全文获取类型
收费全文 | 109篇 |
免费 | 1篇 |
专业分类
化学 | 30篇 |
力学 | 3篇 |
数学 | 18篇 |
物理学 | 59篇 |
出版年
2016年 | 1篇 |
2014年 | 1篇 |
2013年 | 36篇 |
2011年 | 3篇 |
2010年 | 3篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2005年 | 2篇 |
2002年 | 2篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1996年 | 10篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1968年 | 2篇 |
1961年 | 1篇 |
1951年 | 1篇 |
1928年 | 1篇 |
排序方式: 共有110条查询结果,搜索用时 15 毫秒
11.
Multireference configuration interaction (MRCI) and complete active space second-order perturbation theory (CASPT2) calculations are performed on Fe2 and Fe? 2. Although it is not possible to definitively identify the ground states of Fe2 and Fe? 2, the calculations suggest that the ground state of Fe? 2 in 8Σ? u derived from 3d134σ2 g4σ2 u and that the states observed in photodetachment are the 9Σ? g and 7Σ? g states with a 3d134σ2 g4σ1 u occupation, but that the ground state of Fe2 is 7Δu(3d144σ2 g) and is not observed in the photo-detachment spectra. 相似文献
12.
Standardized electronic formats for data are needed to efficiently and transparently communicate the results of scientific studies. A format for the unique identification of chemical species is a requirement in the field of chemistry, and the IUPAC International Chemical Identifier (InChI) has been widely adopted for this purpose. The InChI identifier has proved to be very useful. The InChI identifier, however, is currently insufficient to uniquely specify some types of molecular entities at a detailed molecular level needed to fully characterize their chemical nature, to differentiate between chemically distinct conformers, to uniquely identify structures used in quantum chemical calculations, and to completely describe elementary chemical reactions. To address this limitation, we propose an augmented form of InChI, denoted as InChI–ER, which contains additional optional layers that allow the unique and unambiguous identification of molecules at a detailed molecular level. The new layers proposed herein are optional extensions of the existing InChI formalism and, like all other InChI layers, would not interfere with InChI identifiers currently in use. The focus of the present work is the better specification of required molecular entities such as rotational conformations, ring conformations, and electronic states. In companion articles, we propose additional reaction layers using an extended InChI format that will enable the unique identification of elementary chemical reactions, including specification of associated transition states, specification of the changes in bonds that occur during reaction, and classification of reaction types. 相似文献
13.
Charles E. Carraher JR. 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):1237-1261
Prior to 1940 there was little or no education directed toward polymer chemistry. With the contributions of Carothers and others that transformed the practice of polymers into a science-and the leadership of Herman Mark and others in formal graduate and postgraduate education-polymer education took root but rapid expansion and general acceptance by more traditionally oriented academic institutions was slowed by many barriers. Only since 1974 has there been a concerted effort to include education in the basic concepts of polymer chemistry into the undergraduate curriculum. Emphasis is on the development of polymer education in the United States. 相似文献
14.
The fractionation technique described in this paper was used to characterize the melting-point, monomer, and blocking distributions for polymers and copolymers. It is different from the molecular-weight fractionation technique in that the fractions are obtained by using a single solvent to extract the solid polymer below its melting point at stepwise-increasing temperatures. The reproducibility of this technique is excellent, and the technique is sufficient to distinguish pellet-to-pellet variation in a commercially available polypropylene. It was used to show the influence of preparation variables on the melting-point distributions of polyethylene and polypropylene and on the monomer and blocking distribution of copolymers, and to distinguish copolymers from blends. 相似文献
15.
Balle S Tolkachova E San Miguel M Tredicce JR Martín-Regalado J Gahl A 《Optics letters》1999,24(16):1121-1123
We analyze polarization switching in vertical-cavity surface-emitting lasers, taking into account a proper semiconductor frequency-dependent complex susceptibility and spin-flip processes. Thermal effects are included as a varying detuning, and gain differences arise from birefringence splitting. We find that, for large birefringence, gain differences between the two linearly polarized modes are preponderant, and switching occurs owing to thermal shift. For small birefringence polarization switching from the high- to the low-gain mode occurs owing to the combined effect of birefringence and semiconductor phase-amplitude-coupled dynamics for a finite value of the carrier spin-flip rate. 相似文献
16.
S.?Barland X.?Hachair M.?GiudiciEmail author S.?Balle J. R.?Tredicce G.?Tissoni L.?Spinelli L.?Lugiato M.?Brambilla 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,32(1):75-82
We analyze experimentally the spatio-temporal dynamics of the
transverse structures appearing in broad area edge-emitting
semiconductor amplifiers under CW optical injection. We
demonstrate that, in certain conditions, the light reflected by
the system exhibits a multipeaked structure whose dependence on
the parameters suggests an interpretation in terms of
cavity solitons. These structures can exhibit self-pulsations with
periods of the order of few milliseconds, which we explain in
terms of regenerative thermal oscillations. In a particular device,
we generate two single-peak structures which are spatially
uncorrelated, as required for cavity solitons. A microscopic model
shows good agreement with the main body of the experimental
results. 相似文献
17.
Ice nucleating-active Pseudomonas fluorescens F264C was fed to Colorado potato beetles to determine bacterial retentioin in the beetle gut and its effect on the cold hardiness of this insect pest. The bacrterium was present in beetles recovered after overwintering in the field, seven months after their exposure to P. fluorescens. Retention was evident not only in the detection of the P. fluorescens ice nucleating gene, inaW, in bacterial cultures from beetle guts but also in the elevated supercooling points of some treated beetles. 相似文献
18.
Kylstra NJ Worthington RA Patel A Knight PL Vazquez De Aldana JR Roso L 《Physical review letters》2000,85(9):1835-1838
An analysis of the influence of the magnetic field of an intense, high-frequency laser pulse on the stabilization of an atomic system is presented. We demonstrate that at relatively modest intensities the magnetic field can significantly alter the dynamics of the system. In particular, a breakdown of stabilization occurs, thereby restricting the intensity regime in which the atom is relatively stable against ionization. Counterpropagating pulses do not negate the detrimental effects of the magnetic field. We compare our quantum mechanical results with classical Monte Carlo simulations. 相似文献
19.
20.
F. Pedaci M. Giudici J.R. Tredicce G. Giacomelli 《Applied physics. B, Lasers and optics》2005,81(7):993-1000
In this work we experimentally study mode-hopping in bulk semiconductor lasers. This stochastic process is ruled by Kramers
statistics with a decay rate depending on the laser parameters of the temperature of the substrate and the pumping current.
For a general combination of these parameters the average residence times in the two active modes are not equal, resulting
in an asymmetric probability distribution for the modal intensities. We show that, by choosing an appropriate path in the
parameter space, we can vary the residence times of the two modes while holding their ratio constant. Along this path, the
shape of modal intensities distributions are constant up to a scaling factor which is a function of the laser parameters.
Then, the system can be described by a single Langevin equation. The effect of adding noise to the pumping current is also
investigated.
PACS 42.65.Sf; 42.55.Sa; 42.50.-p 相似文献