全文获取类型
收费全文 | 338篇 |
免费 | 4篇 |
专业分类
化学 | 230篇 |
力学 | 3篇 |
数学 | 34篇 |
物理学 | 75篇 |
出版年
2019年 | 5篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 4篇 |
2013年 | 14篇 |
2012年 | 6篇 |
2011年 | 10篇 |
2010年 | 7篇 |
2009年 | 9篇 |
2008年 | 16篇 |
2007年 | 12篇 |
2006年 | 15篇 |
2005年 | 18篇 |
2004年 | 14篇 |
2003年 | 11篇 |
2002年 | 8篇 |
2001年 | 13篇 |
2000年 | 22篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 8篇 |
1995年 | 12篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 14篇 |
1991年 | 15篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1961年 | 1篇 |
1944年 | 1篇 |
排序方式: 共有342条查询结果,搜索用时 0 毫秒
61.
An Fe-0·04 wt.% C alloy was quenched and aged to produce precipitate particles of varying size and spacing. Specimens were fatigued at constant plastic strain over a range of strain amplitudes. In the as-quenched condition the alloy exhibited pronounced cyclic hardening which was attributed to strain ageing. The alloy containing fine carbide particles showed high primary cyclic hardening followed by softening. The softening was associated with the formation of precipitate free channels observed by electron microscopy. When larger, more widely spaced noncoherent particles were present in the lattice, primary cyclic hardening was slight even at high strain amplitudes.This work was sponsored by a grant from the Department of Economics and Trade of the Province of Ontario.Thanks are due to the Department of Energy, Mines and Resources, Ottawa, for assistance in specimen fabrication. 相似文献
62.
A dramatic transition in the mechanical properties of water is observed at the nanometer scale. For a water meniscus formed between two hydrophilic surfaces in the attractive region, with < or = 1 nm interfacial separation, the measured viscosity is 7 orders of magnitude greater than that of bulk water at room temperature. Grand canonical Monte Carlo simulations reveal enhancement in the tetrahedral structure and in the number of hydrogen bonds to the surfaces as a source for the high viscosity; this results from a cooperative effect of hydrogen bonding of water molecules to both hydrophilic surfaces. 相似文献
63.
H. Mkrtchyan P.E. Bosted G.S. Adams A. Ahmidouch T. Angelescu J. Arrington R. Asaturyan O.K. Baker N. Benmouna C. Bertoncini H.P. Blok W.U. Boeglin H. Breuer M.E. Christy S.H. Connell Y. Cui M.M. Dalton S. Danagoulian D. Day T. Dodario J.A. Dunne D. Dutta N. El Khayari R. Ent H.C. Fenker V.V. Frolov L. Gan D. Gaskell K. Hafidi W. Hinton R.J. Holt T. Horn G.M. Huber E. Hungerford X. Jiang M. Jones K. Joo N. Kalantarians J.J. Kelly C.E. Keppel V. Kubarovsky Y. Li Y. Liang S. Malace P. Markowitz E. McGrath P. McKee D.G. Meekins B. Moziak T. Navasardyan 《Physics letters. [Part B]》2008
64.
65.
66.
J. D. Baker C. A. McGrath T. S. Hill R. Reifarth F. Tovesson 《Journal of Radioanalytical and Nuclear Chemistry》2008,276(2):555-560
The Advanced Fuel Cycle Initiative (AFCI) and the Generation IV Reactor Initiative have demonstrated a lack of detailed neutron
cross sections for certain “minor” actinides. For some closed-fuel-cycle reactor designs more than 50% of reactivity will,
at some point, be derived from “minor” actinides that currently have poorly known or in some cases not measured (n,γ) and
(n,f) cross sections. Using a combination of resurrected techniques and new developments, we have made a series of targets
including highly enriched 239Pu, 240Pu, and 242Pu. Thus far, we have electrodeposited these actinide targets. The chemical purification and electodeposition techniques will
be described. 相似文献
67.
Feng Wang Michael Hickner Qing Ji William Harrison Jeffrey Mecham Thomas A. Zawodzinski James E. McGrath 《Macromolecular Symposia》2001,175(1):387-396
Novel biphenol‐based wholly aromatic poly (arylene ether sulfones) containing pendant sulfonate groups were prepared by direct aromatic nucleophilic substitution polycondensation of disodium 3,3′‐disulfonate‐4,4′‐dichlorodiphenyl sulfone (SDCDPS), 4,4′‐dichlorodiphenylsulfone (DCDPS) and biphenol. Copolymerization proceeded quantitatively to high molecular weight in N‐methyl‐2‐pyrrolidinone at 190°C in the presence of anhydrous potassium carbonate. Tough membranes were successfully cast from the control and the copolymers, which had a SDCDPS/DCDPS mole ratio of either 40:60 or 60:40 using N,N‐dimethylactamide; the 100% SDCDPS homopolymer was water soluble. Short‐term aging (30 min) indicates that the desired acid form membranes are stable to 220°C in air and conductivity values at 25°C of 0.110 (40%) and 0.170 S/cm (60%) were measured, which are comparable to or higher than the state‐of‐the art fluorinated copolymer Nafion 1135 control. The new copolymers, which contain ion conductivity sites on deactivated rings, are candidates as new polymeric electrolyte materials for proton exchange membrane (PEM) fuel cells. Further research comparing their membrane behavior to post‐sulfonated systems is in progress. 相似文献
68.
J. C. Abed R. Mercier J. E. McGrath 《Journal of polymer science. Part A, Polymer chemistry》1997,35(6):977-987
Several aromatic dicyanate monomers have been synthesized bearing para-linked strong electron withdrawing groups, such as phenylphosphine oxide, sulfone, and carbonyl. These groups increased the reactivity of the cyanate functional groups and eliminated the need for curing catalysts. However, an undesirable decrease in the processing window between the monomer melting point and the onset of cure was also generally observed. An arylene ether phenyl phosphine oxide system was designed that displayed several attractive characteristics such as a low softening point, a wide processing window, cure with no catalyst, high Tg and high char yield in air, suggesting that these new thermosets might show good fire resistance. The dicyanate ester monomers were synthesized in high yield by reacting various bisphenols with cyanogen bromide in the presence of triethylamine. The high reactivity of the cyanate functional groups required that the cyanation reaction be conducted at temperature below 0°C in order to prevent imidocarbonate side reactions. Proton NMR and FT-IR were used to characterize these monomers. The cyclotrimerization curing process was monitored by the disappearance of the carbon-nitrogen triple bond stretch (2270 cm−1). An optimal cure schedule was determined and the cured polycyanurate networks were characterized by DSC, DMTA, and TGA. Tg values were typically > 250°C and 5% weight loss values were observed by TGA in air above 400°C. Several of the dicyanate monomers with sufficiently large processing windows were cured into single lap shear adhesive bonds onto titanium 6/4 and the measurements are reported herein. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 977–987, 1997 相似文献
69.
70.