全文获取类型
收费全文 | 24049篇 |
免费 | 2958篇 |
国内免费 | 1913篇 |
专业分类
化学 | 17549篇 |
晶体学 | 276篇 |
力学 | 1042篇 |
综合类 | 97篇 |
数学 | 2180篇 |
物理学 | 7776篇 |
出版年
2024年 | 32篇 |
2023年 | 314篇 |
2022年 | 498篇 |
2021年 | 720篇 |
2020年 | 808篇 |
2019年 | 800篇 |
2018年 | 714篇 |
2017年 | 602篇 |
2016年 | 1019篇 |
2015年 | 958篇 |
2014年 | 1182篇 |
2013年 | 1747篇 |
2012年 | 2078篇 |
2011年 | 2145篇 |
2010年 | 1390篇 |
2009年 | 1317篇 |
2008年 | 1660篇 |
2007年 | 1510篇 |
2006年 | 1367篇 |
2005年 | 1233篇 |
2004年 | 1007篇 |
2003年 | 836篇 |
2002年 | 890篇 |
2001年 | 608篇 |
2000年 | 466篇 |
1999年 | 432篇 |
1998年 | 317篇 |
1997年 | 297篇 |
1996年 | 296篇 |
1995年 | 243篇 |
1994年 | 213篇 |
1993年 | 167篇 |
1992年 | 167篇 |
1991年 | 148篇 |
1990年 | 120篇 |
1989年 | 90篇 |
1988年 | 65篇 |
1987年 | 42篇 |
1986年 | 44篇 |
1985年 | 60篇 |
1984年 | 38篇 |
1983年 | 33篇 |
1982年 | 32篇 |
1981年 | 33篇 |
1980年 | 22篇 |
1979年 | 15篇 |
1978年 | 18篇 |
1976年 | 17篇 |
1975年 | 16篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
DongXiangLI WanGuoHOU ShuPingLI MingTuHAO GaoYongZHANG 《中国化学快报》2004,15(2):224-227
The relation of the isoelectric point (IEP) and the point of zero net charge (PZNC) of the hydrotalcite-like compounds was discussed. It was found that the IEP does not equal to the PZNC and the IEP is higher than the PZNC. The structural positive charges existing in the HTlc,which cause the difference between the IEP and the PZNC. The effects of the structural positive charges of the HTlc on its IEP and PZNC are the same as the specific adsorption of metal cations. 相似文献
62.
In this article we prove the existence of the solution to the mixed problem for Euler–Bernoulli beam equation with memory term. The existence is proved by means of the Faedo–Galerkin method and the exponential decay is obtained by making use of the multiplier technique combined with integral inequalities due to Komornik. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
63.
非负矩阵与有向图的谱半径 总被引:2,自引:0,他引:2
本文给出非负矩阵的谱半径的上界、下界,由此给出有向图的谱半径的界. 相似文献
64.
Yu. A. Mitropol’skii Nguyen Dong Anh Nguyen Dyk Tynh 《Ukrainian Mathematical Journal》1998,50(11):1731-1737
We construct the second approximation for random oscillations described by the Van der Pol equation which are under the action
of a broadband random process.
Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 50, No. 11, pp. 1517–1521, November, 1998. 相似文献
65.
Modifying complex plane rotations, we derive a new Jacobi-type algorithm for the Hermitian eigendecomposition, which uses only real arithmetic. When the fast-scaled rotations are incorporated, the new algorithm brings a substantial reduction in computational costs. The new method has the same convergence properties and parallelism as the symmetric Jacobi algorithm. Computational test results show that it produces accurate eigenvalues and eigenvectors and achieves great reduction in computational time.The work of this author was supported in part by the National Science Foundation grant CCR-8813493 and by the University of Minnesota Army High Performance Computing Research Center contract DAAL 03-89-C-0038.The work of this author was supported in part by the University of Minnesota Army High Performance Computing Research Center contract DAAL 03-89-C-0038. 相似文献
66.
67.
Dielectric effect on the rf characteristics of a helical groove travelling wave tube 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A new type of partial-dielectric-loaded helical groove slow-wave structure (SWS) for millimetre wave travelling wave tube (TWT) is presented in this paper.The radio-frequency characteristics including the dispersion properties,the longitudinal electric field distribution and the beam-wave coupling impedance of this structure are analysed.The results show that the dispersion of the helical groove circuit is weakened,the phase velocity is reduced and the position of the maximum Ez is moved from the mouth to the inside of the groove after partially filling the dielectric materials in the helical groove SWS.Therefore,the dielectric-loaded helical groove SWS is suitable for a multi-beam TWT with broad band and high gain. 相似文献
68.
69.
70.
J.H. Sung J.Y. Park T. Imran Y.S. Lee C.H. Nam 《Applied physics. B, Lasers and optics》2006,82(1):5-8
Optical pulses with 1.1-mJ energy and 5.5-fs duration have been generated at 1-kHz repetition rate from a chirped pulse amplification
Ti:Sapphire laser incorporating a differentially pumped hollow-fiber chirped-mirror compressor. The effects of self-focusing
and multi-photon ionization during the beam propagation were minimized by differentially pumping the hollow fiber filled with
neon. The spectral broadening at the hollow-fiber compressor was optimized by adjusting gas pressure, laser intensity, and
laser chirp, covering from 540 nm to 950 nm.
PACS 42.65.Jx; 42.65.Re 相似文献