全文获取类型
收费全文 | 258篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 128篇 |
晶体学 | 7篇 |
力学 | 10篇 |
数学 | 25篇 |
物理学 | 94篇 |
出版年
2022年 | 3篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 25篇 |
2012年 | 7篇 |
2011年 | 6篇 |
2010年 | 9篇 |
2009年 | 5篇 |
2008年 | 14篇 |
2007年 | 11篇 |
2006年 | 8篇 |
2005年 | 14篇 |
2004年 | 12篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 9篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 6篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 4篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1968年 | 3篇 |
1967年 | 2篇 |
1966年 | 3篇 |
1937年 | 2篇 |
排序方式: 共有264条查询结果,搜索用时 78 毫秒
51.
C.I. Calle P.J. Mackey M.D. Hogue M.R. Johansen H. Yim P.B. Delaune J.S. Clements 《Journal of Electrostatics》2013,71(3):257-259
Electrodynamic Dust Shields (EDS) have been in development at NASA as a dust mitigation method for lunar and Martian missions. An active dust mitigation strategy, such as that provided by the EDS, that can remove dust from surfaces, is of crucial importance to the planetary exploration program. We report on the development of a flight experiment to fully expose four EDS panels to the space environment. This flight experiment is part of the Materials International Space Station experiment X (MISSE-X), an external platform on the International Space Station that will expose materials to the space environment. 相似文献
52.
The temperature dependence of photoluminescence in Europium tris[3-(trifluoro-methylhydroxymethylene)-(+)-camphorate] (EuTFC) embedded in polymer films has been examined from 40 K down to 4.2 K with the goal of preparing sensor films for low-temperature thermal imaging. The behavior of EuTFC showed significant difference when based on polystyrene compared to poly(n-alkyl methacrylate)s. In poly(n-alkyl methacrylate)s prepared by standard methods for imaging applications, the photoluminescence is fully saturated below 30 K, whereas in polystyrene films there is a strong temperature dependence even down to 4.2 K. By optimizing the preparation procedure for films made of poly(butyl methacrylate) (PBMA) and poly(methyl methacrylate), also these polymers became very sensitive down to liquid helium temperature. The maximum temperature sensitivity of EuTFC in PBMA is found to be 1.0%/K at 4.2 K. The problem of delamination and cracking of the polymer film at cryogenic temperature is also avoided by the special preparation method. 相似文献
53.
Riisager K. Borge M. J. G. Briz J. A. Carmona-Gallardo M. Forstner O. Fraile L. M. Fynbo H. O. U. Camacho A. Garzon Johansen J. G. Jonson B. Lund M. V. Lachner J. Madurga M. Merchel S. Nacher E. Nilsson T. Steier P. Tengblad O. Vedia V. 《The European Physical Journal A - Hadrons and Nuclei》2020,56(3):1-19
The European Physical Journal A - A deterministic treatment of sequential neutron emission, based on recursive equations of the residual temperatures, was applied to numerous fission cases (i.e. 49... 相似文献
54.
Access to the Bis‐benzene Cobalt(I) Sandwich Cation and its Derivatives: Synthons for a “Naked” Cobalt(I) Source? 下载免费PDF全文
Stefan C. Meier Albina Holz Jan Kulenkampff Alexei Schmidt Dr. Daniel Kratzert Dr. Daniel Himmel Dominik Schmitz Dr. Ernst‐Wilhelm Scheidt Prof. Dr. Wolfgang Scherer Dr. Christine Bülow Martin Timm Dr. Rebecka Lindblad Dr. Scott T. Akin Dr. Vicente Zamudio‐Bayer Prof. Dr. Bernd von Issendorff Prof. Dr. Michael A. Duncan Prof. Dr. J. Tobias Lau Prof. Dr. Ingo Krossing 《Angewandte Chemie (International ed. in English)》2018,57(30):9310-9314
The synthesis and structural characterization of the hitherto unknown parent Co(bz)2+ (bz=benzene) complex and several of its derivatives are described. Their synthesis starts either from a CoCO5+ salt, or directly from Co2(CO)8 and a Ag+ salt. Stability and solubility of these complexes was achieved by using the weakly coordinating anions (WCAs) [Al(ORF)4]? and [F{Al(ORF)3}2]? {RF=C(CF3)3} and the solvent ortho‐difluorobenzene (o‐DFB). The magnetic properties of Co(bz)2+ were measured and compared in the condensed and gas phases. The weakly bound Co(o‐dfb)2+ salts are of particular interest for the preparation of further CoI salts, for example, the structurally characterized low‐coordinate 12 valence electron Co(PtBu3)2+ and Co(NHC)2+ salts. 相似文献
55.
A. Anselm A. Johansen E. Leader L. Lukaszuk 《Zeitschrift für Physik A Hadrons and Nuclei》1997,356(4):457-466
The π0 γγ vertex for virtual photons of squared masses q 1 2 and q 2 2 plays a vital rôle in several physical processes; for example for q 1 2 < 0, q 2 2 < 0, in the two-photon physics reaction e + e ? → e + e ?π0, and for q 1 2 > 0, q 2 2 > 0, in the annihilation process e + e ? → π0 l +l?. It is also of interest because of its link to the axial anomaly. We suggest a new approach to this problem. We have obtained a closed analytic expression for the vertex in the limit in which at least one of ¦q 1 2 ¦ and ¦q 2 2 ¦ is large for arbitrary fixed values of the ratio q 1 2 /q 2 2 . We compare our results with those obtained previously by Brodsky and Lepage. It should be straightforward to test our predictions experimentally. 相似文献
56.
A. Johansen D. Sornette 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(1):163-181
The fracture of materials is a catastrophic phenomenon of considerable technological and scientific importance. Here, we analysed
experiments designed for industrial applications in order to test the concept that, in heterogeneous materials such as fiber
composites, rocks, concrete under compression and materials with large distributed residual stresses, rupture is a genuine
critical point, i.e., the culmination of a self-organization of damage and cracking characterized by power law signatures. Specifically, we analyse
the acoustic emissions recorded during the pressurisation of spherical tanks of kevlar or carbon fibers pre-impregnated in
a resin matrix wrapped up around a thin metallic liner (steel or titanium) fabricated and instrumented by Aérospatiale-Matra
Inc. These experiments are performed as part of a routine industrial procedure which tests the quality of the tanks prior
to shipment. We find that the seven acoustic emission recordings of seven pressure tanks which was brought to rupture exhibit
clear acceleration in agreement with a power law “divergence” expected from the critical point theory. In addition, we find
strong evidence of log-periodic corrections that quantify the intermittent succession of accelerating bursts and quiescent
phases of the acoustic emissions on the approach to rupture. An improved model accounting for the cross-over from the non-critical
to the critical region close to the rupture point exhibits interesting predictive potential.
Received 6 July 2000 相似文献
57.
M. E. Gaevskii D. V. Shantsev A. V. Bobyl’ Yu. M. Gal’perin T. H. Johansen H. Hauglin 《Physics of the Solid State》1999,41(6):877-880
The paper provides the first demonstration of the efficiency of applying the magneto-optic method to studies of the spatial
and temporal magnetic-field relaxation in an YBa2Cu3O7 film strip after the transport current is switched on. It is shown that the evolution of magnetic flux distribution is adequately
described in terms of a modified Bean model with time-dependent critical current. At a time 50 ms after the current is switched
on, the critical current of the samples studied decreases by ≈15%. This proves the significance of thermally activated magnetic
flux motion (creep) in the regime investigated. The magnetic vortex pinning energy has been estimated as U
0≈20 kT.
Fiz. Tverd. Tela (St. Petersburg) 41, 965–968 (June 1999) 相似文献
58.
Nur Mahammad Felicity J. Ashcroft Astrid J. Feuerherm Samah Elsaadi Esten N. Vandsemb Magne Brset Berit Johansen 《Molecules (Basel, Switzerland)》2021,26(24)
Cytosolic phospholipase A2α (cPLA2α) is the rate-limiting enzyme in releasing arachidonic acid and biosynthesis of its derivative eicosanoids. Thus, the catalytic activity of cPLA2α plays an important role in cellular metabolism in healthy as well as cancer cells. There is mounting evidence suggesting that cPLA2α is an interesting target for cancer treatment; however, it is unclear which cancers are most relevant for further investigation. Here we report the relative expression of cPLA2α in a variety of cancers and cancer cell lines using publicly available datasets. The profiling of a panel of cancer cell lines representing different tissue origins suggests that hematological malignancies are particularly sensitive to the growth inhibitory effect of cPLA2α inhibition. Several hematological cancers and cancer cell lines overexpressed cPLA2α, including multiple myeloma. Multiple myeloma is an incurable hematological cancer of plasma cells in the bone marrow with an emerging requirement of therapeutic approaches. We show here that two cPLA2α inhibitors AVX420 and AVX002, significantly and dose-dependently reduced the viability of multiple myeloma cells and induced apoptosis in vitro. Our findings implicate cPLA2α activity in the survival of multiple myeloma cells and support further studies into cPLA2α as a potential target for treating hematological cancers, including multiple myeloma. 相似文献
59.
Arne Johansen Randi Midtkandal Heidi Roggen Carl Henrik Grbitz 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(4):o198-o200
The valine side chains in the crystal structure of the title compound [systematic name: 2‐(2‐ammonio‐3‐methylbutanamido)‐3‐hydroxypropanoate trihydrate], C8H16N2O4·3H2O, stack along an a axis of 4.77 Å to form hydrophobic columns surrounded by remarkable water/hydroxyl shells. The peptide main chains are connected by hydrogen bonds in two‐dimensional layers. The peptide molecules in each layer are related only by translation, and generate a very rare pattern. This is rendered possible through the formation of the shortest Cα—H·O(carboxylate) interaction ever recorded. 相似文献
60.
The separation and shock wave formation on the aft-body of a hypersonic adiabatic circular cylinder were studied numerically using the open source software OpenFOAM. The simulations of laminar flow were performed over a range of Reynolds numbers (\(8\times 10^3 < Re < 8\times 10^4\)) at a free-stream Mach number of 5.9. Off-body viscous forces were isolated by controlling the wall boundary condition. It was observed that the off-body viscous forces play a dominant role compared to the boundary layer in displacement of the interaction onset in response to a change in Reynolds number. A modified free-interaction equation and correlation parameter has been presented which accounts for wall curvature effects on the interaction. The free-interaction equation was manipulated to isolate the contribution of the viscous–inviscid interaction to the overall pressure rise and shock formation. Using these equations coupled with high-quality simulation data, the underlying mechanisms resulting in Reynolds number dependence of the lip-shock formation were investigated. A constant value for the interaction parameter representing the part of the pressure rise due to viscous–inviscid interaction has been observed at separation over a wide range of Reynolds numbers. The effect of curvature has been shown to be the primary contributor to the Reynolds number dependence of the free-interaction mechanism at separation. The observations in this work have been discussed here to create a thorough analysis of the Reynolds number-dependent nature of the lip-shock. 相似文献