全文获取类型
收费全文 | 26126篇 |
免费 | 4190篇 |
国内免费 | 2486篇 |
专业分类
化学 | 18384篇 |
晶体学 | 312篇 |
力学 | 1541篇 |
综合类 | 118篇 |
数学 | 3003篇 |
物理学 | 9444篇 |
出版年
2024年 | 70篇 |
2023年 | 529篇 |
2022年 | 956篇 |
2021年 | 916篇 |
2020年 | 1026篇 |
2019年 | 1005篇 |
2018年 | 837篇 |
2017年 | 739篇 |
2016年 | 1227篇 |
2015年 | 1174篇 |
2014年 | 1365篇 |
2013年 | 1823篇 |
2012年 | 2444篇 |
2011年 | 2442篇 |
2010年 | 1607篇 |
2009年 | 1537篇 |
2008年 | 1690篇 |
2007年 | 1550篇 |
2006年 | 1384篇 |
2005年 | 1196篇 |
2004年 | 875篇 |
2003年 | 672篇 |
2002年 | 661篇 |
2001年 | 496篇 |
2000年 | 454篇 |
1999年 | 532篇 |
1998年 | 435篇 |
1997年 | 442篇 |
1996年 | 455篇 |
1995年 | 364篇 |
1994年 | 310篇 |
1993年 | 236篇 |
1992年 | 236篇 |
1991年 | 198篇 |
1990年 | 170篇 |
1989年 | 144篇 |
1988年 | 99篇 |
1987年 | 109篇 |
1986年 | 87篇 |
1985年 | 83篇 |
1984年 | 49篇 |
1983年 | 44篇 |
1982年 | 35篇 |
1981年 | 19篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1976年 | 9篇 |
1975年 | 11篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The compression behaviour of Ni77P23 amorphous alloy is investigated at room temperature in a diamond-anvil cell instrument using in-situ high pressure energy dispersive x-ray diffraction with a synchrotron radiation source. The equation of state is determined by fitting the experimental data according to the Birch-Murnaghan equation. It is found that the structure of Ni77P23 amorphous alloy is stable under pressures up to 30.5 GPa. Within the pressure range from zero to the experimental one, the pressure-induced structural relaxation is reversible. 相似文献
62.
63.
含三正辛胺微胶囊对六价铬的富集 总被引:5,自引:0,他引:5
本文将对六价铬有效的萃取剂TOA(三正辛胺)微胶囊化,制成填充柱型的酸性体系六价铬的富集分离装置。实验结果表明,微胶囊填充柱中每毫升TOA对六价铬的最大萃取容量为158.0g/mL,为纯TOA液相萃取的4.9倍。微胶囊经碱/水洗涤后,可再生使用。 相似文献
64.
65.
66.
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
67.
68.
The Existence of Solutions to Sturm-Liouville Boundary Value Problems with Laplacian-like Operator 总被引:2,自引:0,他引:2
Wei-ping Sun Wei-gao GeDepartment of Applied Mathematics Beijing Institute of Technology Beijing China 《应用数学学报(英文版)》2002,18(2):341-348
Abstract The existence of infinitely many solutions to Sturm-Liouville boundary value problem with aLaplacian-like operator is studied by applying generalized polar coordinates. 相似文献
69.
To incorporate an acceptor type polythiophene segment onto a supramolecular block copolymer for potential light harvesting applications, effective synthetic routes for the end‐functionalized and acceptor‐substituted polythiophenes are critical. The Ullmann coupling reaction can be utilized to obtain electron‐deficient polythiophenes and to attach terminal thiophene units that carry functional groups. In this article, the reactions involving a 2,5‐dibromothiophene monomer containing an electron‐withdrawing fluorinated ester and 5‐bromo‐2‐thiophenecarboxaldehyde (the end‐capper) were studied in detail. It was found that the Ullmann coupling reaction of the dibromide is very fast (completed in a few minutes) and the terminal bromine group does not survive long under the reaction condition. These findings lead to the development of an effective procedure for aldehyde end‐capping of electron‐deficient polythiophenes. Polymers with molecular weights around 4000 Da are routinely obtained. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 41–47, 2007 相似文献
70.