全文获取类型
收费全文 | 11351篇 |
免费 | 837篇 |
国内免费 | 657篇 |
专业分类
化学 | 2986篇 |
晶体学 | 157篇 |
力学 | 550篇 |
综合类 | 27篇 |
数学 | 324篇 |
物理学 | 8801篇 |
出版年
2024年 | 14篇 |
2023年 | 91篇 |
2022年 | 130篇 |
2021年 | 129篇 |
2020年 | 175篇 |
2019年 | 187篇 |
2018年 | 203篇 |
2017年 | 277篇 |
2016年 | 386篇 |
2015年 | 358篇 |
2014年 | 866篇 |
2013年 | 771篇 |
2012年 | 565篇 |
2011年 | 1028篇 |
2010年 | 696篇 |
2009年 | 828篇 |
2008年 | 785篇 |
2007年 | 860篇 |
2006年 | 650篇 |
2005年 | 525篇 |
2004年 | 502篇 |
2003年 | 411篇 |
2002年 | 357篇 |
2001年 | 356篇 |
2000年 | 240篇 |
1999年 | 273篇 |
1998年 | 263篇 |
1997年 | 155篇 |
1996年 | 140篇 |
1995年 | 109篇 |
1994年 | 81篇 |
1993年 | 85篇 |
1992年 | 43篇 |
1991年 | 45篇 |
1990年 | 41篇 |
1989年 | 28篇 |
1988年 | 35篇 |
1987年 | 32篇 |
1986年 | 15篇 |
1985年 | 18篇 |
1984年 | 26篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 11篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1974年 | 4篇 |
1973年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Soliton interaction under the influence of higher-order effects 总被引:6,自引:0,他引:6
In this paper, we present exact N-soliton solution by employing simple, straightforward Darboux transformation based on the Lax pair for Hirota equation, a higher-order nonlinear Schrödinger (HNLS) equation. As examples, one- and two-soliton solutions in explicit forms are given and their properties are also analyzed. A bound solution without interaction will be theoretically predicted if one can adjust frequency shift for each soliton appropriately. Further, we obtain the approximate eigenvalues by employing two-soliton solution and discuss analytically the interaction between neighboring solitons under the influence of the higher-order effects. It is shown that the combined effects of the higher-order effects can restrain the interaction between neighboring solitons to some extent. The results are proved by directly solving HNLS equation numerically. 相似文献
23.
We derive an explicit autocorrelation function (ACF) formula of state of polarization for a fiber transmission system with polarization mode dispersion (PMD) and polarization dependent loss (PDL), which is found to agree well with Monte Carlo simulation. Then we use the new ACF to investigate the combined effect of PMD and PDL on the polarization multiplexed scheme. We find the performance of the polarization multiplexed scheme can be deteriorated more severely than the case without PDL. 相似文献
24.
The propagation property of flattened Gaussian beams (FGBs) is studied based on the Collins formula, and analytical propagation equations for FGBs with and without an aperture are derived. It is shown that the closed-form expressions for the FGB of order N passing through paraxial ABCD optical systems without an aperture can be written as the combinations of Confluent Hyper-geometric Functions, and that the analytical equations for the FGB of order N passing through apertured paraxial ABCD optical systems may involve Error Functions. The proposed algorithms for the considered beams can save computing time, provide intuitive physical insights, and help to design optical systems. Our results are confirmed and illustrated with numerical examples. 相似文献
25.
26.
27.
28.
Giuseppe Coppola Andrea Irace Giovanni Breglio Mario Iodice Luigi Zeni Antonello Cutolo Pasqualina M. Sarro 《Optics and Lasers in Engineering》2003,39(3):317-332
In this paper we describe two different kind of optoelectronic devices both based on a three terminals active device and exploit the plasma dispersion effect to achieve the desired working. The first device exploits this effect in order to obtain an optical modulation. The second device is an optoelectronic router based on the mode-mixing principle together with the injection-induced optical phase shift. Both devices are integrated into a Silicon on Silicon optical channel waveguide which can be realized using a standard bipolar process. The possibility of using standard, well-known technology presents several advantages with respect to III–V Optoelectronics. The active three terminal device used is a Bipolar Mode Field Effect Transistor (BMFET). Numerical simulation results are presented on both devices. 相似文献
29.
The identification of incomplete signal re-setting of optically stimulated luminescence signals in sedimentary quartz is a vitally important step in the continued improvement of optical dating. It is shown that narrow spectrum (blue-green) laboratory partial bleaching of aliquots of natural sedimentary quartz has a significant effect on equivalent dose (measured using a single aliquot procedure) calculated as a function of measurement time (De(t)). The blue-green stimulation spectrum mimics that found underwater and the results suggest that incomplete re-setting of waterlain sediments may be possible using the De(t) method. 相似文献
30.
A two-step swelling procedure was adopted to synthesize mono-dispersed and highly cross-linked poly (St-divinylbenzene) particles
with PSt micro-spheres (1.80 μm in diameter). The PSt micro-spheres were prepared by a dispersion polymerization method and
used as seeds. The effects of monomer concentration, ratio of ethanol to water, swelling reagents, crosslinking reagents,
swelling temperature and agitation speed on particle size were investigated in detail. The morphologies and size distributions
of these micro-spheres were examined by SEM and particle size analysis (PSA). The T
g of the micro-spheres was measured by DSC. The results indicate that the particles (6.20 μm in diameter) exhibit excellent
mono dispersed property and high crosslinking degree when the concentration of the swelling reagent was 25%, the concentration
of the crosslinking reagents was 23%, the swelling temperature was 30°C and the stirring speed was 150 r/min.
__________
Translated from Chinese Journal of Applied Chemistry, 2007, 24(11): 1289–1294 相似文献