全文获取类型
收费全文 | 4788篇 |
免费 | 1460篇 |
国内免费 | 479篇 |
专业分类
化学 | 1758篇 |
晶体学 | 96篇 |
力学 | 332篇 |
综合类 | 98篇 |
数学 | 406篇 |
物理学 | 4037篇 |
出版年
2024年 | 8篇 |
2023年 | 46篇 |
2022年 | 135篇 |
2021年 | 127篇 |
2020年 | 181篇 |
2019年 | 109篇 |
2018年 | 143篇 |
2017年 | 206篇 |
2016年 | 213篇 |
2015年 | 202篇 |
2014年 | 307篇 |
2013年 | 422篇 |
2012年 | 384篇 |
2011年 | 366篇 |
2010年 | 339篇 |
2009年 | 331篇 |
2008年 | 330篇 |
2007年 | 353篇 |
2006年 | 321篇 |
2005年 | 289篇 |
2004年 | 271篇 |
2003年 | 213篇 |
2002年 | 226篇 |
2001年 | 195篇 |
2000年 | 176篇 |
1999年 | 116篇 |
1998年 | 120篇 |
1997年 | 87篇 |
1996年 | 71篇 |
1995年 | 67篇 |
1994年 | 55篇 |
1993年 | 54篇 |
1992年 | 38篇 |
1991年 | 35篇 |
1990年 | 28篇 |
1989年 | 15篇 |
1988年 | 32篇 |
1987年 | 16篇 |
1986年 | 14篇 |
1985年 | 18篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1974年 | 5篇 |
1973年 | 3篇 |
排序方式: 共有6727条查询结果,搜索用时 31 毫秒
731.
732.
733.
Effects of SiNx on two-dimensional electron gas and current collapse of A1GaN/GaN high electron mobility transistors
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
SiNx is commonly used as a passivation material for AlGaN/GaN high electron mobility transistors (HEMTs). In this paper, the effects of SiN x passivation film on both two-dimensional electron gas characteristics and current collapse of AlGaN/GaN HEMTs are investigated. The SiNx films are deposited by high- and low-frequency plasma-enhanced chemical vapour deposition, and they display different strains on the AlGaN/GaN heterostructure, which can explain the experiment results. 相似文献
734.
Photocurrent analysis of organic photovoltaic cells based on CuPc/C60 with Alq3 as a buffer layer
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The performance of an organic photovoltaic(OPV) cell based on copper phthalocyanine CuPc/C60 with a tris(8-hydroxyquinolinato) aluminum(Alq3) buffer layer has been investigated.It was found that the power conversion efficiency of the device was 1.51% under illumination with an intensity of 100 mW/cm2,which was limited by a squareroot dependence of the photocurrent on voltage.The photocurrent-optical power density characteristics showed that the OPV cell had a significant space-charge limited photocurrent with a varied saturation voltage and a three quarters power dependence on optical power density.Also,the absorption spectrum was measured by a spectrophotometer,and the results showed that the additional Alq3 layer has a minor effect on photocurrent generation. 相似文献
735.
736.
Izaskun Garrido Barry Lee Gunnar E. Fladmark Magne S. Espedal. 《Mathematics of Computation》2006,75(255):1403-1428
Parallel methods are usually not applied to the time domain because of the inherit sequentialness of time evolution. But for many evolutionary problems, computer simulation can benefit substantially from time parallelization methods. In this paper, we present several such algorithms that actually exploit the sequential nature of time evolution through a predictor-corrector procedure. This sequentialness ensures convergence of a parallel predictor-corrector scheme within a fixed number of iterations. The performance of these novel algorithms, which are derived from the classical alternating Schwarz method, are illustrated through several numerical examples using the reservoir simulator Athena.
737.
The effects of the linear birefringence inside a bulk glass current sensing element and the incident polarizing angle upon the performance of a bulk glass optical current sensor are derived and analyzed theoretically. The investigation results show that the linear birefringence will modify the scale factor of the system with a sample function; it can also affect the extent of the influence of the incident polarizing angle, at the same time. When the incident polarizing angle has some special values such as 0, 45, or 90, its effect on the system will be zero. These results might provide some useful reference to the researchers and designers of bulk glass optical current sensors. 相似文献
738.
Protein separations by a novel size-exclusion electrochromatography (SEEC) are presented. The present SEEC, denoted as pSEEC, was established with an oscillatory low-voltage electric field perpendicular to the mobile-phase streamline. Retention experiments with different proteins indicated that the influence of electric field strength on the partition coefficient is different for different proteins as well as for the same protein under different mobile-phase conditions. These results of protein retention led to the experimental design of protein separations with binary mixtures of BSA and immunoglobulin G (IgG), myoglobin (Myo) and lysozyme (Lys), as well as ovalbumin (Oval) and Myo. The separation results for the binary protein systems sufficiently exhibited the applicability of the pSEEC for various separations in terms of their molecular weights (MWs) as well as pIs. For example, it was possible to separate the gel-excluded proteins (BSA/IgG) as well as gel-permeable and similar-molecular-weight proteins (Myo/Lys) by the pSEEC. Moreover, in the cases of Oval/ Myo, which could be partially separated by size-exclusion chromatography, the use of the pSEEC greatly improved the resolution and the separation became possible at high sample loading. The results indicate that the pSEEC technology is promising for preparative protein separations. 相似文献
739.
Isolation and purification of canthaxanthin from the microalga Chlorella zofingiensis by high-speed counter-current chromatography 总被引:2,自引:0,他引:2
Certain microalgae are considered to be a potential source of canthaxanthin, which possesses strong antioxidant and anticancer activities. A high-speed counter-current chromatography (HSCCC) method was developed for the separation and purification of canthaxanthin from the microalga Chlorella zofingiensis. The crude canthaxanthin was obtained by extraction with organic solvents after the microalgal sample had been saponified. Preparative HSCCC, with a two-phase solvent system composed of n-hexane-ethanol-water (10:9:1 v/v), was successfully performed yielding canthaxanthin at 98.7% purity from 150 mg of the crude extract (2.1% canthaxanthin) in a one-step separation. The recovery of canthaxanthin was 92.3%. This was the first report that canthaxanthin was successfully separated and purified from microalgae. 相似文献
740.
The medicinal plant Atractylodes macrocephala (Baizhu in Chinese) has been widely used in traditional Chinese medicine for energy and stomach complaints, treatment of dyspepsia and anorexia, anti-inflammation, anticancer and for increasing assimilation. A high-speed counter-current chromatography (HSCCC) method was developed for the preparative separation and purification of two main bioactive components, namely, atractylon and atractylenolide III from A. macrocephala by using light petroleum (60-90 degrees C)-ethyl acetate-ethanol-water (4:1:4:1 v/v) as the two-phase solvent system in dual-mode elution. Compared with the separation using the normal-mode elution, the dual-mode HSCCC can be achieved with shorter elution time. Atractylenolide III (32.1 mg) at 99.0% purity and 319.6 mg atractylon at 97.8% purity could be obtained from 1000 mg crude sample in a single run. The recoveries of atractylenolide III and atractylon were 95.4 and 92.6%, respectively. 相似文献