全文获取类型
收费全文 | 469篇 |
免费 | 7篇 |
专业分类
化学 | 279篇 |
晶体学 | 3篇 |
力学 | 40篇 |
数学 | 95篇 |
物理学 | 59篇 |
出版年
2023年 | 5篇 |
2022年 | 11篇 |
2021年 | 10篇 |
2020年 | 12篇 |
2019年 | 3篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 13篇 |
2015年 | 24篇 |
2014年 | 12篇 |
2013年 | 23篇 |
2012年 | 33篇 |
2011年 | 50篇 |
2010年 | 19篇 |
2009年 | 13篇 |
2008年 | 25篇 |
2007年 | 22篇 |
2006年 | 13篇 |
2005年 | 26篇 |
2004年 | 10篇 |
2003年 | 17篇 |
2002年 | 15篇 |
2001年 | 4篇 |
1999年 | 4篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1970年 | 3篇 |
1905年 | 2篇 |
1898年 | 2篇 |
1880年 | 2篇 |
1877年 | 2篇 |
1875年 | 3篇 |
1873年 | 2篇 |
1870年 | 3篇 |
1869年 | 2篇 |
1868年 | 2篇 |
1858年 | 3篇 |
排序方式: 共有476条查询结果,搜索用时 406 毫秒
31.
Being nondestructive and requiring short measurement times, a low amount of material, and no sample preparation, Raman spectroscopy
is used for routine investigation in the study of gemstone inclusions and treatments and for the characterization of mounted
gems. In this work, a review of the use of laboratory Raman and micro-Raman spectrometers and of portable Raman systems in
the gemology field is given, focusing on gem identification and on the evaluation of the composition, provenance, and genesis
of gems. Many examples are shown of the use of Raman spectroscopy as a tool for the identification of imitations, synthetic
gems, and enhancement treatments in natural gemstones. Some recent developments are described, with particular attention being
given to the semiprecious stone jade and to two important organic materials used in jewelry, i.e., pearls and corals. 相似文献
32.
Danilo Sciarrone Luisa Schipilliti Carla Ragonese Peter Quinto Tranchida Paola Dugo Giovanni Dugo Luigi Mondello 《Journal of chromatography. A》2010,1217(7):1101-1105
The present research is focused on the determination of the enantiomeric distribution of chiral compounds, contained in mandarin essential oils, by means of conventional chiral gas chromatography with flame ionization detection (enantio-GC-FID); the results attained were compared with those derived from heart-cutting multidimensional GC-mass spectrometry (MDGC/MS), to evaluate the reliability of the monodimensional technique as a tool for quality control. The Deans-switch MDGC system was equipped with two GC ovens, which were connected via a heated transfer line, a flame ionization detector (FID1) in the first dimension and a quadrupole MS as second-dimension detector. The a priori knowledge of potential co-elutions concerning target compounds (an enantiomer and an interfering compound), when using enantio-GC-FID, could enable the use of corrected enantiomer excess values. Correction factors could be calculated through a preliminary GC-FID analysis (using an apolar column), considering the peak areas of the known interferences. The method used for the calculation of a so-called “coelution correction factor” is described, along with some examples. 相似文献
33.
ángel Ballesteros Alberto Enciso Francisco J. Herranz Orlando Ragnisco Danilo Riglioni 《International Journal of Theoretical Physics》2011,50(7):2268-2277
We consider the classical superintegrable Hamiltonian system given by
_boxclose=+= + ,\mathcal{H}_{\lambda}=\mathcal{T}+\mathcal{U}=\frac{\mathbf{p}^2}{2(1+{\lambda}\mathbf{q}^2)} + \frac{ \omega^2\mathbf{q}^2}{2(1+{\lambda}\mathbf{q}^2)}, 相似文献
34.
Danilo Babusci Giuseppe Dattoli Dario Sacchetti 《Central European Journal of Physics》2011,9(6):1381-1386
The Airy transform is an ideally suited tool to treat problems in classical and quantum optics. Even though the relevant mathematical
aspects have been thoroughly investigated, the possibilities it offers are wide and some features, such as the link with special
functions and polynomials, still contain unexplored aspects. In this note we will show that the so called Airy polynomials
are essentially the third order Hermite polynomials. We will also prove that this identification opens the possibility of
developing new conjectures on the properties of this family of polynomials. 相似文献
35.
In this paper, a family of interpolation neural network operators are introduced. Here, ramp functions as well as sigmoidal functions generated by central B-splines are considered as activation functions. The interpolation properties of these operators are proved, together with a uniform approximation theorem with order, for continuous functions defined on bounded intervals. The relations with the theory of neural networks and with the theory of the generalized sampling operators are discussed. 相似文献
36.
R.J.H. Paynter D.A. Hills D. Dini 《International Journal of Solids and Structures》2010,47(18-19):2613-2619
The edge of a complete contact between elastically similar bodies may often be modelled as a semi-infinite monolithic wedge, because, under a wide range of conditions, the interface is often fully closed and stuck or has small regions of lift and slip at the contact edge. When the local edge separates from the half-plane and slip is inevitable a correction to the Williams solution is required, and this is deduced for the case where the contact-defining body possesses a 90° corner. A simple application of the solution to the example problem of a clamped strip subject to tension is calibrated and the results found used to infer the slip and separation lengths. 相似文献
37.
38.
39.
Danilo šuster 《Acta Analytica》2004,19(33):45-54
Modal arguments for incompatibility of freedom and determinism are typically based on the “transfer principle” for inability
to act otherwise (Beta). The principle of agglomerativity (closure under conjunction introduction) is derivable from Beta.
The most convincing counterexample to Beta is based on the denial of Agglomeration. The defender of the modal argument has
two ways to block counterexamples to Beta: (i) use a notion of inability to act otherwise which is immune to the counterexample
to agglomerativity; (ii) replace Beta with a logically stronger principle Beta 2. I argue that the second strategy fails because
the strengthened principle and Agglomeration together entail Beta. So this strategy makes sense only if Beta 2 is applied
without Agglomeration. But if Beta 2 is used without Agglomeration, then the incompatibilist will undercut the rationale for
the premise of his argument. I illustrate this point with the analysis of Warfield (1996) and his use of Beta 2 in the so
called direct argument for incompatibilism. 相似文献
40.
The equations governing the response of hysteretic systems to sinusoidal forces, which are memory dependent in the classical phase space, can be given as a vector field over a suitable phase space with increased dimension. Hence, the stationary response can be studied with the aids of classical tools of nonlinear dynamics, as for example the Poincaré map. The particular system studied in the paper, based on hysteretic Masing rules, allows the reduction of the dimension of the phase space and the implementation of efficient algorithms. The paper summarises results on one degree of freedom systems and concentrates on a two degree of freedom system as the prototype of many degree of freedom systems. This system has been chosen to be in 1:3 internal resonance situation. Depending on the energy dissipation of the elements restoring force, the response may be more or less complex. The periodic response, described by frequency response curves for various levels of excitation intensity, is highly complex. The coupling produces a strong modification of the response around the first mode resonance, whereas it is negligible around the second mode. Quasi-periodic motion starts bifurcating for sufficiently high values of the excitation intensity; windows of periodic motions are embedded in the dominion of the quasi-periodic motion, as consequence of a locking frequency phenomenon. 相似文献
|