全文获取类型
收费全文 | 4126篇 |
免费 | 120篇 |
国内免费 | 11篇 |
专业分类
化学 | 3140篇 |
晶体学 | 34篇 |
力学 | 37篇 |
数学 | 385篇 |
物理学 | 661篇 |
出版年
2023年 | 22篇 |
2022年 | 38篇 |
2021年 | 84篇 |
2020年 | 72篇 |
2019年 | 70篇 |
2018年 | 44篇 |
2017年 | 46篇 |
2016年 | 108篇 |
2015年 | 99篇 |
2014年 | 110篇 |
2013年 | 239篇 |
2012年 | 213篇 |
2011年 | 253篇 |
2010年 | 151篇 |
2009年 | 144篇 |
2008年 | 240篇 |
2007年 | 248篇 |
2006年 | 210篇 |
2005年 | 214篇 |
2004年 | 153篇 |
2003年 | 150篇 |
2002年 | 104篇 |
2001年 | 59篇 |
2000年 | 74篇 |
1999年 | 43篇 |
1998年 | 24篇 |
1997年 | 39篇 |
1996年 | 41篇 |
1995年 | 27篇 |
1994年 | 31篇 |
1993年 | 47篇 |
1991年 | 31篇 |
1990年 | 29篇 |
1989年 | 29篇 |
1988年 | 28篇 |
1987年 | 40篇 |
1986年 | 39篇 |
1985年 | 43篇 |
1984年 | 39篇 |
1983年 | 29篇 |
1982年 | 40篇 |
1981年 | 28篇 |
1980年 | 39篇 |
1979年 | 28篇 |
1978年 | 21篇 |
1977年 | 30篇 |
1976年 | 23篇 |
1975年 | 22篇 |
1974年 | 29篇 |
1973年 | 20篇 |
排序方式: 共有4257条查询结果,搜索用时 46 毫秒
951.
952.
953.
Aug Vogel 《Fresenius' Journal of Analytical Chemistry》1884,23(1):536-537
Ohne Zusammenfassung 相似文献
954.
Ioana Lacatusu Nicoleta Badea Dionezie Bojin Silvia Iosub Aurelia Meghea 《Journal of Sol-Gel Science and Technology》2009,51(1):84-91
Synthesis of some novel fluorescence nanomaterials loaded with photoactive polyphenols originated from plants with a high
spectrum of biological activity, by replacing synthetic chemicals, may open new opportunities for optical and bio-medical
applications. This paper presents the synthesis, characterization and fluorescence properties of a new class of materials
based on host hybrid matrices obtained through templated sol–gel route, by hydrolysis and co-condensation of tetraorthoethylsilicate
with octaisobutyltetracyclo [7.3.3.15,11] octasiloxane-endo-3,7-diol. The aim of paper is focused on the evaluation of the behavior of the fluorescence properties
of ornamental bush extract at immobilization in a templated silica matrix and in a silica-silsesquioxane network, using as
templates a neutral, non-toxic and biodegradable surfactant from poly(ethyleneglycol) class and a high biocompatible non-surfactant
from glucidic class. The proofs of ornamental bush extract entrapment by physical interactions in silica based networks were
provided by FT-IR and UV–VIS spectroscopy. The changes of polymer network due to the hydrogen bond interactions between residual
Si–OH groups and functional groups of organic molecules from extract were evidenced by shifts of specific vibrations. In UV–VIS-NIR
domain, the chromophore groups from ornamental bush extract were also evidenced by similar small shifts. As a result of ornamental
bush extract entrapment, in all the immobilized samples the fluorescence intensity was more than 10 times amplified in samples
templated with poly(ethylenglycol) surfactant) and of about 5 times in samples with glucidic template due to the physical
adsorption of polyphenolic molecules from extract, excellent synergistic optical properties of SiO2 and silsesquioxane compound and also due to a favorable conformational arrangement. The size of synthesized polymeric materials,
estimated by dynamic light scattering technique showed main diameters less then 1.4 μm, namely 1,060 and 211 nm—for samples
with d-glucose template and 1,330 and 531 nm—for samples with poly(ethyleneglycol) template, respectively, with a narrow size distribution
and a polidispersity varying between 0.022 and 0.426. These results are in good accordance with TEM images that evidenced
the presence of some polymeric aggregates which contain the vegetal extract immobilized inside hybrid SiO2-Sq polymeric network of about hundred nanometers size. This study bring new contributions to the development of the sol–gel
procedure by entrapment of a complex vegetable mixture in polymeric matrices as integral component of silica and hybrid silica-silsesquioxane
networks which leads to a significant enhancement of the functional properties of the final material, thus diversifying the
potential applications of organic doped sol–gel glasses. 相似文献
955.
956.
This paper deals with the study of a mathematical model of photon transport in an interstellar cloud where a localized source is present. The source is represented by a Dirac delta functional. The problem is studied in the setting of locally convex spaces. By means of the theory of semigroups on locally convex spaces and the adjoint approach, we prove existence and uniqueness of the solution. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
957.
958.
Soft X-ray resonant magnetic scattering (SXRMS) has been used to investigate the microscopic magnetization reversal behavior of complex magnetic systems. SXRMS is a unique technique, providing chemical, spatial and magnetic sensitivity, which is not affected by external magnetic fields. The study of two selected thin magnetic heterostructures is presented, amorphous rare-earth transition metal alloys and perpendicular exchange coupled antiferromagnetic/ferromagnetic films. In the first system, the internal structure of magnetic stripe domains on nanometer length scales is obtained by measuring bi-dimensional (2D) scattering images. In the second system, the element specificity is exploited to identify the role of the uncompensated spins in the antiferromagnetic layer on the exchange coupling phenomena. Future trends are also discussed. 相似文献
959.
Isabella Miglioli Luca Muccioli Silvia Orlandi Matteo Ricci Roberto Berardi Claudio Zannoni 《Theoretical chemistry accounts》2007,118(1):203-210
We set up a model for discotic liquid crystal dimers and study, by means of Monte Carlo simulations, their phase behaviour
and self–assembling properties, in comparison with the simpler monomeric case. Each discotic dimer is described by two oblate
Gay–Berne ellipsoids connected by a flexible spacer, modelled by a harmonic “spring” of three different lengths. We find that
dimerization in general yields produces a significant change on the phase behaviour, with an increase of the columnar–nematic
transition temperature, a widening of the nematic region and the apparent suppression of the crystalline phase in favour of
the columnar phase up to very low temperatures. Longer spacers prove to ease the formation of columns and to increase the
orientational order.
Contribution to the Fernando Bernardi memorial issue. 相似文献
960.