全文获取类型
收费全文 | 29015篇 |
免费 | 1804篇 |
国内免费 | 870篇 |
专业分类
化学 | 7011篇 |
晶体学 | 332篇 |
力学 | 1790篇 |
综合类 | 216篇 |
数学 | 11046篇 |
物理学 | 11294篇 |
出版年
2023年 | 183篇 |
2022年 | 340篇 |
2021年 | 317篇 |
2020年 | 336篇 |
2019年 | 631篇 |
2018年 | 484篇 |
2017年 | 498篇 |
2016年 | 426篇 |
2015年 | 368篇 |
2014年 | 538篇 |
2013年 | 1433篇 |
2012年 | 811篇 |
2011年 | 1326篇 |
2010年 | 796篇 |
2009年 | 1157篇 |
2008年 | 1303篇 |
2007年 | 1335篇 |
2006年 | 1255篇 |
2005年 | 925篇 |
2004年 | 1277篇 |
2003年 | 1433篇 |
2002年 | 1968篇 |
2001年 | 1953篇 |
2000年 | 1783篇 |
1999年 | 1955篇 |
1998年 | 1659篇 |
1997年 | 1058篇 |
1996年 | 558篇 |
1995年 | 324篇 |
1994年 | 280篇 |
1993年 | 131篇 |
1992年 | 152篇 |
1991年 | 114篇 |
1990年 | 193篇 |
1989年 | 166篇 |
1988年 | 123篇 |
1987年 | 94篇 |
1986年 | 136篇 |
1985年 | 209篇 |
1984年 | 189篇 |
1983年 | 87篇 |
1982年 | 145篇 |
1981年 | 241篇 |
1980年 | 238篇 |
1979年 | 115篇 |
1978年 | 175篇 |
1977年 | 105篇 |
1976年 | 77篇 |
1975年 | 82篇 |
1974年 | 78篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
D. Chithrani R. L. Williams J. Lefebvre P. J. Poole G. C. Aers 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):290
We discuss the preparation and spectroscopic characterisation of a single InAs/InP quantum dot suitable for long-distance quantum key distribution applications around λ=1.55 μm. The dot is prepared using a site-selective growth technique which allows a single dot to be deposited in isolation at a controlled spatial location. Micro-photoluminescence measurements as a function of exciton occupation are used to determine the electronic structure of the dot. Biexciton emission, shell filling and many-body re-normalization effects are observed for the first time in single InAs/InP quantum dots. 相似文献
172.
Howard Jacobowitz Gerardo Mendoza 《Transactions of the American Mathematical Society》2003,355(10):4201-4222
We study embeddings of complex vector bundles, especially line bundles, in the complexification of the tangent bundle of a manifold. The aim is to understand implications of properties of interest in partial differential equations.
173.
Bradley L. Thiel 《Mikrochimica acta》2004,145(1-4):243-247
The role of positive gaseous ions in the formation of secondary electron images in low vacuum scanning electron microscopes is discussed. This paper describes the charging processes and related effects that occur during high vacuum imaging of insulators and then discusses the influence of ions on those processes. The ions are responsible for a number of phenomena, including distortion of the electric field above and below the specimen surface due to space charge, removal of excess negative charge from the specimen, alteration of the specimen surface barrier, and scavenging/filtering of the secondary electron emission. The resulting electron-specimen-ion interactions can give rise to interesting contrast effects that are unique to this class of instruments. 相似文献
174.
175.
Summary. We consider the spline collocation method for a class of parabolic pseudodifferential operators. We show optimal order convergence
results in a large scale of anisotropic Sobolev spaces. The results cover the classical boundary integral equations for the
heat equation in the general case where the spatial domain has a smooth boundary in the plane. Our proof is based on a localization
technique for which we use our recent results proved for parabolic pseudodifferential operators. For the localization we need
also some special spline approximation results in anisotropic Sobolev spaces.
Received May 17, 2001 / Revised version received February 19, 2002 / Published online April 17, 2002 相似文献
176.
Toshiyuki Sugawa 《Monatshefte für Mathematik》2003,139(1):61-68
The inner radius of univalence of a domain D with Poincaré density ρ
D
is the possible largest number σ such that the condition ∥ S
f
∥
D
= sup
w∈ D
ρ
D
(w)
−2∥ S
f
(z) ∥ ≤ σ implies univalence of f for a nonconstant meromorphic function f on D, where S
f
is the Schwarzian derivative of f. In this note, we give a lower bound of the inner radius of univalence for strongly starlike domains of order α in terms
of the order α.
The author was partially supported by the Ministry of Education, Grant-in-Aid for Encouragement of Young Scientists, 11740088.
A part of this work was carried out during his visit to the University of Helsinki under the exchange programme of scientists
between the Academy of Finland and the JSPS.
Received November 26, 2001; in revised form September 24, 2002
Published online May 9, 2003 相似文献
177.
178.
K. L. Janssens B. Partoens F. M. Peeters 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):349
We investigated theoretically the influence of strain on the exciton in both single and three vertically coupled self-assembled quantum dot systems in the presence of a perpendicular magnetic field. For the single disk, we find that the heavy-hole exciton is the ground state, while for the system of three stacked disks, the light hole state was found to be lower in energy. Results for the diamagnetic shift were compared with experimental results. 相似文献
179.
Bi12TiO20纳米粉体的制备及其光吸收特性研究 总被引:3,自引:0,他引:3
以钛酸四丁酯和硝酸铋为原料 ,利用化学溶液分解法制备了Bi12 TiO2 0 纳米多晶粉体 .采用XRD和TEM对其结构和形貌进行了表征 .结合热重 差热 (TG DTA)分析 ,探讨了Bi12 TiO2 0 晶相的形成机理 .通过UV Vis漫反射谱的测定 ,研究了Bi12 TiO2 0 纳米晶粉体的光吸收特性 .结果显示 ,从组成为化学计量比的前驱液中可以很容易制得纯Bi12 TiO2 0 纳米晶粉体 ,该Bi12 TiO2 0 纳米晶粉体呈现了在很宽的波长范围内 (5 6 0~ 385nm )对光的吸收的特性 . 相似文献
180.
YunFei Liu ShengCai Shi ShengLin Yu 《International Journal of Infrared and Millimeter Waves》2003,24(12):2069-2077
When electromagnetic waves propagate through a wire grid, there will be some evanescent space harmonics generated around the wire grid. In this paper, we mainly investigate their effects on the transmission characteristics of a Gaussian beam by cylindrical wire grids. The results are compared with those without taking account of evanescent space-harmonics. 相似文献