全文获取类型
收费全文 | 11966篇 |
免费 | 1942篇 |
国内免费 | 1569篇 |
专业分类
化学 | 9266篇 |
晶体学 | 132篇 |
力学 | 626篇 |
综合类 | 106篇 |
数学 | 1308篇 |
物理学 | 4039篇 |
出版年
2024年 | 37篇 |
2023年 | 256篇 |
2022年 | 493篇 |
2021年 | 502篇 |
2020年 | 522篇 |
2019年 | 555篇 |
2018年 | 442篇 |
2017年 | 394篇 |
2016年 | 600篇 |
2015年 | 611篇 |
2014年 | 700篇 |
2013年 | 857篇 |
2012年 | 1051篇 |
2011年 | 1049篇 |
2010年 | 648篇 |
2009年 | 657篇 |
2008年 | 739篇 |
2007年 | 623篇 |
2006年 | 589篇 |
2005年 | 517篇 |
2004年 | 442篇 |
2003年 | 394篇 |
2002年 | 451篇 |
2001年 | 368篇 |
2000年 | 257篇 |
1999年 | 263篇 |
1998年 | 228篇 |
1997年 | 164篇 |
1996年 | 173篇 |
1995年 | 141篇 |
1994年 | 118篇 |
1993年 | 84篇 |
1992年 | 114篇 |
1991年 | 81篇 |
1990年 | 73篇 |
1989年 | 46篇 |
1988年 | 42篇 |
1987年 | 43篇 |
1986年 | 36篇 |
1985年 | 22篇 |
1984年 | 23篇 |
1983年 | 15篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 3篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1957年 | 3篇 |
1936年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
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
2.
Analysis and pharmacokinetic study of polyphyllin H in beagle dog plasma after oral administration of Rhizoma Paridis Extracts by LC‐MS/MS 下载免费PDF全文
3.
4.
Double Michael additions of lithium enolaie of 1,4-dioxaspiro[4.5]dec-6-en-8-one to four acrylates afforded bicyclo[2.2.2]octan-2-ones with high regio- and stereoselectivities in moderate yields. 相似文献
5.
Fiber-optic reflex sensor for in-line production measurement 总被引:1,自引:0,他引:1
The paper describes experiments concerning distance measurement with fiber-optic sensor and improvement of the measurement principle. The sensor probe was well-designed with a small structure and multi-function. The novel optical fiber probe arrangement as well as the possibilities of use for complex measurement problems are explained using the measurement of an internal screw thread as an example. The experimental results show that the measurement uncertainty of the thread minor diameter can reach ±10 μm, and the stability of the measurement system is better than 0.07%. 相似文献
6.
7.
Wang Qing-Lun Zhao Bin Liao Dai-Zheng Yan Shi-Ping Cheng Peng Jiang Zong-Hui 《Transition Metal Chemistry》2003,28(3):326-330
The copper(II) complex Na2[Cu(pba)] · 6H2O has been synthesized and its structure determined. It consists of a novel two-dimensional network of [Cu(pba)]2– anions connected to each other through the sodium ion as a bridge. Spectroscopic and magnetic properties have been measured and a spin distribution calculation has been carried out with the GAUSSIAN-94. Theoretical calculations indicate the rather larger spin density on nitrogen atoms should be responsible for the satellite lines appearing beside the main hyperfine coupling signs of copper(II). The antiferromagnetic interaction may be due to the intermolecular interaction and/or different copper(II) ions through the Na+ bridge in the same layer. 相似文献
8.
Liang Liao Yi Pang Liming Ding Frank E. Karasz 《Journal of polymer science. Part A, Polymer chemistry》2003,41(20):3149-3158
A soluble cyano‐substituted poly[(1,3‐phenylene vinylene)‐alt‐(1,4‐phenylene vinylene)] derivative ( 9 ) was synthesized and characterized. Comparison between 9 and its model compound ( 10 ) showed that the chromophore in 9 remained to be well defined as a result of a π‐conjugation interruption at adjacent m‐phenylene units. The attachment of a cyano substituent only at the β position of the vinylene allowed the maximum electronic impact of the cyano group on the optical properties of the poly(p‐phenylene vinylene) material. At a low temperature (?108 or ?198 °C), the vibronic structures of 9 and 10 were partially resolved. The absorption and emission spectra of a film of 9 were less temperature‐dependent than those of a film of 10 , indicating that the former had a lower tendency to aggregate. A light‐emitting diode (LED) based on 9 emitted yellow light (λmax ≈ 578 nm) with an external quantum efficiency of 0.03%. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3149–3158, 2003 相似文献
9.
讨论了浅海中波导的声波散射问题,我们将该问题归结为一个第一类边界积分方程,利用正同化方法求解,并证明了该方法的收敛性,数值例子表明了该方法的简单与有效性。 相似文献
10.
A convergent-barrel (CB) cold spray nozzle was designed through numerical simulation. It was found that the main factors influencing significantly particle velocity and temperature include the length and diameter of the barrel section, the nature of the accelerating gas and its pressure and temperature, and the particle size. Particles can achieve a relatively low velocity but a high temperature under the same gas pressure using a CB nozzle compared to a convergent-divergent (CD) nozzle. The experiment results with Cu powder using the designed CB nozzle confirmed that particle deposition can be realized under a lower gas pressure with a CB nozzle. 相似文献