全文获取类型
收费全文 | 560篇 |
免费 | 1篇 |
国内免费 | 2篇 |
专业分类
化学 | 296篇 |
晶体学 | 7篇 |
力学 | 15篇 |
数学 | 34篇 |
物理学 | 211篇 |
出版年
2020年 | 3篇 |
2018年 | 4篇 |
2014年 | 5篇 |
2013年 | 27篇 |
2012年 | 9篇 |
2011年 | 17篇 |
2010年 | 14篇 |
2009年 | 9篇 |
2008年 | 20篇 |
2007年 | 19篇 |
2006年 | 17篇 |
2005年 | 21篇 |
2004年 | 25篇 |
2003年 | 10篇 |
2002年 | 12篇 |
2001年 | 15篇 |
2000年 | 12篇 |
1999年 | 14篇 |
1998年 | 13篇 |
1997年 | 3篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 11篇 |
1993年 | 11篇 |
1992年 | 13篇 |
1991年 | 11篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 28篇 |
1984年 | 15篇 |
1983年 | 7篇 |
1982年 | 11篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1976年 | 10篇 |
1975年 | 13篇 |
1974年 | 11篇 |
1973年 | 9篇 |
1972年 | 7篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1968年 | 3篇 |
1937年 | 3篇 |
排序方式: 共有563条查询结果,搜索用时 468 毫秒
51.
Avgoustidis A Copeland EJ Moss A Pogosian L Pourtsidou A Steer DA 《Physical review letters》2011,107(12):121301
We study signatures of cosmic superstring networks containing strings of multiple tensions and Y junctions, on the cosmic microwave background (CMB) temperature and polarization spectra. Focusing on the crucial role of the string coupling constant g(s), we show that the number density and energy density of the scaling network are dominated by different types of string in the g(s) ~ 1 and g(s) ? 1 limits. This can lead to an observable shift in the position of the B-mode peak--a distinct signal leading to a direct constraint on g(s). We forecast the joint bounds on g(s) and the fundamental string tension μ(F) from upcoming and future CMB polarization experiments, as well as the signal to noise in detecting the difference between B-mode signals in the limiting cases of large and small g(s). We show that such a detectable shift is within reach of planned experiments. 相似文献
52.
D. Pudo B. Corcoran C. Monat M. Pelusi D.J. Moss B.J. Eggleton T.P. White L. O’Faolain T.F. Krauss 《Photonics and Nanostructures》2010,8(2):67-71
We demonstrate bit error rate improvement, corroborated by eye diagram measurements, of a (10 MHz) amplitude distorted 10 Gbit/s data signal in silicon photonic crystal waveguides. This demonstration exploits a power clamping nonlinear transfer function, provided by slow light enhancement of nonlinear absorption in these waveguides. 相似文献
53.
A. D. Fitt D. P. Mason E. A. Moss 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2007,58(6):1049-1067
The propagation of a two-dimensional fluid-driven fracture in impermeable rock is considered. The fluid flow in the fracture
is laminar. By applying lubrication theory a partial differential equation relating the half-width of the fracture to the
fluid pressure is derived. To close the model the PKN formulation is adopted in which the fluid pressure is proportional to
the half-width of the fracture. By considering a linear combination of the Lie point symmetries of the resulting non-linear
diffusion equation the boundary value problem is expressed in a form appropriate for a similarity solution. The boundary value
problem is reformulated as two initial value problems which are readily solved numerically. The similarity solution describes
a preexisting fracture since both the total volume and length of the fracture are initially finite and non-zero. Applications
in which the rate of fluid injection into the fracture and the pressure at the fracture entry are independent of time are
considered. 相似文献
54.
A. D. Fitt D. P. Mason E. A. Moss 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2007,81(2):1049-1067
The propagation of a two-dimensional fluid-driven fracture in impermeable rock is considered. The fluid flow in the fracture
is laminar. By applying lubrication theory a partial differential equation relating the half-width of the fracture to the
fluid pressure is derived. To close the model the PKN formulation is adopted in which the fluid pressure is proportional to
the half-width of the fracture. By considering a linear combination of the Lie point symmetries of the resulting non-linear
diffusion equation the boundary value problem is expressed in a form appropriate for a similarity solution. The boundary value
problem is reformulated as two initial value problems which are readily solved numerically. The similarity solution describes
a preexisting fracture since both the total volume and length of the fracture are initially finite and non-zero. Applications
in which the rate of fluid injection into the fracture and the pressure at the fracture entry are independent of time are
considered. 相似文献
55.
Background
Stargazin (γ2) and the closely related γ3, and γ4 transmembrane proteins are part of a family of proteins that may act as both neuronal voltage-dependent calcium channel (VDCC) γ subunits and transmembrane α-amino-3-hydroxy-5-methyl-4-isoxazoleproponinc (AMPA) receptor regulatory proteins (TARPs). In this investigation, we examined the distribution patterns of the stargazin-like proteins γ2, γ3, and γ4 in the human central nervous system (CNS). In addition, we investigated whether human γ2 or γ4 could modulate the electrophysiological properties of a neuronal VDCC complex transiently expressed in Xenopus oocytes. 相似文献56.
It has been established experimentally that both natural gas and hydrogen discharges, through circular orifices larger than a critical diameter, sustain stable lifted flames irrespective of the reservoir pressure driving the release. At smaller diameters, however, stable burning will only be achieved at operating pressures higher than a particular, diameter-dependent, threshold. This latter is strongly fuel-type dependent but empirical correlations have been developed to describe such behaviour. Given the wide disparity of critical diameters depending upon the fuel type considered, the behaviour of multi-component gaseous mixtures involving hydrogen is much less predictable than the correlations for pure fuels might indicate. A series of experiments has been undertaken in which H2-CO mixtures are discharged from a high pressure reservoir to ambient through convergent circular nozzles, varying in diameter from 1.3 to 5 mm. A wide range of driving pressures has been investigated, from 3 to 50 bar, embracing fuel mixtures containing up to 20% CO by volume. Stability curves have been derived that identify the region where stable burning is sustained relative to the pressure ratio (reservoir pressure/ambient pressure) and the CO concentration in the fuel mixture. The present experimental data are compared with existing correlations (Kalghatgi 1981), derived from subsonic releases, and Birch et al. (1988a), applied to underexpanded supersonic methane jet flames. Although these correlations reproduce the general trend observed experimentally, they appear to significantly over-estimate the stability region. Furthermore, they do not account for the high sensitivity of the diluent concentration on the blowout stability. A thorough investigation is carried out in order to determine the source of discrepancies observed between the empirical correlations and the present measurements. Differential diffusion between the fuel components is shown to be negligible. The introduction of additional information on the turbulent flowfield from numerical simulation of the isothermal underexpanded jet, immediately upstream of the flame stabilisation region, does not appear to yield discriminating evidence for incipient blow-off instability. The maximum burning velocity alone, a widely employed characterising parameter, does not appear to describe accurately the complex interactions between the turbulent flowfield and the chemical kinetics. 相似文献
57.
E. A. Moss 《Experiments in fluids》1989,7(4):271-274
A study was undertaken to investigate transition in a pipe flow accelerated from rest. Experiments were carried out on a vertical tube under a constant head of liquid: flow was initiated by opening a solenoid valve. A wall shear stress probe used in the role of an event recorder identified two transition events, separated by the passage of a turbulent to laminar front and a period of laminar flow. Evidence suggests that the first comprises a laminar to turbulent interface arising from a natural stable/unstable front moving up the tube as local conditions become met, while the second is consequent upon the formation of a continuous turbulent structure carried down the tube from the inlet by the bulk flow. The paper provides a formal explanation of a phenomenon which is typical of that which is observed in starting pipe flows with a disturbed inlet. 相似文献
58.
Mokgolela M. Mogorosi John R. Moss Selwyn F. Mapolie Koop Lammertsma 《Journal of organometallic chemistry》2011,696(23):3585-3592
New N-functionalised 2-phosphinobenzaldimino (P^N) ligands bearing 3-picolyl, furfuryl, thiophene-2-methyl, thiophene-2-ethyl, and benzyl groups have been prepared in good yield. The 2-phosphinobenzaldimino ligands were reacted with PdCl2(COD) to give the corresponding metal complexes of the type Pd(L)Cl2 (L = 2-phosphinobenzaldimino (P^N) ligand). All compounds were fully characterized using spectroscopic and analytical techniques, including 1H, 13C, and 31P NMR and IR spectroscopies, mass spectrometry and elemental analysis. Selected neutral palladium complexes were evaluated as catalyst precursors in ethylene oligomerisation reactions, after activation with a co-catalyst (MMAO, EtAlCl2, or Et2AlCl). 相似文献
59.
Moss CL Chung TW Wyer JA Nielsen SB Hvelplund P Tureček F 《Journal of the American Society for Mass Spectrometry》2011,22(4):731-751
Electron transfer and capture mass spectra of a series of doubly charged ions that were phosphorylated pentapeptides of a
tryptic type (pS,A,A,A,R) showed conspicuous differences in dissociations of charge-reduced ions. Electron transfer from both
gaseous cesium atoms at 100 keV kinetic energies and fluoranthene anion radicals in an ion trap resulted in the loss of a
hydrogen atom, ammonia, and backbone cleavages forming complete series of sequence z ions. Elimination of phosphoric acid was negligible. In contrast, capture of low-energy electrons by doubly charged ions
in a Penning ion trap induced loss of a hydrogen atom followed by elimination of phosphoric acid as the dominant dissociation
channel. Backbone dissociations of charge-reduced ions also occurred but were accompanied by extensive fragmentation of the
primary products. z-Ions that were terminated with a deaminated phosphoserine radical competitively eliminated phosphoric acid and H2PO4 radicals. A mechanism is proposed for this novel dissociation on the basis of a computational analysis of reaction pathways
and transition states. Electronic structure theory calculations in combination with extensive molecular dynamics mapping of
the potential energy surface provided structures for the precursor phosphopeptide dications. Electron attachment produces
a multitude of low lying electronic states in charge-reduced ions that determine their reactivity in backbone dissociations
and H- atom loss. The predominant loss of H atoms in ECD is explained by a distortion of the Rydberg orbital space by the
strong dipolar field of the peptide dication framework. The dipolar field steers the incoming electron to preferentially attach
to the positively charged arginine side chain to form guanidinium radicals and trigger their dissociations. 相似文献
60.
Feng Zheng Akella Sivaramakrishna John R. Moss 《Journal of organometallic chemistry》2011,696(11-12):2457-2465
Thermal decomposition studies on platinacycloalkanes of the type Pt(CH2)mL2 (where m = 6,7,8,10 and L2 = dppp {1,3-bis(diphenylphosphino)propane}, dppe {1,2-bis(diphenylphosphino)ethane} or L = PPh3, tBu3P) are described. The results reveal that the organic product distribution depends on various factors such as the nature of ligand, the metal system, the mode of decomposition, the ring size and the temperature. Possible mechanistic pathways for the formation of various products are discussed. These platinacycloalkanes can be used as models for metallacycloalkane intermediates in catalytic reactions. 相似文献