-analogues of Kneser graphs. For the proof one needs results on the number of 0-secant subspaces of point sets, so in the second part of the paper recent results on the structure of point sets having few 0-secant subspaces are discussed. Our attention is focussed on the planar case, where various stability results are given. 相似文献
98.
We report a structural characterization using X-ray absorption spectroscopy of the molybdenum site of Escherichia coli YedY, a novel oxidoreductase related to be the sulfite oxidase family of molybdenum enzymes. We find that the enzyme can exist in Mo(V) and Mo(IV) oxidation states but cannot be readily oxidized to the Mo(VI) form. Mo(V) YedY has molybdenum coordination similar to that of sulfite oxidase, with one Mo═O at 1.71 ?, three Mo-S at 2.39 ?, and one Mo-OH at 2.09 ?, which elongates to 2.20 ? upon reduction to Mo(IV), indicating Mo-OH(2) coordination. The Mo(V) enzyme also possesses a long Mo-O coordination at 2.64 ?, which may be due to oxygen coordination by Asn-45 O(δ), with Mo-O(δ) approximately trans to the Mo═O group. A comparison with sulfite oxidase indicates that YedY possesses a much more uniform Mo-S coordination, with a maximum permitted deviation of less than 0.05 ?. Our results indicate that the YedY active site shows considerable similarity to but also important differences from that of reduced forms of sulfite oxidase. 相似文献
99.
In this work, we study condensation phase transitions of two-dimensional Stockmayer fluids under additional external fields using Monte-Carlo (MC) simulations in the grand-canonical ensemble. We employ two recently developed methods to determine phase transitions in fluids, namely Wang-Landau (WL) MC simulations and successive-umbrella (SU) sampling. Considering first systems in zero field (and dipolar coupling strengths μ(2)∕εσ(3) ≤ 6), we demonstrate that the two techniques yield essentially consistent results but display pronounced differences in terms of efficiency. Indeed, comparing the computation times for these systems on a qualitative level, the SU sampling turns out to be significantly faster. In the presence of homogeneous external fields, however, the SU method becomes plagued by pronounced sampling difficulties, yielding the calculation of coexistence lines essentially impossible. Employing the WL scheme, on the other hand, we find phase coexistence even for strongly field-aligned systems. The corresponding critical temperatures are significantly shifted relative to the zero-field case. 相似文献
100.
Fortman GC Jacobsen H Cavallo L Nolan SP 《Chemical communications (Cambridge, England)》2011,47(34):9723-9725
The catalytic activity of a series of coordinatively unsaturated NHC-M(III) (M = Rh, Ir; NHC = N-heterocyclic carbene) complexes was tested in the deuteration of secondary and tertiary silanes. Among these, [IrCl(I(t)Bu')(2)] provides the highest conversions to the deuterated species. Mechanistic studies highlight the reversible nature of the ortho-metalation reaction. 相似文献