全文获取类型
收费全文 | 3972篇 |
免费 | 98篇 |
国内免费 | 16篇 |
专业分类
化学 | 2473篇 |
晶体学 | 16篇 |
力学 | 274篇 |
数学 | 824篇 |
物理学 | 499篇 |
出版年
2023年 | 19篇 |
2022年 | 78篇 |
2021年 | 101篇 |
2020年 | 83篇 |
2019年 | 72篇 |
2018年 | 56篇 |
2017年 | 46篇 |
2016年 | 121篇 |
2015年 | 112篇 |
2014年 | 110篇 |
2013年 | 201篇 |
2012年 | 222篇 |
2011年 | 240篇 |
2010年 | 168篇 |
2009年 | 146篇 |
2008年 | 201篇 |
2007年 | 209篇 |
2006年 | 200篇 |
2005年 | 179篇 |
2004年 | 160篇 |
2003年 | 111篇 |
2002年 | 140篇 |
2001年 | 39篇 |
2000年 | 45篇 |
1999年 | 42篇 |
1998年 | 32篇 |
1997年 | 41篇 |
1996年 | 47篇 |
1995年 | 35篇 |
1994年 | 32篇 |
1993年 | 42篇 |
1992年 | 46篇 |
1991年 | 31篇 |
1990年 | 14篇 |
1989年 | 21篇 |
1988年 | 21篇 |
1987年 | 33篇 |
1986年 | 15篇 |
1985年 | 33篇 |
1984年 | 36篇 |
1983年 | 38篇 |
1982年 | 33篇 |
1981年 | 47篇 |
1980年 | 47篇 |
1979年 | 41篇 |
1978年 | 26篇 |
1977年 | 29篇 |
1976年 | 23篇 |
1975年 | 19篇 |
1967年 | 13篇 |
排序方式: 共有4086条查询结果,搜索用时 15 毫秒
1.
We report studies on the structure of the metallic core and the alkyl cap layer in monolayer protected gold nanoparticles having sizes down to 1.6 nm. These particles are obtained by laser ablating gold targets in alkane-thiol solutions at different concentrations. The electronic structure of gold core and the vibrational properties of the capping hydrocarbon chains reveal effects connected with the nanosized nature of the particles. 相似文献
2.
We apply here the harmonic and Cartan decomposition techniques to piezoelectric material symmetries classification. We show in particular that we shall reduce from 19 to 17 the number of symmetry classes corresponding to the piezoelectric phenomenon. To cite this article: G. Geymonat, T. Weller, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 847–852. 相似文献
3.
Nicolò Giovannelli Giuseppe Rao Calogero Vetro 《Rendiconti del Circolo Matematico di Palermo》2005,54(3):443-450
In this paper we consider a definition of essentialK-variation for real functions which gives information on the absolute integrability of its approximate derivate on a measurable
set. 相似文献
4.
Vincenzo Santagada Ferdinando FiorinoElisa Perissutti Beatrice SeverinoSara Terracciano Giuseppe CirinoGiuseppe Caliendo 《Tetrahedron letters》2003,44(6):1145-1148
A novel and convenient microwave-assisted dimerization of an active peptide compound using the DKPs as scaffold is described. The key reaction giving rise to the diketopiperazine scaffold is the intermolecular coupling. No epimerization was detected in the reactions used. Conventional and microwave heating of the reactions are compared. Synthesis by microwave irradiation gave the desired compounds in higher yields and in shorter reaction times than those obtained by conventional heating. 相似文献
5.
Giuseppe Coppola Andrea Irace Giovanni Breglio Mario Iodice Luigi Zeni Antonello Cutolo Pasqualina M. Sarro 《Optics and Lasers in Engineering》2003,39(3):317-332
In this paper we describe two different kind of optoelectronic devices both based on a three terminals active device and exploit the plasma dispersion effect to achieve the desired working. The first device exploits this effect in order to obtain an optical modulation. The second device is an optoelectronic router based on the mode-mixing principle together with the injection-induced optical phase shift. Both devices are integrated into a Silicon on Silicon optical channel waveguide which can be realized using a standard bipolar process. The possibility of using standard, well-known technology presents several advantages with respect to III–V Optoelectronics. The active three terminal device used is a Bipolar Mode Field Effect Transistor (BMFET). Numerical simulation results are presented on both devices. 相似文献
6.
Alberto Plaza Sonia Piacente Angela Perrone Arafa Hamed Cosimo Pizza Giuseppe Bifulco 《Tetrahedron》2004,60(52):12201-12209
Stemmosides C and D, two novel pregnane glycosides characterized by an unusual C-17 side chain were isolated from the pericarps of Solenostemma argel. In addition, stemmoside D displays an uncommon 14β proton configuration, apparently being the first pregnane isolated from plants known to have a 15 keto, cis CD ring junction. Their structures have been established by ESIMS and NMR experiments. The relative configuration of the molecules was determined using a strategy based on the simulation of 1H, 13C, and J coupling NMR parameters. DFT calculations of 1H and 13C chemical shifts, and of the 1H homonuclear spin–spin coupling constants were performed with the mPW1PW91 functional using the 6-31G(d,p) basis set on the fully optimized geometries of all the possible stereoisomers. 相似文献
7.
8.
9.
Giuseppe Mingione 《Applications of Mathematics》2006,51(4):355-426
I am presenting a survey of regularity results for both minima of variational integrals, and solutions to non-linear elliptic,
and sometimes parabolic, systems of partial differential equations. I will try to take the reader to the Dark Side...
This work has been partially supported by MIUR via the project “Calcolo delle Variazioni” (Cofin 2004), and by GNAMPA via
the project “Studio delle singolarità in problemi geometrici e variazionali”. 相似文献
10.
Giuseppe Gaeta 《Annals of Physics》2004,312(2):511-540
In the Landau theory of phase transitions one considers an effective potential Φ whose symmetry group G and degree d depend on the system under consideration; generally speaking, Φ is the most general G-invariant polynomial of degree d. When such a Φ turns out to be too complicate for a direct analysis, it is essential to be able to drop unessential terms, i.e., to apply a simplifying criterion. Criteria based on singularity theory exist and have a rigorous foundation, but are often very difficult to apply in practice. Here we consider a simplifying criterion (as stated by Gufan) and rigorously justify it on the basis of classical Lie-Poincaré theory as far as one deals with fixed values of the control parameter(s) in the Landau potential; when one considers a range of values, in particular near a phase transition, the criterion has to be accordingly partially modified, as we discuss. We consider some specific cases of group G as examples, and study in detail the application to the Sergienko-Gufan-Urazhdin model for highly piezoelectric perovskites. 相似文献