全文获取类型
收费全文 | 954篇 |
免费 | 23篇 |
专业分类
化学 | 692篇 |
晶体学 | 10篇 |
力学 | 23篇 |
数学 | 139篇 |
物理学 | 113篇 |
出版年
2023年 | 4篇 |
2022年 | 33篇 |
2021年 | 33篇 |
2020年 | 15篇 |
2019年 | 13篇 |
2018年 | 16篇 |
2017年 | 11篇 |
2016年 | 37篇 |
2015年 | 17篇 |
2014年 | 25篇 |
2013年 | 51篇 |
2012年 | 50篇 |
2011年 | 51篇 |
2010年 | 40篇 |
2009年 | 46篇 |
2008年 | 58篇 |
2007年 | 55篇 |
2006年 | 59篇 |
2005年 | 50篇 |
2004年 | 47篇 |
2003年 | 42篇 |
2002年 | 32篇 |
2001年 | 12篇 |
2000年 | 6篇 |
1999年 | 13篇 |
1998年 | 9篇 |
1997年 | 9篇 |
1996年 | 14篇 |
1995年 | 8篇 |
1994年 | 13篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1973年 | 3篇 |
1971年 | 1篇 |
1940年 | 1篇 |
排序方式: 共有977条查询结果,搜索用时 15 毫秒
1.
We report on the realization and characterization of electro-responsive and pressure sensitive polydimethylsiloxane (PDMS) conductive photonic structures combined with the reconfigurable properties of short pitch cholesteric liquid crystals (aligned in Grandjean configuration). By combining ion-implantation process and surface chemistry functionalization, we have overcome the insulating properties of PDMS and induced long range organization of cholesteric liquid crystals, thus controlling both diffraction and selective Bragg reflection of light by means of external perturbations (electric field, pressure). We have characterized our devices in terms of morphological, optical and electro-optical properties. 相似文献
2.
Infinite dimensional duality and applications 总被引:2,自引:0,他引:2
Patrizia Daniele Sofia Giuffrè Giovanna Idone Antonino Maugeri 《Mathematische Annalen》2007,339(1):221-239
The usual duality theory cannot be applied to infinite dimensional problems because the underlying constraint set mostly has
an empty interior and the constraints are possibly nonlinear. In this paper we present an infinite dimensional nonlinear duality
theory obtained by using new separation theorems based on the notion of quasi-relative interior, which, in all the concrete
problems considered, is nonempty. We apply this theory to solve the until now unsolved problem of finding, in the infinite
dimensional case, the Lagrange multipliers associated to optimization problems or to variational inequalities. As an example,
we find the Lagrange multiplier associated to a general elastic–plastic torsion problem. 相似文献
3.
4.
V. Vittoria R. Russo F. De Candia P. L. Magagnini B. Bresci 《Journal of Polymer Science.Polymer Physics》1991,29(9):1163-1168
The transport properties of a side-chain liquid-crystalline polymer forming a smectic A phase have been investigated using dichloromethane as a permeant. Samples differing in the isotropization enthaoly were analyzed. A. Correlation between this thermal parameter and sorption has been found, while the diffusion coefficient is substantially the same in all samples. The results obtained can be explained in terms of a biphasis model in which a disordered permeable phase is present within the liquid-crystalline phase, which is impermeable to the diffusant molecules. 相似文献
5.
Giovanna Idone 《Journal of Mathematical Analysis and Applications》2004,290(1):147-170
Hölder regularity up to the boundary of the solutions to the Dirichlet problem for second order elliptic systems with nonlinearity q>2 and with controlled growth is proved when n?q+2. 相似文献
6.
7.
Giovanna Citti 《Rendiconti del Circolo Matematico di Palermo》1986,35(3):364-375
In questa nota proviamo un teorema di esistenza di soluzioni positive su tuttoR n della equazionediv(|Du| p?2Du)+f(u)=0. 相似文献
8.
Marco Berettoni Giovanna De Chiara Tommaso Iacoangeli Paola Lo Surdo Rinaldo Marini Bettolo Lorenzo Montagnini Di Mirabello Luca Nicolini Rita Scarpelli 《Helvetica chimica acta》1996,79(7):2035-2041
A novel preparation of methyl (13S)-13-hydroxyisoatisiren-18-oate ( 4 ), a key-intermediate in a synthesis of (+)-methyl trachyloban-18-oate ((+)- 1 ), from (?)-abietic acid, is described. Since (?)- 1 has been previously converted into (?)-methyl 16-oxo-17-norkauran-18-oate ((?)- 16 ), our preparation of 4 constitutes also a formal total synthesis, from (?)-abietic acid, of (+)- 16 . Key steps in this approach were the allene photoaddition to podocarp-8(14)-en-13-one ( 5 ) and the conversion of the endo-toluene-4-sulfonate 11 into the exo-benzoate 12b . 相似文献
9.
Crovella S Antcheva N Zelezetsky I Boniotto M Pacor S Verga Falzacappa MV Tossi A 《Current protein & peptide science》2005,6(1):7-21
Host defense peptides (HDPs) are endogenous antibiotics that play a multifunctional role in the innate immunity of mammals. Among these, beta-defensins contribute to mucosal and epithelial defense, also acting as signal molecules for cellular components of innate and adaptive immunity. Numerous members of this family have been identified in mammalian and avian species, and genomic studies in human and mouse indicate a considerable complexity in their gene organization. Recent reports on the evolution of primate and rodent members of this family indicate quite a complex pattern of variation. In this review we briefly discuss the evolution of mammalian beta-defensins in relation to other types of defensins, and then concentrate on the evolution of beta-defensins 1 to 4 in primates. In particular, the surprisingly varied patterns of evolution, which range from neutral or weakly purifying, to positive selection to a high level of conservation are analyzed in terms of possible genetics, structural or functional implications, as well as to observed variations on the antimicrobial activity in vitro. The role of polymorphisms in the genes encoding for these host defense peptides in determining susceptibility to human diseases are also briefly considered. 相似文献
10.
Fabrizio Melani Lucia Cecchi Giovanna Palazzino Guido Filacchioni 《Journal of heterocyclic chemistry》1986,23(1):173-176
Following our reports on synthetic tricyclic analogues of antitumor anthramycin the synthesis of some isomers pyrazolo[4,5-d]- and pyrazolo[4,5-c][1]benzazepine derivatives is reported. 相似文献