全文获取类型
收费全文 | 71132篇 |
免费 | 13619篇 |
国内免费 | 4316篇 |
专业分类
化学 | 64882篇 |
晶体学 | 682篇 |
力学 | 2116篇 |
综合类 | 188篇 |
数学 | 6360篇 |
物理学 | 14839篇 |
出版年
2023年 | 519篇 |
2022年 | 998篇 |
2021年 | 1170篇 |
2020年 | 2235篇 |
2019年 | 3519篇 |
2018年 | 2006篇 |
2017年 | 1524篇 |
2016年 | 4725篇 |
2015年 | 4696篇 |
2014年 | 4963篇 |
2013年 | 6360篇 |
2012年 | 5543篇 |
2011年 | 5012篇 |
2010年 | 4743篇 |
2009年 | 4568篇 |
2008年 | 4450篇 |
2007年 | 3697篇 |
2006年 | 3214篇 |
2005年 | 3176篇 |
2004年 | 2744篇 |
2003年 | 2422篇 |
2002年 | 3189篇 |
2001年 | 2258篇 |
2000年 | 2043篇 |
1999年 | 1180篇 |
1998年 | 627篇 |
1997年 | 599篇 |
1996年 | 559篇 |
1995年 | 533篇 |
1994年 | 472篇 |
1993年 | 427篇 |
1992年 | 347篇 |
1991年 | 373篇 |
1990年 | 346篇 |
1989年 | 269篇 |
1988年 | 251篇 |
1987年 | 224篇 |
1986年 | 210篇 |
1985年 | 285篇 |
1984年 | 294篇 |
1983年 | 196篇 |
1982年 | 218篇 |
1981年 | 173篇 |
1980年 | 181篇 |
1979年 | 151篇 |
1978年 | 131篇 |
1977年 | 175篇 |
1976年 | 159篇 |
1975年 | 137篇 |
1973年 | 130篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
V. De Sabbata C. Sivaram H.-H. v. Borzeszkowski H.-J. Treder 《Annalen der Physik》1991,503(7):497-502
It is shown that in gravitational theories with torsion one is led to commutation rules corresponding to Landau-Peierls type uncertainty relations. 相似文献
82.
本文对特征P的基域F引入适当的Galois群T,讨论p置换模的Green环的Conlon比析在Galois群T作用下的动态,证明了在T作用下p置换模的Green环的不动点集重合于置换模的Green环。 相似文献
83.
84.
利用多靶磁控溅射技术制备了Au/SiO2纳米颗粒分散氧化物多层复合薄膜.研究了在保持Au单层颗粒膜沉积时间一定时薄膜厚度一定、变化SiO2的沉积时间及SiO2的沉积时间一定而改变薄膜厚度时,多层薄膜在薄膜厚度方向的微观结构对吸收光谱的影响.研究结果表明:具有纳米层状结构的Au/SiO2多层薄膜在560nm波长附近有明显的表面等离子共振吸收峰,吸收峰的强度随Au颗粒的浓度增加而增强,在Au颗粒浓度相同的情况下,复合薄膜光学吸收强度随薄膜厚度的增加而增强.但当金属颗粒的浓度增加到一定程度时,金属颗粒相互接触,没有观察到纳米层状结构,薄膜不显示共振吸收峰特征.用修正后的M-G(Maxwell-Garnett)理论对吸收光谱进行了模拟,得到了与实验一致的结果. 相似文献
85.
A two-dimensional, nonlinear, compressible, diabatic, nonhydrostatic photochemical-dynamical gravity wave model has been advanced. The model includes diabetic process produced by photochemistry and the effect of gravity wave on atmospheric chemical species. In the horizontal direction, the pseudospectral method is used. The finite difference approximations are used in vertical direction z and time t. The FICE method is used to solve the model. The model results on small amplitude fluctuation are very close to those of linear theory, which demonstrates the correctness of the model.
相似文献86.
D. De Salvador A. Coati E. Napolitani M. Berti A.V. Drigo M.S. Carroll J.C. Sturm J. Stangl G. Bauer L. Lazzarini 《Applied Physics A: Materials Science & Processing》2002,75(6):667-672
In this work we investigate the diffusion and precipitation of supersaturated substitutional carbon in 200-nm-thick SiGeC
layers buried under a silicon cap layer of 40 nm. The samples were annealed in either inert (N2) or oxidizing (O2) ambient at 850 °C for times ranging from 2 to 10 h. The silicon self-interstitial (I) flux coming from the surface under
oxidation enhances the C diffusion with respect to the N2-annealed samples. In the early stages of the oxidation process, the loss of C from the SiGeC layer by diffusion across the
layer/cap interface dominates. This phenomenon saturates after an initial period (2–4 h), which depends on the C concentration.
This saturation is due to the formation and growth of C-containing precipitates that are promoted by the I injection and act
as a sink for mobile C atoms. The influence of carbon concentration on the competition between precipitation and diffusion
is discussed.
Received: 19 October 2001 / Accepted: 19 December 2001 / Published online: 20 March 2002 / Published online: 20 March 2002 相似文献
87.
88.
T. Temesvári C. De Dominicis I.R. Pimentel 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(3):361-372
Symmetry considerations and a direct, Hubbard-Stratonovich type, derivation are used to construct a replica field-theory relevant
to the study of the spin glass transition of short range models in a magnetic field. A mean-field treatment reveals that two
different types of transitions exist, whenever the replica number n is kept larger than zero. The Sherrington-Kirkpatrick critical point in zero magnetic field between the paramagnet and replica
magnet (a replica symmetric phase with a nonzero spin glass order parameter) separates from the de Almeida-Thouless line,
along which replica symmetry breaking occurs. We argue that for studying the de Almeida-Thouless transition around the upper
critical dimension d = 6, it is necessary to use the generic cubic model with all the three bare masses and eight cubic couplings. The critical
role n may play is also emphasized. To make perturbative calculations feasible, a new representation of the cubic interaction is
introduced. To illustrate the method, we compute the masses in one-loop order. Some technical details and a list of vertex
rules are presented to help future renormalisation-group calculations.
Received 9 October 2001 相似文献
89.
A new method is introduced to generate a elliptical hollow beam inside a cavity. Using a matrix eigenvalue method, the laser resonator with optical diffraction elements is theoretically analyzed and simulated. A elliptical hollow beam of good quality is realized experimentally. The interaction between linearly polarized elliptical hollow beam and a two-level atom is investigated theoretically. Although the linearly polarized elliptical hollow beam does not carry angular momentum, it can produce very high torque. The atoms initially at rest and located at off-beam- axis positions will rotate under the drive of the torque of the beam. The atomic motion trajectory in the field of elliptical hollow beam has been demonstrated. The study shows that the elliptical hollow beam might be a useful tool in the study of vortex property of Bose-Einstein condensate or ultra cold atom media. 相似文献
90.