全文获取类型
收费全文 | 7821篇 |
免费 | 328篇 |
国内免费 | 52篇 |
专业分类
化学 | 5445篇 |
晶体学 | 53篇 |
力学 | 164篇 |
数学 | 1279篇 |
物理学 | 1260篇 |
出版年
2023年 | 72篇 |
2022年 | 105篇 |
2021年 | 170篇 |
2020年 | 167篇 |
2019年 | 117篇 |
2018年 | 154篇 |
2017年 | 139篇 |
2016年 | 283篇 |
2015年 | 273篇 |
2014年 | 313篇 |
2013年 | 559篇 |
2012年 | 545篇 |
2011年 | 662篇 |
2010年 | 385篇 |
2009年 | 330篇 |
2008年 | 497篇 |
2007年 | 502篇 |
2006年 | 407篇 |
2005年 | 385篇 |
2004年 | 350篇 |
2003年 | 273篇 |
2002年 | 253篇 |
2001年 | 149篇 |
2000年 | 130篇 |
1999年 | 101篇 |
1998年 | 51篇 |
1997年 | 71篇 |
1996年 | 107篇 |
1995年 | 50篇 |
1994年 | 47篇 |
1993年 | 45篇 |
1992年 | 49篇 |
1991年 | 27篇 |
1990年 | 24篇 |
1989年 | 23篇 |
1988年 | 19篇 |
1987年 | 25篇 |
1986年 | 27篇 |
1985年 | 36篇 |
1984年 | 37篇 |
1983年 | 30篇 |
1982年 | 30篇 |
1981年 | 19篇 |
1980年 | 14篇 |
1979年 | 26篇 |
1978年 | 21篇 |
1977年 | 16篇 |
1976年 | 16篇 |
1974年 | 13篇 |
1973年 | 17篇 |
排序方式: 共有8201条查询结果,搜索用时 0 毫秒
101.
Guadalupe Valverde-Aguilar Jorge A. García-Macedo Víctor M. Rentería-Tapia Raúl W. Gómez Manuel Quintana-García 《Journal of nanoparticle research》2011,13(10):4613-4622
Hexagonal mesostructured films containing silver ions were obtained by sol–gel method. Brij 58 was used to produce channels
into the film, which house these ions. The films were exposure to UV radiation to produced silver metallic nanoparticles.
The presence of the metallic nanoparticles was determined by infrared spectroscopy and optical absorption. Besides, these
nanoparticles and core–shell structures of silver–silver oxide nanoparticles were identified by high-resolution transmission
electronic microscopy. From these measurements, the obtained size range for silver nanoparticles was 6.1 nm. The absorption
spectrum located at 440 nm was modelled and well fitted with the Gans theory considering refractive index higher than the
one coming from host matrix. This index is explained because the silver oxide shell modifies the local surrounding medium
of the metallic nanoparticles. 相似文献
102.
The behavior of the polarization in a microscopic statistical model for a thin film relaxor placed between two metallic electrodes is studied by numerical simulations. Depolarization fields different from zero, due to a non-perfect compensation of surface charges at the metallic electrodes, are taken into account. Different thicknesses and different values of the compositional charge disorder density for the relaxor are considered. Depolarization field is found to be extremely attenuated for large values of the number density of charge carriers in the relaxor. In such a case, field attenuation allows for the existence of a homogeneous ferroelectric ground state. 相似文献
103.
104.
Alexander P. Chetverikov Werner Ebeling Manuel G. Velarde 《Physica D: Nonlinear Phenomena》2011,240(24):1954-1959
Nano-scale soliton-like supersonic, intrinsic localized excitations in two-dimensional atomic anharmonic lattice layers are here considered. We study the propagation, the velocity and other soliton-like features at head-on collisions of such lattice excitations created by using suitable initial mechanical and thermal conditions. Noteworthy is that narrow, highly-energetic solitons moving along one lattice row are very robust, accompanied by weak anti-phase oscillations in the lateral direction. 相似文献
105.
Francisco Javier Gallego Miguel González Bangere P. Purnaprajna 《Inventiones Mathematicae》2010,182(1):1-46
In this article we study the deformation of finite maps and show how to use this deformation theory to construct varieties
with given invariants in a projective space. Among other things, we prove a criterion that determines when a finite map can
be deformed to a one-to-one map. We use this criterion to construct new surfaces of general type with birational canonical
map, for different c12c_{1}^{2} and χ (the canonical map of the surfaces we construct is in fact a finite, birational morphism). Our general results enable us
to describe some new components of the moduli of surfaces of general type. We also find infinitely many moduli spaces having one component whose general point corresponds to a canonically embedded surface and another component whose general
point corresponds to a surface whose canonical map is a degree 2 morphism. 相似文献
106.
The global formulation of the higher-order Poincaré-Cartan form for Lagrangian field theories in the calculus of variations is re-examined in terms of the theory of lifts of tensor fields on a manifold to its higher-order prolongated jet bundles.Partially supported by CNPq, Brazil, Proc. MA 30.1115/79. 相似文献
107.
108.
Manuel Gonzá lez Joaquí n M. Gutié rrez José G. Llavona 《Proceedings of the American Mathematical Society》1997,125(5):1349-1353
A mapping between Banach spaces is said to be polynomially continuous if its restriction to any bounded set is uniformly continuous for the weak polynomial topology. A Banach space has property (RP) if given two bounded sequences , we have that for every polynomial on whenever for every polynomial on ; i.e., the restriction of every polynomial on to each bounded set is uniformly sequentially continuous for the weak polynomial topology. We show that property (RP) does not imply that every scalar valued polynomial on must be polynomially continuous.
109.
Let (Mr)r∈? 0 be a logarithmically convex sequence of positive numbers which verifies M0 = 1 as well as Mr ≥ 1 for every r ∈ ? and defines a non quasi-analytic class. Let moreover F be a closed proper subset of ?n. Then for every function ? on ?n belonging to the non quasi-analytic (Mr)-class of Roumieu type, there is an element g of the same class which is analytic on ?n F and such that Dα ?(x) = Dαg(x) for every σ ∈ ?0 n SBAP and x ∈ F. 相似文献
110.
P. González D. Fernández J. Pou E. García J. Serra B. León M. Pérez-Amor T. Szörényi 《Applied Physics A: Materials Science & Processing》1993,57(2):181-185
A study of the gas-phase parameters involved in ArF laser induced chemical vapour deposition of silicon-oxide thin films is presented. A complete set of experiments has been performed showing the influence of the concentration of the precursor gases, N2O and SiH4, and their influence on total and partial pressures on film growth and properties. In this paper we demonstrate the ability of this LCVD method to deposit silicon oxide films of different compositions and densities by appropriate control of gas composition and total pressure. Moreover, a material specific calibration plot comprising data obtained using different preparation techniques is presented, allowing determination of the stoichiometry of SiO
x
films by using FTIR spectroscopy independently of the deposition method. For the range of processing conditions examined, the experimental results suggest that chemical processes governing deposition take place mainly in the gas phase. 相似文献