全文获取类型
收费全文 | 248623篇 |
免费 | 1584篇 |
国内免费 | 430篇 |
专业分类
化学 | 115275篇 |
晶体学 | 3835篇 |
力学 | 13047篇 |
综合类 | 3篇 |
数学 | 38151篇 |
物理学 | 80326篇 |
出版年
2021年 | 1066篇 |
2020年 | 1220篇 |
2019年 | 1299篇 |
2018年 | 10501篇 |
2017年 | 11364篇 |
2016年 | 6654篇 |
2015年 | 2483篇 |
2014年 | 2550篇 |
2013年 | 6330篇 |
2012年 | 9301篇 |
2011年 | 18647篇 |
2010年 | 11433篇 |
2009年 | 11507篇 |
2008年 | 16409篇 |
2007年 | 19848篇 |
2006年 | 5754篇 |
2005年 | 11940篇 |
2004年 | 8116篇 |
2003年 | 7705篇 |
2002年 | 5645篇 |
2001年 | 5803篇 |
2000年 | 4371篇 |
1999年 | 3169篇 |
1998年 | 2202篇 |
1997年 | 2257篇 |
1996年 | 2304篇 |
1995年 | 2074篇 |
1994年 | 2051篇 |
1993年 | 1854篇 |
1992年 | 2335篇 |
1991年 | 2416篇 |
1990年 | 2250篇 |
1989年 | 2214篇 |
1988年 | 2200篇 |
1987年 | 2204篇 |
1986年 | 2023篇 |
1985年 | 2513篇 |
1984年 | 2546篇 |
1983年 | 2013篇 |
1982年 | 2039篇 |
1981年 | 1868篇 |
1980年 | 1856篇 |
1979年 | 2170篇 |
1978年 | 2251篇 |
1977年 | 2105篇 |
1976年 | 2066篇 |
1975年 | 1936篇 |
1974年 | 1922篇 |
1973年 | 1998篇 |
1972年 | 1278篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The European Physical Journal Special Topics - The removal of suspended particles from the interior of a thermocapillary liquid bridge via a finite-particle-size effect restricting the particle... 相似文献
2.
3.
Nano palladium supported on high‐surface‐area metal–organic framework MIL‐101: an efficient catalyst for Sonogashira coupling of aryl and heteroaryl bromides with alkynes 下载免费PDF全文
Manne Annapurna T. Parsharamulu P. Vishnuvardhan Reddy M. Suresh Pravin R. Likhar Mannepalli Lakshmi Kantam 《应用有机金属化学》2015,29(4):234-239
Palladium nanoparticle‐incorporated metal–organic framework MIL‐101 (Pd/MIL‐101) was successfully synthesized and characterized using X‐ray diffraction, nitrogen physisorption, X‐ray photoelectron, UV–visible and infrared spectroscopies, and transmission electron microscopy. The characterization techniques confirmed high porosity and high surface area of MIL‐101 and high stability of nano‐size palladium particles. Pd/MIL‐101 nanocomposite was investigated for the Sonogashira cross‐coupling reaction of aryl and heteroaryl bromides with various alkynes under copper‐free conditions. The reusability of the catalyst was tested for up to four cycles without any significant loss in catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
4.
We study the full counting statistics of transport electrons through a semiconductor two-level quantum dot with Rashba spin–orbit (SO) coupling, which acts as a nonabelian gauge field and thus induces the electron transition between two levels along with the spin flip. By means of the quantum master equation approach, shot noise and skewness are obtained at finite temperature with two-body Coulomb interaction. We particularly demonstrate the crucial effect of SO coupling on the super-Poissonian fluctuation of transport electrons, in terms of which the SO coupling can be probed by the zero-frequency cumulants. While the charge currents are not sensitive to the SO coupling. 相似文献
5.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant. 相似文献
6.
7.
V. A. Bespalov V. M. Glazov E. A. Il’ichev Yu. A. Klimov S. V. Kuklev A. E. Kuleshov R. M. Nabiev G. N. Petrukhin B. G. Potapov G. S. Rychkov D. S. Sokolov V. V. Fandeev E. A. Fetisov S. S. Yakushov 《Technical Physics》2015,60(4):553-560
The results of investigation of optical image detectors designed for the largest problem, near-VUV, range of the spectrum are presented. The possibility of using a dual-stage image detection system to appreciably lower the sensitivity threshold and make computer data processing feasible is considered. The integration of a UV module into a wideband image detector is studied. 相似文献
8.
9.
10.
A. Lashgari S. Ghammamy R. Ramirez-Tagle G. Salgado-Moran 《Journal of Structural Chemistry》2015,56(8):1505-1513
Two new compounds of fluorine: (C2H5)4N[I2F] and (C2H5)4N[Br2F], have been easily synthesized in a nearly quantitative by a direct reaction of (C2H5)4NF, I2 and Br2. The products were isolated and characterized by elemental analysis and spectroscopic methods such as: Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-Vis). These compounds have been studied computationally with the Scalar ZORA relativistic level of theory using the ADF program package. The molecular parameters, and vibrational spectra were calculated. The excitation energies were found by timedependent perturbation density functional theory (TD-DFT). Molecule optimization, frequencies and excitation energies were calculated with standard Slatertype-orbital (STO) basis sets with triple-zeta quality double plus polarization functions (TZ2P) for all atoms. The FTIR, UV-Vis spectra and assignment of principal transitions and total density of state (TDOS) were extracted using the GaussSum 2.2 program. The comparison between experimental and calculated values showes that the experimental results correlate well with the predicted data. 相似文献