全文获取类型
收费全文 | 450篇 |
免费 | 105篇 |
国内免费 | 65篇 |
专业分类
化学 | 43篇 |
晶体学 | 5篇 |
力学 | 21篇 |
综合类 | 5篇 |
数学 | 34篇 |
物理学 | 512篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 13篇 |
2019年 | 10篇 |
2018年 | 11篇 |
2017年 | 16篇 |
2016年 | 19篇 |
2015年 | 11篇 |
2014年 | 19篇 |
2013年 | 37篇 |
2012年 | 29篇 |
2011年 | 30篇 |
2010年 | 40篇 |
2009年 | 34篇 |
2008年 | 32篇 |
2007年 | 45篇 |
2006年 | 29篇 |
2005年 | 31篇 |
2004年 | 28篇 |
2003年 | 18篇 |
2002年 | 27篇 |
2001年 | 12篇 |
2000年 | 17篇 |
1999年 | 11篇 |
1998年 | 11篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
排序方式: 共有620条查询结果,搜索用时 15 毫秒
131.
132.
133.
134.
J. R. Forshaw 《Pramana》2004,63(6):1119-1134
In this talk I discuss a few selected topics in Higgs phenomenology at the LHC. After some brief remarks on the standard model
Higgs I turn to more novel possibilities, discussing a heavy Higgs scenario, a light Higgs scenario and a no Higgs scenario.
In the case of the light Higgs, I discuss briefly the physics opportunities afforded if it becomes possible to detect low
angle scattered protons at the LHC. 相似文献
135.
J. J. Gonzalez A. Gleizes S. Vacquié P. Brunelot 《Plasma Chemistry and Plasma Processing》1993,13(2):237-271
A physical model of two zones (constricted arc and cathode jet) of a 1-MW transferred arc in air is presented. It is based on the solution al conservation equations by a finite-differenee method. Turbulence is treated with Prandtl's approximation, whereas radiative transfer is solved considering a nonhontogeneous medium, with the hypothesis of gray spectral bands. The in of radiative transfer on the temperature field is illustrated using two-band and four-band radiation models. We also show the influence of several parameters on plasma jet properties: current intensity between 500 and 1500 A; gas mass /low rate between 10 and 90g/s, vortex injection. The arc characteristics are analyzed in accordance with physical mechanisms such as heat conduction, radiation, turbulence, convection, and miring of cold gas. 相似文献
136.
Electronic structures and photophysical properties of phosphorescent platinum (II) complexes with tridentate C^N*N cyclometalated ligands
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
To get an insight into the structure–property relationships in a series of strongly phosphorescent platinum(II) complexes with tridentate C^N*N cyclometalated ligands, their electronic structures and electroluminescence properties were systematically investigated via density functional theory and time‐dependent density functional theory. Moreover, the factors related to the radiative and non‐radiative decay process, including the transition electric dipole moment μ(Sn), the energy difference between singlet and lowest triplet excited states ΔE(Sn–T1) and the spin–orbital coupling matrix elements , as well as the energy gap between T1 and S0 states ΔE(T1–S0) and absorption–emission Stokes shifts have been calculated. Fine emission color tuning and high phosphorescence quantum yield of phosphorescent complexes may be achieved through introducing five–six‐membered metallacycle geometries and linking a substituent (such as phenyl) at bridge atoms. Additionally, phosphorescent properties of these complexes show a clear dependence on the electronegativity of bridge atoms. 相似文献
137.
Ion activation methods for tandem mass spectrometry 总被引:7,自引:0,他引:7
This tutorial presents the most common ion activation techniques employed in tandem mass spectrometry. In-source fragmentation and metastable ion decompositions, as well as the general theory of unimolecular dissociations of ions, are initially discussed. This is followed by tandem mass spectrometry, which implies that the activation of ions is distinct from the ionization step, and that the precursor and product ions are both characterized independently by their mass/charge ratios. In collision-induced dissociation (CID), activation of the selected ions occurs by collision(s) with neutral gas molecules in a collision cell. This experiment can be done at high (keV) collision energies, using tandem sector and time-of-flight instruments, or at low (eV range) energies, in tandem quadrupole and ion trapping instruments. It can be performed using either single or multiple collisions with a selected gas and each of these factors influences the distribution of internal energy that the activated ion will possess. While CID remains the most common ion activation technique employed in analytical laboratories today, several new methods have become increasingly useful for specific applications. More recent techniques are examined and their differences, advantages and disadvantages are described in comparison with CID. Collisional activation upon impact of precursor ions on solid surfaces, surface-induced dissociation (SID), is gaining importance as an alternative to gas targets and has been implemented in several different types of mass spectrometers. Furthermore, unique fragmentation mechanisms of multiply-charged species can be studied by electron-capture dissociation (ECD). The ECD technique has been recognized as an efficient means to study non-covalent interactions and to gain sequence information in proteomics applications. Trapping instruments, such as quadrupole ion traps and Fourier transform ion cyclotron resonance instruments, are particularly useful for the photoactivation of ions, specifically for fragmentation of precursor ions by infrared multiphoton dissociation (IRMPD). IRMPD is a non-selective activation method and usually yields rich fragmentation spectra. Lastly, blackbody infrared radiative dissociation is presented with a focus on determining activation energies and other important parameters for the characterization of fragmentation pathways. The individual methods are presented so as to facilitate the understanding of each mechanism of activation and their particular advantages and representative applications. 相似文献
138.
Radiative lifetimes and total deactivation cross sections of K(72S) and K(52D) by collision with NO are studied. The K atomic vapor in either the 72S or the 52D state was prepared by two- photon absorption using a dye laser. The decay signal of the time-resolved fluorescence from the 72S – 42P1/2 or 52D – 42P3/2 transition was then monitored. Based on a Stern-Volmer analysis, the radiative lifetimes are 155 ±8 ns and 561 ± 18 ns for the K(72S) and K(52D) states, respectively. The total deactivation cross sections are 88 ±1Å2 and 70 ±2Å2 for the K(72S)-NO and K(52D)-NO collisions, respectively. In the absence of NO collisions the radiative lifetimes obtained in this work show excellent agreement with those previously reported. The quenching cross sections for NO have been measured for the first time, and have values in a reasonable range, when compared with Na-N2 collisions. 相似文献
139.
Photoionization (PI) cross sections (PICS) are necessary for the simulation of astrophysical and ICF plasmas. In order to be used in plasma modeling, the PICS are usually fit to simple analytical formulas. We observed an unusual spectral shape of the PICS of the 4d shell of ionized Xe and other elements, computed with different codes: a local minimum occurs around twice the threshold energy. We explain this phenomenon as interference between the bound 4d wavefunction and the free electron wavefunction, which is similar to the Cooper minima for neutral atoms. Consequently, the usual fitting formulas, which consist of a combination of inverse powers of the frequency beyond threshold, may yield rates for PI and radiative recombination (RR) that are incorrect by orders of magnitude. A new fitting algorithm is proposed and is included in the latest version of HULLAC.v9.5. 相似文献
140.
In this paper, we shall establish the global existence and exponential stability of solutions in Hi(i = 1,2,4) for a Stefan‐Boltzmann model of a viscous, reactive, and radiative gas with the first‐order Arrhenius kinetics in a bounded interval. 相似文献