全文获取类型
收费全文 | 4525篇 |
免费 | 544篇 |
国内免费 | 489篇 |
专业分类
化学 | 2298篇 |
晶体学 | 30篇 |
力学 | 225篇 |
综合类 | 45篇 |
数学 | 311篇 |
物理学 | 1155篇 |
综合类 | 1494篇 |
出版年
2024年 | 15篇 |
2023年 | 67篇 |
2022年 | 133篇 |
2021年 | 146篇 |
2020年 | 150篇 |
2019年 | 117篇 |
2018年 | 124篇 |
2017年 | 148篇 |
2016年 | 166篇 |
2015年 | 152篇 |
2014年 | 233篇 |
2013年 | 264篇 |
2012年 | 264篇 |
2011年 | 348篇 |
2010年 | 252篇 |
2009年 | 256篇 |
2008年 | 293篇 |
2007年 | 255篇 |
2006年 | 213篇 |
2005年 | 174篇 |
2004年 | 144篇 |
2003年 | 101篇 |
2002年 | 111篇 |
2001年 | 107篇 |
2000年 | 91篇 |
1999年 | 128篇 |
1998年 | 109篇 |
1997年 | 119篇 |
1996年 | 119篇 |
1995年 | 111篇 |
1994年 | 90篇 |
1993年 | 87篇 |
1992年 | 83篇 |
1991年 | 66篇 |
1990年 | 68篇 |
1989年 | 58篇 |
1988年 | 44篇 |
1987年 | 41篇 |
1986年 | 29篇 |
1985年 | 17篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1957年 | 4篇 |
排序方式: 共有5558条查询结果,搜索用时 15 毫秒
991.
By using the Al'tshuler-Aronov-Spivak (AAS) model, we give the amplitude changing with Rashba spin-orbit interaction (SOI) and Dresselhaus SOI strength. In the first idea 1D square loop (SL), Rashba SOI acts on two sides while Dresselhaus SOI acts on the other two sides. In the second SL, we consume Rashba SOI and Dresselhaus SOI act on four sides simultaneously. This model can be replaced by another one that Rashba SOI and Dresselhaus SOI act on every side independently, and each side is twice long. We theoretically illustrate the influence of the Dresselhaus SOI on node position and number. To explain the “half oscillation” phenomenon found in experiment, we apply Dresselhaus SOI to the ideal 1D SL. The conclusion is that the Dresselhaus SOI has a strong effect on the emergence of “half oscillation”. 相似文献
992.
Open-circuit voltage analysis of p-i-n type amorphous silicon solar cells deposited at low temperature 下载免费PDF全文
This paper identifies the contributions of p-a-SiC:H layers and i-a-Si:H layers to the open circuit voltage of p-i-n type a-Si:H solar cells deposited at a low temperature of 125 C.We find that poor quality p-a-SiC:H films under regular conditions lead to a restriction of open circuit voltage although the band gap of the i-layer varies widely.A significant improvement in open circuit voltage has been obtained by using high quality p-a-SiC:H films optimized at the "low-power regime" under low silane flow rates and high hydrogen dilution conditions. 相似文献
993.
Yan-Jun Li Peng Wang Jing-Fu Ni Liang Meng Xiao-Bo Wang Chun-Qi Sheng Hong-Nian Li Wen-Hua Zhang Yang Xu Fa-Qiang Xu Jun-Fa Zhu 《Journal of Electron Spectroscopy and Related Phenomena》2011,184(7):414-419
We have measured and analyzed the photoemission spectra (PES) of a C70 film in the photon energy region from 13.4 eV to 98.4 eV. The photoelectron intensities of two C 2p π-derived features (denoted by A and B) oscillate regularly in the whole energy region with some fine structures below ∼30 eV. To obtain the detailed information of the oscillations, we have developed a sophisticated but practical procedure for intensity calculation. The procedure consists of two core concepts. The first is ascribing the PES features to their corresponding molecular orbitals with the help of density functional calculations. The second is a background subtraction algorithm. With this procedure, we obtained the oscillating behavior for individual features (A and B), which is by and large consistent with the predictions based on the spherical symmetric approximation although C70 has the ellipsoidal shape. Owing to the solid state effect, the oscillating amplitudes of the A/B intensity ratios are smaller than those of gas phase C70, but an orbital shift reported recently was not observed on our sample. The oscillating curve of a deeper feature, which consists of both σ and π states, are also reported. 相似文献
994.
The generation of ultrasound in film–substrate system by a laser line source is studied in the case of ablation mechanism, which can be realized by adding a liquid layer at the excitation point. The time domain displacement can be yielded by the numerical jointed inversed Laplace–Fourier transformation technique. The typical surface acoustic waves (SAW) of two layer structures, slow film on fast substrate and fast film on slow substrate, are obtained and the effect of the propagation distance and the thickness of the film on the SAW are given. 相似文献
995.
996.
Ablation process of 1-kHz femtosecond lasers (pulse duration of 148 fs, wavelength of 775 nm) of Au film on silica substrates is studied. The thresholds for single and multi pulses can be obtained directly from the relation between the squared diameter D2 of the ablated craters and the laser fluence φo. From the plot of the accumulated laser fluence Nφth(N) and the number of laser pulses N, incubation coefficient of Au film is obtained to be 0.765. Some experimental data obtained around the single pulse threshold are in good agreement with the theoretical calculation. 相似文献
997.
Qin Han Zhichuan Niu Haiqiao Ni Shiyong Zhang Xiaohong Yang Yun Du Cunzhu Tong Huan Zhao Yingqiang Xu Hongling Peng Ronghan Wu 《中国光学快报(英文版)》2006,4(7)
Continuous wave operation of a semiconductor laser diode based on five stacks of InAs quantum dots (QDs) embedded within strained InGaAs quantum wells as an active region is demonstrated. At room temperature, 355-Mw output power at ground state of 1.33-1.35μm for a 20-μm ridge-waveguide laser without facet coating is achieved. By optimizing the molecular beam epitaxy (MBE) growth conditions,the QD density per layer is raised to 4 × 1010 cm-2. The laser keeps lasing at ground state until the temperature reaches 65 ℃. 相似文献
998.
B. Buliński K. Malinowski A. Michalik P. Niżegorodcew 《Isotopes in environmental and health studies》2013,49(7):261-265
The present paper makes an attempt of the interpretation of the tracer measurements by means of transfer function. Obtained data of residence time of catalyst in xylene isomerization column inserted in previous paper [1] were used to the identification of dynamic properties of individual sections of the column. 相似文献
999.