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11.
Dmitri Vassiliev 《General Relativity and Gravitation》2002,34(8):1239-1265
In abstract Yang–Mills theory the standard instanton construction relies on the Hodge star having real eigenvalues which makes it inapplicable in the Lorentzian case. We show that for the affine connection an instanton-type construction can be carried out in the Lorentzian setting. The Lorentzian analogue of an instanton is a spacetime whose connection is metric compatible and Riemann curvature irreducible (pseudoinstanton). We suggest a metric-affine action which is a natural generalization of the Yang–Mills action and for which pseudoinstantons are stationary points. We show that a spacetime with a Ricci flat Levi-Civita connection is a pseudoinstanton, so the vacuum Einstein equation is a special case of our theory. We also find another pseudoinstanton which is a wave of torsion in Minkowski space. Analysis of the latter solution indicates the possibility of using it as a model for the neutrino. 相似文献
12.
13.
We use a two-channel contact interaction model to describe a system of three identical bosons. The two-channel model quantitatively describes the phenomena of Feshbach resonance in agreement with the phenomenological expression relating scattering length to magnetic detuning. The model also has a finite effective range. We investigate finite range effects in three-body recombination. The simpler one-channel contact interaction model predicts a characteristic geometric scaling of minima in the recombination coefficient as a function of scattering length with scaling parameter 22.7. We show that this factor is reduced when the effective range is included. We compare calculations to experiment. 相似文献
14.
We evaluate the current distribution for a single-electron transistor with intermediate strength tunnel conductance. Using the Schwinger-Keldysh approach and the drone (Majorana) fermion representation, we account for the renormalization of system parameters. Nonequilibrium effects induce a lifetime broadening of the charge-state levels, which suppress large current fluctuations. 相似文献
15.
Anomalous absorption of bulk shear sagittal acoustic waves in a layered structure with viscous fluid
It is demonstrated theoretically that the absorptivity of bulk shear sagittal waves by an ultra-thin layer of viscous fluid between two different elastic media has a strong maximum (in some cases as good as 100%) at an optimal layer thickness. This thickness is usually much smaller than the penetration depths and lengths of transverse and longitudinal waves in the fluid. The angular dependencies of the absorptivity are demonstrated to have significant and unusual structure near critical angles of incidence. The effect of non-Newtonian properties and non-uniformities of the fluid layer on the absorptivity is also investigated. In particular, it is shown that the absorption in a thin layer of viscous fluid is much more sensitive to non-zero relaxation time(s) in the fluid layer than the absorption at an isolated solid-fluid interface. 相似文献
16.
We report a comparison of electric-field gradients (EFGs) measured at the group-III sites on epitaxially-grown surfaces of
2×2-reconstructed GaAs and InAs crystals. For this purpose, we used 111In→111Cd perturbed-angular-correlation (PAC) spectroscopy. Sharp spectral lines characterize the perturbation functions corresponding
to both surfaces. On GaAs surface, we observe only one well-defined nuclear electric-quadrupole interaction (NQI); and on
the InAs surface, we observe a primary and a secondary NQI. Very similar but experimentally-distinguishable values of the
EFG-parameters characterize the primary interactions corresponding to the GaAs and InAs surfaces. Specifically, for the GaAs
and InAs surfaces, ω
Q
=28.0±0.2 Mrad s−1 and η=0.43±0.02 and ω
Q
=28.8±0.2 Mrad s−1 and η=0.39±0.02, and the angles between EFG z-axis and the (111) direction are 65°±3° and β=53°±3°, respectively. These unexpected results indicate that the so-called
lattice contribution to the EFG is not significant. Moreover, for the primary NQIs on both surfaces, the similar parameter
values demonstrate that chemical differences between the 111In probe and the indigenous Ga surface atoms cause no large quantitative effects. This information indicates that impurity
probes and PAC spectroscopy can be used effectively to investigate III–V surfaces.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
17.
Pumera M Smíd B Peng X Golberg D Tang J Ichinose I 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(27):7644-7649
A novel protocol for precisely coating individual multiwall carbon nanotubes (MWCNTs) with an ultrathin layer of polypyrrole was developed. The nanocoated MWCNTs were successfully prepared by in situ chemical deposition of polypyrrole in an aqueous suspension of MWCNTs. The coating layer was very uniform and the thickness of the layer was determined by controlling the monomer concentration used, which gave nanometer precision. The products were characterized by transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, electron energy loss spectroscopy, and conductivity and current-voltage measurements. The ultrathin polypyrrole layer could electrically insulate individual MWCNTs. 相似文献
18.
Dianionic Titanyl and Vanadyl (Cation+)2[MIVO(Pc4−)]2− Phthalocyanine Salts Containing Pc4− Macrocycles 下载免费PDF全文
Dr. Dmitri V. Konarev Dr. Alexey V. Kuzmin Dr. Salavat S. Khasanov Alexey L. Litvinov Dr. Akihiro Otsuka Prof. Hideki Yamochi Prof. Hiroshi Kitagawa Prof. Rimma N. Lyubovskaya 《化学:亚洲杂志》2018,13(12):1552-1560
In this study, the titanyl and vanadyl phthalocyanine (Pc) salts (Bu4N+)2[MIVO(Pc4?)]2? (M=Ti, V) and (Bu3MeP+)2[MIVO(Pc4?)]2? (M=Ti, V) with [MIVO(Pc4?)]2? dianions were synthesized and characterized. Reduction of MIVO(Pc2?) carried out with an excess of sodium fluorenone ketyl in the presence of Bu4N+ or Bu3MeP+ is exclusive to the phthalocyanine centers, forming Pc4? species. During reduction, the metal +4 charge did not change, implying that Pc is an non‐innocent ligand. The Pc negative charge increase caused the C?N(pyr) bonds to elongate and the C?N(imine) bonds to alternate, thus increasing the distortion of Pc. Jahn–Teller effects are significant in the [eg(π*)]2 dianion ground state and can additionally distort the Pc macrocycles. Blueshifts of the Soret and Q‐bands were observed in the UV/Vis/NIR when MIVO(Pc2?) was reduced to [MIVO(Pc . 3?)] . ? and [MIVO(Pc4?)]2?. From magnetic measurements, [TiIVO(Pc4?)]2? was found to be diamagnetic and (Bu4N+)2[VIVO(Pc4?)]2? and (Bu3MeP+)2[VIVO(Pc4?)]2? were found to have magnetic moments of 1.72–1.78 μB corresponding to an S=1/2 spin state owing to VIV electron spin. As a result, two latter salts show EPR signals with VIV hyperfine coupling. 相似文献
19.
Dzmitry Padhorny David R. Hall Hanieh Mirzaei Artem B. Mamonov Mohammad Moghadasi Andrey Alekseenko Dmitri Beglov Dima Kozakov 《Journal of computer-aided molecular design》2018,32(1):225-230
Fast Fourier transform (FFT) based approaches have been successful in application to modeling of relatively rigid protein–protein complexes. Recently, we have been able to adapt the FFT methodology to treatment of flexible protein–peptide interactions. Here, we report our latest attempt to expand the capabilities of the FFT approach to treatment of flexible protein–ligand interactions in application to the D3R PL-2016-1 challenge. Based on the D3R assessment, our FFT approach in conjunction with Monte Carlo minimization off-grid refinement was among the top performing methods in the challenge. The potential advantage of our method is its ability to globally sample the protein–ligand interaction landscape, which will be explored in further applications. 相似文献
20.
A General Approach Towards Triazole‐Linked Adenosine Diphosphate Ribosylated Peptides and Proteins 下载免费PDF全文
Qiang Liu Dr. Hans A. V. Kistemaker Dr. Sagar Bhogaraju Prof. Dr. Ivan Dikic Prof. Dr. Herman S. Overkleeft Prof. Dr. Gijsbert A. van der Marel Prof. Dr. Huib Ovaa Dr. Gerbrand J. van der Heden van Noort Dr. Dmitri V. Filippov 《Angewandte Chemie (International ed. in English)》2018,57(6):1659-1662
Current methods to prepare adenosine diphosphate ribosylated (ADPr) peptides are not generally applicable due to the labile nature of this post‐translational modification and its incompatibility with strong acidic conditions used in standard solid‐phase peptide synthesis. A general strategy is presented to prepare ADPr peptide analogues based on a copper‐catalyzed click reaction between an azide‐modified peptide and an alkyne‐modified ADPr counterpart. The scope of this approach was expanded to proteins by preparing two ubiquitin ADPr analogues carrying the biological relevant α‐glycosidic linkage. Biochemical validation using Legionella effector enzyme SdeA shows that clicked ubiquitin ADPr is well‐tolerated and highlights the potential of this strategy to prepare ADPr proteins. 相似文献