全文获取类型
收费全文 | 6202篇 |
免费 | 898篇 |
国内免费 | 902篇 |
专业分类
化学 | 4205篇 |
晶体学 | 60篇 |
力学 | 194篇 |
综合类 | 41篇 |
数学 | 588篇 |
物理学 | 1120篇 |
无线电 | 1794篇 |
出版年
2024年 | 12篇 |
2023年 | 50篇 |
2022年 | 119篇 |
2021年 | 140篇 |
2020年 | 165篇 |
2019年 | 205篇 |
2018年 | 146篇 |
2017年 | 144篇 |
2016年 | 268篇 |
2015年 | 311篇 |
2014年 | 348篇 |
2013年 | 429篇 |
2012年 | 485篇 |
2011年 | 468篇 |
2010年 | 396篇 |
2009年 | 457篇 |
2008年 | 471篇 |
2007年 | 390篇 |
2006年 | 386篇 |
2005年 | 348篇 |
2004年 | 324篇 |
2003年 | 345篇 |
2002年 | 447篇 |
2001年 | 350篇 |
2000年 | 196篇 |
1999年 | 126篇 |
1998年 | 77篇 |
1997年 | 69篇 |
1996年 | 52篇 |
1995年 | 39篇 |
1994年 | 31篇 |
1993年 | 25篇 |
1992年 | 22篇 |
1991年 | 23篇 |
1990年 | 21篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 6篇 |
1971年 | 4篇 |
排序方式: 共有8002条查询结果,搜索用时 15 毫秒
21.
22.
Dual-Mode Microstrip Open-Loop Resonators and Filters 总被引:1,自引:0,他引:1
A miniature dual-mode microstrip open-loop resonator is proposed. Distinct characteristics of this new type of dual-mode resonator are investigated using full-wave electromagnetic simulations. It is shown that the two operating modes, i.e., the even and odd modes, within a single dual-mode resonator of this type do not couple. It is also found that there is a finite-frequency transmission zero inherently associated with the even mode. Two two-pole filters using this type of dual-mode resonator are demonstrated with opposite asymmetric responses, which result from different locations of the transmission zero. Higher order filters of this type are also investigated. Both simulated and measured results are presented. 相似文献
23.
24.
25.
对Sn-C60薄膜进行紫外可见光吸收,X-射线衍射和扫描电镜的测定结果显示,薄膜样品紫外可见光吸收的两个短波段吸收峰比纯C60薄膜的吸收峰显著下降,说明Sn-C60薄膜的电子光吸收跃迁为间接跃迁,能带中有杂质能级的存在;样品的X射线衍射峰则对应于面心立方结构;扫描电镜结果显示薄膜为纳米级颗粒组成。 相似文献
26.
ChunXiaLI YingXiaLI LingBoYU HuaZHANG SiftDongCHU HuaShiGUAN 《中国化学快报》2003,14(8):776-778
A convenient synthetic route was developed for the synthesis of the novel glycolipids: 1,2-di-O-acyl-3-O-(2‘-acylamide-2‘-denxy-ct-D-glucopyranosyl)-sn-glycerols. 10 new compounds of glycolipids with different acyl groups were obtained. 相似文献
27.
ZHOU Ming-Xiua② YANG Chuna DENG Xiao-Yana YU Wei-Feib LI Jin-Shanb a 《结构化学》2006,25(6):647-652
1 INTRODUCTION Silicon and its alloy have been widely applied in such fields as electronic industry, high-temperature structural ceramics, etc. In addition, the researches on silicon and its relevant materials greatly promote the rapid development of modern optics and infor- mation technology. Therefore, more and more at- tention is focused on the structure of silicon, oxide of silicon and the interfaces between silicon and metal or nonmetal. As an ideal passive film on the Si surface, S… 相似文献
28.
Tsung-Nan Kuo Yo-Shen Lin Chi-Hsueh Wang Chun Hsiung Chen 《Microwave and Wireless Components Letters, IEEE》2006,16(2):90-92
In this letter, a compact branch-line coupler is proposed by making good use of the three-dimensional layout capability of the low-temperature co-fired ceramic (LTCC) substrate. This branch-line coupler is accomplished by using lumped-inductors and lumped-capacitors to realize the modified-T equivalent-circuit model for the transmission line so that the circuit size may drastically be reduced. Specifically, a very compact LTCC branch-line coupler with a size of 0.079/spl lambda//spl times/0.0717/spl lambda/ is implemented and carefully examined, where /spl lambda/ is the wavelength of the multilayer structure at the operating frequency f/sub 0/. 相似文献
29.
Munhyoung Cho Chong Hyun Lee Soohong Kim Joohwan Chun 《AEUE-International Journal of Electronics and Communications》2004,58(4):299-301
In this paper, we propose a new robust code division multiple access (CDMA) receiver of which weight vector is obtained by projecting the effective spatio-temporal signature waveform onto the signal subspace of the data covariance matrix. We verified our proposed algorithm by the field measured data obtained with a custom-built wideband CDMA test-bed. It will be shown that the proposed algorithm is robust to the signal mismatch. 相似文献
30.
The SmF_(2.01)was synthesized by reducing SmF_3 in H_2 stream.As it was doped inKM_gF_3 and KCaF_3.there was emission of Sm~(2+) in KMgF_3 but no emission of Sm~(2+) inKCaF_3 was observed. 相似文献